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Position Sensorless Control of BLDCM Using Direct Torque Control

Abstract

In this paper, speed and position sensorless control of BLDC motor with non sinusoidal back EMF using direct torque control with an improved flux estimation algorithm has been proposed. The rotor position is obtained through calculations by generating an orthogonal flux system. PI controllers are used for tuning. The inverter voltage space vector for a two-phase conduction mode is derived from a simple look-up table to obtain the desired quasi-square wave current. The output of the hysteresis controller is fed to the look-up table. The look-up table includes input information from torque, flux and sector to produce the corresponding switching pulses for the inverter. This simplifies the switching and decreases the processing time, unlike the PWM or Space vector PWM controls. It gives faster torque and speed response with reduced ripples. It also provides an accurate speed control. The proposed method closely resembles the DTC used in ac sinusoidal motors but differs in its flux estimation algorithm. This methodology improves the efficiency of the drive. The validity and practical application of the proposed two-phase conduction DTC of BLDC motor drive scheme is verified through simulations on a 24V 4000rpm PMBLDC motor.

Dolly Nelson, Jayasri R. Nair

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