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The document summarizes a research paper that proposes a new topology for a DSTATCOM (Distribution Static Compensator) to improve power quality in three-phase four-wire distribution systems. The proposed topology integrates a three-leg voltage source converter with a T-connected transformer. This helps mitigate neutral current and allows the DSTATCOM to compensate for load harmonics, reactive power, and imbalance. The design and control strategy of the DSTATCOM are described. Its performance is validated using MATLAB simulation for applications like power factor correction and voltage regulation along with neutral current compensation and harmonic reduction with nonlinear loads.
Comparison of Three leg and Four Leg VSC DSTATCOM for Power Quality AssessmentIOSR Journals
This document compares the performance of three-leg and four-leg voltage source converter (VSC) based distribution static compensators (DSTATCOMs) for power quality improvement in three-phase four-wire distribution systems. It describes the control algorithms and modeling of both the three-leg VSC with a star/delta transformer and the four-leg VSC DSTATCOM topologies. Simulations of both systems are performed in MATLAB/Simulink under different load conditions to regulate voltage and correct power factor. The results demonstrate that the three-leg VSC with a star/delta transformer can compensate reactive power and mitigate neutral currents effectively at a lower cost compared to the four-leg VSC DSTATCOM topology.
A Novel Hybrid Dstatcom Topology for Load Compensation with Non-Stiff SourceIJERA Editor
The distribution static compensator (DSTATCOM) is a shunt active filter, which injects currents into the point
of common coupling (PCC) (the common point where load, source, and DSTATCOM are connected) such that
the harmonic filtering, power factor correction, and load balancing can be achieved. The distribution static
compensator (DSTATCOM) is used for load compensation in power distribution network. A new topology for
DSTATCOM applications with non-stiff source is proposed. The proposed topology enables DSTATCOM to
have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor
along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the
average switching frequency of the insulated gate bipolar transistor switches of the D-STATCOM is also
reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and
shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out
using MATLAB environment and the results analyzed.
The document presents a simple algorithm for distribution system load flow analysis that can accommodate distributed generation. It begins by outlining the objectives, motivation and special features of distribution networks that require modified load flow analysis. It then describes the proposed forward-backward sweep method and models for loads and distributed generation. The algorithm is tested on three test systems and results show reductions in losses and improved voltage profiles with distributed generation integrated using the proposed method and models.
Power systems can be modeled and analyzed using per-unit representations of components. Key models include:
1) Generator models that specify real and reactive power injection or terminal voltage and current.
2) Transformer models using an equivalent circuit with magnetizing reactance and resistance.
3) Load models like constant impedance, current, or power to represent different load characteristics.
4) Transmission lines modeled as series impedances.
The per-unit system allows analysis of different voltage levels on a common scale and simplifies modeling of components.
Power System Simulation Laboratory Manual Santhosh Kumar
This document outlines experiments related to power system simulation laboratory. It includes 10 experiments covering topics like computation of transmission line parameters, modeling of transmission lines, formation of bus admittance and impedance matrices, load flow analysis using different methods, fault analysis, stability analysis of single machine and multimachine systems, electromagnetic transients, load-frequency dynamics, and economic dispatch. The document provides theoretical background and procedures for conducting each experiment using MATLAB software. Sample problems are also included for some experiments to demonstrate the modeling and simulation of different power system components and analysis.
The document discusses load flow studies in power systems. Load flow analysis is important for planning future expansion and determining optimal operation of existing power systems. It provides key information like voltage magnitude and phase angle at each bus and real and reactive power flows. Bus classification depends on which quantities are specified - P,Q buses specify real and reactive power, P,V buses specify real power and voltage magnitude, and the slack bus specifies voltage magnitude and phase angle. Nodal admittance matrix formulation and numerical load flow examples are also presented.
Comparison of Three leg and Four Leg VSC DSTATCOM for Power Quality AssessmentIOSR Journals
This document compares the performance of three-leg and four-leg voltage source converter (VSC) based distribution static compensators (DSTATCOMs) for power quality improvement in three-phase four-wire distribution systems. It describes the control algorithms and modeling of both the three-leg VSC with a star/delta transformer and the four-leg VSC DSTATCOM topologies. Simulations of both systems are performed in MATLAB/Simulink under different load conditions to regulate voltage and correct power factor. The results demonstrate that the three-leg VSC with a star/delta transformer can compensate reactive power and mitigate neutral currents effectively at a lower cost compared to the four-leg VSC DSTATCOM topology.
A Novel Hybrid Dstatcom Topology for Load Compensation with Non-Stiff SourceIJERA Editor
The distribution static compensator (DSTATCOM) is a shunt active filter, which injects currents into the point
of common coupling (PCC) (the common point where load, source, and DSTATCOM are connected) such that
the harmonic filtering, power factor correction, and load balancing can be achieved. The distribution static
compensator (DSTATCOM) is used for load compensation in power distribution network. A new topology for
DSTATCOM applications with non-stiff source is proposed. The proposed topology enables DSTATCOM to
have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor
along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the
average switching frequency of the insulated gate bipolar transistor switches of the D-STATCOM is also
reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and
shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out
using MATLAB environment and the results analyzed.
The document presents a simple algorithm for distribution system load flow analysis that can accommodate distributed generation. It begins by outlining the objectives, motivation and special features of distribution networks that require modified load flow analysis. It then describes the proposed forward-backward sweep method and models for loads and distributed generation. The algorithm is tested on three test systems and results show reductions in losses and improved voltage profiles with distributed generation integrated using the proposed method and models.
Power systems can be modeled and analyzed using per-unit representations of components. Key models include:
1) Generator models that specify real and reactive power injection or terminal voltage and current.
2) Transformer models using an equivalent circuit with magnetizing reactance and resistance.
3) Load models like constant impedance, current, or power to represent different load characteristics.
4) Transmission lines modeled as series impedances.
The per-unit system allows analysis of different voltage levels on a common scale and simplifies modeling of components.
Power System Simulation Laboratory Manual Santhosh Kumar
This document outlines experiments related to power system simulation laboratory. It includes 10 experiments covering topics like computation of transmission line parameters, modeling of transmission lines, formation of bus admittance and impedance matrices, load flow analysis using different methods, fault analysis, stability analysis of single machine and multimachine systems, electromagnetic transients, load-frequency dynamics, and economic dispatch. The document provides theoretical background and procedures for conducting each experiment using MATLAB software. Sample problems are also included for some experiments to demonstrate the modeling and simulation of different power system components and analysis.
The document discusses load flow studies in power systems. Load flow analysis is important for planning future expansion and determining optimal operation of existing power systems. It provides key information like voltage magnitude and phase angle at each bus and real and reactive power flows. Bus classification depends on which quantities are specified - P,Q buses specify real and reactive power, P,V buses specify real power and voltage magnitude, and the slack bus specifies voltage magnitude and phase angle. Nodal admittance matrix formulation and numerical load flow examples are also presented.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
The document discusses power flow analysis, which determines the voltage, current, real power, and reactive power at points in an electrical network under normal operating conditions. It provides three key points:
1. Power flow analysis is important for planning, operations, and future expansion of power systems by studying the effects of new loads, generators, or transmission lines.
2. The analysis involves classifying buses as slack, generator, or load buses and formulating the network equations based on the bus admittance matrix.
3. Solving the load flow problem involves determining the complex voltages across all buses given the network configuration and bus demands. This provides critical information for monitoring overloads and voltage deviations.
