Research On Operation Control Of DC Microgrid Based On Hybrid Energy Storage

Climate warming,environmental pollution and the aggravation of energy crisis all promote the development of renewable and clean energy technology.However,the output power of new energy power generation is easily affected by the environment change of local area,and It is not stable enough while working and not suitable for direct integration into the grid.DC microgrid integrates distributed power supply,energy storage device,and load.It has obvious advantages in such fields as construction cost,controlling difficulty and power utilization.The wind solar energy storage DC microgrid is the research object of thesis.This thesis studies the scheme of improving the power distribution of hybrid energy storage system while implementing the frequency division control scheme,and formulates the scientific and reasonable scheme of controlling the DC microgrid under different conditions.The main contents of this thesis are as follows:The overall structure of DC microgrid was introduced.The distributed generation unit of DC microgrid was analyzed to study the mathematical modeling and operation control.In light of the problem of power distribution between super capacitor and battery in hybrid energy storage system of DC microgrid and the disadvantage of low energy density of super capacitor and easy to reach overcharge or overdischarge state,a power control scheme according to the super capacitor SOC(Stage of Charge)was designed on the basis of the establishment of equivalent circuit model.After the SOC and droop control strategy of battery were comprehensively considered in different hybrid energy storage systems,an optimized adaptive droop strategy was developed,which can adjust the charging and discharging power of different hybrid energy storage systems according to the state of charge of battery,so that the state of charge of battery in multiple hybrid energy storage subsystems gradually tends to be consistent in the operation process.Finally,the DC microgrid was divided into various working conditions by making full use of the SOC of energy storage equipment.On the basis of mastering the operation conditions of different converters,the power of the DC microgrid system was controlled and distributed and the operation power of different regions was adjusted.all of these measures help to realize the reasonable distribution of the net power of the system among the subsystems.