Optimized Design of Three-Level APF Voltage Loop Considering DC-Link Voltage Oscillations

When current harmonics of nonlinear loads are compensated by the three-level active power filter (APF), voltage oscillations will be generated in the dc-link. In this paper, firstly, the dc-link voltage oscillation generated by specific harmonic current is analyzed. Then, the mathematical model of three-level APF is established, and the transfer function diagram of the control system is obtained. An optimized design method is proposed for the voltage control loop to improve the harmonic-compensation performance while guaranteeing the stability of the control system. To verify the effectiveness of the proposed method, a three-level APF is built. Experimental results show that, compared with the conventional design method for voltage loop, the proposed design method has a better ability to compensate current harmonics in nonlinear loads.