This document summarizes a research paper that models the performance of different types of Dynamic Voltage Restorers (DVRs) in mitigating balanced and unbalanced voltage sags on distribution systems. The paper presents modeling aspects of several DVR configurations and analyzes their effectiveness in compensating for various voltage sag scenarios through detailed simulation results. It also discusses the capability of DVRs to regulate voltage quality at load terminals during power quality issues like sags, swells and harmonics.
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Modeling and simulation of dynamic voltage restorer for voltage sag mitigatio...IJRRR
Abstract- Power quality deals with utilization of electric energy from the distribution system successfully without interference or interruption. Various factors like interruption in power supply, under voltage, over voltage, unbalanced voltage or current, harmonic distortion, flickering voltage, voltage fluctuation voltage sag etc. result in poor power quality. These power quality related problems can be solved with the help of various custom power devices. Voltage sags are considered to be the most common type of disturbances in the field based on current power disturbances studies. Their impact on sensitive loads is rigorous. The impact ranges from load disruptions to financial losses. In spite of the technical advances in electronics, there are some pieces of equipment that are so sensitive that they are unable to withstand voltage sags. There are many varies methods to mitigate voltage sags, but a Custom Power Supply device is considered to be the most efficient method. This dissertation is the study of Dynamic Voltage Restorer (DVR) which is the most efficient and effective device to protect sensitive equipment against voltage sags. It has low cost, smaller size and it has dynamic response to the disturbance.
Keywords- Voltage sag, DVR, power system, mitigation
Modeling Analysis& Solution of Power Quality Problems Using DVR & DSTATCOMijsrd.com
A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a disoperation of end use equipment. Utility distribution networks, sensitive industrial loads, and critical commercial operations all suffer from various types of outages and service interruptions which can cost significant financial loss per incident based on process down-time, lost production, idle work forces, and other factors. With the restructuring of Power Systems and with shifting trend towards Distributed and Dispersed Generation, the issue of Power Quality is going to take newer dimensions. The aim therefore, in this work, is to identify the prominent concerns in the area and thereby to recommend measures that can enhance the quality of the power, keeping in mind their economic viability and technical repercussions. In this paper electromagnetic transient studies are presented for the following two custom power controllers: the distribution static compensator (DSTATCOM), and the dynamic voltage restorer (DVR). Comprehensive results are presented to assess the performance of each device as a potential custom power solution.
Sag mitigation in distribution system by using Dynamic voltage Restorer (DVR)IJERA Editor
Power quality is most important concern in the current age. It’s now a day’s necessary with the refined devices, where performance is very perceptive to the quality of power supply. Power quality crisis is an incidence manifest as a typical voltage, current or frequency that results in a failure of end use equipments. One of the major crises dealt here is the power sag. Perceptive industrial loads and distribution networks suffer from different types of service interruptions and outages which results in a major financial loss. To improve the power quality, custom power-devices are used. The device considered in this work is Dynamic Voltage Restorer. This paper shows modelling, analysis and simulation of a DVR test systems using MATLAB.
I have considered single line to ground fault for linear load. The role of DVR is to “compensate load voltage” is examined during the different fault conditions like voltage sag, single phase to ground faults.
Voltage sag mitigation using supercapacitor based dynamic voltage restorereSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Research Inventy : International Journal of Engineering and Scienceresearchinventy
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Modeling and simulation of dynamic voltage restorer for voltage sag mitigatio...IJRRR
Abstract- Power quality deals with utilization of electric energy from the distribution system successfully without interference or interruption. Various factors like interruption in power supply, under voltage, over voltage, unbalanced voltage or current, harmonic distortion, flickering voltage, voltage fluctuation voltage sag etc. result in poor power quality. These power quality related problems can be solved with the help of various custom power devices. Voltage sags are considered to be the most common type of disturbances in the field based on current power disturbances studies. Their impact on sensitive loads is rigorous. The impact ranges from load disruptions to financial losses. In spite of the technical advances in electronics, there are some pieces of equipment that are so sensitive that they are unable to withstand voltage sags. There are many varies methods to mitigate voltage sags, but a Custom Power Supply device is considered to be the most efficient method. This dissertation is the study of Dynamic Voltage Restorer (DVR) which is the most efficient and effective device to protect sensitive equipment against voltage sags. It has low cost, smaller size and it has dynamic response to the disturbance.
