Optimal Level Number and Performance Evaluation of Si/GaN Multi-Level Flying Capacitor Inverter for Variable Speed Drive Systems

This paper analyzes the optimal number of voltage levels concerning power density for a motor-integrated Multi-Level Flying Capacitor inverter (ML FCi) with 800 V DC-link driving a 7.5 kW Permanent Magnet Synchronous Motor (PMSM). The analysis is performed for an ML FCi, as it enables high efficiency and power density required for motor integration on the one hand and decreases the output filter volume with increasing output voltage level numbers N on the other hand. General scaling laws of the ML FCi are derived analytically and a Pareto optimization based on real hardware dimensions is performed to determine which number of levels is optimal in terms of power density and efficiency and which system performance is achieved for employing Si or GaN power transistors.