Improved dynamic response of dstatcom using genetic algorithmAlexander Decker
This document describes the configuration and control of a DSTATCOM (distributed static compensator) using genetic algorithms. A DSTATCOM consists of a voltage source inverter connected to a distribution network via a transformer to regulate voltage and compensate for reactive power. The performance depends on regulating the DC capacitor voltage. Typically a PI controller is used but it does not perfectly regulate the capacitor voltage. This paper applies a genetic algorithm to optimize the PI controller gains in order to improve the dynamic response by reducing disturbances in the DC voltage. The optimized PI coefficients are implemented in the controller and simulations show improved convergence speed and reduction in errors and overshoot.
Engineering Research Publication
Best International Journals, High Impact Journals,
International Journal of Engineering & Technical Research
ISSN : 2321-0869 (O) 2454-4698 (P)
www.erpublication.org
This document provides an overview and summary of different load flow analysis methods. It begins with an introduction to load flow studies and the power flow equations. It then summarizes three classical iterative methods: Gauss-Seidel, Newton-Raphson, and Fast Decoupled. The document also briefly discusses other optimization methods like fuzzy logic, genetic algorithms, and particle swarm optimization that can be applied to load flow problems. Case studies are presented at the end to demonstrate the different techniques.
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
The document discusses power flow analysis, which determines bus voltages and power flows in a power system under normal steady-state operating conditions. It provides the mathematical formulation of the power flow problem as a set of nonlinear algebraic equations that must be solved iteratively. Buses are classified as slack, generator, or load buses depending on which two of four associated quantities - real power, reactive power, voltage magnitude, and voltage angle - are specified versus solved for. Solution methods like the Gauss-Seidel method are commonly used to iteratively solve the power flow equations until bus voltages converge.
This document discusses the development and structure of the Swedish power system. It began with hydroelectric power stations and later added coal and nuclear power plants. A 220-400kV transmission system was developed to transmit power from northern hydroelectric sources to industrial areas in the south and middle of Sweden. Today the system includes high voltage transmission lines, transformers and substations connecting large centralized power plants ranging from 1000MW to individual consumer needs of kW. The main sources of electricity in Sweden are now hydroelectric, nuclear and some combined heat and power, with hydro and nuclear providing most generation.
This document provides a summary of key concepts from Chapter 2 on AC circuits. It discusses instantaneous, average, and active power calculations. It defines reactive power as the oscillating component of instantaneous power. It examines power calculations for resistive, inductive, and capacitive circuits. Power triangles and complex power are introduced. Power factor correction methods are described. Complex power flow between buses is discussed. Key concepts for three-phase circuits like phase sequence, line voltages, and per-phase analysis are covered. Formulas are provided for calculating real, reactive, and complex power in balanced three-phase systems.
A Novel Control Strategy of Indirect Matrix Converter Using Space Vector Modu...IJPEDS-IAES
This document presents a novel control strategy for an indirect matrix converter using space vector modulation. The control strategy aims to stabilize frequency variations. It was implemented in MATLAB/Simulink and showed better performance than conventional techniques with lower THD, higher output voltage at the same modulation index, lower switching stress and losses. The complete control strategy including DC link formation, commutation scheme, dwell time calculation and simulation results validating the theoretical analysis are described in the document.
This document summarizes key concepts about three-phase systems. It defines a three-phase system as having three sinusoidal voltages differing in phase by 120 degrees. The voltages can form a positive or negative sequence. Three-phase systems are commonly used for power generation, transmission, and distribution due to their ability to transmit more power with less material. Formulas are provided for calculating line voltages, currents, and power in balanced and unbalanced three-phase systems. Advantages of three-phase systems like constant torque and easier starting of motors are also discussed.
Load flow studies analyze the steady state operation of a power system by determining voltage magnitudes and angles, as well as active and reactive power flows. The key purposes of load flow analysis include designing, planning, and optimizing the operation of a power system. The analysis models each bus in the system where generators, transmission lines, and loads connect. Buses are classified based on which two of four parameters - voltage magnitude, voltage angle, active power, and reactive power - are specified as inputs. Load flow equations are then solved to calculate the unknown parameters.
Power Flow Analysis using Power World SimulatorUmair Shahzad
The importance of power flow analysis cannot be overrated. In the scope of Electrical Power Engineering, it is very vital for the utility as well as the consumer to know about several electrical quantities including voltages and power flows regarding power systems. This paper successfully uses Power World Simulator software to carry out load flow analysis on a typical large power system. The results can be used to apply on a much more complex system consisting of several loads and variety of power generation sources including synchronous and induction generators.
The document discusses load flow analysis using the Newton-Raphson method. It provides background on load flow analysis and its importance. It describes classifying buses, constructing the bus admittance matrix, and developing the power flow equations. The Newton-Raphson method is presented as the preferred technique due to its powerful convergence, low computing time, and flexibility. Key steps include initializing bus voltages, calculating mismatches, and iterating to reduce mismatches.
The document discusses power flow analysis, which determines voltages, currents, real power, and reactive power in a power system under steady-state load conditions. It describes the different types of buses in a power system and how they are modeled. The key component of power flow is the bus admittance matrix, which relates nodal voltages to branch currents based on Kirchhoff's current law. Solving the matrix equations provides the voltage magnitude and angle at each bus.
1. The document describes the process of load flow analysis using the Newton-Raphson power flow method.
2. The Newton-Raphson power flow method uses Newton's method to solve the nonlinear power balance equations to determine the voltage magnitude and angle at each bus in the power system.
3. It derives the real and reactive power balance equations, defines the power flow variables, describes calculating the Jacobian matrix and its elements, and provides an example of applying the method to a two bus system to solve for the unknown voltage magnitude and angle at the second bus.
This document summarizes a study on modelling and automating a Controllable Network Transformer (CNT). The CNT augments an existing load tap-changing transformer with an AC chopper to control voltage magnitude and phase angle. The study models the CNT using MATLAB and automates its response to system voltage variations. Simulation results demonstrate the CNT's ability to dynamically control output voltage between taps by varying the chopper's pulse width. An automatic tap and pulse selector subsystem chooses the appropriate tap and pulse width based on the required voltage. The automated CNT model proves CNT is a valuable solution for future grid network links by providing flexible voltage matching and bidirectional power flow control.
Basics of Power systems
Network topology
Transmission and Distribution
Load and Resource Balance
Economic Dispatch
Steady State System Analysis
Power flow analysis
Dynamic System Analysis
Transient stability
This document summarizes previous research on the deformation of endodontic obturator tips using finite element modeling (FEM). It discusses how FEM has been used to analyze stress distributions and deformation patterns in gutta percha cutter tips when subjected to thermal and mechanical loads. The document reviews literature on using tools like ANSYS to model different tip geometries and materials. It also discusses how FEM can help optimize tip design by predicting failure modes and analyzing stresses under various loading conditions. FEM is presented as an effective tool for analyzing complex dental structures when direct measurement is difficult.
The document compares the low field electron transport properties in compounds of groups III-V semiconductors by solving the Boltzmann equation using an iterative technique. It calculates the temperature and doping dependencies of electron mobility in InP, InAs, GaP and GaAs. The electron mobility decreases with increasing temperature from 100K to 500K for each material due to increased electron-phonon scattering. Electron mobility also increases significantly with higher doping concentration at low temperatures. The iterative results show good agreement with other calculations and experiments. Electron mobility is highest in InAs and lowest in GaP at 300K, due to differences in their effective masses.
This paper presented single DC bus single phase seven level cascaded H-bridge (CHB) inverter for multi-panel photovoltaic grid-connected applications. A single DC bus supplying flyback converters to produce DC link voltages for CHB cells is suggested. A balanced operation of CHB inverter cells is obtained irrespective to power unbalance occurred by individual maximum power point tracking boost converter of photovoltaic (PV) panels due to the non-uniform irradiation and partial shading. A DC bus voltage control system with addition of estimated DC bus ripple voltage to the reference is proposed to eliminate the second order harmonic contained in the feedback voltage of DC bus enabling to design high bandwidth of DC voltage control loop. This produces fast dynamic response, low total harmonic distortion (THD) of grid current and smaller DC bus capacitance. Mathematical modeling of bus voltage control system is presented. PSIM simulation program is used and the simulation results are obtained to validate the proposed control system.
