Coordinated Control Method of Multi-infeed DC System for Commutation Failure Prevention

Commutation failure predictive control (CFPREV) is widely used to suppress commutation failure (CF) in practical multi-feed DC systems (MIDC). The current research is mainly limited to the improvement of CF suppression strategy for single-loop DC system without considering the influence of this DC controller on other DC systems. The CFPREV not only reduces the risk of CF, but also increases the reactive power consumption of the local DC system, which will affect the normal commutation process of other DC systems. Therefore, a coordinated control method of MIDC for CFPREV is proposed in this paper. First, the reactive power coupling factor is proposed to qualitatively determine the coupling degree between each DC system, and then multiplied by the margin to guide the adaptive output of CFPREV. Reduce the CFPREV output when the margin of other DC systems is low to avoid the CF of other DC systems. Based on the CIGRE HVDC standard test model in the electromagnetic transient simulation platform PSCAD/EMTDC, the three-feed DC system was built as the simulation model, and the effectiveness of the proposed control method to suppress CF was verified.