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PMU-Based Identification and Analysis of Power System Low-Frequency Electromechanical Oscillations Using Ringdown Data

Hatami, Mohammad Reza | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45434 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Parniani, Mostafa
  7. Abstract:
  8. Poorly damped Low Frequency electromechanical Oscillations (LFOs) confine the capability of power system transmission lines. This phenomenon, which is the result of dynamic interactions among generator groups, may make the system prone to small- signal instability in some cases. Due to the use of some system controllers such as AVRs, these oscillations are inevitable.
    Hence, electromechanical modes detection and assessing stability margin are important requirement in power system planning and operation, and can provide significant help to power system operators by preventing stability problems.
    From the distant past, in order to monitor small-signal stability, power system operators have been modeling the system and utilizing analysis software. In today large power systems, however, model- based simulations need a lot of computation. Furthermore, it is impossible to simultaneously apply the system changes into the model. In recent years, real-time monitoring of power system dynamics has become viable with the utilization of synchronized Phasor Measurement Units (PMU) and wide area measurement in power systems.
    In this regard several advanced signal processing methods have been proposed. In this thesis, a novel online monitoring method based on real-time wide-area measurement is proposed in order to evaluate the current states of LFOs.
    Quadratic time- frequency distribution, as a powerful tool for analyzing non-linear non-stationary signals, is used for modal parameter estimation, including instantaneous frequency and damping. Instantaneous frequency is directly calculated by local maximization of the distribution in each time sample. Also instantaneous damping can be achieved using the envelope of the signal modes.
    Different simulations are carried out and the efficiency of the proposed method is exhibited by applying it to the simulated data and real data of WECC 1996 blackout
  9. Keywords:
  10. Small Signal Stability ; Signal Processing ; Phasor Measurement Unit ; Time-Frequency Representation

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