Study On The Power System Disturbance Propagation Mechanism Based On WAMS

Disturbance is the direct cause of the destruction of safe and stable operation of power grids. How to analyze the scope, disturbance level and safety control plays an important role in improving the safety level of the power grid. With the increase in the number of nodes, the traditional analysis method which analyzes system dynamic based on electromagnetic wave equations. The disturbance propagation information could not outline and the multi machine system stability could not be predicted also. In this dessertation, spatial information is introduced to the Differential algebraic equations which describe the system dynamic. The electromechanical wave theory is adopted to describe the spatio-temporal propagation mechanism disturbance propagation. So, based on the propagation mechanism, introducing the PMU measured data, identifying the disturbance and the propagation parameters and predicting the disturbance influence will improve the system security level.The sectinaized homogeneous structural frame mode of chained and practical power system is put forward for the study of disturbance propagation. The impact scope of the moment of inertia of a generator is analyzed and the equation for electromechanical wave propagation is established. The analytical solution of the proposed equation is derived. On the basis of chained power network, by revealing of the characteristics of disturbance propagation in practical power systems, the hierarchically symmetrical distribution approach is proposed to deal with the spatially concentrated inertias. The spatial structural frame structure model of power network is built. The consistency between the structural frame model and discrete inertia model is confirmed by the state transition matrix.The characteristics of disturbance propagation in power networks are studied from electromechanical wave point of view. The wave transfer function which can describe the amplitude and phase variations is derived. The wave transfer function which can describe the amplitude and phase variations is derived. The propagation characteristics of different frequency disturbances are analyzed. The corner frequency of the discrete inertia model is proposed. The frequency dispersion and local oscillation are revealed as well as their relationships with corner frequency.A WAMS based disturbance location algorithm is put forward. By comparing the short-period volatility of frequency at steady state and monotonicity when the disturbance arrives, an sliding time window based identification method for the arrival time of disturbance is put forward. The Floyd method for the shortest path search is applied to build the reference time matrix which shows the propagation time of electromechanical wave induced by different disturbance locations. The disturbance is located by sequential minimum distance classifier. The proposed algorithm has less searching space dan can meet the requirement of online use.A prediction method of disturbance arrival time is put forward which will provide arrival time for online active controls based on disturbance propagation theory. The weighted undirected graph of structural frame model is formulated as well as the adjacent matrix which is based on the disturbance propagation time in segments. The Dijkstra algorithm based shortest path searching algorithm for the arrival time of electromechanical wave is proposed. Effect factors of the measured arrival time of electromechanical wave are analyzed. The selection criterion for the threshold of the measured disturbance arrival is put forward.