Improvements on a Sensorless Controlled Synchronous Reluctance Machine Down to Standstill

A position - sensorless controlled synchronous reluctance machine (SynRM) is discussed in this paper. Induction motors (IMs), widely used in industry, achieve a lower efficiency than SynRMs [1][2][3], which leads to higher operating costs. To reduce these costs it is reasonable to replace IMs by Syn- RMs. An additional option to increase the economic benefit is to replace the angular position sensor by implementing sensorless methods. This work shows that improvements on the sensorless behaviour are reached by using a high PWM frequency to reduce the ripple current in the dc-link. This approach reduces the losses in the capacitors and provides a silent operation of the sensorless method at a higher position estimation bandwidth. In order to realise sensorless control at such an increased PWM frequency it is necessary to reduce current sensing noise as well as to improve the observer behaviour by implementation of a non-linear observer of the mechanical system. Experimental results with the prototype are presented and characterise the performance of the improved sensorless method.