The document discusses power flow analysis, which determines the voltage, current, real power, and reactive power at points in an electrical network under normal operating conditions. It provides three key points:
1. Power flow analysis is important for planning, operations, and future expansion of power systems by studying the effects of new loads, generators, or transmission lines.
2. The analysis involves classifying buses as slack, generator, or load buses and formulating the network equations based on the bus admittance matrix.
3. Solving the load flow problem involves determining the complex voltages across all buses given the network configuration and bus demands. This provides critical information for monitoring overloads and voltage deviations.
Improved dynamic response of dstatcom using genetic algorithmAlexander Decker
This document describes the configuration and control of a DSTATCOM (distributed static compensator) using genetic algorithms. A DSTATCOM consists of a voltage source inverter connected to a distribution network via a transformer to regulate voltage and compensate for reactive power. The performance depends on regulating the DC capacitor voltage. Typically a PI controller is used but it does not perfectly regulate the capacitor voltage. This paper applies a genetic algorithm to optimize the PI controller gains in order to improve the dynamic response by reducing disturbances in the DC voltage. The optimized PI coefficients are implemented in the controller and simulations show improved convergence speed and reduction in errors and overshoot.
Engineering Research Publication
Best International Journals, High Impact Journals,
International Journal of Engineering & Technical Research
ISSN : 2321-0869 (O) 2454-4698 (P)
www.erpublication.org
This document provides an overview and summary of different load flow analysis methods. It begins with an introduction to load flow studies and the power flow equations. It then summarizes three classical iterative methods: Gauss-Seidel, Newton-Raphson, and Fast Decoupled. The document also briefly discusses other optimization methods like fuzzy logic, genetic algorithms, and particle swarm optimization that can be applied to load flow problems. Case studies are presented at the end to demonstrate the different techniques.
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
The document discusses power flow analysis, which determines bus voltages and power flows in a power system under normal steady-state operating conditions. It provides the mathematical formulation of the power flow problem as a set of nonlinear algebraic equations that must be solved iteratively. Buses are classified as slack, generator, or load buses depending on which two of four associated quantities - real power, reactive power, voltage magnitude, and voltage angle - are specified versus solved for. Solution methods like the Gauss-Seidel method are commonly used to iteratively solve the power flow equations until bus voltages converge.
This document discusses the development and structure of the Swedish power system. It began with hydroelectric power stations and later added coal and nuclear power plants. A 220-400kV transmission system was developed to transmit power from northern hydroelectric sources to industrial areas in the south and middle of Sweden. Today the system includes high voltage transmission lines, transformers and substations connecting large centralized power plants ranging from 1000MW to individual consumer needs of kW. The main sources of electricity in Sweden are now hydroelectric, nuclear and some combined heat and power, with hydro and nuclear providing most generation.
This document provides a summary of key concepts from Chapter 2 on AC circuits. It discusses instantaneous, average, and active power calculations. It defines reactive power as the oscillating component of instantaneous power. It examines power calculations for resistive, inductive, and capacitive circuits. Power triangles and complex power are introduced. Power factor correction methods are described. Complex power flow between buses is discussed. Key concepts for three-phase circuits like phase sequence, line voltages, and per-phase analysis are covered. Formulas are provided for calculating real, reactive, and complex power in balanced three-phase systems.
A Novel Control Strategy of Indirect Matrix Converter Using Space Vector Modu...IJPEDS-IAES
This document presents a novel control strategy for an indirect matrix converter using space vector modulation. The control strategy aims to stabilize frequency variations. It was implemented in MATLAB/Simulink and showed better performance than conventional techniques with lower THD, higher output voltage at the same modulation index, lower switching stress and losses. The complete control strategy including DC link formation, commutation scheme, dwell time calculation and simulation results validating the theoretical analysis are described in the document.
This document summarizes key concepts about three-phase systems. It defines a three-phase system as having three sinusoidal voltages differing in phase by 120 degrees. The voltages can form a positive or negative sequence. Three-phase systems are commonly used for power generation, transmission, and distribution due to their ability to transmit more power with less material. Formulas are provided for calculating line voltages, currents, and power in balanced and unbalanced three-phase systems. Advantages of three-phase systems like constant torque and easier starting of motors are also discussed.
Load flow studies analyze the steady state operation of a power system by determining voltage magnitudes and angles, as well as active and reactive power flows. The key purposes of load flow analysis include designing, planning, and optimizing the operation of a power system. The analysis models each bus in the system where generators, transmission lines, and loads connect. Buses are classified based on which two of four parameters - voltage magnitude, voltage angle, active power, and reactive power - are specified as inputs. Load flow equations are then solved to calculate the unknown parameters.
Power Flow Analysis using Power World SimulatorUmair Shahzad
The importance of power flow analysis cannot be overrated. In the scope of Electrical Power Engineering, it is very vital for the utility as well as the consumer to know about several electrical quantities including voltages and power flows regarding power systems. This paper successfully uses Power World Simulator software to carry out load flow analysis on a typical large power system. The results can be used to apply on a much more complex system consisting of several loads and variety of power generation sources including synchronous and induction generators.
The document discusses load flow analysis using the Newton-Raphson method. It provides background on load flow analysis and its importance. It describes classifying buses, constructing the bus admittance matrix, and developing the power flow equations. The Newton-Raphson method is presented as the preferred technique due to its powerful convergence, low computing time, and flexibility. Key steps include initializing bus voltages, calculating mismatches, and iterating to reduce mismatches.
The document discusses power flow analysis, which determines voltages, currents, real power, and reactive power in a power system under steady-state load conditions. It describes the different types of buses in a power system and how they are modeled. The key component of power flow is the bus admittance matrix, which relates nodal voltages to branch currents based on Kirchhoff's current law. Solving the matrix equations provides the voltage magnitude and angle at each bus.
1. The document describes the process of load flow analysis using the Newton-Raphson power flow method.
2. The Newton-Raphson power flow method uses Newton's method to solve the nonlinear power balance equations to determine the voltage magnitude and angle at each bus in the power system.
3. It derives the real and reactive power balance equations, defines the power flow variables, describes calculating the Jacobian matrix and its elements, and provides an example of applying the method to a two bus system to solve for the unknown voltage magnitude and angle at the second bus.
This document summarizes a study on modelling and automating a Controllable Network Transformer (CNT). The CNT augments an existing load tap-changing transformer with an AC chopper to control voltage magnitude and phase angle. The study models the CNT using MATLAB and automates its response to system voltage variations. Simulation results demonstrate the CNT's ability to dynamically control output voltage between taps by varying the chopper's pulse width. An automatic tap and pulse selector subsystem chooses the appropriate tap and pulse width based on the required voltage. The automated CNT model proves CNT is a valuable solution for future grid network links by providing flexible voltage matching and bidirectional power flow control.
Basics of Power systems
Network topology
Transmission and Distribution
Load and Resource Balance
Economic Dispatch
Steady State System Analysis
Power flow analysis
Dynamic System Analysis
Transient stability
This document summarizes previous research on the deformation of endodontic obturator tips using finite element modeling (FEM). It discusses how FEM has been used to analyze stress distributions and deformation patterns in gutta percha cutter tips when subjected to thermal and mechanical loads. The document reviews literature on using tools like ANSYS to model different tip geometries and materials. It also discusses how FEM can help optimize tip design by predicting failure modes and analyzing stresses under various loading conditions. FEM is presented as an effective tool for analyzing complex dental structures when direct measurement is difficult.
