Analysis of DC bus overvoltage in parallel photovoltaic systems

High power photovoltaic plants are usually constituted of distributed solar subfields. This paper focuses on the dynamic characteristics analysis of parallel connected photovoltaic (PV) systems. Due to the existence of the parasitic capacitance to ground, a circulating current among parallel PV inverters is injected into the system. The circulation may cause DC bus overvoltage fault when the inverter switches to the standby mode. The reason of bus overvoltage is investigated in detail in this paper. Then, a device aiming at avoiding DC bus overvoltage is proposed to solve this issue. The theoretical analysis has been validated through simulations.