A sensorless commutation technique of a brushless DC motor drive system using two terminal voltages in respect to a virtual neutral potential

In this work, a sensorless commutation technique for the operation of a BLDC motor drive system is proposed. The idea is to derive back electromagnetic force zero crossings from two motor terminal voltages in respect to a virtual neutral potential. The commutation instances can be properly defined via a 30° electrical degrees phase shift of the correspondent back EMF zero crossing point in each motor phase. The use of filters or integrators is avoided and therefore the speed operating range is extended. Simulation results verify the effectiveness of this sensorless method.