Keywords- Voltage sag, DVR, power system, mitigation
Modeling Analysis& Solution of Power Quality Problems Using DVR & DSTATCOMijsrd.com
A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a disoperation of end use equipment. Utility distribution networks, sensitive industrial loads, and critical commercial operations all suffer from various types of outages and service interruptions which can cost significant financial loss per incident based on process down-time, lost production, idle work forces, and other factors. With the restructuring of Power Systems and with shifting trend towards Distributed and Dispersed Generation, the issue of Power Quality is going to take newer dimensions. The aim therefore, in this work, is to identify the prominent concerns in the area and thereby to recommend measures that can enhance the quality of the power, keeping in mind their economic viability and technical repercussions. In this paper electromagnetic transient studies are presented for the following two custom power controllers: the distribution static compensator (DSTATCOM), and the dynamic voltage restorer (DVR). Comprehensive results are presented to assess the performance of each device as a potential custom power solution.
Sag mitigation in distribution system by using Dynamic voltage Restorer (DVR)IJERA Editor
Power quality is most important concern in the current age. It’s now a day’s necessary with the refined devices, where performance is very perceptive to the quality of power supply. Power quality crisis is an incidence manifest as a typical voltage, current or frequency that results in a failure of end use equipments. One of the major crises dealt here is the power sag. Perceptive industrial loads and distribution networks suffer from different types of service interruptions and outages which results in a major financial loss. To improve the power quality, custom power-devices are used. The device considered in this work is Dynamic Voltage Restorer. This paper shows modelling, analysis and simulation of a DVR test systems using MATLAB.
I have considered single line to ground fault for linear load. The role of DVR is to “compensate load voltage” is examined during the different fault conditions like voltage sag, single phase to ground faults.
Voltage sag mitigation using supercapacitor based dynamic voltage restorereSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
STATE OF THE ART: DYNAMIC VOLTAGE RESTORER FOR POWER QUALITY IMPROVEMENTecij
Improved and controlled power quality is one of the essential and fundamental need in any power driven industry for optimum utilization of resources. However critical problems in power quality have been recognized such as sags, swells, harmonic distortions and other interruptions. Out of these sags and swells
are predominantly found and have severe impact on the electrical devices or electrical machines and therefore needs to be compensated at an earliest to ensure any mal-operation or failure. To crack these problems custom power devices are used like unified power-quality conditioner (UPQC), distributionSTATCOM (DSTATCOM) and dynamic voltage restorer (DVR). The DVR is a one of the custom power device used for the compensation of voltage sag and swell with an advantage of active/reactive power control. A major volume of literature reported in past several years on different configurations of DVR and different control technique used in it. In context of this a detailed review on DVR has been presented with different possible power circuit topologies and control techniques available to reconcile these power quality issues. This review article will contribute in better selection of control strategy and power circuit for optimum performance of DVR for a particular requirement. Also it presents a very helpful investigation for the researcher in this field.
Analysis of Total Harmonic Distortion (THD) Level of Distribution Network Usi...IJERA Editor
The modern sensitive, Non-linear and sophisticated load affects the power quality. Dynamic Voltage Restorer (DVR) provides the fast, flexible and efficient solution to improve the power quality for such distribution network [8]. The active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operations are the major source of affecting power quality. The intent of this paper is to demonstrate the improvements obtained with DVR in power system network using MATLAB/SIMULINK. In this paper, an overview of the DVR, its functions, configurations, components, control strategies are reviewed. The Simulation results are presented to illustrate the performance of DVR in Total Harmonic Distortion (THD). The results showed clearly the performance of using DVR in improving THD level.
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.
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.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
STATE OF THE ART: DYNAMIC VOLTAGE RESTORER FOR POWER QUALITY IMPROVEMENTecij
Improved and controlled power quality is one of the essential and fundamental need in any power driven industry for optimum utilization of resources. However critical problems in power quality have been recognized such as sags, swells, harmonic distortions and other interruptions. Out of these sags and swells
are predominantly found and have severe impact on the electrical devices or electrical machines and therefore needs to be compensated at an earliest to ensure any mal-operation or failure. To crack these problems custom power devices are used like unified power-quality conditioner (UPQC), distributionSTATCOM (DSTATCOM) and dynamic voltage restorer (DVR). The DVR is a one of the custom power device used for the compensation of voltage sag and swell with an advantage of active/reactive power control. A major volume of literature reported in past several years on different configurations of DVR and different control technique used in it. In context of this a detailed review on DVR has been presented with different possible power circuit topologies and control techniques available to reconcile these power quality issues. This review article will contribute in better selection of control strategy and power circuit for optimum performance of DVR for a particular requirement. Also it presents a very helpful investigation for the researcher in this field.
Analysis of Total Harmonic Distortion (THD) Level of Distribution Network Usi...IJERA Editor
The modern sensitive, Non-linear and sophisticated load affects the power quality. Dynamic Voltage Restorer (DVR) provides the fast, flexible and efficient solution to improve the power quality for such distribution network [8]. The active power, reactive power, variation of voltage, flicker, harmonics, and electrical behavior of switching operations are the major source of affecting power quality. The intent of this paper is to demonstrate the improvements obtained with DVR in power system network using MATLAB/SIMULINK. In this paper, an overview of the DVR, its functions, configurations, components, control strategies are reviewed. The Simulation results are presented to illustrate the performance of DVR in Total Harmonic Distortion (THD). The results showed clearly the performance of using DVR in improving THD level.
