The document discusses voltage regulation in distribution systems and describes how load flow calculations are dependent on accurate load models. It provides an overview of different components in an electrical power system including generation, transmission, and distribution. The document also describes various static load models that can be used in load flow analysis to better represent the characteristics of distribution system loads.
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.
The document provides an overview of power systems concepts including:
- Single-phase and three-phase power calculations including real, reactive, and apparent power.
- Modeling of common power system components like generators, transformers, loads, and transmission lines.
- The per-unit system used for power system analysis and its advantages.
Fuzzy Logic Controller for Static Synchronous Series Compensator with Line Po...paperpublications3
Abstract: This paper investigates the problem of controlling and modulating power flow in a transmission line using a Synchronous Static Series Compensator (SSSC). The studies, which include detailed PWM techniques controlled for SSSC, are conducted and the control circuits are presented. In this study, a static synchronous series compensator (SSSC) is used to investigate the effect of this device in controlling active and reactive powers as well as damping power system oscillations in transient mode. The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active power to or from the line. Simulations have been done in MATLAB/SIMULINK environment. Simulation results obtained for selected bus-2 in two machine power system shows the efficacy of this compensator as one of the FACTS devices member in controlling power flows, achieving the desired value for active and reactive powers, and damping oscillations appropriately.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
POWER SYSTEM STABILITY OF MULTI MACHINE BY USING STATIC SYNCHRONOUS SERIES CO...ijiert bestjournal
In this paper the problem of modeling and simulati on of voltage stability is improved using Static Synchronous Series Compensator (SSSC). Due t o the continuous demand in electric power system,the system is heavily loaded,this ca uses to voltage instability. In this work,a static synchronous series compensator (SSSC) is use d to minimize the effect of this device in controlling active and reactive powers as well as d amping power system oscillations in transient mode. The PI controller is used to achiev e the zero signal error. The result is obtained from simulation using MATLAB. In short whe n any disturbances occur in transmission line,if SSSC is connected then distur bance in the system is minimized & system will reach the steady state condition very quickly.
The document describes modeling a power system network using an admittance matrix formulation. Key points:
1) Branches are modeled as admittances to relate voltage and current. The admittance matrix (Y-bus) is formed with diagonal elements equal to the sum of incident branch admittances and off-diagonals equal to the negative of branch admittances.
2) Kirchhoff's and Ohm's laws are used to write equations relating bus voltages and branch currents.
3) Simplifying assumptions are made to develop the "DC power flow" equations, including ignoring voltage magnitudes and angles and resistance. This leads to a linear relationship between bus voltage angles and real power injections
Comparison of Shunt Facts Devices for the Improvement of Transient Stability ...IJSRD
This paper presents, the performance of STATCOM placed at midpoint of the two machine power system and compared with the performance of SVC. The comparison of various results found for the different type of faults (single line, double line & three phase fault) occur in long transmission line, and their removal by using shunt FACTS devices is analysed. Computer simulation results under a severe disturbance condition (three phase fault) for different fault clearing times, and different line lengths are analyzed. Both controllers are implemented using MATLAB/SIMULINK. Simulation results shows that the STATCOM with conventional PI controller installed with two machine three bus systems provides better damping oscillation characteristics in rotor angle as compared to two machine power system installed with SVC. The transient stability of two machine system installed with STATCOM has been improved considerably and post settling time of the system after facing disturbance is also improved.
Assignment 1 170901 interconnected power systemVara Prasad
1. The document discusses power system analysis and modeling of various components in a power system. It provides definitions, equations, and examples related to topics like load flow analysis, bus types, transformer modeling, and transmission line modeling.
2. Key aspects covered include defining the three main bus types - PQ bus, PV bus, and slack bus - and explaining the quantities specified for each. Equations are given for calculating base values like current and impedance as well as transforming values between bases.
3. Modeling of components like transformers and transmission lines is also summarized, along with advantages of per-unit systems. Factors affecting stability and methods to improve it are briefly mentioned.
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.
The document provides an overview of power systems concepts including:
- Single-phase and three-phase power calculations including real, reactive, and apparent power.
- Modeling of common power system components like generators, transformers, loads, and transmission lines.
- The per-unit system used for power system analysis and its advantages.
Fuzzy Logic Controller for Static Synchronous Series Compensator with Line Po...paperpublications3
Abstract: This paper investigates the problem of controlling and modulating power flow in a transmission line using a Synchronous Static Series Compensator (SSSC). The studies, which include detailed PWM techniques controlled for SSSC, are conducted and the control circuits are presented. In this study, a static synchronous series compensator (SSSC) is used to investigate the effect of this device in controlling active and reactive powers as well as damping power system oscillations in transient mode. The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active power to or from the line. Simulations have been done in MATLAB/SIMULINK environment. Simulation results obtained for selected bus-2 in two machine power system shows the efficacy of this compensator as one of the FACTS devices member in controlling power flows, achieving the desired value for active and reactive powers, and damping oscillations appropriately.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
POWER SYSTEM STABILITY OF MULTI MACHINE BY USING STATIC SYNCHRONOUS SERIES CO...ijiert bestjournal
In this paper the problem of modeling and simulati on of voltage stability is improved using Static Synchronous Series Compensator (SSSC). Due t o the continuous demand in electric power system,the system is heavily loaded,this ca uses to voltage instability. In this work,a static synchronous series compensator (SSSC) is use d to minimize the effect of this device in controlling active and reactive powers as well as d amping power system oscillations in transient mode. The PI controller is used to achiev e the zero signal error. The result is obtained from simulation using MATLAB. In short whe n any disturbances occur in transmission line,if SSSC is connected then distur bance in the system is minimized & system will reach the steady state condition very quickly.
The document describes modeling a power system network using an admittance matrix formulation. Key points:
1) Branches are modeled as admittances to relate voltage and current. The admittance matrix (Y-bus) is formed with diagonal elements equal to the sum of incident branch admittances and off-diagonals equal to the negative of branch admittances.
2) Kirchhoff's and Ohm's laws are used to write equations relating bus voltages and branch currents.
3) Simplifying assumptions are made to develop the "DC power flow" equations, including ignoring voltage magnitudes and angles and resistance. This leads to a linear relationship between bus voltage angles and real power injections
Comparison of Shunt Facts Devices for the Improvement of Transient Stability ...IJSRD
This paper presents, the performance of STATCOM placed at midpoint of the two machine power system and compared with the performance of SVC. The comparison of various results found for the different type of faults (single line, double line & three phase fault) occur in long transmission line, and their removal by using shunt FACTS devices is analysed. Computer simulation results under a severe disturbance condition (three phase fault) for different fault clearing times, and different line lengths are analyzed. Both controllers are implemented using MATLAB/SIMULINK. Simulation results shows that the STATCOM with conventional PI controller installed with two machine three bus systems provides better damping oscillation characteristics in rotor angle as compared to two machine power system installed with SVC. The transient stability of two machine system installed with STATCOM has been improved considerably and post settling time of the system after facing disturbance is also improved.
Assignment 1 170901 interconnected power systemVara Prasad
1. The document discusses power system analysis and modeling of various components in a power system. It provides definitions, equations, and examples related to topics like load flow analysis, bus types, transformer modeling, and transmission line modeling.
2. Key aspects covered include defining the three main bus types - PQ bus, PV bus, and slack bus - and explaining the quantities specified for each. Equations are given for calculating base values like current and impedance as well as transforming values between bases.
3. Modeling of components like transformers and transmission lines is also summarized, along with advantages of per-unit systems. Factors affecting stability and methods to improve it are briefly mentioned.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
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 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.
Active Reactive Power Flow Control Using Static Synchronous Series Compensato...IOSR Journals
1) The document discusses using a Static Synchronous Series Compensator (SSSC) and STATCOM to control active and reactive power flow in transmission lines.
2) An SSSC injects a controllable voltage in quadrature with the line current, allowing both capacitive and inductive compensation. A STATCOM regulates voltage by controlling reactive power injection or absorption.
3) Simulation studies were conducted on a two-area, 11-bus system model in MATLAB/Simulink to observe the compensation achieved by installing an SSSC or STATCOM. The system parameters, such as voltage, current, active and reactive power transmissions were monitored with the FACTS devices connected.
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
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Hybrid T-I-D and Fuzzy Logic Based SVC Controller for Transient Stability Enh...IJERA Editor
This paper presents a new approach to solve the transient stability problem. The conventional PI based SVC controller has simple functioning and is economical in operation but has sluggish performance with non-linear characteristics. so, in order to circumvent this problem, fuzzy based T-I-D controller has been designed to improve the transient stability of 2 machine 3 bus power system using MATLAB/SIMULINK software.
This document discusses power system fault analysis. It begins by outlining the learning objectives and syllabus, which include power flow analysis, power system faults, and power system stability. It then provides an introduction to power system fault analysis, explaining that faults usually occur due to insulation failure, flashover, physical damage or human error. Faults can be three-phase symmetrical or asymmetrical, and involve short-circuits to earth, between phases, or open circuits. Fault analysis is carried out using per-unit quantities. The document goes on to discuss equivalent circuits for single-phase and three-phase systems, and revising per-unit quantities and conversions between different bases.
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.
Power system analysis material -Mathankumar.s VMKVECMathankumar S
This document provides an overview of power systems, including different types of power generation sources like thermal, hydroelectric, nuclear, gas turbine, and diesel power plants. It also describes the basic components of a power system such as generators, transformers, transmission lines, and loads. Additionally, it discusses the voltage structure of electric power systems including generating stations, transmission systems, and distribution systems. Finally, it introduces the need for system analysis in planning and operating power systems, and distinguishes between steady state and transient state stability analysis.
