Research On Control Of Doubly Fed Wind Power System In Case Of Speed Sensor Failure

As renewable green energy source, wind energy has been widely used around the world, and wind power technology has become the most developed technology of clean energy product in the world. With the rapid development of wind power industry, how to improve the security and reliability of wind power system has become an outstanding issue, how to detect fault rapidly and retain operation in spite of malfunction has drawn people's attention. As speed sensor malfunction rate is high, this thesis mainly researches the control strategy of doubly fed wind power generator(DFIG) system in case of speed sensor failure.Firstly, the operating principle of DFIG variable speed constant frequency is studied, and mathematical model of DFIG is presented, furthermore, the grid voltage oriented vector control strategy of DFIG is implemented in detail. Then the theory of grid side converter is analyzed, including the mathematical model and the double closed loop control strategy.Secondly, this thesis researches on the theory and method of fault diagnosis. The state observer is designed for fault detection of speed sensor in DFIG system. The detection method is realized by residuals generation and demonstrated correct by simulation results.Comparing the speed identification methods, the thesis proposes a model reference adaptive control method based on rotor current to estimate the speed, which provides a replacement signal for the failed sensor. Models of DFIG system are set up by Matlab/Simulink, and the simulation results show good static and dynamic performance of the designed speed estimation system.Finally, in order to prove the feasibility of the control strategy, a DFIG wind power system test platform is built in the laboratory. The hardware and software design of the control system are introduced, in addition, experiments are made on the platform. The experimented results show that the control strategy is valid.