Study of modular APF parallel combination system aiming at power quality improvement in distribution network

In order to deal with the increasingly serious power quality problem of distribution network, this paper focuses on the APF compensation scheme and a variety of parallel combination schemes are studied for the limited capacity of APF applications. Then a parallel combination scheme of improved modular APF with independent controller that can be flexibly configured with compensation coefficient is proposed. The hierarchical control strategy is designed. The first layer is the coordination control strategy between modules based on bus communication and current-sharing control. The second layer is the fine control strategy inside module based on the outer voltage loop and inner current loop, in which the inner current loop adopts the compound control structure consisting of repetitive control and PI control. Finally, the validity of proposed system and its control strategy is verified by simulation and experiment.