This document describes a VSC-HVDC transmission system connecting a strong AC system to a weak island AC system. It investigates the AC filter requirements and designs controllers for the VSC using optimal techniques. The controllers designed are a active power controller for the rectifier, reactive power controller for the rectifier, DC voltage controller for the inverter, and AC voltage controller for the inverter. Simulations are performed in MATLAB to analyze the system's performance for load variations in the island system.
Transient stability in power system is vital to be addressed due to large disturbances that could damage the system such as load changes and voltage increases. This paper presents a multi-machine transient stability using the Static Synchronous Series Compensator (SSSC). SSSC is a device that is connected in series with the power transmission line and produces controllable voltage which contribute to a better performance in the power system stability. As a result, this research has observed a comparison of the synchronization of a three-phase system during single-phase faults before and after installing the SSSC device. In addition, this research investigates the ability of three different types of controllers i.e. Proportional Integral (PI), Proportional Integral Derivation (PID), and Generic controllers to be added to the SSSC improve the transient stability as it cannot operate by itself. This is because the improvement is too small and not able to achieve the desired output. The task presented is to improve the synchronization of the system and time taken for the voltage to stabilize due to the fault. The simulation result shows that the SSSC with an additional controller can improve the stability of a multi-machine power system in a single phase fault.
Seamless Transitions between Grid-Connected and Stand-Alone Operations of Dis...IJERD Editor
Control of the Distributed Generation (DG) system is important in both grid-connected and standalone
modes and the system stability becomes very crucial during the transfer between these two modes. If the
system does not have a proper transfer procedure, severe transient voltages or currents will occur, which may
damage the entire system. A seamless transfer can ensure smooth operation and quick attainment of steady state.
In order to solve these transition problems, this paper presents the development and test of a control strategy for
DG capable of working in grid-connected and intentional islanding connection modes with seamless transitions
from both operational modes.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
LOW VOLTAGE RIDE - THROUGH CAPABILITY OF WIND FARMSEditor IJMTER
Nowadays wind turbines are generally required to offer ancillary services similar to those
provided by conventional generators. One of the most important services wind turbines must offer is
to stay connected to the grid in fault situations delivering the reactive current specified in the recent
grid codes. In this paper, FACTS solutions for fixed speed wind farms such as DVR (Dynamic
Voltage Restorer) are presented as well as classic control and crowbar solutions for variable speed
wind turbines.
This paper investigates the performance of line commutated converter (LCC) based monopolar
HVDC transmission system feeding a weak AC network with hybrid reactive power compensators (RPC’s) at the
inverter AC side. The hybrid compensator is an equal mix of any two of the following compensators:
synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM).
The HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal
proportional integral (PI) controller for rectifier and inverter control. The transient performances of hybrid
RPC’s (SC+SVC, SVC+STATCOM and SC+STATCOM) are judged under various fault conditions and the
outcomes are compared with the performance of the SC, SVC and STATCOM to highlight the supremacy of the
hybrid compensators. The simulation results validate that the equal mix of SC and STATCOM has a steady and
fastest response. The results also demonstrate the superiority of the firefly algorithm based optimal PI
controller over the conventional PI controller. The harmonic analysis is also carried out under steady state
operation to assure the quality of power supply on the inverter AC side
This document discusses a proposed tool using support vector regression (SVR) and fuzzy logic controller (FLC) for online voltage stability monitoring and estimation of reactive power (VAR) support in deregulated power systems. The tool uses bus voltage angle and reactive power load as inputs to SVR to predict the voltage stability margin index (VSMI) and voltage stability factor (VSF) of the most critical bus. The results of SVR are compared to artificial neural networks in terms of accuracy and computation time on IEEE 14 bus and 30 bus test systems. The tool estimates voltage stability margins for different transactions and contingencies and determines the minimum VAR support needed to enhance stability.
LOAD FREQUENCY CONTROL IN TWO AREA NETWORK INCLUDING DGIAEME Publication
Automatic Generation Control (AGC) is associate integral a part of Energy Management
System. This paper deals with the automatic generation control of interconnected multi area grid
network. The first purpose of the AGC is to balance the full system generation against system load
and losses so the specified frequency and power interchange with neighboring systems are
maintained. Any pair between generation and demand causes the system frequency to deviate from
regular worth. So high frequency deviation could result in system collapse. This necessitates
associate correct and quick acting controller to take care of constant nominal frequency. The
limitations of the conventional controls are slow and lack of efficiency in handling system nonlinearity.
This leads to develop a control technique for AGC. In this paper both conventional and
PI viz. Proportional Integral controller approach of automatic generation control has been
examined. PI based AGC has been used for all optimization purposes. System performance has
been evaluated at various disturbances such as, load disturbances, grid disturbances and both load
and grid disturbances. Various responses due to conventional and proposed PI based AGC
controllers have been compared at load disturbances, grid disturbances and both load and grid
disturbances.
ER Publication,
IJETR, IJMCTR,
Journals,
International Journals,
High Impact Journals,
Monthly Journal,
Good quality Journals,
Research,
Research Papers,
Research Article,
Free Journals, Open access Journals,
erpublication.org,
Engineering Journal,
Science Journals,
Transient stability in power system is vital to be addressed due to large disturbances that could damage the system such as load changes and voltage increases. This paper presents a multi-machine transient stability using the Static Synchronous Series Compensator (SSSC). SSSC is a device that is connected in series with the power transmission line and produces controllable voltage which contribute to a better performance in the power system stability. As a result, this research has observed a comparison of the synchronization of a three-phase system during single-phase faults before and after installing the SSSC device. In addition, this research investigates the ability of three different types of controllers i.e. Proportional Integral (PI), Proportional Integral Derivation (PID), and Generic controllers to be added to the SSSC improve the transient stability as it cannot operate by itself. This is because the improvement is too small and not able to achieve the desired output. The task presented is to improve the synchronization of the system and time taken for the voltage to stabilize due to the fault. The simulation result shows that the SSSC with an additional controller can improve the stability of a multi-machine power system in a single phase fault.
Seamless Transitions between Grid-Connected and Stand-Alone Operations of Dis...IJERD Editor
Control of the Distributed Generation (DG) system is important in both grid-connected and standalone
modes and the system stability becomes very crucial during the transfer between these two modes. If the
system does not have a proper transfer procedure, severe transient voltages or currents will occur, which may
damage the entire system. A seamless transfer can ensure smooth operation and quick attainment of steady state.
In order to solve these transition problems, this paper presents the development and test of a control strategy for
DG capable of working in grid-connected and intentional islanding connection modes with seamless transitions
from both operational modes.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
LOW VOLTAGE RIDE - THROUGH CAPABILITY OF WIND FARMSEditor IJMTER
Nowadays wind turbines are generally required to offer ancillary services similar to those
provided by conventional generators. One of the most important services wind turbines must offer is
to stay connected to the grid in fault situations delivering the reactive current specified in the recent
grid codes. In this paper, FACTS solutions for fixed speed wind farms such as DVR (Dynamic
Voltage Restorer) are presented as well as classic control and crowbar solutions for variable speed
wind turbines.
This paper investigates the performance of line commutated converter (LCC) based monopolar
HVDC transmission system feeding a weak AC network with hybrid reactive power compensators (RPC’s) at the
inverter AC side. The hybrid compensator is an equal mix of any two of the following compensators:
synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM).
The HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal
proportional integral (PI) controller for rectifier and inverter control. The transient performances of hybrid
RPC’s (SC+SVC, SVC+STATCOM and SC+STATCOM) are judged under various fault conditions and the
outcomes are compared with the performance of the SC, SVC and STATCOM to highlight the supremacy of the
hybrid compensators. The simulation results validate that the equal mix of SC and STATCOM has a steady and
fastest response. The results also demonstrate the superiority of the firefly algorithm based optimal PI
controller over the conventional PI controller. The harmonic analysis is also carried out under steady state
operation to assure the quality of power supply on the inverter AC side
This document discusses a proposed tool using support vector regression (SVR) and fuzzy logic controller (FLC) for online voltage stability monitoring and estimation of reactive power (VAR) support in deregulated power systems. The tool uses bus voltage angle and reactive power load as inputs to SVR to predict the voltage stability margin index (VSMI) and voltage stability factor (VSF) of the most critical bus. The results of SVR are compared to artificial neural networks in terms of accuracy and computation time on IEEE 14 bus and 30 bus test systems. The tool estimates voltage stability margins for different transactions and contingencies and determines the minimum VAR support needed to enhance stability.
LOAD FREQUENCY CONTROL IN TWO AREA NETWORK INCLUDING DGIAEME Publication
Automatic Generation Control (AGC) is associate integral a part of Energy Management
System. This paper deals with the automatic generation control of interconnected multi area grid
network. The first purpose of the AGC is to balance the full system generation against system load
and losses so the specified frequency and power interchange with neighboring systems are
maintained. Any pair between generation and demand causes the system frequency to deviate from
regular worth. So high frequency deviation could result in system collapse. This necessitates
associate correct and quick acting controller to take care of constant nominal frequency. The
limitations of the conventional controls are slow and lack of efficiency in handling system nonlinearity.
This leads to develop a control technique for AGC. In this paper both conventional and
PI viz. Proportional Integral controller approach of automatic generation control has been
examined. PI based AGC has been used for all optimization purposes. System performance has
been evaluated at various disturbances such as, load disturbances, grid disturbances and both load
and grid disturbances. Various responses due to conventional and proposed PI based AGC
controllers have been compared at load disturbances, grid disturbances and both load and grid
disturbances.
ER Publication,
IJETR, IJMCTR,
Journals,
International Journals,
High Impact Journals,
Monthly Journal,
Good quality Journals,
Research,
Research Papers,
Research Article,
Free Journals, Open access Journals,
erpublication.org,
Engineering Journal,
Science Journals,
This document proposes an artificial neural network and fuzzy logic controller tool for online voltage stability monitoring and estimating reactive power (VAR) support needs in deregulated power systems. The tool uses bus voltage angles and reactive power loads as inputs to the ANN, which then outputs the voltage stability margin and voltage stability factor of the most vulnerable bus. The ANN is trained offline using patterns from continuation power flow simulations. The tool can estimate stability margins and determine minimum VAR support for different system conditions and contingencies in deregulated markets. It has been tested on IEEE 14 bus and 30 bus systems.
Voltage Stability Based Formation of Voltage Control Areas Considering Impact...IJAPEJOURNAL
Voltage instability has been considered as a major threat to power system networks since last three decades. Frequent incidences of grid failures caused by voltage instability have been observed in different parts of the world. Fast voltage stability assessment of power system may be done by formation of voltage control areas, clubbing group of buses in geographically compact region having similar voltage instability problem. This paper presents a new approach for formation of voltage control areas (VCAs) based on sensitivity of reactive power generations with respect to reactive power demands, together with bus voltage variations under voltage stability based critical contingencies. The load buses in geographically compact region showing similar sensitivity of reactive power demand to reactive generations have been clubbed together to form voltage control areas. Since, voltage control areas formed should remain valid under change in operating conditions and network topology, the areas formed based on reactive power sensitivities
have been modified considering voltage variations at different loadings points under voltage stability based critical contingencies. Voltage stability based Critical contingencies have been selected based on maximum loadability criterion. Case studies have been performed on IEEE 14-bus system. Simulation results performed on IEEE 14-bus system validate VCAs formed even under change in network topology caused by line outages and change in operating conditions caused by variations in real and reactive power demands. The VCAs formed by proposed method have been compared with VCAs formed by few existing approaches. The superiority of proposed approach of voltage control areas formation over few existing approaches has been established on the test system considered.
Implementation of DC voltage controllers on enhancing the stability of multi-...IJECEIAES
Because of the increasing penetration of intermittent green energy resources like offshore wind farms, solar photovoltaic, the multi-terminal DC grid using VSC technology is considered a promising solution for interconnecting these future energies. To improve the stability of the multi-terminal direct current (MTDC) network, DC voltage control strategies based on voltage margin and voltage droop technique have been developed and investigated in this article. These two control strategies are implemented in the proposed model, a ±400 kV meshed multi-terminal MTDC network based on VSC technology with four terminals during the outage converter. The simulation results include the comparison and analysis of both techniques under the outage converter equipped with constant DC voltage control, then the outage converter equipped with constant active power control. The simulation results confirm that the DC voltage droop technique has a better dynamic performance of power sharing and DC voltage regulation.