The document compares the low field electron transport properties in compounds of groups III-V semiconductors by solving the Boltzmann equation using an iterative technique. It calculates the temperature and doping dependencies of electron mobility in InP, InAs, GaP and GaAs. The electron mobility decreases with increasing temperature from 100K to 500K for each material due to increased electron-phonon scattering. Electron mobility also increases significantly with higher doping concentration at low temperatures. The iterative results show good agreement with other calculations and experiments. Electron mobility is highest in InAs and lowest in GaP at 300K, due to differences in their effective masses.
This document summarizes a research paper that proposes using a particle swarm optimization (PSO) algorithm to design hybrid active power filters (HAPFs) for 3-phase 4-wire power systems with variable and nonlinear loads. The objectives are to minimize harmonic distortion, reactive power capacity, and costs while satisfying constraints. PSO is applied to find optimal filter parameters and component ratings. Simulation results show PSO designs outperform conventional trial-and-error methods in meeting standards for harmonic mitigation and power factor correction.
This document discusses methods for interpolating rainfall data using modified inverse distance weighting (MIDW) techniques. It examines four general forms of the MIDW method where the effects of distance and elevation difference can take positive or negative weights. The authors apply genetic algorithms to optimize the MIDW interpolation equation regionally and compare integrated vs. separated dimensionless weighting approaches. Daily rainfall data from 49 stations in the Mashhad plain catchment area of Iran over 16 years is analyzed. The results show that accounting for elevation improves interpolation and that regional optimization of the MIDW method leads to better performance than local optimization.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
This document presents a comparison of PID and fuzzy PID controllers for position control of a DC motor. It first describes the modeling of a DC motor transfer function. It then provides details on designing a PID controller using Ziegler-Nichols tuning methods. A fuzzy PID controller is also designed using triangular membership functions for error and change in error inputs. Simulation results in MATLAB/Simulink show that the fuzzy PID controller provides better tracking of setpoint changes with less overshoot compared to the ZN-tuned PID controller. The fuzzy PID controller therefore demonstrates better performance for position control of DC motors.
This document presents a framework for optimizing transportation costs when supplying resources to construction sites. It identifies renewable and non-renewable resources and considers the locations of storage facilities and construction sites. The objective is to minimize total transportation costs by determining optimal quantities to ship from each storage location to each site. A mathematical model is formulated to represent the transportation costs as a function of shipping quantities between sources and sinks, subject to supply and demand constraints. The model aims to develop a tradeoff between transportation costs and transshipment quantities for efficiently supplying resources in construction projects.
This document summarizes a research paper that proposes a fuzzy self-adaptive PID controller for temperature control of an electric heating furnace. It begins with an introduction to electric furnaces and challenges with using conventional PID controllers for nonlinear and time-varying temperature processes. It then describes tuning various PID controller gains using algorithms and comparing responses. Next, it designs a fuzzy logic controller and fuzzy-PID controller for the system using MATLAB/Simulink. Membership functions and fuzzy rules are defined for the fuzzy inference systems. The results show that the proposed fuzzy self-adaptive PID controller provides the best dynamic performance for temperature control of the electric furnace.
This document summarizes a research paper that proposes using the firefly algorithm to solve the NP-hard optimization problem of assigning cells in a cellular network to switches in a way that minimizes total costs. The total cost includes handoff costs for calls between adjacent cells and cabling costs for connecting cells to switches, subject to constraints like switch capacity. It describes modeling the problem mathematically and comparing the firefly algorithm to the particle swarm optimization (PSO) algorithm. The firefly algorithm is shown to solve the cell-to-switch assignment problem faster than existing approaches like PSO.
This document discusses implementing trust in cloud computing using public key infrastructure (PKI). It begins by providing background on PKI and how it uses public/private key cryptography to provide security services like authentication, confidentiality, and integrity. It then discusses cloud computing models and the Windows Azure platform. The paper proposes three trust models using PKI: 1) a public root CA and public CA, 2) a public root CA and enterprise CA, and 3) an enterprise root CA and enterprise CA. It details methodologies for implementing each model to establish trust between cloud services and customers. The enterprise root CA model provides the most security and trust but has higher costs and complexity.
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Similar to call for papers, research paper publishing, where to publish research paper, journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJEI, call for papers 2012,journal of science and technolog
The document provides information about a PowerPoint presentation on Distributed Static Compensator (D-STATCOM) given by Sheikh Mohammad Sajid. It introduces D-STATCOM as a device used to mitigate current-based power quality problems at the distributed level. It discusses various classifications, topologies, components, control strategies and objectives of D-STATCOM, including reactive power compensation, load balancing and harmonic suppression. The key principles of operation involve injecting compensating currents from a voltage source converter to regulate voltage at the point of common coupling.
Voltage Sag Mitigation in Utility Connected System Using Current Source Conve...IDES Editor
This paper discusses the implementation of current
source converter based distribution type static synchronous
compensator. For eliminating the lower order harmonics, the
power semiconductors are switched by pulse width modulation
technique. Current source converter, input filter, dc link
reactor are combined to design the proposed CSC based
STATCOM. Since the STATCOM is a current injection
device, the performance of the device is improved by a currentsource
converter (CSC) combination. So a controllable current
is generated at the output terminals of the device. Filter circuit
at the input terminal is designed to eliminate the higher order
harmonics. The proposed D- STATCOM is simulated and the
results are validated using MATLAB.
IRJET- Analysis of Open Loop Distribution Static Compensator for Improvin...IRJET Journal
This document discusses the analysis and simulation of an open loop distribution static compensator (D-STATCOM) for improving power quality in a distribution system. Key points:
1. A D-STATCOM model is developed in MATLAB Simulink to compensate for reactive power demand from nonlinear and unbalanced loads, improve source power factor, and reduce total harmonic distortion in source currents.
2. Simulation results show that before compensation, source currents are unbalanced and distorted due to nonlinear loads. The D-STATCOM is able to maintain unity power factor at the source and mitigate harmonics after compensation.
3. Operating modes of the D-STATCOM include reactive power compensation to regulate voltage, and active power compensation
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.
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.
Distribution Static Synchronous Compensator (DSTATCOM) is a shunt compensating device which is used
to improve current profile by exchanging of reactive power with unbalanced and nonlinear load. DSTATCOM is a
shunt compensating device used for power quality improvement in distribution systems. Relevant solutions are
applied for harmonics, fluctuation of voltage, voltage deviation, unbalance of three phase voltage and current and
frequency deviation. Different controlling schemes such as Phase Control Method (PCM), Fryze Power Theory
(FPT), Synchronous Reference Frame Theory (SRFT) and Instantaneous Reactive Power Theory (IRPT) are used
for reactive power compensation with the help of Voltage source Inverter (VSI). In this project we are going to
balance the source current using different control schemes. The results of different source currents are compared
with a different control schemes in terms of active and reactive power and in terms of Total Harmonic Distortion
(THD) for nonlinear load using Fryze Power Theory (FPT) and Instantaneous Reactive Power Theory (IRPT).
Reference currents are generated by the different control schemes have been dynamically traced in a hysteresis
current controller. The performance of DSTATCOM for different control schemes is validated for load balancing
and harmonic elimination by using simulation models in MATLAB/SIMULINK
Power Quality Improvement Using Cascaded H-Bridge Multilevel Inverter Based D...IJERA Editor
Cascaded multilevel configuration of the inverter has the advantage of its simplicity and modularity over the
configurations of the diode-clamped and flying capacitor multilevel inverters. This paper presents a threephase,
five-level and seven level cascaded multilevel voltage source inverter based active filter for power line
conditioning to improve power quality in the distribution network. The DSTATCOM helps to improve the
power factor and eliminate the Total Harmonics Distortion (THD) drawn from a Non-Liner Diode Rectifier
Load (NLDRL). The compensation process is based on concept of p-q theory. A CHB Inverter is considered for
shunt compensation of a 11 kV distribution system. Finally a level shifted PWM (LSPWM) and phase shifted
PWM (PSPWM) techniques are adopted to investigate the performance of CHB Inverter. The results are
obtained through Matlab/Simulink software package.
