| As a clean energy, wind power has got a rapid development and also made great progress as an important way to solve the environment pollution and energy crisis. However, with the scale of wind power connection to grid, the impact caused by wind’s randomness and intermittent on the stability and economy of power system has become increasingly obvious, and even caused serious safety problems in the operation of power grid. Therefore, in order to eliminate these adverse effect the wind power can be combined with advanced energy storage technology and using the appropriate capacity of energy storage system in wind turbines to smooth the output power of wind power generation system, which improves the quality of the grid wind power. Basing on the analysis of flywheel energy storage unit and direct-drive permanent magnet synchronous generator(DD-PMSG) and the coordinated control of power converters, the impact of flywheel energy storage unit(FESU) on DD-PMSG system in the case of different grid faults is deeply studied in this thesis.Firstly, the thesis introduced the classification and characteristics of energy storage technology, and compared the various energy storage technology in the application of wind power generation system. Compares with other stored energy technology, the flywheel stored energy may carry on the electrical energy quality and the frequency adjustment because its advantages of high efficiency, rapid charging and discharging, environmental and so on, because this,The composition structure and working principle of flywheel energy storage unit were analyzed in this thesis, and on the basis of analyzing the mathematical model of FESU a simulation model was built to complete the simulation of charging and discharging process.Secondly, the thesis analyzed the mathematical model of DD-PMSG system including wind turbine model, generator model, the network side converter model. On the basis of analyzing the structure and working principle of the DD-PMSG system including the flywheel energy storage unit, and through coordinated control of machine side converter, the network side converter and the flywheel side converter a simulation model of DD-PMSG system was built on the Matlab platform.Finally, the results of the model simulation were compared in different grid voltage dips to get the different variables of the system dynamic characteristics under different grid faults. By analyzing the response curve the flywheel energy storage unit can effectively improve the power characteristic of DD-PMSG system, which improves the quality of the grid wind power. |
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