Implementation and control of a dynamic voltage restorer using Space Vector Pulse Width Modulation (SVPWM) for voltage sag mitigation

This paper presents the low voltage dynamic voltage restorer (DVR) based on application of space Vector Pulse Width Modulation (SVPWM) for three phases Voltage Source Converter (VSC) and it is the standard PWM techniques to utilize the DC-AC power conversion. A control technique based on SVPWM is also proposed for dynamic voltage restorer. The DVR was a power electronics device that was able to compensate voltage sags on critical loads dynamically. By injecting an appropriate voltage, the DVR restores a voltage waveform and ensures constant load voltage. The compensating signals are determined dynamically based on the difference between desired and measured values. The DVR consists of VSC, injection transformers, passive filters and energy storage (lead acid battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching the inverter. In this paper a novel structure for voltage sags mitigation and for power quality improvement are proposed. There was an increasing trend of using space vector PWM (SVPWM) because of their easier digital realization and better dc bus utilization. The proposed control algorithm is investigated through computer simulation by using PSCAD/EMTDC software. Simulation results show the performance of the proposed low voltage dynamic voltage restorer and prove the validity of the proposed topology. From simulation and experimental results of a DVR using PSCAD/EMTC software based on SVPWM technique showed that the effectiveness of the DVR in mitigating voltage sags. The DVR operates without any difficulties to inject the appropriate voltage component to correct rapidly any disturbances in the supply voltage. It was concluded that the proposed low voltage dynamic voltage restorer works well both in balance and unbalance conditions of voltages.

I. INTRODUCTION

The dynamic voltage restorer (DVR) is a series custom power device intended to protect sensitive loads from the effects of voltage sags at the point of common coupling (PCC).A typical DVR connected system circuit is shown in Figure 1, where the DVR consists of essentially a series connected injection transformer, a voltage source inverter (VSI), inverter output filter and an energy storage device connected to the dc-link, The power system upstream to DVR is represented by an equivalent voltage source and a source impedance. The basic operation principle of the DVR is to inject an appropriate voltage quantity in series with the supply through an injection transformer when a PCC voltage sag is detected. Loads connected downstream are thus protected from the PCC voltage sag.