FUZZY LOGIC CONTROLLER FOR VOLTS/HZ INDUCTION MOTOR CONTOL USED IN ELECTRICALLY DRIVEN MARINE PROPELLER

This paper develops the usage of induction motor to drive the marine propeller for producing ship propulsion. In the electric propulsion system, load torque of induction motor is very dynamic because it is influenced by the torque produced propeller and disturbances. The disturbances come from ocean waves, ocean currents, wind, and ship motions. In this paper, a fuzzy logic controller (FLC) is designed to control the speed of induction motor using volt/Hz (V/f) control method. V/f method maintains a constant ratio of voltage and frequency to produce the optimum speed and torque of induction motor. The voltage and frequency is directly controlled by voltage inverter. Fuzzy logic (FL) is one of the artificial intelligence. FL performance is affected by its membership functions. Adaptive process in FL makes improvement of induction motor performance whenever there are changing parameters caused by change of load torque. To clarify robustness of FLC, the induction motor is employed in electric propulsion system. In this system, load torque of induction motor is torque produced by propeller, whereas propeller torque depends on the induction motor speed. Simulation results of designed FLC show that the induction motor rapidly reaches the speed reference, has small steady state error and overshoot. And also load disturbance can be rejected.