DSP-based high-speed sensorless control for a brushless DC motor using a DC link voltage control

Abstract

A DSP-based high speed sensorless control for a brushless DC (BLDC) motor using a DC link voltage control scheme is presented. By operating the BLDC motor in a high speed range, the drive system can have a small size and be light weight at the same output rating. In the existing sensorless control schemes, the PWM technique is generally used as a speed control. However, since the PWM and inverter commutation cannot be performed independently, a significant commutation delay may exist in a high-speed region. On the other hand, using the DC link voltage control scheme, the inverter is operated with the squarewave of 120degrees conduction and the speed control is achieved by regulating the DC link input voltage of the inverter through the chopper. By using this technique, since the voltage control and commutation can be achieved independently, a commutating delay does not exist even in a high speed region. Also, the phase current can have a waveform similar to the rectangular wave and the terminal voltage is more efficient to deal with in the position detection circuits. The practical implementation issues concerning the commutation delay in a high speed sensorless control are discussed. The whole control system is implemented on a BLDC motor using DSP TMS320C240 and the effectiveness is verified through the comparative simulations and experiments.