An improved physics-based phase variable model of PM synchronous machines obtained through field computation

The study of sensorless control of PM synchronous machines at low speed or at standstill requires a machine model which includes highly detailed and accurate information on the saliency. To meet these requirements, the physics-based phase variable model previously developed by these authors is improved here by including the inductance variations with the armature currents. As a result, the improved model considers all the possible factors affecting the inductances, including the rotor position, the armature currents, and the nonlinear magnetization of the core. The inductances required are obtained from the steady state solutions of nonlinear transient field computations covering a complete ac cycle. In this paper, the improved model, the procedure used for the inductance determination through field computation, and the implementation of the improved model are presented.