Different control techniques of Dynamic Voltage Restorer for power quality problems

Nowadays power quality is the biggest issue in power sector. Everyone demands for reliable and good power quality. There are different problems in power quality like harmonic distortion, flicker, notching, transient, etc. Voltage sag and swell are the major problems in power quality. Dynamic voltage Restorer (DVR) is a custom power device used for mitigation of voltage sag and swell. DVR is connected in series by using the injection transformer to inject the appropriate voltage to mitigate voltage sag/swell and maintain the load voltage constant. For the generation of this compensating voltage there are two steps which are reference voltage generation and gate pulse generation for IGBT´s of VSC. In this paper two methods are used for reference voltage generation viz Synchronous Reference Frame (SRF) theory and Fourier transform technique. These methods detect the voltage sag/swell condition and give the reference voltage. Hysteresis controller is used for gate pulse generation in both methods. Simulations are carried out for addition of three phase RL load, removal of load and also for three phase system fault.