The influence of commutation failures on the reliability of HVDC transmission systems

The commutation failure is a common fault in line-commutated converter (LCC) based high-voltage direct current (HVDC) transmission system. The commutation failure is modeled and its influence on reliability of HVDC transmission systems is studied in this paper. First, the commutation failure mechanism of LCC-HVDC transmission systems is analyzed. Then, the commutation failure criterion is presented based on the concept of commutation area. Moreover, a concise equivalent reliability model of the commutation failure is built. The corresponding evaluation method is proposed based on Monte Carlo simulation. Furthermore, the impacts of commutation failures on reliability are studied by introducing the reliability model into the F&D approach in HVDC reliability evaluation. Extensive studies are conducted on a CIGRE benchmark system, which validate the presented methods. The evaluation results show that the commutation failures influence the reliability of HVDC system obviously. After the consideration of commutation failures, the energy unavailability of the HVDC transmission system increases more than 9%.