Online determination of reference currents for wide-speed range operation of IPMSM in electric vehicles using the Newton-Raphson method

The Interior Permanent Magnet Synchronous Motor (IPMSM) has been widely employed as a preferred choice for electric vehicle (EV) because of its advantageous characteristics such as high efficiency, high-power density, and a robust operation. This paper focuses on the control of an IPMSM for EV applications, with emphasis on smooth transitions over a wide speed range, including both normal and high-speed operating regions. A comprehensive review of state-of-the-art IPMSM control methods is provided, followed by fundamental machine principles. Over-modulation techniques are then presented to effectively manage the maximum voltage of the DC-link source, a critical aspect for EV powertrains. In order to control the machine over a wide-speed range, a flux-weakening method has to be adopted by combining the conventional space vector modulation (SVM) in the normal speed range and the voltage angle control in the high-speed regions. A key innovation of this study is the use of the Newton-Raphson method to determine the optimum operating point of the IPMSM, minimizing the stator current for a given torque demand. This optimization not only maximizes the torque capability over the entire speed range, but also enhances the dynamic performance of the system, which is essential for EV applications requiring rapid and precise response. The proposed control strategy combines SVM with overmodulation techniques, enabling seamless transitions between low- and high-speed regions. Simulation results are used to validate the effectiveness of the proposed control strategy, demonstrating stable and robust performance under varying speed and load torque conditions, highlighting its potential for applications in wide-speed-range IPMSM-based EV systems