Steady-State Performance Improvement for LQR-Based PMSM Drives

Considering the periodic disturbances caused by non-ideal factors like dead time effect, permanent magnet flux harmonics, and current sampling errors in the permanent magnet synchronous motor (PMSM) drives, this paper establishes an augmented state space model (SSM), which contains information of periodic disturbances, and then more accurate description for the PMSM system is achieved. Meanwhile, since the three augmented state variables related to periodic disturbances in the augmented SSM cannot be measured directly, a novel periodic disturbance observer (PDO) depending on the Kalman filter is designed to estimate these state variables. On the basis of the augmented SSM and PDO, a linear-quadratic-regulator (LQR)-based state feedback controller is established, which can achieve a successful suppression of periodic disturbances and at the same time ensure a more smooth speed output. Finally, the proposed PDO-LQR is tested in a 6 kW PMSM, and the experimental results show that the proposed controller can efficiently improve the steady-state performance of the PMSM system without sacrificing dynamic-state performance.