EE6501 Power System Analysis Rejinpaul_Important_QuestionsSanthosh Kumar
This document provides sample exam questions for a 5th semester power systems analysis course. It covers topics like power flow analysis, fault analysis, sequence networks, transient stability, and swing equations. The questions involve calculating fault currents, drawing impedance diagrams, solving load flows, determining critical clearing angles, and more. In total, there are 5 units covering different power systems analysis concepts, and each unit provides 5 sample exam questions related to those concepts for review.
POWER QUALITY IMPROVEMENT BY SSSC AND STATCOM USING PI CONTROLLERJournal For Research
This document summarizes research on using SSSC (Static Synchronous Series Compensator) and STATCOM (Static Synchronous Compensator) to improve power quality and voltage stability in a two machine, four bus power system model. It describes the basic operational principles of SSSC and STATCOM, which are FACTS devices that can be connected in series and parallel, respectively, with transmission lines. The document presents simulation results showing that connecting an SSSC to Bus 2 and a STATCOM to Bus 2 both increase the voltage levels and regulate active and reactive power flows at the different buses, demonstrating the effectiveness of these devices for maintaining voltage stability.
This document discusses several power system engineering concepts studied using PowerWorld simulator. It includes 10 problems analyzing topics like power flow analysis, fault analysis, unsymmetrical faults, power factor correction, transmission line diagrams, phase shifting transformers, transmission line conductor selection, transmission line evaluation, load angle estimation, and short circuit duty. The first problem analyzes real and reactive power flow between two buses under base case conditions and with an increased load. It establishes the relationships between real power and load angle and reactive power and voltage.
Power System Analysis was a core subject for Electrical & Electronics Engineering, Based On Anna University Syllabus. The Whole Subject was there in this document.
Share with it ur friends & Follow me for more updates.!
Power quality issues can arise from reactive power demand, harmonic distortion, voltage sags and swells, unbalance, flicker, notching, and interruptions. Non-linear loads like rectifiers and adjustable speed drives generate harmonics. Harmonics can overheat equipment and increase losses. Voltage sags are brief reductions in voltage from events like motor starts. Unbalance occurs when three-phase voltages differ in magnitude. Flicker is the perception of lighting variations below 25 Hz. Mitigation methods include active and passive filters, dynamic voltage restorers, static compensators, and surge arresters.
Determination of Voltage Regulation and Power system lossesManish Sadhu
The document discusses voltage regulation and losses in power systems. It defines voltage regulation as maintaining a stable voltage level for consumers. Methods to regulate voltage include transformer taps, automatic voltage regulators, boosters, and capacitors. Power system losses occur in components like transformers, transmission lines, and motors. These losses can be reduced by techniques such as power factor correction, optimal component loading, and use of lower resistance conductors. Measurement of losses involves calculating the difference between total power input and useful power output.
Nowadays, it is very important to maintain voltage level. Controlling of that voltage is also important. This Presentation contains methods of voltage control.
It is very useful power point presentation on the "Grid Voltage Regulation"
it consist all thing related with topic.
I have already presented and got 100% credit.
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
Application of Capacitors to
Distribution System and Voltage
Regulation
POWER FACTOR IMPROVEMENT,
System Harmonics
Voltage Regulation
Methods of Voltage Control
Tap changers are devices fitted to power transformers that allow for regulation of the output voltage. Voltage regulation is achieved by altering the number of turns in one winding of the transformer, which changes the transformer ratios. Tap changers offer variable control to keep the supply voltage within limits. They can be on load or off load tap changers. On load tap changers consist of a diverter switch and selector switch to transfer current between taps without interruption.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
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 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.
Active Reactive Power Flow Control Using Static Synchronous Series Compensato...IOSR Journals
1) The document discusses using a Static Synchronous Series Compensator (SSSC) and STATCOM to control active and reactive power flow in transmission lines.
2) An SSSC injects a controllable voltage in quadrature with the line current, allowing both capacitive and inductive compensation. A STATCOM regulates voltage by controlling reactive power injection or absorption.
3) Simulation studies were conducted on a two-area, 11-bus system model in MATLAB/Simulink to observe the compensation achieved by installing an SSSC or STATCOM. The system parameters, such as voltage, current, active and reactive power transmissions were monitored with the FACTS devices connected.
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
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Hybrid T-I-D and Fuzzy Logic Based SVC Controller for Transient Stability Enh...IJERA Editor
This paper presents a new approach to solve the transient stability problem. The conventional PI based SVC controller has simple functioning and is economical in operation but has sluggish performance with non-linear characteristics. so, in order to circumvent this problem, fuzzy based T-I-D controller has been designed to improve the transient stability of 2 machine 3 bus power system using MATLAB/SIMULINK software.
This document discusses power system fault analysis. It begins by outlining the learning objectives and syllabus, which include power flow analysis, power system faults, and power system stability. It then provides an introduction to power system fault analysis, explaining that faults usually occur due to insulation failure, flashover, physical damage or human error. Faults can be three-phase symmetrical or asymmetrical, and involve short-circuits to earth, between phases, or open circuits. Fault analysis is carried out using per-unit quantities. The document goes on to discuss equivalent circuits for single-phase and three-phase systems, and revising per-unit quantities and conversions between different bases.
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.
Power system analysis material -Mathankumar.s VMKVECMathankumar S
This document provides an overview of power systems, including different types of power generation sources like thermal, hydroelectric, nuclear, gas turbine, and diesel power plants. It also describes the basic components of a power system such as generators, transformers, transmission lines, and loads. Additionally, it discusses the voltage structure of electric power systems including generating stations, transmission systems, and distribution systems. Finally, it introduces the need for system analysis in planning and operating power systems, and distinguishes between steady state and transient state stability analysis.
EE6501 Power System Analysis Rejinpaul_Important_QuestionsSanthosh Kumar
This document provides sample exam questions for a 5th semester power systems analysis course. It covers topics like power flow analysis, fault analysis, sequence networks, transient stability, and swing equations. The questions involve calculating fault currents, drawing impedance diagrams, solving load flows, determining critical clearing angles, and more. In total, there are 5 units covering different power systems analysis concepts, and each unit provides 5 sample exam questions related to those concepts for review.
POWER QUALITY IMPROVEMENT BY SSSC AND STATCOM USING PI CONTROLLERJournal For Research
This document summarizes research on using SSSC (Static Synchronous Series Compensator) and STATCOM (Static Synchronous Compensator) to improve power quality and voltage stability in a two machine, four bus power system model. It describes the basic operational principles of SSSC and STATCOM, which are FACTS devices that can be connected in series and parallel, respectively, with transmission lines. The document presents simulation results showing that connecting an SSSC to Bus 2 and a STATCOM to Bus 2 both increase the voltage levels and regulate active and reactive power flows at the different buses, demonstrating the effectiveness of these devices for maintaining voltage stability.
This document discusses several power system engineering concepts studied using PowerWorld simulator. It includes 10 problems analyzing topics like power flow analysis, fault analysis, unsymmetrical faults, power factor correction, transmission line diagrams, phase shifting transformers, transmission line conductor selection, transmission line evaluation, load angle estimation, and short circuit duty. The first problem analyzes real and reactive power flow between two buses under base case conditions and with an increased load. It establishes the relationships between real power and load angle and reactive power and voltage.
Power System Analysis was a core subject for Electrical & Electronics Engineering, Based On Anna University Syllabus. The Whole Subject was there in this document.
Share with it ur friends & Follow me for more updates.!
Power quality issues can arise from reactive power demand, harmonic distortion, voltage sags and swells, unbalance, flicker, notching, and interruptions. Non-linear loads like rectifiers and adjustable speed drives generate harmonics. Harmonics can overheat equipment and increase losses. Voltage sags are brief reductions in voltage from events like motor starts. Unbalance occurs when three-phase voltages differ in magnitude. Flicker is the perception of lighting variations below 25 Hz. Mitigation methods include active and passive filters, dynamic voltage restorers, static compensators, and surge arresters.
Determination of Voltage Regulation and Power system lossesManish Sadhu
The document discusses voltage regulation and losses in power systems. It defines voltage regulation as maintaining a stable voltage level for consumers. Methods to regulate voltage include transformer taps, automatic voltage regulators, boosters, and capacitors. Power system losses occur in components like transformers, transmission lines, and motors. These losses can be reduced by techniques such as power factor correction, optimal component loading, and use of lower resistance conductors. Measurement of losses involves calculating the difference between total power input and useful power output.
Nowadays, it is very important to maintain voltage level. Controlling of that voltage is also important. This Presentation contains methods of voltage control.
It is very useful power point presentation on the "Grid Voltage Regulation"
it consist all thing related with topic.
I have already presented and got 100% credit.
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
Application of Capacitors to
Distribution System and Voltage
Regulation
POWER FACTOR IMPROVEMENT,
System Harmonics
Voltage Regulation
Methods of Voltage Control
Tap changers are devices fitted to power transformers that allow for regulation of the output voltage. Voltage regulation is achieved by altering the number of turns in one winding of the transformer, which changes the transformer ratios. Tap changers offer variable control to keep the supply voltage within limits. They can be on load or off load tap changers. On load tap changers consist of a diverter switch and selector switch to transfer current between taps without interruption.
Distribution System Voltage Drop and Power Loss CalculationAmeen San
Distribution System Voltage Drop and Power Loss
Calculation
Comparison of Overhead Versus Underground System
Power Loss Calculation,Voltage Drop Calculation
The document discusses transformer protection. It describes various failures that can occur in transformers such as winding failures, bushing failures, and tap changer failures. It provides statistics on historical transformer failures. It also discusses different types of protection for transformers including electrical protection methods like differential protection, overcurrent protection, overexcitation protection and thermal protection. Internal short circuits, system short circuits, and abnormal conditions are some of the issues addressed by transformer protection schemes.
This document discusses different types of voltage regulators. It describes linear regulators as either series or shunt types, with series regulators having a control element in series with the load and shunt regulators having a control element parallel to the load. Switching regulators are introduced as another type that passes voltage to the load in pulses to improve efficiency. Integrated circuit voltage regulators are also covered, including fixed positive and negative voltage regulators, as well as adjustable voltage regulators.
