Though the three-phase two-level parallel photovoltaic grid-connected systems can increasing the efficiency of the system, the inter-module circulating current is caused by sharing positive, negative and AC buses. To solve the problem reduction of stabilize caused by the circulating current, firstly a new scheme of LCL filter based on sharing neutral point of capacitances is proposed to suppress high frequency common-mode circulating current, because it improve the order of the zero-sequence circulating current transfer function. Secondly, the low frequency components of the zero-sequence circulating current is analyzed, and an appropriate harmonic compensator is designed to reduce them. A composite strategy of suppressing circulating current is proposed working with the new scheme of LCL and the harmonic compensator. Finally, a Matlab/Simulink based platform for simulation is constructed. Results of simulation show that the result of theoretical analysis on the circulating current and the proposed control strategy are correct.
