Study On Electromechanical Dynamic Characteristics Of Power Systems Based On Trajectory Eigenvalue Sensitivity

The practical power systems suffer a variety of disturbances in normal operating state. It will present complex dynamic characteristics due to the complexity structure and quick response. The safe and stable operation of power grid will be affected. With nonlinear and time-varying characteristics of power systems gradually strengthened and the relativity of disturbance, traditional mode analysis of power systems is no longer applicable. In order to study the dynamic characteristics of nonlinear non-autonomous power systems, trajectory eigenvalue technique is proposed and used in dynamic characteristic analysis under large fault. The inadaptability of the traditional eigenvalue analysis method on equilibrium point can be solved by it. At the same time, the dynamic sensitivity information can quantitatively reflect the effects system parameters to system states. And it provides guidance to improve the dynamic performance of power system. Trajectory sensitivity based on system disturbed trajectory is widely used in power systems dynamic stability analysis.When time-varying and nonlinear factors can not be ignored, the electromechanical dynamic characteristics of power systems will no longer be accurately analyzed by traditional mode analysis. Trajectory eigenvalue technique is introduced to solve the problem. The generator swing equation at non-equilibrium point is linearized and trajectory eigenvalues are calculated. The changes of trajectory eigenvalues on different states are studied by changing perturbation conditions and the system parameters. The factors affecting oscillation amplitude, oscillation period and magnitude of eigenvalues are studied. Combined trajectory sensitivity with eigenvalue sensitivity on equilibrium point, the trajectory eigenvalue sensitivity is proposed. Then two kinds of calculation methods of trajectory eigenvalue sensitivity are compared. Finally, numerical perturbation method is used to calculate the sensitivities trajectory eigenvalues to system parameters. The advantages of trajectory eigenvalue sensitivity compared to the eigenvalue sensitivity on equilibrium point are verified in study of electromechanical dynamic characteristics. The inadaptability of eigenvalue sensitivity on equilibrium point in time domain is found.Trajectory eigenvalue sensitivity is a new method to study the electromechanical dynamic characteristics of power systems. The influence degree parameters to oscillation mode of power systems in each time section can be obtained. And the effects parameters to system are also analyzed during the whole dynamic process. It combines the advantages of static eigenvalue sensitivity and dynamic trajectory sensitivity and is of great value to study the power system dynamic characteristics considering time-varying nonlinear factors.