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Efficiency optimization control of permanent magnet synchronous motor system with SiC MOSFETs for electric vehicles

As the permanent magnet synchronous motor (PMSM) system is the key part of power system in electric vehicles (EVs), the efficiency of PMSM system has great influence on the energy consumption of EVs. To increase the endurance mileage of EVs in one charge, it is important to improve the system efficiency of PMSM drive system. This paper proposes a novel analytical nonlinear loss model for PMSM system which can calculate motor loss and inverter loss together. The PMSM loss can be calculated by the analytical model which can exactly predict copper loss and iron loss together. The nonlinear switch characteristics and conduction characteristics of power devices can be fitted by the nonlinear model, by which the accurate inverter loss is acquired in a fast and simple way. This paper applied double Fourier integral analysis to calculate the harmonic current caused by the PWM output voltage of inverter in an analytic method, by which the system stability is analyzed. Based on the nonlinear system loss model, this paper proposes an efficiency optimization control strategy which can significantly increase the system efficiency without serious effect on the system stability in the whole operation condition of PMSM system for EVs. Both analytical and experimental results prove that efficiency optimization control can decrease the system loss and improve the system efficiency of PMSM system.