Power System Fault Detection And Isolation Based On Adaptive Approximation Method

The emerging WAMS/PMU measurement system provides synchronous electrical phasor information of power grid nodes for power system analysis,and the data refresh rate has been dramatically improved,which makes it possible to analyze faults based on power system transient models.The most critical issue in fault diagnosis under the WAMS synchronous phasor measurement system is how to quickly and accurately locate the fault area.This paper is based on the study of the nonlinear swing equation of the power system,and mainly uses nonlinear observers and approximators to solve this problem.The work of the paper includes:(1)The history of power system fault diagnosis is reviewed,and common methods of power system fault diagnosis are introduced.(2)The basic idea of using an observer for fault detection and location is introduced based on LTI system.Then it is extended to a class of nonlinear uncertain systems,using the approach of embedded observers to approach the uncertain dynamics and fault dynamics,and storing this information in an observer bank.Finally,the problems of fault detectability and isolability under a given threshold are analyzed.(3)The method of fault detection and diagnosis based on power system dynamic model is studied.Firstly,a model of a multi-machine power system is established and converted into a discrete form.Secondly,the concepts of interconnection set,global fault set,fault impact set and local fault set are defined.Then the fault detection and approximation observer is constructed,the corresponding adaptive threshold is derived,the fault detection logic is established,and the fault detectable conditions are analyzed.Then,a fault isoaltion estimator under the general observer scheme is constructed,the corresponding adaptive threshold is derived,the fault location logic is established,and the fault location condition is analyzed.(4)Simulation of the fault diagnosis mechanism was carried out on Matlab,the effectiveness of the proposed scheme was verified on IEEE 3 machine 9 bus system and IEEE 10 machine 39 bus system.