This document presents a new control scheme for a STATCOM (Static Synchronous Compensator) to improve power quality in a grid-connected wind energy system. A STATCOM equipped with a battery energy storage system is connected at the point of common coupling between the wind farm and the grid. The STATCOM control scheme uses a hysteresis current control technique to inject compensating current and regulate the grid voltage. Simulation results show the STATCOM can mitigate reactive power demand and harmonics, as well as respond quickly to changes in load to help regulate voltage and current waveforms at the point of connection to the grid.
Transmission System Operators and Owners are required to maintain a Black Start and System
Restoration Plan that has been thoroughly verified with studies. Combustion turbines are
typically used as Black Start generators, which then are used to start larger coal and combined
cycle plants. Steady state and transient studies are normally performed to verify whether voltage
and frequency are within limits so as not to interrupt the restoration process, and to ensure
large induction motors associated with the power plants can be started. In recent times, Battery
Energy Storage Systems (BESS) are being considered for black start system restoration, in
lieu of combustion turbines. The models that are currently available for BESS in transmission
planning software are meant to study synchronized operation of BESS, rather than an islanded
operation. In this paper, a modeling technique is presented for evaluating BESS for black start
system restoration. The performance of BESS for black start system restoration is compared
with the performance of a combustion turbine.
This document discusses testing procedures for motor bus bar transfer schemes. It focuses on verification of an in-phase transfer method. The paper provides background on voltage decay theory during motor bus bar transfers and discusses an example recording of actual voltage decay on a motor bus bar system. It also briefly describes other transfer methods before detailing a proposed testing protocol to evaluate the in-phase transfer method, including using calculations and simulations to determine the estimated time of phase coincidence during a transfer.
This document discusses constraints and load flow analysis in power systems. It outlines four key constraints: active power constraint, reactive power constraint, voltage magnitude constraint, and load angle constraint. It also describes load flow analysis as a balanced mechanism between demand and generation under incremental loading. Load flow analysis is important for the safe and future operation of power systems. The document further discusses bus classification, basic power flow conditions including the proportional relationships between reactive power and voltage and active power and load angle. It also covers the development of the Y-bus matrix considering line resistances and inductances alone and then including line capacitances.
This article proposes a novel scheme to improve the doubly-fed induction generator (DFIG) behavior during grid fault. The DFIG’s are sensitives to voltage variations when abrupt variations of the wind velocity arrive. For enhancing DFIG behavior, protecting the converters, and smoothing the fluctuations power output of the DFIG under sag voltage; a novel hybrid energy storage system scheme and its controller are proposed. The main advantages of our approach are a faster response and suppressing overvoltage on DC bus and globally less stress in the storage system. The control structure decreases the tiredness on the battery and restores the DC bus voltage rapidly, globally the battery system operating time increases. The results obtained by simulations in MATLAB validate the benefits of the suggested control.
This document discusses several topics related to power system operation and control:
1. It defines a control area as a region where all generators swing together in response to load changes or speed governor settings.
2. It explains that voltage stability refers to a power system reaching a stable post-disturbance voltage equilibrium.
3. It describes different approaches for steady-state security analysis, which test the system against contingencies by calculating changes and checking against constraints.
Influencing Power Flow and Transient Stability by Static Synchronous Series C...ijeei-iaes
This document summarizes research on using a Static Synchronous Series Compensator (SSSC) to improve power flow and transient stability in a Single Machine Infinite Bus (SMIB) system. The research models an SMIB system and analyzes its power angle curve and transient stability both with and without an SSSC. Results show that the SSSC is effective at stabilizing the system after a transient fault by controlling voltage injection and virtual line impedance. The SSSC allows the system to regain stability faster than without the SSSC. Therefore, the SSSC is concluded to be an effective means of influencing power flow and improving transient stability in power systems.
In this paper a grid interconnected system with wind energy source linked with a FACTs based SSFC device ( Static switched filter compensator ) at load for enhancing power quality is considered .Analysis is done for the proposed system by varying Carrier frequency over a wide range and observed system performance at all 3 busses wise Grid bus, Generator Bus and Load Bus. Two regulators are used to organize the FACTS SSFC-device, these are based on a tri-loop dynamic error obsessed inter-coupled input to VSC controller. Investigation is made in MATLAB/SIMULINK Environment for the proposed system ,it is observed that system performance in terms of percentage Total harmonic Distortion is satisfactory along with the Enhanced Power Quality.
Static Synchronous Series Compensator (SSSC) with Superconducting Magnetic En...IDES Editor
Static Synchronous Series Compensator (SSSC) has
been designed with Superconducting Magnetic Energy Storage
(SMES) system. A closed loop control scheme has been
proposed with PI controller and real and reactive powers are
taken as references. A 48 pulse voltage source inverter is
designed for the SSSC. Control scheme for the chopper circuit
of SMES coil is also designed. A three area system is taken as
the test system and the operation of SSSC with SMES is
analysed for various transient disturbances. Test results under
different disturbances and operating conditions show the
proposed SSSC with SMES is effective in damping out the
power system oscillations.
Modeling Optimization Voltage Index Unified Power Flow Controller Equivalent ...IJMTST Journal
This paper presents an active-reactive power control strategy for voltage source converters (VSCs) based on derivation of the direct and quadrature components of the VSC output current. The proposed method utilizes a multivariable proportional-integral controller and provides almost completely decoupled control capability of the active and reactive power with almost full disturbance rejection due to step changes in the power exchanged between the VSC and the grid. It also imposes fast transient response and zero steady-state error as compared to the conventional power control approaches. The applicability of the proposed power control strategy for providing the robust stability of the system against the uncertainties of the load parameters is also investigated. The superiority of the proposed control strategy over conventional approaches in the new condition of supplying the load is demonstrated. The theoretical aspects of the proposed multivariable-based power control strategy and the conventional approaches are reviewed and simulation results are presented in two separate sections. MATLAB/Simulink 2009a is used to simulate different scenarios of the simulation.
Iaetsd load frequency control for a distributed gridIaetsd Iaetsd
This document discusses load frequency control for a distributed grid system involving wind, hydro, and thermal power plants. It proposes using a PI controller to suppress frequency deviations caused by load and generation fluctuations from renewable resources connected to the grid. It models a system with four thermal plants, a wind farm, and a hydro plant in MATLAB. Load frequency control methods are explored to minimize deviations in area frequency and tie-line power interchange for reliable grid operation with both conventional and renewable resources.
Simulation of D-STATCOM to study Voltage Stability in Distribution systemijsrd.com
This document presents a simulation study of a D-STATCOM (Distribution Static Compensator) to improve voltage stability in a distribution system. It first provides background on voltage dips and describes the structure of a STATCOM, which includes a voltage source inverter, transformer, and controller. The simulation model of the D-STATCOM and distribution network is developed using SimPowerSystems blocks. Simulation results show that without the D-STATCOM, voltage dips to 0.93 p.u. during a load change, but with the D-STATCOM the voltage is stabilized at 1.0 p.u., demonstrating its effectiveness in mitigating power quality issues like voltage instability.
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document presents the design and analysis of a microstrip patch antenna for triple band applications in digital communication systems. The antenna is designed to operate at 1.5 GHz, 2.4 GHz, and 5.5 GHz bands. It consists of a rectangular patch fed by a microstrip line with two additional arms of different lengths acting as resonators. Simulation results show the antenna achieves impedance matching across bandwidths of 700 MHz, 800 MHz, and 1 GHz at the three frequencies. It has an omnidirectional radiation pattern and gain between 5-6 dBi. The compact triple band design reduces the antenna size by 67% compared to a conventional patch antenna.
This document describes the design and implementation of a hybrid cryptosystem using the AES and SHA-2 algorithms. The system integrates AES, a symmetric encryption algorithm, with SHA-2, a cryptographic hash function, to improve data security. AES encrypts data using a 128-bit key generated by hashing the input message with SHA-2. The combined system was synthesized using Xilinx ISE software and implemented on a Virtex-5 FPGA, utilizing under 2% of slice registers and 5% of slice LUTs. This provides higher security than AES alone through increased algorithm complexity.
The document summarizes a 1-level discrete wavelet transform (DWT) image watermarking algorithm for embedding watermarks into RGB cover images. The algorithm applies 1-level DWT to decompose the RGB cover image and watermark into frequency subbands. It then inserts the watermark into the low-frequency approximation subband of the cover image using alpha blending. The watermarked image achieves good quality with high peak signal-to-noise ratio. The extracted watermark matches the original with a normalized correlation value close to 1, showing the algorithm efficiently detects the watermark. The algorithm is imperceptible and robust against various attacks like noise and filtering.
This document describes a proposed fuzzy logic-based weather advisory system. It begins with background on how agricultural productivity depends on weather and how weather forecasts can help farmers plan. It then discusses using a fuzzy approach to develop the system given the uncertain nature of weather. The rest of the document reviews related work applying fuzzy logic to weather-related problems and provides details on fuzzy logic and how it can model imprecise systems through membership functions and if-then rules. The overall goal is to develop a weather advisory system to help farmers minimize losses from adverse conditions.
This document proposes an artificial neural network and fuzzy logic controller tool for online voltage stability monitoring and estimating reactive power (VAR) support needs in deregulated power systems. The tool uses bus voltage angles and reactive power loads as inputs to the ANN, which then outputs the voltage stability margin and voltage stability factor of the most vulnerable bus. The ANN is trained offline using patterns from continuation power flow simulations. The tool can estimate stability margins and determine minimum VAR support for different system conditions and contingencies in deregulated markets. It has been tested on IEEE 14 bus and 30 bus systems.
Voltage Stability Based Formation of Voltage Control Areas Considering Impact...IJAPEJOURNAL
Voltage instability has been considered as a major threat to power system networks since last three decades. Frequent incidences of grid failures caused by voltage instability have been observed in different parts of the world. Fast voltage stability assessment of power system may be done by formation of voltage control areas, clubbing group of buses in geographically compact region having similar voltage instability problem. This paper presents a new approach for formation of voltage control areas (VCAs) based on sensitivity of reactive power generations with respect to reactive power demands, together with bus voltage variations under voltage stability based critical contingencies. The load buses in geographically compact region showing similar sensitivity of reactive power demand to reactive generations have been clubbed together to form voltage control areas. Since, voltage control areas formed should remain valid under change in operating conditions and network topology, the areas formed based on reactive power sensitivities
have been modified considering voltage variations at different loadings points under voltage stability based critical contingencies. Voltage stability based Critical contingencies have been selected based on maximum loadability criterion. Case studies have been performed on IEEE 14-bus system. Simulation results performed on IEEE 14-bus system validate VCAs formed even under change in network topology caused by line outages and change in operating conditions caused by variations in real and reactive power demands. The VCAs formed by proposed method have been compared with VCAs formed by few existing approaches. The superiority of proposed approach of voltage control areas formation over few existing approaches has been established on the test system considered.
Implementation of DC voltage controllers on enhancing the stability of multi-...IJECEIAES
Because of the increasing penetration of intermittent green energy resources like offshore wind farms, solar photovoltaic, the multi-terminal DC grid using VSC technology is considered a promising solution for interconnecting these future energies. To improve the stability of the multi-terminal direct current (MTDC) network, DC voltage control strategies based on voltage margin and voltage droop technique have been developed and investigated in this article. These two control strategies are implemented in the proposed model, a ±400 kV meshed multi-terminal MTDC network based on VSC technology with four terminals during the outage converter. The simulation results include the comparison and analysis of both techniques under the outage converter equipped with constant DC voltage control, then the outage converter equipped with constant active power control. The simulation results confirm that the DC voltage droop technique has a better dynamic performance of power sharing and DC voltage regulation.
