Hye-Won Choi, Sungjoon Cho, and Kyo-Beum Lee, "Circulating Current Reduction in a Parallel Connected-Inverter for Distributed Generation Systems," in Proc. APAP Conf., Oct. 2021. > Paper

This paper proposes a circulating current (CC) reduction method in a parallel connected-inverter for distributed generation systems. The distributed 

generation inverters have been installed according to the increment of the renewable energy demand. In general, the modular scheme is applied in the inverters for increasing power capacity. The modular inverters have the advantages of the convenient design and maintenance, and adjustable power 

rating by the number of modules. However, the CC occurs when each inverter has the different output voltages due the inconsistent triangular carrier waves and different circuit parameters. The CC will deteriorate the output current and degrade the performance of the parallel distributed generation 

system. This paper analyzes the components of the CC, and proposes the enhanced CC reduction method for improving the efficiency of the parallel 

connected-distributed generation system. The high frequency CC is reduced by synchronization of the triangular carrier waves of modules, and the low frequency CC can be suppressed by injecting equal zero-sequence voltages during PWM. The validity of the proposed control method was 

demonstrated by simulation results.