Loss optimization control of permanent-magnet synchronous machines drive system for electric vehicles

The efficiency-oriented control strategies are very important to obtain high-efficiency performance of permanent-magnet synchronous motor (PMSM) drive systems. This paper proposes a novel analytic system loss model of PMSM drive system which can consider about both losses of PMSM and power converter losses. The losses of PMSM consist of two parts: stator iron losses and stator copper losses which are calculated with an analytical electromagnetic model. As there is strong nonlinearity in the conduction and switch characteristics of power device, this paper creates a nonlinear inverter loss model to calculate the power device loss of three-phase half-bridge inverter accurately and fast. By the novel PMSM drive system model, an efficiency-oriented control strategy of PMSM drive system named loss optimization control is presented in this paper which can systematically minimize PMSM losses and three-phase inverter losses by maintaining the d-axis current to the optimal current at the each working point. The system efficiency enhancement of proposed loss optimization control is proved by the theoretical derivation and experiments.