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.
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.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
Qualitative Chemistry Education: The Role of the TeacherIOSR Journals
Abstract: This paper discussed the role of a chemistry teacher towards improving the quality of education in Nigeria. The decline in the quality of education has been attributed to many factors. Some of these factors are unqualified teachers, examination malpractice,, lack of practical skills, method of classroom instruction, to mention but a few. The role of a chemistry teacher among others is to change the method of classroom instruction from lecture method to innovative learning strategy such as cooperative learning and concept mapping, and to make use of improvised materials in the absence of standard equipments . It also examine the problems associated with the fall in quality of education. Finally it is recommended that Government should ensure that adequate funds are released to train science teachers, since teachers are the main determinant of quality in Education.
Surface Morphological and Electrical Properties of Sputtered Tio2 Thin FilmsIOSR Journals
Titanium dioxide films were formed on quartz and crystalline p-Si (100) substrates by DC reactive magnetron sputtering method. Pure titanium target was sputtered at a constant oxygen partial pressure of 5x10-2 Pa, and at different sputtering powers in the range 80 – 200 W. The as-deposited films were annealed in air for 1 hour at 1023 K. The deposited films were characterized by studying the surface morphology by atomic force microscopy (AFM), electrical and dielectric properties from current-voltage and capacitance-voltage measurements. Atomic force micrographs of the films showed that the Rrms and Ra increased with the increase of sputter power from 80 to 200 W. The leakage current density was increased by increasing the sputtering power.
50 Hz Frequency Magnetic Field Effects On Pseudomonas Aeruginosa And Bacillus...IOSR Journals
The effect of electromagnetic field of different intensities on Pseudomonas aeruginosa (as gram-negative
bacteria) and Bacillus subtilis (as gram-positive bacteria) was investigated to find out the effective magnetic field strength that alters the running physiological processes of every microorganism. Equal volumes of P. aeruginosa and B. subtilis suspensions were exposed for one hour at their maximum rate of active growth to the electromagnetic field (2 - 10 mT, 50 Hz). The results indicated that no remarkable differences were found in the growth of exposed P. aeruginosa. Moreover, a remarkable inhibition in the growth of exposed relative to unexposed B. subtilis cells was achieved at (4 mT) as compared with other intensities which may indicate that this magnetic field induction had a great effect on the biological activity of the cells, so more investigations were made at this magnetic field induction. Remarkable changes in the growth characteristics could be easily detected as the absorbance decreased which indicate a decrease in the cells number and consequently an
inhibition case for the bacteria. Also, the antibiotic sensitivity test of B. subtilis cells indicated either inhibition or stimulation case for the bacteria depending on the drug mode of action
Membrane Stabilizing And Antimicrobial Activities Of Caladium Bicolor And Che...IOSR Journals
The crude methanol extracts of whole plant of Caladium bicolor (Aiton) Vent. and leaf of Chenopodium album L. as well as their pet-ether, carbon tetrachloride, chloroform and aqueous soluble fractions were evaluated for membrane stabilizing and antimicrobial activities. At concentration 1.0 mg/ml, the carbon tetrachloride soluble fraction of C. bicolor inhibited 43.92±1.63% and 38.08±0.83 % hypotonic solution and heat induced haemolysis of RBCs, respectively. Among the extractives of C. album, the aqueous soluble fraction inhibited 47.11±0.49 % and 36.73±0.76 % hypotonic solution and heat induced haemolysis of RBCs as compared to 72.79 % and 42.12 % by acetyl salicylic acid (0.10 mg/ml), respectively. C. bicolor test samples demonstrated zone of inhibition ranging from 6.0 to 20.0 mm. The chloroform soluble fraction showed the highest zone of inhibition (20.0 mm) against Staphylococcus aureus. The test samples of C. album displayed zone of inhibition ranging from 7.0 to 13.0 mm. The highest zone of inhibition (13.0 mm) was showed by the chloroform soluble fraction against Salmonella paratyphi
IOSR Journal of Humanities and Social Science is an International Journal edited by International Organization of Scientific Research (IOSR).The Journal provides a common forum where all aspects of humanities and social sciences are presented. IOSR-JHSS publishes original papers, review papers, conceptual framework, analytical and simulation models, case studies, empirical research, technical notes etc.
