Transmission Network Flexible Planning Under Uncertainties

The enlargement of power grid and revolution of power market bring many uncertainties into the transmission network expansion planning problem. The planning scheme solved by the traditional transmission expansion planning model under certain information doesn't have enough adaptability for future uncertain environment. Based on the idea of transmission network flexible planning, this dissertation studies the safety evaluation index and method of the system considering uncertain factors, builds some new transmission network flexible planning models that can be used for different requirements under uncertain environment and perfects the transmission network flexible planning theory. The main results in this dissertation are as follows:1) The interval minimum load cutting model is built and proved to have optimal solution. After solving this model, the precise global optimal solution of the interval minimum load cutting number can be gotten. The proposed interval analysis method starts a new way for the safety evaluation work of power system under interval information. When solving the interval planning model, it is decoupled into two sub-models that are solved separately. One is the interval most minimum load cutting model that is based on bilevel linear programming model, the other is the interval least minimum load cutting model that is based on linear programming model. After solving these two models, the upper and lower limits of the interval minimum load cutting number can be gotten.2) Using parametric linear programming theory, the"load edges"characteristic existing in the interval most minimum load cutting problem is proved. Using this characteristic and combing the bilevel linear programming theory, the improved branch-and-bound algorithm is proposed. Using this algorithm, the interval most minimum load cutting number can be solved quickly and precisely, and the time to evaluate the safety of power system under interval information can be greatly reduced.3) The transmission network flexible planning model under interval load is built. After solving this model, the planning scheme that is safe under interval load can be gotten. Combing the theory of interval minimum load cutting problem, the improved greedy randomized adaptive search procedure (GRASP) is used to solve this model. The improved GRASP is adaptive to solve the transmission network flexible planning model under uncertain information and improves a lot in calculation speed.4) The transmission network flexible planning model based on credibility theory when the load is fuzzy uncertain is built. The credibility index, which has strict mathematic base and realistic physical meaning, is introduced to evaluate the performance of the system under fuzzy information. Furthermore, the equivalent credibility theorem is proposed and proved. By this theorem, the fuzzy planning model based on credibility theory can be converted into the equivalent interval planning model which can be solved much easier.5) The transmission network flexible planning model considering the line loadability and zone available transfer capability is built. By including the line loadability constraint and zone available transfer capability constraint, the new planning model can better accommodate the load increasing magnitude uncertainty and location uncertainty.6) The transmission network flexible planning model considering the power reserve is built. By including the constraints of generator failure and load increment, the planning scheme solved from the new model can make certain that it is able to transfer the power reserve to maintain the safety of the system when there are generator uncertain failure and load uncertain increment.Analysis and comparison on the Garver 6-node system and a real 77-node system prove the feasibility, validity and applicability of returns of this dissertation.