Comparative EMI evaluations of three-phase ZVS-PWM and ZVZCS-PWM inverters

This paper presents the three-phase voltage source soft-switching pulse width modulation (PWM) based inverter using the quasi-resonant commutation snubber circuits in order to improve the power conversion efficiency, realize the high control performances and reduce the electromagnetic noises as compared with three-phase voltage source conventional hard-switching PWM inverter. At first, the resonant AC link snubber-assisted soft-switching inverter is presented as the zero voltage soft-switching (ZVS) PWM inverter and the operation principle of the resonant AC link snubber circuit is explained. Secondly, the common mode and differential mode electromagnetic conductive noises of the resonant AC link snubber-assisted ZVS-PWM inverter is evaluated as compared with the hard-switching PWM inverter, and it is shown clearly that the reduction of differential mode noise is ineffective by using the resonant AC link snubber-assisted ZVS-PWM inverter as compared with hard-switching PWM inverter from the measured results. Thirdly, in order to overcome this problem, the hybrid resonant commutation bridge leg link snubber circuit that the zero voltage and zero current soft-switching (ZVZCS) of all the switches of inverter bridge arms are achieved is proposed, and operation principle of this hybrid resonant commutation bridge leg link snubber circuit is presented. And at last, the electromagnetic noise level of the ZVZCS-PWM inverter and hard-switching PWM inverter are evaluated, it is explained that both common mode and differential mode noises can reduce by using the hybrid resonant commutation bridge leg link snubber as compared with hard-switching PWM inverter, and it is described that ZVZCS-PWM inverter is suitable to improve both conductive common mode and differential mode electromagnetic noise levels.