Transient Stability Assessment Of Power System Considering Stochastic Disturbances

With the large number of grid-connected distributed power sources,such as new energy sources,and the increasing penetration of plug-in electric vehicles,stochasticity has become one of the significant characteristics of power systems.In the past,because of stochasticity is not prominent,the deterministic models and methods are often used in transient stability analysis,which are not applicable to stochastic systems.For the system considering stochastic disturbances,what changes will happen to transient stability,and how to quickly and accurately analyze and evaluate transient stability is a new research topic.Today,with the increasing stochasticity,the research of this topic has important prospective significance for maintaining the safe and stable operation of power systems.Firstly,the research of stochasticity of power systems and transient stability analysis methods are summarized.Then,based on the theory of It? stochastic differential equation,the common stochastic disturbances in power system are classified and modeled,and the numerical simulation method is given.A power system mathematical model with stochastic disturbance term is established,and a new framework for transient stability assessment of stochastic power system is proposed.Through the numerical method of stochastic differential equations,the transient stability assessment results of the system can be obtained.Secondly,the transient stability index of stochastic power system,stability probability,is determined.Based on the classical equal-area criterion and the stochastic differential equation model of power system,the modified EAC method for transient stability of single machine infinite bus system under external stochastic excitation is derived by using It? integral.The proposed method is applied to calculate the critical clearing time of single machine infinite bus system.Compared with the numerical simulation method,the correctness of the proposed method are verified.According to the existence interval of stochastic disturbance,transient stability is divided into different cases for discussion and comparison.The stability probability of the system with global existence of stochastic disturbance and with only stochastic disturbance during fault are compared.The results are quite different,and it need to be screened according to the correlation between the fault and stochastic disturbance in practical application.Then,the transient stability analysis is extended to multi-machine systems with multiple stochastic disturbances.Based on the stochastic differential equation theory and the quantification theory of motion stability,the modified EEAC method for transient stability analysis of stochastic systems is proposed.The stochastic disturbances are equivalent,and the system model is simplified by model aggregation and dimensionality reduction.Comparing the results of the proposed method with those of the numerical simulation method,it is shown that the proposed method can significantly reduce the computational complexity while guaranteeing the accuracy.The influence of the intensity and type of stochastic disturbance on the transient stability of power system is studied and analyzed by the proposed method.The transient stability of power system under the same intensity of white Poisson noise and white Gaussian noise stochastic disturbances are compared.