A variable gains PI speed controller in a simplified scalar mode control induction machine drive — Design and implementation

The use of PI controllers for speed control of induction machine drives is characterised by an overshoot during start up with a poor load disturbance rejection. To overcome this problem we propose the use of an original variable gain PI (VGPI) speed controller. Each gain value of the proposed controller vary along an appropriate polynomial curve from a start up setting that permits overshoot elimination, to a permanent mode setting that permits a rapid load disturbance rejection. In this paper a VGPI speed controller is designed to replace the classical PI controller in a modified scalar mode controlled induction motor drive. First the simulated performances of the two controllers are compared using Simulink/Matlab software, then a practical implementation is performed in order to validate the simulation results. Both simulation and experimental results demonstrate that the VGPI controller maintains the PI controller properties in permanent region with the advantage of overshoot elimination in the transient mode.