Stability analysis of sensorless BLDC motor drive using digital PWM technique for electric vehicles

Electric vehicles are attractive for future transportation due to sustainability, efficiency and zero greenhouse gases emission. The Brushless DC (BLDC) motor has been used for propulsion system of electric vehicles in the last decade. This paper proposes a new optimized sensorless drive of BLDC motor. This technique is based on back-EMF zero crossing detection (ZCD) from voltage of one phase suitable for EV application. This paper presents a novel commutation technique of BLDC which significantly reduces sensing circuits and cost of motor drive. Digital PWM technique with a PI duty cycle controller is implemented for speed control. The stability of BLDC motor drive is analyzed by Lyapunov stability method. A novel condition is derived for digital PWM controller system being stable with respect to Lyapunov stability criterion. Further cost reduction is also possible by implementing proposed technique and speed controller on a single chip microcontroller. The effectiveness of stability analysis for proposed sensorless technique is verified through simulation and experiment.