Coupled Generator- and Converter-Modelling for Partly Superconducting Medium-Speed Wind Turbine Generators

Abstract:
This work presents a structured modelling and simulation workflow for a medium-speed wind power generator with a superconducting rotor winding and its corresponding power converter. By considering the generator and converter as a coupled drivetrain system, the approach optimizes energy efficiency, material usage, and enables larger wind turbines within existing installation constraints. The effects of the power converter feeding of the normal-conducting stator winding are highly relevant for partly superconducting generators: Even minor additional power dissipation in the cryogenic rotor parts can lead to significant thermal loads for the cryogenic cooling system. This work is part of a current, publicly funded project for the development of a megawatt-scale prototype by 2026. It was found that converter feeding excites additional magnetic field waves in the rotor, causing eddy current losses, which can more than double the losses in the cryogenic rotor, compared to sine current operation. This leads to an impractically large and expensive cooling system, and reduced overall efficiency of the superconducting generator. To examine mitigation measures, finite element calculations using the software JMAG 22 with pulsed voltage feeding are carried out.