Performance of a PLC-based hybrid fuzzy controller for PWM-driven variable speed drive with constant V/Hz ratio

This paper presents the performance of hybrid fuzzy controller in response to several different threshold values. The hybrid-fuzzy consists two control strategies i.e. a PID-type fuzzy logic controller and an incremental PID action. At the early stage of control action, the task is handled by PID-type fuzzy controller. When the absolute of error is less than threshold value, the input of integrator at the output side is no longer given by fuzzy action but fed by incremental PID action. On the other words, the controller output is no longer PI type + PD type fuzzy control but conventional PID + PD type fuzzy control. The controller is simulated under several conditions i.e. sudden change in reference, sudden change in load applied and both simultaneously. The result shows that the lower threshold error value in general gives better performance.