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Study on the Voltage Stability On-Line Monitor Based on Local Index

Author: LiaoGuoDong
Tutor: WangXiaoRu
School: Southwest Jiaotong University
Course: Proceedings of the
Keywords: Voltage stability Voltage Stability Index Load voltage characteristics Wide Area Measurement System Adaptive Robust Kalman filter algorithm
CLC: TM712
Type: PhD thesis
Year: 2009
Downloads: 300
Quote: 2
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Abstract


In recent years, the foreign occurs many because voltage instability caused massive power outages, and caused huge economic losses, seriously affected the social life. Voltage stabilization accidents generally have unexpected and hidden features, it is difficult to restore the event of voltage collapse, but the existing voltage stability assessment method is still difficult to meet the needs of online real-time analysis. Based on local indicators of voltage stability assessment method using only relevant measurement information for voltage stability assessment, reducing the amount of network solver, has the advantages of online real-time applications. Of local voltage stability indicators suitable for online applications based on-line monitoring of partial indicators of voltage stability theory and methods, to provide new theoretical tools for grid-line monitoring, prevention and correction control to avoid vicious voltage power system crash accident occurs has important theoretical and practical significance. Thesis as the main research content to local power system voltage stability index and its application to power system Thevenin equivalent parameter identification, establish local indicators of good performance, as well as local indicators, focusing on expanding problem in a multi-machine system development based on local indicators of the power system voltage stability assessment method has an important role in promoting local indicators of measurement-based online real-time assessment of the stability of the power system voltage really applied. Papers introduce uncertainty through observation and dynamic models, the establishment of a power system Thevenin equivalent discrete time uncertain model and as a basis for adaptive adjustment of the fusion forecast covariance matrix and state space Robust estimation, adaptive robust Kalman filter algorithm is proposed to identify Thevenin equivalent parameters. The model and algorithm taking into account the changes in the system operating mode, the of fault disturbance and nonlinear dynamic behavior of load on the power system node Thevenin equivalent parameters, the algorithm has strong anti-interference ability and tracking capabilities. In addition, based on the decomposition UDU ~ T measurement update update application to the Thevenin equivalents parameters identification in solve the problem of computer rounding errors leading to filter divergence Thevenin equivalent of good numerical stability parameter identification. Voltage Stability Monitoring there are certain limitations on the lack of papers based on a simple single-source power transmission system model by introducing reflect the working point area location notation function, proposed a new applied voltage stability for existing local index the node load margin index, it can accurately reflect the node's stable load margin given operating point is located half support system PV curve on the second half of the support of information, indicators with quasi-linear characteristics, and in the vicinity of the bifurcation point are not sensitive to the small change of the load. In addition, the papers reflect the reactive power margin node load margin index identification voltage unstable reactive weak areas, has been a conclusion consistent with the modal analysis method. In order to expand to the multi-machine system load margin index, such as the node, the paper presents two calculations of single-supply system of power transmission equivalents. The first method is based only on the measurement of the state of a system phasor, and direct calculation equivalent system parameters for the power transmission of the single power supply, its equivalent load be monitored only by a point adjacent to the impact load of the bus node region. This method as compared with L indicator method, reducing the impact of the transfer load, improve the accuracy of the index value, and can also be applied to the load-free communication bus. The second method, on the basis of the first method, reducing the need to a range of information, it is only based on monitoring point is adjacent within the region information calculating single Power transmission system parameters equivalent, but use of a plurality of system state voltage The current phasor above adaptive Robust Kalman filter estimated area outside the grid index value. Identification, calculated according to the regional power grid system parameters equivalent set filtering the initial value, and the range of values ??of the parameters to be estimated and node voltage change information, invalid estimate. The second method improves the accuracy of the persistent excitation condition difficult to meet the conditions under indicators, and can be applied to the load-free communication bus, the development of a partial indicator of voltage stability based Thevenin equivalent of Theorem expand multi-machine system. General power system load has a voltage-dependent changes in the characteristics, the paper taking into account the actual situation of the load voltage characteristics of the voltage stability influential characteristic equation when the saddle-node bifurcation point reached by the introduction of a single power supply power transmission system, proposed a kinds accurate account of the load voltage characteristics of the voltage stability of local indicators. The discarded according to the conditions for the existence of solutions of the equation real roots and taking into account the load voltage characteristics of the Jacobian matrix determinant partial indicators of voltage stability indicators accurately reflect the impact of the load voltage characteristics of the system voltage stability. Application NLEQ-RES (global Newton method with the residual based convergence criterionand adaptive trust region strategy) algorithm for solving nonlinear equations encountered in solving local indicators to improve the convergence and the convergence rate of the numerical calculation.

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CLC: > Industrial Technology > Electrotechnical > Transmission and distribution engineering, power network and power system > Theory and Analysis > Power system stabilizer
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