"SRF theory revisited" to control self supported dynamic voltage restorer (DVR) for unbalanced and nonlinear loads

In this paper a fuzzy controller based DVR is proposed for the protection of the sensitive unbalanced nonlinear loads from sag/swell, distortion, and unbalance in supply voltage is achieved. A simple generalized algorithm based on basic synchronous reference frame theory has been developed for the generation of instantaneous reference compensating voltages for controlling a DVR. This novel algorithm makes use of the fundamental positive sequence phase voltages extracted by sensing only two unbalanced and/or distorted line voltages. In addition to this a fuzzy logic controller have been developed to reduce the % THD compared with the conventional method. The compensating voltages when injected in series with a distribution feeder by three single-phase H-bridge voltage-source converters A capacitor-supported DVR does not need any active power during steady-state operation because the injected voltage is in quadrature with the feeder current. The proposed control strategy is validated through simulation results with the help of MATLAB/SIMULINK software.