A simple method of realization of low power loss and high compensation-precision active power filter

In active power filter (APF) application, LCL-filters are prevalently served as output filters due to high slew rate of compensation current and sufficient attenuation ratio for switching frequency with small LC parameters. In order to realize the stable control of LCL filters, appropriate damping is required. Both the classical PI control method with a damping resistor and active damping without the power loss on damping resistor are feasible, while the former method will induce unacceptable power loss under high power condition and the latter one may increase the complexity of control strategy as well as weaken system's robustness. In this paper, a double-loop control strategy for a 380V/264 kVA system with an inner current loop and an external repetitive control loop is proposed. Systematic design approaches of the double-loop control scheme have been given in details. The simulation experiment results indicate that it obtains low power loss reduced greatly from 1.8 kW (0.68%) to 0.8 kW (0.3%) and high compensation-precision with the proposed control scheme.