Impact of Battery Temperature on Motor Flux Weakening Operations in Electric Vehicles

The environmental pollution is becoming an urgent global problem, leading to the dramatically growth of the electric vehicle (EV) market. Permanent magnet synchronous motors (PMSMs) are among the most used in EV traction drives because of their high starting torque and high torque density, especially for urban and small vehicles. It is well-known that flux-weakening strategy is required for motor drives working in extended speed range due to supply voltage saturation. In this paper, the studied surface permanent magnet synchronous motor (SPMSM) is fed by battery DC voltage which varies with different working conditions. Examinations reveal that the battery voltage significantly changes according to the ambient temperature, and hence impacts on the EV operation. This paper proposes a study of the impact of the battery cell temperature on flux-weakening strategy regarding current and torque constraints. Based on a commercial EV, simulation results figure out major effects of the cell temperature on the flux-weakening performance.