Research On Busbar Splitting-based Enhancement Method For Static Voltage Stability

With the development of power market reform and power grid,while promoting rapid economic growth,the operating conditions of the power system are closer to the stability limit,resulting in the problem of static voltage stability prevention and control of the power system is more important than ever.Grid topology becomes an effective measure to improve the static stability of the power system because of its practicality,economy,and easy operation.As one of the important measures of grid topology control,busbar splitting operation has been widely used in the fields of limiting short-circuit current,eliminating voltage violations,alleviating overloads,and so on.In this dissertation,the busbar splitting measure is applied to improve the static voltage stability of the power system,and the related research is carried out on the static voltage stability enhancement control problem by busbar splitting.The main contents include:Firstly,considering the problem that a large number of busbar splitting schemes in power systems and a huge calculation amount for solving effective busbar splitting schemes directly,a screening method based on sensitivity for busbar splitting schemes is applied.In this screening method,a busbar splitting scheme is equivalent to the change of branch admittance matrix of the corresponding grid topology.Based on the power flow equation of the power system,the differential relationship between voltage stability margin and branch admittance parameters is established.The sensitivity method is used to calculate the variation of voltage stability margin corresponding to the busbar splitting scheme to pre-screen the busbar splitting schemes,and the calculation results are compared with the continuation power flow method.The simulation results verify the effectiveness of the sensitivity method in screening busbar splitting schemes.Secondly,the contingency-constrained voltage stability enhancement model is established,and a stage-based busbar splitting scheme solution methodology is proposed for the contingency cases and base case,respectively.To reduce the computation complexity,the above sensitivity method is employed to pre-screen the candidate set in which the busbar splitting schemes can enhance the voltage stability margin,and the effective ones are ranked by the look-ahead margin estimation method.Finally,the continuation power flow method is used to identify the best busbar splitting scheme.The results demonstrate that the proposed stage-based methodology can solve busbar splitting schemes effectively and optimize grid topology,to improve the static voltage stability of base case and contingency cases.Finally,since the load of the power system is dynamic in actual operation,if the busbar splitting schemes are solved only according to the current load level,the grid topology may need to be adjusted frequently.To solve this problem,the day-ahead voltage stability enhancement model is constructed with the minimum number of grid topology regulations as the optimization objective and the voltage stability margin of the power system as the constraint,and a voltage stability enhancement methodology of the day-ahead power system is developed.This methodology includes four stages: status assessment,global time partition,busbar splitting schemes solution,and local period adjustment,which can provide operators with the decision plan of grid topology optimization for the next day,to improve the static voltage stability of the day-ahead power system.The simulation results show that the proposed methodology can reasonably partition the time period and solve the busbar splitting schemes,so that the voltage stability margin of the day-ahead power system is maintained at a high level,and the number of grid topology regulations is effectively reduced.