The document discusses high voltage distribution systems (HVDS) as an alternative to traditional low voltage distribution systems (LVDS). It outlines three main types of HVDS - phase-neutral, phase-phase, and phase-ground - and describes their components and configurations. HVDS is presented as a technically superior option to LVDS, offering benefits like lower line losses, improved voltage profile, reduced theft and failures. Restructuring an existing LVDS network to HVDS could result in power loss reductions of 25-80% and payback periods of around 18 months, making it a viable option.
Assignment 1 170901 interconnected power systemVara Prasad
Planning and operation of a power system requires studies of load, faults, protection from surges and short circuits, and stability. A disturbance causes changes in system parameters moving it from steady to transient state. Small disturbances can be analyzed linearly while large disturbances require nonlinear analysis. Transient stability means generators remain synchronized after a disturbance and steady state stability means the system returns to the pre-disturbance steady state after a small disturbance. Per unit representations use common base values for analysis and allow easy conversion between different bases.
International Journal of Computational Engineering Research (IJCER) ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
This document contains information about power system components and fault analysis. It includes:
- An introduction to one-line diagrams and their use in representing power systems through standardized schematic symbols. One-line diagrams simplify three-phase systems and are useful for power flow studies.
- Descriptions of impedance diagrams and reactance diagrams, which represent power system components through equivalent circuits by replacing elements like generators, transformers, and transmission lines with their impedances or reactances.
- Examples of drawing one-line, impedance, and reactance diagrams for given power system configurations. Resistances are often omitted from reactance diagrams for fault analysis calculations.
- Explanations of symmetrical components and their use
This document contains the question bank for the subject EE 1351 Power System Analysis. It includes 18 multiple choice and numerical questions related to modeling components of a power system including generators, transmission lines and transformers. It also covers per-unit calculations, impedance and reactance diagrams, bus admittance matrices, symmetrical components and power flow analysis. Sample questions are provided on determining the per-unit impedances of components, drawing equivalent circuits, calculating sequence impedances and modeling various elements for power flow studies.
The document discusses per unit calculations in power systems. It defines per unit quantities as actual quantities normalized by a base quantity. Common base quantities used are voltage (Vbase), apparent power (Sbase), and impedance (Zbase). The document provides formulas for calculating base impedance and converting impedances to different bases. It includes an example of calculating the per unit impedances of components in a sample power system diagram and drawing the equivalent impedance diagram.
The document discusses key concepts in per unit representation systems for power systems analysis. It defines per unit values as the ratio of an actual value to a base value, and explains that per unit systems simplify analysis by eliminating factors of √3 and 3. The document also outlines advantages of per unit systems like providing relative magnitude information, simplifying analysis with different voltage levels/transformer ratios, and allowing assumed values when specific data is unavailable. Base values are needed to convert different components to common reference values for unified analysis of the entire power system.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
This document summarizes a research paper on improving voltage stability and reducing losses in distribution networks through distributed generation. The paper analyzes how distributed generation capacity and location can enhance voltage stability in a real distribution network. It presents a method to determine the steady-state voltage stability region of each bus in a distribution system. Simulation results show that distributed generation can reduce line losses by supplying power locally, with losses decreasing as generation is placed closer to loads. Both the capacity and location of distributed generation significantly impact line losses.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
IRJET-Power Flow & Voltage Stability Analysis using MATLAB IRJET Journal
This document presents a MATLAB program for power flow analysis and voltage stability analysis of power systems. It begins with an introduction to power flow analysis and its importance. It then discusses voltage stability concepts like voltage collapse and improvement methods. The methodology section describes the Newton-Raphson power flow method and P-V and Q-V curves used for voltage stability analysis. It also provides the algorithm and case study details for the IEEE 14 bus system implemented in MATLAB. The program allows for power flow solutions, calculation of P-V and Q-V curves, and voltage stability assessment of power systems.
Power Flow & Voltage Stability Analysis using MATLAB IRJET Journal
This document presents a MATLAB program for power flow analysis and voltage stability analysis of power systems. It begins with an introduction to power flow analysis and its importance. It then discusses voltage stability concepts like voltage collapse and improvement methods. The methodology section describes the Newton-Raphson power flow method and P-V and Q-V curves used for voltage stability analysis. It also provides the algorithm and case study details for the IEEE 14 bus system implemented in MATLAB. The program allows for power flow solutions, calculation of P-V and Q-V curves, and voltage stability assessment of power systems.
Performance Improvement of the Radial Distribution System by using Switched C...idescitation
Distribution system is the major link which provides supply to the consumers
from the high voltage transmission system. The load on the distribution system is not
constant and it changes with respect to time throughout the working period. The voltage
drop and power losses occur in the distribution system mainly depends on the nature of the
load which is applied on the system. The voltage drop and power losses frequently occurs
mainly on those systems which are supplying load to the industrial areas, this is mainly
because of the existence of more reactive power. To overcome these problems shunt
compensation is employed to reduce or suppress those effects to an extent. The main aim of
this paper is to determine the specific value of the shunt capacitance required to achieve the
permissible voltage tolerance limits and maximum percentage of power loss reduction in a
sample two feeder radial distribution system.
This document compares the effectiveness of STATCOM, SSSC, and UPFC FACTS devices in improving power system stability. It presents a single machine infinite bus system model with each device and analyzes the response to a 3-phase fault. All FACTS devices reduce oscillations and stabilize the system after the fault, while the uncompensated system becomes unstable. STATCOM and SSSC effectively suppress oscillations and stabilize the rotor angle, velocity, and generator output power. UPFC combines features of STATCOM and SSSC to regulate real and reactive power flow and make the system stable.
Voltage Regulators Placement in Unbalanced Radial Distribution Systems for Lo...paperpublications3
Abstract: The Automatic Voltage Regulators (AVRs) help to reduce energy loss and improve the power quality of electric utilities. This paper presents selection of optimal location and tap setting for voltage regulators in Unbalanced Radial Distribution Systems (URDS). Power loss index (PLI) is used for the selection of optimal location of voltage regulators which will first found at each branch except source bus and the bus that has the highest power loss index are picked as the best location for the voltage regulators placement. Particle swarm optimization (PSO), is used for selecting the tap position of voltage regulator in an unbalanced radial distribution system. This algorithm makes the initial selection and tap position setting of the voltage regulators to minimize power losses and provide a good voltage profile along the distribution network and then reduce the total cost to obtain the maximum net savings. The effectiveness of the proposed method is illustrated on a test system of IEEE 33 bus unbalanced radial distribution systems.
Keywords:Unbalanced Radial Distribution Systems (URDS), Load Flow, Power loss index(PLI),Particle swarm optimization(PSO), Voltage Regulator placement, Loss minimization, cost saving.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
A Simulink Model for Damping Power System Oscillations Using Fact DevicesIOSR Journals
This document presents a Simulink model for damping power system oscillations using FACTS devices. It describes a hybrid series compensation scheme using a single-phase thyristor controlled series capacitor (TCSC) and fixed capacitors on the other two phases. The TCSC is equipped with a proportional-integral controller to modulate its reactance based on stabilizing signals. Case studies on a test power system show the hybrid scheme provides better damping than fixed compensation alone. The best damping was achieved using local generator angle differences as stabilizing signals.
Enhancement for Power Quality in Distribution Side Using Custom Power DevicesIOSR Journals
1) The document discusses enhancing power quality in distribution systems using custom power devices like the Interline Unified Power Quality Conditioner (IUPQC).
2) It proposes using a Synchronous Reference Frame (SRF) control algorithm with a modified Phase Locked Loop (PLL) for generating gate signals to improve the IUPQC's performance under distorted voltage conditions.
3) The SRF method transforms voltage and current signals into rotating dq coordinates to extract fundamental frequency components, while the modified PLL improves determination of positive sequence system voltages for better filtering.
The document discusses analyzing a single-phase power system and its theoretical variations through per unit analysis using MATLAB. It provides the theory behind per unit analysis and calculates the per unit values of the system parameters. It then manually solves the system using per unit analysis and compares the results to those obtained through simulation in MATLAB.
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
[IJET V2I2P30] Authors: AnkurGheewala, Jay Chanawala,Nikhil Jadav,Modi Rishit...
Main
1. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
DISTRIBUTION SYSTEM VOLTAGE REGULATION
FOR DIFFERENT STATIC LOAD MODELS
CONTENTS :
1
2. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
ABSTRACT …………………………………………………………………………..7
1. INTRODUCTION
1.1. Introduction to electrical power system……………………………….8
(a) Generation system……………………………………………………….9
(b) Transmission system……………………………………………………10
(c) Distribution system……………………………………………………..10
1.2. Brief overview of distribution system………………………………….11
1.3. Distribution system configuration……………………………………..12
1.4. Primary distribution system…………………………………………….13
1.5. Secondary distribution system………………………………………...15
1.6. Literature survey…………………………………………………………..16
2. LOAD FLOW ANALYSIS
2.1. Proposed Method…………………………………………………………..21
2.2 .Solution methodology……………………………………………………..22
2.3. Explanation of the proposed algorithm……………………………….25
2.4. Static load models………………………………………………………….27
2.5 .Algorithm for Load flow computation………………………………....30
3. EXAMPLES………………………………………………………….37
4.SUMMARY AND FUTURE SCOPE
(i) Conclusion……………………………………………………………….....40
(ii) Future scope………………………………………………………………..41
5. References………………………………………………………………………..42
2
3. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
6. Appendix A……………………………………………………………………….43
7. Appendix B………………………………………………………………………45
LIST OF FIGURES:
Fig 1.1 A single line diagram of a distribution substation………..12
Fig 1.2 Primary distribution feeder……………………………………..14
Fig 1.3 Service drops in distribution systems………………………..15
Fig 2.1 Radial main feeder…………………………………………………22
Fig 2.2 Electrical Equivalent of figure…………………………………..22
Fig 2.3 Flow Chart for the Algorithm of radial
distribution network having laterals…………………………33
Fig 3.1 34 node radial distribution system……………………………37
3
4. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
LIST OF TABLES:
Table1 Details of the numbering scheme of figure 3.1……………..24
Table 2 Non-zero integer values of F(i)………………………………….25
Table 3 Voltage magnitude (p.u.) of each node for 34………………38
node radial distribution network for CP,CI,CZ load models
Table 4 Power losses for CP,CI,CZ load models……………………..39
Table 5 Voltage regulation for CP,CI,CZ load models………………39
Table 6 Line Data of 34 Node Radial Distribution Network……….43
Table 7 Load Data of 34 Node Radial Distribution Network………44
4
5. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Nomenclature:
NB = total number of nodes.
