Research On Line Identification And Elimination Methods Of Active Power Flow Over-limit Of Transmission Sections In Power Network

With the great progress of the national economy,the society’s demand for electricity is increasing,and the grid structure of the power system is becoming more and more complex.At the same time,the development of all walks of life and the normal operation of society both depend on safe and high-quality power support.In order to avoid the occurrence of serious events such as cascading outages caused by regional overload or faults,power system operators are required to conduct effective online security monitoring of the entire network’s operating status.Dispatch operators often select the key components or lines for monitoring,and focus on monitoring the large power plants and important transmission sections generally.As an important hub for power transmission in different regions,transmission sections are always the focus of attention.If over-limit situation appears in transmission sections,it is necessary to find appropriate control measures to eliminate the over-limit of the transmission sections.The traditional transmission section lines are selected based on experience,it exists the multiple selection and missing selection problems,and based on the actual situation that the power flow of the transmission sections may exceed the limit during the operation of the power system and affects the normal operation,In this paper,the identification of the transmission sections in the power network and the control algorithm of safety correction when the active power flow of the lines contained in the transmission sections exceeds the limit to achieve the purpose of eliminating the transmission sections over-limit are studied.The main contents of this article are as follows:The basic principle of AP(Affinity Propagation)clustering algorithm is studied,and the power network is divided into sub-regions using this algorithm.The similarity matrix is constructed by selecting the negative Euclidean distance between the nodes and the transmission betweenness of the line,and the network partition is realized based on the geographic coordinates and electrical parameters of the nodes.At the same time,the influence of the preference degree on the division result of clusters is discussed.The basic principle of the GN(Girvan-Newman)splitting algorithm is studied.The sub-region division of the power network is completed based on the geographic distance and electrical distance between nodes.The calculation process of the modularity Q is analyzed,it overcomes the defect that the GN splitting algorithm can not determine the final number of divided sub-communities.After completing the basic network partition using AP clustering algorithm and GN splitting algorithm,according to the definition of the transmission section,combined with the cut set theory in graph theory,the two methods of determining the cut set branches in the network are studied,and the initial transmission section lines are selected,the line identification of the initial transmission sections is completed.The calculation process of the line outage distribution factor(LODF)is analyzed,the initial transmission section lines are corrected by the distribution factor,the final identification of the transmission section lines is realized.The safety correction method of transmission sections based on comprehensive sensitivity is studied.The basic power flow sensitivity of the generator node’s active power output to the line is analyzed,combined with the active power flow over-limit weight of each transmission section,the comprehensive sensitivity matrix of the generator node to each transmission section is established,select the generators with a larger value to adjust the active power output step by step.The safety correction method of transmission sections based on the primal-dual interior point method is analyzed,a mathematical model to eliminate the active power flow overr-limit of the transmission section lines is established,and the power flow reconstruction of the entire network is carried out by adjusting the active power output of all generators in the system,so that the active power flow of the transmission section lines that exceed the limit is restored to the upper and lower limit,thereby the active power flow over-limit is eliminated.The standard node network and typical case of the actual system are used to identify the transmission section lines,the rationality of the sub-areas division result is verified.When the lines contained in the transmission sections exceed the active power limit,the safety correction methods based on the comprehensive sensitivity and the primal-dual interior point method are used to deal with the problem,and the output data of the corresponding generators is adjusted to achieve the purpose of eliminating the over-limit condition.The effectiveness of the proposed control methods is verified.