Improved sensorless control of switched-flux permanent-magnet synchronous machines based on different winding configurations

In switched-flux permanent-magnet machines, winding coil connections can be rearranged into several types of machine winding configurations (MWCs), such as all poles wound, alternate poles wound, and single and dual three-phase windings. This paper investigates the influence of machine saliency on a sensorless control operation based on different MWCs. First, by injecting an HF carrier signal, the machine saliency level can be evaluated experimentally. The influence of saliency on an HF-signal-injection-based sensorless operation for different MWCs can be then investigated irrespective of any information of machine parameters. However, the secondary saliency caused by magnetic saturation or current harmonics may exist in a machine, due to which the sensorless control performance will deteriorate. Hence, an orthogonal signal-based position tracking observer is proposed to improve the accuracy of rotor position estimation rather than utilizing an existing position observer. Furthermore, experimental results confirm that a prototype machine exhibits different saliency characteristics and apparent saliency, in which the HF-injection-based sensorless control technique can be applied. Moreover, better steady and dynamic state performance can be achieved by the improved position estimator compared with using an existing position observer.