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Offshore Power Electronics

To reduce the cost and improve the reliability in offshore wind farms is a critical issue with high R&D-efforts. Offshore wind energy produced far from shore (e.g. in the North Sea), and nearly all energy produced by new renewable energy sources, will have to pass two or more power electronic converters before reaching the tie-in point to the national transmission grid. This fact, but also the presently high cost for renewable energy, highlights the need for very energy efficient conversion systems. Power electronic converters situated far from shore and possibly subsea will also require high reliability and long life time due to high costs for maintenance and repair.

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When the project application was submitted in 2008 there were several research project at SINTEF Energy Research related to offshore wind, most of them associated with NOWITECH.  However no projects had main focus on important converter basic characteristics such as reliability, efficiency and control problems related to converters interacting with complex grid systems. These are all crucial issues for offshore wind power conversion systems due to remote locations and harsh environment.

The main results from the project are summarized as follows:

Component modelling:

  • Detailed converter simulation models for testing control algorithms, component losses, thermal cycling etc.
  • Loss models with input from measurements and output to life time estimators. Mainly for IGBTs but also for inductive components (winding losses)
  • Multi-physics analysis (electric, thermal, mechanical) of IGBT stress – PhD student Tilo Poller

Laboratory equipment provided by the project and experiments:

  • High Voltage Test Cell for Measurements of IGBT temperature dependent switching losses
    for input to simulations
  • Power Cycling Tester for life-time testing of high-power IGBTs – Input to life-time prediction
  • Several PWM Voltage Source Converters in the range of 50 kW with advanced digital  control algorithms for generator side and motor side operation and currently used in the SINTEF/ NTNU Renewable Energy Systems and Smart Grid Laboratory

Case simulations:

  • Case 1 and case 2 simulations of control algorithms, loss calculation and thermal stress
  • Analysis of Converters Topologies for DC series connected wind turbines

Achievements within control strategies and algorithms:

  • Algorithm for IGBT power cycling lifetime prediction for Wind Power converters
  • Algorithms for AC side droop control, virtual synchronous machine etc.
  • Control strategies for parallel converters based on AC droop

Post Doc work by Salvatore D'Arco on topologies and control strategies completed.

Well established cooperation with TU Chemnitz on  power semiconductor reliability.

Key Factors

Project duration

2009 - 2014