A Parameter-Independent Optimal Field-Weakening Control Strategy of IPMSM for Electric Vehicles over Full Speed Range

The rest if this article proposes a field-weakening control strategy along with two characteristic curves of IPMSM under electric vehicle driving conditions, where the operation speed, load torque, and target torque change rapidly and continuously. Two characteristic curves, the maximum torque curve, and the switching torque curve are introduced to obtain a strategy that can generate the optimal operation point with minimum stator current at any machine speed. The reference current of the optimal operation points can be derived from both calculation method and conventional calibration method. However, sometimes it is difficult to get solutions directly by the calculation method, not to mention it relies on precise motor parameters that vary with the temperature and magnetic saturation. Additionally, conventional calibration method is really a time-consuming process. In this article, a much simpler approach to obtain reference current based on polynomial fitting is presented, which has a great performance on fitting precision and much less workload with only one additional operation point to be calibrated except for the two characteristic curves. With this fitting method, the reference current generation procedure becomes completely parameter independent. The proposed strategy is demonstrated through simulations and test bench results.