Novel Sensorless Control Algorithm for SyR Machines Based on Low Speed Active Flux

This work deals with encoderless control of synchronous reluctance machines at low and zero speed. The algorithm is based on active flux method, often exploited to retrieve the rotor position at sufficiently high speed. Being a model based technique, the active flux commonly fails when the speed is too low due to lack of back-emf and so low signal-to-noise ratio, and is impossible at standstill. The active flux concept is now generalized and extended to cover also the low speed range, where the control is enhanced by HF voltage injection. The fundamental and HF machine models are decoupled, permitting to exploit the model based algorithm also at standstill. The proposed technique was experimentally tested in a 1.1 kW motor prototype with promising results.