IJERD(www.ijerd.com)International Journal of Engineering Research and Develop...IJERD Editor
1) The document describes modeling and simulation of a DSTATCOM (distribution static synchronous compensator) to improve power quality in a distribution system feeding both linear and non-linear loads.
2) A MATLAB/Simulink model of a DSTATCOM power circuit and control system is developed. Simulation results under different load conditions are presented to demonstrate the DSTATCOM's ability to provide power factor correction, harmonic compensation, and reactive power support.
3) Key findings include that the DSTATCOM can balance unbalanced loads, improve the source power factor to unity, and regulate voltages under transient conditions like load changes within one cycle.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
IRJET - Review Paper on RSC-MLC Base Smart PV-DSTATCOM for Multi Objective Pu...IRJET Journal
This document summarizes research on using a Real Switch Count Multi-Level Converter (RSC-MLC) based smart PV-DSTATCOM for multiple objectives including improving power quality, compensating reactive power flow, and optimizing the DC link voltage. A DSTATCOM uses a voltage source converter to inject current and control reactive power flow. The proposed method uses an RSC-MLC to regulate the DC link voltage from a PV source, reducing voltage stress on switches and minimizing losses. It can supply solar power to loads and compensate reactive power with battery support when solar power is unavailable. The document reviews related work on DSTATCOM control and applications and provides details on controlling the proposed RSC-MLC based PV-
Real and Reactive Power Compensation by using Diode Clamped Multilevel Invert...IRJET Journal
This document discusses using a diode-clamped multilevel inverter based STATCOM to provide both real and reactive power compensation on a transmission line. A STATCOM is a shunt connected device that can regulate voltage and provide reactive power support. A diode-clamped multilevel inverter is proposed for the STATCOM due to its ability to generate stepped voltage waveforms with lower harmonic distortion compared to a two-level inverter. Simulation results using MATLAB/Simulink show that the multilevel inverter based STATCOM can effectively regulate the voltage and maintain stability of the load while supplying real and reactive power to the transmission line.
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.
Indraneel perfect paper on dstatcom using pq theoryindranilsaaki
This document summarizes a research paper about modeling and simulation of a three phase-four wire distribution static compensator (DSTATCOM) system using an H-bridge voltage source inverter (VSI) topology. The DSTATCOM is used to compensate unbalanced and nonlinear loads by injecting current. Maintaining the DC link voltage is important for proper operation but conventional PI controllers have slow transient response. The paper proposes a faster acting DC link voltage controller based on the energy of the DC link capacitor. It also provides equations to design gains for a conventional PI controller to achieve similar fast transient response. Detailed simulation studies are presented to validate the proposed controller.
Design modelling and Simulation of DSTATCOM for distribution lines for power ...CHRAMIREDDY2
This document discusses the design, modeling, and simulation of a DSTATCOM (distribution static synchronous compensator) to improve power quality on distribution lines. It presents a study on modeling a STATCOM used for reactive power compensation. A three-phase IGBT-based voltage source inverter known as a DSTATCOM is used for power factor correction, harmonic compensation, and providing reactive power to loads. A model of a DSTATCOM connected to a distribution system feeding linear and non-linear loads is developed in MATLAB to analyze system behavior under transient conditions. The performance of the DSTATCOM is investigated under various fault conditions.
This document discusses the design and analysis of a multi-level D-STATCOM to improve power quality. A D-STATCOM is a shunt connected custom power device that can regulate voltage and compensate for reactive power and current harmonics. The paper proposes using a cascaded H-bridge multilevel inverter for the D-STATCOM due to its advantages of low harmonic distortion and reduced switching losses. Simulation results using Matlab/Simulink show that the D-STATCOM is able to regulate the voltage and compensate for reactive power drawn by a non-linear diode rectifier load, improving the power factor and eliminating total harmonic distortion.
1) The document discusses different control strategies for DSTATCOM (distribution static synchronous compensator), including Synchronous Reference Frame (SRF) methods, to mitigate voltage sags and compensate reactive power.
2) It analyzes the SRF method, SRF without phase locked loop (PLL), and a modified SRF method through mathematical modeling and MATLAB simulation.
3) The comparison of results from the different control strategies indicates that SRF provides effective compensation of voltage sags and reactive power under steady state conditions.
The study made in this paper concerns the use of the voltage-oriented control (VOC) of three-phase pulse width modulation (PWM) rectifier with constant switching frequency. This control method, called voltage-oriented controlwith space vector modulation (VOC-SVM). The proposed control scheme has been founded on the transformation between stationary (α-β) and and synchronously rotating (d-q) coordinate system, it is based on two cascaded control loops so that a fast inner loop controls the grid current and an external loop DC-link voltage, while the DC-bus voltage is maintained at the desired level and ansured the unity power factor operation. So, the stable state performance and robustness against the load’s disturbance of PWM rectifiers are boths improved. The proposed scheme has been implemented and simulated in MATLAB/Simulink environment. The control system of the VOC-SVM strategy has been built based on dSPACE system with DS1104 controller board. The results obtained show the validity of the model and its control method. Compared with the conventional SPWM method, the VOC-SVM ensures high performance and fast transient response.
This document presents a comparative study of the effects of GCSC (GTO Controlled Series Capacitor) and TCSC (Thyristor Controlled Series Capacitor) on the impedance seen by MHO distance relays protecting a 400kV transmission line in Algeria. The study investigates how the insertion of GCSC and TCSC at the line midpoint affects the setting of the relay's protection zones to prevent unwanted tripping while maintaining protection performance. Simulation results using MATLAB are presented to analyze the modified protection zone settings for different compensation levels of the FACTS devices.
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call for papers, research paper publishing, where to publish research paper, journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJEI, call for papers 2012,journal of science and technolog
1. International Journal of Engineering Inventions
ISSN: 2278-7461, www.ijeijournal.com
Volume 1, Issue 4 (September2012) PP: 80-90
A Modern Approach of a Three Phase Four Wire Dstatcom for
Power Quality Improvement Using T Connected Transformer
A.Dheepanchakkravarthy.M.E.1, Prof.Jebasalma.M.E.2,
1
Department Of EEE, M.I.E.T Engineering College, Trichy – 07
2
Department Of EEE, A.C. College Of Engineering And Technology, Karaikudi-04
Abstract––Three-phase four-wire distribution systems are facing severe power quality problems such as poor voltage
regulation, high reactive power and harmonics current burden, load unbalancing, excessive neutral current, etc., due to
various reasons such as single phase loads, nonlinear loads etc. A new topology of DSTATCOM [Distribution Static
Compensator] is proposed in this paper in which a three phase three leg VSC [Voltage Source Converter] is Integrated
with T connected transformer for nonlinear loads and is able to perform all the compensation required for three phase
four wire system. The T-connected transformer connection mitigates the neutral current and the three-leg VSC
compensates harmonic current, reactive power, and balances the load. Two single-phase transformers are connected in
T-configuration for interfacing to a three-phase four-wire power distribution system and the required rating of the VSC is
reduced. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current
compensation, harmonic reduction, and balancing of nonlinear loads. The performance of the three-phase four-wire
DSTATCOM is validated using MATLAB software with its Simulink and power system block set toolboxes.
