Research On The Power System Dynamics Based On The Trajectory And Trajectory Sensitivity

With the rapid development of modern electric power industry and the expansion ofthe power grid in China power system dynamics become more and more complex. Thepower system security and stability face more challenge. The analysis of power systemsecurity and stability relies on the accurate of the power system models. The foundationof modem measurement system can provide the trajectory which may be helpful for theanalysis of power system dynamics. It is necessary to find the effective method to makeuse of trajectory for the dynamic analysis. Both the trajectory itself and the trajectorysensitivities will play an important role in power system dynamic analysis.The calculation of trajectory sensitivity has usually been carried out by thenumerical integration that derived from the difference of the dynamic system withrespect to a parameter. This algorithm is so complicated that not only the computationresult relies on accurate of the model and parameter, but also it does not reveal therelationship between trajectory and trajectory sensitivity. With the foundation of WAMSmany measured trajectories can easily be got. A convolution method for calculatingtrajectory sensitivity has been proposed by making use of typical system trajectoriesobtained by measurement. So the convolution method can provide the physicalunderstanding of the sensitivity. It is free of the error of parameter since the calculationis based on the measured trajectory, which provides a new way for analyzing powersystem dynamic.Trajectory analysis method can give the stable and instable indices of eachgenerator. It is effective to quantitatively evaluate the power system stability based onthe individual machine energy function. An algorithm is built for calculating thesensitivity of stable index based on trajectory sensitivity. This algorithm has beenapplied in the computation of critical clearing time and the active power limit. When thestability index being figured out, the sensitivity can be got which is useful forconstructing the preventive control strategy to keep power system stable.The dynamics of power-frequency (P-F) can be recorded by the measureequipments fitted at power system. It has been shown that there were some evident errorsbetween the measured P-F trajectory and simulated one with common components modeland their parameters. The effect of kernel parameters to the P-F dynamics has been analyzed based on the trajectory sensitivity. The result has been applied in tuning modelparameter in a large power system. Then the simulating trajectory is as closed to themeasured trajectory by modified parameter as possible. The method provide the base forcorrecting parameters and for studying the dynamic characteristic of thepower-frequency according the measured trajectory.The package software for power system stability analysis is developed which canevaluate the stability and can provide the sensitivity of the stability indices. The softwareis a powerful tool for the analysis and control of power system stability.