Studies Of The Impact On Voltage Stability After First UHVDC Linking On East China Power Grid

In order to meet the demand of electricity of east China district, the first±800kV ultra-high voltage direct current (UHVDC) transmission system project (Xiang Jiaba to Shang Hai) is already approved by National Development and Reform Commission. It is expected to be established and put into production in the twelveth five years plan. However, there is no±800kV UHVDC transmission system in use all over the world, so we lack of the actual operation experiences. Therefore, the research of the impact of the±800kV UHVDC transmission system on the power grid is carried out urgently. For evaluating the impact of UHVDC on the voltage stability of east China power grid, this paper is divided into two parts, the static voltage stability and transient voltage stability. The main work and contributions are listed as follows:(1) With the function modules of PSS/E, a solving program for finding the maximum loading point of a power system is implemented using PYTHON language on PSS/E platform. This program can take the active power limit of the balance points into consideration, set the generator active power output and the load growth model in random direction, by which the flexibility and practicability of PSS/E are enhanced when the loading margin has to be determined.(2) The reactive power compensation schemes are given at the aim of improving voltage stability margin. In order to analysis the voltage stability margin under contingencies, the fast selection method of the key branches is also proposed. This method can identify the key branches which will deteriorate the voltage stability under contingency from a large number of branches quickly and accurately. These methods and computer programs extend the function of PSS/E in the analysis of static voltage stability.(3) In the analysis of the transient voltage stability, a transient voltage stability model taking UHVDC into consideration is implemented after the analysis methods for transient voltage stability are reviewed. The simulation is conducted for transient voltage stability analysis of East China power grid under contingencies using time domain simulation method by which the conclusion of the impact of AC contingency on the performance of UHVDC are drawn.All of the above methods are tested on the data package of the planning power system of East China in 2012. The effectiveness of these methods is demonstrated. The results give a valuable reference for understanding the voltage stability of east china grid in 2012 and the impact of UHVDC on it.