Enhancement of Power Quality Problem by Using Dynamic Voltage RestorerAM Publications
Dynamic voltage restorers (DVRs) are used to protect sensitive loads from the effects of voltage sags on the
distribution feeder. This paper presents and verifies a novel voltage sag detection technique for use in conjunction
with the main control system of a DVR. In all cases it is necessary for the DVR control system to not only detect the
start and end of a voltage sag but also to determine the sag depth and any associated phase shift. The DVR, which is
placed in series with a sensitive load, must be able to respond quickly to a voltage sag if end users of sensitive
equipment are to experience no voltage sag. The DVR can restore the load voltage within few milliseconds. A control
technique based on a proportional–integral (PI) controller and a selective controller is used. The controller is
designed in a synchronously-rotating reference frame. In fact, three independent controllers have been used to tackle
balanced and unbalanced voltage supplies. Simulation results using ‘MATLAB SIMULINK’ Sim Power System
Toolbox is presented to illustrate the principle and performance of a DVR operation in load voltage compensation.
Mitigation of Voltage Sag/Swell using Custom Power Devices with SMES System i...Editor IJMTER
Any power problem noticed in voltage, current or frequency deviations that results in
misoperation of customer or end user equipment. The new method of dynamic voltage restorer with
SMES is proposed to protect consumers load from tripping .The DVR can effectively inject the
voltage to the power lines. To improve the performance of DVR the superconducting magnet is
selected as the energy storage unit. The compensation of the voltage sag, swell by short period of
voltage injection. SMES based DVR has been used to improve the performance of power system. It
is having high power rating with maximum efficiency than any other energy storage devices. It
restores line voltage to its nominal value within few milliseconds. Most of the power quality
problems are voltage sag, swell, interruption, transient, fluctuation, etc.. Among those power quality
problem voltage sag is severe one. So it is analyzing and mitigated using custom power device and
SMES system using MATLAB SIMULINK in proposed system.
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.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Optimization Technique for Power Quality Improvement using DSTATCOM Neural Ne...ijtsrd
As the power demand has been increasing rapidly, power generation and transmission are being affected due to limited resources, environmental restrictions and other losses. soft computing the techniques of correcting the supply voltage sag, swell and interruption in a distributed system. At present, a wide range of very flexible controllers, which capitalize on newly available power electronics components, are emerging for custom power applications. Power electronic based equipment aimed at enhancing the reliability and quality of power flows in low voltage distribution networks. A control algorithm is used for the extraction of the fundamental weighted value of active and reactive power components. Using digital signal processor the DSTATCOM is developed and its performance of DSTATCOM is found to be satisfactory for various types of loads. Hareram Mishra | Manju Gupta | Dr. Anuprita Mishra "Optimization Technique for Power Quality Improvement using DSTATCOM (Neural Network Approach) – A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-5 , August 2021, URL: https://www.ijtsrd.com/papers/ijtsrd45219.pdf Paper URL: https://www.ijtsrd.com/engineering/other/45219/optimization-technique-for-power-quality-improvement-using-dstatcom-neural-network-approach- – -a-review/hareram-mishra
1. IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)
e-ISSN: 2278-1676 Volume 4, Issue 6 (Mar. - Apr. 2013), PP 01-09
www.iosrjournals.org
Modelling of Dynamic Voltage Restorer against Balanced and
Unbalanced Voltage Sags in Distribution systems
H. Lakshmi
Electrical and Electronics Engineering, Kakatiya University, Warangal, India.
Abstract: The Dynamic Voltage Restorer (DVR) is used to regulate the voltage at the load terminals from
various power quality problems like sag, swell, harmonics, unbalance etc. in supply voltage. This paper
presents modelling aspects of several types of Dynamic Voltage Restorer (DVR) working against various
voltage sags by simulation. Dynamic voltage restorers (DVRs) are used to protect sensitive loads from the
effects of voltage sags on the distribution feeder. Significant simulation results show that these several types of
the modelled device can work very well against balanced and/or unbalanced voltages caused by faults in a
distribution system. Detailed analyses illustrate that with suitable parameter setting these devices can deal with
different levels of voltage sag severity. In addition, appropriate ways to obtain a good quality output voltage by
a DVR during voltage sag is also presented. It then provides analyses of working performance of the device,
including capability and quality of compensation.
Index Terms- Dynamic Voltage Restorer (DVR), Balanced and unbalanced faults, Compensation capability,
Power quality sag severity, voltage sag.
I. Introduction
Power quality (PQ) is a term which has captured increasing attention in power engineering within the
recent years. For most of the electric power engineers, the term refers to a certain sufficiently high grade of
electric service. Usually the term quality refers to maintaining a sinusoidal waveform of bus voltages at rated
voltage and frequency [1].
One of the fundamental challenges facing utility and working staff is the need to become familiar with
and stay informed about issues dealing with power quality. Power suppliers and also the customers are going to
find a solid background in power quality not only useful, but necessary too, for continued productivity and
competitiveness. These facts are supported by the utility industry which undergoes restructuring and as
customers find their service needs changing with increased use of equipment and processes more susceptible to
power system disturbances.
