Studies On Real-Time Transient Stability Determination Of Power System And Control Technology Based On Responsed Data

This dissertation focuses on the rotor angle stability analysis based on wide-area measurement information, including mechanisms analysis, mathematics modeling, extraction of dynamic characteristic data, prediction of disturbed trajectories, real-time transient instability criterion, recognition of principal mode and quantitative research of generation capacity tripped. Then a response data driven transient stability control strategy based on real-time measurement data is proposed.Response data of network can be collected by wide-area measurement system and it is need to extract the dynamic characteristic data for transient stability analysis in order to avoid dealing with the huge number of PMUs data and improve the speed of stability analysis. Dynamic characteristic data is required to reflect the process of transient stability after disturbance. Considering the complexity of transient stability problem of multi-machine system, it is difficult to identify the stability of power system correctly, so multiple characteristic data is used for transient stability analysis based on wide-area measurement information.The tendency of disturbed trajectories variation is complex and the curves have strong nonlinear characteristics. In the prediction of disturbed trajectories, the parameters of prediction model must dynamically adjust to cope with the variation of nonlinearity of curves in real-time to enhance the prediction ability. Based on detailed analysis on the relation between prediction performance and model parameters, a self-adaption technology for model parameters is proposed in this dissertation. Using the latest measurement data to calculate the parameters and cope with the variation of nonlinearity for the purpose of realizing overall optimal performance prediction. The proposed technology includes inner and outer loop calculations. Inner loop focuses on the calculation of prediction results and the outer loop focuses on the calculation of parameters with the latest measurement data according to principles of adaptive adjustment of model parameters.Real-time transient stability criterion is the key of real-time transient stability analysis. For multi-machine power system, dynamic characteristic information of tie lines in transmission section can reflect the oscillation status between two systems when the oscillation occurs. A power-phase angle-frequency criterion based on the characteristic information of tie lines is proposed. Few and vital network information is used to design this criterion, so it has fast calculation speed and practicality to be used. There are three steps to identify the unstable status with this criterion. Firstly, identify if the system operating point is in the unstable area. Secondly, identify if the system has the tendency to lose stability. Finally, confirm if the system operating point is beyond the unstable equilibrium point. Simulation results based on actual power system show that the criterion can identify transient angle stability correctly.Rotor angle instability and transient voltage instability are two forms of system instability during the post disturbance. Recognition between them is the pre-preparation for power system emergency control. Research shows that the variation of active power of tie lines in transmission section includes two components. The first component is associated with the bus voltage magnitude of tie lines; the second component is associated with the phase angle of bus voltage for tie lines. The relationship between different unstable modes and the components is shown as follows:When the transient voltage instability is the principle mode, the variation of active power in tie lines is mainly determined by the first component. When the rotor angle instability is the principle mode, the variation of active power in tie lines is mainly determined by the second component. A criterion for recognition of principal mode based on this relationship is presented for the subsequent emergency control.Estimating the generation capacity to be tripped suitably is a pre-preparation for power system transient stability emergency control. The methods of estimating generation capacity tripped based on transient energy function requires that the function can accurately reflect the energy which causes the system instability. Based on the corrected energy function, accelerated energy function of power system is defined. With the detailed analysis of accelerated energy of power system, a method to estimate generation critical capacity tripped is presented. Different from the equal-area criterion, this method don’t need to calculate the unstable equilibrium points, integral path determined and calculation process are simple.