142
Z. Lu and G. Zhu
It’s important for UHV AC/DC parallel grids to match the distribution of energy
resources in China. Construction of robust UHV grids should be accelerated by using
UHV DC, via UHV AC connection, to transmit clean energy across regions and over
long distances. Efforts should be made to reverse the precedence of DC over AC
and ensure appropriate balance, so that the size of DC or AC is commensurate with
intensity. Currently, China’s UHV AC/DC parallel grids have taken shape, yet new
problems resulting from constant changes in operation stand as a test to the endurance
of grids (Wen et al. 2012).
4.3.2 Flexible DC Transmission Technology
Despite the distinct strength of UHV DC transmission technology in long-distance
transmission, it can only be applied to point-to-point transmission of energy without
any drop point in the middle, which is not conducive to the optimal allocation of
Fig. 4.20 Comparison of AC/DC transmission construction costs
Table 4.10 Reliability comparison of AC and DC networks
Name
AC
DC
Single-circuit Double-circuit Monopolar Bipolar
Line (times/100 km/year)
0.299
0.054
0.126
0.055
Two-end conversion stations (times/year) 0.56
0.12
4.8
0.2