Fuzzy logic based supervision of DC link PI control in a DSTATCOM

In a DSTATCOM, generally, the DC capacitor voltage is regulated using a PI controller when various control algorithms are used for load compensation. However, during load changes, there is considerable variation in DC capacitor voltage which might affect compensation. In this work, a fuzzy logic based supervisory method is proposed to improve transient performance of the DC link. The fuzzy logic based supervisor varies the proportional and integral gains of the PI controller during the transient period immediately after a load change. An improvement in the performance of the controller is obtained because of appropriate variation of PI gains using expert knowledge of system behaviour and higher sampling during the transient period. A 50% reduction in the error in DC link capacitor voltage during load change compared to a normal PI controller is obtained. The voltage waveform also has a faster settling time. The efficacy of the proposed strategy is proved using detailed simulation studies.