A new modular drivetrain for large wind turbines currently under development is presented. The electromechanical drivetrain has a direct-drive configuration with a modular flux-switching permanent-magnet generator. The full-power converter consists of 12 parallel back-to-back two-level voltage source converter modules. A novel method of modulation is used to improve harmonic quality while maintaining a low switching frequency. Benefits of the new design include simplified manufacturing and transport, increased system availability due to fault tolerance and redundance, and avoidance of an LCL filter. Measurement results are shown from a 500-kW test rig.

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Among electrical machines with permanent magnets, the class of flux-switching permanent magnet machines has especially good properties with regard to mechanical robustness and cooling. It is a relatively new class of machines with only few industrial applications so far. The design of such machines is thus not well established and known publications on the topic focused on optimizing single objectives or on varying single parameters only. A systematic way to find a trade-off between multiple objectives is proposed while also considering constraints-in particular such constraints introduced by the power converter. To practically demonstrate the usefulness of multiple-objective optimization, a hypothetical redesign is performed with reference to a machine, which was originally designed and commissioned without explicit use of multiple-objective optimization. It is found that the original machine is optimal in a certain sense, but that the strength of multiple-objective optimization does not lie in finding one particular optimal solution but in visualizing trade-offs between multiple objectives/goals. The visualization reveals, for example, that 11 % magnet material could have been saved at the cost of 16 % higher copper losses at full load.

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