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Stabilization of Subsynchronous Oscillations of ILAM Refinery Gas Turbine Units in Islanded Operations

Sheikhi, Mostafa | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49910 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Mokhtari, Hossein
  7. Abstract:
  8. Ilam refinery has three synchronous generator units each with a capacity of 26.5 MVA and two six-phase LCI-fed synchronous compressors, each with a capacity of 8 MW. Generators of Ilam gas refinery have instability issue in case of island operation. With launching one generator unit and then connecting two compressors the instability problem and tripping of the generators appear. Given the importance of this issue, various tests and corresponding measurements in both electrical and mechanical aspects were carried out at the plant in on-grid and island operations to analyze the cause of instability phenomena. The mechanical part of tests analyses the frequency of oscillations and vibration in turbine-generator’s shaft and the electrical part’s data include various signals and power quality parameters that are required for the analysis of aforementioned events. This project contains a summary of measurements and investigations to solve the problem of stability in the refinery through changes in the network or controlling line commutation inverters, network loads or other controllers. The results show that in some cases, the interharmonics produced by the LCI converters match turbine-generator natural frequencies and cause torsional interactions. Therefore, vibrations on the generator shaft could be severe, resulting in Trip. It can be found that these interharmonics are multiples of the difference frequency between generator and compressor that have been produced due to the power grid structure
  9. Keywords:
  10. Power Quality ; Stabilization ; Interharmonic ; Subharmonics ; High Voltage DC Power Transmission ; Power Systems Dynamic ; Six Phase Motor ; Torsional Interaction

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