Harmonic Reduction and Performance Improvement of BLDC Motor Using a Selective Harmonic Elimination PWM Based Controller

Brushless DC (BLDC) motors are widely used in various industrial as well as low power applications because they offer high power density, wide range of torque and speed, high torque per watts, high torque to weight ratio, reliability, lower noise and non-requirement of mechanical parts for commutation. They are also being found as an attractive choice in electric vehicular applications. Since these motors rely on electronic commutation, inherent problems of power electronic circuits like harmonics and switching losses will be significantly affecting the motor performance. In this paper, a control scheme is proposed which aims to reduce the motor current harmonics and their negative effects and also improve the overall performance of the motor. A DC-DC boost converter fed inverter with Selective Harmonic Elimination based PWM and a passive lowpass filter combination is used to reduce the THD, reduce the harmonic copper loss and improve the overall system performance like torque ripples and input power factor. The control scheme also automatically decides between operating conditions where SHE-PWM is favorable or not and thus avoids the cases of unnecessary introduction of switching losses.