Selection Of Fault Current Limiting Methods And Optimal Allocation Of Fault Current Limiters

That short-circuit current exceeds rated interrupting capacity of breakers is becoming an increasingly critical problem in modern interconnected power grids. Effective current limiting measures are to install optimized fault current limiters (FCLs) as series impedances at selected locations, or to dispatch by optimized districts via breaking some interconnected branches. To optimize the reactance and location of FCLs, firstly decision variables are either reactance of FCLs or the reactance ratios of candidate branches before and after the installation of FCLs; secondly, fault current calculation method is used to formulate constraints to which linearization method should be applied then, that is piecewise linearization method should be applied after superposition principle based fault component method and one-order Taylor expansion method of multiple-variable function should be applied after node voltage method based direct calculation method; thirdly,4types of mixed integer linear programming (MILP) optimization models of FCL allocation are established. To dispatch by optimized districts, firstly, node voltage method based direct calculation method is used to formulate constraints which contain the decision variables of on and off state of branches, branch currents and node voltages, and then MILP model is established without error. To increase efficiency of optimization, sensitivity factors are calculated to help reduce the number of candidate branches of FCLs’ allocation reasonably. Optimal solutions are obtained by invoking CPLEX optimizer on the platform of Visual Studio. Optimal results of the test on IEEE-39bus system and succedent error analysis show that after optimization2types of MILP models can offer practical allocation of FCLs with small error, and that dispatching by optimized districts model after optimization can offer reasonable branch breaking deployment, and that both measures can limit node short-circuit currents below interrupting capacity of breakers, and thus prove the validity for the proposed MILP models.