This document presents a new control scheme for a STATCOM (Static Synchronous Compensator) to improve power quality in a grid-connected wind energy system. A STATCOM equipped with a battery energy storage system is connected at the point of common coupling between the wind farm and the grid. The STATCOM control scheme uses a hysteresis current control technique to inject compensating current and regulate the grid voltage. Simulation results show the STATCOM can mitigate reactive power demand and harmonics, as well as respond quickly to changes in load to help regulate voltage and current waveforms at the point of connection to the grid.
Transmission System Operators and Owners are required to maintain a Black Start and System
Restoration Plan that has been thoroughly verified with studies. Combustion turbines are
typically used as Black Start generators, which then are used to start larger coal and combined
cycle plants. Steady state and transient studies are normally performed to verify whether voltage
and frequency are within limits so as not to interrupt the restoration process, and to ensure
large induction motors associated with the power plants can be started. In recent times, Battery
Energy Storage Systems (BESS) are being considered for black start system restoration, in
lieu of combustion turbines. The models that are currently available for BESS in transmission
planning software are meant to study synchronized operation of BESS, rather than an islanded
operation. In this paper, a modeling technique is presented for evaluating BESS for black start
system restoration. The performance of BESS for black start system restoration is compared
with the performance of a combustion turbine.
This document discusses testing procedures for motor bus bar transfer schemes. It focuses on verification of an in-phase transfer method. The paper provides background on voltage decay theory during motor bus bar transfers and discusses an example recording of actual voltage decay on a motor bus bar system. It also briefly describes other transfer methods before detailing a proposed testing protocol to evaluate the in-phase transfer method, including using calculations and simulations to determine the estimated time of phase coincidence during a transfer.
This document discusses constraints and load flow analysis in power systems. It outlines four key constraints: active power constraint, reactive power constraint, voltage magnitude constraint, and load angle constraint. It also describes load flow analysis as a balanced mechanism between demand and generation under incremental loading. Load flow analysis is important for the safe and future operation of power systems. The document further discusses bus classification, basic power flow conditions including the proportional relationships between reactive power and voltage and active power and load angle. It also covers the development of the Y-bus matrix considering line resistances and inductances alone and then including line capacitances.
This article proposes a novel scheme to improve the doubly-fed induction generator (DFIG) behavior during grid fault. The DFIG’s are sensitives to voltage variations when abrupt variations of the wind velocity arrive. For enhancing DFIG behavior, protecting the converters, and smoothing the fluctuations power output of the DFIG under sag voltage; a novel hybrid energy storage system scheme and its controller are proposed. The main advantages of our approach are a faster response and suppressing overvoltage on DC bus and globally less stress in the storage system. The control structure decreases the tiredness on the battery and restores the DC bus voltage rapidly, globally the battery system operating time increases. The results obtained by simulations in MATLAB validate the benefits of the suggested control.
This document discusses several topics related to power system operation and control:
1. It defines a control area as a region where all generators swing together in response to load changes or speed governor settings.
2. It explains that voltage stability refers to a power system reaching a stable post-disturbance voltage equilibrium.
3. It describes different approaches for steady-state security analysis, which test the system against contingencies by calculating changes and checking against constraints.
Influencing Power Flow and Transient Stability by Static Synchronous Series C...ijeei-iaes
This document summarizes research on using a Static Synchronous Series Compensator (SSSC) to improve power flow and transient stability in a Single Machine Infinite Bus (SMIB) system. The research models an SMIB system and analyzes its power angle curve and transient stability both with and without an SSSC. Results show that the SSSC is effective at stabilizing the system after a transient fault by controlling voltage injection and virtual line impedance. The SSSC allows the system to regain stability faster than without the SSSC. Therefore, the SSSC is concluded to be an effective means of influencing power flow and improving transient stability in power systems.
In this paper a grid interconnected system with wind energy source linked with a FACTs based SSFC device ( Static switched filter compensator ) at load for enhancing power quality is considered .Analysis is done for the proposed system by varying Carrier frequency over a wide range and observed system performance at all 3 busses wise Grid bus, Generator Bus and Load Bus. Two regulators are used to organize the FACTS SSFC-device, these are based on a tri-loop dynamic error obsessed inter-coupled input to VSC controller. Investigation is made in MATLAB/SIMULINK Environment for the proposed system ,it is observed that system performance in terms of percentage Total harmonic Distortion is satisfactory along with the Enhanced Power Quality.
Static Synchronous Series Compensator (SSSC) with Superconducting Magnetic En...IDES Editor
Static Synchronous Series Compensator (SSSC) has
been designed with Superconducting Magnetic Energy Storage
(SMES) system. A closed loop control scheme has been
proposed with PI controller and real and reactive powers are
taken as references. A 48 pulse voltage source inverter is
designed for the SSSC. Control scheme for the chopper circuit
of SMES coil is also designed. A three area system is taken as
the test system and the operation of SSSC with SMES is
analysed for various transient disturbances. Test results under
different disturbances and operating conditions show the
proposed SSSC with SMES is effective in damping out the
power system oscillations.
Modeling Optimization Voltage Index Unified Power Flow Controller Equivalent ...IJMTST Journal
This paper presents an active-reactive power control strategy for voltage source converters (VSCs) based on derivation of the direct and quadrature components of the VSC output current. The proposed method utilizes a multivariable proportional-integral controller and provides almost completely decoupled control capability of the active and reactive power with almost full disturbance rejection due to step changes in the power exchanged between the VSC and the grid. It also imposes fast transient response and zero steady-state error as compared to the conventional power control approaches. The applicability of the proposed power control strategy for providing the robust stability of the system against the uncertainties of the load parameters is also investigated. The superiority of the proposed control strategy over conventional approaches in the new condition of supplying the load is demonstrated. The theoretical aspects of the proposed multivariable-based power control strategy and the conventional approaches are reviewed and simulation results are presented in two separate sections. MATLAB/Simulink 2009a is used to simulate different scenarios of the simulation.
Iaetsd load frequency control for a distributed gridIaetsd Iaetsd
This document discusses load frequency control for a distributed grid system involving wind, hydro, and thermal power plants. It proposes using a PI controller to suppress frequency deviations caused by load and generation fluctuations from renewable resources connected to the grid. It models a system with four thermal plants, a wind farm, and a hydro plant in MATLAB. Load frequency control methods are explored to minimize deviations in area frequency and tie-line power interchange for reliable grid operation with both conventional and renewable resources.
Simulation of D-STATCOM to study Voltage Stability in Distribution systemijsrd.com
This document presents a simulation study of a D-STATCOM (Distribution Static Compensator) to improve voltage stability in a distribution system. It first provides background on voltage dips and describes the structure of a STATCOM, which includes a voltage source inverter, transformer, and controller. The simulation model of the D-STATCOM and distribution network is developed using SimPowerSystems blocks. Simulation results show that without the D-STATCOM, voltage dips to 0.93 p.u. during a load change, but with the D-STATCOM the voltage is stabilized at 1.0 p.u., demonstrating its effectiveness in mitigating power quality issues like voltage instability.
The peer-reviewed International Journal of Engineering Inventions (IJEI) is started with a mission to encourage contribution to research in Science and Technology. Encourage and motivate researchers in challenging areas of Sciences and Technology.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
This document presents the design and analysis of a microstrip patch antenna for triple band applications in digital communication systems. The antenna is designed to operate at 1.5 GHz, 2.4 GHz, and 5.5 GHz bands. It consists of a rectangular patch fed by a microstrip line with two additional arms of different lengths acting as resonators. Simulation results show the antenna achieves impedance matching across bandwidths of 700 MHz, 800 MHz, and 1 GHz at the three frequencies. It has an omnidirectional radiation pattern and gain between 5-6 dBi. The compact triple band design reduces the antenna size by 67% compared to a conventional patch antenna.
This document describes the design and implementation of a hybrid cryptosystem using the AES and SHA-2 algorithms. The system integrates AES, a symmetric encryption algorithm, with SHA-2, a cryptographic hash function, to improve data security. AES encrypts data using a 128-bit key generated by hashing the input message with SHA-2. The combined system was synthesized using Xilinx ISE software and implemented on a Virtex-5 FPGA, utilizing under 2% of slice registers and 5% of slice LUTs. This provides higher security than AES alone through increased algorithm complexity.
The document summarizes a 1-level discrete wavelet transform (DWT) image watermarking algorithm for embedding watermarks into RGB cover images. The algorithm applies 1-level DWT to decompose the RGB cover image and watermark into frequency subbands. It then inserts the watermark into the low-frequency approximation subband of the cover image using alpha blending. The watermarked image achieves good quality with high peak signal-to-noise ratio. The extracted watermark matches the original with a normalized correlation value close to 1, showing the algorithm efficiently detects the watermark. The algorithm is imperceptible and robust against various attacks like noise and filtering.
This document describes a proposed fuzzy logic-based weather advisory system. It begins with background on how agricultural productivity depends on weather and how weather forecasts can help farmers plan. It then discusses using a fuzzy approach to develop the system given the uncertain nature of weather. The rest of the document reviews related work applying fuzzy logic to weather-related problems and provides details on fuzzy logic and how it can model imprecise systems through membership functions and if-then rules. The overall goal is to develop a weather advisory system to help farmers minimize losses from adverse conditions.
This document discusses analyzing human personality characteristics from social media profiles using machine learning techniques. It collects over 3,000 profile summaries from LinkedIn using web scraping. It then uses the WordNet lexical database to form word clusters for extroversion and introversion characteristics. The k-nearest neighbors algorithm is used to classify profiles as extrovert, introvert, or ambivert based on the words in their summaries. The goal is to analyze users' profiles and provide guidance to write profiles that include a balance of introvert and extrovert traits classified as ambivert, which tends to be viewed more positively. Accuracy results from the classification approach are promising but not discussed in detail.
This document reviews the stir casting process for producing aluminum metal matrix composites reinforced with ceramic particles. It discusses key parameters of the stir casting process that must be properly controlled, including stirrer design and speed, stirring temperature and time, reinforcement feed rate, and pouring temperature. The document summarizes research on using stir casting to fabricate aluminum composites reinforced with silicon carbide particles, where factors like reinforcement volume ratio and particle size were investigated. The summary concludes that stir casting is an effective and economical technique for producing aluminum metal matrix composites when process parameters are properly optimized.
This document describes the design and analysis of a two half-ring and half circular patch microstrip antenna for dual-band applications in the C-band frequencies. The antenna is designed to operate at 4.1 GHz and 6.5 GHz with moderate return loss and gain. Simulation results show the antenna achieves a peak gain of 3.08 dB at 4.1 GHz and 4.14 dB at 6.5 GHz when fabricated on FR4 epoxy substrate with a dielectric constant of 4.4 and thickness of 3 mm. Current distribution and radiation patterns are also analyzed to understand the antenna performance at the resonant frequencies.
Implementation of XOR Based Pad Generation Mutual Authentication Protocol for...IOSR Journals
In RF link, without security the messages exchange between the two devices are monitoring by an
eavesdropper. So the exclusive-OR (XOR) based pad generation protocol is used to safely transfer the data to
the other point with necessary security and it maintaining confidentiality. This protocol produce the cover
coding pad to mask the access password before the datas are transmitted. A specially designed pad generation
will be implemented in digital domain to solve the insecurity problem in data communication RF link. This
protocol developed under regulation of ISO 18000 – 6 type C protocol also known as EPC C1G2 RFID
protocol. The linear feed back shift register (LFSR) generate the pseudo random binary sequence (PRBS) and it
is used as data source to the pad generation function. The Xilinx 13.x software is used for synthesize and
modelsim SE6.0 is used for simulating the result. The pad generation algorithm has been implemented in FPGA
Spartan 3 PQ208-4 board to verify the result
This document investigates the influence of construction parameters such as bitumen content, air void content, and compaction on the properties and performance of dense graded bituminous mixes. Samples were prepared and tested according to the Marshall mix design method at varying bitumen contents and compaction levels. Tests conducted included Marshall stability testing, indirect tensile strength testing, and wheel tracking tests. Relationships between bitumen content, air voids, indirect tensile strength, and pavement fatigue and rutting performance were examined using mechanistic-empirical pavement design modeling. The results indicate that construction parameters significantly influence mix properties and predicted pavement performance.
