Estimation errors in sensorless drives due to the magnetic interaction

Magnetic interaction or cross-saturation affects the accuracy of the position estimator in sensorless permanent-magnet synchronous drives. To compensate for the estimation error a look-up table or analytic expression can be used. Identifying this estimation error can be done off-line by using a finite-element (FE) model of the machine. Nevertheless, as the FE model has to be simulated with the sensorless controller and for different points of operation, the computation time will be long. Therefore, in this paper, an analytical model is used for which the parameters are obtained from a limited number of FE computations. The estimation error due to magnetic interaction will then be derived from the analytical model directly.