The Robustness Degree Assessment Method Of Distribution Grid Structure

On the background of the construction of strong smart grid, power distribution network as the terminal part of power system, directly face the electricity user. And it receive electricity from the grid or regions, by assigning or distribution facilities in situ according to voltage level assigned to different voltage grade of all types of users. It is very closely related to the interests of these users. According to statistics, more than80%of users’power failure is caused by the distribution part of the power system. As early distribution network construction in our country is long-term backward, unreasonable planning and much thought to the consideration of economy, make the current distribution network grid not strong enough. Scientific and reasonable distribution network frame is the basis of providing customers with high quality power and it also necessary for power network safety and economic operation. The robustness degree of the overall grid is affected by the robustness degree of the distribution network. Therefore, the robustness degree assessment of distribution network structure becomes the imminent task.Firstly, in this thesis, the conseption of distribution network structure robustness degree is demined systematically, the specific method is determined from the perspective of the "load margin" and the "risk thory", and the evaluation system of the distribution network structure has been proposed.Secondly, on the basis of the power flow calculation, the weak branch of the distribution network is determined according to the branch load rate and load transfer rate and the suitable calculation method of load power margin has been raised.Thirdly, by using the typical load power supply mode and referencing the probability distribution of traction power supply method and referring probability of power-supply, the risk probability of the branch has been calculated and the slip-risk-indicators which is applicable to this article has been obtained. By using a combination of indicators and load margin slip-risk-indicators, the robustness degree of the grid structure of the distribution network can be evaluated. Taking into the load of the grid can be manifested by the robustness degree and vulnerability of grid, and the vulnerability has been adequately studied, the evaluation method used in this thesis could be verified by using the vulnerability of grid which is represented by systemic risk indicator.Finally, through the analysis of the example, the analysis process of robustness degree assessment of the distribution network strcture is descripde. which verify the feasibility and effectiveness of the evaluation method in this paper.