Application of Variable Carrier Frequency Control by Using Wide Bandgap Semiconductors Inverter for WLTC Mode Driving

This paper aims to propose a control method of a high efficiency electric vehicles(EVs) drive motor and to verify its effectiveness. One of the ways to extend the driving distance is to improve the efficiency of the motor control system. However, existing motor control systems which use Si-IGBT inverters have limitations in terms of efficiency due to device restrictions. New inverters using wide bandgap (WBG) semiconductors such as Gallium Nitride (GaN) are being investigated to improve the efficiency. The advantages of a GaN inverter are the lower conduction and switching losses than a Si-IGBT inverter and the higher switching frequency. If the switching frequency is increased, the motor harmonic loss as well as the whole loss in the motor control system can be reduced. However, most of the existing research have focused on small capacity modules, which are not sufficient to study the motor control system of EVs. Therefore, our research group has been working on improving the GaN inverter to realize a compact EV. We are investigating variable carrier frequency control as a control method to make WBG semiconductors more useful. In this paper, a variable carrier frequency control is applied to a motor control system using GaN and SiC inverters, and we discuss the usefulness of wide bandgap semiconductors for electric vehicles by measuring the loss in WLTC mode with the systems. The experimental results show that the application of variable carrier frequency control to the motor control system with SiC inverter reduces the loss in WLTC mode by up to about 6% compared to the conventional control method.