There is a variety of possible causes for vibrations affecting the entire wind turbine (WTG) at its lowest natural frequencies. Some typical examples are:
- Resonance due to rotor speeds and higher harmonics: When starting a WTG, a resonance is often caused or the WTG should be operated in such a way that the excitations from the rotor (1P, 2P or 3P etc.) are close to a natural frequency of the WTG.
- Excitation by periodic vortex shedding: At the tower of a wind turbine, vortices can periodically detach at certain wind speeds. Typically, this can become critical for assembled WTGs (without nacelle) or for slender WTGs with a low second natural tower bending frequency.
- Wave excitation in offshore wind turbines: Wave excitation can become critical when the first natural frequency of a wind turbine is very low, since the energy of the wave excitation is particularly high at these frequencies. The trend towards ever more powerful wind turbines at greater water depths and the maintenance of the monopile foundation concept reinforces this problem.
Depending on the wind turbine type and overall context, it is necessary to assess whether the expected vibrations are problematic and which solution is the most suitable for vibration reduction.
Absorbers are a very cost-effective and reliable solution for vibration problems. They are highly effective and, in particular, passive absorbers are extremely robust. Tailored to the specific application, we offer successful, individual absorber concepts to solve the respective problem.