Research On Key Problems Of Flexible DC Grid Applied In Dalian Area

Electric energy has become an important energy to support social development.With the depletion of traditional petrochemical energy,electric energy is replacing traditional petrochemical energy.This has also led to a sharp increase in the demand for power energy in the current society.In order to ensure economic development and guarantee people's production and life.The power grid must be continuously expanded and strengthened to ensure the quality of power supply while providing power supply capacity.This paper mainly studies the application of flexible HVDC transmission in urban power grid construction.According to the specific situation of Dalian area,it discussed the key problems of flexible DC transmission and distribution construction.The research results of this paper have guiding significance for the construction of flexible HVDC transmission in urban power grid.On the basis of introducing the research background and significance of the subject,the key technologies of flexible DC transmission and distribution are analyzed.It studies the basic structure and working principle of flexible HVDC transmission system.It analyses the characteristics and advantages of flexible DC transmission and distribution.It studies the different topology and working principle of voltage converter and DC solid-state transformer.It discusses the operation mode and control logic of flexible HVDC transmission.Secondly,it analyses the basic situation of the current power system in Dalian.It counts the current load rate of 220 kV substation in Dalian and the transfer capacity of 66 kV tie-line.It focuses on the weak links of the current Dalian power grid.It analyses the future power balance in Dalian.It predicts the power gap of Dalian power grid in the next six years.Based on the analysis of basic electric power situation in Dalian area,it analyses the basic scheme of flexible DC power supply in Dalian area.Through analysis,it is determined that the flexible DC power supply capacity is 1000MW;the DC voltage level of flexible DC transmission and distribution is(+320kV);and the AC voltage level of flexible DC transmission and distribution is 220 kV.It focuses on the analysis of cable access schemes and related supporting access points.By comparing the land cable scheme with the submarine cable scheme,it finally decides to choose the submarine cable scheme,and determines the substation at the receiving end and the transmitting end.It hascompleted the research on the construction scheme of flexible DC transmission relay protection and converter station.It analyses the configuration of relay protection schemes for flexible HVDC transmission and the design of relay protection schemes for transmission and recipient terminals.It focuses on the construction scheme of the converter station.The modular construction scheme is adopted in the construction of converter station,which ensures its advancement and reduces the construction cost of converter station.In the monitoring scheme of converter station,the monitoring standard of intelligent station is used as a template to realize the monitoring of various operation parameters.