Research on the operation of active power filters with capacity limitation control

To solve the problem that active power filters (APFs) should meet the needs of increasing nonlinear loads, this paper proposes an APF having the capacity-limitation function of compensating load harmonics. In this APF, if the detected harmonic current exceeds the limit current of the APF, the compensating current can be limited with an optimal approach under capacity-limitation. Consequently, the APF proposed in this paper is optimized to maximize the APF efficiency and to minimize the total harmonic distortion of the line current supplied by the source. When such capacity-limited APFs are cascade-connected between source and load, all harmonic components will be automatically distributed to the APFs participating in the compensation without needing control interconnection. Through the proposed design, the capacity-limitation makes the system work well even under overload conditions. The APF has expansion flexibility when larger APFs arc required for a larger system. In addition to describe the theoretic bases of the proposed APF, this paper also researches the control algorithm of the APF. Theoretical analysis and simulation results are provided for demonstrating the effectiveness of the proposed approach.