Parameter Robustness Sensorless SynRM Drives via LUT-Driven Position Error Compensation for Nonlinear Flux Observer

This article studies the parameter robustness issues encountered in the application of nonlinear flux observer (NFO) in position-sensorless control of synchronous reluctance motors (SynRMs). The nonlinear structure of the NFO poses difficulties for parameter robustness analysis, which has only been studied through simulation in the past. In addition, the magnetic saturation characteristics of SynRMs exacerbate the risk of parameter mismatch. These factors pose challenges to the stability of NFO-based SynRMs sensorless control. In response to this problem, this article elaborates on a methodology dedicated to parameter robustness analysis and enhancement. First, for the NFO based on inductance lookup tables (LUTs), the coordinate transformation is applied for its error system analysis to evaluate the impact of parameter mismatch. Then, the convergence analysis of the error system with parameter mismatch is realized using the phase portrait. Considering the distributed effects of parameter mismatch on the NFO, the idea of lumped position error compensation is investigated to enhance the parameter robustness of the NFO. The position error caused by parameter mismatch can be extracted for compensation by estimating an auxiliary flux vector under the estimated dq-axes. Thus, a position error estimator based on flux observer is developed to compensate for the position error caused by the parameter mismatch. Comparative experiments are conducted in a 7.5-kW SynRM platform to verify the studied algorithm.