A Novel 3D-SVPWM Modulation Strategy for Zerosequence Circulating Current Suppression in Threephase Four-Leg Parallel-Inverter Systems

The three-phase four-leg (3 P 4 L) parallel-inverter system has been increasingly applied in the field of new energy power generation due to its capability of feeding single-phase loads. However, zero-sequence circulating current (ZSCC) can jeopardize the stable operation of the parallel-inverter system. This paper firstly analyzes the generation mechanism of zerosequence circulating current in the 3P4L parallel-inverter system and a novel 3D-SVPWM modulation strategy has been proposed to suppress the circulating current. By changing the difference in zero-sequence duty ratios between the two inverters, the zerosequence voltage difference is altered, thereby achieving the effect of suppressing circulating current. Finally, simulation results have been provided to validate the effectiveness of the proposed strategy.