Keywords––Power quality improvement, DSTATCOM, voltage source converter, T connected transformer, neutral
current compensation
I. INTRODUCTION
Three-phase four-wire distribution systems are used in commercial buildings, office buildings, hospitals, etc. Most
of the loads in these locations are nonlinear loads and are mostly unbalanced loads in the distribution system. This creates
excessive neutral current both of fundamental and harmonic frequency and the neutral conductor gets overloaded. The
voltage regulation is also poor in the distribution system due to the unplanned expansion and the installation of different
types of loads in the existing distribution system. The power quality at the distribution system is governed by various
standards such as IEEE-519 standard [1]. The remedies to power quality problems are reported in the literature and are
known by the generic name of custom power devices (CPD) [2]. These custom power devices include the DSTATCOM
(distribution static compensator), DVR (dynamic voltage restorer) and UPQC (unified power quality conditioner). The
DSTATCOM is a shunt connected device, which takes care of the power quality problems in the currents, whereas the DVR
is connected in series with the supply and can mitigate the power quality problems in the voltage and the UPQC can
compensate power quality problems both in the current and voltage.
Some of the topologies of DSTATCOM for three-phase four-wire system for the mitigation of neutral current
along with power quality compensation in the source current are four-leg voltage source converter (VSC), three single-phase
VSCs, three-leg VSC with split capacitors [5], three-leg VSC with zigzag transformer [9],[10], and three-leg VSC with
neutral terminal at the positive or negative of dc bus [11]. The voltage regulation in the distribution feeder is improved by
installing a shunt compensator [12]. There are many control schemes reported in the literature for control of shunt active
compensators such as instantaneous reactive power theory, power balance theory, synchronous reference frame theory,
symmetrical components based, etc. [13], [14]. The synchronous reference frame theory [14] is used for the control of the
proposed DSTATCOM.
The T-connected transformer is used in the three-phase distribution system for different applications [6]–[8].But
the application of T-connected transformer for neutral current compensation is demonstrated for the first time. Moreover, the
T-connected transformer is suitably designed for magneto motive force (mmf) balance. The T-connected transformer
mitigates the neutral current and the three-leg VSC compensates the harmonic current and reactive power, and balances the
load. The IGBT based VSC is self-supported with a dc bus capacitor and is controlled for the required compensation of the
load current. The DSTATCOM is designed and simulated using MATLAB software with its Simulink and power system
block set (PSB) toolboxes for power factor correction and voltage regulation along with neutral current compensation,
harmonic reduction, and load balancing with nonlinear loads.
II. BLOCK DIAGRAM REPRESENTATION
80
2. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Fig. 2.1: Block Diagram Representation
The block diagram representation of the proposed Three-Phase Four-Wire DSTATCOM and T-connected
Transformer based distribution System is as shown in fig 2.1. It consists of three phase linear/nonlinear load block, ripple
filter block, control circuit block and shunt active filter block. The T-connected Transformer block is used for neutral current
compensation and it reduces the rating of three leg voltage source converter. The control circuit consists of DSATATCOM
with Three leg Voltage Source Converter. This block is used to compensate the harmonic current and reactive power and
load balancing. Also The DSTATCOM is tested for power factor correction and voltage regulation. The three leg VSC is
used as an active shunt compensator along with a T-connected transformer. The ripple filter block is used to reduce the high
frequency ripple voltage in the voltage at Point of Common Coupling (PCC). High frequency ripple is due to switching
current of the VSC of the DSTATCOM. All the blocks should be connected at PCC.
III. SYSTEM CONFIGURATION AND DESIGN
Fig.3.1 (a) shows the single-line diagram of the shunt-connected DSTATCOM-based distribution system. The dc
capacitor connected at the dc bus of the converter acts as an energy buffer and establishes a dc voltage for the normal
operation of the DSTATCOM system. The DSTATCOM can be operated for reactive power compensation for power factor
correction or voltage regulation. Fig.3. (b) shows the phasor diagram for the unity power factor operation. The reactive
current (Ic) injected by the DSTATCOM has to cancel the reactive power component of the load current, so that the source
current is reduced to active power component of current only (I S). The voltage regulation operation of DSTATCOM is
depicted in the phasor diagram of Fig. 3.1 (c). The DSTATCOM injects a current Ic such that the voltage at the load (VL) is
equal to the source voltage (VS). The DSTATCOM current are adjusted dynamically under varying load condition.
The proposed DSTATCOM consisting of a three-leg VSC and a T-connected transformer is shown in Fig.3.2,
where the T-connected transformer is responsible for neutral current compensation. The windings of the T-connected
transformer are designed such that the mmf is balanced properly in the transformer. A three-leg VSC is used as an active
shunt compensator along with a T-connected transformer, as shown in Fig. 3.2, and this topology has six IGBTs, and one dc
capacitor. The required compensation to be provided by the DSTATCOM decides the rating of the VSC components. The
data of DSTATCOM system considered for analysis is shown in the Appendix 1. The VSC is designed for compensating a
reactive power of 12 KVAR, as decided from the load details. The ripple filter block is used to reduce the high frequency
ripple voltage in the voltage at Point of Common Coupling (PCC). High frequency ripple is due to switching current of the
VSC of the DSTATCOM. All the blocks are connected at PCC. The selection of dc capacitor and the ripple filter are given
in the following sections.
3.1. DC CAPACITOR VOLTAGE
The minimum dc bus voltage of VSC of DSTATCOM should be greater than twice the peak of the phase voltage
of the system [17]. The dc bus voltage is calculated as
Vdc = 2√2VLL / √3 m (1)
Where m is the modulation index and is considered as 1 and VLL is the ac line output voltage of DSTATCOM. Thus, Vdc is
obtained as 677.69V for VLL of 415 V and is selected as 700V.
81
3. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Fig.3.1. (a) Single-line diagram of DSTATCOM system. (b) Phasor diagram for UPF operation. (c) ZVR operation
Fig.3.2. Schematics of the proposed three-leg VSC with T-connected transformer- based DSTATCOM connected in
distribution system
3.2. DC BUS CAPACITOR
The value of dc capacitor (Cdc) of VSC of DSTATCOM depends on the instantaneous energy available to the
DSTATCOM during transients [17]. The principle of energy conservation is applied as
(1/2) Cdc [(Vdc)2 - (Vdc1)2] = 3V(a I) t (2)
Where Vdc is the reference dc voltage and Vdc1 is the minimum voltage level of dc bus, a is the overloading factor,
V is the phase voltage, I is the phase current, and t is the time by which the dc bus voltage is to be recovered. Considering, a
1.5 %( 10 V) reduction in DC bus voltage during transients, Vdc1 = 690 V, Vdc = 700 V, V = 239.60 V, I = 28.76 A, t = 350
μs, a = 1.2, the calculated value of Cdc is 2600 μF and is selected as 3000 μF.
3.3. RIPPLE FILTER
A low-pass first-order filter tuned at half the switching frequency is used to filter the high-frequency noise from
the voltage at the PCC. Considering a low impedance of 8.1 Ω for the harmonic voltage at a frequency of 5 kHz, the ripple
filter capacitor is designed as Cf = 5 μF. A series resistance (Rf) of 5 Ω is included in series with the capacitor (Cf ). The
82
4. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
impedance is found to be 637 Ω at fundamental frequency, which is sufficiently large, and hence, the ripple filter draws
negligible fundamental current.
IV. DESIGN OF THE T-CONNECTED TRANSFORMER
Fig. 4.1 (a) shows the connection of two single-phase transformers in T-configuration for interfacing with a three-
phase four-wire system. The T-connected windings of the transformer not only provide a path for the zero-sequence
fundamental current and harmonic currents but also offer a path for the neutral current when connected in shunt at point of
common coupling (PCC). Under unbalanced load, the zero-sequence load-neutral current divides equally into three currents
and takes a path through the T-connected windings of the transformer. The current rating of the windings is decided by the
required neutral current compensation. The voltages across each winding are designed as shown shortly.
