PhD student Erik Kostandyan (pictured below) is defending his thesis on the 28th of October at Aalborg University.



Under the supervision of Professor John Dalsgaard Sørensen he has worked on the reduction of Operation & Maintenance costs through reliability modeling. The title of his thesis is "Reliability modeling of wind turbines - exemplified by power converter systems as basis for O&M planning". The assessment committee consists of:

  • Professor Zhe Chen (Chairman), Department of Energy Technology, Aalborg University, Denmark
  • Professor Ivar Langen, Faculty of Science and Technology, University of Stavanger, Norway
  • Professor Dimitri Val, School of the Built Environment, Heriot-Watt University, United Kingdom

From the announcement (text Erik Kostandyan):

"Reduction of Operation & Maintenance costs of Wind Turbines will result in significant cost savings  as well as cheaper electricity production. The Operation & Maintenance processes mainly involve actions related to replacements and/or repair. Identifying the right times when the actions should be made and the type of actions requires knowledge on the accumulated damage or degradation state of the wind turbine components. For offshore wind turbines, the action times could be delayed due to weather restrictions and result in damage or degradation increase of the remaining components. Thus, reliability models should be developed and applied in order to quantify the residual life of the components. Damage models based on physics of failure combined with stochastic models describing the uncertain parameters are imperative for development of cost-optimal decision tools for Operation & Maintenance planning, and these procedures are implemented in this research.



This research is focused on reliability modeling of Wind Turbine critical subsystems such as the power converter system, specifically developing reliability models for electrical subsystem and its components. The developed models are aimed for Operation & Maintenance strategy development and could be integrated with non-destructive evolution techniques (e.g. remotely obtaining information on fatigue measure evolution without damaging the component).  Further, reliability of structural comments is considered by taking into account possible fault events due to the grid loss resulting from the converter system failure. Such situations are quite common and have vital importance, especially for pitched controlled off-shore Wind Turbines. For a representative structural failure mode, a probabilistic model is developed that incorporates grid loss failures. Also, advancing the topic of dependent / load sharing system reliability estimation, a theoretical background is developed based on sequential order statistics and structural systems reliability methods.

Procedures for reliability estimation on the above-mentioned are detailed and presented in a collection of peer reviewed research papers."


The PhD Defence is open to the public.

Address: Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg East

Phone: 0045 9940 8484



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