Research On Identification And Safety Check Of The Critical Transmission Section For Power System Static Security Considering Wind Power Access

Analysis on historic blackout accidents shows that the process is commonly resulted from simple faults,which lead to power transfer,followed by chain failures,and finally come to blackout.With the expansion of power grid,the enhancement of interconnection of power grid,the rapid development of power market as well as the increasing penetration rate of renewable energy source such as wind power,the difficulty of static security analysis of power system is increasing.How to quickly and accurately identify the transmission sections existing overload risk and judge the risk degree is an important issue in the safety analysis of the power grid.In this paper,transmission section is taken as the research object and outputs of the thesis are showed as follows:The topological characteristics of power system are analyzed,and the power system network is simplified.A maximum flow and minimum cut theorem based scheme is proposed for identification of the key transmission sections in a power grid.The proposed algorithm transforms the power grid into a directed weighted graph with consideration of the power flow and capacity margin of the power grid during the minimum cut scanning.The searching results are stored in a search tree storage and the transmission sections are obtained through network segmentation.All the transmission sections with "N-1" and "N-2" overload risks can be quickly and accurately identified and follows the cut set characteristics.By searching the power flow transfer path,the power flow transfer relationship of the line inside the transmission section is analyzed.According to the loop current method and the principle of conservation of power transmitted by the section,the proportional coefficient of power flow transfer inside the section in the case of the line “N-1” or even “N-k” outage is quantitatively calculated.The power limit of transmission sections considering the static safety constraints are calculated based on the power transfer factor.Performance and feasibility of the proposed method is verified in the 39-bus New England system and the IEEE 300-bus system.Considering the fluctuation and correlation of power generation output of multiple wind power,a Vine Copula model of multivariate wind power model was established,Latin hypercube sampling and Rosenblatt transform were used to generate several groups of samples in accordance with wind power correlation characteristics which were used to calculated stochastic load flow by sampling method.The network flow diagram model was modified according to the probability distribution interval of the line power flow,and the key transmission sections were searched based on the revised network flow diagram.Considering wind farm output,the probabilistic transmission power limit of transmission section is calculated,and the influence of wind power output on the power limit is analyzed.The research of this thesis shows that the heavy overload events that endanger the static security of the power system mostly occur in the critical transmission section and the uncertainty and fluctuation of wind power will affect the static safety and stability of transmission section.The transmission section identification method based on the maximum flow and minimum cut theorem proposed in this thesis can effectively identify the key transmission sections,find out the weak links of the network and carry out stable monitoring.The optimization algorithm based on the power transmission distribution factor can quickly solve the transmission power limit of the transmission section and quantitatively analyze the transmission capacity of the transmission section.In view of the fluctuation of wind power,the proposed model is modified to make it suitable for the transmission section identification and transmission capacity analysis under the scenario of wind power fluctuation,so as to meet the needs of static security analysis of power system under the background of the continuous increasing of new energy power generation permeability.