Experimental Validation of Inertia-Eigenfrequency Emulation for Wind Turbines on System Test Benches

Hardware-in-the-loop systems for wind turbine system test benches are prominently used in today’s development process of wind turbine manufacturers to conduct realistic ground-level tests. This contribution presents a state-of-the-art test rig in the multi-megawatt regime equipped with an innovative hardware-in-the-loop (HiL) system which enables ground-based testing of full scale wind turbines. The proposed system consists of a state estimator, an internal wind turbine model comprising an aeroelastic rotor model for reference generation as well as control loops for setpoint tracking and active drivetrain damping purposes. The introduced HiL system is validated experimentally in detail at a test rig with a mounted state-of-the art 3 MW full scale wind turbine. Experiments prove the system’s ability to emulate the nacelles drivetrain dynamics on ground-level while guaranteeing stable operation over the full wind speed range and in demanding instationary design load cases such as gust events. Experimental results show wind turbine related frequency shares originated in the dynamics of the physically not present rotor, e.g. per-revolution frequencies, tower shadow as well as the first torsional drivetrain eigenfrequency are induced. In addition to this, experiments in power production prove the ability of reproducing the nacelle’s power curve with a maximum error of 10 % in the transition of partial and full load operation and less than 3 % over the full operational range.