Analysis of over-voltage of dc-link capacitor of solid state power supply in parallel operation

In the medium frequency voltage source paralleled inverters, the paralleled diodes in IGBTs run as rectifier before the inverter starts, and the DC capacitor could be damaged by over voltage because of the transient of the circuit. This paper analyzed the characteristics of medium-frequency inverter in parallel operation, compared to the 50Hz inverter. The simplified system model is setup, and the impact of parallel inductor, the use age of DC voltage and filter capacitor on the safety of DC capacitor is analyzed theoretically. The Simulink model is established to verify the theoretical analysis. Finally, measures are proposed to protect DC capacitor.