| The development of power electronics technology drives the development of high voltage direct current transmission (HVDC) technology. In the coming era of Big Power Grid Era, HVDC technology reflects its advantages. Light high voltage direct current transmission (Flexible HVDC) technology develops on the basis of full control type semiconductor material development. Flexible HVDC keeps the full control type semiconductor material Insulated-Gate Bipolar Transistor (IGBT) voltage source converter (VSC) remaining dominant relatives to the traditional HVDC half control type semiconductor material thyristor.Flexible HVDC is a new-type HVDC based on voltage sourced converters (VSC) Technology. As using IGBT in VSC, the current will be cut off easily; also the pulse-width-modulation (PWM) technology can be used for passive inversion. The VSC technology has many more superiorities, such as small cubage, strong function, decreasing filter device and simplifying conversation structure. For these reasons, this technology is named flexible HVDC. Besides the superiorities of traditional HVDC, flexible HVDC can be used for supplying to the isolated and distanced load and connecting separated sources. Also, the control method of flexible HVDC is much more flexible and multivariate. The voltage drop in the transmission line will be decreased and the voltage quality will be increased by using flexible HVDC technology.This paper describes the basic structure of flexible HVDC and principle, technical features, such as content development and applications; summarized flexible HVDC control strategy; given flexible mathematical model of steady-state DC power transmission; established the transmission system model using MATLAB/SIMULINK software, analyzed the characteristics of the system in normal operation and three-phase short circuit, the simulation results demonstrate the excellent flexible HVDC operational stability. At last, the application of flexible HVDC was prospected. |
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