| The low voltage DC microgrid is mainly composed by wind and light power,energy storage units(ESU),electric vehicles,AC or DC loads,and control units.It can effectively increase the penetration rate of new energy and is important part of the future smart distribution system.However,the intermittent volatility of the distributed power supply in the low-voltage DC microgrid and the irregular fluctuation characteristics of the load has brought major challenges to the safety and stable operation of the system.It is a great significance to study how to use energy storage system to achieve fluctuating power balancing and voltage support of DC power networks.This paper pay attention on the key control technologies of storage system research for low-voltage DC microgrid,mainly including energy balance control technology of multi-energy storage system and DC microgrid voltage control strategies.Firstly,this paper studies and designs a power control way based on SOC(state of charge)of multi-energy storage equalization control.Using the droop control technology,the reference voltage values of the converters,which connect to each energy storage unit,can adjust dynamically.In the result,the energy storage unit can adjust corresponding output according to its own state of charge.In the meantime,the balanced control of ESU and the dynamic distribution of system fluctuating power can be realized in the low-voltage DC microgrid to avoiding over-charge or over-discharge of a certain energy storage unit and extend the life of the energy storage unit.At the same time,compared with our method and the traditional control schemes,simulation results verify the feasibility and effectiveness of the balanced control of the multi-energy storage system mentioned in this paper.Secondly,this paper studies and designs a system control method that combines the energy storage unit and the distributed power generation unit in response to the low voltage ride through(LVRT)problem that may occur in the low-voltage DC microgrid under grid-connected operation.During the period of LVRT,the energy storage system controls the DC bus voltage stability,balances the system energy,and improves the reliability and stability of the low-voltage DC microgrid system when connected to the grid.Based on MATLAB/Simulink simulation,the relevant simulation is executed.Finally,the structure of the microgrid experiment platform of the school is introduced,and the experimental verification and analysis of energy storage control related experiments are completed based on the school experiment platform.The research work of this paper will have theoretical guiding significance and practical application value to the power control technology of energy storage system for DC microgrid. |
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