Implementation of Single-Phase SRF (d-q) Theory for Control Technique in DVR Restoring Voltage Sag in Sensitive Nonlinear Load

In three-phase power system with the presence of nonlinear sensitive load, the complexity of control design for dynamic voltage restorer (DVR) becomes serious issue for unbalance sag mitigation. Restoration of pre-sag value of load voltage requires freezing of phase lock loop (PLL) at the point of initiation of fault. The already in existent single-phase and/or three-phase synchronous reference theory (SRT) utilized for the design of control system for DVR shows poor response in restoration of unbalance voltage sag and harmonics in nonlinear load. Therefore, the ultimate objective of paper concentrates on design of robust controller based on single-phase SRT for DVR mitigating sag in sensitive nonlinear load. Hence, a new control concept has been suggested which incorporates fundamental component extraction required for nonlinear load. The suggested control scheme is phasor based which utilizes pre-sag mitigation technique by single-phase SRT. It operates on forward control strategy for better transient response. The proposed controller for DVR illustrates its effective performance carried out in MATLAB in the obtained results.