Simple and effective digital control of a variable-speed low inductance BLDC motor drive.

Abstract

This paper presents a simple digital control applied to a low inductance 5 kW/48 V three-phase brushless DC motor. Controlling the VSI as a full-bridge converter allowed the use of unipolar switching strategy, increasing the output equivalent frequency up to 100 kHz. The aforementioned strategy has made it possible to control the three-phase currents using a single deadbeat controller without a back-EMF feed-forward compensation. Stability analysis is performed to show that the proposed current control presents good transient response under reasonable parametric variations, as well as zero steady-state error. Precise regulation with no overshoot was obtained using an IP controller to regulate the motor speed. Experimental results are presented to validate the theoretical analysis and to compare with a conventional PI compensator and a predictive controller.