Research On Maximum Power Point Tracking Of Wind Power Generation System With Variable Speed Constant Frequency

As the depletion of oil. coal, natural gas and other traditional fuel and the pollution in environment, the development and utilization of a renewable green energy. wind energy becomes more and more important. At present, with the rapid development of wind power technology, the wind power generation with variable speed constant frequency (VSCF) has received more and more attention for its high efficiency and practicability, and it is a hotspot of the research in the field of wind power generation.First of all, it summarizes, in this dissertation, the trend and the present situation of wind power generation. The aerodynamics model and transmission system model of wind turbine are established on the basis of the fundamental principle of the wind power generation system with variable speed constant frequency, and the analysis of Maximum Power Point Tracking (MPPT) with the operating principles in operating area.Secondly, according to the principle of the Squirrel Cage Induction Generator (SCIG), the mathematical model of the SCIG is established in synchronous rotating coordinate system, on the basis of the characteristics of its operation and power relations SCIG coordinate transformation, and the motor vector control method on SCIG is applied.Then, on the basis of the characteristics of the wind turbine, it is proposed the method based on On-Off control for MPPT of wind turbine as for its advantages of simple structure, independent of the system model, quickly responding to the change of wind speed. And also a control method is proposed based on the theory of sliding mode variable structure to tackle the problem of MPPT of wind turbine which does not need the wind speed measured, and possesses the properties of good dynamic performance and robustness.Finally, in this dissertation, simulation studies were carried out with Matlab/Simulink to establish the simulation models of wind turbine and generator, and the maximum power point tracking of wind turbine system was simulated based on the control strategies of On-Off control and sliding mode variable structure control. The simulation results show that the both two tracking methods can achieve the results of MPPT in the condition of independence of wind. The control system with On-Off control strategy possesses the properties of simple structure and easy implementation, but weaker in transient performance than that of sliding mode control, while MPPT method based on the sliding mode control can track better for the tip speed ratio so that the wind energy utilization coefficient reaches a maximum value, and can quickly realize the maximum wind power capture. The simulation results verify the Feasibility and effectiveness of the proposed control strategies.