Vector based analysis for design of single phase SRF controller in Dynamic Voltage Restorer

A novel vector based control scheme for single phase Dynamic Voltage Restorer (DVR) is proposed to obtain fast and effective restoration of load. The proposed control scheme is based on exact voltage insertion method in which extensive analysis of inserted voltage vector is done. The complete vector analysis during sag provides the magnitude and phase of injected voltage. Improved single phase synchronous reference frame (SRF) theory is utilized for this vector analysis. Besides, closed loop control technique is adopted in phasor study. This proposed method completely removes the freezing of Phase-Locked-Loop (PLL) required at the sag instant where phase jump mostly occurs. Actually, the PLL is nonlinear in nature and must be slow in response to give proper voltage insertion. The suggested controller exhibits both feed forward and feedback path with separate magnitude and angle control. The digital simulation in MATLAB indicates that the suggested vector method for voltage insertion can effectively restore healthy value of voltage for nonlinear load as well.