Comparative Evaluation of 800V DC-Link Three-Phase Two/Three-Level SiC Inverter Concepts for Next-Generation Variable Speed Drives

Abstract

The adoption of wide band-gap (WBG) semiconductors is gaining momentum, particularly in industries where high efficiency and/or extreme power density are major concerns, e.g. electric transportation and aerospace. In order to fully leverage the advantages of WBG devices, identifying the converter topologies best exploiting their superior performance is of utmost importance. Hence, this paper analyzes and compares 2-level and 3-level SiC-based three-phase inverters for next-generation variable speed drives. Full sine-wave filtering at the converter output is assumed to counteract the negative effects of the fast switching transitions of WBG devices on the driven machine. The stresses on the active and passive components, i.e. semiconductor losses, output inductor flux ripple and DC- link capacitor RMS current, are calculated by analytical and/or numerical means. Moreover, the optimal semiconductor chip area, the power losses and the efficiency of each converter topology are investigated as functions of the switching frequency, providing a theoretical performance limit for each solution. Finally, a multi-objective optimization targeting an 800 V 7.5 kW system is carried out. The results are in good agreement with the theoretical performance analysis and provide an overview of the achievable efficiency vs. power density trade-off for all the considered topologies.