Electrical Grid Study of Using Offshore Wind Power for Oil & Gas Offshore Installations
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The purpose of this thesis is to investigate the performance of a wind integrated oil & gas offshore installation. The motivation behind this is to reduce emissions of CO2 and other greenhouse gases from offshore installations that utilize natural gas turbines. A model of the wind integrated oil & gas installation is built and implemented in Matlab/Simulink. The simulations are focused on investigating the performance of the system for transient contingency conditions.Two subsystems are investigated separately. The wind energy system is implemented as a 6MW direct-driven permanent magnet synchronous generator. The generator connects to the oil & gas installation by a 2-level back-to-back voltage source converter. An extensive control system allows for variable-speed operation to optimize power production. The configuration is found advantageous for use with oil & gas installations as the generator is decoupled from the platform transients by a DC-link. The oil & gas offshore installation is implemented as a 46MVA gas turbine synchronous generator, two 8MVA induction motor drives and a passive load of 16MW. The gas turbine is shown to have a fast response in handling transients, and the induction motor drive is shown to have excellent speed and torque control.The wind integrated oil & gas offshore installation combines the two subsystems through a transmission line. The complete system is simulated for both varying wind speed operation and selected contingency events. The loss of passive load is found to give the biggest voltage transient. The biggest frequency transient is seen for the loss of one of the two gas turbines. All results are compared with the transient limits found in the NORSOK/IEC standards, and found to be within the requirements. The wind turbine is allowed to produce at maximum throughout the simulations, while the gas turbine is seen to balance the system to maintain the system frequency. The conclusion of the thesis is that integration of a wind turbine with an oil & gas offshore installation is feasible within the NORSOK/IEC standards. This is true for all scenarios and contingencies tested in this thesis. The results are discussed further in the thesis, with challenges and suggested further work pointed out.