Online MTPA Angle Search Method Using Flux Linkage Plane Estimation of SynRM

The synchronous reluctance motor (SynRM) has attracted attention as a low-cost, resource-saving, and high-efficiency motor. Maximum torque per ampere (MTPA) control is one method to control the SynRM with high efficiency. However, it is difficult to derive MTPA conditions for the SynRM because its inductance varies significantly depending on the current due to magnetic saturation. This paper proposes an online MTPA angle search method. In the proposed method, the flux linkage plane is modeled, and the model parameters are identified using the recursive least squares (RLS) method. The MTPA search is achieved using the estimated flux linkage plane and the gradient ascent method. This study conducted various experiments to evaluate the performance of the proposed online MTPA angle search method. The proposed method is effective for a wide current range, resistance variation, and position error.