Application Of Phase-shifting Technology In UHV Half-wavelength AC Transmission System

It is of urgently to explore the new ultra-long distance large capacity transmission technology,which can effectively solve the global energy resource distribution,market demand severe imbalance,and the reverse distribution problem of China's energy resources and load demand.As a very competitive power transmission scheme,the transmission scheme of half-wavelength is one of the most important ways to transmit power.Although the half-wavelength AC transmission technology has many advantages,there are still many problems to be studied.This paper introduces the development status,characteristic advantages and key technical problems of half-wavelength AC transmission,and it is focused on the application of phase shift technology in the ultra high voltage and half-wavelength AC transmission system.Firstly,the principle is used that Phase shift transformer can change the voltage amplitude and phase angle of the end of the transmission line.A voltage compensation method based on phase shift in half-wave transmission line is proposed,the voltage compensation of different transmission lines is validated by PSCAD/EMTDC.The simulation results prove the effectiveness and feasibility of phase-shifting for voltage compensation of power transmission lines.Based on the principle that Phase shift transformer can regulate the flow of transmission lines,it is analyzed that the single loop line flow controled by the shift phase transformer in the half-wave double-loop transmission line,which exits a running fault line.Secondly,based on the principle that the equivalent impedance of phase shift can be changed by adjusting the phase shift angle,the impedance matching method of a half-wave transmission system is proposed.When the system is disturbed,the equivalent impedance of the equivalent change system is adjusted to make it close to the characteristic impedance.Thus the transmission efficiency of transmission line is improved.Finally,the characteristics of point-to-grid connection in half-wavelength transmission system are analyzed.The principle of phase-shifting voltage amplitude and phase angle is adopted which realizes the flexible grid connection of half-wave transmission lines.The control strategy of phase-shifting is proposed and the model is simulated in PSCAD/EMTDC.