Voltage Balancing and Switching Losses Minimization for Dual Three-Phase NPC Inverters in Electric Vehicle Multi-Motor Drives

This paper presents a comprehensive study on voltage balancing and switching-loss minimization in dual three-phase neutral-point-clamped inverters for electric vehicle multi-motor drive applications. The increasing adoption of multi-motor drives in electric traction systems, often comprising two electric machines connected to the same battery and operating at different points, enables flexible optimization of driving profiles. Each three-phase system can be controlled independently; however, a collaborative strategy introduces new degrees of freedom to improve voltage balancing and reduce switching losses. A novel control strategy is proposed to maintain capacitor voltage balance while simultaneously reducing switching losses, thereby enhancing the overall efficiency of the inverter system. The effectiveness of the method is validated through experimental results obtained with a dual three-phase drive composed of a permanent-magnet synchronous motor and an induction motor under various operating conditions and load profiles. Results demonstrate significant reductions in switching losses and improved voltage stability, confirming the suitability of the approach for high-performance, multi-motor electric vehicle applications.