A torque ripple minimization method for brushless dc motor in high speed applications

The torque ripple is occurred due to commutation time of phase currents in the brushless direct current (BLDC) motors. In this paper, an effective method is developed in order to reduce torque ripple with wide speed control range for the high speed BLDC motor applications by using boost-buck converter topology. The boost-buck converter is placed between dc power supply and dc-link of the inverter. The dc-link voltage is adjusted depending on motor speed. Pulse Width Modulation (PWM) is used in order to control the phase currents of high speed BLDC motor. The PWM duty cycle is adjusted to reduce the ripple of the phase currents at the commutation time. In  this work, the current control of the high speed BLDC motor is analyzed with different methods such as; traditional control method with fixed dc-link voltage, variable dc-link voltage by using  a boost-buck dc-dc converter and both variable dc-link voltage via boost-buck converter and  current control method by using PWM. The waveforms of current and torque are given for different speed conditions in the steady state and during commutation. The traditional current controls and proposed current control strategies are presented by comparing their performance.