Research On Voltage Sags Level Estimation Method For Complex Power Grid

Voltage sags has become the most serious power quality problem.In the present,there are two main analysis methods for complex power grid voltage sags,monitoring method and stochastic assessment method.The former has the disadvantages of large investment and long monitoring period,the latter has the disadvantage of introducing subjective factors,and the reliability of the results is not satisfying.The study of voltage sags in China started late,the monitoring period of the voltage sag in the complex network is still short,or it has not been carried out.Lack of long period and high reliability system voltage sag data,which seriously affects the further research on the voltage sag of the actual system.The voltage sag level estimation can effectively combine the advantage of monitoring method and stochastic assessment method.By using the monitoring data of the limited monitoring nodes and the structural analysis of the complex power system,the voltage sag estimation of each node in the whole network is realized.In this paper,based on the existing voltage sag estimation method,a new method of voltage sag estimation based on line segment theory is proposed.The method is based on mathematical analysis,which does not include the approximation process,and can further improve the accuracy of voltage sag estimation.The voltage sag estimation method which is used only for single fault condition is generalized to arbitrary fault conditions,the application range of voltage sag estimation method is extended.Considering the influence of the voltage sag monitoring device configuration scheme,three derivative models of monitoring device optimal configuration are proposed,the two stage optimal allocation model under the condition of bad disposition,the optimal configuration model considering the redundancy,the suboptimal allocation model.Considering the practical objective factors in the practical application,it is more suitable for the practical application of the monitoring equipment configuration and voltage sag estimation.Finally,the correctness and effectiveness of the proposed method are verified by the IEEE 30-bus standard test system.