In 2013 5 of NORCOWE's PhD students defended their theses successfully.
At the University of Agder Tore Bakka defended his PhD on the 29th of November. The title was Multiobjective Optimization and Multivariable Control of Offshore Wind Turbine System, with Professor Hamid Reza Karimi as supervisor and Professor Geir Hovland as co-supervisor.
His dissertation mainly dealt with pitch control of a floating wind turbine, dealing to some extent also with modeling. Regarding the latter, he examined how the bond graph can contribute with a model and give a better understanding of how the overall system works. This is an alternative to the more classical Newtonian approach. The emphasis was here on the electro-mechanical system and not on the hydro- or aero- dynamics.
For the control of the turbine he used models obtained from the wind turbine simulation software FAST (Fatigue, Aerodynamic, Structures and Turbulence), a software developed by NREL with which NORCOWE has a Memorandum of Understanding. NORCOWE and NREL are planning a workshop on FAST in September 2014.
In his research, Tore examined several linear models of the turbine, made continuous based on an affine parameter-varying structure. He also looked at controllers where not all the available information is used (so-called constrained information). The reason for this approach is that for instance some of the sensors may be espectially prone to failure, or one may wish to switch between controllers which do not need the same information.
Tore Bakka was a visiting researcher at the University of Wisconsin-Madison in USA during the fall semester of 2012, where his host was Professor Neil A. Duffie.
Tore Bakka is now working for National Oilwell Varco.
The committe at Tore Bakka's PhD defence
At the University of Bergen Olav Krogsæter defended his Phd on the 16th of December. The title was The Marine Atmosperic Boundary Layer and Ocean Waves Under the Aspect of Offshore Wind Energy Applications. His supervisor was Professor Joachim Reuder. Olav Krogsæter is working for StormGeo, and has been working for the company during his PhD. The picture below shows Olav in 2011 at the 7th PhD seminar on Wind Energy in Europe, where he won a prize for best poster. Olav Krogsæter will present his work at the internal NORCOWE Work Package meeting in May.
The other three PhDs defended in 2013 were:
Søren Christiansen, Aalborg University: Model-based control of a ballast-stabilized floating wind turbine exposed to wind and waves (supervisor: Professor Thomas Bak)
Arunjyoti Sarkar, University of Stavanger: Offshore wind turbines supported by monopiles (supervisor: Professor Ove Tobias Gudmestad)
Erik Kostandyan, Aalborg University: Reliability modelling of wind turbines - exemplified by power converter systems as basis for O&M planning (supervisor: Professor John Dalsgaard Sørensen)