| The Voltage Source Converter based High Voltage Derect Current (VSC-HVDC) transmission system is a new kind of electrical energy transmission system,which can control active and reactive power separately immedietely, supply power to non-source system and will not fail in phase commutation, at the same time, its ability to supply emergency active and reactive power support can enhance the stability of power system.The problem of static voltage stabily of AC/HVDC system based on PCC technology has been discovered for a long time, however, the corresponding problem of AC/HVDC system based on VSC converter is merely discovered. This issue is to research the static voltage stabily of AC/VSC-HVDC system.The working principle and the commutation process is analyzed in detail and the mathematical model of VSC is established, on this basis, the control equation of VSC-HVDC and statistic mathematical model of AC/VSC-HVDC system is established.A new method of analyzing static voltage stability of AC/VSC-HVDC using continuation method and alternative algorithm is proposed, which can take factors such as the upper and lower limits of generator output and change of operation mode.According to the real circumstance that two HVDC lines supply power to one system at the same time, which eventually form a Double-Infeed HVDC (DIDC)system, a method of analyzing DIDC system based on VSC converter is discovered and a practical calculation example is given to illustrate the influence of VSC, VSC control mode and VSC-HVDC transmission system to the static voltage stability of DIDC system.
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