Research On Composite Generation And Transmission Expansion Planning

In power system expansion planning,the investment of generation and transmission expansion planning is larger,and the impact on security of power supply is also more profound than that of distribution system.With the development of big power network and generator,generation and transmission expansion planning requires more sophisticated methods and has significant value in economy and security of big power system.In composite generation and transmission expansion planning(GTEP),enduring the uncertainties of load and N-K contingency is very important to adequate security of power system,and in optimal stage of GTEP considering AC power flow constraint is very difficult due to the non-linear and non-convex AC power flow.The paper furtherly studied the mathematical modeling and global solution of GTEP from the two aspects: the uncertainties of load and N-K contingency and AC power flow constraint.The main works are as follows:(1)To propose a multi-scenario GTEP method based on mixed integer linear programming(MILP),which has multi-scenario characteristics and can be applied into the preliminary optimization of candidate generators and branches.Separation of existing and candidate branch DC power flow and the big M linearization are used for making the multiscenario GTEP model into a MILP.(2)To establish the best and worst situation models under the uncertainties of load demand and N-K contingency,and study the minimum and maximum load shedding probem under interval load and N-K contingency.The K value of contingency element is general.The worst model of interval load and N-K contingency is a bi-level linear programming,it can be transformed into a MILP problem by strong duality theory and linearization method.Thus the worst model can be globally solved by mathematical programming.The worst situation model can be applied into the security analysis of GTEP.If the worst load shedding satisfies with the security standard,the load shedding of all situations must satisfies with it.(3)To build the model of N-K contingency constrained GTEP under interval load based on DC power flow and propose its solution method with global optimization programming.These variables of N-K contingency constrained GTEP under interval load are divided into expansion planning variables,uncertainties variables for load demand and N-K contingency,and operation variables.The model of N-K contingency constrained GTEP under interval load has a tri-level characteristics.Based on the model and its solution of the the worst load shedding of N-K contingency under interval load,the tri-level programming can be globally solved by Benders decomposition theory.In order to reduce the iteration times of solution,a primal and dual Benders decomposition method also is proposed.(4)To present a framework which transformed non-linear and non-convex optimal power flow to mathematical global optimal power flow by mathematical relaxation and approximation methods.To summarize semi-definite programming of optimal power flow and its necessary and sufficient conditions of global optimum,and propose the feasible verification method of AC power flow with maximum load power flow.To establish two optimal power flow model based on second order conic relaxation and approximation,and analyze the relation of their model solutions and primal optimal power flow solution.In order to tighten the relaxation of optimal power flow with second order conic relaxation,approximation angle constraints are studied.(5)To produce second order conic relaxation and approximation AC power flow constrained GTEP models based on optimal power flow with second order cone model.The two models can be globally solved by mixed integer second order conic programming.To compare the results of DC and second order cone AC power flow constrained GTEP and analyze them by maximum load power flow.Analyses on 24-bus and 118-bus systems demonstrated the feasibility,validity and applicability of these models and methods the paper proposed.