Low-loss quasi-parallel resonant DC link inverter with advanced PWM capability

Abstract

A low-loss quasi-parallel resonant DC link (L(2)QPRDCL) circuit with advanced PWM capability is proposed for soft switching a three-phase PWM inverter. This L(2)QPRDCL has minimum voltage stress for the devices, and an advanced PWM capability due to the variable zero voltage duration of the DC-link over a wide range. Owing to there being scarcely any freewheeling current in the L(2)QPRDCL during the zero voltage period, low-loss operation in the resonant circuit can be obtained. As a result, the proposed L(2)QPRDCL inverter is applicable to the high-power range. Operational principles and detailed analyses are presented. By adopting the non-nearest four vectors ((NFV)-F-2) selection law in the space vector PWM technique, the narrow pulse problem originating from the link operation, which should be considered in those inverters having resonant DC-links, can be eliminated. Experimental results are also presented to verify the link operation and the performance of the selected space vector PWM method.