(j) = branch number, j=1, 2,………, NB-1
PL(i)= real power load of ith node
QL(i)= reactive power load of ith node
|V(i)|=voltage magnitude of ith node
R(j)= resistance of jth branch
X(j)=reactance of jth branch
I(j)=current flowing through branch j
P(i+1)=total real power load fed through node i+1
Q(i+1)= total reactive power load fed through node i+1
δ(i+1)=voltage angle of node i+1
LP(j)=real power loss of branch j
LQ(j)= reactive power loss of branch j
NL=total number of laterals
[L]=lateral number, L=1, 2,.…., NL
SN(L)=source node of lateral L
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6. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
EB(L)= end node of lateral L
LB(L)=node, just ahead of source node of lateral L
F(i)= integer variable
TP(L)= total real power load fed through the node LB(L) of lateral L
TQ(L)= total reactive power load fed through the node LB(L) of lateral L
SPL(L)= sum of real power loads of all the nodes of lateral L which have
just been left plus the sum of real power losses of all the
branches of lateral L which have just been left except the real
power loss in branch {LB(L)-1} of lateral L
SQL(L)= sum of reactive power loads of all the nodes of lateral L which
have just been left plus the sum of reactive power losses of all
the branches of lateral L which have just been left except the
reactive power loss in branch {LB(L)-1} of lateral L
PS(L)= sum of the real power loads of all the nodes(except source nodes)
of all the laterals which have just been left plus the sum of real
power losses of all the branches of all the laterals which have
just been left.
QS(L)= sum of the reactive power loads of all the nodes(except source
nodes) of all the laterals which have just been left plus the sum of
reactive power losses of all the branches of all the laterals which
have just been left.
6
7. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
ABSTRACT:
Voltage regulation computations for distribution systems are strongly
dependent on power flow solutions. The classical constant power load model
is typically used in power flow studies of transmission or distribution
Systems; however, the actual load of a distribution system cannot just be
modeled using constant power models, requiring the use of constant
current, constant impedance, exponential or a mixture of all these load
models to accurately represent the load. This paper presents a study of
voltage regulation of a distribution system using different Static load
models.
7
8. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
CHAPTE-1
INTRODUCTION
Voltage regulation is an important subject in electrical distribution
engineering. It is the utilities responsibility to keep the customer voltage
within specified tolerances. The performance of a distribution system and
quality of the service provided are not only measured in terms of
frequency of interruption but in the maintenance of satisfactory voltage
levels at the customers’ premises. A high steady-state voltage can reduce
light bulb life and reduce the life of electronic devices. On the other hand,
a low steady-state voltage leads to low illumination levels, shirking of
television pictures, slow heating of heating devices, motor starting
problems, and overheating in motors. However, most equipment and
appliances operate satisfactorily over some reasonable range of voltages,
hence; certain tolerances are allowable at the customer’s end. Thus, it is
common practice among utilities to stay within preferred voltage levels
and ranges. The steady-state voltage regulations should be within +6%
to−13% for satisfactory operation of various electrical devices. Voltage
regulation calculations depend on the power flow solutions of a System.
Most of the electrical loads of a power system are connected to low
voltage or Medium-voltage distribution systems rather than to a high-
voltage transmission system. The loads connected to the distribution
system are certainly voltage dependent; thus, these types of load
characteristics should be considered in load flow studies to get accurate
results and to avoid costly errors in the analysis of the system. For
example, in voltage regulation improvement studies, possible under- or
over-compensation can be avoided if more accurate results of load flow
solutions are available. However, most conventional load flows use a
constant power load model, which assumes that active and reactive
powers are independent of voltage changes. In reality, constant power
load models are highly questionable in distribution systems, as most
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9. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
nodes are not voltage controlled; therefore, it is very important to
consider better load models in these types of load flow problems. In this
paper, distribution system voltage regulation and the effect of shunt
capacitor compensation on this regulation for different static load models
are studied.
1.1 Introduction to electrical power system:
The electric power system is a network of interconnected
components which generate electricity by converting different forms of
energy, (potential energy, kinetic energy, or chemical energy are the most
common forms of energy converted) to electrical energy.
The electric power system consists of three main subsystems:
1. Generation system,
2. Transmission system, and
3. Distribution system.
Electricity is generated at the generating station by converting a primary
source of energy to electrical energy. The voltage output of the generators
is then stepped up to appropriate transmission levels using a step-up
transformer. The transmission subsystem then transmits the power close
to the load centers. The voltage is then stepped down to appropriate
levels. The distribution subsystem then transmits the power close to the
customer where the voltage is stepped-down to appropriate levels or use
by a residential, industrial, or commercial customer.
1.1 (a) Generation system:
Generation plants consist of one or more generating units that convert
mechanical energy into electricity by turning a prime mover coupled to
an electric generator. Generators produce line-to-line voltages between 11
kv and 30 kv. The ability of generation plants to supply all of the power
demanded by a customers is referred to as system adequacy. Three
conditions must be met to ensure system adequacy.
1. Available generation capacity must be greater than demanded load
plus system losses.
2. The system must be able to transport demanded power to customers
without overloading equipment.
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10. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
3. Customers must be served within an acceptable voltage range.
1.1 (b) Transmission system:
Electric power transmission is the bulk transfer of electrical power, a
process in the delivery of electricity to consumers. Transmission systems
transport electricity over long distances from generation substations to
transmission or distribution substations. Typical voltage levels include
69 kv, 115 kv, 138 kv, 161 kv, 230 kv, 345 kv, 500 kv, 765 kv, and 1100
Kv. Transmission substations are transmission switching stations with
transformers that step down voltage to sub transmission levels. Sub
transmission systems transport electricity from transmission substations
to distribution substations. Typical voltage levels include 34.5kv, 46 kv,
69 kv, 115 kv, 138 kv, 161 kv, and 230 kv.
1.1 (c) Distribution systems:
Distribution substations are nodes for terminating and reconfiguring sub
transmission Lines plus transformers that step down voltage to primary
distribution levels.
Primary distribution systems: deliver electricity from distribution
substations to distribution transformers. Voltages range from 4.16 kv to
34.5 kv with the most common being 15-kv class (e.g., 12.47 kv, 13.8
kv).
Distribution transformers: Convert primary distribution voltages to
utilization voltages. Typical sizes range from 5 kva to 2500 kva.
Secondary distribution systems: deliver electricity from distribution
transformers to customer service entrances. Voltages are typically
120/240v single phase, 120/208v three phase, or 277/480v three phase.
1.2 Brief overview of distribution system:
Distribution systems deliver power from bulk power systems to
retail customers. To do this, distribution substations receive power from
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11. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
sub transmission lines and step down voltages with power transformers.
These transformers supply primary distribution systems made up of
many distribution feeders. Feeders consist of a main 3φ trunk, 2 φ and 1
φ laterals, feeder interconnections, and distribution transformers.
Distribution transformers step down voltages to utilization levels and
supply secondary mains or service drops. Distribution planning
departments at electric utilities have historically concentrated on
capacity issues, focusing on designs that supply all customers at peak
demand within acceptable voltage tolerances without violating equipment
ratings. Capacity planning is almost always performed with rigorous
analytical tools such as power flow models. Reliability, although
considered important, has been a secondary concern usually addressed
by adding extra capacity and feeder ties so that certain loads can be
restored after a fault occurs. Distribution systems begin at distribution
substations. An elevation and corresponding one-line diagram of a simple
distribution substation is shown in figure.
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12. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Figure 1.1: A single-line diagram of a distribution substation
The substation’s source of power is a single overhead sub transmission
line that enters from the left and terminates on a take-off (dead-end)
structure. The line is connected to a disconnect switch, mounted on this
same structure, capable of visibly isolating the substation from the sub
transmission line. Electricity is routed from the switch across a voltage
transformer through a current transformer to a circuit breaker. This
breaker protects a power transformer that steps voltage down to
distribution levels. High voltage components are said to be located on the
“high side” or “primary side” of the substation.
1.3 Distribution system configuration:
The design of the distribution system mainly depends on the
chosen classification of single or three phase, radial or loop network,
overhead line or underground cables. The essential factors to be kept in
mind while planning a distribution system are:
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13. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
1) Safety: the safety factor requires the distributors to be laid following:
(i) Proper clearances.
(ii) Voltage safe enough to be used for consumer’s gadgets.
2) Smooth and even flow of power: a steady, uniform, non-fluctuating
flow of power is necessary to feed loads of all categories of consumers.
3) Economy: the third factor is economy. This usually calls for use of
higher
Voltage to ensure minimum losses while distribution power.
