Research On Operation Strategy Of Improving Security And Economy Of Transmission Network Based On Demand Side Management

In the process of development of modern interconnected power grid, it is very necessary to divide the power grid into sub-systems and the tie transmission sections to analyze and manage, and only by accurately controlling the limit tranimission power of tie section, can we furthest meet the load demands of each area under the premise of ensuring the security of system. The fundamental way to improve the transmission capacity of the cross section is to build a new transmission line or to expand the existing line, but increase the transmission limit through newly building and expanding transmission line is restricted by various conditions, so it is very important and realistic to study how to improve the limit tranimission power of the tie sections by making full use of existing transmission lines, power equipment and power management policies.With the introduction of electricity market to the power system step by step demand side management (DSM) has received the widespread attention. Interruptible load(IL), is an important part of DSM, When the active power shortages has appeared in the system because of the peak periods or the states of emergency accidents, the grid companies can interrupt part loads temporarily according to the contracts to reduce the demand,thus, the IL is equivalent to providing the system with a fast virtual system reserve capacity in load side. To obtain the limit tranimission power of sections under the static security constraints, the condition of the traditional N-1 analysis is the loads can’t be lost, and after the introduction of the concept of IL in electricity market environment, the interrupt load management in receiving areas can be used to shed the loads of the user side immediately and actively when the N-1 faults has been happened. This is equivalent to broaden the conditions of the traditional N-1 analysis, and thus the transport capacity of the sections can be improved under the normal operation mode and the economical efficiency of the power system can be improved consequently.This paper introduce the viewpoint of interruptible load of DSM into N-1 static security analysis of transmission capacity of transmission section; and the influence on system operation conditions of using interruptible load to system reserve capacity is studied; A mathematical model on limit tranimission power of section under theconstraints of troditional N-1 static security was established and simplified the model based on actual working condition of system; Broaden the conditions of traditional N-1 analysis through using the interrupt load management in receiving areas and a improved mathematical model of the power flow constraints of transmission section considering the interruptible load is established; The adjustment principle of opposite quantities in pairs analysis method based of branch sensitivity was studies, and the adjustment table for reference and adjustment active power is given in detail. The algorithm solving steps of the mathematical model using the above method is proposed herewith and quantitative relationship between the increments of limit tranimission power of section and the interruptible load quantities is obtained on this basis. The IEEE39 nodes numerical example in BPA running environment shows that the application of interruptible load to improve limit tranimission power of section can improve the operation economy while guaranteeing the security of the power system.