Power Distributed Strategy Of DC Microgrids With Hybrid Energy Storage System

Renewable Energy Source(RES)generation is an important part of microgrid,which is of great significance to alleviate energy crisis and achieve sustainable development.However,the distributed power supply represented by Solar Photovoltaic(PV)has obvious disadvantages such as poor steady-state performance,weak continuity and low energy density,so energy storage(ES)must be added to reduce these negative effects and maximize the benefits.The battery and supercapacitor(SC)combination of new type of Hybrid Energy Storage System(HESS)and applied to dc micro grid System,has great technical and economic advantages,with the corresponding control strategy and Energy management scheme,to give full play to the super capacitor power density and the characteristics of high Energy density battery,prolong the service life of battery,improve power quality,improve the running efficiency of the whole System,and reduces the total investment cost of the System.Therefore,this paper makes a preliminary study on the power distribution strategy of dc microgrid with hybrid energy storage system,and makes a contribution to the application and development of dc microgrid.Firstly,it introduces the background and significance of this research,analyzes the current research status of hybrid energy storage system at home and abroad,and models the photovoltaic cells,DC converters and energy storage device based on the the system structure of typical DC microgrids.A disturbance observation method based on variable step sizes is proposed to realize the MPPT control of photovoltaic cells,and is verified by simulation in Matlab/Simulink.Then a distributed secondary compensation control strategy is proposed based on the traditional droop control method.The secondary control method is used to compensate the dc bus voltage drop caused by the traditional droop control.By adjusting the droop coefficient,the high precision of load power distribution is achieved,and its effectiveness and reliability are verified by simulation.Finally,a multi-group hybrid energy storage control strategy for dc microgrid is proposed,which is used to distribute unbalanced power in the autonomous system and adjust the dc bus voltage.By setting an appropriate cut-off frequency,the frequency division distribution of power between the SC and the accumulator is realized,and the consistency algorithm is adopted to make the variation of bus voltage,the SOC of the SC and the accumulator become consistent for each hybrid energy storage unit,and its effectiveness and reliability are verified by simulation analysis.