Real Time Simulation of Wind Turbines for HiL Testing with MoWiT

Full Nacelle Ground Testing is becoming increasingly important during the certification and validation process of modern multi-megawatt wind turbines. Despite the utilization of modern simulation methods, experimental hardware tests with real components are still essential. In order to reduce the vast efforts associated with full component testing, a combination of simulation models and specific testing facilities for individual components can be employed in a hardware-in-the-loop (HiL) environment. The Dynamic Nacelle Testing Laboratory DyNaLab at Fraunhofer IWES allows for realistic emulation of both (mechanical) rotor and (electrical) grid loads for the full component test of wind turbine power trains. For most realistic loading scenarios during testing, a virtual rotor model with turbulent 3D wind inflow can be simulated in real time and coupled with the test rig in an HiL environment. The Modelica for Wind Turbines Library MoWiT developed at Fraunhofer IWES includes all major components necessary for load calculations of state of the art onshore and offshore wind turbines. MoWiT serves as the virtual rotor model for such HiL-tests. The realistic wind turbine models are simulated on an Opal-RT real-time simulator to obtain optimal I/O interfacing possibilities while maintaining strict real-time requirements. In an ongoing research project, the MoWiT rotor model or the full wind turbine simulation model will be coupled with the IWES DyNaLab test rig.

The document describes the setup of the software and hardware tool chain to achieve this goal as well as the implications to the aero-elastic model that come along with the requirement of strict real time conditions with a desired sampling rate of 200Hz. It is necessary to reduce the complexity of a high fidelity aero-elastic wind turbine model in MoWiT as it would be used for load calculations to increase simulation speed. At the same time, it is desired to maintain the nonlinear dynamic behaviour of the wind turbine model with appropriate accuracy compared to the high fidelity aero-elastic model. An approach for such a model reduction while sustaining the fully-coupled aero-elastic behaviour is presented. The results from the reduced order, real time simulation model are compared with the high fidelity offline simulation model to evaluate the effect of model reduction and show the real time capability of MoWiT.