Zeng Nanchao

Study of AC/DC coupling for Three Gorges to Changzhou HVDC system

The new solution for calculation AC/DC coupling issue in the same ROW was proposed and validated by EMTDC. The brief curve of I/sub ac-in-dc/ versus D/sub ac-to-dc/ for per coupling length of AC line was obtained by the proposed method (I/sub ac-in-dc/ and D/sub ac-to-dc/ here mean the fundamental frequency current in DC line and the distance between AC and DC lines respectively). Based on this curve, the value of I/sub ac-in-dc/ can be easily estimated for different AC/DC coupling schemes especially in the cases of the AC and the DC lines being built simultaneously, or the DC line being built earlier than the AC line. The relationship between the I/sub ac-in-dc/ and the DC bias current in converter transformer valve side with the actual HVDC control system is also investigated.

Analysis of main technical problems for XS and JS ±800kV UHVDC projects system test

The main technical problems of Xiangjiaba to Shanghai (abbr. XS) and Jinping to Sunan (abbr. JS) 800kV UHVDC transmission projects system test were analyzed in this paper. Based on the system stability calculation results, 46 kinds of main circuit connection modes and referring to 500kV HVDC system commissioning test experiences, the system test program and test plan were prepared, which was divided into four parts that were single converter system test instructions, monopole system test instructions, bipolar system test and de-icing mode system test instructions. Duo to rectifier side system was weak in the initial operation stage, AC bus voltage control and reactive power control had been solved. The main technical problems in XS and JS UHVDC project system test were analyzed in detail, which included VBE and control interface function verification, island mode test and de-icing connection mode test. These technical problems had been solved during system commissioning test, which guaranteed to complete XS and JS UHVDC project system commissioning test and put into operation in time.