Stator flux based speed sensorless control of single phase induction motor drives

Single phase induction motors (SPIM) are widely used at low power levels because of their simple construction, robust nature and nominal price. Conventionally, they have one operational stator winding and the speed of the motor is not controlled. But SPIM drives for higher power levels have both main and auxiliary winding remaining operational throughout and can be treated as asymmetrical, two-phase machines. High performance operation of these asymmetrical machines is associated with the problems of modeling the asymmetry and controlling the electromagnetic torque oscillations. Different research groups have proposed different schemes to tackle the above said difficulties. In this paper, a novel vector control scheme is proposed based on the simplest mathematical model that works for diverse speed ranges far below and much above the base speed and excludes the traditional complexities found in high performance SPIM logics. Stress has been given on simplicity in modeling the asymmetry and designing the controllers. The controllers are simulated in synchronously rotating reference frame for which the stator voltages are transformed to synchronous reference frame by removing the asymmetrical terms and adding them later as decoupled voltages. The simulation results are given for various speeds below and above base speed to indicate the versatility of the scheme. To improve its adaptability, speed sensorless algorithm has also been added.