A novel Active Power Filter topology based on coordinate transformation

As one of the most effective methods to inhibit electric power grid harmonics, the technology of Active Power Filter (APF) has been a key subject in the field of power quality control. Currently, research on APF mainly focuses on topology structure and control strategy. A novel topological structure of APF in alpha-beta coordinate is presented based on transformation of three phase static A-B-C coordinate to two phase static alpha-beta coordinate. The topological structure adopts two groups of single-phase inverter as main devices of APF, and can realize transformation of current source from two phases to three phases by using a special transformer connection. Decoupling of the three phase harmonic compensation current is realized directly in circuit structure. Calculation for the control quantity in the new topological structure is performed directly in alpha-beta coordinate, and the results are directly applied to two groups of single-phase inverter system. The repetitive learning control method is suggested to verify the viability of the proposed APF. The simulation results show that the novel active power filter topology is feasible and its compensation effect is quite good even dead time of inventers in existence.