Online Incremental Inductance Identification for Reluctance Synchronous Motors

The paper deals with the online incremental inductances estimation of a synchronous motor at low speeds using a high-frequency voltage injection. The control scheme is analogous to that used in position estimation algorithms, with the difference that the current control and the rotating voltage injection operate on the real dq axes. Thus a position sensor is required to apply this method. The corresponding current response is measured, filtered, and processed with an ellipse fitting technique. The estimated ellipse coefficients are then used to retrieve the incremental inductances online without the need of any post processing. A novel formulation to express the estimation error valid for other conventional signal injection techniques is presented. The method has been validated experimentally on a reluctance synchronous motor at locked rotor and during load and speed transients.