This document investigates the use of saw dust ash (SDA) as a stabilizing agent for an A-7-6 lateritic soil. Tests were conducted on mixtures of the soil with 2%, 6%, 8%, 12%, 16%, and 20% SDA by weight. Results showed the liquid limit and plasticity index decreased with increasing SDA content up to 12%, while maximum dry density decreased and optimum moisture content increased. Unconfined compressive strength initially decreased then increased up to a maximum of 164.2 kPa at 16% SDA, around 4 times the strength of the untreated soil. The 12% SDA mixture produced strengths of 118.5 kPa, a plasticity index of 11.6
Design of Anti-collision Technique for RFID UHF Tag using VerilogIOSR Journals
Abstract: This paper presents a proposed Reliable and Cost Effective Anti-collision technique (RCEAT) for Radio Frequency Identification (RFID) Class 0 UHF tag. The RCEAT architecture consists of two main subsystems; PreRCEAT and PostRCEAT. The PreRCEAT subsystem is to detect any error in the incoming messages. Then the identification bit (ID) of the no error packet will be fed to the next subsystem. The PostRCEAT subsystem is to identify the tag by using the proposed Fast-search Lookup Table. The proposed system is designed using Verilog HDL. The system has been successfully implemented in hardware using Field Programmable Grid Array (FPGA) SPARTAN 3E. Finally the RCEAT architecture is synthesized using xillins 13.3v. From the hardware verification results, it shows that the proposed RCEAT system enables to identify the tags without error at the maximum operating frequency of 180MHz. The system consumes 7.578 mW powers, occupies 6,041 gates and 0.0375 mm2 area with Data arrival time of 2.31 ns. Key words: FPGA,Spartan 3e,RCEAT,Verilog HDL,RFID tag,CRC.
This document provides an overview of digital image steganography and steganalysis. It discusses various image steganography techniques including least significant bit modification in the spatial domain, and algorithms like JSteg and F5 that operate in the transform domain. It also covers hybrid techniques like patchwork and spread spectrum. The document compares the techniques based on parameters like invisibility, bit rate, and robustness. Finally, it discusses steganalysis methods for detecting hidden information in images, including techniques based on higher-order image statistics.
This document provides a comparative study of existing intrusion detection systems for smartphones. It discusses 5 different intrusion detection approaches: 1) a cloud-based anomaly detection system, 2) a signature-based host-based IDS, 3) a rule-based host-based IDS called AMOXID, 4) an anomaly-based behavioral detection framework called Andromaly, and 5) an anomaly-based cloud-based detection system. It provides an overview of each approach and compares them based on parameters like detection method, positioning, type of analysis, alerts, scalability, pros, and cons. The conclusion is that combining anomaly and signature-based detection could improve attack detection performance for smartphones.
This document discusses a proposed method for lossless image compression that uses a hybrid of wavelet transforms, embedded zero tree coding, and Huffman coding. Specifically, it uses discrete wavelet transforms to decompose images into sub-bands, applies embedded zero tree coding to the wavelet coefficients to encode insignificant coefficients as zero trees, and then uses Huffman coding for further compression. Tables of results are presented showing compression ratios, bits per pixel, and PSNR values for images compressed with different threshold values in the wavelet decomposition. The goal is to determine an optimal threshold level for each decomposition to maximize compression while perfectly reconstructing the original image content.
The document analyzes and compares the C4.5 and K-nearest neighbor (KNN) algorithms for clustering data and determining priority development areas in Papua Province, Indonesia. It first discusses Klassen typology for classifying areas based on economic growth and per capita income. It then provides an overview of the C4.5 and KNN algorithms, including pseudo code for analyzing their time complexities using the Big O notation. The study applies these algorithms to PDRB and economic growth data from 29 regencies in Papua from 2006-2012 to determine priority development areas, running the algorithms multiple times on different sized data sets to analyze running time.
1) The document discusses recognizing handwritten Devanagari characters using an artificial neural network approach.
2) It proposes extracting features from images by dividing them into zones and calculating average pixel distances to the image and zone centroids.
3) This zone-based feature extraction method is used to create a feature vector for each character image that is then classified by a feedforward neural network.
Wireless Network Security Architecture with Blowfish Encryption ModelIOSR Journals
Abstract: In this research paper ,we developed a model for a large network, wireless nodes are interconnected and each can be considered as a node processor that offer services to other node processors connected to a specific network. A very high proportion of the nodes that offer services need to carry out an authentication process so as to make an access request to the node offering the service. In this context, an integrated reconfigurable network security architecture moved to the application layer has become the need of the day for secure wireless data sharing. The security schemes of the seven layer OSI architecture need to be placed intrinsically in the wireless node itself and should be capable of supporting the MAC layer, IP address based layer and the routing protocols of the network layer. This work focuses on the use of emulator and embedded hardware architectures for wireless network security. In this work, the individual nodes can have a unique security signature pattern maintained by respective wireless nodes using an encryption algorithm and this is made dynamic. The metrics includes latency, throughput, Scalability, Effects of data transfer operation on node processor and application data located in the processor Keywords:Wireless Network security, Embedded hardware, Reconfigurable architecture, blowfish algorithm
This document provides a review of e-learning in higher education. It begins with defining e-learning as the computer and network-enabled transfer of skills and knowledge to learners. It notes that e-learning has become an important part of education at all levels. The document then discusses the evolution of e-learning from using electronic media in traditional classrooms to fully online courses. It highlights that e-learning provides opportunities for continuous, lifelong learning. However, it also notes that e-learning will likely never replace traditional classroom learning entirely. The review explores the objectives, requirements and various definitions of e-learning. Overall, it aims to increase awareness of the importance of e-learning, especially when integrated with traditional methods of learning
1) The document proposes four techniques for facial feature extraction - 2DPCA, LDA, KPCA, and KFA. It uses these techniques to extract features from images in the ORL database, applies LDA for classification, and recognizes faces using a feedforward neural network (FFNN).
2) It compares the recognition rates of the different feature extraction techniques when using 10, 20, 30, and 40 hidden neurons in the FFNN. The technique that performs best is KPCA, achieving a maximum recognition rate of 94.82% using 20 hidden neurons.
3) In conclusion, the goal of implementing and comparing different feature extraction techniques with an FFNN classifier on face images was achieved. KPCA provided the best
This document provides a review of atypical hierarchical routing protocols for wireless sensor networks. It begins by introducing hierarchical routing and typical clustering routing in wireless sensor networks. It then describes several types of atypical hierarchical routing protocols, including chain-based, tree-based, grid-based, and area-based routing protocols. For each type, some representative protocols are described and their advantages and disadvantages are analyzed. The document concludes by comparing the performance of different chain-based hierarchical routing protocols based on factors like energy efficiency, scalability, delivery delay, and load balancing.
VSC BASED HVDC SYTEM DESIGN AND PROTECTION AGAINST OVER VOLTAGESIJERD Editor
High Voltage Direct Current system based on voltage source converter (VSC-HVDC) is becoming
more effective solution for offshore wind plants and supplying power to remote regions. In this paper, the
control of a VSC-based HVDC system (VSC-HVDC) is described. Based on this control strategy, appropriate
controllers utilizing PI controllers are designed to control the active and reactive power at each end station.The
operation performance of a voltage source converter (VSC) based HVDC (VSC-HVDC system) system is
explained under some characteristic faulted conditions with and without protection measures. A protection
strategy is proposed to enhance the continuous operation performance of the VSC-HVDC system. The strategy
utilizes a voltage chopper to suppress over-voltages on the DC side of the VSC. Digital simulation is done to
verify the validity of the proposed control strategy and protection strategy
This paper investigates the performance of line commutated converter (LCC) based monopolar HVDC transmission system feeding a weak AC network with hybrid reactive power compensators (RPC’s) at the inverter AC side. The hybrid compensator is an equal mix of any two of the following compensators: synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM). The HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal proportional integral (PI) controller for rectifier and inverter control. The transient performances of hybrid RPC’s (SC+SVC, SVC+STATCOM and SC+STATCOM) are judged under various fault conditions and the outcomes are compared with the performance of the SC, SVC and STATCOM to highlight the supremacy of the hybrid compensators. The simulation results validate that the equal mix of SC and STATCOM has a steady and fastest response. The results also demonstrate the superiority of the firefly algorithm based optimal PI controller over the conventional PI controller. The harmonic analysis is also carried out under steady state operation to assure the quality of power supply on the inverter AC side.
This document investigates the performance of a monopolar HVDC transmission system feeding a weak AC network using different reactive power compensators (RPCs). It analyzes the transient performance of hybrid RPC combinations including synchronous compensator (SC) + static VAR compensator (SVC), SVC + static synchronous compensator (STATCOM), and SC + STATCOM under various fault conditions. Simulation results show that the equal mix of SC and STATCOM has the steadiest and fastest response. The document also compares the performance of an optimal proportional-integral (PI) controller tuned with the firefly algorithm to a conventional PI controller. The firefly algorithm is used to minimize rectifier and inverter DC power errors to determine optimal PI gains.
IRJET- Comparative Study of Common Methods of Frequency Response using MTDC G...IRJET Journal
This document compares different control strategies for exchanging frequency support between AC power systems connected by a multi-terminal HVDC grid. It studies synthetic inertia control using frequency derivative input, classical frequency droop control, and an integrated synthetic inertia emulation control scheme. Time domain simulations show the impact of these controls on both HVDC grid voltage response and AC system frequency stability. Frequency droop control improves one AC system's frequency at the cost of disturbance to the other. Integrated synthetic inertia emulation control facilitates primary frequency reserve exchange similarly to droop control. The control strategies allow artificial coupling of HVDC-connected AC systems for frequency support.
- The document describes a unified power flow controller (UPFC) which consists of two voltage source converters connected respectively in series and shunt with a transmission line, with a common DC link.
- It proposes modeling the UPFC using a discrete simulator in MATLAB with 12-pulse converters to reduce voltage harmonics, and controlling the series and shunt converters separately while coordinating them.
- Simulation results showed the UPFC model reflected static and dynamic characteristics, and harmonics analysis was performed on the output during different system conditions including faults.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
vsc hvdc fuzzy controller for improving the stability of acdc power systemIndra S Wahyudi
This document describes a fuzzy logic controller that is proposed to improve the stability of an AC/DC power system using a Voltage Source Converter based HVDC (VSC-HVDC) transmission system. The controller monitors oscillations on the AC line parallel to the VSC-HVDC line and uses fuzzy logic rules to adaptively adjust the active power output of the VSC-HVDC in a way that dampens the oscillations. Simulation results on an IEEE 4-generator test system showed the controller effectively enhances the dynamic stability of interconnected power systems and is robust to different system operating conditions and oscillation modes.
Analysis of multi terminal hvdc transmission system feeding very weak ac netw...eSAT Journals
Abstract This paper presents a line commutated converter (LCC) based multi-terminal HVDC transmission (MTDC) system feeding very weak AC networks with hybrid reactive power compensators (RPC’s) at the inverter AC side. The hybrid compensator is accomplished by the equal mixing of any two of the following compensators: synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM). The four-terminal HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal proportional integral (PI) controller for rectifiers and inverters control. The transient performances of hybrid RPC’s (SC+SVC, SVC+STATCOM and SC+STATCOM) are studied under various fault conditions and the results are compared with the performance of the SC, SVC and STATCOM to focus the high quality of the hybrid compensators. The simulation results authorize that the equivalent mixture of SC and STATCOM has a steady and fastest response. The results also reveal the supremacy of the firefly algorithm based optimal PI controller over the conventional PI controller. The harmonic present in the inverter side AC quantities is also calculated under steady state operation to assure the quality of power supply. Keywords: MTDC, Very weak AC system, Hybrid RPC, PI controller, Firefly Algorithm.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Power quality optimization using a novel backstepping control of a three-phas...IJECEIAES
A novel nonlinear backstepping controller based on direct current (DC) link voltage control is proposed in three-phase grid-connected solar photovoltaic (PV) systems to control the active and reactive power flow between the PV system and the grid with improved power quality in terms of pure sinusoidal current injection with lower total harmonic distortion (THD), as well as to ensure unity power factor, or to compensate for reactive power required by the load, i.e., the electrical grid. The output power of the PV array is supplied to the grid through a boost converter with maximum power point tracking (MPPT) control and an inverter. Simulation results of the proposed controller show good robustness under nominal conditions, parameter variations, and load disturbances, which presents the main advantage of this controller as compared to an existing controller. The performance of this work was evaluated using a MATLAB/Simulink environment.
