中文摘要：

现代高压直流输电系统一般采用双极双桥的单12脉或双12脉接线方式。从接线方式、运行容量状态和等效模型三个方面对这两种接线方式进行了对比研究，并应用马尔科夫（Markov）过程和频率与持续时间法（FD法）对它们进行了可靠性量化评估分析，计算结果表明双12脉接线相对单12脉接线在系统运行效率和可靠性水平上有较大提高。同时进行了元件参数对系统可靠性影响的灵敏度分析研究，透过灵敏度指标可以深刻揭示影响系统可靠性的主要因素，为有效发现系统薄弱环节和提高系统的运行管理水平提供重要的参考信息和决策依据。

英文摘要：

Modem HVDC transmission systems generally use 12-pulse valve groups or 2xl2-pulse valve groups per pole as a main circuit designing structure. In this paper, the two configurations are compared with each other by the main circuits, operating capacity states and equivalent models, and then their reliability indices are calculated using the theory of Markov process and FD method based on the same reliability parameter for each equipment. The results of calculation indicate that the HVDC system used 2xl2-pulse valve group has dramatic improvement on the operation efficiency of system and level of reliability compared with the one used 12-pulse valve group. Moreover, the sensitivity indices of reliability with respect to equipment parameters are also analyzed in this paper. The sensitivity indices open out the main factors that affect the reliability of system. The analysis and conclusions in the paper can be used as a reference to find the weak reliability links of the HVDC system and improve operation and management of HVDC system.