A mutual MRAS identification scheme for position sensorless field orientation control of induction machines

A mutual model reference adaptive control system (MRACS) containing two models is proposed to implement position sensorless field orientation control (FOC) of an induction machine. For the rotor speed estimation, one model is used as a reference model and another is the adjustable model. Pure integration and stator leakage inductance are removed from the reference model, resulting in robust performance in low and high speed ranges. For the stator resistance identification, the two models switch their roles, that is, the reference model becomes the adjustable model and the adjustable model becomes the reference model. Assuming a brief stable rotor speed interval, the stator resistance can be tracked very well. To improve further the estimation accuracy of rotor speed and stator resistance, a simple online rotor time constant identification is included. This mutual MRACS scheme is a cost-effective approach for position sensorless variable speed implementation. Computer simulations and experimental results are given to show its effectiveness