This document discusses methods for controlling voltages and reactive power in power system networks using automatic voltage regulators (AVRs) and static var compensators. It provides an overview of these control methods, including AVRs on generators for voltage regulation and static var compensators for reactive power support. The document evaluates the performance of these methods for enhancing voltage control, improving system stability, and minimizing reactive power flows and losses. Key methods discussed are synchronous generator excitation control using AVRs, transmission system voltage control using shunt capacitors and static var compensators.
Hybrid energy storage system control analogous to power quality enhancement o...IJECEIAES
Increasing nonlinear loads and power electronic converters lead to various power quality issues in microgrids (MGs). The interlinking converters (ILCs) can participate in these systems to harmonic control and power quality enhancement. However, ILC participation deteriorates the dc link voltage, system stability, and storage lifetime due to oscillatory current phenomena. To address these problems, a new control strategy for a hybrid energy storage system (HESS) is proposed to eliminate the adverse effects of the harmonic control operation of ILC. Specifically, battery and super-capacitor (SC) are used as HESSs that provide low and high power frequency load, respectively. The proposed strategy tries to compensate the current oscillation imposed by ILC with fuzzy control of HESS. In this method, a proportional-resonant (PR) controller integrated with harmonic compensator (HC) is employed to control the ILC for power quality enhancement and oscillatory current elimination. The main advantages of the proposed strategy are to reduce DGs power fluctuations, precise DC bus voltage regulation for generation and load disturbances, improved grid power quality under nonlinear load and transition conditions. The performance of the proposed method for isolated and grid-connected modes is verified using simulation studies in the MATLAB software environment.
Steady State Fault Analysis of VSC- HVDC Transmission SystemIRJET Journal
This document summarizes research on modeling and analyzing steady state faults in a voltage source converter (VSC) high voltage direct current (HVDC) transmission system. It presents the following:
1) A dynamic model of a VSC-HVDC back-to-back system is developed including VSC converters, AC and DC filters, and cables. Vector control is used to independently control active and reactive power.
2) Simulation cases demonstrate startup and steady state response, as well as the system's ability to independently control active and reactive power through step changes.
3) Additional cases show the system maintains stability under a voltage sag at one station and a three-phase fault at the other station, recovering quickly
Low voltage ride through control of modular multilevel converter based hvdc s...Ghazal Falahi
Low Voltage Ride Through (LVRT) is an important grid requirement for Voltage Source Converter (VSC) based HVDC links. This paper studies the performance of the modular multilevel converter (MMC) VSC based HVDC systems during faults or voltage dips and proposes a new control strategy to improve the LVRT performance. The proposed algorithm controls the system to generate the required active and reactive powers that are calculated mathematically based on the ratings of the MMC-HVDC system and LVRT requirements. The injected active and reactive power values obey the LVRT guidelines and are adaptable to different grid codes. The mathematical calculations are presented and EMTDC/PSCAD simulation evaluates the performance of the proposed method.
The document discusses unified power quality conditioners (UPQC) and their use in compensating for power quality issues. Some key points:
1) An UPQC is proposed that uses an artificial neural network controller to compensate for unbalanced grid voltages and load voltages in a power system, correcting issues like voltage sags/swells, power factor correction, and voltage/current harmonic cancellation.
2) The UPQC regulates grid and load voltage unbalances and total harmonic distortion using an artificial neural network controller. In addition to correcting voltage and current disturbances, the controller provides phase detection and grid synchronization.
3) UPQCs are able to compensate for most power quality issues like voltage sags/swells and
Voltage-current Double Loop Control Strategy for Magnetically Controllable Re...Kashif Mehmood
Voltage regulation depending on reactive power
compensation is the main feature of the AC power supply
system. Magnetically controllable reactors (MCR) are
becoming a growing demand for this purpose. The structure
and working principles of MCR are analysed in this paper
while a simulation model is established. The reactive power
compensation strategy based on a single loop voltage control
system (SLVCS) is presented and a double loop
voltage-current control system (DLVCCS) is proposed. A
comprehensive scenario is developed to mitigate reactive power
compensation by using the proposed controls. Simulation
results substantiate that proposed controls of MCR has a faster
response in comparison to the traditional control, and it
provides the least voltage variation at the line end. It also
shows that the proposed control on MCR meet the desired
objective of the voltage regulation and provides flexibility to ac
transmission system
IRJET- Enhancement of Power Flow Capability in Power System using UPFC- A RevieWIRJET Journal
This document reviews the use of a Unified Power Flow Controller (UPFC) to enhance power flow capability in power systems. The UPFC is a flexible AC transmission system (FACTS) device that can control both real and reactive power flows on a transmission line. It consists of two voltage source converters connected by a DC link: a static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC). The STATCOM controls reactive power and the DC link voltage, while the SSSC injects a controlled AC voltage in series with the transmission line to vary the transmission line impedance and power flow. Simulation results show that a UPFC installed on the IEEE 5 bus test system can control power flows and
Analysis of Six Active Power Control Strategies of Interconnected Grids with ...Power System Operation
In this paper, the generator angle stability of several active power control schemes of a
voltage-source converter (VSC)-based high-voltage DC (HVDC) is evaluated for two interconnected
AC systems. Excluding frequency control, there has been no detailed analysis of interconnected grids
depending upon the converter power control, so six different types of active power control of the
VSC-HVDC are defined and analyzed in this paper. For each TSO (transmission system operator),
the applicable schemes of two kinds of step control and four kinds of ramp-rate control with a droop
characteristic are included in this research. Furthermore, in order to effectively evaluate the angle
stability, the Generators-VSC Interaction Factor (GVIF) index is newly implemented to distinguish
the participating generators (PGs) group which reacts to the converter power change. As a result,
the transient stabilities of the two power systems are evaluated and the suitable active power control
strategies are determined for two TSOs. Simulation studies are performed using the PSS®E program
to analyze the power system transient stability and various active power control schemes of the
VSC-HVDC. The results provide useful information indicating that the ramp-rate control shows a
more stable characteristic than the step-control for interconnected grids; thus, a converter having a
certain ramp-rate slope similar to that of the other generator shows more stable results in several cases.
In this paper, using a neural controller and a genetic optimization algorithm to control the voltage as well as, control the frequency of the grid along with the management of the reactive power of the micro-grid to control the output power during islanding using Simultaneous bilateral power converters with voltage/frequency droop strategy and optimization of PI coefficients of parallel power converters by genetic-neural micro-grid algorithm to suppress AC side-current flow that increases stability and improvement of conditions frequency and voltage are discussed. Given the performance of the micro-grid in two simulation scenarios, namely transition from on-grid to off-grid, the occurrence of a step change in load in island mode as well as return to working mode is connected. The ability to detect the robust performance and proper performance of two-level neural controller. The controller performance time was also very good, indicating the appropriate features of the method used to design the controller, namely two-level neural, genetics. The main advantage of this method is its simplicity of design. The method used is also efficient and resistant to changes in the system, which results from the simulations.
Performance of PWM Rectifier with Different Types of Loadijsrd.com
The paper presents the decoupled vector control of the PWM rectifier with the nonlinear DC-link voltage regulation and the load compensating feed forward. The concept of the proposed control system is based on Voltage Oriented Control with Space-Vector Pulse Width Modulation (SV-PWM). For the high-performance operation of the PWM rectifier and the satisfactory current tracing the decoupled current control has been introduced. The performance of the linear PI controller of the DC-link voltage is strictly dependent on its settings and it may introduce a disadvantageous voltage overshoot under a heavy load impact. In order to improve the transient response of the DC-link voltage control loop a load compensation has been proposed. The different approach to the control of the DC-link voltage based on the regulation of the square power of the DC voltage has been introduced.
This document provides a technical review of secure banking using RSA and AES encryption methodologies. It discusses how RSA and AES are commonly used encryption standards for secure data transmission between ATMs and bank servers. The document first provides background on ATM security measures and risks of attacks. It then reviews related work analyzing encryption techniques. The document proposes using a one-time password in addition to a PIN for ATM authentication. It concludes that implementing encryption standards like RSA and AES can make transactions more secure and build trust in online banking.
This document analyzes the performance of various modulation schemes for achieving energy efficient communication over fading channels in wireless sensor networks. It finds that for long transmission distances, low-order modulations like BPSK are optimal due to their lower SNR requirements. However, as transmission distance decreases, higher-order modulations like 16-QAM and 64-QAM become more optimal since they can transmit more bits per symbol, outweighing their higher SNR needs. Simulations show lifetime extensions up to 550% are possible in short-range networks by using higher-order modulations instead of just BPSK. The optimal modulation depends on transmission distance and balancing the energy used by electronic components versus power amplifiers.
This document provides a review of mobility management techniques in vehicular ad hoc networks (VANETs). It discusses three modes of communication in VANETs: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and hybrid vehicle (HV) communication. For each communication mode, different mobility management schemes are required due to their unique characteristics. The document also discusses mobility management challenges in VANETs and outlines some open research issues in improving mobility management for seamless communication in these dynamic networks.
This document provides a review of different techniques for segmenting brain MRI images to detect tumors. It compares the K-means and Fuzzy C-means clustering algorithms. K-means is an exclusive clustering algorithm that groups data points into distinct clusters, while Fuzzy C-means is an overlapping clustering algorithm that allows data points to belong to multiple clusters. The document finds that Fuzzy C-means requires more time for brain tumor detection compared to other methods like hierarchical clustering or K-means. It also reviews related work applying these clustering algorithms to segment brain MRI images.
1) The document simulates and compares the performance of AODV and DSDV routing protocols in a mobile ad hoc network under three conditions: when users are fixed, when users move towards the base station, and when users move away from the base station.
2) The results show that both protocols have higher packet delivery and lower packet loss when users are either fixed or moving towards the base station, since signal strength is better in those scenarios. Performance degrades when users move away from the base station due to weaker signals.
3) AODV generally has better performance than DSDV, with higher throughput and packet delivery rates observed across the different user mobility conditions.
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Nordic Marketo Engage User Group_June 13_ 2024.pptx
D010121832
1. IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)
e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 10, Issue 1 Ver. II (Jan – Feb. 2015), PP 18-32
www.iosrjournals.org
DOI: 10.9790/1676-10121832 www.iosrjournals.org 18 | Page
Controllers For A VSC-HVDC Link Connected To A Weak AC
System
R.S. Geetha1
, Ravishankar Deekshit2
, G.Lal3
,
1
Department of Electrical and Electronics, BMS College of Engineering, Bangalore,India
2
Electronics Division, BHEL, Bangalore, India
Abstract: In this paper, the interconnection of a strong AC system to a weak AC system by using a Voltage
Source Converter (VSC) based High Voltage DC (HVDC) transmission system is investigated. In this work, the
weak AC system considered is an island system comprised of synchronous generators and passive load. Analysis
is carried out for UPF load and inductive load. The ac filter requirement to achieve the required response for
UPF and inductive load is carried out. For efficient functioning of the system considered, proper designing of
the controllers is an important factor. The controller parameters are designed using Modulus Optimum
technique and Symmetric optimum method. The performance analysis of VSC-HVDC is carried out for power
transmission in the DC link for load variation in the island system. Simulations are carried out in MATLAB/
Simulink / Sim Power Systems and the results are presented.