The phasor diagram shown in Fig. 4.1 (b) gives the following relations to find the turn’s ratio of windings. If Va1
and Vb1 are the voltages across each winding and Va is the resultant voltage,
Then
Va1 = K1Va (3)
Vb1 = K2Va (4)
Where K1 and K2 are the fractions of winding in the phases.
Considering
|Va | = |Vb | = V and
From phasor diagram,
cos 30◦ = Va1 / Va
Va1 = Va cos 30◦
and
sin 30◦ = Vb1 / Va
Vb1 = Va sin 30◦
Fig. 4.1 (a) Design of T-connected transformer (b) Phasor diagram
Then from (4) and (5), one gets, K1 = 0.866 and K2 = 0.5. The line voltage is
Vca = 415 V
Va = Vb = Vc = 415 √3= 239.60 V (5)
Va1 = 207.49 V, Vb1 = 119.80 V (6)
Hence, two single-phase transformers of ratings 5kVA, 240 V/120V/120 V and 5kVA, 208 V/208 V are selected.
V. CONTROL OF DSTATCOM
The control approaches available for the generation of reference source currents for the control of VSC of
DSTATCOM for three-phase four-wire system are instantaneous reactive power theory (IRPT), synchronous reference frame
theory (SRFT), unity power factor (UPF) based, instantaneous symmetrical components based, etc. [13], [14]. The SRFT is
used in this investigation for the control of the DSTATCOM. A block diagram of the control scheme is shown in Fig. 5.1.
The load currents (iLa, iLb, iLc), the PCC voltages (VSa, VSb, VSc), and dc bus voltage (Vdc) of DSTATCOM are sensed as
feedback signals. The load currents from the a–b–c frame are converted to the d–q–o frame using Park’s Transformation
1
cosθ −sinθ
iLd 2 iLa
2 1
iLq = cos θ − 120 − sin θ − 120 iLb (7 )
3 2
iL0 1 iLc
cos θ + 120 sin θ + 120
2
Where cos θ and sin θ are obtained using a three-phase phase locked loop (PLL). A PLL signal is obtained from
terminal voltages for generation of fundamental unit vectors [18] for conversion of sensed currents to the d–q–o reference
frame. The SRF controller extracts dc quantities by a low-pass filter, and hence, the non-dc quantities (harmonics) are
separated from the reference signal. The d-axis and q-axis currents consist of fundamental and harmonic components as
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5. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
iLd = id dc + iq ac (8)
iLq = iq dc + Iq ac (9)
5.1. Unity Power Factor (UPF) operation of DSTATCOM
The control strategy for reactive power compensation for UPF operation considers that the source must deliver the
mean value of the direct-axis component of the load current along with the active power, component current for maintaining
the dc bus and meeting the losses (iloss) in DSTATCOM. The output of the proportional-integral (PI) controller at the dc bus
voltage of DSTATCOM is considered as the current (iloss) for meeting its losses
i loss (n) = i loss (n−1) + K pd (Vde (n) − Vde (n−1)) + K idVde(n) (10)
where Vde(n) = V*dc-Vdc(n) is the error between the reference (V*dc)and sensed (Vdc) dc voltages at the nth sampling
instant. Kpd and Kid are the proportional and integral gains of the dc bus voltage PI controller The reference source current is
therefore
I*d = id dc + iloss (11)
The reference source current must be in phase with the voltage at the PCC but with no zero-sequence component.
It is therefore obtained by the following inverse Park’s transformation with i*d as in and i*q and i*0 as zero.
i∗a cosθ sinθ 1 i∗
d
i∗
b = cos − 120) sin − 120) 1
(θ (θ i∗
q (12)
i∗
c cos + 120) sin + 120) 1
(θ (θ i∗
0
5.2. Zero-Voltage Regulation (ZVR) operation of DSTATCOM:
The compensating strategy for ZVR operation considers that the source must deliver the same direct-axis
component i*d, as mentioned in along with the sum of quadrature-axis current (iq dc) and the component obtained from the PI
controller (iqr ) used for regulating the voltage at PCC. The amplitude of ac terminal voltage (VS) at the PCC is controlled to
its reference voltage (V*S ) using the PI controller. The output of PI controller is considered as the reactive component of
current (iqr) for zero-voltage regulation of ac voltage at PCC. The amplitude of ac voltage (VS) at PCC is calculated from the
ac voltages (vsa, vsb, vsc) as
VS = (2/3)1/2 (v2sa + v2sb + v2sc) ½ (13)
Then, a PI controller is used to regulate this voltage to a reference value as
i qr (n) = i qr (n−1) + Kpq (Vte (n) − Vte (n−1)) + K iq Vte (n) (14)
Where Vte (n) = V*S – VS(n) denotes the error between reference (V*S ) and actual (VS(n)) terminal voltage amplitudes at the nth
sampling instant. Kpq and Kiq are the proportional and integral gains of the dc bus voltage PI controller. The reference source
quadrature-axis current is
I*q = iq dc + iqr (15)
The reference source current is obtained by inverse Park’s transformation using (12) with i*d as in (11) and i*q as in (15) and
i*0 as zero.
Fig.5.1 Control algorithm for the three-leg-VSC-based DSTATCOM in a three phase four-wire system.
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6. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
5.3. Current controlled PWM generator:
In a current controller, the sensed source currents (isa, isb, isc) and reference source currents (i sa*, isb*, isc*) are
compared and a proportional controller is used for amplifying current error in each phase. Then, the amplified current error
is compared with a triangular carrier signal of switching frequency to generate the gating signals for six IGBT switches of
VSC of DSTATCOM. The gate signals are PWM controlled so that sensed source currents follows the reference source
currents precisely.
VI. MODELING AND SIMULATION
The three-leg VSC and the T-connected-transformer-based DSTATCOM connected to a three-phase four-wire
system is modeled and simulated using the MATLAB with its Simulink and PSBs. The ripple filter is connected to the
DSTATCOM for filtering the ripple in the PCC voltage. The system data are given in the Appendix I. The MATLAB-based
model of the three-phase four-wire DSTATCOM is shown in Fig.6.2. The T connected transformer in parallel to the load,
the three-phase source, and the shunt-connected three-leg VSC are connected as shown in Fig. 6.2. The available model of
linear transformers, which includes losses, is used for modeling the T-connected transformer. The control algorithm for the
DSTATCOM is also modeled in MATLAB. The reference source currents are derived from the sensed PCC voltages (vsa,
vsb, vsc), load currents (iLa, iLb, iLc), and the dc bus voltage of DSTATCOM (vdc). A PWM current controller is used over the
reference and sensed source currents to generate the gating signals for the IGBTs of the VSC of the DSTATCOM.
6.1 Simulation diagram of Three-Phase Four-Wire Distribution System without Controller Circuits
It consists of two three phase circuit breakers and Active Reactive power block, Power factor calculation Block
and Display. The circuit Breakers are used to simulate the unbalanced condition. The Source voltage (V s), Source current
(Is), Load current (IL), Load neutral current (ILn), Source neutral current (ISn) are measured from the corresponding scopes as
in shown fig.6.1
6.2. Simulation diagram of the T-connected Transformer and Three leg VSC based DSTATCOM for power quality
improvement
It consists of Three Three-phase Circuit Breakers, Nonlinear load, DSTATCOM block, T-connected transformer,
controller block, Power factor correction, ripple filter and the measurement scopes as shown in fig.6.2. Initially the three-
phase four-wire distribution system is in stable condition (CB1 and CB2 are open), and the controller circuit is not connected
to the balanced three-phase four-wire distribution system. When Circuit breaker1 gets closed at 0.2sec, one phase of the load
is disconnected resulting load become unbalanced. At this junction the circuit breaker3 gets closed thereby connecting the
controller circuit to the three-phase four-wire distribution system. The circuit breaker1 remain closed from 0.2sec to 0.5 sec.
