Research On Grid-connection Characteristics And Flexible Grid-connection Technology Of Half-wavelength AC Transmission Lines

In recent years,the power industry has been developing continuously,but the imbalance between resource distribution and energy demand in China has become increasingly prominent.Therefore,it is urgent to find a transmission mode suitable for large capacity and long distance.Half-wavelength AC transmission has been widely concerned for its advantages of large capacity,long distance and high efficiency.Many scholars have studied the characteristics and feasibility of half-wavelength transmission lines from different aspects such as characteristics of transient and steady state and over-voltage problems.In this paper,a series of problems of grid-connection on half-wavelength transmission line are discussed.In order to study the grid-connection characteristics of half-wavelength transmission line,this paper considers the distribution characteristics of line parameters,builds an accurate equivalent ? model of half-wavelength line based on the long-distance transmission line equation and two-port network theory,analyzes the differences of grid-connection characteristics between half-wavelength line and conventional lines.The grid-connection simulation models are built in MATLAB.Simulation considers the grid-connection characteristics under different conditions,and compares half-wavelength line with conventional lines.The simulation results show the advantages of the grid-connection characteristics of half-wavelength line.This paper also considers the hidden danger caused by large grid-connection deviation for half-wavelength transmission systems,difficulty to simultaneous adjustment of grid-connection parameters at both ends of half-wavelength line due to its long distance,variety of grid-connection structures and grid conditions for half-wavelength systems,this paper uses the flexible device for grid-connection adjustment.Then,the equivalent circuit of half-wavelength transmission system connected with flexible device is analyzed,and also the theoretical feasibility of the flexible grid-connection device is studied.The simulation results in MATLAB/Simulink show that the flexible grid-connection device is suitable for multi-structure and multi-conditions of half-wavelength transmission systems,also it can generally improve the grid-connection characteristics.The results can provide support for multi-structure grid-connection control of half-wavelength transmission projects in the future.