Keywords: Voltage Source Converter; PI controllers parameters; VSC-HVDC; Modulus optimum; Symmetric
optimum; weak AC system; island system; Power order
I. Introduction
For HVDC transmission, the strength of the ac system is important for normal operation. A measure of
the strength of the ac system is given by the short circuit ratio (SCR). SCR is defined as the ratio between the
short circuit capacity of the ac network and the nominal DC power level. An AC system is usually regarded as
weak, if SCR is lower than 3 [1]. In the conventional line-commutated HVDC technology, the commutation of
the converter valves is dependent on the stiffness of the alternating voltage supplied by the ac system. The
converter cannot work properly if the connected ac system is weak [2]. Some of the important consequences that
are to be addressed when a HVDC system is connected to a weak AC system are: high temporary over voltages,
low frequency resonances, risk of voltage/power instability, long restart times and high risk of commutation
failures[1] [3][4]. Synchronous condensers can be used to increase the short circuit capacity of the AC system.
But, the use of synchronous condensers substantially increases the investment and maintenance cost of the
HVDC project. With the advent of semiconductor technology, devices with turn off capability like Gate Turn
Off Thyristor (GTO) and Insulated Gate Bipolar Transistor (IGBT) make the Voltage Source Converter (VSC)
attractive for HVDC transmission[5]. Some of the problems faced in connecting HVDC transmission system to
a weak AC system can be overcome by using VSC based HVDC system (VSC-HVDC). Among many
advantages of VSC-HVDC [6][7], the property of independent control of active and reactive power may be used
for overcoming the problem of voltage/power instability, when HVDC system is connected to a weak AC
system.
The voltage/power controllability of the VSC-HVDC system is determined by the controllers included
in the system. Adequate performance of the VSC-HVDC system under diverse operating conditions depends on
the selection of robust parameters for the control system [8]. Usually, due to their simple structure and
robustness, PI controllers are used to adjust the system for desired response. An overview of VSC-HVDC
technology is given in [9], wherein some aspects of model and control are discussed. A control system for VSC-
HVDC during island operation is proposed in [10], and it has been found that, the current limit of the converter
has a significant influence on the dynamic response of the system. Control methodologies based on sliding
mode control for controlling active and reactive power are addressed in [11]. An optimal control strategy for a
HVDC light system using a direct current vector control mechanism is proposed in [12], where the control
mechanism operates by either using PI control technique, or integrating PI, fuzzy and adaptive control
techniques together. Different control approaches like Internal Model Control (IMC) and H∞ control are
applied for designing controllers for VSC-HVDC connected to weak AC systems [13]. These two design
approaches are used for power-synchronization control, which has also been proposed for interconnection of
two very weak AC systems [2] . The power synchronization control method is similar to power angle control
method and uses phase angle and voltage magnitude to directly control active power and reactive power.
Typical problems such as resonant peak at grid frequency and converter over current limitation are taken care in
power synchronization method [14]. The modeling and control of VSC-HVDC links connected to Island
Systems is discussed in [15]. The control method in this paper is based on the power synchronization control for
2. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 19 | Page
grid connected VSCs. In [16], a sliding mode controller is proposed for a VSC-HVDC transmission link, and
results have been provided for a variety of operating conditions such as, changes in short circuit ratio, converter
parametric changes, and faults on the converter and inverter buses.
A detailed discussion on tuning techniques of converter controllers for VSC-HVDC is carried out in
[8], by using Modulus optimum method and Symmetric optimum method for a system that is comprised of an
ac source/ grid connected to a Pulse Width Modulated (PWM) VSC. The control of the converter aims at
regulating the dc voltage Vdc and maintaining a balance between the dc link power and ac power supply.
In this work, the control techniques described in [8], are used for the analysis of behavior of a VSC-
HVDC system connected to an island system . The island system chosen is a weak AC system with synchronous
generators of total short circuit rating of 516MVA and passive load. The analysis is carried out for UPF load, as
well as for an inductive load of 0.85 power factor. The total active load in the island system is assumed to be of
400MW, out of which, 300MW is considered to be a critical load, that has to be supplied by the VSC-HVDC
transmission system. Hence, the VSC-HVDC link is designed to supply a maximum load of 300MW. The
difference power is supplied by the synchronous generators in the island system. The simulation is carried out for
different load settings. Remaining part of the paper is organized as follows: In section II, the topology of the
system under consideration is explained. In section III, the tuning of the controllers for the considered system are
presented. In section IV, the dynamic performance of the active power controller, reactive power controller, DC
voltage controller and AC voltage controller are carried out. Also, the operation of VSC-HVDC link for load
variation in the island system is analyzed.
II. Circuit Topology
Fig. 1 shows the topology of the VSC-HVDC system connected to a weak AC system. The topology involves two
VSCs, VSC-1 and VSC-2. VSC-1 is a rectifier and VSC-2 is an inverter. VSC-1 is connected to a strong AC
system through reactor and converter transformer. VSC-2 is connected to an island system, which is a weak AC
system represented as AC system-2. The two converters are linked through a DC cable. The phase reactors
smoothen the current and secure the power exchange between AC system and DC link. The capacitors are used
for voltage support and harmonic attenuation.
Fig. 1. Basic VSC based HVDC scheme connected to an island system
III. Tuning Of The Controllers
Depending on the type of controllers used, the main control topologies for VSC station are: 1)Fixed DC
voltage control mode 2) Fixed DC current or power control mode 3) Fixed AC bus voltage control mode
4)Variable frequency control mode. Usually in the VSC-HVDC transmission systems, one VSC station uses
fixed DC voltage control mode and the other uses fixed DC current control mode or fixed AC bus voltage
control mode according to the requirement [17],[18]. In this work, the maximum power in the DC link is
restricted to 300MW. Hence, an active power controller is used in the rectifier side of the DC link. The reactive
power controller used in the rectifier side controls the reactive power exchange between the VSC-1 and AC
system-1 to maintain constant voltage at PCC. Since it is important to maintain the DC link voltage constant at
the inverter input terminals, a DC voltage controller is used on the inverter side. In addition to this, AC voltage
controller is also used in the inverter side to maintain constant AC voltage at the inverter output. For proper
steady state and dynamic performance of these controllers, it is required to tune the controller parameters. In the
following sections, tuning techniques used for different controllers of the system considered are described.
Fig. 2 shows the block diagram of the control structure of the overall system. Basically, in this control
scheme, the actual current in the reactor, i.e., iabc is controlled using a dq reference frame through a inner
current controller. As shown in Fig. 2, the reference parameters for the inner current controller are obtained
3. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 20 | Page
from the outer controllers, namely, active power controller, reactive power controller, DC voltage controller and
AC voltage controller. In such cascade control structure, the inner loop response must be faster when compared
to the speed of response of the outer loop. Hence, internal loop is designed to achieve fast response. The inner
loop is tuned according to “Modulus optimum” condition because of fast response and simplicity. This method
provides a relatively fast and non-oscillatory closed-loop tracking response.
Fig.2 Block diagram of control strategies for VSC_HVDC
3.1.1 Modulus Optimum Tuning Criteria
For low order controlled plants without time delay, the modulus optimum (absolute value optimum
criterion) is often used in the conventional analog controller tuning [19]. When the controlled system has one
dominant time constant and other minor time constant, the standard form of the control system transfer function
for the modulus optimum is achieved by cancelling the largest time constant, while the closed loop gain should
be larger than unity for as high frequencies as possible [8]. This method is widely used because of its simplicity
and fast response.
The outer controllers have to be relatively slower when compared to the inner current controller. One tuning
technique that satisfies this criteria is the Symmetrical Optimum tuning method.
3.1.2 Symmetrical Optimum method
A symmetrical optimum design criterion results in a controller that forces the frequency response of the
system as close as possible to that for low frequencies. In this method, the phase margin is maximized. As phase
margin is maximized for given frequency, the system can tolerate more delays. This method optimizes the
control system behaviour with respect to disturbance input. The method has well established tuning rules and
has good disturbance rejection [20]. An extended approach of tuning by symmetric optimum is presented in
[21]. The various controllers used in this work are explained in detail in the following section. In the ensuing
discussions, the various reference parameters and output values of the controller block are in per unit.
3.2.1 Inner Current Controller
The basic equation describing the system behavior for the rectifier mode of operation is given by equation (1).
1
1
11 tabc
sabc
sabcsabc v
dt
di
LRiv (1)
where, vsabc1 is the balanced 3phase voltage of the AC system-1, vtabc1 is the converter input voltage, L is the
reactor inductance and R is the reactor resistance.
Transforming equation (1) to dq frame,
tdsqsdsd ViLuV (2)
tqsdsq
sq
sq ViLRi
dt
di
LV
(3)
The voltage across the reactor is represented as usd, and is given by
sdsd
sd
sd iRLsRi
dt
di
Lu
(4)
4. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 21 | Page
where, Vsd, Vsq are the d and q components of ac voltage Vabc1 , usd is the d component of the voltage drop across
the phase reactor, isd, isq are the d and q component of the ac current iabc .
The structure of the inner current controller implemented in the synchronous reference frame based on equations
(2), (3) and (4) for VSC-1 station, is shown in Fig. 3. Similar equations can be developed for VSC-2 station.
Fig. 3. Structure of the inner current controller for the rectifier
Choosing appropriate values for the parameters of the PI controller shown in Fig. 3 is a challenging task.
Here, in order to find these parameters, the system involving the inner current controller is represented in terms of
the transfer functions of the various components of the system as shown in Fig. 4.
Fig. 4 Block diagram of the inner current controller
In the block diagram, the delay caused due to switching of the devices in the converter is represented by
PWM converter block, which involves a time component Ta, and is given by
switchf2
1
2
switchT
aT
(5)
where, fswitch is the switching frequency and is chosen to be 1350Hz.
The plant is represented by the transfer function:
pupu sLR
1
where, Rpu and Lpu are the per unit value of the resistance and inductance of the reactor.
The equation representing the PI regulator is:
siT
siT1
pK
s
iK
pK)s(R (6)
The controller parameters Kp and Ti =Kp/Ki need to be designed for an optimum performance.
The open loop transfer function for the current controller of Fig. 4 is given as,
pupuai
i
pup)OL(c
s1
1
R
1
sT1
1
sT
sT1
KG (7)
Applying modulus optimum tuning criteria for this system, the PI controller parameters are given as,
Ti=τpu (8)
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DOI: 10.9790/1676-10121832 www.iosrjournals.org 22 | Page
pu
pu
pu
R
L
(9)
a
pupu
pup
T2
R
K ; (10)
Hence, the open loop and closed loop transfer functions of the current control loop are given by equations (11)
and (12) respectively.
)saT1(s
1
aT2
1
)OL(cG (11)
1saT22s2
aT2
1
)CL(cG (12)
The resulting system has a frequency of natural oscillation
2T
1
a
n and damping factor
2
1
.
3.2.2 Active power controller
The active power (Pac) is expressed in d and q components of the voltage and current [21], and is given by
equation (13). In steady state, vsq=0 and hence, Pac is given by equation (14).
)]t(i)t(v)t(i)t(v[
2
3
)t(P sqsqsdsdac (13)
)]t(i)t(v[
2
3
)t(P sdsdac
(14)
A closed loop control is used for controlling the active power as shown in Fig.5. In the control
methodology, the actual power Pac as given by equation (14) is compared with the power to be transmitted (Pref),
and the error is passed through a simple PI controller. The active component of the reference current ( idref ) for
the inner current controller is derived from this PI controller.
The sampling block represents the delay introduced for the analog to digital conversion and it is represented by
a first order transfer function with a time constant 0.5Ts, where Ts=1/fswitch.
The Kp and Ki values of the controller depend on the settling time of the step response of the active
power control block of Fig. 5. These values are tuned to get good dynamic response.
Fig. 5 Block diagram of the Active power controller
3.2.3 Reactive power controller
The reactive power (Qac) is expressed in d and q components of the voltage and current [22], and is given by
equation (15). In steady state, vsq=0 and hence, Qac is given by equation (16). For a given reactive power (Qref),
the reference reactive current iqref , for the inner current controller can be derived using equation (17).
The block diagram of the outer reactive power controller is shown in Fig. 6.
