Structural Vibration Suppression of Wind Turbine Based on Dynamic Vibration Absorption

The vibration of wind turbine towers is a critical issue affecting the reliability and safety of wind turbines. Tuned mass dampers (TMD) have been widely used to reduce the vibration of structures. In this study, the finite element simulation method is used to investigate the tower structure’s response to vibration with and without TMD at different placement positions. The results show that under fluctuating wind loads, the vibration displacement and acceleration in the downwind surface of the tower are larger than those in the windward surface. After installing TMD, the damping effect of the wind power tower can be effectively improved. Under the condition that the total mass ratio is constant, the arrangement of placing a single TMD at the top of the tower is changed to a distributed arrangement at the top and the flange. The placement position of TMD affects the vibration reduction effect and the reliability of the tower structure. A distributed arrangement of TMD can improve the reliability of the tower structure and reduce the space occupied by a single TMD.


Introduction
With the energy crisis and environmental deterioration becoming more and more pressing, the importance of wind energy has become more prominent than ever before.By the end of 2021, the total installed capacity of wind power in China has reached 328.5 GW, which represents 13.8% of the country's total installed capacity.Wind power generation accounts for 8.04% of the country's power generation, becoming the third largest power source in China.With the continuous growth of wind turbine unit capacity, wind wheel diameter, and tower height, the vibration problem of wind turbines under pulsating load is more serious.When the external wind load changes sharply, it will cause severe vibration of the tower, and could even result in the wind turbine collapsing.In addition, excessive tower vibration can worsen the fatigue effect on the structure and accelerate damage to the bolt at the root flange, creating a potential risk for collapse accidents [1][2] .
Aiming at the passive control of wind turbine tower vibration, both domestic and international scholars have conducted extensive research.STEWART and LACKNER [3] established a dynamic model of offshore wind power and analyzed the influence of wind and wave loads on the vibration reduction effect of dynamic vibration absorbers.Li et al. [4] established a finite element model that accounted for the coupling effect of the top concentrated mass and the blade tower, and separately calculated the natural vibration characteristics of the tower when subjected to the bidirectional tuned mass damper.The results show that the device has a good vibration reduction effect.Tian et al. [5] proposed a frequency-adjustable two-way sliding rail-tuned mass damper and verified the effectiveness of the device by making a scale model of the tower and damper.Chen et al. [6] proposed a basin-type tuned particle damper based on dynamic vibration absorption technology and proved that the damper can also exert an excellent vibration reduction effect in the case of a small mass ratio.The influence of mass and damping ratio of TMD on the vibration reduction effect is studied on the platform of a barge offshore wind turbine [7] .In summary, the research on tower vibration control based on dynamic vibration absorption technology is mostly based on blade-tower-damper coupling model establishment, damper form design, and parameter optimization, without considering the influence of dynamic vibration absorber placement on wind power tower vibration control.In this paper, the finite element analysis method is used to establish a solid model of a wind power tower including blade-cabin particle coupling, and the simulation of the tower's response to wind-induced vibration is conducted while subjected to fluctuating wind loads.The analysis focuses on the effectiveness of TMD in reducing vibration, with consideration of different placement positions.

Three-dimensional solid model
A 3 MW land-based wind turbine model is utilized for analysis, with a cut-in wind speed of 4 m/s and a cut-out wind speed of 25 m/s.The main structural material of the tower is low carbon alloy steel (S355), with four sections that are hoisted on-site in sequence and connected by high-strength bolts between adjacent sections.The first section of the tower is embedded in the foundation, 0.55 meters above the surface.The second section is 19.21 meters long, and the third and fourth sections are 29 meters long.The wall thickness of each section changes along the height.The nacelle, transmission chain system, and blade were simplified as lumped mass during the modeling process.Tables 1 and 2 show the correlation between the wind turbine's structural parameters, tower height, and wall thickness [8] .Based on the above data, the solid model of the wind turbine is created.Figure 1 shows the schematic diagram of the solid model.

Synthesis of wind load and design of dynamic vibration absorber
The instantaneous wind speed is a combination of the fluctuating and the average wind speed.The average wind speed depends on the height of the ground.In this study, the average wind speed is modeled using an exponential function.Figure 3 illustrates the wind load on the tower.The structural mechanics model after installing the dynamic vibration absorber is shown in Figure 4.
Figure 4 The structural mechanics model of TMD The governing equations of the model are as follows [9] : Based on the equation provided, a vibration control scheme is designed as outlined in Table 3.The placement of the Tuned Mass Damper (TMD) is illustrated in Figure 5.  Referring to Figure 6, it is evident that scheme 1 exhibits the poorest vibration reduction effect, while scheme 2 shows a slightly better effect than scheme 3.All three schemes resulted in a decrease in root mean square displacement compared to the state without control, with reductions of 14.1%, 37.6%, and 29.4% for schemes 1 to 3 respectively.The placement of TMD has a notable impact on both the vibration reduction effect and the structural reliability of the tower.Considering the vibration reduction effect, a distributed and multiple arrangement of TMD can enhance the reliability of the tower structure and reduce the space required for each individual TMD, provided that the total mass ratio remains constant.

Conclusion
This study is centered on the tower structure of a 3 WM wind turbine.A finite element grid model is established, and three power shock absorber layout schemes are designed using the modal analysis method.The study then analyzes the tower vibration control effect of power shock absorbers under different configurations.The results indicate that, with the total mass ratio of TMD held constant, a distributed arrangement with multiple TMDs can significantly improve the overall effectiveness of controlling wind-induced vibration response in the tower.

Figure 1
Figure 1 Finite element model of the wind turbine tower2.2Analysis of the tower structure's modesFigure2shows the results of the modal analysis conducted on the solid model.The results depicted in Figure2reveal that the tower exhibits distinct vibration patterns under different modes.Specifically, the first-order vibration displacement shows a maximum point at the top of the windward side of the tower, while the second mode exhibits a maximum vibration displacement near flange 3. The third-order vibration mode, on the other hand, shows a maximum vibration displacement below the top of the tower and below flange 3.

Figure 2
Figure 2 Wind turbine tower mode 3 Wind vibration response calculation of wind power tower

4 Figure3
Figure3 Time history curve of fluctuating wind load

Figure 5 Figure 6
Figure 5 The placement position of TMDs

Table 1
Tower structure parameters

Table 3
Design parameters of the dynamic vibration absorber