A grid-tied photovoltaic generation system based on series-connected module integrated inverters with adjustable power factor

In order to enhance the redundancy and reliability for distributed generation, a grid-tied photovoltaic (PV) generation system based on series-connected module integrated inverters (SC-MIIs) is proposed in this paper. In the proposed system, each MII is interfaced with a PV panel with independent maximum power point tracking (MPPT) to harvest maximum solar energy. The outputs of MIIs are at AC-line frequency and are connected in series to fulfill the voltage requirement by the utility grid. Since the high step-up power conversion in the conventional micro-inverter is avoided, the SC-MIIs based PV grid-tied structure is easier to be implemented and features higher efficiency. A distributed control strategy for SC-MIIs is also proposed for this system, in which the active power sharing between SC-MIIs is determined by the individual maximum power available from PV panels, while the reactive power of the system can be regulated through any of the SC-MIIs according to the utility grid command. Simulation and experimental results verify the feasibility and effectiveness of the proposed system and its corresponding control strategy.