Power quality is a growing concern for a wide range of customers. Industrial customers can experience
interruptions of important processes during momentary voltage sags associated with faults within the utility
system [2]. Commercial customers are installing high efficiency lighting and electronic office equipment,
resulting in higher harmonic levels in the buildings. These harmonic sources cause excessive neutral currents
and transformer overheating. Even residential customers are concerned about surge protection for sensitive
electronics in the home and the impact of momentary interruptions on their electronic equipment.
Power quality within the electric distribution system is a growing concern. Customers require higher
quality service due to more sensitive electronic and computer-controlled loads. Capacitor switching events and
voltage sags associated with remote faults that never caused problems in the past, now cause equipment tripping
and even failures within customer facilities. Also, customer loads are generating increasing amounts of
harmonic currents that can be magnified on the distribution system due to resonance conditions [3].
As technology becomes more advanced, equipment has become more sensitive to fluctuations in
voltage along the distribution line. New equipment that increases productivity for a plant may also cause power
quality problems for other equipment down the line [4]. Power quality is now viewed from a systems
perspective rather than as an isolated instrument problem. Understanding the entire scope of the problem helps
in identifying the solution and preventing future occurrences.
The existence of disturbances requires analysis, monitoring and taking measures to ensure the quality
of electricity. Therefore, disturbances are those that significantly reduce the quality of electricity affecting the
generation, trans-mission and distribution process, but also the electricity consumption [2].
Voltage is the main qualitative element that conditions the proper functioning of the receptor. That is why the
voltage quality practically defines the power quality. The paper is focusing on the power quality monitoring in
case of an important substation within the Romanian Power System.
One of the major concerns in electricity industry today is power quality problems to sensitive loads.
This is due to the advent of a large numbers of sophisticated electrical and electronic equipment, such as
computers, programmable logic controllers, variable speed drives, and so forth. The use of these equipment’s
www.iosrjournals.org 1 | Page
2. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
very often requires power supplies with very high quality. Voltage sag, which is a momentary decrease in rms
voltage magnitude in the range of 0.1 to 0.9 per unit (p.u.) [5], is considered as the most serious problem of
power quality. It is often caused by faults in power systems or by starting of large induction motors. It can
interrupt or lead to malfunction of any electric equipment which is sensitive to voltage variations. It occurs more
frequently than any other power quality phenomenon does. Therefore, the loss resulted due to voltage sag
problem for a customer at the load-end is huge.
Dynamic voltage restorer (DVR) and static compensator (STATCOM) are recently being used as the
active solution for voltage sag mitigation
These system-equipment interface devices are commonly known as custom power devices [6], in which DVR is
a powerful one for short-duration voltage compensation. Unlike the STATCOM which connects to the load in
parallel, the DVR is connected in series with the load hence it possesses some certain advantages.
For example, during power disturbances DVR installed in front of a critical load will appropriately
provide correction to that load only. It is noteworthy that during normal operation due to the series connection a
DVR may have to provide a small amount of voltage drop mainly at the coupling transformer. Also DVR cannot
provide compensation during full power interruptions.
.
II. Voltage Sags
Voltage sags are one of many power quality related problems the industrial process sector has to face
[7], [8], though sags are one of the most severe.
Voltage sags are defined as short duration reductions in the rms supply voltage that can last from a few
milliseconds to a few cycles, with typical dip depths ranging from 0.9 to 0.5 pu of a 1-pu nominal. It has been
shown that year on year voltage sags cause extensive disruption to the industrial process sector in terms of
production loss [7], [9], which make them a particularly important area.
There are various solutions to this problem, examples being: Designing inverter drives for process
equipment to be more tolerant of voltage fluctuations or the installation of voltage correction devices. It has
already been shown [7] that for customers of large loads, from the high kilowatt to the low
megawatt range, a good solution is the installation of a dynamic voltage restorer (DVR); see Fig. 1.
A DVR is primarily for use at the distribution level, where the basic principle is to inject a voltage in
series with the supply when an upstream fault is detected. Loads connected downstream of the DVR are thus
protected from any voltage sags caused by faults elsewhere on the network.
The location of the DVR, in terms of the connection arrange-ment of upstream transformers (typically ) and
the type of protection it is to offer to potentially sensitive loads, is a major factor when determining the type of
inverter control required. The main DVR control used in conjunction with the sag detection techniques presented in
this paper utilizes a type a vector control that only considers the positive and negative sequence information in the
supply. The DVR is located downstream of a delta-star distribution transformer (Fig. 1), thus eliminating the need to
control the zero sequence.
III. Dvr Against Balanced Volatge Sags
A. Modelling in PSCAD
This section will briefly highlight one way of modelling a DVR in PSCAD against balanced voltage
sags based on published literature and show the result of mitigation obtained.
