The parallel three-phase grid-connected converters sharing direct current and alternating current buses can increase the system level

but the circulating current problem is inevitable. According to an analysis of the causes of the circulation

the circulation problems caused by the injection of different zero-sequence voltages are studied. A mathematical model of the circulating current is developed and a modulation scheme combining sinusoidal pulse width modulation(SPWM)and space vector pulse width modulation(SVPWM)is proposed. It is expected that the voltage utilization can be increased

the low-frequency circulation due to the injection of different zero-sequence voltages should be avoided. Finally

the experiment platform of parallel three-phase grid-connected converters is set up in the laboratory to facilitate experiments and verify the feasibility and effectiveness of the proposed modulation method.