Comparative Analysis on Speed Control of a Three Phase Induction Motor Drive Using Proportional Integral Differential and Scalar Closed Loop Fuzzy Logic Approach

Abstract

The principles of controlling an AC driven three phase induction motor employing constant volts/hertz (v/f) control method and the space vector pulse width modulation (SVPWM) technique are reviewed. The induction motor is one of the most common electrical motors in usage, owing to its unique characteristics. Its further application strength requires a robust, problem handling, fast and intelligent speed control system. As a result of this, developing an intelligent knowledge based fuzzy logic controller (FLC) became eminent, and on this basis, this paper is presented. By varying the motor speed with input reference speed, an error signal and a feedback loop is generated. The FLC then operates on the principles of mapping with corrective measure of an error signal generated and it is regulated by sets of programmable IF-THEN rules integrating the Mamdani fuzzy inference approach. The rules projected and formed are used to overcome drawbacks such as complexities and insensitivities to changes in model parameters associated to conventional controllers. The application of the constant v/f method was used to maintain constant voltage to frequency ratio, therefore, creating a constant magnetic field and a maximum torque throughout the operating range. This in turn generates a voltage and an angle command for the actualization of the SVPWM technique. This entire set up was repeated but now with a classical control method like the proportional integral differential (PID) controller. With a simulation time of 2s, results showed that with FLC, a better speed response can be achieved from a 5Hp 350V 50Hz AC motor attaining steady-state at 0.21s at no-load conditions. Simulation results showed a superior dynamic scheme of the FLC over the PI controller in terms of sensitivity to changes in model parameters. With a load torque of 10Nm applied at 1s, the FLC achieved stability at 1.2s still maintaining a constant speed of 157rads/s.