Performance Improvement with a Robust Self Tuned Fuzzy Logic Controller for Generator Control in Wind Energy System

Abstract

In this paper a line excited cage generator is considered which is connected with the grid through a bidirectional PWM converter- inverter system. The generator is controlled by indirect field oriented control (IFOC) scheme. Fuzzy logic controllers (FLC)are used for the control purpose. The first FLC is used in the outer speed loop to track the generator speed with the reference speed for maximum power extraction and the second and third FLCs are used in the inner current loops for control of active and reactive power. The FLCs use normalized values of error and change of error as their inputs. The outputs of the FLCs are again multiplied with gains to give the control signals. A trapezoidal membership function is taken for the error input and triangular membership functions are taken for change of error as well as output. Again a robust self tuned fuzzy logic controller (STFLC) scheme is used in place of the FLCs. In this scheme a tuning FLC (TFLC) is used to tune the output gain of the main FLC. The inputs to both the FLCs are normalized values of error and change of error. The output of the TFLC is the output gain of the main FLC. The main FLC is similar to the FLC as discussed in the previous scheme. In the TFLC triangular membership functions are used for all input as well as output variables. The performances of both the schemes are simulated and a comparison is given. The simulation work is done in MATLAB coding environment.