Advanced Fault-tolerant Control Strategy of Wind Turbine Based on Squirrel Cage Induction Generator with Rotor Bar Defects

Abstract

Several research works in Wind Energy Conversion Systems (WECS) based on Squirrel Cage Induction Generator (SCIG) are developed for isolated site applications. Where, WECS are usually controlled by the Maximum Power Point Trucking (MPPT) algorithm in order to extract the maximum power from wind with constant operating point of SCIG. However, this WECS based on SCIG generator suffers from the problem of breaking rotor bars, therefore a failure in rotor bars is particularly a challenging task because: 1) it can change the operating point generated by MPPT algorithm, 2) increase mechanical vibrations, 3) affect the operation of gearbox, 4) inject a harmonic current in the grid. Therefore, Fault Tolerant Control (FTC) scheme is necessary to allow an optimum energy production, to reduce the maintenance costs and to increase the WECS availability. In this work, a new fault diagnosis approach based on frequency analysis of stator currents is used to detect the failure in bars of SCIG, then FTC algorithm is developed to adjust the pitch angle in max wind speed zone by determining a new operating point according to the wind speed, which leads to extend the lifetime of WECS. Simulation results using MATLAB SIMULINK showed a nominal current in healthy rotor bars and the lifetime of WECS was increased.