The Research Of Control Method For Stand-alone Wind Generation System

This paper studies the optimal control strategies of stand-alone wind power generation system. The configuration is proposed according to characteristics of stand-alone wind power generation system, including wind turbine, drive train, Permanent Magnet Synchronization Generator (PMSG), three-phase rectifier, Buck converter, battery, inverter and AC load. A Buck converter is adopted in this system to improve the operating efficiency and control flexibility, comparing to the conventional small wind turbine system. This system apply parallel load configuration. The generator supply to battery and AC load at the same time. Meanwhile, the battery and generator can supply to AC load together.On the basis of the analysis of the system parts characteristics, a reasonable system equivalent model to established. Based on the model, the paper studies how to design wind turbine controller, enables the system operating in the vicinity of the maximum power point, when the wind speed below the rated wind speed. That is the tip speed ratio lies in the optimal value. This goal is achieved by controlling the Buck converter duty cycle, equivalent to change the generator load, making the generator track the optimal rotational speed, implementing maximum power tracking.Because the system is highly nonlinear system, but with smooth nonlinearities, the stand-alone wind power generation system can be linearized through strict state transform and feedback. A controller is designed based on the feedback linearization techniques, and the Matlab / Simulink simulation model is established. The simulation results are given.Because the system uncertainty under different wind speed, the non-linear stand-alone wind power generation system can be converted into a series of system transfer functions; these functions reflect the uncertainty of the system. Based on quantitative feedback theory, a robust controller is designed. System Matlab/Simulink simulation model is established and simulation results is given.The simulation results show that the above-mentioned two types of control method can effectively implement maximum energy capture under rated wind speed, even if the wind speed changes in a large range. It's of great significance to the optimal operation and reliable operation of the stand-alone wind power system.Finally, this paper specially studies the important component of the system—battery, a dynamic simulation model of the battery is constructed based on improved Shepherd model. Simulation using the battery model thus makes it possible to analyze complex electrochemical phenomena. Simulation results show that the discharge curves of model and manufacturer are basically the same, the model can correctly represent the battery behavior. On this basis of model, a certain accuracy charge and discharge control of battery can be achieved. Finally, a stand-alone wind power systems with battery model be established, the simulation results show that the battery model is consistent with the theoretical analysis, can represent systems dynamic behavior, lay the foundation for follow-up study.