Two-Degree-of-Freedom Control with Linear Extended State Observer for PMSM Drive System

In permanent magnet synchronous motors (PMSM) drive system, it is difficult to achieve the optimal performance of command tracking and disturbance rejection simultaneously when the speed loop designed with the conventional one-degree-of-freedom (1-DOF) PI controller. To solve this problem, this paper proposes a speed control structure of two-degree-of-freedom (2-DOF) P-PI controller with linear extended state observer (LESO). There are two sets of parameters that can be designed independently in the controller, which improves the command tracking performance without degrading the disturbance rejection performance. In addition, a linear extended state observer (LESO) is designed to estimate the total disturbance in the speed loop. According to the estimated value, the output of the 2-DOF P-PI controller is compensated feedforward equivalently, which further enhances the disturbance rejection performance. Finally, simulations verify the effectiveness of the proposed control strategy.