Research On Multi-terminal Feed Modes And Operation Characteristics For UHVDC

The energy distribution and economic development in China is imbalance due to the fact that most of the massive clean energy bases and thermal power bases are scattered in northwestern and southwestern China while the electricity lord centers are concentrated in eastern and southern China.The UHVDC transmission system has the advantages in long distance and high-capacity power transmission ability,which gained fast development in recent years.As a result,the capacity of power transmission is getting increasingly bigger,which will cause a great impact on the receiving end power system,so it’s very necessary to adopt multiple distributed receiving ends to absorb power.This paper focused on addressing this issue from the aspect of grid structure by proposing a novel separating pole connection(SPC)mode for UHVDC integration,and the feasibility was verified by analyzing its static properties and dynamic behaviors.Firstly,taking off from the background and significance of this subject,this paper summarized the development and applications for UHVDC,meanwhile,the present reaearch on multi-terminal feed modes were concluded.Secondly,the paper introduced the configuration concept of SPC and studied the overall control stategies for SPC.The third chapter presented the definition of short circuit ratio for separating pole connection mode(SPCSCR),and the abilities of power transmission related with SPCSCRs under different connection modes were analyzed.Furthwemore,the equavilent model for different kinds of multi-terminal feed modes was discribed by characteristic equations.According to the actual needs of Henan Grid,simulation model for UHVDC SPC was built based on PSCAD/EMTDC,and the dynamic behavior of SPC mode was studied through fault and recovery analysis,which showed the SPC mode can achieve fault isolation between two poles.The series multi-terminal feed mode was also built to proceed fault analysis and provided contrast for SPC,and the results validated the advantages of SPC mode,which has great superiority in adressing the issue of voltage stability for UHVDC and promoting coordinated development for AC and DC power networks.