Rotor Position Error Compensation in Sensorless Synchronous Reluctance Motor Drives

A new approach to compensate rotor position errors caused by parameter mismatching in model-based sensorless synchronous reluctance (SynchRel) motor drives is presented in this article. According to the proposed approach, the error in estimating the rotor position is detected by injecting some low-frequency current signals and adjusting the estimated rotor angular position through a gradient descent algorithm until minimizing the ripple generated on the estimated rotational speed. A rotor position correction can be fully online accomplished coping with saturation and cross saturation effects, as well as with unmodeled phenomena and unpredictable variations of the stator resistance with the temperature. The correction procedure can be accelerated by starting from an approximated correction table, which can be offline built using the same technique. The proposed approach neither needs additional current or voltage sensors nor motor design modifications, thus providing an inexpensive mean to improve the control performance and robustness. Although originally conceived to deal with back EMF-based sensorless control techniques, the correction procedure can be extended to other model-based sensorless SynchRel motor drives.