Simulative investigation of wind turbine gearbox loads during power converter fault

Abstract

Three phase short circuit power converter faults in wind turbines (WT) result in highly dynamic generator torque reversals, which lead to load reversals within the drivetrain. Dynamic load reversals in combination with changing rotational speeds are, for example, critical for smearing within roller bearings. Therefore, an investigation of the correlation between three phase short circuit converter faults and drivetrain component failures is necessary.Due to the risk of damage and the resulting costs, it is not economically feasible to extensively investigate three phase short circuit converter faults on test benches. Valid WT drivetrain models can be used instead. A WT drivetrain model, which has been developed and validated in a national project at the CWD, is used and a three phase short circuit converter fault is implemented. In this paper, the resulting torque load on the drivetrain for a three phase short circuit converter fault in rated power production is presented. This converter fault leads to a highly dynamic reversing electromagnetic torque which exceeds the rated torque by a factor of three. As a result the load on the rotor side high speed shaft (HSS) bearing oscillates and increases by around 15 per cent compared to rated power production. Simultaneously the rotational velocity of the HSS oscillates with an amplitude of 10 rpm. Therefore an increase in the risk of smearing is expected.

Mitigation of transient torque reversals in indirect drive wind turbine drivetrains

“…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.…”

“…FIGURE11 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).…”

Reduction of gearbox loads of a DFIG wind turbine during grid faults with optimized converter configurations

“…The dynamic generator torque excitations are transferred to the gearbox via the HSS. The resulting dynamic load changes in combination with fast changing rotational speeds can increase the risk of damage in the gearbox [3,4,5]. Gearbox damage is one driver for WT downtimes.…”

Investigation of a converter fault for a DFIG wind turbine and analysis of the resulting gearbox component loads

“…For WTs with doubly fed induction generator (DFIG) with a partial scale power converter (PSC) grid faults are transmitted directly to the generator which results in dynamic torque excitations with amplitudes significantly higher than the rated torque [3,4]. Furthermore, power converter faults can lead to highly dynamic torque excitations [5,6]. These dynamic torque excitations lead to a dynamic loading of the drivetrain components which may result in an increase in the risk of damage to the gearbox components [5].…”

“…Furthermore, power converter faults can lead to highly dynamic torque excitations [5,6]. These dynamic torque excitations lead to a dynamic loading of the drivetrain components which may result in an increase in the risk of damage to the gearbox components [5]. Damages to the gearbox are the main driver for WT downtime due to the high time to repair the fault.…”