A Stator Flux Observer With Phase Self-Tuning for Direct Torque Control of Permanent Magnet Synchronous Motor

Owing to simple implementation and excellent performance, the conventional stator flux observer based on active flux concept is considered as a competitive scheme for direct torque control system of a permanent magnet synchronous motor. However, it is constructed by a large number of motor parameters, which may vary with the operating points. This leads to weak robustness. To improve its performance, a stator flux observer with phase self-tuning is proposed as an improved version in this article. First, relationship between the stator flux observed values obtained by current and voltage models and observed error of rotor position angle is analyzed. Then, according to the aforementioned analysis, a phase self-tuning link constructed by a proportional-integral regulator is proposed to ensure that the observed coordinate system converges to the actual one even under motor parameters vary conditions. Consequently, the robustness and accuracy of the stator flux observer can be improved. Finally, the stability of the proposed phase self-tuning link is analyzed. Experimental comparison between the conventional stator flux observer based on active flux concept and the proposed improved stator flux observer has been done, and the results verify the feasibility and effectiveness of the proposed stator flux observer.

I. Introduction

With the advantages of high power density, high efficiency, and simple structure, permanent magnet synchronous motor (PMSM) is widely used in industry, such as electric vehicles and locomotive traction [1]–[3].