Research On Overvoltage Simulation And Equipment Insulation Coordination Of DC Distribution Network

Compared with AC distribution network,DC distribution network has the advantages of large transmission capacity,high power quality,low commutation loss,no system synchronization stability problems and support for distributed generation access.Because of the economy and reliability of direct current distribution,the construction of DC distribution network has been paid more and more attention.And overvoltage and insulation coordination as an important part of the construction of the project,there are many problems to be solved.Its purpose is to rationalize the insulation level of DC power distribution equipment.We need to consider at relevant equipment cost,maintenance cost and loss of insulation failure,and obtain the related strategy of insulation protection coordination for improving the reliability and economy of DC equipment operation.At present,arresters are widely used for insulation protection of equipment overvoltage.The locations and parameters of arresters directly affect the insulation level of equipment,which is related to the cost of the whole DC distribution project.Therefore,it's very necessary to carry out the research on the overvoltage and insulation coordination of the DC distribution network.This paper has done a further research of the structural characteristics of ± 10kV Modular Multilevel Converter(MMC)flexible DC distribution system and the control modes of MMC converter station.The electromagnetic transient simulation model of DC distribution network is established by PSCAD/EMTDC software,and all kinds of possible faults on the AC or DC sides of the system are also studied.On the basis,the maximum overvoltage level at each key node of the converter station is obtained through simulation analysis.Meanwhile,based on the experience of insulation coordination of flexible DC converter station,and according to the basic principles of arrester arrangement,two protection schemes for arresters suitable for two-end DC distribution network are put forward.Finally,the insulation level of the related equipment is determined considering the insulation margin.In this thesis,the overvoltage and insulation coordination of two-end DC distribution network based on MMC are studied.The relevant results and methods of the research can provide the basis for the design of the subsequent DC distribution engineering.