1.4 Primary distribution system:
Primary distribution systems consist of feeders that deliver power from
distribution substations to distribution transformers. A feeder begins
with a feeder breaker at the distribution substation. Many will exit the
substation in a concrete duct bank (feeder get-away) and be routed to a
nearby pole. At this point, underground cable transitions to an overhead
three-phase main trunk. The main trunk is routed around the feeder
service territory and may be connected to other feeders through
normally-open tie points. Underground main trunks are possible, even
common in urban areas, but cost much more than overhead
construction. Lateral taps off of the main trunk are used to cover most of
a feeder’s service territory. These taps are typically 1φ, but may also be 2
φ or 3 φ. Laterals can be directly connected to main trunks, but are more
commonly protected by fuses, recloses, or automatic sectionalizes.
Overhead laterals use pole-mounted distribution transformers to serve
customers and underground laterals use pad mount transformers. An
illustrative feeder showing different types of laterals and devices is shown
in figure.
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14. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Figure 1.2 primary distribution feeder
There are two type of distribution line exists in primary distribution
systems overhead lines and underground lines. In overhead lines, wires
carry load current in an overhead system. Major classifications are by
insulation, size, stranding, material, impedance, and capacity. Lines
without an insulated cover are called bare conductors and all other lines
are referred to as insulated conductors. Insulated conductors are further
classified into covered conductor, tree wire, spacer cable, and aerial
cable. Covered conductor and tree wire have a thin covering of insulation
that cannot withstand phase to ground voltages, but reduce the
probability of a fault if vegetation bridges two conductors. Spacer cable
has increased insulation that allows conductors to be arranged in a small
triangular configuration. Aerial cable has fully rated insulation capable of
withstanding phase to ground voltages.
14
15. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
1.5 SECONDARY DISTRIBUTION SYSTEMS:
Secondary systems connect distribution transformers to customer
service entrances. They can be extremely simple, like overhead service
drop, and extremely complex, like a secondary network. Customers are
connected to distribution systems via service drops. In general service is
typically 1Φ 3-wire 120/240V, 3 Φ 4-wire 120/208V, or 3 Φ 4-wire
277/480V. Customers close to a distribution transformer are able to
have service drops directly connected to transformer secondary
connections. Other customers are reached by routing a secondary main
for service drop connections. These two types of service connections are
shown in Figure.3 systems utilizing secondary mains are characterized
by a small number of large distribution transformers rather than a large
number of small distribution transformers. This can be cost effective for
areas with low load density and/or large lot size, but increases ohmic
losses and results in higher voltage drops. Increased line exposure tends
to reduce reliability while fewer transformers tend to increase reliability.
Figure 1.3 : Service Drops in Distribution System
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16. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Distribution Feeders:
There are three basic types of distribution system designs: Radial,
Loop, or Network. As one might expect, one can use combinations of
these three systems, and this is frequently done. The Radial distribution
system is the cheapest to build, and is widely used in sparsely populated
areas. A radial system has only one power source for a group of
customers. A power failure, short-circuit, or a downed power line would
interrupt power in the entire line, which must be fixed before power can
be restored. A loop system, as the name implies, loops through the
service area and returns to the original point. The loop is usually tied
into an alternate power source. By placing switches in strategic locations,
the utility can supply power to the customer from either direction. If one
source of power fails, switches are thrown (automatically or manually),
and power can be fed to customers from the other source. The loop
system provides better continuity of service than the radial system, with
only short interruptions for switching. In the event of power failures due
to faults on the line, the utility has only to find the fault and switch
around it to restore service. The fault itself can then be repaired with a
minimum of customer interruptions. The loop system is more expensive
than the radial because more switches and conductors are required, but
the resultant improved system reliability is often worth the price.
Network systems are the most complicated and are interlocking loop
systems. A given customer can be supplied from two, three, four, or more
different power supplies. Obviously, the big advantage of such a system
is added reliability. However, it is also the most expensive. For this
reason it is usually used only in congested, high load density municipal
or downtown areas.
1.6 Literature Survey :
In the literature, there are a number of efficient and reliable load
flow solution techniques, such as; Gauss-Seidel, Newton-Raphson and
Fast Decoupled Load Flow. Hitherto they are successfully and widely
used for power system operation, control and planning. However, it has
repeatedly been shown that these methods may become inefficient in the
16
17. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
analysis of distribution systems with high R/X ratios or special network
structures. Accordingly, a number of methods proposed in the literature
[12-28] specially designed for the solution of power flow problem in radial
distribution networks. The methods developed for the solution of ill-
conditioned radial distribution systems may be divided into two
categories.
The first type of methods is utilized by proper modification of existing
methods such as, Newton-Raphson. On the other hand, the second group
of methods is based on forward-backward sweep processes using
Kirchhoff’s Laws or making use of the well-known bi-quadratic equation
which, for every branch, relates the voltage magnitude at the receiving
end to the voltage at the sending end and the branch power flow for
solution of ladder networks. Shirmohammadi et al. [12] had presented a
compensation based
power flow method for radial distribution networks and extended it for
weakly meshed structure using a multi-port compensation technique and
basic formulations of Kirchhoff’s Laws. The radial part is solved by a
straightforward two step procedure in which the branch currents are first
computed (backward sweep) and then the bus voltages are updated
(forward sweep). In the improved version [13], branch power flow was
used instead of branch complex currents for weakly meshed
transmission and distribution
systems by Luo. Baran and Wu [14], proposed a methodology for solving
the radial load flow for analyzing the optimal capacitor sizing problem. In
this method, for each branch of the network three non-linear equations
are written in terms of the branch power flows and bus voltages. The
number of equations was subsequently reduced by using terminal
conditions associated with the main feeder and its laterals, and the
Newton-Raphson method is applied to this reduced set. The
computational efficiency is improved by making some simplifications in
the jacobian. Consequently, numerical properties and convergence rate of
this algorithm have been studied using the iterative solution of three
fundamental equations representing real power, reactive power and
voltage magnitude by Chiang [15]. G. Renato [16] made use of well-
known bi-quadratic equation which, for every branch, relates the voltage
magnitude at the receiving end to the voltage at the sending end and
branch power flow. Only voltage magnitudes are computed, bus phase
angles do not appear in the formulation which was also used by Das et
al. in [17]. Jasmon [18] proposed a load flow technique which, for every
branch, leads to a pair of quadratic equations relating power flows at
both ends with the voltage magnitude at the sending end for the voltage
stability analysis of radial networks. Haque [19] had formulated the load
flow problem of the distribution system in terms of three sets of recursive
17
18. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
equations and analyzed load flow results for various voltage dependent
load models. The effects of various load models on the convergence
pattern of the method are also studied. The effect of voltage-dependency
of load on the results and convergence characteristics of power flow
solution were also analysed [20], where the proposed method was also
based on Kirchhoff’s Laws. Liu et al.[21] had proposed Ratio-Flow method
which is based on forward-backward ladder equation for complex
distribution system by using voltage ratio for convergence control. This
method were applied with standard Newton-Raphson method for complex
distribution systems, which have multiple sources or relatively strong
connected loops with extended long radial feeders including laterals, to
solve the load flow problem. 11 R. Ranjan et al. [22] had proposed a new
method to solve radial distribution networks. They had used simple
algebraic recursive expression of voltage magnitude and the proposed
algorithm used the basic principle of circuit theory. D. Zimmerman and
H. D. Chiang [23] formulated load flow problem as a function of the bus
voltages and equations are solved by Newton’s method. The method has
been compared with classical Newton-Raphson and Forward-Backward
sweep methods by using a number of test cases. Although required
iteration number considerable favoured from classical methods for small
tolerances, no results has been provided on the accuracy of the solution
in terms of bus voltage magnitudes or angles. The results provided in [23]
suggest that undertaken comparisons only cover network structures
which are inherently convergent i.e. Solutions can also be obtained using
classical Newton Raphson method. J.Jerome et al.[25],had proposed
forward-backward substitution method which is based on the Kirchhoff’s
Laws. In backward substitution, each branch current is calculated by
Kirchhoff’s current law
(KCL). Using these currents, the node voltages are calculated by
Kirchhoff’s Voltage Law in forward substitution at each iteration. The
voltage magnitudes at each bus in an iteration are compared with their
values in the previous iteration. If the error is within the tolerance limits,
the procedure is stopped. Ladder network theory shown in ref. [26] is
similar to the Forward-Backward Substitution method. In Ladder
network theory, the currents in each branch are computed by KCL. In
addition to the branch currents, the node voltages are also computed by
KVL in each iteration. Thus magnitude of the swing bus voltage is also
determined. The calculated value of swing bus is compared with its
specified value. If the error is within the limit, the procedure is stopped.
Otherwise, the forward and backward calculations are repeated as in
forward-backward substitution method. The aim of this paper is to
compare the convergence ability of distribution system load flow methods
which are widely used for distribution systems analysis. The method,
18
19. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
analysed in this section, are classical Newton-Raphson method [2], Ratio-
Flow [21], Forward Backward Substitution method [25] and Ladder
Network Theory [26], The convergence ability of methods were also
evaluated for different tolerance values, different voltage levels, different
loading conditions and different R/X ratios, under the wide range
exponents of loads. Algorithms had been implemented with Matlab codes.
12 A few researchers [29–32] had tried to incorporate composite load
model in their algorithms. The most recent of these is the work of Mok et
al. [33], which included composite loads and solves the networks by
ladder network theory. However, their convergence was not efficient and
takes a high number of iterations. Chiang [34] had also proposed three
different algorithms for solving radial distribution networks based on the
method proposed by Baran and Wu .He had proposed decoupled, fast
decoupled & very fast decoupled distribution load-flow algorithms. In fact
decoupled and fast decoupled distribution load-flow algorithms proposed
by Chiang [34] were similar to that of Baran and Wu [l4]. However, the
very fast decoupled distribution load flow proposed by Chiang [ 16] was
very attractive because it did not require any Jacobian matrix
construction and factorisation. Renato [12] had proposed one method for
obtaining a load-flow solution of radial distribution networks. He has
calculated the electrical equivalent for each node summing all the loads
of the network fed through the node including losses and then, starting
from the source node, the receiving-end voltages of all the nodes are
calculated. Goswami and Basu [35] had presented a direct method for
solving radial and meshed distribution networks. However, the main
limitation of their method is that no node in the network is the junction
of more than three branches, i.e. one incoming and two outgoing
branches. Jasmon and Lee [18] had proposed a new load-flow method for
obtaining the solution of radial distribution networks. They have used the
three fundamental equations representing real power, reactive power and
voltage magnitude derived in [35]. They have solved the radial
distribution network using these three equations by reducing the whole
network into a single he equivalent. Das et al. [36] had proposed a load-
flow technique for solving radial distribution networks by calculating the
total real and reactive power fed through any node. They have proposed a
unique node, branch and lateral numbering scheme which helps to
evaluate exact real and reactive power loads fed through any node.
