Common-Mode Resonance Suppression in Transformerless PWM Current-Source Drive

Among high-power pulsewidth modulation (PWM) current-source motor drives, the transformerless structure using the integrated dc choke has been widely acknowledged with superior advantages. A typical challenge faced by such transformerless PWM current-source drive systems is the potential common-mode resonance excited by the common-mode voltage (CMV). Since the implementation of power factor compensation (PFC) at low motor speeds may increase the CMV in such drives, the common-mode resonance could be serious and further aggravate the CMV stress on the system. In this paper, the critical factors on the common-mode resonance are thoroughly investigated. Based on the investigation, a solution based on average-value-reduction (AVR) spacevector modulation (SVM) is proposed to suppress the common-mode resonance while maintaining the PFC function. The investigation of common-mode resonance and the effectiveness of the proposed resonance suppression solution are verified through experiments on a transformerless PWM current-source drive system.