Cascaded fuzzy logic based direct torque control of interior permanent magnet synchronous motor for variable speed electric drive systems

Direct torque control (DTC) is recognized as one of the widespread control schemes in controlling AC motor drives. Thus, in order to maintain a stable performance of AC drives over a wide speed range of operation, this paper presents two cascaded fuzzy logic controllers to be employed in DTC of interior permanent magnet synchronous motor (IPMSM) drive system. The first fuzzy logic controller is used to implement the DTC scheme of IPMSM and the second one is used to control the motor speed. Compared to the classical DTC scheme, the proposed fuzzy DTC strategy uses the estimated torque and flux to determine the switching states of the space vector modulated (SVM) voltage source inverter (VSI). Moreover, the speed controller uses a fuzzy adaptive PI controller to regulate the motor speed at different loading conditions. The fuzzy rules and the membership functions of the two fuzzy controllers are presented. Several simulation results at different operating conditions are presented and discussed.