A Fuzzy logic controller for AC/AC converter

A FUZZY LOGIC CONTROLLER FOR AC/AC CONVERTER (Ph.D. Thesis) Hamid ARDAM GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY April 2002 ABSTRACT High power AC/AC converters which are the combination of AC/DC and DC/AC converters, have a problem in low frequency and low voltage in terms of load current interruption in variable speed control of ac motor. In order to minimize the load current interruption and minimize injection of harmonics of nonlinear load and inverter into the AC supply, which disturbances line power quality standarts, a three stage AC/AC converter with combination of AC/DC DC/DC DC/AC converters is realized. A DC/DC converter is designed to be used between AC/DC and DC/AC converters as buffer and voltage regulator. Control of combined converter is implementted by fuzzy logic controller. The performance of the system is evaluated under PI and fuzzy logic controller in the simulation environment and results are discussed. Results show that system performance is better under fuzzy controller and DC/DC converter is effective for harmonic minimization. In application, the fuzzy control algorithm is implementted on ST52x420 microcontroller. A three phase Asynchronous motor is connected as a load and the speed of the motor is controlled. The simulation and application results are compared and discussed. Science code Key Words Page Number Advisor 626.01.00 AC/AC Converter, Fuzzy Logic control, PWM inverter 160 Prof. Dr. Ismail COŞKUN