Design Considerations of Multi-Phase Multilevel Inverters for High-Power Density Traction Drive Applications

This paper presents the effect of multi-phase machines in Three-Level (3L) Active Neutral-Point Clamped (ANPC) inverter design for high-speed traction drive applications. In this work, GaN-based 3L-ANPC inverters are considered to drive high-speed Permanent Magnet Synchronous Machines (PMSMs) with an 800V DC bus. Two different analytical models are developed to calculate the DC bus capacitor and dv/dt filter requirements of the 3L-ANPC inverters. Using the analytical models, the requirement of the DC bus capacitor and dv/dt filter sizes are compared for driving three-phase, six-phase symmetrical, and asymmetrical PMSMs. Another model is developed from experimental Double Pulse Test (DPT) data to calculate the heat sink size requirements for driving the three types of PMSMs mentioned above. A discussion on the Common Mode Voltage (CMV) is also provided. Finally, a comparison is made in terms of DC bus capacitor, dv/dt filter, heat sink size requirements, and common-mode voltages for the three types of drives. The analytical models are verified in simulation, and the results are presented in this paper.