Jauch, C. . (2021). Grid Services and Stress Reduction with a Flywheel in the Rotor of a Wind Turbine. Energies, 14. http://doi.org/10.3390/en14092556
Abstract
Wind power penetration increases in most grids and the sizes of wind turbines increase. This leads to increasingly tough requirements, which are imposed on wind turbines, both from the grid as well as from economics. Some of these partially contradictory requirements can only be satisfied with additional control mechanisms in the wind turbines. In this paper, such a mechanism, i.e., a hydraulic–pneumatic flywheel system in the rotor of a wind turbine, is discussed. This flywheel system supports a wind turbine in providing grid services such as steadying the power infeed, fast frequency response, continuous inertia provision, power system stabilization, and low voltage ride-through. In addition, it can help mitigate the stress on the mechanical structure of a wind turbine, which results from varying operating points, imbalances in the rotor, gravitation that acts on the blades, in-plane vibrations, and emergency braking. The study presented in this paper is based on simulations of a publicly available reference wind turbine. Both the rotor blade design as well as the design of the flywheel system are as previously published. It is discussed how the aforementioned grid services and the stress reduction mechanisms can be combined. Finally, it is concluded that such a flywheel system broadens the range of control mechanisms of a wind turbine substantially, which is beneficial for the grid as well as for the wind turbine itself.
Gloe, A. ., Jauch, C. ., & Räther, T. . (2021). Grid Support with Wind Turbines: The Case of the 2019 Blackout in Flensburg. Energies, 14(6), 1697. http://doi.org/10.3390/en14061697
Abstract
The work presented in this paper aims to show how modern wind turbines can help to control the frequency in a small grid which suffers from large power imbalances. It is shown for an exemplary situation, which occurred in Flensburg’s distribution grid in 2019: a major blackout, which occurred after almost two hours in islanding operation, affecting almost the entire distribution grid, which supplies approximately 55,000 households and businesses. For the analysis, a wind turbine model and a grid support controller developed at the Wind Energy Technology Institute are combined with real measurements from the day of the blackout to generate a fictional yet realistic case study for such an islanding situation. For this case study, it is assumed that wind turbines with grid support functionalities are connected to the medium voltage distribution grid of the city. It is shown to what extent wind turbines can help to operate the grid by providing grid frequency support in two ways: By supplying synthetic inertia only, where the wind turbines can help to limit the rate of change of frequency in the islanded grid directly after losing the connection to the central European grid. In combination with the primary frequency control capabilities of the wind turbines (WTs), the disconnection of one gen set in the local power station might have been avoided. Furthermore, wind turbines with primary frequency control capabilities could have restored the grid frequency to 50 Hz shortly after the islanding situation even if the aforementioned gen-set was lost. This would have allowed connecting a backup medium voltage line to the central European grid and thereby avoiding the blackout.
Thiesen, H. ., & Jauch, C. . (2020). Determining the Load Inertia Contribution from Different Power Consumer Groups. Energies, 13(7). http://doi.org/10.3390/en13071588 (Original work published April 2020)
Abstract
Power system inertia is a vital part of power system stability. The inertia response within the first seconds after a power imbalance reduces the velocity of which the grid frequency changes. At present, large shares of power system inertia are provided by synchronously rotating masses of conventional power plants. A minor part of power system inertia is supplied by power consumers. The energy system transformation results in an overall decreasing amount of power system inertia. Hence, inertia has to be provided synthetically in future power systems. In depth knowledge about the amount of inertia provided by power consumers is very important for a future application of units supplying synthetic inertia. It strongly promotes the technical efficiency and cost effective application. A blackout in the city of Flensburg allows for a detailed research on the inertia contribution from power consumers. Therefore, power consumer categories are introduced and the inertia contribution is calculated for each category. Overall, the inertia constant for different power consumers is in the range of 0.09 to 4.24 s if inertia constant calculations are based on the power demand. If inertia constant calculations are based on the apparent generator power, the load inertia constant is in the range of 0.01 to 0.19 s.
Alhrshy, L. ., Jauch, C. ., & Kloft, P. . (2020). Development of a Flexible Lightweight Hydraulic-Pneumatic Flywheel System for Wind Turbine Rotors. Fluids, 5. http://doi.org/10.3390/fluids5040162
Abstract
In this paper, the design of a flexible piston accumulator for application in a hydraulic-pneumatic flywheel system in a wind turbine rotor is presented. The flywheel system enables a wind turbine to vary the inertia of its rotor blades to control the power output and, most importantly, to influence the vibratory behaviour of wind turbine components. The method used for designing the flexible accumulator is based on the one hand on test results of a flexible piston accumulator prototype, and on the other hand, on simulation results of a model of a flexible piston accumulator. As a result, a design of flexible piston accumulators for application in the flywheel system is implemented and compared with the design of conventional steel accumulators. Due to the proposed design of the flywheel system, the impact on the mechanical loads of a wind turbine is analysed. The simulation results show that the new design of the piston accumulators causes a lower impact on the mechanical loads of the wind turbine than a previously published design of piston accumulators. It is further shown that the considered wind turbine can take on the flywheel system without the need for reinforcements in the rotor blades.
Jauch, C. ., Alhrshy, L. ., & Kloft, P. . (2019). Flexible hydropneumatische Kolbenspeicher aus kohlefaserverstärktem Kunststoff zum Einsatz in Rotorblätter von Windenergieanlagen. Ingenieurspiegel , 4, 3. (Original work published November 2019)
Gloe, A. ., Jauch, C. ., & Räther, T. . (2019). Störfall im Flensburger Stromnetz – wie Windenergieanlagen den Blackout möglicherweise hätten verhindern können. Ingenieurspiegel , 4, 3. (Original work published November 2019)
Jauch, C. ., Rohr, A. ., Gloe, A. ., Thiemke, M. ., & Wilhelm, J. E. (2019). Ein Windenergieanlagenemulator zum Test von Leistungseinspeisung im Netz. Ingenieurspiegel , 4, 4. (Original work published November 2019)
Jauch, C. ., & Rohr, A. . (2019). Large Scale Test Bench for Emulating Grid Connected Wind Turbines of Different Sizes. IEEE CPE-POWERENG 2019, 13th International Conference on Compatibility, Power Electronics and Power Engineering. (Original work published April 2019)
Thiesen, H. ., & Jauch, C. . (2019). Identifying electromagnetic illusions in grid frequency measurements for synthetic inertia provision. IEEE CPE-POWERENG 2019, 13th International Conference on Compatibility, Power Electronics and Power Engineering. (Original work published April 2019)