A common-mode voltage reduction method for a back-to-back four-level hybrid-clamped converter

Four-level hybrid-clamped (4L-HC) converter is a newly proposed topology which is suitable for high-performance medium-voltage drives. Zero-sequence voltage (ZSV) is commonly used to balance the DC-link capacitor voltages of this topology and then the common-mode voltage (CMV) is also affected. This paper proposes a CMV reduction method for a back-to-back 4L-HC converter. The relationship of CMV and ZSV in the back-to-back 4L-HC converter is discussed in detail and the amplitude of CMV at motor terminals can be effectively reduced by properly selecting the ZSV. Simulation results are presented to verify this method.