Control Method of HTS Permanent Magnet Synchronous Machine With a Nonlinear Disturbance Observer

The high temperature superconducting (HTS) permanent magnet synchronous machine (HTS-PMSM) uses the HTS armature winding instead of the copper armature winding, having higher torque density and higher efficiency and showing a great application prospect. Although the mathematical analysis model of the HTS-PMSM is similar as that of the conventional PMSM with the copper armature winding, as the load current increases, the stator core of the HTS-PMSM is more likely to be saturated, the inductance of quadrature-axis and direct-axis will be reduced. That leads that the power density and overload capacity of the HTS-PMSM will be affected, the control performance of the controller will be reduced as well. In order to solve the problem of the great change of the inductance values with the load variation, this article proposes a nonlinear disturbance observer (NDOB) to estimate the disturbance of inductance parameter caused by the core saturation of the HTS-PMSM and builds a compensation strategy, combining with robust sliding mode control (SMC) to improve the stability of the speed and torque of the HTS-PMSM. The effectiveness of the proposed control method is verified by the combination method of the finite element analysis and Matlab/Simulink simulation.