Sensor fault-tolerant control of DFIG based wind energy conversion systems

•An observer-based fault-tolerant control strategy is proposed for a doubly-fed induction generator.•Three robust sensor fault observers are designed to estimate the sensor faults.•The proposed strategy does not require fault diagnosis scheme.•The proposed strategy maintains the current sensor fault-tolerant operation of system. This paper proposes a fault-tolerant control (FTC) strategy for a doubly-fed induction generator (DFIG) based wind energy conversion system (WECS) with sensor faults. The DFIG system is decomposed into stator, rotor, grid current models, and the sensor fault observer (SFO) is presented to provide accurate estimations of sensor fault components in the presence of model uncertainties. Based on the independent current dynamics of DFIG system, three SFOs are designed in parallel to respectively estimate the stator, rotor, and grid current senor fault signals. During the occurrence of faults, the fault estimations derived from current observers are adopted to compensate the faulty signals, thereby achieving the system reconfiguration of DFIG without requiring any fault diagnosis schemes. Simulation studies are undertaken on a grid-connected WECS under the conditions of stepped and random wind speeds, and single and multiple current sensor faults. Simulation and experimental results reveal that the FTC-controlled DFIG system is resilient from the sensor faults and maintains continuous stable operation.