Impact On Dynamic Stability Studies Of UHVDC Link On East China AC Power Grid

The Ultra-high voltage direct current (UHVDC) transmission has its obvious superiority in long-distance large power transmission domain. The UHVDC line from Xiangjiabato East China power grid will be put into operation at the beginning of the twelfth five-year-plan of China. Then there will be six HVDC lines connected to the East China power grid including this UHVDC line and all DC lines total power injections amounts to 19.6GW. It makes the East China power grid become multi-HVDC injection sink power system. The various UHVDC operation modes will bring influence on the statbility of East China power grid. This paper is mainly analyzed interaction on the stability between UHVDC and East China power grid AC system with big disturbance from the system operation viewpoint with the PSS/E tool. The primary content covers:(1) According to real UHVDC design parameters, its quasi-steady model is established including converter model and the control policies for electromechanical transient simulation analysis. PSS/E CDC6T model is explained and introduced into this research.(2) The interaction mechanism between HVDC and AC sink system has been presented. The effects of AC fault on UHVDC system has been analyzed with the planning data package of East China power grid in 2012. The 500kV and 220kV N-1, N-2 faults and UHVDC block faults are simulated in the text. The impact of UHVDC single-pole and bi-pole block on East China power grid AC sink system stability are simulated and analyzed with East China power grid planning data platform in 2012.(3) To illustrate the conditions of UHVDC block, a typical small simulation system with consideration of UHVDC effect has been designed. And some different factors which cause to DC block phenomenon are preceded. Lastly, sensitivity factors are simulated in the test system.(4) The simulation results indicate that the system power disturbance will be brought if reactive power compensation equipments can’t switch off under UHVDC single-pole and bi-pole block conditions. If these reactive power compensation equipments can switch off timely, the AC power system will maintain power angle and voltage stability after DC block faults. While, the UHVDC faults will not lead to power angle instability or voltage instability of the AC system. It shows simultaneously that HVDC systems are not likely induce DC block fault under any N-1 or N-2 AC system faults. While, these AC system faults could lead to some DC lines’commutation failure.All these research process and results are benifical to system security operation with connection of UHVDC and have great potienal application value.