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Detection and Compensation of Oscillation in Control Loops: The Multiplicity of Oscillation Causes

Armoon, Fazlollah | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56129 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tavazoei, Mohammad Saleh
  7. Abstract:
  8. In this research, oscillation in control loop caused by control valve stiction, external harmonic disturbance, poor controller tuning or their combination, is recognized and compensated. In control valve stiction based study, flaws in one of the important modeling methods are described and some modifications are proposed. For diagnosis of oscillation source, signal is decomposed to its fundamental modes and oscillation in each mode is investigated. Then, from the existence of harmonics in decomposed modes, stiction is diagnosed. Also, relation between peak differences in autocorrelation functions of other modes, results to external harmonic disturbance or poor controller tuning as oscillation source. On the other hand, without signal decomposition, by evaluation of manipulated variable- control signal curve, the stiction and by evaluation of cross correlation function of control and output signals, the stiction or poor controller tuning is diagnosed as oscillation source. After oscillation root cause, a new method based on prevention of stoppage or direction change of movement of control valve stem is presented for stiction compensation. For external harmonic disturbance compensation, by using estimated frequency in signal decomposition, harmonic steady- state control is used. Also, in case of poor controller tuning as oscillation source, controller retuning is performed
  9. Keywords:
  10. Oscillation Detection ; Control Valve ; Oscillation Compensation ; Oscillation Causes Multiplicity

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