Accordingly, there are a number of reported studies in the literature [17–
28] specially designed for solution of power flow problem in radial
distribution systems (RDS). Methods developed for the solution of ill-
conditioned radial distribution systems may be divided into two
categories. The first group of methods is based on the forward-backward
sweep process 13 for solution of ladder networks. On the other hand, the
19
20. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
second group of methods is utilized by proper modification of existing
methods such as Newton-Raphson.
CHAPTER-2
LOAD FLOW ANALYSIS
20
21. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
2.1 Proposed method:
The load flow of distribution system is different from that of
transmission system because it is radial in nature and has high R/X
ratio. Convergence of load flow is utmost important. Literature survey
shows that the following works had been carried out on load flow studies
of electric power distribution systems. The literature survey of radial
distribution networks has already been presented in Chapter 1 .
In this method of load flow analysis the main aim is to reduce the
data preparation and to assure computation for any type of numbering
scheme for node and branch. If the nodes and branch numbers are
sequential, the proposed method needs only the starting node of feeder,
lateral(s) and sub lateral(s) only. The proposed method needs only the set
of nodes and branch numbers of each feeder, lateral(s) and sub-lateral(s)
only when node and branch numbers are not sequential. The proposed
method computes branch power flow most efficiently and does not need
to store nodes beyond each branch. The voltage of each node is
calculated by using a simple algebraic equation. Although the present
method is based on forward sweep ,it computes load flow of any
complicated radial distribution networks very efficiently even when
branch and node numbering scheme are not sequential.
A 34-node radial distribution networks with constant
power(CP),constant current (CI) and constant impedance (CZ) load
modelling are considered.
2.2 Solution methodology:
21
22. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
1 I(1) 2 I(2) 3 I(3) 4 I(nb) nb
R(1)+j*Q(1) R(2)+jQ(2) R(3)+jQ(3) R(nb-1)+jQ(nb-1)
P(2)+j*Q(2) P(3)+j*Q(3) P(4)+j*Q(4) P(nb)+j*Q(nb)
Fig 2.1. Radial main feeder
|V(1)| ∟δ (1) I(1) |V(2)|∟δ(2)
1 R(1)+j*X(1)
P(2)+j*Q(2)
Fig. 2.2 Electrical equivalent of fig 1
Consider a distribution system consisting of a radial main feeder
only. The one line diagram of such a feeder comprising n nodes and n-1
branches is shown in Fig. 2.1. Fig. 2.2 shows the electrical equivalent of
Fig. 2.1. From Fig. 2.2, the following equations can be written
_________________________(1)
P(2)-j*Q(2)=V*(2)I(1) ____________________________________________(2)
From eqns. 1 and 2 we have
|V(2)|=[{P(2)R(1)+Q(2)X(1)-0.5|V(1)|2)2-- (R2(1)+X2(1))
(P2(2)+Q2(2))}1/2
-(P(2)R(1)+Q(2)X(1)-0.5|V(1)|2)]1/2 ________________ (3)
Eqn. 3 can be written in generalized form
|V(i+1)|=[{P(i+1)R(i)+Q(i+1)X(i)-0.5|V(i)|2)2 - (R2(i)+X2(i))
(P2(i+1)+Q2(i+1))}1/2
-(P(i+1)R(i)+Q(i+1)X(i)-0.5|V(i)|2)]1/2 _____________________ (4)
Eqn. 4 is a recursive relation of voltage magnitude. Since the substation
voltage magnitude |V(1)| is known, it is possible to find out voltage
22
23. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
magnitude of all other nodes. From Fig. 2.2 the total real and reactive
power load fed through node 2 are given by
P(2)= + __________________________________ (5)
Q(2)= +
It is clear that total load fed through node 2 itself plus the load of all
other nodes plus the losses of all branches except branch 1.
LP(1)=(R(1)*[P2(2)+Q2(2)])/(|V(2)|2) _____________________________ (6)
LQ(1)=(X(1)*[P2(2)+Q2(2)])/(|V(2)|2)
Eqn. 5 can be written in generalized form
P(i+1)= + for i=1, 2,……, NB-1 _______________(7)
Q(i+1)= + for i=1, 2,……, NB-1
Eqn. 6 can also be written in generalized form
LP(i)=(R(i)*[P2(i+1)+Q2(i+1)])/(|V(i+1)|2) _____________________________(8)
LQ(1)=(X(i)*[P2(i+1)+Q2(i+1)])/(|V(i+1)|2)
Initially, if LP(i+1) and LQ(i+1) are set to zero for all I, then the initial
estimates of P(i+1) and Q(i+1) will be
P(i+1)= for i=1, 2,……, NB-1 ______________________________(9)
Q(i+1)= for i=1, 2,……, NB-1
Eqn. 9 is a very good initial estimate for obtaining the load flow solution
of the proposed method.
The convergence criteria of this method is that if the difference of real
and reactive power losses in successive iterations in each branch is less
than 1 watt and 1 var, respectively, the solution has converged.
Technique of lateral, node and branch numbering:
23
24. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Fig.3.1 shows single line diagram of a radial
distribution feeder with laterals. First, we will number the main feeder as
lateral 1 (L=1) and number the nodes and branches of lateral 1 (main
feeder). For lateral 1, source node SN(1)=1, node just ahead of source
node LB(1)=2 and end node EB(1)=12. For lateral 1 there are 12 nodes
and 11 branches. Next we will examine node 2 it does not have any
lateral.
Next, we will examine node 3 of lateral 1. It also has one lateral. The
lateral number is 2. For lateral 2, it is seen that source node SN(2)=3,
node just ahead of source node LB(2)=13 and end node EB(1)=16. For
lateral 2 there are 5 nodes including source node (node 3). The remaining
nodes are numbered as 13, 14, 15 and 16. The branch numbers of
lateral 2 is shown inside brackets(.). Next, we will examine node 4, 5. It
does not have laterals. Next, we will examine node 6 of lateral 1. The
lateral numbered as 3. For lateral 3, source node SN(3)=6, node just
ahead of source node LB(3)=17 and end node EB(3)=27. For lateral 3
there are 11 nodes including source node (node 6). The remaining nodes
are numbered as 17, 18, 19,……….., 27. The branch numbers of lateral 2
is shown inside brackets (.). Similarly we have to examine each node of
lateral 1 and lateral, source node, node just ahead of source node, end
node and branch numbering have to be completed by using above
mentioned technique. Details are given in table. 2.
Table1 : Details of the numbering scheme of figure 3.1
Laterals Source node Node just End node
number SN(L) ahead of EB(L)
source node
LB(L)
Lateral 1 1 2 12
Lateral 2 3 13 16
Lateral 3 6 17 27
Lateral 4 9 28 30
Lateral 5 10 31 34
Any numbering each lateral and nodes we follow the steps described
below. Generalized expressions for TP(L) and TQ(L) are given below:
TP(L)= for L=1,2,….NL _________________ (10)
24
25. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
TQ(L)=,j=LB(L)-NN(L)-QL,j.+. for L=1,2,….,NL
Where
NN(1)=EB(1)
NN(2)=EB(2)
…. ….
NN(L)=EB(L)
Now we will define one integer variable F(i),i=1,2,…,NB-1,the meaning of
which is as follows:
From Fig. ,it can be seen that four laterals are connected with different
nodes of lateral 1(main feeder). Laterals are connected with node i.e. two
laterals are connected with node therefore only one lateral is connected
with node i.e. similarly other values of F(i) can easily be obtained. From
Table
Table2 : Non Zero integer values of F(i)
Source node F(i)
SN(L)
3 F(3)=1
6 F(6)=1
9 F(9)=1
10 F(10)=1
It is clear that F(i) is positive only at the source nodes {i=SN(L),L>1}.other
values of F(i) are zeros.
2.3 Explanation of the proposed algorithm:
From Fig. it is seen that for L = 1, total real and reactive power
loads fed through node 2 are TP(1) and TQ(1) (eqn. 10). At any iteration
voltage magnitude of node 2 can easily be obtained by using eqn. 4 {P(2)
= TP(1) and Q(2) = T Q ( 1 ) } . After solving the voltage magnitude of node
2 one has to obtain the voltage magnitude of node 3 and so on. Before
25
26. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
proceeding to node 3, we will define here four more variables which are
extremely important for obtaining exact load feeding through nodes 3, 4,
..., EB(1) of lateral 1 or in general obtaining exact load feeding through
LB(L) + 1, LB(L) + 2, ... ., EB(L) of lateral L. It is seen from the flow chart
(Fig. 6) that
SPL(1) = 0 + PL(2) + LP(2) = PL(2) + LP(2)
SQL(1) = 0 + QL(2) + LQ(2) = QL(2) + LQ(2)
where
SPL(1) = real power load of node 2 which has just been left plus real
power loss of branch 2 which has just been left.
SQL(1) = reactive power load of node 2 which has just been left plus
reactive power loss of branch 2 which has just been left.
