Research On Intelligent Fault Tolerant Control Pitch System Of Wind Turbines With Front-end Speed Control

The application of the new front-end speed regulation unit based on the hydraulic torque variation technology, which can effectively solve the grid pollution caused by the traditional wind power generation and security problems, improve power generating quality. At the same time, the electric pitch system in the wind turbines influenced by its own components’ working lives and the poor working conditions will cause the inevitable malfunction which can result in the unsuccessful performance of the pitch function, consequently causing a huge property loss. Given that, It is very necessary to study the current of failure prone parts and speed sensor using fault-tolerant control method respectively. It will play a positive and effective role for the development of China’s wind power industry.In this thesis, the structures of wind turbine and the electric pitch system are described. The dynamic model of the asynchronous motor is analyzed. The mathematical model based on rotor flux oriented vector model is reached. The electric pitch system model include position, speed and current closed-loop control is built. Different controller is selected for each closed-loop depending on the different control objectives.For the current sensor failures in electric pitch system, a variable universe fuzzy intelligent fault tolerant control method of the electric pitch control system based on single current detection is proposed. To ensure the stability of closed-loop system the method updates the three-phase current using modulation method within any two adjacent sampling period in time. Switches and fault tolerance control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold. For reconstructed signal error caused by the modulation method and main control target of electric propeller system, a variable universe fuzzy control method is used in the speed loop to mprove the system ability to resist load disturbance and the robustness of fault tolerance system. Results show that the fault tolerant control method makes the variable propeller system still has the ideal control characteristic in the case of sensor failure by sacrificing part of the performance of the system, and verified the correctness of the method.For the speed sensor malfunctioning problem of the electric pitch system, a fault tolerant control method based on a full-order flux observer is put forward. Taking the rotor flux and the stator current as the input variables for the full-order flux observer, the feedback gain matrix is emphatically studied. While the monitoring sensors are working, the malfunctioning problem can be diagnosed; when the results turn out to be the speed sensor’s failure, the rotating speed will be estimated by the flux observer. Using it to replace the fault speed sensor can ensure the stable of closed-loop system and ultimately the fault tolerant control of the pitch system speed sensor can come true. Considering the motor stator resistance fluctuations can cause the precision of the speed identification loss, the self-adaptation rate of the rotating speed and resistance are analyzed and derived. The results show that the fault-tolerant control of the electric pitch system can be achieved, which rightly verify the correctness of this method.