Disturbance observer based speed control of PMSM using fractional order PI controller

In this paper, fractional order PI ( FOPI ) control is developed for speed control of permanent magnet synchronous motor ( PMSM ). Designing the parameters for FOPI controller is a challenging task, especially for nonlinear systems like PMSM. All three PI controllers in the conventional vector controlled speed drive are replaced by FOPI controllers. Design of these FOPI controllers is based on the locally linearized model of PMSM around an operating point. This operating point changes with the load torque. The novelty of the work reported here is in use of Non Linear Disturbance Observer ( NLDO ) to estimate load torque to obtain this new operating point. All three FOPI controllers are then designed adaptively using this new operating point. The scheme is tested on simulation using MATLAB / SIMULINK and results are presented.