Effectiveness analysis of evaluating continuous commutation failure with short circuit ratio

The continuous commutation failure (CCF) of a line-commuted converter (LCC) based high voltage direct current (HVDC) transmission system will lead to long-term power imbalance of AC systems, which seriously threatens the safe and stable operation of AC systems. At present, the short circuit ratio (SCR) is widely used to evaluate commutation failure recovery characteristics of HVDC systems. In order to verify the effectiveness of the SCR in evaluating the risk of the CCF, the factors influencing the accuracy of the SCR are studied based on a simplified single-infeed HVDC system model. The analysis results show that the accuracy of the SCR is seriously reduced if there are a large number of loads near the LCC.