Identification Of Low Frequency Oscillation In Power System And Research Of Internal Resonance

The safe and stable power supply of the power grid is a necessary condition to ensure the steady economic growth of the country.However,the expansion of the scale of the power grid and the deterioration of the environment seriously harm the stability ofthe power system.The power system is a complex and large-scale interconnected nonlinear time-varying system.There are many kinds of oscillation types in the interconnected power grid.The low frequency oscillation caused by weak connection,weak damping,strong resonance and its own nonlinear structure has become one of the important factors to harm the security of the power grid and limit the power of the transmission of the power grid.Therefore,from the point of view of dispatching operation,accurate and effective identification of low frequency oscillation will be an important issue in the research of power system stability.In recent years,more and more new energy is used,and the random excitation produced by new energy generation is injected into the power system,and the internal resonance phenomenon will be caused,which puts forward a new problem for the identification of the low frequency oscillation of the power system.Firstly,a modified Prony algorithm based on the two order derivative method is proposed to identify the low frequency oscillation in the wide area measurement system.The two order derivative method is used to determine the fitting order of the Prony algorithm,and the practicability of the method is proved by an example analysis and comparison with the traditional Prony algorithm.Then,based on the internal resonance mechanism,the nonlinear factors in the low frequency oscillation of the power system and the nonlinear interaction between the modes are analyzed,and the conditions of the internal resonance are simulated.The internal resonance can lead to the strong nonlinear interaction between different oscillating modes,which makes the results of the linearized low frequency oscillation analysis very different.Because the modes of power system are not completely decoupled,it is necessary to pay attention to the internal resonance phenomenon in the low frequency oscillation analysis of power system.Finally,the generation conditions of internal resonance are expanded under generalized forced oscillation,and the simulation results show that:Under random excitation,there is no need to satisfy the specific multiple relation between the frequency of the system oscillation mode and the internal resonance phenomenon,that is.the internal resonance phenomenon is more easily excited under the generalized forced oscillation.All these provide more ideas for the analysis of low frequency oscillation of power system.