Next, we have to obtain the value of K (Fig. 6). In this case K = 0 + F(2)
= 0. K =0 indicates that we have no laterals . After that we have to check
whether F(2) is positive or not? But in this case F(2) < 0. Therefore it will
compute PS(1) and QS(1) (Fig.6)
PS(1)=0.0
QS(1)=0.0
PS(1)=0+ =TP(2)
QS(1)=0+ =TQ(2)
TP(2), TP(NL) and TQ(2), TQ(NL) can easily be computed from eqn. 10 and
P1 = P1 + F(2) = 1 + 0 = 1. Therefore, real and reactive power loads fed
through the node 3 are given as:
P(3) = TP(1) - PS(1) - SPL(1)
= TP(1) - PL(2) - LP(2)
Q(3) = TQ(1) - QS(1) - SQL(1)
= TQ(1) - QL(2) - LQ(2)
26
27. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
After computing P(3) and Q(3), eqn. 4 has to be solved to obtain the
voltage magnitude at node 3. Before obtaining the voltage magnitude of
node 4, computer logic will perform the following computations:
SPL(1)=PL(2)+LP(2)+PL(3)+LP(3)
SQL(1)=QL(2)+LQ(2)+QL(3)+LQ(3)
and k=0+F(3)=0+1=1.
Next it will check whether F(3) is positive or not? But Total real and
reactive loads fed through the node 4 are: F(3) = 1, therefore
P(4) = TP(1) - PS(1) - SPL(1)
PS(1)=0+ = TP(2)
QS(1)=0+ = TQ(2)
P(4)=TP(1)-PS(1)-SPL(1)
=TP(1)-TP(2)-PL(2)-LP(2)-PL(3)-LP(3)
Q(4)=TQ(1)-PQ(1)-SQL(1)
=TQ(1)-TQ(2)-PQ(2)-LQ(2)-QL(3)-LQ(3)
and solve eqn. 4 for obtaining the voltage magnitude of node 4. For
lateral 1 (L = 1, main feeder) similar computations have to be repeated for
all the nodes. At any iteration, after solving the voltage magnitudes of all
the nodes of lateral 1 one has to obtain the voltage magnitudes of all the
nodes of laterals 2, and so on. Before solving voltage magnitudes of all
the nodes of lateral 2 the voltage magnitude of all the nodes of lateral 1 is
stored in the name of another variable, say V1, i.e. I Vl(J) I = 1 V(J) I for J
= P2 to EB(1) (Fig. 6). For lateral 1 (main feeder) P2 = 1 and EB(1) = 12.
For lateral 2, P2=EB(L)+1=12+1=13. L=L+1=1+1=2, K2 = SN(L) =
SN(2) = 3, |V(EB(1))|=|V(K2)| or |V(12)| = |V(3)| and solve the voltage
magnitudes of all the nodes of lateral 2 using eqn. 4. The proposed
computer logic will follow the same procedure for all the laterals. This will
complete one iteration. After that it will compute total real and reactive
power losses and update the loads. This iterative process continues until
the solution converges.
27
28. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
2.4 STATIC LOAD MODELS:
In power flow studies, the common practice is to represent the
composite load characteristic as seen from power delivery points. In
transmission system load flows, loads can be represented by using
constant power load models, as voltages are typically regulated by
various control devices at the delivery points. in distribution systems,
voltages vary widely along system feeders as there are fewer voltage
control devices; therefore, the v-i characteristics of load are more
important in distribution system load flow studies. Load models are
traditionally classified into two broad categories: static models and
dynamic models. Dynamic load models are not important in load flow
studies. Static load models, on the other hand, are relevant to load flow
studies as these express active and reactive steady state powers as
functions of the bus voltages (at a given fixed frequency). These are
typically categorized as follows:
Constant impedance load model (constant z): A static load model
where the power varies with the square of the voltage magnitude. It is
also referred to as constant admittance load model.
Constant current load model (constant I): A static load model where
the power varies directly with voltage magnitude.
Constant power load model (constant p): A static load model where the
power does not vary with changes in voltage magnitude. It is also known
as constant MVA load model.
Exponential load model: A static load model that represents the power
Relationship to voltage as an exponential equation in the following way:
P=Po (V/Vo)a
Q=Qo (V/Vo)b
Where Po and Qo stand for the real and reactive powers consumed
at a reference Voltage Vo. The exponents a and b depend on the type of
load that is being Represented, e.g., for constant power load models
a=b=0, for constant current Load models a=b=1 and for constant
impedance load models a=b=2. It is interesting to note that none of these
loads has a zero exponent, polynomial load model. A static load model
that represents the power-voltage relationship as a polynomial equation
of voltage magnitude. It is usually referred to as the ZIP model, as it is
made up of three different load models: constant impedance (Z), constant
current (I ) and constant power (P). The real and reactive power
characteristics of the ZIP load model are given by
28
29. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
P=Po [ ap(V/V0)2+bp(V/Vo)+cp ]
Q=Qo [ aq(V/V0)2+bq(V/Vo)+cq ]
Where ap+bp+cp=aq+bq+cq=1, and Po and Qo are the real and reactive
Power consumed at a reference voltage Vo. In this paper, three types of
static Load models, i.e., constant power, constant current and constant
impedance, Are considered to demonstrate their effect on voltage
regulation calculations in Distribution systems. The studies presented in
this paper can be readily extended to other load models as well.
29
30. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
2.5 ALGORITHM FOR LOAD FLOW COMPUTATION:
The complete algorithm for load flow calculation of radial distribution
network is shown in below.
Step1 : Read the system voltage magnitude |v(i)|, line parameters and
load data.
Step2 : Read base KV and base MVA.
Step3 : Read total number of nodes nb,
Step4 : compute per unit values of load powers at each node i.e. pl(i)
And ql(i) for i=1, 2, 3,…nb, as well as resistance and reactance
of each branch i.e. r(j) and x(j) for j=1, 2, 3,……..nb-1.
Step5 : By examine the radial feeder network note down the lateral
number l, source node sn(l), node just ahead of source node
lb()l, end node eb(l).
Step6 : Read the nonzero integer value f(i), i.e. whether node consists of
lateral or not. If yes f(i)=1, otherwise f(i)=0, for i=1, 2, 3,…nb
Step7 : Initialize the branch losses lp(i)=0.0, lq(i)=0.0 for i=1, 2, 3,.nb-1
Step8 : set iteration count IT=1, ε(0.0001).
Step9 : compute TP(l) and TQ(l) by using eqn. 10
Step10 : compute TP(1)=sum(TP), TQ(1)=sum(TQ).
Step11 : set the losses ploss(i)=lp(i), qloss(i)=lq(i) for i=1, 2, 3,…..nb-1
Step12 : l=1, p2=1
Step13 : for i=1
Step14 : set k=0, p1=1
Step15 : initialize spl(l)=0.0, sql(l)=0.0, ps(l)=0.0, qs(l)=0.0
30
31. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Step16 : k=k+f(i)
Step17 : If f(i) is greater than zero go to next step otherwise go to step20
Step18 : compute ps(l) and qs(l) by using the formulae are
ps(l)=ps(l)+TP(l+i3), qs(l)=qs(l)+TQ(l+i3).
Step19 : p1=p1+f(i)
Step20 : compute node real power and reactive powers by using eqn. 7
Step21 : solve the eqn. 4 for |v(i+1)|
Step22 : i is incremented by i+1
Step23 : If i is not equal to eb(l) go to next step otherwise go to step26
Step24 : compute spl(l), sql(l) by using eqns.
SPL(l)=SPL(l)+PL(i)+LP(i)
SQL(l)=SQL(l)+QL(i)+LQ(i)
Step25 : Then go to step 16
Step26 : |v1(j)|=|v(j)| for j=p2 to eb(l).
Step27 : If i is not equal to nb then go to next step otherwise go to
step32
Step28 : set k1=eb(l), p2=eb(l+1)
Step29 : l is incremented by l+1.
Step30 : set k2=sn(l)
Step31 : set |v(k1)|=|v(k2)| then go to step step5.
Step32 : compute lp(i), lq(i) by using eqn.8 for i=1, 2, 3,…nb-1
Step33 : compute dp(i) and dq(i) by using eqns
dp(i)=lp(i)-ploss(i)
dq(i)=lq(i)-qloss(i) for i=1, 2, 3,…nb-1
Step34 : If (max |(dp(i))| & max|(dq(i))|) is less than not equal ε go to
next step otherwise go to step36
31
32. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Step35 : IT is incremented by IT+1, then go to step8
Step36 : write voltage magnitudes and feeder losses.
Step37 : stop
32
33. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
FLOW CHART:
START
Read S/S voltage
magnitude |v(i)|, line
parameters and load
data.
Initialize LP(i)=0
LQ(i)=0 for i=1,2…
NB-1
IT=1
Compute TP(L) and
TQ(L) by using eqn.
From (A)
TP(1)=sum(TP)
TQ(1)=sum(TQ
Set PLOSS(i)=LP(i)
QLOSS(i)=LQ(i)
For 1=1,2,…NB-1
Set
L=1,i=1,P2=1
From(B)
33
34. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
K=0,P1=1
Initialize
SPL(L)=0.0,SQL(L)=0.0
PS(L)=0.0,QS(L)=0.0
K=K+F(i)
From (C)
Is
F(i)>0
?
PS(L)=PS(L)+
no
QS(L)=QS(L)+
P1=P1+F(i)
yes
P(i+1)=TP(L)-PS(L)-SPL(L)
34
Q(i+1)=TQ(L)-QS(L)-SQL(L)
35. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Solve eqn.
