Performance Comparison of Linear Controllers for Voltage Dip Mitigation using Dynamic Voltage Restorer /

Abstract

Dynamic Voltage Restorer (DVR) is a series connected custom power device whose main function is to compensate for the voltage sags. For this purpose DVR uses a Voltage Source Converter with an energy storage which is connected between the load and grid through an injection transformer and an LC-filter. Conventionally, DVR employs Proportional Integral (PI) controllers as a part of control technique which have certain drawbacks like greater response time due to a large number of transformations. In this study, three different types of linear controllers i.e. PI, Proportional Resonant (PR) and Vector Proportional Integral (VPI) are designed, investigated and modelled. Control topology for all the controllers is kept same, i.e. cascaded voltage and current controllers, for comparison purposes. For all the controllers the performance analysis is presented while considering the computational time delays. The simulation study presents the results under balanced as well as unbalanced fault conditions supplying three different types of loads i.e. Linear, Non-linear and Dynamic Load. VPI controller depicts the fastest performance with a good steady state response while PR controller illustrates the best steady state performance among all others but with greater response time than VPI.