International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 994 POWER QUALITY IMPROVEMENT USING DVR (DYNAMIC VOLTAGE RESTORER) UNDER VARIOUS FAULT CONDITIONS Anjani Kumar Prajapati 1 , K. P. Singh 2 1 P.G Student, Department of Electrical Engineering, MMMUT, Gorakhpur, Uttar Pradesh, India 2 Associate Professor, Department of Electrical Engineering, MMMUT, Gorakhpur, Uttar Pradesh, India -----------------------------------------------------------------------***-------------------------------------------------------------------- Abstract - Power quality improvement has become a very serious concern in present days due to increase in modern sensitive and sophisticated loads connected to the Distribution System. Because non-standard voltage, current or frequency causes a failure of the loads connected to the system. Power electronics and advanced control technologies have made it possible to improve the quality of power and operate the sensitive loads satisfactorily. One of the major problems dealt in this paper is the voltage quality which is very severe for the industrial customers as it can cause mal-functioning of several sensitive electronic equipment. Dynamic Voltage Restorer (DVR) is a solution to improve voltage quality, which is connected in series with the network. This paper presents modeling, analysis, and simulation of DVR in MATLAB/SIMULINK, which includes PI controller and discrete PWM generator for control purpose of DVR. Simulation results of performance of DVR under different fault conditions such as single line to ground fault, double line to ground fault, double line fault, three phase fault etc. are presented in this paper. The results exhibit clearly the performance of the DVR in voltage quality improvement. KEY WORDS: DVR, POWER QUALITY, FACTS, PI CONTROLLER, PWM 1. INTRODUCTION: Electric Power Utilities and end users of electric power are becoming increasingly more serious about the electric power quality. The term DzPower Qualitydz has become most popular word in the power industry since the late ͳͻͺͲs. There are following reasons for the increased concern towards power quality. Newer generation load equipment, with microprocessor- based controls and power electronic devices, is more sensitive to power quality variations than was the equipment used before the late 1980s. Increasing emphasis on overall power system efficiency has resulted in continuous growth in the application of devices such as high-efficiency, adjustable-speed motor drives and shunt capacitors for The purpose of power factor improvement so that losses can be reduced. This is resulting in increasing harmonic levels on power systems and has many people concerned about the future impact on the system capabilities. End users have an increased awareness of power quality issues. Utility customers are becoming better informed about such issues as interruptions, sags and switching transients and are challenging the utilities to improve the quality of power delivered. Many devices are now interconnected in a network. Integrated processes mean that the failure of any component has much more important consequences. Load equipment. Interestingly, the equipment installed to increase the productivity is also often the equipment that suffers the most from common power disruptions and the equipment is sometimes the source of additional power quality problems. When entire processes are automated, the efficient operation of machines and their controls becomes increasingly dependent on quality of the power. Power quality can be defined as those properties of the power supply which allows the electrical apparatus to function properly. But in actual sense power quality is ult imately a customer driven issue, and the end user’s point of reference takes preference [1]. So any power problems manifested in voltage, current, or frequency deviations that result in failure or mal-operation of the customer equipment can be categorized into power quality problem. To deliver clean and pure power ie. pure sinusoidal voltage waveform, FACTS (Flexible Alternating Current Transmission System) devices are used. There are many FACTS devices which are being used in the modern electrical network, some of them are Static Synchronous Compensator( STATCOM), Static Synchronous Series Compensator( SSSC), Interline Power Flow Controller (IPFC), Unified Power Flow Controller(UPFC), etc. . In actual practice FACTS devices were designed for the transmission system and these are modified to be used in distribution system and named as DzCustom Power Devicesdz. Some of the widely used custom power devices are Distribution Static Synchronous Compensator (DSTATCOM), Dynamic Voltage Restorer (DVR), Active Filter (AF), Unified Power Quality Conditioner (UPQC). With the help of these devices the quality problems are reduced to great extents. DVR is one of the most efficient and effective custom power devices due to its fast response lower cost and smaller size [2]. There are many power quality problems in distribution system such as sag, swell, harmonics, transients etc., but voltage sag is the most severe disturbance which is generally caused by the faults. Voltage Sag and swell can be instantaneous, momentary or temporary. If voltage sag occurs for 0.5 to 30 cycles and voltage magnitude remains between 0.10 to 0.9 pu then it comes under the category of instantaneous voltage sag. If it occurs for 30cycles to 3 seconds and voltage