Calculation Of Transfer Capability In Interconnected Networks Based On Contingency Selection And Risk Evaluation

With the gradually opening up of the electricity market, the calculation of transfer capability of the interconnected transmission networks attracts more and more attentions. Transfer capability should be calculated correctively and rapidly. It should ensure the security and stability of the power network operation, and also guide the power company to obtain the maximum profits in the power trade, which is based on the existing transmission equipment and transmission lines. In the traditional electric power market conditions, the transfer capability calculation only took the reliability of the system operation into account without considering the economic value of the power grid, the results of transfer capability is conservative. According to the situations, this paper study on the transfer capability of the interconnected power network from two aspects: contingency selection and ranking, risk evaluation.The Benders decomposition is applied to calculate the transfer capability in this paper. Based on the fundamental conception of transfer capability, the simple nonlinear programming model is derived by applying the optimization theory, and then the calculation flow of transfer capability based on the decomposition is designed. The calculated results of IEEE-30 indicate that the application of Benders decomposition greatly improve the computing speed and establish the foundation for guiding the operation and dispatching of the power system real-timely.In view of the problem that the contingency the combinatorial number of the contingency is growing exponentially, this paper establishes the multi-level methods for contingency selection and ranking and makes it apply in the calculation of transfer capability in interconnected network. In this method, the pre-selection program, the middle-selection program using DC load flow or distribution factors and the final-selection program using the single iteration of the fast-decoupled load flow are conducted sequentially to select the off-limits seriously faults. The test results of IEEE-30 system show that the evaluation of the transfer capability can be conducted with less computational burdens by using the proposed multi-level method.Because of the contingency uncertainties, the problem of transfer capability calculation is investigated with consideration of the risk evaluation from a probability viewpoint. The Benders decomposition technique is employed to evaluate the transfer capabilities for different contingency states of an interconnected power system together with the state enumeration and selection technique. According to the basic idea of risk evaluation of power system, the reliability model of components and power system are derived, and the optimal transfer capability model are derived and solved by Benders decomposition technique. The test results of IEEE reliability test system and IEEE-30 system proved the corrective and rationality of the model proposed in this paper.