Research on distributed networked unbalanced harmonic control combined with APF

In order to solve the unbalanced harmonics problem of multi-source and multi-inverter system, a networked hierarchical control approach is proposed, based on the structure of hierarchical control and combined with active parallel filters (APF). In the control approach, the distributed generator (DG) consists of primary and secondary control. In the primary controller and the secondary controller, some basic controls are proposed and modified, which maintain the stable operation of the system. Similarly, a DG compensation and APF-coordinated compensation controller are designed, which coordinate with each other to control the power quality of the system. When the DG compensator cannot fully compensate the sensitive load bus (SLB) by itself, the APF controller can calculate compensation through coordinated control management, then using the APF auxiliary compensator for compensation. Not only does the proposed approach compensate the voltage unbalanced harmonic at SLB, but it also improves the precision of power distribution and load current sharing. Finally, simulation results can validate the effectiveness and feasibility of the proposed approach.