figure 6. The transmission line on the red land of Yunnan. (Used with permission from CSG.). figure 7. A night view of Guangzhou. (Used with permission from CSG.) back-to-back interconnection. at that time, power in eastern and western Guangdong will supply power themselves respectively; the problem of high short circuit currents is also solved. july/august 2016 Application of VSC-HVdc Commutation of a conventional hVdc line-commutated converter depends on the ac power grid, and commutation failure will occur when failures at nearby ac power grid ieee power & energy magazine 77