Analysis and mitigation of parallel resonance in the distribution system

This paper deals with the mitigation of the parallel resonance of PFC (Power Factor Correction) capacitor with the supply impedance in the distribution system. The proposed system consists of three phase step-down transformer, three phase thyristor converter used to feed load commutated inverter (LCI) of a synchronous motor (SM) drive and a capacitor at point of common coupling (PCC) for PFC used in the distribution system. The PFC capacitor with a small inductor is designed as a passive filter to mitigate the parallel resonance problem in the distribution system which shifts the parallel resonance frequency at other frequency than the harmonics of the three phase thyristor converter feeding an LCI-fed SM drive. The mitigation of the parallel resonance problem is demonstrated through simulated results in MATLAB with SPS toolboxes to validate the design.