A Min-communication Control for Grid-connected Cascaded PV Inverters

A minimize communication control method is proposed for photovoltaic (PV) grid-connected systems with cascaded H-bridge inverters. In the system used in this paper, PV panel in each unit is directly connected to the input port of the local H-bridge, then the output ports of these H-bridge inverters are cascaded with each other, each PV unit works at its maximum power point (MPP) to guarantee system's maximum power generation efficiency. With communication, the inverter that connect to the point of common coupling (PCC) is controlled as a current source to keep synchronous operation with the utility grid by regulating its output current in phase with the grid voltage. The other cascaded inverters are controlled as voltage resources and keeping self-synchronization with unity power factor (PF) by the proposed control method without any communication. Finally, the common link current drives all cascaded inverters keep self-synchronization with the grid and provide maximum power with high quality to the grid. Compare with other control methods, the proposed control method only requires one communication link, the communication cost is effectively reduced, the reliability and power quality of the system are greatly improved. Simulation test verifies the correctness and validity of the proposed control strategy.