Research On Variable Structure Control Of Variable Speed Constant Frequency Wind Turbine

With the development of world economy and the progress of human society, the consumption of fossil energy is increasing sharply. People have to seek new renewable energy facing the danger of depleting fossil energy. The generation technology of wind power is becoming mature as wind energy is clean and renewable. Variable speed constant frequency (VSCF) doubly-fed wind power generator is wildly used in many wind farm and has become a hot spot of research.Firstly, the vector control technology of the orientation of doubly-fed machine's stator flux is studied systematically in this paper, and the traditional double PI control system is also simulated. Then, in order to improve the dynamic performance of the decoupling control of doubly-fed motor's active and reactive power and improve the regulation time and overshoot, the sliding mode variable structure control is applied, whose advantages and disadvantages are analysed. The simulation and test results show that the sliding mode variable structure control can improve the dynamic performance of the system well, but at the same time, it leads to another new problem—buffeting. In the end of the paper, after synthesizing the two control methods above, a new control strategy is put forward—compound sliding mode control. The control strategy synthesizes the technology of PI control and sliding mode control, in which a PI controller is in parallel with the sliding mode controller. The model of doubly-fed wind power generation system is set up by Matlab/Simulink to carry on simulation analysis. Compared with the results of PI control and sliding mode control, the simulation results show that the compound sliding mode controller can control the problem of buffeting effectively, realize the decoupling of doubly-fed generator's active and reactive power, and exhibit better dynamic response performance than PI control and sliding mode control. The system can keep original stable state and keep the advantage of strong resistance to disturbance when the parameters of doubly-fed motor change. The system has strong robustness.