For the harmonic of large capacity nonlinear load

a parallel combinatorial system of modular active power filter is proposed and its system structure and operating principle are researched. Based on this

the corresponding small signal model is set up and a control strategy in the case of different module capacities is introduced for comparison. Then an average current control and redundancy control strategy is put forward. In order to guarantee the steady and dynamic performance

a compound control strategy including digital proportional-integral control and repetitive control is adopted. Finally

a device including two modular 50 kVA active power filters is constructed and the effects of different control strategies among modules and different control strategies inside modules are compared. The feasibility and efficiency of the proposed control strategy is validated by experimental results. This work is supported by National Natural Science Foundation of China (No. 51177147).