)]t(i)t(v)t(i)t(v[
2
3
)t(Q sdsqsqsdac . (15)
)]t(i)t(v[
2
3
)t(Q sqsdac (16)
sdv3
refQ2
qrefi (17)
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DOI: 10.9790/1676-10121832 www.iosrjournals.org 23 | Page
Fig. 6 Block diagram of the Reactive power controller
3.2.4 DC voltage controller
The power balance relationship between the ac input and dc output of VSC is given in (18).
dcdcsqsqsdsdac IV)]t(i)t(v)t(i)t(v[
2
3
)t(P
(18)
where, Vdc and Idc are the DC link voltage and current on the output side of VSC-1 respectively as shown in
Fig.1. With vsq=0 in steady state, equation for Idc as derived from (18) is given as:
)t(i
)t(V
)t(v
2
3
I sd
dc
sd
dc
(19)
It is also seen that, Idc is related to Vdc and IL , the dc link current as given in (20).
L
dc
dc I
dt
dV
CI
(20)
Substituting (19) in (20), the current through the capacitor (Ic) can be obtained as:
Lsd
dc
sd
c
dc
Ii
V
v
2
3
I
dt
dV
C
(21)
Equation (21) is a non linear equation representing the dynamics of DC link. The linearized form of (21) is:
sd
refdc
sd
c
dc
i
V
v
2
3
I
dt
Vd
C
(22)
Using Laplace transformation :
s.C
1
V
v
2
3
i
)s(V
refdc
sd
sd
dc
(23)
The system block diagram for DC voltage controller based on equations (19) to (23), expressed in pu values is
shown in Fig. 7.
Fig. 7 Block diagram of the DC voltage controller
In the diagram, R(s) represents the PI regulator and is given by :
7. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 24 | Page
sT
sT1
K)s(R
iv
iv
pupv (24)
The inner current controller is represented by approximated transfer function, where Teq=2Ta.
The open loop transfer function of the system without considering the disturbance input is given by,
s
C
V
v
sT1
1
sT
sT1
KG
pub
pudc
pusd
eqiv
iv
pupv)OL(v (25)
As seen from equation (25), the open loop transfer function of the voltage controller already has two
poles at the origin. Hence, the modulus optimum tuning criteria is not effective in this situation. In such
situation, Symmetrical optimum method has been considered to tune the controllers [8].
Introducing
pudc
pusd
V
v
K and
pub
c
C
1
T ; the transfer function can be written as
ceqiv
iv
pupv)OL(v
sT
1
sT1
K
sT
sT1
KG (26)
It can be shown that [8], Tiv=a2
Teq, where Teq=2Ta. (27)
eq
c
eqiv
c
pupv
aKT
T
TTK
T
K (28)
The recommended value of the ratio Tiv/Teq is constrained between 4 and 16 in literature [23]. Whereas,
most of the literature use Tiv/Teq =4, (i.e., a=2) for the optimization according to conventional symmetrical
optimum tuning [21]. In this work, a=3 is chosen for controller design.
3.2.5 AC Voltage controller
This controller is used in the inverter side of the transmission system. As stated earlier, the function of
this controller is to maintain the AC voltage in the inverter output at the reference value. Fig. 8 shows the block
diagram of the AC voltage controller. In this controller, the voltage across the AC filter on the inverter side (vcf)
as shown in Fig. 2, is compared with the reference AC voltage, and the error is passed through a PI controller.
The required amount of reactive power (Qref) to be supplied for maintaining the AC voltage constant at the
reference value is derived from this PI controller. The reactive current iqref is derived from Qref, by using (17).
The q component of the AC current isq tracks iqref. The vcf value is computed using (29):
sC
1
iv
f
sqcf
(29)
Fig. 8 Block diagram of AC voltage controller
Kp and Ki values of the PI controller depend on the settling time of the step response of the AC voltage
control block of Fig. 8. All the controller parameters of VSC-1 station and VSC-2 station computed as described
in the preceding section are summarized in Table 3.
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DOI: 10.9790/1676-10121832 www.iosrjournals.org 25 | Page
Table 3. PI Controller Parameters For VSC-1 And VSC-2.
Station Controller K p pu K i pu
VSC-1 Current controller 0.6118 1.755
Active power controller 0.01 45
VSC-2 Current controller 0.6118 1.755
DC voltage controller 1.738 259.40
AC voltage controller 0.00776 0.228
In the following section, the simulation results of VSC-HVDC system incorporating all the controllers
discussed in this section are presented.
IV. Simulation Results
Simulation studies have been carried out for the system shown in Fig. 9. It is seen that,
1. AC system-1 is a strong system with Short Circuit (SC) level of 3500 MVA
2. AC system-2 is a weak system with SC level of 516 MVA
3. There is a local load of 50MW at PCC-1
4. There is a fixed load of 300MW and a varying load of 100MW at PCC-2.
The proposed VSC-HVDC system is designed for a constant active power transmission of 300MW. The
generators in AC system-1 are rated to generate power slightly greater than 350MW to take into account the
transmission line losses. Out of this, 300MW is transmitted over the VSC-HVDC line and supplied to the load in
AC system-2 and 50MW of power is supplied to the local load of AC system-1. If the load demand is more than
300MW in AC system-2, the local generators supply the difference power. The complete system data is provided
in Table 4.1.
Fig.9 Single line diagram of system
Table 4.1. System Data
AC system-1 1) Equivalent AC source representing a set of generators with a total SC level of 3500MVA
L-L voltage: 220kV, Frequency: 50Hz
2) A local load of 50MW, 220kV
AC system-2 1) Equivalent AC source representing two parallel connected synchronous generators with a
total SC level of 516MVA
L-L voltage : 220kV , Frequency: 50Hz
2) Passive load of maximum 400MW, 220kV
Converter transformer 315MVA,50Hz
Winding 1 : Y connected, 220kV(L-L rms), Resistance:0.002pu, Leakage reactance:0.08pu
Winding 2 : Δ connected, 150kV(L-L rms), Resistance:0.002pu, Leakage reactance:0.08pu
DC cable R=1.39e-2 Ω/km, L=1.59e-4 H/km, C=2.31e-7 F/km, length=100 km
DC link and Reactor DC voltage:±150kV, Rated Power:300MW, DC capacitor: 70μF
Reactor inductance=0.034 H, Reactor resistance =0.10Ω
System studies have been carried out for Unity Power Factor (UPF) load and an inductive load of 0.85 power
factor (pf) to assess the performance of VSC-HVDC system with respect to:
(a) Power controllability
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DOI: 10.9790/1676-10121832 www.iosrjournals.org 26 | Page
(b) AC filter requirement for AC system of VSC-1
(c) DC voltage and AC voltage controllability
(d) AC filter requirement for AC system of VSC-2
For the ensuing discussion, the nomenclature is given in Appendix 1.
(a) Power controllability in the DC link:
The DC link power is controlled by the active power controller of VSC-1 station. The reference active
power of this controller is fixed to a value slightly greater than 300MW (to account for DC line transmission
losses). Since the converter is considered to be lossless, the DC link power (PDC) is equal to the input AC power
(Pac) to VSC. In the first case considered for simulation studies, the load in AC system-1 and AC system-2 are
chosen to be 50MW, UPF and 300MW, UPF respectively. The simulation results are shown in Fig 10(a). As seen
from the results, the active power generated (Pac PCC-1) is around 350MW and the reactive power (Qac PCC-1) is
nearly zero, since the load is UPF. As observed from Fig. 10(a), the active power supplied to the local load (PL
PCC-1) is around 50MW. The power in the DC link is restricted to 300MW as seen in Fig. 10(a), which is due to
the robust active power controller. The settling time for these parameters is observed to be around 0.1 sec.
Fig. 10 (a) Active and reactive power at PCC1 , Power supplied to local load, active power of DC
link and reactive power for UPF load.
In the second case considered for simulation studies, the load in AC system-1 and AC system-2 are
chosen to be 50MW, UPF and inductive load of 300MW, 0.85 pf respectively. The simulation results were found
to be same as that shown in Fig 10(a). From the results, it is observed that, the inductive load in the AC system-2
has not affected the power flow in the VSC-HVDC system.
In the third case, the load in AC system-1 and AC system-2 are chosen to be inductive load of 50MW,
0.9 pf and 300MW, 0.85 pf respectively.
The results are shown in Fig. 10(b). It is observed that, when the load at PCC1 is changed to inductive
load of 0.9 pf, the active and reactive power reach steady state value at around 0.04 sec, unlike the case with
UPF load. Also, the waveforms have less ripple when compared to UPF load. The power flow in the DC link is
maintained at around 300MW.
From the results shown it is found that, the controllability of power in the DC link is found to be good in
all the three cases due to the robust active power controller.
Fig. 10(b ) active and reactive power at PCC-1 , Power supplied to local load, active power of DC link and
reactive power for 300MW, 0.85 pf load
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DOI: 10.9790/1676-10121832 www.iosrjournals.org 27 | Page
To further test the robustness of the controllers, the load demand is suddenly increased to 400MW, UPF, at time
t=0.7 sec in AC system-2. Under this condition, the DC link has to supply 300MW and the generators in AC
system-2 have to supply the remaining 100MW. It is seen from the results presented in Fig. 10(c), that these
conditions are satisfied. Under this situation, it is also seen that, the generators are able to generate the
difference power of 100MW within 0.76 secs. A small disturbance is seen in reactive power at 0.7 sec, but it
settles back again to zero at around 0.76 secs. The power supplied to the variable load at PCC-2 , active power
of the VSC-HVDC link and reactive power between VSC-2 and AC system-2 are also shown in Fig. 10(c). It is
observed that, at 0.7 secs, there is an increase in the load supplied. The delay time for the active power to reach
100MW is 0.06 sec, (approximately 3 cycles). From the figure, it is seen that, the active power in the DC link is
subjected to small disturbance at 0.7secs. But, due to fast controllability of the active power controller, it is able
to settle back to 300MW in approximately 0.05 sec. It is also observed that, there is a reactive power
requirement of around 50MVAR at the inverter side of VSC-2. Due to the good performance of the reactive
power controller in VSC-2, it remains constant after subjected to small deviations between 0.7 and 0.76 sec. The
results for sudden increase in the load demand to 400MW, 0.85pf lag at AC system-2 are shown in Fig.10 (d). It
is observed from results that, the response time for the active power controller is approximately 0.045 sec and
the waveforms are smoother.
Fig 10. (c ) Power controllability under dynamic load conditions for UPF load
Fig 10. (d ) Power controllability under dynamic load conditions for inductive load
From the above discussions, it is seen that, a constant power flow in VSC-HVDC system is attained
for UPF as well as inductive load in the weak AC system. In all the above cases considered for simulation, it is
observed that, any change in the active power is not affecting the reactive power. This independent control of
active and reactive power control is achieved through robust controllers in VSC-1 station.
(b) AC filter requirement for AC system of VSC-1 :
In this section, the three phase AC supply currents are analyzed for harmonic content. The AC filter
requirement to maintain the current harmonics well within the permissible limit is discussed.
In the first case considered for simulation studies, the load in AC system-1 and AC system-2 are:
50MW, UPF and 300MW, UPF respectively. The simulation results are shown in Fig 11(a). It is found from FFT
analysis that, the Total Harmonic Distortion (THD) level is around 12.71%, with predominant harmonics of 5th
and 7th order as shown in Fig. 11(b). In order to reduce these harmonic components, a double tuned filter for 5th
11. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 28 | Page
and 7th
harmonics along with single tuned filter for 27th
and 54th
harmonic is used. The improved current
waveform and the corresponding FFT analysis are shown in Fig. 11 (c) and 11(d) respectively.
Fig. 11(a) Three phase supply ac currents for UPF load without filters Fig. 11(b) FFT analysis of the current
Fig 11(c). Improved three phase supply ac currents for UPF load with filters
Fig. 11(d). FFT analysis of improved current
As it can be observed from Fig. 11(d), the THD in the supply current is reduced to 2.12%, which is well
within the permissible limit. In the second case, the load in AC system-1 and AC system-2 are changed to
inductive load of 50MW, 0.9 pf and 300MW, 0.85 pf respectively. For this case also, it is observed from the
result obtained that, the predominant harmonics are 5th and 7th order leading to a THD of 13.21%. To reduce
these harmonic contents, a double tuned filter for 5th
and 7th
harmonics along with single tuned filter for 27th
and
54th
harmonic are used. It was found that, the THD value is improved to 0.61%.
