中文摘要：

高压直流三极输电技术是一种适用于交流输电线路增容改造的新技术。介绍了它的主电路结构,对其中用于实现三极输电方式的关键部分——极3的2种接线方式（即换流阀直接反并联和换流阀中的晶闸管反并联）进行了比较,得出后者更适合应用于实际工程建设中的结论。并通过数学理论推导,分析了高压直流三极输电系统所采用的电流调制控制的原理。比较了将交流输电线路转换为高压直流双极和三极输电系统后的输电容量、冗余度、过载能力和经济性,得出后者优于前者的结论。最后,根据我国现有国情,将高压直流三极输电技术与其他的增容改造方法进行了比较,并对其在我国的应用前景进行了初步的探讨。

英文摘要：

Tripole high voltage direct current （HVDC） power transmission is a new technology suitable for capacity-increase of existing AC power transmission lines. The structure of main circuit of tripole HVDC power transmission is presented, and two connection modes of the third pole, namely anti-parallel valves and anti-parallel thyristors within same valve, which are the key parts in the implementation of tripole HVDC power transmission, are compared, and research results show that the latter is more suitable to be applied in practical engineering projects. By means of theoretical derivation, the principle of current modulation adopted in tripole HVDC power transmission system is analyzed. After turning AC transmission lines into bipolar and tripolar HVDC power transmission lines respectively, the transmission capacity, internal redundancy, overload capacity and economy are compared and the conclusion is the latter is better than the former. Finally, according to current national conditions in China, the technology of tripole HVDC power transmission is compared with other approaches for capacity-increase of existing AC power transmission lines, and its application prospect in China is preliminarily discussed.