Research on Hybrid Active Power Filter Based on Symmetrical Component Method

To address the harmonic issues caused by nonlinear loads in photovoltaic grid-connected power generation system, as well as the serious asymmetry of three-phase power system resulting from numerous single-phase nonlinear loads, a new hybrid filter main circuit structure and an active filter control method are proposed based on the application of improved symmetrical component method. In this paper, the main circuit structure of the hybrid filter is established, and an analysis is conducted on the topology of the active part, together with the working mode and zero-sequence reactance of the passive part. After that, the PLL control circuit and the overall hardware control structure of the filter are given. In view of the serious asymmetry of three-phase load, the improved symmetrical component method is employed to accurately extract the zero-sequence current component at the neutral side, so as to realize the control over the active part of the filter. Finally, the effectiveness of the hybrid filter and control method in the case of three-phase load symmetry and serious asymmetry is verified through simulation and field application, which demonstrates superior filtering effect and good economy.