A Hybrid Active Power Filter Comprising an Active Electromagnetic Filter

A hybrid active power filter comprising a b-shape C-type hybrid active power filter and an active electromagnetic filter is proposed in this paper. The active electromagnetic filter of the proposed topology consists of a three-phase Zig-Zag transformer and a half-bridge single-phase inverter connected in parallel with the b-shape C-type hybrid active power filter and the loads. The zero sequences of the load currents due to unbalancing and the triple order harmonics are compensate by the active electromagnetic filter. In this topology, compensation of the zero sequences is independent of the Zig-Zag transformer location. The b-shape C-type hybrid active power filter consists of a double tuned parallel passive filter and a half-bridge three-phase inverter. Using the active electromagnetic filter reduces rated power of the active part of the b-shape C-type hybrid active power filter effectively. The proposed configuration is applicable in high voltage grid (up to 20kV) due to the series capacitor of the b-shape C-type hybrid active power filter and the Zig-Zag transformer of the active electromagnetic filter. The principles, the steady state compensation and the resonance-damping characteristics of the proposed topology are analyzed in detail. The hybrid active power filter is simulated and the simulation results are provided to validate effectiveness of the topology and the design considerations.