Study on the dead-time effection in PWM inverter control of electric vehicle´s motor

One of the disadvantages of the direct torque control (DTC) in electric vehicle motor drive system is poor performance at low speed, and the dead-time is an important factor influencing its low speed performance. Dead-time effect caused by the switching lag-time, which avoids the phase shortage of inverter arms, causes serious distortions of output voltage and current of the inverter. In order to reduce the output waveform´s harmonic content of inverter and the torque ripple of motor, several methods have been proposed. However, most of those methods consider from voltage or current compensation, and the relative realization are complicated meanwhile the result is not satisfied. With Fourier Transform this paper presents the principle of the dead-time influence on the torque ripple of the motor controlled by PWM inverter. By calculated, this paper obtains a set of optimal solutions. A novel method to improve the torque ripple was proposed. Theory analysis and simulation results show this method can decrease the scope of unreasonnable torque ripple.