Analysis and simulation studies for position sensorless BLDC motor drive with initial rotor position estimation

This paper presents a simulation for the sensorless operation of a BLDC motor drive with the estimation of initial rotor position at standstill. The system determines the actual rotor position of the motor at standstill and provides appropriate starting pulses to inverter switches to turn on. Once the motor starts to rotate, it then directly extracts the back EMF from the motor terminals between the floating phase and the mid-point of DC link. Inductance variation sensing method is used for estimating the initial rotor position of the motor followed by a sensorless operation by back EMF sensing method. The principle behind the rotor position estimation is detection and comparison of phase voltage and dc link current responses and relating it with the stator inductances. The most advantage of this method is that it requires only three voltage pulse injections of small duration for the estimation of rotor position. A resolution of 30° can be achieved. The effectiveness of the method is validated by simulation results in Matlab Simulink platform.