The Common-Mode Voltage Reduction Method for Two-Stage Power Conversion System

This paper proposes a method to reduce a common-mode(CM) voltage that causes an electro-magnetic interference(EMI) noise in a two-stage power conversion system consisting of a 3-phase 3-level neutral-point clamped(NPC) converter and a 3-parallel 3-level DC-DC converter. the CM voltage of the system is defined as the difference between the CM voltage generated by each converter. The proposed switching sequence controls the DC-DC converter to output the CM voltage that matches the CM voltage of the NPC converter controlled by a large-medium-zero(LMZ) PWM. The proposed method is verified by experiments through the two-stage power conversion system.