Equivalence and Transient Characteristics of Flexible DC Converter after AC Fault

Flexible DC transmission systems can renewable energy consumption and improve power supply reliability. However, the control response and topology of flexible DC converter leads to a different fault output from conventional synchronous generator. Based on topology and control strategy, the controller response of flexible DC converter after AC fault is analyzed, and the equivalence of converter is proposed from the view of sequence component. The results show that positive-sequence equivalence is a current source, and its output satisfies the second order non-flush differential equation and is over-damped. Negative-sequence equivalence is an open circuit under suppression strategy. Zero-sequence equivalence is determined by grounding scheme of transformer windings and is not affected by control strategy.