There are typically four main components to model a DVR
[3]:
• Coupling transformer
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3. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
• DC voltage source
• Multi-pulse bridge inverter
• Control system
A typical DVR built in PSCAD and installed into a simple power system to protect a sensitive load in a
large radial distribution system [10] is presented in Fig. 2. Its control system block diagram is shown in Fig. 3.
The coupling transformer with either a delta or wye connection on the DVR side is installed on the line in
front of the protected load. Filters can be installed at the coupling transformer to block high frequency
harmonics caused by DC- to-AC conversion to reduce distortion in the output [11]. The DC voltage source is an
external source supplying DC voltage to the inverter to convert to AC voltage. The optimisation of the DC
source can be determined during simulation with various scenarios of control schemes, DVR configurations,
performance requirements, and voltage sags experienced at the point DVR is installed.
The inverter is a six-pulse gate turn off (GTO) thyristor controlled bridge. Currents will follow in different
directions at outputs depending on the control scheme, eventually supplying AC output power to the critical load
during power disturbances. The control of this bridge is indeed the control of thyristor firing angles. Time to
open and close gates will be determined by the control system. There are several methods for controlling the
inverter. To model a DVR protecting a sensitive load against only balanced voltage sags, a simple method of
using the measurement of three-phase rms output voltage for controlling signals can be applied. Amplitude
modulation (AM) is then used. In addition, to provide appropriate firing angles to thyristor gates the switching
control using pulse width modulation (PWM) technique and interpolationfiring [6] is employed.
Fig. 3 DVR Control system block diagram
The following two figures illustrate two different levels of voltage sags that the DVR works with. Each figure
shows the rms voltages before and after DVR is connected during voltage sag. As can be clearly seen,
irrespective of the voltage sag levels the output voltages recover back closely to reference value, which means
that the DVR can cope well with voltage sag in both cases.
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4. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
When the actual load rms voltage is set higher than the reference value, DVR also works to recover it back. In
other words DVR should cope with voltage swell as well.
Various simulations showed an excellent performance of this DVR to work against balanced voltage sags and
swells. The outstanding problem is that this type of DVR can only deal with balanced voltage sags.
IV. Dvr Against Balanced And Unbalanced Voltage Sags
A. General
Unbalanced voltage sags are very common in distribution systems. Voltages sags are normally caused
by remote faults, either within the distribution systems or downward from transmission lines. While the three
phase balanced fault is often seen as the worst case, it seldom occurs. The most frequent types of faults include
Single phase to ground fault (SLGF) and Line to line fault (LLF), which can be grounded or non-grounded. In
distribution systems 95% of faults are unbalanced type . They result in unbalanced sags.
In the previous section the DVR detects 3-phase rms voltage of the critical load and then employs
PWM technique to control the firing of GTO’s to pump up DC voltage to all three phases of load
B. Mitigation Result
An almost worst-case fault (local, three-phase-to-ground, and with a small impedance) by lightning
strikes was made as shown in Fig.2. The line impedance has been taken out for simulation comparison purposes,
which does not have any effect to the observed result. The load is a fixed load and not a motor type.
To satisfy these three criteria rms voltages can still be measured for differential control signals but they
have to be obtained from single-phase rms measurement not from three-phase. The control signals will be
separately made for three phases A, B, and C. Besides, modification of DVR inverter bridge and transformer
connection should be made and then return without affecting the other two phases. It is noted that to maintain an
equal injecting voltage to each phase, the same value of DC voltage at each half of the source would be
required. In Fig. 7 instead of having only one three-phase rms voltage three separate line-to-neural (L-N) values
are now used for firing control input. Three groups of GTO’s are now working independently from each other’s.
They start firing in case their corresponding phase rms voltage is different from one. When all the phase
voltages of the load reach to desired value the control system stays at stable condition. Other properties of the
DVR shown in section I are kept unchanged. Consequently, the three criteria for DVR working in both
unbalanced and balanced voltage sags are obtained. Result of mitigation against various voltage sags are shown
in Figs. 8,9 and 10 accordingly. Most importantly, the changes should not affect the performance of the DVR
against balanced sags described previously because the objective of building DVR is that it should be able to
deal with all kinds of voltage sags.
Two methods of coupling transformer configuration were investigated: a wye-connected with
grounding point and a delta-connected between phases. To adapt to each of these methods the control systems
were appropriately amended. In fact, two different single-phase rms voltage detection schemes were established
for each method. One is a detection of voltages between line to neutral for the first and the other is that between
line to line for the second respectively. The following part will describe configuration of the wye-connected
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5. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
method and its results of voltage sag compensation. Three different types of faults with the same fault
impedance for comparison purposes will be created in the order: SLGF, LLF (grounded) and three-phase-to-
ground fault.
