| With the traditional fossil energy reserves declining and environmental problems worsening,it is imperative to adopt clean and renewable new energy sources.As the most widely used new energy technology of wind power generation,it doesn’t pollute the environment in the process of its production and utilization,so it has become the object pursued by all countries.The total installed capacity of wind power in China has reached the world’s first in 2017.However,the output power of wind power has the limitations of volatility,intermittency and randomness.Its large-scale grid interconnection will have a tremendous impact on the power grid.Energy storage system access can effectively smooth wind power fluctuations.Considering hydrogen has the advantages of high calorific value,large energy density and no pollution after combustion,the supercapacitor have the features of high power density,long life cycle and fast response.In this paper,a new hybrid energy storage system based on hydrogen storage and supercapacitor energy storage is proposed,which can be used to stabilize wind power output power fluctuations and achieve grid-connected friendly.This paper mainly includes:1.Building model of wind power-hydrogen coupling system and research the model characteristics and principles of wind turbines,supercapacitors,electrolyzers,hydrogen storage tanks and fuel cells in the system.2.In order to meet the requirements of grid-connected power fluctuation in wind farms,a power-stable control strategy and capacity allocation method based on spectrum analysis and wavelet packet decomposition algorithm are proposed.On base of the analysis for the spectrum characteristics of wind power,it is firstly decomposed into low frequency component as grid-connected power and high frequency component by wavelet packet decomposition.The high frequency component is divided into medium-high and highest,the electrolytic cell is used to smooth medium-high component and the supercapacitor is used to smooth highest component.Besides,the method of fourier approximation is adopted to fit the probability density function so that the best capacity configuration of energy storage system can be calculated finally.Based on the measured data of wind farms,both the working characteristics of energy storage equipment and the fluctuation of grid power are taken into account simultaneously,the simulation show that the proposed method can achieve grid-connected friendly of wind power.3.Based on the wind-hydrogen coupling system following a given power curve,the control strategy that the energy storage priority of charging and discharging of the super capacitor is higher than the hydrogen energy storage system is proposed,and the superiority of this strategy is studied.The operating characteristics of the wind-hydrogen coupling system are analyzed,and the coordinated operation method of the system is established.The paper takes total cost of the system,loss of power supply probability and absolute value of fluctuation of wind power as the objective function,and build capacity optimization model.The particle swarm optimization algorithm is used to optimize the capacity.The case study shows that the proposed scheme can find a balance between the system economy and the dispatching characteristics,the optimal capacity is validated at the same time to verify the technical rationality of the proposed method of operation. |
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