NPC-Based Multilevel Inverters: Performance Analysis and Control Strategies for Five-Phase Drives

Abstract

This paper investigates the necessity and performance of multilevel inverters, specifically the Five-Phase Three-Level Neutral Point Clamped (FPTHL-NPC) inverter, for multi-phase machine drives. While three-phase drives have traditionally dominated industrial applications, the growing demand for electric propulsion and high-power systems has driven interest in five-phase drives due to their high fault tolerance and reduced torque ripple. However, feeding five-phase loads with discrete inverters introduces x-y subspace currents that do not contribute to power transfer but cause thermal losses. This study compares the performance of a conventional Five-Phase Two-Level Voltage Source Inverter (FPTL-VSI) against an FPTHL-NPC inverter using Sinusoidal Pulse Width Modulation (SPWM). The comparative analysis demonstrates that the NPC multilevel topology significantly reduces total harmonic distortion (THD) and optimizes common mode voltage, making it a superior choice for high-power multi-phase applications.