Fuzzy Controller for Efficiency Maximization of Induction Motors Connected to Islanded Network Powered By Wind Turbine Generation Using Optimum Constant Ratios of V/Hz and V/Hz3

In the remote area or offshore electrical installation, efficient power network is required. In many application wind turbine farm is used and operated isolated from the grid. In such cases, the frequency can be fluctuated with high range. This can affect the induction motor torque and efficiency. Typical solution for such problem is to use DC link to control the frequency. This method is costly and consume high power losses. The purpose of this paper is to design fuzzy controller for the induction motor to deliver the motor at the required torque and at highest possible efficiency. For that, combined fuzzy motor controllers based on linear dependency (V/Hz) and cubic dependency (V/Hz³) are developed for LV induction motor. The fuzzy controller receives frequency signal as input from the network and estimate the required firing angle of a full-wave thyristor circuit that receives power from the wind turbine and connected in series with the induction motor to control the voltage at motor terminal. Fluctuation of the power supply frequency during the starting and running condition of the motor are considered in the fuzzy controller design to select the optimum applied voltage to the motor for both cases. MATLAB Simulink is used to simulate and test the controller and the motor operation during the starting and running for the full applicable range of frequency. The output of the simulation results show the designed controller is fast and accurate. Comparison between the obtained results and the DC link method results is provided. From this comparison it was noticeable that at all input power range, the efficiency of the pump-motor system is considerably improved by using the proposed fuzzy controller. The minimum gain in the efficiency is 16.67% occurs at 800-Watt input power.