Mitigation of harmonic problems in an offshore drilling jack-up rig power system

  • Mamdouh Alhaddad

Student thesis: Master's Thesis


Variable Frequency Drives (VFDs) are employed in the heavy industry like oil rigs, refineries and mills etc., as they result in efficient plant operation. However, with the increased penetration of VFDs, the power quality problems have become significant. The focus in this thesis s is to study the power quality problem in the oil rigs of National Drilling Company (NDC). NDC has different types of variable speed drives in their on shore and off shore rigs. The purpose of this study is to collect field data, check the harmonic distortion and suggest other suitable solutions to improve the power quality in offshore oil rigs. Most of the old rigs are set up in 1970s and they use variable speed DC drives. The new offshore rigs use VFDs. Some these new rigs are equipped with series inductors in VFDs. Generator voltage distortion, overheating of generators, poor power factor, unwanted tripping are the common problem faced by these rigs. This thesis investigates the harmonic problems in VFDs, reduction in harmonic due to the usage of series inductance. Detailed investigation is carried out to check if the series inductance is able to reduce the harmonics to acceptable levels or not. The typical oil rig power system simulated using ETAP and necessary harmonic distortion data generated from MATLAB. It is observed that series inductor will keep the THD within acceptable limits if the generator is oversized. For better utilization of generators and harmonic mitigation other alternative solutions such as tuned passive filters are required. This study is significant for oil rigs and other industries as it will help the industry in studying the harmonic problems and mitigation techniques. The suggested solutions will help the industry in better utilization of generator and efficient operation of the plant.
Date of Award2016
Original languageAmerican English
SupervisorAbdul Rahiman Beig (Supervisor)


  • Applied sciences
  • Drilling
  • Harmonics
  • Power system
  • Rig
  • Electrical engineering
  • 0544:Electrical engineering

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