Research On Hybrid Energy Storage System Control Of Battery And Supercapacitor

Due to the increasing depletion of fossil energy and the growing environmental problems caused by the large amount of burning fossil energy,people have paid more and more attention to the development and utilization of renewable new energy.However,most renewable energy sources are greatly restricted by the environment,and the output power has obvious random-ness and fluctuation.Energy storage elements are capable of buffering power fluctuations and are widely considered to be an effective way to solve the output power fluctuations of renew-able energy sources.Compared with a limited single energy storage,hybrid energy storage technology can fully take advantage of the advantages of different energy storage,and can also extend the service life of energy storage components.In this paper,a hybrid energy storage system combining storage batteries and supercapacitors is taken as the main research object.The power distribution between the two types of energy storage elements and the restoration of the state of charge of the supercapacitors are studied.The work is as follows.Firstly,several existing energy storage components are connected to the microgrid.The equivalent circuit models are selected based on the charging and discharging characteristics of the battery and supercapacitors.The small signal mathematical model of the converter is es-tablished to provide a basis for the design of the control strategy.Secondly,in order to solve the problem of power distribution between energy storage elements with two different character-istics,this paper proposes a power division control strategy for hybrid energy storage systems based on an improved droop method,which allocates power fluctuations on the bus to super-capacitors at high and low frequencies.And battery,you can set the power fluctuation fre-quency division point by changing the size of the virtual impedance,without the need for the central controller and communication network to participate.Thirdly,based on the power di-vision strategy proposed above,a further optimization is made for a low-energy-density su-percapacitor.A supercapacitor with a virtual inductor and a virtual voltage source is designed to recover the state of charge(SoC).The strategy and the design criteria of related control pa-rameters are given.This strategy uses a virtual voltage source to recover the power of the super capacitor,and introduces a virtual inductor,which uses its "traffic-blocking" feature to limit the SoC recovery process to the low-frequency stage after the transient power fluctuation com-pensation is completed,achieving two processes.It is separated and can be switched from the SoC recovery state to the transient power fluctuation compensation state at any time,which improves the safety of the system.Thirdly,based on the power division strategy proposed above,a further optimization is made for a low-energy-density supercapacitor.A supercapac-itor with a virtual inductor and a virtual voltage source is designed to recover the state of charge(SoC).The strategy and the design criteria of related control parameters are given.This strategy uses a virtual voltage source to recover the power of the super capacitor,and introduces a vir-tual inductor,which uses its "traffic-blocking" feature to limit the SoC recovery process to the low-frequency stage after the transient power fluctuation compensation is completed,achieving two processes It is separated and can be switched from the SoC recovery state to the transient power fluctuation compensation state at any time,which improves the safety of the system.Fourth,in order to meet the energy storage needs of larger-scale microgrids,for hybrid energy storage systems containing multiple batteries or multiple supercapacitors,based on the strate-gies mentioned above,improved hybrid energy storage with multiple energy storages in par-allel is proposed.The system power division control strategy and super capacitor SoC recovery strategy,while completing the power frequency division between the battery and the super capacitor and the super capacitor SoC recovery,realize the shunting of the same type of energy storage in parallel according to the capacity ratio.In order to verify the proposed power allocation and supercapacitor SoC recovery strategy,a model including hybrid energy storage system and equivalent load was built in Matlab/Simulink,and the proposed strategy was simulated.The results verified the effectiveness of the above control strategy.