Common Mode Voltage Effects and Bearing Current Mitigation in Three-Level NPC Inverter-Driven PMSMs for Electric Vehicles

This paper provides a detailed examination of the influence of common-mode voltage (CMV) on leakage and bearing currents in Permanent Magnet Synchronous Motors (PMSMs) for Electric Vehicles (EV) powered by Three-Level Active Neutral-Point Clamped (ANPC) inverters. A comparison of various carrier-based Pulse Width Modulation (PWM) techniques is conducted, evaluating their performance in terms of phase current Total Harmonic Distortion (THD), leakage current, CMV, and bearing voltage. An equivalent circuit model, integrating PMSM's parasitic capacitances and bearing dynamics, is developed to analyse bearing behaviour under both healthy and fault conditions. Simulation results obtained in the PLECS environment offer valuable insights for selecting the modulation strategies that effectively balance CMV reduction, motor longevity, and inverter output quality, thereby enhancing the reliability of the system.