Research On Capacity Configuration And Control Strategy Of Hybrid Energy Storage System For Smoothing Wind Power Fluctuation

With the deep-learning of renewable energy power generation technology,the replacement of traditional fossil energy by clean energy,such as wind energy and solar energy,has become the core issue concerned by all over the world.Due to the influence of natural environment,wind energy has the characteristics of randomness,fluctuation and intermittence.Therefore,unstable large-scale wind power integration will bring damage to power quality,system stability and power generation dispatch.In the wake of developments in power electronics technology,energy storage systems are usually installed in wind farms.Hybrid energy storage systems combined with high energy density and high power density can smooth wind power output well.The capacity configuration and control strategy of the energy storage system directly affect the grid-connected power and system economy.Therefore,this paper mainly studies the optimization of capacity configuration and control strategy of the hybrid energy storage system.The main content covers the following:1?The principle and topological structure of hybrid energy storage system is constructed according to its control ability and system economy.Then,the structure and working principle of lithium-ion batteries and supercapacitors are introduced and analyzed respectively.The equivalent circuit model is established according to the characteristics of energy storage equipment.Finally,the relationship between state of charge and voltage of lithium-ion batteries and supercapacitors is analyzed based on the equivalent circuit model.2?Based on the analysis of the characteristics of wind power output and the Fourier transform of wind power,it is concluded that in order to meet the technical requirements of grid-connection,the low-frequency power should be directly connected to the grid and the medium and high-frequency power should be allocated to the hybrid energy storage system.The energy storage system is equipped at the outlet of wind farm considering the economy,and the capacity configuration model of a wind farm is established in Matlab.The reference power of hybrid energy storage system is obtained by the moving average filter.The frequency dividing point is calculated by the marginal spectrum obtained by variational mode decomposition and Hilbert transform.The power of low frequency and high frequency bands is distributed according to the physical characteristics of the supercapacitor and lithium battery.Finally,the system economy is evaluated.3?Considering the relationship between charging and discharging depth and service life of hybrid energy storage equipment,this paper presents a SOC fuzzy feedback control strategy applied to secondary power regulation of energy storage system.Compared with traditional particle swarm optimization and the grey wolf algorithm,the cuckoo algorithm has good prediction accuracy in short-term wind power prediction.According to the difference between predicted charging state and reference charging state,DC/DC converter adjusts power output in time to avoid overcharge and overdischarge of lithium batteries and supercapacitors and prolong service life of equipment.By comparing the proposed control scheme with the non-control scheme,it is concluded that the fuzzy control strategy not only meets the objective of output power fluctuation,but also optimizes the charge/discharge of hybrid energy storage system,and achieves economic benefits and application value.