| In 2020,new infrastructure,including data centers,electric vehicles,charging stations and trams,has higher requirements for power quality,power supply safety,reliability,efficiency and power of DC power supply.Due to the high power loss of copper cable transmission,slow response speed of battery energy storage,poor reliability of power electronic current limiting and other defects,conventional electrical device technology has been unable to meet the high power supply quality and high energy efficiency requirements of DC microgrid.Benefiting from the advantages of the near-zero loss and high current density self-triggered current limiting of superconductors,the superconducting DC microgrid with superconducting energy storage technology and superconducting current limiting technology is expected to meet the higher quality of power supply and high energy efficiency requirements of the new infrastructure for DC microgrid in 2020.This paper introduces the dc chopper superconducting energy storage battery energy storage(SMES)dc chopper(BES)composite superconducting energy storage system(HESS)superconducting fault current limiter(SFLC)principle and control strategy from the superconducting dc micro grid structure analysis,build simulation model respectively to study the structure of radial ring structure of the superconducting dc micro power grid in the power supply voltage fluctuations load power cable circuit fault and load under the condition of short circuit fault compensation results.The main research contents are as follows:1.The simulation model of the composite superconducting energy storage DC microgrid is built.The simulation shows that the composite superconducting energy storage device can compensate or suppress the rated load voltage of 87.5% or 112%instantaneously to the rated voltage,which proves that the composite superconducting energy storage device can improve the power supply quality of the superconducting DC microgrid.2.The simulation model of superconducting current limiting DC microgrid is built.When a short circuit fault occurs in the DC microgrid,the SFCL limits the maximum impulse current from 1400 A to 455 A and improve the power reliability of the DC microgrid.Compared with the traditional fault circuit breaker,the superconducting current limiter can limit the current through its own characteristics and does not rely on external control,so it has higher reliability and achieves the essential requirements of safety.3.Based on the model of superconducting DC microgrid structure,the influence of microgrid structure on the power supply reliability of DC microgrid is analyzed from the perspective of safety essentialization.Loop network structure reduces the possibility of regional power outage from the structure.When a cable is out of circuit,the DC power supply can be supplied from another cable to the branch,which increases the power supply reliability of the DC microgrid.4.Considering the high economic cost of superconducting devices,a multi-network cascading superconducting DC microgrid model(IDC-DVR)is built in this paper.In this system,a SMES system is used to compensate the voltage fluctuations of multiple radiative DC microgrids.The IDV-DVR scheme can stabilize the voltage when the voltage fluctuation occurs in a single DC microgrid.When multiple lines fail at the same time,the high-priority lines can be compensated according to the set line priority order,which saves the economic cost while maintaining the stable operation of the DC microgrid.5.The experimental platform of superconducting DC microgrid was built,and the parallel composite superconducting energy storage experiment and series superconducting energy storage experiment were carried out.According to the experimental results,the parallel type HESS device can quickly stabilize the load voltage at the rated value of 24 V,and the series type SMES can stabilize the load voltage and current at 30V/20 A normal working state.It effectively verifies the high-quality power supply characteristics and high reliability of the composite superconducting energy storage and current limiting DC microgrid,which establishes the technical basis for the high quality power supply and safe operation of the DC microgrid. |
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