Research On Hybrid Energy Storage Allocation Based On Smoothing Wind Power Fluctuation

With the advancement of electricity market and the rapid growth of wind power installed capacity,consumption of wind power has become the key to wind power development.The fluctuating characteristics of wind power weakens the safety and stability of power systems,prevents wind power consumption via grid connections.Therefore,smoothing wind power fluctuation is an important measure in terms of realizing wind power value,and is of significant importance to the market-oriented power operation.In this paper,based on the characteristics of wind power output,a smoothing strategy based on wavelet domain denoising combined with model predictive control(MPC).Sets hybrid energy storage allocation as objective,coordinated operation of wind power – energy storages as constraints,to smooth wind power fluctuations and realize optimized allocation between hybrid energy storages,fuzzy control theory is used to optimizing the state of charges of the hybrid energy storages,in order to prolong their life cycle.First,this paper analyzes the principles of wind power generation,influential factors and characteristics,establishes a wind power output model,and builds quantitative indicators of wind power fluctuations.The wind power fluctuation quantitative indicators,Discrete fourier Transform(DFT)and wavelet transform(WT)are used to statistically analyzing the wind power output signals in Time Domain,Frequency Domain and Time-frequency Domain separately,to obtain the wind power fluctuation characteristics and energy distribution,this provides a theoretical basis to suppress wind power fluctuations.Secondly,existing wind power output smoothing methods cannot simultaneously take into account the smoothness of wind power and meet the requirements of wind power fluctuations and the minimization of energy storage requirements.To solve this problem,a wind power fluctuation suppression strategy based on wavelet domain denoising combined with model predictive control(MPC)is proposed in the Theses.Compare to the commonly used suppression methods(low-pass filtering,wavelet domain denoising,model predictive control,etc.),the number of fluctuations,the required energy storages and capacities are used as evaluation indications.Examples are given in the paper to show that best results are obtained in terms of number of over-limit wind power outputs,and energy storages allocations.Finally,to solve the problem of economical allocation of hybrid energy storage,energy storage characteristics are analyzed,and a hybrid energy storage system consisting of supercapacitors and lead-acid batteries is established using the complementary characteristics of hybrid energy storage performance.Combined with the proposed wind power suppression strategy,from economic point of view,the comprehensive cost of wind power overrun penalty and the initial investment cost of energy storage is used as the control index to obtain the number of decomposition layers and the energy storage reference power.By combining the frequency and amplitude characteristics of the energy storage reference power with the energy storage characteristics,the dual-type energy storage realizes the first power distribution and capacity allocation.Then,fuzzy control theory is used to make another correction to the output of the dual energy storage,so that its State of Charge(SOC)is within a reasonable range,to prevent reduced service life of energy storages due to excessive charging and discharging.