Full metal pole loops; complete monopolar ground return line running

With the growth of the national economy , energy and the distribution of the load center features make the ultra- long-range , large -capacity power transmission become inevitable , the use of ± 800kV HVDC transmission technology, not only conducive to  Valve manifolds  transmission of scale , saving a lot of resources, transmission corridor You can also increase the level of security and stability of the grid . HVDC (UHVDC) project generally use two 12-pulse valve means connected in series to form a pole, this structure makes the entire DC system has great flexibility , based HVDC (UHVDC) of a pole 2 the characteristics of a valve in series , the DC system operation modes: full bipolar operation ; complete monopole metal loops ;  Stainless steel needle valve  ground return line run ; 3/ 4 bipolar ( a very full 1/ 2 is extremely uneven ) run ; 1/ 2 bipolar operation ; 1/ 2 pole metal loop run ; 1/ 2 monopolar ground loop operation. For the above characteristics, HVDC project must meet the following requirements: ① tandem two manifolds can be run  Stainless steel needle valve  ; ② stable operation of the two valves in series should be essential to maintain symmetry operation ; ③ When either a valve operation, through relevant the control inputs of two manifolds, AC / DC system should not produce too much disturbance ;