Efficiency Optimization Control of Direct Drive Permanent Magnet Synchronous Motor

High-performance permanent magnet synchronous motor(PMSM) systems used in electric vehicle(EV) are required to deliver high efficiency over the wide speed and torque ranges. This paper proposes a novel efficiency optimization control strategy of PMSM system EV which can maximize the system efficiency in both steady and dynamic state. As the PMSM is directly connected with the load, caused the output torque of motor is a function of the rotate speed, this study is focused on the dynamic system model with the driving cycle which considers about motor copper loss, motor iron loss and inverter loss. Based on the dynamic system model, the proposed control strategy can optimize motor loss and inverter loss together, by which the system efficiency is increased over the whole operation duty. Compared with traditional control strategy, the proposed control strategy can decrease the energy consumption over the whole driving cycle. Both theoretical analysis and experimental results verifies the validity of proposed efficiency optimization control strategy.