Further at 0.3sec the circuit breaker2 gets closed disconnecting another phase. The circuit breaker 2 remains closed till
0.4sec. During unbalanced condition as a result of fault is rectified by the controller action.
Fig.6.1. Simulation diagram of three-phase four-wire System without controller circuits
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7. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Fig.6.2. Simulation diagram of the proposed three-phase four-wire DSTATCOM-connected system for Non-linear Load
VII. RESULTS
7.1. Performance of three phases four wire distribution system for linear load without controller circuits:
The source voltage (Vs), source current (Is), load current (IL), load neutral current (ILn), source neutral current (ISn)
are measured from the corresponding scopes of fig.6.1. and shown in Fig.7.1. The power factor measured in this condition is
0.5119 as shown in fig. 6.1. The source current (Is) and load current (IL) both contain harmonics. The THD measured is
37.85% with help of FFT analysis. The Source current and harmonic spectrums without controller circuit are also shown in
fig. 7.1.
Source Voltage (Vs)
Source Current (Is)
Source Current (Isa)
Load Current (IL)
Load Neutral Current (ILn)
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8. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Source Neutral Current (ISn)
Source current and Harmonic Spectrum
Fig.7.1. Performance of three phases four wire distribution system for nonlinear load without controller circuits
7.2. Performance of three phases four wire DSTATCOM with Non-Linear load for Harmonic compensation, Load
balancing
The dynamic performance during Non-linear, unbalanced load condition is shown in fig.6.2. At 0.2 sec, the load is
changed to two phase load and single phase load at 0.3 sec. These loads are applied again at 0.4 sec and 0.5 sec respectively.
The PCC voltage (VS), source current (IS), load current (IL), compensator current (IC), source neutral current (ISn), load
neutral current (ILn),and compensator neutral current (ICn), DC bus Voltage of DSTATCOM (VDC), amplitude of voltage
(VAmp) at PCC, reactive Power (Q), active power (P), harmonic spectrum of source current and Filter current are shown in
Fig 7.2.
The source currents are observed as balanced and sinusoidal under all these condition. The harmonic currents are
added with the filter currents so we can get the pure sinusoidal source current with help of DSTATCOM and VSC. The total
Harmonic Distortion (THD) of the source current was improved from 37.85% to 5.52% and this shows the satisfactory
performance of DSTATCOM for harmonic compensation as stipulated by IEEE 519 – standard. The load current and the
compensator current are observed as balanced under all these condition with help of DSTATCOM. The T - connected
transformer is responsible for neutral current compensation. By adding the load neutral current (ILn) with Compensator
neutral current (ICn) as a result source neutral current is equal to zero (ISn = ILn + ICn = 0) and this is used to verify the
proper compensation.
The Reactive power (Q) is compensated for power factor correction with help of DSTATCOM. From the
waveform we can measure the reactive power (Q = 0) value is equal to zero. Here power factor value nearly one (cosΦ = 1).
Here the power factor value was improved from 0.5119 to 0.8040.
Source Voltage (Vs)
Source Current (Is)
Source current (ISa)
Load current (IL)
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9. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Compensator current (Ic)
Load neutral Current (ILn)
Compensator neutral Current (ICn)
Source neutral Current (ISn)
Reactive power (Q) and Active power (P)
Filter current (If)
Amplitude of PCC Voltage (VAmp)
DC bus voltage (VDC)
Source current and Harmonic Spectrum
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10. A Modern Approach of a Three Phase Four Wire Dstatcom for Power…
Fig.7.2. Performance of three phases four wire DSTATCOM for Nonlinear load with controller circuits
7.3. Comparison with other techniques
A three-leg single-phase-VSC-based DSTATCOM [5] requires a total of 12 semiconductor devices, and hence, is
not attractive, and the three-leg VSC with split capacitors [5] has the disadvantage of difficulty in maintaining equal dc
voltage at two series-connected capacitors. The four-leg-VSC-based DSTATCOM [3] is considered as superior considering
the number of switches, complexity, cost, etc. A three-leg VSC with T connected transformer [10] is reported recently and
has shown improved performance. The three-leg VSC with T-connected transformer has the advantage of using a passive
device for neutral current compensation, reduced number of switches, use of readily available three-leg VSC, etc. The
proposed three-phase four-wire DSTATCOM is based on a three-leg VSC and a T-connected transformer. The T connected
transformer requires two single-phase transformers. A star/delta transformer is also reported [19] for neutral current
compensation and the kVA rating required is higher compared to T-connected transformer. Table I shows the rating
comparison of the two transformer techniques for a given neutral current of 10 A. It is observed that the kVA rating of the T-
connected transformer is much less compared to a star/delta transformer. Similarly, comparison with the four-leg converter
shows that the numbers of switches are reduced in the proposed configuration, thus reducing the complexity and cost of the
system.
Winding voltage Winding Number of
Transformer (V) current(A) KVA Transformer Total KVA
Star/Delta 240/240 10 2.4 3 Nos 7.2
T-Connected 240/120/120 10 2.4 1 Nos 4.48
208/208 2.08 1 Nos
Table.7.1. Comparison with other technique.
VIII. CONCLUSION
A new three phase four wire DSTATCOM using T-connected transformer has been proposed for Three-Phase
Four-wire DSTATCOM system to improve the power quality. The performance of distribution system has been
demonstrated for neutral current compensation along with reactive power compensation, harmonic reduction and load
balancing for non-linear load.The performance of three-phase four-wire distribution system with and without controller
circuits for Non-linear load was discussed in the above section and following observation is obtained.From the performance
of the distribution system without controller source current of each phase is reduced to zero during the fault period
(ISA=0:ISB=0;ISC=6A from 0.2sec to 0.5sec as shown fig.7.1). This is compensated by using the DSTATCOM circuits and
also the load current of the each phase is compensated as shown fig.7.2. The THD of the system without controller is 37.85%
this is reduced to 5.57% with help of DSTATCOM. The reactive power Q was compensated and the power factor was
improved from 0.5119 to 0.8040 by using DSTATCOM. The VDC was regulated to reference value (700V) under all load
disturbances. The voltage regulation and power factor correction mode of operation of the DSTATCOM has been observed
as the expected ones.Two single phase transformers are used for the T-configuration of the transformer to interface with a
three-phase four-wire system. The total kilovolt amperes rating of the T-connected transformer is lower than a star/delta
transformer for a given neutral current compensation. From the above discussion, the proposed technique “A MODERN
APPROACH OF THREE-PHASE FOUR-WIRE DSTATCOM FOR POWER QUALITY IMPROVEMENT USING
T-CONNECTED TRANSFORMER” is very efficient one for power quality improvement of Three-phase Four-wire
distribution system compared to other techniques(Using star-delta and star-hexagon transformer).
APPENDIX-I
Line impedance: Rs = 0.01 Ω, Ls = 2 mH
For linear Loads: 20 KVA, 0.80 pF lag
For Nonlinear: Three single-phase bridge rectifiers with R = 25 Ω and C = 470 μF
Ripple filter: Rf = 5 Ω, Cf = 5 μF
DC bus voltage of DSTATCOM: 700 V
DC bus capacitance of DSTATCOM: 3000 μF
AC inductor: 2.5 mH
DC voltage PI controller: Kpd = 0.19, Kid = 6.25
PCC voltage PI controller: Kpq = 0.9, Kiq = 7.5
AC line voltage: 415 V, 50 Hz
PWM switching frequency: 10 kHz
Hence, two single-phase transformers of rating are
Rating of Transformer1: 5 kVA, 240 V/120 V/120 V and
Rating of Transformer2: 5 kVA, 208 V/208 V are selected.
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