(c ) DC voltage and AC voltage controllability
This set of simulations was carried out to assess the performance of DC voltage and AC voltage
controllers implemented in VSC-2 station. For the DC voltage controller, the reference DC voltage is set to
300V, which is the rated DC link voltage. Fig. 13(a) and Fig. 13(b) show the waveforms of the controllers of
VSC-2 station for UPF and inductive load respectively. The DC voltage controller waveform shows that, at 0.7
sec, the DC link voltage is subjected to variations due to increase in the load demand at AC system-2. The link
voltage is able to settle back to the reference voltage in 0.05 sec for UPF load and approximately in 0.025 sec
for inductive load respectively. These results show that, the DC controller responds fast for load change in AC
system-2.
In the AC voltage controller, the reference AC voltage is set to peak value of the phase voltage on Δ
side of converter transformer. The AC voltage controller is able to bring the AC voltage at the inverter output of
the DC link to the reference value in about 0.07sec for UPF load as shown in Fig. 13(a) and in approximately
0.05sec for inductive load as shown in Fig. 13(b). The waveforms also show the tracking of the active and
reactive currents (due to action of inner current controller). For any small deviation in the reference current, the
current controller is able to track the reference almost instantaneously. The results show that, the dynamic
response of the AC voltage controller for load change in AC system-2 is good.
12. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 29 | Page
Fig 13(a). VSC-2 controller waveforms for UPF load
Fig 13(b).VSC-2 controller waveforms for inductive load
(d) AC filter requirement for AC system of VSC-2
In this section, the three phase AC supply currents are analyzed for harmonic content. The AC filter
requirement to maintain the current harmonics well within the permissible limit is discussed.
In the first case considered for simulation studies, the chosen load in AC system-1 and AC system-2 are : 50MW,
UPF and 300MW, UPF respectively. The simulation results are shown in Fig. 14(a). It is found from FFT
analysis that, the Total Harmonic Distortion (THD) level is around 21.93%, with predominant harmonics of 3rd
,
5th
and 7th
order as shown in Fig. 14(b). In order to reduce these harmonic components, a double tuned filter for
5th
and 7th
harmonics along with single tuned filter for 3rd
, 27th
and 54th
harmonic are used. The improved current
waveform and the corresponding FFT analysis are shown in Fig. 14(c) and Fig. 14(d) respectively.
13. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 30 | Page
Fig. 14(a) Three phase supply ac currents for UPF load without filters Fig. 14(b) FFT analysis of the current
Fig. 14(c). Improved three phase supply ac currents for Fig. 14(d). FFT analysis of improved current with
UPF load filters
As it can be observed from Fig. 14(d), the THD in the supply current has reduced to 2.53%, which is
well within the permissible limit. In the second case, the load in AC system-1 and AC system-2 are changed to
inductive load of 50MW, 0.9 pf and 300MW, 0.85 pf respectively. For this case also, it is observed from the
result obtained that, the supply current has harmonics, leading to a THD of 8.38%. To reduce these harmonic
contents, a double tuned filter for 5th
and 7th
harmonics along with single tuned filter for 27th
, 54th
harmonic and a
high pass filter are used. It was found that, the THD value is improved to 4.06%.
V. Conclusion
In this paper, the designing of the current and DC voltage controllers using Modulus optimum and
Symmetric optimum techniques respectively are carried out. The controller parameters for the active power,
reactive power and AC voltage controller are tuned based on the settling time for the closed loop step response of
the respective closed loop transfer function. The steady state and dynamic performance of these controllers are
tested for a VSC-HVDC transmission system, that is connected to a weak AC system on the inverter side. The
simulation is carried out for UPF load and inductive load. It is observed from the simulation results that, the
response of the controllers is more smoother and response time for variation in load is less for an inductive load
when compared to that of UPF load. For both types of load considered, AC filters are required to eliminate ac
current harmonics. The performance of the controllers for UPF and inductive load are found to be robust for
changing load conditions in the island system.
Appendix 1
Nomenclature used in section IV
v pcc-1: Three phase voltage at PCC-1. i abc PCC-1: Three phase current at PCC-1.
Pac PCC-1: Active power at PCC-1 Q ac PCC-1: Reactive power at PCC-1.
PL PCC-1: Power supplied to local load at PCC-1 P ac: Active power transmitted in HVDC
link
Qac : Reactive power exchange between DC link and AC network
Pref: Reference active power idref: Reference active current (d
component of iabc)
id:d component of iabc iqref: Reference reactive current (q
component of iabc)
iq : q component of iabc v pcc-2: Three phase voltage at PCC-2.
i abc PCC-2: Three phase current at PCC-2. Pac PCC-2: Active power at PCC-2
Q ac PCC-2 : Reactive power at PCC-2 PL PCC-2 : Power supplied to local load at
PCC-2
P ac_inv: Active power transmitted at the inverter side of VSC- HVDC link
Qac_inv: Reactive power at the inverter side of VSC- HVDC linkVdc: DC link voltage
Vdc ref: Reference DC link voltage vac: ac voltage at the inverter output
vac_ref: Reference ac voltage id_inv: d component of iabc
idref_inv: Reference active current (d component of iabc) iq_inv: q component of iabc
iqref_inv: Reference reactive current (q component of iabc)
14. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 31 | Page
Appendix 2
Base values for per unit system:
Base values for AC side quantities:
Base voltage=Vb=Phase peak voltage
Base active power=Pb
Base current=
b
b
b
V3
P2
I
Base impedance=
b
b
b
I
V
Z
Base nominal frequency= wb=314;
Base capacitance =
bb
b
Z
1
C
Base inductance=
b
b
b
Z
L
Base reactive power=Qb=Reference reactive power (Qref)
Base values for VSC DC side quantities
Base dc power=Pb_dc =Rated DC power
Base dc voltage=2*Vb
Base dc current=
4
I3
I b
dc_b
Base value of DC transmission line resistance=
3
Z8
R b
dc_b
Base value of DC transmission line capacitance=
8
C3
C b
dc_b
Base value of DC transmission line inductance=
3
L8
L b
dc_b
References
[1]. B.Frankén, G.Andersson, “Analysis of HVDC converters connected to weak AC systems”, IEEE Transactions on Power Systems,
vol. 5, No. 1, February 1990.
[2]. Zhang, Lennart Harnefors and Hans-Peter Nee, “Interconnection of Two Very Weak AC Systems by VSC-HVDC Links Using
Power-Synchronization Control”, IEEE Transactions on Power Systems, vol. 26, No. 1, February 2011.
[3]. IEEE Guide for Planning DC Links Terminating at AC Locations having Low Short Circuit Capacities, 1997, IEEE Std. 1204-1997,
Tech. Rep
[4]. A.Gavrilovic, “AC/DC system strength as indicated by short circuit ratios”, in Proc. AC/DC Power Transmission Int. Conf.,
London, U.K., 1991.
[5]. Guanjun Ding, Guangfu Tang, Zhiyuan He, Ming Ding “ New Technologies of Voltage Source Converter (VSC) for HVDC
Transmission System Based on VSC.” Power Engineering Society, IEEE General Meeting - PES , pp. 1-8, 2008
[6]. Li Gengyin, Zhou Ming, He Jie, Li Guangkai, Liang Haifeng “ Power Flow calculation of Power Systems Incorporating VSC-
HVDC”, 2004 International Conference on Power System Technology-POWERCON 2004, Singapore, 21-24 November 2004.
[7]. Ervin Spahic, Gerd Balzer “Offshore Wind Farms – VSC-based HVDC Connection”, in proceeding of: PowerTech 2005, IEEE
Russia, pp.1 - 6
[8]. Chandra Bhajracharya, Marta Molinas, Jon Are Suul, Tore M Undeland, “Understanding of tuning techniques of converter
controllers for VSC-HVDC. NORPIE/2008, Nordic Workshop on Power and Industrial Electronics, June 9-11, 2008
[9]. Nikolas Flourentzou, Vassilios G. Agelidis, Georgios D. Demetriades, “VSC-Based HVDC Power Transmission Systems: An
Overview”, ”, IEEE Transactions on Power Electronics, vol. 24, No. 3, March 2009.
[10]. C.Du, Math H.J. Bollen, “Power frequency control for VSC-HVDC during Island Operation”, in Proc. 8th
Inst.Electr. Eng. Int.
Conf. AC DC Power Transmiss. (ACDC 2006), pp. 177-181.
[11]. H.S.Ramadan, H.Siguerdidjane, M.Petit, R.Kaczmarek, “Performance enhancement and robustness assessment of VSC-HVDC
transmission systems controllers under uncertainties”, Electrical Power and Energy systems 35(2012) 34-46.
[12]. Shuhui Li, Timothy A. Haskew and Ling Xu, “Controlof HVDC Light system using Conventional and Direct Current Vector
Control Approaches”, IEEE Transactions on Power Electronics, vol. 25, No. 12, December 2010.
[13]. Lidong Zhang and Hans-Peter Nee, “Multivariable Feedback Design of VSC-HVDC Connected to Weak AC Systems”, IEEE
Bucharest Power Tech Conference, June 28th
-July 2nd
, BUCHAREST, Romania.
[14]. Lidong Zhang, Lennart Harnefors and Hans-Peter Nee, “Power Synchronization Control of Grid-Connected Voltage-Source
Converters”, IEEE Transactions on Power Eystems, vol. 25, No. 2, May 2010. Lidong Zhang, Lennart Harnefors, Hans-Peter Nee,
“Modeling and Control of VSC-HVDC Links Connected to Island Systems”,IEEE Trans. Power Systems, vol.26, No.2, May 2011.
15. Controllers for a VSC-HVDC link connected to a weak AC system
DOI: 10.9790/1676-10121832 www.iosrjournals.org 32 | Page
[15]. Akshaya Moharana and P.K.Dash, “Input-Output Linearization and Robust Sliding-Mode Controller for the VSC-HVDC
Transmission Link”, IEEE Transactions on Power Delivery,vol. 25,No. 3, July 2010.
[16]. Cuiqing Du,Ambra Sannino, Math H.J.Bollen,”Analysis of the control Algorithms of Voltage –Source Converter HVDC”, Power
Tech, 2005 IEEE Russia, 27-30 June 2005,pp.1 – 7.
[17]. Heifeng Liang,Gengyin Li, Guangkai Li,Peng Li and Ming Yin,”Analysis and design of H∞ controller in VSC-HVDC Systems
“,Transmission and Distribution Conference and Exhibition: Asia and Pacific, 2005 IEEE/PES, pp.1 – 6.
[18]. Ruihua,Song Chao, Zheng Ruomei, Li Xiaoxin, Zhou , “VSCs based HVDC and its control strategy”, Transmission and
Distribution Conference and Exhibition: Asia and Pacific, 2005 IEEE/PES, pp.1-6.
[19]. Â. J. J. Rezek, C. A. D. Coelho, J. M. E. Vicente, J. A. Cortez, P. R. Laurentino, “The Modulus Optimum (MO) Method Applied to
Voltage Regulation Systems: Modeling, Tuning and Implementation”, Proc. International Conference on Power System Transients,
IPST’01, 24-28 June 2001, Rio de Janeiro, Brazil.
[20]. O. Aydin, A. Akdag, P. Stefanutti, N. Hugo, “Optimum Controller Design for a Multilevel AC-DC Converter System”, Proc. Of
Twentieth Annual IEEE
Applied Power Electronics Conference and Exposition, APEC 2005, 6-10 March 2005, Vol. 3, pp. 1660-1666
[21]. “Voltage Sourced Converters in Power systems Modeling, Control and applications”,Amirsen Yazdani, Reza Iravani, Wiley, IEEE
press.
[22]. S. Preitl, R.-E. Precup, “An Extension of Tuning Relations after symmetrical Optimum Method for PI and PID Controllers”,
Automatica, Vol. 35, 1999, pp 1731-1736.
[23]. M. Machaba, M. Braae, “Explicit Damping Factor Specification in Symmetrical Optimum Tuning of PI Controllers”, Proc. of First
African Control Conference, (accessed online) www.nt.ntnu.no/users/skoge/prost/proceedings/afcon03/Papers/050