Modeling and analysis of IPM synchronous motor under six step voltage control by fourier series

High efficiency, high power density and wide constant power region are all the required functions of the traction motor and drive in electric vehicle applications. However, these requirements are mainly dependent on the output line voltage utilization of the motor drivers. Generally, electric vehicle use over-modulation to increase voltage utilization under constant output voltage of battery. A six-step voltage control method without current control loops is proposed to increase output torque and power of IPMSM at middle and high speed region. The relation between generated torque and both amplitude of DC-link voltage and phase leading voltage angle of six-step voltage is derived carefully on this research. The proposed method is analyzed by Fourier series for mathematical derivation. Moreover, the efficiency of motor and its drive are improved due to the current harmonics and switching losses of PWM are reduced by the six-step voltage control. The proposed motor drive consists of two power modules controlled by single DSP. The front end is a DC-DC converter connected to battery to generate a variable voltage with fast response according to the motor speed. The second stage is an inverter which provides vector control and the proposed six-step voltage control for IPMSM. Finally, some simulated and experimental results are made on a 6kW IPMSM to show the correctness of the proposed analysis method.