Angular Voltage Step Excitation Strategy in Induction Machines for Sensorless Position Estimation Using One Single Active Switching State

Among the sensorless control methods, voltage injection strategies stand as the most promising ones in the region of very low speeds. In particular, voltage step excitation method relies on the transient complex inductance measured from such given excitations, thus providing information about machine saliencies. These injections, however, generate additional current ripple, which ultimately creates further acoustic noise to that of the PWM. This paper will provide an approach to integrate the voltage steps into the PWM, injecting them in a way that they rotate together with the fundamental wave voltage, and dealing with the upcoming rotating saliency signal offsets. In order to handle the voltage sector boundaries, only one single active switching state within a PWM cycle will be used to calculate the transient inductance needed for speed sensorless control. Performance of this new excitation method, as well as current ripple and audible noise reduction will be verified by measurement results.