Research On Fluctuation Smoothing Of Wind Power And Joint Dispatching Of Wind-Storage System Based On Time-Frequency Analysis

In recent decades,due to energy crisis,environmental pollution and other problems,wind energy,a clean resource,began to be widely used,and its penetration in power systems gradually increased.However,due to the influence of climate and geographical environment,wind power is intermittent and fluctuating,which affects the power quality.In addition,the rapid change of wind power increases the difficulty of power system dispatching,which may lead to serious security and stability problems.Energy storage has the advantages of rapid response,high reliability,flexible charge and discharge.It can smooth the fluctuation of wind farm output and improve the controllability of wind power.It also helps to improve the stability and economy of power system operation.The participation of energy storage in wind power fluctuation smoothing and joint dispatching of wind-storage systems has become a hot research topic at home and abroad,and it is of great significance.Time-frequency analysis method can extract the stationary and non-stationary characteristics of wind power from both time and frequency domains,which has certain advantages in analyzing non-stationary signals such as wind power and wind power fluctuation.In view of this,this thesis studies the issues related to the participation of energy storage in wind power fluctuation smoothing and joint dispatch of wind-storage systems from the perspective of time-frequency analysis.The main research contents of this thesis are as following:(1)Time-frequency analysis method is used to analyze the wind power and wind power fluctuation.The time-frequency characteristic indexes are established based on the wavelet packet transform,which reflect the volatility and randomness of wind power.The time-frequency characteristic indexes of wind power are analyzed,and the characteristics of both wind power and wind power fluctuation are evaluated from the perspective of time-frequency domain,which provides a reference for the stabilization of wind power fluctuation.(2)For wind farms,an improved wavelet packet wind power fluctuation smoothing method based on time-frequency analysis is proposed,and grid-connected wind power after fluctuation smoothing and power commands of energy storage system obtained.Then,an adaptive dual-layer optimization method based on Haar wavelet is established for energy storage configuration.The simulation results show that the improved wavelet packet fluctuation smoothing method can reduce the cumulative power and charge discharge switching times of energy storage power command on the basis of satisfying the fluctuation standard,and the energy storage configuration method based on Haar wavelet can reduce the energy storage configuration cost and prolong the battery life.(3)For power grids,a joint dispatching method of wind-storage systems based on timefrequency analysis is proposed.The equivalent load is calculated out according to the predicted value of power load and the wind power after fluctuation smoothing,and the Haar wavelet packet decomposition is used to extract the high frequency component reflecting the rapid change of the equivalent load and the low frequency component reflecting the regular change of the equivalent load,and then the high frequency component is involved into the maximum charge-discharge power constraint of battery energy storage.Taking the minimum comprehensive operation cost of the wind-storage systems as the objective function,joint dispatching model of wind-storage systems based on time-frequency analysis is constructed.Finally,the model is solved by CPLEX solver in the optimization software GAMS and case studies verify the effectiveness and rationality of this method.