B. The Wye-connected DVR
The connection diagram of DVR in PSCAD is shown in Fig.6. Its block diagram of the modulating
signals in control system is shown in Fig.7.
In Fig. 6 the transformer is wye-connected with a common connection to the midpoint of the DC source. This
allowsthatcurrentwillpumpintoeachphasethrougheachpairofGTOvoltage three separate line-to-neural (L-N)
values are now used for firing control input. Three groups of GTO’s are now working independently from each
other’s. They start firing in case their corresponding phase rms voltage is different from one. When all the phase
voltages of the load reach to desired value the control system stays at stable condition. Other properties of the
DVR shown in section I are kept unchanged. Consequently, the three criteria for DVR working in both
unbalanced and balanced voltage sags are obtained. Result of mitigation against various voltage sags are shown
in Figs. 8,9 and 10.
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6. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
In Fig. 8, a fault causes rms voltage (phase A) down to about 80%. As can be seen, the rms voltage of the
protected
load stays the same at around unity. The other healthy phase voltages which are not shown here still remain
constant. Fig. 8 shows that the line-to-line fault results in a more severe voltage sag (down to about 65%,
phase A), compared to that of single phase. Regardless of the sag magnitude critical load voltage notices a
good compensation. Meanwhile with the worst three-phase voltage sag down to half of the nominal value
critical load voltage the mitigation equipment still provides a good compensation. This newly simulated
DVR shows a similar performance for voltage sag compensation with that of the DVR which uses the three-
phase rms measurement method. The response time of this DVR with three phase voltage measurement is a
bit slower than the previous one. Still this detection and compensation time to increase rms voltage up
to desired value is within couple of cycles, proving that DVR can work fast enough that would not result
in equipment trouble if any severe sag occurs.
As can be seen single-phase monitoring method gives a less stable rms voltage curve compared to the
three-phase case making it difficult to keep an appropriate signal for control. That involves the rms
smoothing time constant, which is a constant interval time applied for detection of a considerable differential
signal to control the compensation process. This value on the one hand must be small enough for the system to
be able to detect voltage sags. On the other hand the penalty is a huge fluctuation in rms value record that can
lead to wrong differential signal for firing control.
By applying extensive simulations when varying this detection time in PSCAD it can be concluded that
the method can be satisfactorily employed for DVR using in systems with three phase balanced sags requiring
measuring the three-phase rms voltage. Besides, the method can also be applied for systems with
unbalanced sags using single-phase rms voltage measurement. In the second case appropriate modifications
may need to be done to keep the latter to cope with worst case scenarios of voltage sag.
IV. Analysis Of Dvr Compensation Capability & Quality Performance
In a DVR, there are two main considerations in its working performance: the compensation capability
and the output voltage quality. In a STATCOM, there is some influence of the capacitor size on its performance,
including distortion . It is revealed by simulation that the value of the DC source voltage has also some side-effect
as distortion to the output waveform. In addition, the severity of sag decides whether or not the DVR with that set
value of DC voltage is capable of compensating. In other words, there are two main factors relating to the
capability and performance of DVR working against voltage sags in a certain power system: the sag severity level
and the total harmonic distortion (THD) introduced to protected load. Both of these in turn are mainly decided
by the DC source. The study of relation among these three factors enables to select appropriate parameters for
DVR to cope with worst-case scenarios of voltage sag. Thus, in this section, an analytical method of examining the
changes of harmonic distortion and compensation capability according to the changes of DC source voltage is
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7. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
presented. Based on that, considerations on DVR parameter setting and voltage sag compensation strategies can be
addressed.
A. Compensation Capability
By definition [1], a value of rms voltage recovery greater than 90% nominal value is acceptable. The
issue of how much improvement in rms voltage after compensation is also dependent on the DC voltage
value. For example, the sag in the above case is corresponding to a new curve of load voltage (E802rms) as
shown in Fig. 11
Fig. 11 Improvement in voltage sag compensation
Apparently, the load voltage value goes up to about 95%, which satisfies the above criterion. This curve would
change if the DC source value is changed too.
B. Simulation Results
In this work, the DVR against balanced voltage sags described in section II is applied. For the
two types described in section III, the same procedures can be done. Various three-
phase faults with different sag severity are created. First, a constant value of DC source voltage is set and the
changes in total harmonic distortion and load rms voltage due to voltage sag severity changes is recorded.
Then, it is repeated for a number of other DC voltage values. The results simulated are summarized in tables I
and II.
The two tables correspond to data recorded in two different severe sags. In each table, the first column
shows variation of DC source. The second and the third columns record the values of voltage after
compensation and THD according to this DC source variation. It is noted that for comparison purposes,
the definition of voltage sag by how many percent is now applied. Moreover, THD in percentage is a constant for
each case. This is because the average value of THD is applied. In fact, in Fig. 10, THD is actually not
a constant value before, during and after fault. However, the increase in THD at the points where the fault
occurs and cleared is quite short. Meanwhile, harmonic is more significant when it appears in a fairly
longer time, as it is the factor which mainly causes non useful heat dissipation in load equipment and so forth.
