Variable Switching Frequency Control for Efficiency Improvement of Motor Drive System by Using GaN Three Phase Inverter

This paper aims to propose a new traction motor control system for electric vehicles (EVs). EVs are required to have higher energy efficiency in motor control systems for cruising longer distance. However, motor control systems, which are generally equipped with Si-IGBT inverters, have limits of the energy efficiency. Therefore, new inverters, which use wide bandgap (WBG) semiconductor devices such as Gallium Nitride (GaN), are expected to be a solution to improve the energy efficiency. Having less energy loss in conducting and switching operation than Si-IGBT inverters, the GaN inverters can increase the switching frequency. In addition, the reduction of harmonic loss of the motors will enable us to improve the energy efficiencies of the entire motor control system. Although previous researches have demonstrated the performance of various inverters, the experiments demonstrated only inverters of small capacities that are insufficient to be applied in traction motor control of EVs. Then, our research group are challenging to increase the power of GaN inverters and to realize their practical application to compact EVs. In this research, the switching frequency of the GaN inverter was dynamically changed to verify the higher energy efficiency of the motor control system. The results of the experiment have shown that the total energy efficiency can be improved by up to about 1.5% and the total loss can be reduced by up to about 10%.