Optimization And Control Of The Short Circuit Current Of The Ultra High Voltage Hybrid Power Grid System

With the development of the society and economy, the scale of the power system has expanded continuously, and the interconnection between regional power grids has greatly enhanced. To meet the ever increasing power demand, and to take into consideration the fact that China has an unbalanced distribution of power resources and long distance between the energy and load centers, it is both reliable and economical to develop the UHV transmission system, benefiting the overall utilization of multiple resources, the interconnection of large power grids, and peak staggering. However, the construction of a higher level power grid will inevitably influence the short circuit current level of the original grid to some extent, and how to limit the short circuit current level by various short-circuit current limitation methods still worth studying.In this paper, the inevitability of developing the UHV transmission system was first analyzed, and the influence by the UHV system on short circuit current level was briefly introduced. Subsequently, five frequently used short-circuit current limitation methods were introduced from work principle and applicable situations, and the application and effect in engineering application perspectives were given, referring to related literatures. Moreover, the basic principle and algorithm flow of the PSO method and the relevant concepts of the multi-objective optimization were introduced. After the short-circuit current limitation methods model considering single economic target, a MOPSO model considering several short-circuit current limitation methods based on Pareto optimal solution set was presented. The target of the model was to both minimize the investment and maximize the current limitation effect, and a Pareto front curve was obtained after the optimization. The model was applied on the New England 39 bus standard test system. In the process of optimization, the Sigma function was used to calculate the global optimal position of every particle under multi-objective, and the curve of the targets was plotted. Lastly, the short circuit current level of the power grid before and after interconnecting with the UHV system was compared, and the trend was analyzed. The search space was reduced according to the rate of change of short circuit current relative to short-circuit current limitation methods, to solve the optimal allocation of the current limitation method after the interconnection with the UHV system.