4 for |
V(i+1)|
i=i+1
SPL(L)=SPL(L)+PL(i)+LP(i)
Is
i==EB(L) SQL(L)=SQL(L)+QL(i)+LQ(i)
yes yes
no
|V1(J)|=|V(J)|
for J=p2 to To (C)
EB(L)
35
36. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Is no
i==NB
K1=EB(L)
yes
Compute LP(i) and LQ(i)
for i=1,2,…NB-1 by
using eqn. 8
p2=EB(L)+1
Compute L=L+1
DP(i)=LP(i)-PLOSS(i)
DQ(i)=LQ(i)-QLOSS(i)
K2=SN(L)
|V(k1)|=|
V(K2)|
IT=IT+1 is max(|DP(i)|
&max|
DQ(i)|)<ε
no To (B)
no
Write voltage
magnitudes and feeder
losses
To (A)
36
stop
37. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
yes
Fig. 2.3 Flow chart for radial distribution network having laterals.
CHAPTER-3
EXAMPLES
One example has been considered to demonstrate the effectiveness of
the proposed method. The first example is 34 node radial distribution
network (nodes have been renumbered with Substation as node 1) shown
in Figure 3.1. Data for this system are available in [9] shown in Appendix
A. Real and reactive power losses of this system for CP, CI, CZ load
modelling is shown in Table 2.1. The minimum voltage occurs at node
number 27 in all cases. Base values for this system are 11 kV and 1
MVA respectively.
● 34
37
38. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Fig. 3.1 : 34 node radial distribution network
● 30 ● 33
● 29 ● 32
● 28 ● 31
1 2 3 4 5 6 7 8 9 10 11 12
S/S ● ● ● ● ● ● ● ● ● ● ●
● 13 ● 17
14 ● ● 18
15 ● ● 19
16 ● 20 ● ● ● ● ● ● ● ●
21 22 23 24 25 26 27
Table 3: Voltages for different static load model.
Node Voltages of Voltages of Voltages of
number constant power constant current constant
load model load model impedance load
model
1 1.0000 1.0000 1.0000
2 0.9940 0.9942 0.9945
3 0.9888 0.9893 0.9897
4 0.9817 0.9825 0.9833
5 0.9756 0.9767 0.9777
6 0.9699 0.9712 0.9725
7 0.9658 0.9673 0.9688
8 0.9636 0.9652 0.9667
9 0.9611 0.9628 0.9644
38
39. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
10 0.9599 0.9617 0.9633
11 0.9595 0.9612 0.9629
12 0.9593 0.9611 0.9628
13 0.9885 0.9889 0.9894
14 0.9882 0.9886 0.9891
15 0.9881 0.9886 0.9890
16 0.9881 0.9885 0.9890
17 0.9654 0.9670 0.9685
18 0.9617 0.9635 0.9652
19 0.9576 0.9596 0.9615
20 0.9543 0.9565 0.9586
21 0.9515 0.9538 0.9561
22 0.9482 0.9507 0.9532
23 0.9455 0.9482 0.9508
24 0.9430 0.9459 0.9486
25 0.9418 0.9447 0.9475
26 0.9413 0.9443 0.9471
27 0.9412 0.9442 0.9470
28 0.9655 0.9670 0.9685
29 0.9653 0.9668 0.9683
30 0.9652 0.9667 0.9682
31 0.9596 0.9613 0.9630
32 0.9594 0.9612 0.9629
33 0.9592 0.9610 0.9627
34 0.9591 0.9609 0.9626
Base voltage=11kv Base MVA=1MVA
Table 4 : Power losses of different static load models.
Type of load model Real power Reactive power
losses (per losses (per unit)
unit)
Constant power load 0.2276 0.0668
Constant current load 0.2066 0.0607
Constant impedance 0.1877 0.0553
load
39
40. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Table 5: voltage regulation for different static load models
Type of load Voltage regulation(in %)
model
Constant power load 6.2497
Constant current load 5.9143
Constant impedance load 5.5996
CHAPTER-4
SUMMARY AND FUTURE SCOPE
40
41. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
Conclusion:
A novel load flow technique, named “FORWARD SWEEPING
METHOD”, has been proposed for solving radial distribution networks. It
completely exploits the radial feature of the distribution network. A
unique lateral, node and branch numbering scheme has been suggested
which helps to obtain the load flow solution of the radial distribution
network. The forward sweeping method always guarantees convergence of
any type of practical radial distribution network with a realistic R/X
ratio.
In this thesis work a method of load flow analysis has been proposed
for radial distribution networks based on the forward sweeping method to
identify the set of branches for every feeder, lateral and sub-lateral
without any repetitive search computation of each branch current.
Effectiveness of the proposed method has been tested by an example 34-
node radial distribution network with constant power load, constant
current load, constant impedance load for each of this example. The
power convergence has assured the satisfactory convergence in all these
cases. The proposed method consumes less amount of memory compared
to the other due to reduction of data preparation. Several Indian rural
distribution networks have been successfully solved using the proposed
forward sweeping method.
This paper demonstrates how voltage regulation calculations in
distribution system vary with different static loads models. Systems with
constant power load models presenting high voltage along a feeder, and
thus high voltages regulation, followed by systems with constants
impedance load models. Hence it is important to choose the load models
more suitable for a given system in order to obtain accurate results.
Future Scope of Work:
The following are the scopes of future work
(a) Fuzzy load-flow analysis.
(b) Load-flow analysis using Genetic Algorithms
41
43. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
1. T. Gonen, Electric Power Distribution System Engineering (McGraw
Hill, New York, 1986).
2. G. T. Heydt, Electric Power Quality, 2nd edn (Stars in a Circle
Publications, West LaFayette, IN, 1991).
3. M. E. El-Hawary and L. G. Dias, ‘Incorporation of load models in load-
flow studies: form of models effects’, IEE Proc. C, 134(1) (1987), 27–
30.
4. P. S. R. Murty, ‘Load modelling for power flow solution’, J. Inst. Eng.
(India), Part EL , 58(3) (1977) 162–165.
5. M. H. Haque, ‘Load flow solution of distribution systems with voltage
dependent load models’, Int. J. Electric Power System Res., 36 (1996),
151–156.
6. T. Van Cutsem and C. Vournas, Voltage Stability of Electric Power
Systems, Power Electronics and Power System Series, Kluwer, 1998.
7. J. D. Glover and M. Sarma, Power System Analysis and Design, 2nd
edn (PWS Publishing Company, Boston, 1993).
8. C. G. Renato, ‘New method for the analysis of distribution networks’,
IEEE T rans. Power Delivery, 5(1) (1990), 391–396.
9. D. Das, H. S. Nagi, and D. P. Kothari, ‘Novel methods for solving radial
distribution networks’, IEE Proc. Generation T ransmission and
Distribution, 141(4) (1994).
10. M. M. A. Salama and A. Y. Chikhani, ‘A simplified network approach
to the var control problem for radial distribution systems’, IEEE T
rans. Power Delivery, 8(3) (1993), 1529–1535.
APPENDIX A :
43
49. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
for i=1:nb-1
lp(i)=0.0;
lq(i)=0.0;
end
t=1;diff=1;diff1=1;
while (diff>0.000001 && diff1>0.000001)
for l=1:u
p1=0;p2=0;q1=0;q2=0;
for j=lb(l):eb(l)
p1=p1+pl(j);
q1=q1+ql(j);
end
for j=lb(l):eb(l)-1
p2=p2+lp(j);
q2=q2+lq(j);
end
tp(l)=p1+p2;
tq(l)=q1+q2;
end
tp(1)=sum(tp);
tq(1)=sum(tq);
for i=1:nb-1
ploss(i)=lp(i);
qloss(i)=lq(i);
end
p2=1;
for l=1:u
k=0;p1=1;
spl(l)=0;sql(l)=0;ps(l)=0;qs(l)=0;
for i=lb(l)-1:eb(l)
if (i<=eb(l)-1)
k=k+f(i);
if (f(i)>0)
for i3=p1:k
ps(l)=ps(l)+tp(l+i3);
qs(l)=qs(l)+tq(l+i3);
end
p1=p1+f(i);
end
p(i+1)=tp(l)-ps(l)-spl(l);
q(i+1)=tq(l)-qs(l)-sql(l);
v(i+1)=sqrt(sqrt((p(i+1)*r(i)+q(i+1)*x(i)-0.5*v(i)^2)^2-
(r(i)^2+x(i)^2)*(p(i+1)^2+q(i+1)^2))-(p(i+1)*r(i)+q(i+1)*x(i)-0.5*v(i)^2));
49
50. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
if ((i+1)~=eb(l))
spl(l)=spl(l)+pl(i+1)+lp(i+1);
sql(l)=sql(l)+ql(i+1)+lq(i+1);
end
end
end
for j=p2:eb(l)
v1(j)=v(j);
end
if (i~=nb)
k1=eb(l);
p2=eb(l)+1;
k2=sn(l+1);
v(k1)=v(k2);
end
end
for i=1:nb
h(i,g)=v1(i);
end
for i=1:nb-1
lp(i)=r(i)*((p(i+1)^2+q(i+1)^2))/(v(i+1)^2);
lq(i)=x(i)*((p(i+1)^2+q(i+1)^2))/(v(i+1)^2);
di(i)=lp(i)-ploss(i);
di1(i)=lq(i)-qloss(i);
end
for i=1:nb-1
lp1(i,g)=lp(i);
lq1(i,g)=lq(i);
end
diff=max(di(1,:));
diff1=max(di1(1,:));
t=t+1;
end
if(g==1)
for i=1:nb
v2(i)=v1(i);
end
end
end
mincp=min(h(:,1));
minci=min(h(:,2));
mincz=min(h(:,3));
cpreg=((v(1)-mincp)/(mincp))*100;
50
51. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
cireg=((v(1)-minci)/(minci))*100;
czreg=((v(1)-mincz)/(mincz))*100;
51
52. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
cireg=((v(1)-minci)/(minci))*100;
czreg=((v(1)-mincz)/(mincz))*100;
51
53. DISTRIBUTION SYSTEM VOLTAGE REGULATION FOR DIFFERENT STATIC LOADS
cireg=((v(1)-minci)/(minci))*100;
czreg=((v(1)-mincz)/(mincz))*100;
51