Fault-tolerant Control Strategy Research For Wind Turbine System

As one of the most important natural resources, the wind energy has become an important role to solve the problems of word energy. It has an obvious advantage over other resources because the characteristics of clean, enormous energy, sustainable supply. Wind energy equipments are usually built in the mountains or remote areas away from the coast, and the climate change can’t be predicted. So the sensor and actuator fault often occur in this terrible and complex environment. In addition the wind turbine system is a high order, nonlinear, multivariable, strong coupling system, it will become more complex to control subject to uncertain parameters. Thereby, the real-time fault diagnosis and effective faulttolerant control to ensure the reliability of wind turbine system will become more and more important.The paper describes the existing fault diagnosis technology, fault-tolerant scheme of control system and fault-tolerant approaches of wind turbine system in detail. The maximum efficiency of wind energy is introduced based on wind turbine aerodynamic characteristics and the dynamic model of wind turbine system is constructed. Besides, the system operating state is discussed in three different wind speeds. Finally the largest wind energy capture control theory is introduced by calculating the performance parameters and analyzing the curve graph between tip speed ratio and power coefficient.According to the nonlinearity and the strong coupling characteristics among variables of wind turbine system, the global T-S fuzzy model of the system can be easily built because T-S fuzzy theory has simple structure and powerful approximation capacity. Besides, the equivalence output is solved and the sliding mode has strong robust to uncertainty by analyzing the sliding mode control theory. The paper chooses suitable sliding surface and utilizes the output signal of high speed shaft speed and electromagnetic torque as the input of controller. So the global fuzzy sliding mode controller can be designed by LMI approach to achieve the closed-loop of wind turbine system. The performance parameters of tip speed ratio and power coefficient are maintained around optimal value to capture largest wind energy in partial load area of wind turbine system.The sliding-mode observer is a nonlinear observer, it can use the inherent robustness to overcome model uncertainties or nonlinearity in fault diagnosis of nonlinear system. So the paper combines the T-S fuzzy theory and sliding-mode observer theory to design T-S fuzzy sliding-mode fault observer, and the fault information can be directly obtained by the equivalence output control concept to reconstruct the sensor fault. Then the input of sliding-mode controller can be replaced by reconstructing the output signal of sensor to contact the fault-tolerant control of wind turbine system.In senor fault and actuator fault system, a residual error logical table is constructed by combing the sensor hardware redundancy technology with state observer to achieve multiple-fault diagnosis. Then the sensor fault can be transformed into actuator fault by a first-order filter to build a virtual actuator faults. Thereby the two faults simultaneous reconstruction can be achieved by constructing the virtual actuator faults. Finally, the sliding-mode theory is combined with adaptive technology to design the actuator fault-tolerant controller to guarantee the system accurately track the expected state and output trajectory.