Transmission Congestion Cost Allocation And Application

Congestion is a common problem in electric power system and it affects economy and security of system operation. Under electric power market invironment, research on congestion management has theoretical significance and practical value. Congestion management is a complicated system project and it relates to many factors, such as structure of power market, network planning and system operation. In this paper congestion cost issue in real-time market, day-ahead market and forward market is researched. Congestion cost allocation methods in bilateral model are proposed. The allocation can provide economic signal for resolving congestion problem in operation and is favorable for system operating economically and safely in a short run. Network expasion scheme based on congestion cost signal is presented.A priciple of congestion cost allocation based on the degree of involvement is proposed. According to the principle, the cost of relieving a congested facility allocated to each transaction is proportional to the power flow change on the congested facility caused by the transaction. The Aggregated allocation method based on total transaction magnitude is adopted to determine the power flow in the congested line caused by each transaction in day-ahead market accounting, and the sensitivity method based on incermental transaction magnitude to accounting in real-time market.A method based on sensitivity is presented for allocating the cost of congestion relief in real-time market. Firstly, the sensitivity of congestion cost with bilateral transaction power is calculated. Then the cost allocated to each transaction is derived from the sensitivity multiplied by magnitude of contract power. For short-term run, the sensitivity can provide good economic signals. Differences between congestion cost and merchandise surplus are analyzed. Research indicates that the proposed method can allocate fastly the congestion cost, and the efficiency is not related to quantity of congested lines and bilateral transactions.A method of allocating congestion cost to bilatarel transactions in day-ahead market is proposed. The proposed method is a two-step process, in which the total congestion cost is firstly allocated to congested facilities and then to each transaction involved. The cost of relieving a congested facility allocated to each transaction is proportional to the power flow change on the congested facility caused by the transaction. The more the power flow change on the congested facility caused by the transaction is, the deeper the degree of involvement by the transaction is. The results can reflect reasonably the degree of involvement by each transaction in the congestion and provide correct price signals contributing to relieve congestion. Aggregated allocation approach is adopted to determine the power flow in the congested line caused by each transaction, which makes the proposed method suitable for accouting in day-ahead market.A framework for transmission planning in a deregulated electricity market environment is proposed. The level of congestion in the network is utilized as the driving signal for the need of network expansion. The network expansion problem is decoupled into multiple-stage planning subproblems. In each subproblem, validity index of candidates are computed. Then the total validity index(TVI) of each candidate is computed and the candidate which is provided with the maximal total validity index is selected as the optimal scheme. The proposed method determines the location according to validity index composed of running cost, investment cost and load benefit, which can improve economy and reliability. Meanwhile, the candidates are determined based on congeston performance index(CPI) which is derived from congeston cost and shadow price. CPI provides mathmatics basis for planning, which contributes to improve efficiency and quanlity of planning.