Abstract : This paper analyzes the influence of the output cable on the common-mode voltage of the motor and the potential imbalance mechanism of the clamping point of the three-level inverter in a PWM high-voltage frequency converter . To effectively suppress the adverse effects of common-mode voltage on the frequency converter, a novel topology is proposed: in a 24-pulse rectifier/three-level inverter high-voltage frequency converter, a common-mode reactor is set and connected to the rectifier neutral point, DC side midpoint, output filter neutral point, and three-level inverter clamping point, and connected to the system ground through a small resistor. Simulation results of a 6kV/2250kW motor based on this topology show that this topology can reduce the common-mode voltage of the high-voltage frequency converter and improve the reliability of the frequency converter operation. Keywords : High-voltage frequency converter; common-mode voltage; suppression measures; simulation 1 Introduction With the advent of high-voltage high-power power electronic devices such as IGBT and IGCT, high-voltage frequency conversion technology has been gradually promoted and applied to the variable frequency speed regulation of high-capacity fans and water pumps to improve speed regulation performance and energy saving effect. Figure 1 shows a typical voltage source variable frequency speed control system topology, which includes six parts: a three-phase input voltage full-wave rectifier, capacitor filter, PWM inverter, output filter, and transmission cable. (Full text download of high-voltage inverter common-mode voltage simulation study)