High Order Disturbance Observer Based PI-PI Control System With Tracking Anti-Windup Technique for Improvement of Transient Performance of PMSM

In this project, designing of a disturbance observer-based control (DOBC) system for PMSM drives. The cascade structure of the discrete-time PI-PI control system with tracking anti-windup scheme has been designed for both loops. In this study, high order disturbance observer (HODO) based control is used to improve the speed tracking performance of the control system for the PMSM prototyping kit regardless of the disturbance and unmodelled dynamics. The motion equation was modified in the HODO in which torque losses due to the drug resulting from the time-varying flux, hysteresis, and friction have been taken into account to estimate the total disturbance. 

The HODO does not require the derivatives of the disturbance to be zero, like in the traditional ones. It demonstrates its ability to estimate along with a load torque the high order disturbances caused by a cogging torque and a high-frequency electromagnetic noise in the PMSM system. In the real-time experiments, the proposed algorithm with HODO achieves less speed errors and faster response comparing with the baseline controller. The performances with proposed and baseline control have been evaluated under mechanical speed and load torque variation cases. The experimental results have proved the feasibility of the proposed control scheme.

Keywords: Disturbance observer based control, high-order disturbance observer, PI controller, PMSM, cascaded PI-PI, load torque observer.