The last two columns in each table present the derived thresholds that voltage sag and THD must meet. Similar
tables of results can be obtained for other voltage sags having different severity. The results in tables I and
II are converted into two graphs shown in Fig.12 and Fig.13.
Table I A severe voltage sag - voltage drops by 50%
DC Load THD Sag
THD
voltage voltage threshold threshold
(kV): (%) (%) (%) (%)
0 50 0 10 5
5 35 4 10 5
10 20 2.5 10 5
15 10 2 10 5
20 6 2 10 5
25 4 3 10 5
30 2 4 10 5
35 0 5 10 5
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8. Modelling of Dynamic Voltage Restorer against Balanced and Unbalanced Voltage Sags in
Table II. Very severe voltage sag - voltage drops by 75%
DC Load THD Sag
THD
voltage voltage threshold threshold
(kV): (%) (%) (%) (%)
0 75 0 10 5
5 60 8 10 5
10 45 10 10 5
15 30 9 10 5
20 15 3.5 10 5
25 9 3 10 5
30 6 4 10 5
35 5 5 10 5
D. Result Analysis
The results shown in Tables I and II are converted into two corresponding graphs shown in Fig. 12 and
Fig. 13.
Fig. 12 The severe voltage sag - voltage drops by 50%
Fig. 13 The very severe voltage sag - voltage drops by 75%
As can be seen, the graphs give a very clear explanation for which range of DC value source that would
satisfy the DVR operation requirement in each case. Depending on the worst-case level of the sag in the system
that DVR is required to be capable to compensate, the DC voltage value can be appropriately selected.
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For example, if it is required that DVR should be robust enough to cope with balanced sag with value down to
50% at the point of installation; it is corresponding to the case in the first graph. In this one, the sag threshold
(10%) cuts the load voltage sag curve at a point corresponding to a DC voltage value of 15kV. It is noticed
that the curve is relatively linear. These mean that with any value DC voltage value greater 15kV, the DVR is
able to cope with such severe voltage sag (50%). Similarly for the harmonic curve, a less than 35kV DC
voltage would result in a compensation in which harmonic distortion is within limit (5%). Thus, to cope with
the above sag compensation and harmonic distortion requirements, a DC source voltage raging from 15kV to
35kV should be selected for this DVR.
It is important to note that the shape of THD curves in the above figures will change if a higher
number N is selected. This explains why increasing DC source value does not result in a dramatic increase
of THD, as seen in the graphs. However, higher frequency harmonics can be easily removed by filters as
mentioned, they are not of important. In the case that the full impact of the harmonic distortion introduced to
the load needs to be considered, the range of DC source value found would be changed accordingly. Still the
selection principle remains unchanged.
It can also be seen that while the sag curves are nearly linear, those of harmonics are not. This
implies that increasing DC source voltage may improve the capability that DVR can cope with more severe sags;
however, depending on the firing control scheme and other factors, harmonics injected into power system
may differently vary.
With a requirement of different voltage sag level, another range of the source value can be obtained.
Generally speaking, the best case that a DVR may need is it can cope with a local and bolted balanced fault. By
proceeding in the same way, a suitable value of DVR might be selected. In that case, DVR is said to be able to
work with all levels of balanced voltage sag severity.
When DC voltage is large enough but harmonic distortion requirement does not meet, there are other
ways to change DVR parameters that can utilise a better harmonic performance. These include
changing in PWM technique and installing filter at coupling transformer as mentioned, and so forth.
Consequently, the criteria that decide the DVR capability and output quality stated earlier can be obtained.
V. Conclusion
Several aspects of voltage sag mitigation study have been examined. First, a DVR using six-pulse
inverter and three-phase rms voltage measurement and sine wave PWM control was described. It presents
excellent performance to protect critical loads against balanced voltage sags. Then, a DVR using single-
phase rms voltage measurement that works very well against not only balanced voltage sags but also
unbalanced ones resulting from both single-line and line-line faults was presented. Finally, the study of DVR
capability and quality performance was examined thoroughly. This discusses appropriate ways to configure DVR
so that it can deal with all types of voltage sag - balanced and unbalanced, and with all levels of sag severity -
shadow, severe and worst. This addresses the harmonic distortion problem that DVR produces in the power
system. The whole study was mainly involved with changes in the value of DC source voltage in DVR.
A full simulation of DVR mitigation in a large radial system (IEEE 34-bus distribution feeder [4]) was
performed in PSCAD. This has not been presented here due to space constraints but will be presented in a
future paper.
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