Using C-type filter with partial compensation method for capacity reduction of hybrid power quality conditioner in co-phase traction power system

Abstract

Hybrid power quality conditioner (HPQC) has been utilised in a co-phase electrified railway system with the aim of improving power quality indices. A C-type filter is designed as an auxiliary device alongside the HPQC for high-order harmonics mitigation in this paper. Alternatively, the C-type filter compensates a selected portion of load reactive power, while the HPQC compensates for the left required power. Furthermore, the HPQC mitigates grid side unbalance and other harmonics in a co-phase supplied system simultaneously. In addition, a design procedure of LCL filters is proposed to suppress high-order harmonic contents induced by the HPQC converters to achieve lower grid-side total harmonic distortion (THD). Moreover, a flexible partial compensation (PC) method considering the C-type filter effect on the HPQC performance is adapted to maintain the grid-side power quality indices in an acceptable range. The C-type filter and PC method provide VA rating reduction of the HPQC without applying any complication to the compensation control system. Finally, simulation and experimental results are presented to validate the feasibility and functionality of the proposed configuration.