| As a kind of renewable energy with huge reserves,wind energy has been paid more and more attention by all countries in the world,and the installed capacity has been growing rapidly.However,the output power of wind power generation is fluctuant,which will affect the stability of power system or microgrid operation if directly connected to grid or consumed locally by microgrid,which seriously restricts the development of wind power generation technology and the utilization of wind energy.A hybrid energy storage system with a certain capacity can effectively alleviate the fluctuation of wind power,so as to solve a series of problems caused by wind power grid connection and micro grid local consumption.In this paper,a hierarchical control strategy of power distribution optimization for hybrid energy storage system is proposed,which can reduce the charge and discharge times of battery,prolong the life of energy storage system and reduce the operation cost of the system while stabilizing the power fluctuation.The main contents of this paper are as follows:Firstly,the structure of wind power micro grid with hybrid energy storage system is analyzed,and the working principle of wind power generation,lead-acid battery and super capacitor is described.The charging and discharging characteristics of the two systems are analyzed by establishing simulation model in Matlab/Simulink.The analysis results show that there are complementary characteristics between the lead-acid battery and the supercapacitor,which verify the feasibility of the hybrid energy storage system composed of the two,and lay a theoretical foundation for the later study of the power distribution of hybrid energy storage.Secondly,the structure of the hybrid energy storage system is studied.Aiming at the problem of the overall charge and discharge capacity of the hybrid energy storage system and the internal power distribution of the energy storage system during the operation of microgrid,this paper proposes a hierarchical optimization strategy of power distribution based on the rotation charge and discharge.In the upper power distribution,the relationship between the power fluctuation of the microgrid system and the SOC of the hybrid energy storage system is mainly considered,and the charging and discharging instructions of the whole energy storage system are dynamically adjusted by fuzzy control to prevent the over charging and over discharging of the energy storage system;the power distribution in the lower layer is mainly used to absorb the power fluctuation of wind power,mainly including the power distribution between different media and the power distribution of the monomer in the same media.When the power demand to maintain the stability of the system is distributed among different energy storage media,the coefficient of low-pass filter is modified in real time according to the supercapacitor SOC,and the utilization potential of supercapacitor is firstly exploited to reduce the times of battery output;the power distribution in the same medium mainly considers the influence of the power distribution of the monomer in the energy storage medium on the energy storage system,and proposes the control strategy of the charge and discharge rotation considering the charge state and the charge and discharge switching times of the monomer lead-acid battery,which effectively reduces the overall charge and discharge switching times of the battery group and improves the life of the battery group.Thirdly,the hardware circuit and software control flow of the system are designed and implemented,and the feasibility of power allocation layered optimization strategy is verified by the experimental platform.The experimental results show that,compared with the traditional low-pass filter control strategy,the hierarchical optimization strategy of power distribution can not only effectively reduce the fluctuation of wind power grid connected power,but also reduce the switching times of battery charging and discharging,extend the life of energy storage system and reduce the operation cost. |
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