Corrections of original CFPREV control in LCC-HVDC links and analysis of its inherent plateau effect

The most effective approach to suppressing the first commutation failure (CF) of the LCC-HVDC link at fault inception is to advance firings of the inverter, and the commutation failure prevention (CFPREV) control is the most commonly used method in practical engineering. However, it is discovered in this study that there exist a few serious defects in its original scheme, and thus targeted vital corrections were made. Furthermore, an interesting phenomenon termed the plateau effect, which states that an excessive advancement of firings will contrarily and inevitably lead to more commutation failures, is also revealed and analyzed. It turns out that the inherent commutation dents of the Graetz bridge should be primarily responsible, which bridges the knowledge gap and further enhances the cognition of the limitation of CFPREV control, and it may also be conducive to the design of related control parameters. Simulation results then validate the necessity of these presented corrections and confirm the existence of the plateau effect.