FEEDFORWARD LOAD TORQUE COMPENSATOR COMBINED WITH PI SPEED CONTROLLER FOR HIGH DYNAMIC PERFORMANCE OF PMSM DRIVES

Document Type : Original Article

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Electrical Engineering Dept., Faculty of Engineering, Minoufiya University

Abstract

This paper presents a PI speed controller in conjunction with a feedforward load torque compensator in order to improve the dynamic performance of permanent magnet synchronous motor (PMSM) drives. The load torque estimator is used to provide a feedforward value in the speed controller in order to decouple the load torque from the speed control. This method can improve the PMSM dynamic performance against the disturbance torque without increasing the speed controller gain due to stability limitations. This can be achieved by dividing the electromagnetic torque in a feedforward value which should compensate the load torque, and a dynamic value which takes account of the speed variation. The load torque estimator compensates the speed control by setting a feedforward torque value through the q-axis current reference value. Therefore, the speed controller reaches immediately the speed reference value and a better response to load torque variations, which are detected and compensated leading to small speed variations, is obtained. The proposed controller with load torque compensator is examined through both simulation and experiments. The performance of IPMSM drive system with a conventional proportional-integral (PI) controller is presented in comparison with the proposed controller. The results show a significant improvement of the proposed controller, particularly during load torque variations and parameter variations.

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