Mitigation of Voltage Unbalance by DSTATCOM in a Three Phase Four Wire System

This paper presents a Distribution Static Compensator (DSTATCOM) that uses a traditional Synchronous Reference Frame (SRF) to make source current in phase and sinusoidal shape w.r.t source voltage, so that unity power factor is achieved at source side. In addition to this, a new concept of single phase synchronous d-q reference frame theory is used for generation of reference signals in a three phase distribution system for compensation of voltage unbalances at the load side. Further, this paper uses a traditional hysteresis controller for generation of switching signals for the Voltage Source Converter (VSC). Moreover, switching of DSTATCOM between Current Controlled Mode(CCM) and Voltage Controlled Mode(VCM) is carried out so that only single DSTATCOM serves the problem for current and voltage related Power Quality problems. Simulations are carried out in MATLAB/Simulink environment to validate the proposed scheme and results indicate that the unity power factor is achieved during CCM mode and voltages in all the three phases at PCC are maintained at 1 p.u. during VCM mode.