Investigation of Dynamic Loads in Wind Turbine Drive Trains Due to Grid and Power Converter Faults

Röder, Julian; Jacobs, Georg; Duda, Tobias; Bosse, Dennis; Herzog, Fabian

doi:10.3390/en14248542

Cited by 13 publications

(14 citation statements)

References 8 publications

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“…In a previous investigation, the authors identified that grid faults like symmetric voltage dips and emergency shutdowns lead to TTRs. Similar observations were also made by Röder et al 11,12 as they found an increased risk of smearing during grid and converter faults. To mitigate the risk associated with TTRs, three different approaches have been investigated here and their performance evaluated for symmetrical voltage dip and emergency shutdown events in a DFIG wind turbine.…”

Section: Figuresupporting

confidence: 85%

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Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Sarkar

Johansson

Berbyuk

2023

Preprint

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Bearing failure in wind turbine gearboxes is one of the significant sources of downtime. While it is well known that bearing failures cause the largest downtime, the failure cause(s) is often elusive. The bearings are designed to satisfy their Rolling Contact Fatigue (RCF) life. However, they often undergo sudden and rapid failure within a few years of operation. It is well known that these premature failures are attributed to different types of surface damage. In that regard, transient torque reversals (TTRs) in the drivetrain have emerged as one of the primary triggers of surface damage, as explained in this paper. The risk associated with TTRs motivates the need to mitigate TTRs arising in the drivetrain due to various transient events. This paper investigates three TTR mitigation methods. First, two existing devices, namely, the torsional tuned mass damper and the asymmetric torque limiter, are studied. Then, a novel idea of open-loop high-speed shaft mechanical brake control is proposed. The results show that while the torsional tuned mass damper and the asymmetric torque limiter can improve the torsional vibration characteristics of the drivetrain, they cannot mitigate TTRs in terms of eliminating the bearing slip risk associated with TTRs. However, the novel approach proposed here can mitigate TTRs both in terms of improving the torque characteristic in the high-speed shaft and reducing the risk of bearing slip. Furthermore, the control method is capable of mitigating TTRs with the mechanical limitations of a pneumatic actuator in terms of bandwidth and initial dead time.

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Section: Figuresupporting

confidence: 85%

“…FIGURE12 Contour plots of slip risk duration with respect to HSS torque (in Nm), braking torque (in % of rated generator torque) and brake duration (in seconds).…”

mentioning

confidence: 99%

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Sarkar

Johansson

Berbyuk

2023

Preprint

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“…The load cases that lead to these situations lie outside the range of normal operation. Available industrial reports 7,20 and academic literature 21,22,23 point to the fact that transient events such as emergency shutdown and electrical faults such as grid voltage dips, power converter faults etc., in DFIG based wind turbines lead to rapid variation in electromagnetic torque that can then lead to transient torque reversals in the drivetrain shafts. The following steps are taken to investigate the phenomenon of TTRs in indirect drive wind turbines:…”

Section: Figurementioning

confidence: 99%

Transient torque reversals in indirect drive wind turbines

Sarkar

Johansson²,

Berbyuk³

et al. 2023

Preprint

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The adverse effect of transient torque reversals (TTRs) on wind turbine gearboxes can be severe due to their magnitude and rapid occurrence compared to other equipment. The primary damage is caused to the bearings as the bearing loaded zone rapidly changes its direction. Other components are also affected by TTRs (such as gear tooth); however, its impact on bearings is the largest. While the occurrence and severity of TTRs are acknowledged in the industry, there is a lack of academic literature on their initiation, propagation and the associated risk of damage. Furthermore, in the wide range of operation modes of a wind turbine, it is not known which modes can lead to TTRs. Further, the interdependence of TTRs on environmental loading like the wind is also not reported. This paper aims to address these unknowns by expanding on the understanding of TTRs using a high fidelity numerical model of an indirect drive wind turbine with a doubly-fed induction generator (DFIG). To this end, a multibody model of the drivetrain is developed in SIMPACK. The model of the drivetrain is explicitly coupled to state-of-the-art wind turbine simulator Open-FAST, and a grid-connected DFIG developed in MATLAB ® 's Simulink ® allowing a coupled analysis of the electromechanical system. A metric termed slip risk duration is proposed in this paper to quantify the risk associated with the TTRs. The paper first investigates a wide range of IEC design load cases to uncover which load cases can lead to TTRs. It was found that emergency stop and symmetric grid voltage drops can lead to TTRs. Next, the dependence of the TTRs on inflow wind parameters is investigated using a sensitivity analysis. It was found that the instantaneous wind speed at the onset of the grid fault or emergency shutdown was the most influential factor in the slip risk duration. The investigation enables the designer to predict the occurrence of TTRs and quantify the associated risk of damage. The paper concludes with recommendations for utility-scale wind turbines and directions for future research.

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“…The advantages of the DFIG concept are a partial-scale converter, which reduces cost compared to a full-scale converter, variable speed operation in a certain range and decoupled control of active and reactive power [2]. Low Voltage Ride Through (LVRT) tests introduce highly dynamic electrical and mechanical loads to wind turbine systems [3], [4]. These tests are part of the certification process for the electrical properties of wind turbines.…”

Section: Introductionmentioning

confidence: 99%

Influences on the LVRT behavior of DFIG wind turbine systems

Herzog

Röder

Frehn

et al. 2022

J. Phys.: Conf. Ser.

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Grid faults introduce highly dynamic electrical and mechanical loads to a wind turbine (WT). Especially WTs with a direct grid connection like the doubly-fed induction generator (DFIG) are strongly affected. The behavior of a WT during grid faults can be tested in low voltage ride through tests (LVRT). But there are numerous influencing factors on the behavior of the DFIG during a LVRT which have not yet been fully investigated. The pre-fault operating point of the DFIG, the grid inductance, the pre-fault phase angle of the grid voltage, the fall time of the voltage as well as the start and end values of the voltage drop affect the electromagnetic torque and the short circuit current of the generator. Therefore, many LVRT test results for DFIGs are neither comparable nor representative. In this paper it is shown that the peaks of electromagnetic torque and currents during LVRTs can be reduced. A low pre-fault torque and rotational speed, a high grid inductance and a slow voltage drop can minimize the impact of a grid fault. The rotational speed is especially critical because it influences the slip of the DFIG and, thus, has an influence on the dynamics of the fault.

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Investigation of Dynamic Loads in Wind Turbine Drive Trains Due to Grid and Power Converter Faults

Cited by 13 publications

References 8 publications

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

Transient torque reversals in indirect drive wind turbines

Influences on the LVRT behavior of DFIG wind turbine systems

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