Efficiency improvement of permanent magnet synchronous motor for electric vehicles

Permanent magnet synchronous motors (PMSMs), which are widely used in electric vehicles, have advantages such as high efficiency and power density. However, owing to the limitations in battery capacity, maximizing the efficiency of the motor drive system is essential to extend the driving range. In this paper, a variable voltage control strategy based on minimum loss is proposed, which not only reduces the loss of the inverter below the base speed, but also optimizes the electrical loss of the motor to improve the efficiency of the motor, inverter, and the whole drive system. Moreover the current harmonic of the motor stator winding is also reduced, which provides a guarantee for the stable operation of the drive system. First, the loss mechanism of the motor drive system is analyzed in detail, and an inverter loss model and a motor loss model considering iron loss are established. Then, the loss-minimization control and variable voltage control are analyzed to reveal the relationship between the inverter loss and supply voltage. The simulation results in MATLAB/Simulink show that the proposed strategy improved the efficiency of the inverter and motor by as much as 12.8% and 0.77%, respectively, which confirms the effectiveness of the strategy. •The accurate models of the PMSM and inverter are established.•The proposed control strategy can reduce the loss of motor and inverter.•The current harmonics of the motor stator windings are decreased.•The efficiency of the inverter and motor can be increased by 12.8% and 0.77%.