Commutation failure suppression method considering chain reaction in multi-infeed LCC-HVDC systems

In multi-infeed HVDC (MIDC) systems, in which HVDC means high-voltage direct current, the complex in-teractions between AC/DC systems and different line-commutated converter-based high-voltage direct current (LCC-HVDC) produces a special commutation failure (CF) chain reaction phenomenon. The existing methods are mostly aimed at the transient process of the single LCC-HVDC, which reduces the CF suppression effect but may become the driving force of the CF chain reaction. In view of this situation, this study proposes a new CF sup-pression method based on the CF chain reaction security region. First, the CF chain reaction process of multiple LCC-HVDC systems is analyzed, and the boundary of the CF chain reaction is characterized. Second, by estab-lishing the CF chain reaction security region, the control method of the coordinating DC current and firing advance angle to suppress the CF chain reaction is proposed. Simulation results show that the proposed method avoids the subsequent CF of the LCC-HVDC while maximizing the suppression effect of the successive CF in the adjacent LCC-HVDC, thereby blocking the cascading reaction of CF that usually caused large-scale security problems.