Prevention control method of subsequent commutation failure for LCC-HVDC under grid fault

摘要

Commutation failure (CF) can easily occur in line-commutated converter-based high-voltage direct current (LCC-HVDC), which causes the renewable energy tripping off from grid and cascading failures. Given that the first CF (FCF) can be hardly avoided, suppressing subsequent CF (SCF) becomes the key to ensuring the safe operation of large-scale AC/DC hybrid power grids. The advanced control through predicting CF is the most effective method to suppress CF or reduce the bad influence of CF. However, the existing prevention control is implemented according to the FCF prediction. The effects are limited. The unreliable trigger of prevention control can even become the driving force for SCF. Therefore, a new idea of SCF prevention control is proposed. The impact of the firing angle on the reactive power characteristics of the inverter station are demonstrated. The calculation methods of SCF threshold voltage considering the controllers response of inverter station is derived and the firing angle adjustment considering the fault severity are proposed. Thus, the SCF prevention control (SCFPREV) realized by the scientific SCF prediction and accurate adjustment of firing angle is proposed. The effectiveness of SCFPREV is verified through the CIGRE Benchmark HVDC model, and the simulation results demonstrate that the commutation voltage recovery characteristics can be remarkably improved, and the SCF can be avoided by SCFPREV.