High energy-efficient electrical drive with multilevel inverter and wide-bandgap power semiconductors

Abstract

Multilevel inverters are an alternative for electrical drives with DC link voltage between 560 and 750 V. In this voltage range new wide-bandgap power switches (SiC MOSFET, GaN FET) are available. The paper analyses three-, four-, five- and seven-level inverters. A simulation model of the drive system, including the 11 kW induction motor and motor filter is developed. By replacing IGBTs with SiC FETs, the two-level inverter achieved a loss reduction of 59 % at 25 °C and 150 °C at nominal motor operation point. By using the five-level inverter with GaN FETs, a further loss reduction of 9 % only at low junction temperature is possible. With a higher number of inverter levels, the size of the motor filter can be reduced. With five inverter levels and 40 kHz switching frequency volume and weight can be reduced by 86 % and 78 % respectively. The overall efficiency of the drive system achieves 98.5 % at 25 °C and 98.1 % at 150 °C. Compared to the state of the art (two-level with IGBTs with 5 kHz), this is an improvement of 2.1 % at 25 °C and 2.7 % at 150 °C.