Study On Power System Controlled Islanding Time Considering Transient Stability

With the development of society and new energy, the stable operation of the power system has been severely tested. How to keep the power system stable and avoid the occurrence of large-scale blackout has become a serious problem. The power system controlled islanding is the generator separation control measure, when power system subjected to large disturbance or long time after failure, it is important for avoiding the occurrence of power system accidents.Splitting time is a key factor deciding the success of power system separation. The conventional study of splitting are based on the information of power flow, avoid the transient stability problem and splitting time by strong assumptions. For stability problem, this paper introduces Time-domain Simulation, EEAC and TEF method. The Energy Function method is the theory basis of the analysis and calculation. This research focus on the splitting time problem by transient stability analysis, using transient energy function to quantify stability of islands under different disturbance background, and determining feasible splitting time solution by stability critical energy.The theory basis of this paper includes:the transient stability theory, the theoretical basis of transient energy function method. The paper uses CUEP method as calculation method. Research discusses the relationship between island stability and system stability, interpret the key problems of transient stability in the process of islanding:the stability of islands determines success of islanding. Three main steps of solving the stability problem of the island can be concluded as follows:constructing island energy function; Calculating the critical energy based on the trajectory; Comparing the islanding moment energy to the critical energy. If the former is smaller than the latter, the island will be stable; Otherwise, the island may be unstable.Based on the introduced theory and method of transient stability, the paper gives the calculation method of transient energy function of IEEE 118-node system, and analysis the stability of islands by calculating feasible splitting time, processing the splitting time analysis in islanding under different disturbance background.Research shows that, in accordance with different background disturbance and strategies of splitting, the island feasible solution shows five different situations:any time, can be less than a critical moment, is larger than a critical moment, the intermittent time window characteristics and no feasible time. In this paper, the effect of key parameters changes like fault clearing time and topology change for controlled splitting time are analyzed. This is the first research explaining the splitting time problem in islanding from the theoretical level, providing new ideas and support for the further study of controlled islanding problem solution.