说明：  高压直流输电（HVDC），是利用稳定的直流电具有无感抗，容抗也不起作用，无同步问题等优点而采用的大功率远距离直流输电。输电过程为直流。
(High voltage direct current (HVDC) transmission is the use of stable DC has no inductance, Rongkang doesn t work, without synchronization, etc. the high power long-distance HVDC transmission. The transmission process is direct current.)