Modeling and Simulation for Voltage Sags/Swells Mitigation Using Dynamic Voltage Restorer (DVR) Rosli Omar And Nasrudin Abd Rahim Faculty Of Engineering Department Of Electrical Engineering University Of Malaya Kuala Lumpur Malaysia omarrosli@yahoo.com Abstract- This paper describes the problem of voltage sags and swells and its severe impact on non linear loads or sensitive loads. The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags and swells. The control for DVR based on dqo algorithm is discussed. The proposed control scheme is simple to design. Simulation results carried out by Matlab/Simulink verify the performance of the proposed method. Keywords- Dynamic Voltage Restorer (DVR), voltage sags, voltage swells, custom power and power quality. I. INTRODUCTION Power Quality problems encompass a wide range of disturbances such as voltage sags/swells, flicker, harmonics distortion, impulse transient, and interruptions [1]. Voltage sags can occur at any instant of time, with amplitudes ranging from 10 – 90% and a duration lasting for half a cycle to one minute [3]. Voltage swell, on the other hand, is defined as a swell is defined as an increase in rms voltage or current at the power frequency for durations from 0.5 cycles to 1 min. typical magnitudes are between 1.1 and 1.8 up. Swell magnitude is also is also described by its remaining voltage, in this case, always greater than 1.0. [2]. Voltage swells are not as important as voltage sags because they are less common in distribution systems. Voltage sag and swell can cause sensitive equipment (such as found in semiconductor or chemical plants) to fail, or shutdown, as well as create a large current unbalance that could blow fuses or trip breakers. These effects can be very expensive for the customer, ranging from minor quality variations to production downtime and equipment damage [5]. There are many different methods to mitigate voltage sags and swells, but the use of a custom Power device is considered to be the most efficient method. Switching off a large inductive load or Energizing a large capacitor bank is a typical system event that causes swells [1]. This paper introduces Dynamic Voltage Restorer and its operating principle. Then, a simple control based on dqo method is used to compensate voltage sags/swell. At the end, MATLAB/SIMULINK model based simulated results were presented to validate the effectiveness of the proposed control method of DVR. II. CONVENTIONAL SYSTEM CONFIGURATION OF DVR Dynamic Voltage Restorer is a series connected device designed to maintain a constant RMS voltage value across a sensitive load. The DVR considered consists of: a. an injection / series transformer b. a harmonic filter, c. a Voltage Source Converter (VSC), d. an energy storage and e. a control system , as shown in Figure 1 Figure 1: Schematic diagram of DVR 2008 Australasian Universities Power Engineering Conference (AUPEC'08) Paper P-027 page 1