A review of advanced field weakening control strategies of PMSMs

Research content

    The study, led by Runze Jing, has summarized the FW control strategies into calculation-based methods, voltage closed-loop control methods, and model predictive control-related methods. The calculation-based method substitutes the target speed and torque into the motor voltage equation to calculate the FW current and voltage reference values. Firstly, the calculation method of FW's current trajectory is introduced, and then the offline calculation method based on the solution of algebraic equations and the online calculation method based on motor model optimization and fuzzy control are summarized. The voltage closed-loop FW control strategy regulates the FW current by comparing the output voltage and the FW limiting voltage, which does not depend on the motor parameters. This method has a simple structure and strong control robustness and can be categorized into dual regulator control and single regulator control according to the control structure. MPC-related methods have been widely studied to solve complex nonlinear constraint problems in each control cycle. The core idea of these methods is to construct a cost function based on predictions and constraints and to compute the output variables that minimize the cost function. The cost function for FW control usually includes speed, torque, current, and flux. Based on the characteristics of the output voltage vector, these methods can be categorized into finite control sets and continuous control sets.

The research results and their significance

     In summary, offline calculation methods, online computational methods, and MPC all depend on model accuracy but offer good current response speed. Online calculation methods and MPC are mainly applied on platforms with strong computational capabilities, while offline calculation methods are mainly used in low-cost industrial products. Voltage closed-loop control methods do not depend on motor parameters and have relatively simple control structures, achieving a balance between computational difficulty and control robustness.

Future outlook

    Currently, FW control strategies for PMSMs have been extensively researched and applied, providing theoretical foundations and implementation methods for high-speed motor drive control. Considering factors such as controller cost, operating conditions, inverter non-ideal characteristics, and motor model uncertainty, there is still a need for further research into the high performance and robustness of FW control. Future research directions for FW control mainly focus on simplifying the computational process of high-precision models and improving the dynamic performance of high-robustness closed-loop control algorithms.