Influence of VSC-HVDC on short-circuit current of AC system

Abstract

After the AC system is short-circuited, voltage source converter-high voltage direct current (VSC-HVDC) can be equivalent to a current source with a certain amplitude and phase. In this paper, based on the equivalent model of VSC-HVDC when the receiving end grid fault occurs, the factors affecting the phase and amplitude of equivalent current source of VSC-HVDC are analyzed respectively. Studies show that the phase of the equivalent current source is mainly affected by the type of fault, and the amplitude is mainly affected by the control method, the amplitude limiter and the electrical distance. Because of the combination of different situations, the influence on the AC system short-circuit current is bceorning more complicated.The research results show that for AC side three-phase short-circuit fault, the influence of VSC-HVDC on short-circuit current can be divided into four situations, which contain zero feed in, limited amplitude of active control link, limited amplitude of reactive power control link and reference value of reactive power control link. The simulation results based on PSCAD software verify the relevant analysis.

Keywords

• modular multilevel converter
• voltage source converter-high voltage direct current (vsc-hvdc)
• control strategy
• three phase short circuit
• influencing factors
• fault analysis