Development of 4-quadrant sensorless control of SRM drives over the entire speed range

Proper synchronization of the excitation with respect to rotor position is essential in optimal control of switched reluctance motor (SRM) drives. To avoid additional cost, size and unreliability caused by external position sensors, magnetic status of the SRM can be directly monitored to detect commutation instants. A one-to-one correspondence between magnetic status of the SRM and rotor position removes the need for an explicit access to rotor position. In order to obtain a good precision over the entire speed range, educated modifications on the structure of the sensorless strategy is necessary. This is due to the impact of operational regions on dynamic behavior of the SRM. Introduction of SRM technology to industrial and domestic applications has raised the need for four-quadrant operation of SRM drive. The present paper introduces a range of strategies that are necessary to accommodate this requirement in a sensorless format. Our experimental findings indicate that high-grade sensorless operation in a four-quadrant SRM drive is possible and can be integrated to a variety of applications.