Research On Subsynchronous Oscillation State Monitoring And Parameter Identification Method Based On Synchroextracting Transform

Power system subsynchronous oscillation is a hot issue in power system research.Recently,frequent sub synchronous oscillation accidents often happen with the use of power equipment and switching elements in the power grid.In this paper,a new method for power system subsynchronous oscillation monitoring and parameter identification is studied based on measurement signal processing.Firstly,The different mechanism of subsynchronous oscillation is analyzed and compared.The mechanism of typical subsynchronous oscillation in recent years is analyzed in detail.Then,according to the L-C oscillation mechanism,the grid connected model of direct drive fan is built on the MATLAB / Simulink,which provides accurate simulation data source for subsequent analysis.Lastly,the requirements of the system are analyzed,and the overall design of the system is determined,mainly studies the power frequency component extraction,state monitoring and parameter identification of subsynchronous oscillation signal.In view of the fact that the power frequency component of the signal accounts for a large proportion and interferes with the subsequent frequency domain analysis,a sogi-fll structure is proposed,which real-time estimates power frequency components and complete the extraction of power frequency components.Aiming at the characteristics of subsynchronous oscillation signal including single mode component and power frequency jump,sogi-fll is improved and an adaptive s-sogi structure is proposed.By processing the test signal and model signal,it is verified that the adaptive s-sogi structure can estimate the power frequency components in real time and complete the extraction of power frequency components.The key of monitoring the subsynchronous oscillation state is to judge whether there is continuous subsynchronous oscillation and analyze the starting time and dominant mode.The traditional analysis of subsynchronous oscillation is usually post analysis,which proposes a visual monitoring method of subsynchronous oscillation based on synchroextracting transform.The signal sampled by the sliding window is synchroextracting transform in real time,and draw 2D time-frequency map for reference.Simulation results show that the method can effectively identify the number of subsynchronous oscillation modal components,the corresponding frequency and starting time of each modal component and the dominant modal component,and realize the visual monitoring of subsynchronous oscillation state.At the basis of similar frequency in the analysis of subsynchronous oscillation,and the errors reconstruction and parameter identification,In this paper,a higher accuracy method is proposed,which combines second-order synchronous extraction transform and Hilbert transform.Firstly,the two-order synchroextracting transform is used to obtain its various modal components.Then,the inverse transform is used to decompose and reconstruct the various modal components.Finally,the Hilbert transform is used to identify the parameters of the extracted single modal component to identify its frequency,damping ratio,attenuation factor and other main parameters.The test signal,model signal and recording data are used to verify them.The simulation results show that the proposed method has some advantages in parameter identification of subsynchronous oscillation compared with short-time Fourier transform and other methods.