| Using energy storage system is an effective way to improvegrid-connected characteristic of wind power and the capability of power gridabsorbing wind power. At present, many energy storage techniques are used inwind power generation, and battery storage system and supercapacitor storagesystem is more widely used. However, restricted by the energy storagemechanism and technical level, the single battery or supercapacitor energystorage system can not provide high power and high energy at the same time,which can not fully meet the requirements of smoothing the wind power output.Therefore, the lithium battery-supercapacitor hybrid energy storage system andits Application in wind power generation are studied.Firstly, the characteristics as well as the modeling of lithium battery andsuper capacitor are studied. Based on the analysis of the existing models, thePNGV Model is selected because it is preferable to simulating thecharacteristics of LiFePO4battery used in wind power generation. Theemphasis is put on the identification methods of PNGV model parameters. Inthe light of the shortage of the method of discharge static for identifyingparameters of the open circuit voltage, the method of continuouscharge-discharge experiment is proposed, which can obtain open circuit voltagedata simply and fastly. The resistance and capacitance parameters of the modelare calculated by hybrid pulse power performance testing on LiFePO4battery.The characteristics and existing models of supercapacitor are analyzed, and asimple RC series model is used to simulate the supercapacitor. The model ofLiFePO4battery and supercapacitor is established respectively, the simulationresults demonstrate the validity of the model.Secondly，the hybrid energy storage system structure is designed, and thecontrol strategies of hybrid energy storage system is deeply researched. Basedon the characteristics of the little changes of lithium battery terminal voltage,the structure of lithium battery directly coupled to DC bus of hybrid energystorage system is presented, which can save a DC/DC converter, simplify thecontrol process and reduce the loss of system; the control strategy of smoothwind power fluctuations is researched based on the low-pass filtering methods,and using the hybrid energy storage system reduces the specific component ofwind power fluctuations is presented and the power control signal of hybridenergy storage system is obtained through calculating; the corresponding power allocation strategy based on the physical properties of the lithium battery andsuper capacitor is presented; the power and capacity configuration scheme ofhybrid system which can meet the demand of smoothing process is proposed.Finally, the application of the hybrid energy storage technology in windpower generation is researched by simulation. Based on the existing model ofdirect-driven permanent magnet synchronous wind energy conversion system,the wind active power curve is obtained. In view of stabilizing fluctuation ofthis power curve, a detailed process to calculate the power and capacityconfiguration of hybrid energy storage system is given, and the packing methodof LiFePO4batterys and supercapacitors are simply designed respectively. Inthe environment of MATLAB/Simulink，the simulation model is established.The results show the hybrid energy storage system can stabilize the wind powerfluctuation effectively, and it has significant advantages. |
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