High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and costeffective direct-drive (DD) trains for large wind turbines. This paper reports the designing and basic experimental validation of the world's first full-scale DD HTS generator demonstrated on a commercial wind turbine. The HTS generator has its rotor with an HTS field winding working below 30 K, which is achieved by using off-the-shelf Gifford-McMahon cryocoolers. The stator of the generator is essentially conventional, except that the armature winding has four segments to limit fault torques in case of sudden short circuits due to converter failures. Compared to an existing DD permanent magnet generator on the turbine, the air gap shearing stress of the HTS generator is doubled, and the weight is reduced by 24%. The overall design requirements from the turbine integration perspective, as well as the topological considerations, are first described in this paper. The electromagnetic and cryogenic designs are then presented, followed by performance testing of HTS coils. The basic experimental validation shows that the cryogenic design
The EU-funded EcoSwing project addresses the world's first full-scale direct-drive (DD) high temperature superconducting (HTS) wind turbine generator. Before the generator was installed on a commercial wind turbine, the generator had been tested on the ground at the Dynamic Nacelle Testing Laboratory (DyNaLab) in Fraunhofer Institute for Wind Energy Systems (IWES), serving as an experimental validation of the generator design. This article is centered on the ground testing of the EcoSwing HTS generator, which includes corresponding tests for validating the generator's cryogenic design and electromagnetic performance. Despite one HTS coil with a defect limiting the operating current significantly, partial power production up to 1 MW at 14.5 rpm was reached. The critical auxiliary systems, i.e., vacuum system and rotary helium coupling, behaved as expected or even better than anticipated. The work reported in the article successfully validates the generator design, and also provides firsthand information prior to installing and testing the HTS generator on the wind turbine.
High temperature superconducting (HTS) generators could enable a lightweight and cost-effective direct drive (DD) wind turbines with large power ratings. The EU-funded EcoSwing project successfully demonstrated the world's first full-scale MWclass HTS generator on a commercial DD wind turbine. This paper focuses on the commissioning of the EcoSwing HTS generator on the wind turbine. The commissioning campaigns, including the rotor cool-down, excitation of the HTS field winding, and the power production of the generator, are presented in the paper. In the testing period, the generator was grid-connected for more than 650 hours and accumulatively produced more than 600 MWh to the grid. The target output power of the 3 MW class was reached. Throughout the real-life testing on the wind turbine, the generator performed well from the electromagnetic, thermal, and mechanical perspectives. Moreover, the generator even sustained three sudden short circuits in the converter system. The work reported has shown that HTS generators are technologically feasible for wind turbine applications, and the technology readiness level of HTS Manuscript
Using large components made of nodular cast iron (GJS) in wind turbines enables the application of lightweight construction through the high degree of design freedom. Besides the sand-casting process, casting into a permanent metal mould, i.e. chill casting, leads to a finer microstructure and higher quasi-static mechanical properties as well as higher fatigue strength. Unfortunately, in present design methodologies specific fatigue data is only available for sand cast and not for chilled cast GJS. Thus, lightweight design strategies for large, chilled cast components are not achievable, which led to the publicly funded project “Gusswelle”. Based on material investigations of EN-GJS-400-18-LT chill cast, an optimized hollow rotor shaft is developed. The design process and the resulting shaft design are presented. The optimized hollow rotor shaft prototype will be tested on a full-scale test bench to validate the design methodology. The intended validation plan as well as the test bench setup is shown in this paper. Furthermore, the decreasing wall thickness influences the interference fit between main bearing and hollow rotor shaft. Thus, through the applied bending moment, inner ring creep is more probable to occur in the main bearing seat. The creeping behaviour is investigated with finite element simulations and a measuring method is presented.
Modern wind turbines have a driving torque in the range of up to 10 MNm. The measurement of such high torques poses challenges, as there is no standard measurement equipment for this torque level available today. During the EU funded EcoSwing project, the world’s first superconducting low-cost and lightweight multi-megawatt wind turbine generator has been designed and tested on the DyNaLab nacelle test rig of Fraunhofer IWES. For this test campaign, a specifically designed torque measurement system has been developed to measure the torque directly at the flange of the device under test in order to evaluate the efficiency of the power train.
Spheroidal graphite cast iron (EN-GJS), which provides a high degree of design flexibility and the possibility for lightweight design, has benefits as a material for use in structural parts in wind turbines. Comparing components made using the sand casting technique to those made using the chill casting process reveals significant potential to boost strength. However, at present, there is neither a proven design guideline nor reliable material input data for a lightweight component based on this material and fabrication process. This publication presents the results from the Gusswelleproject in chronological order. It starts with the explanation of the final setup and test plan for the full-scale rotor shaft fatigue experiment. The elaborated sensor and operational concept are then presented together with an adequate finite element method (FEM) model of the specimen and relevant neighboring components. The validation of this FEM model to ensure that the loading and the resulting local strains representing the real test bench situation is described. The usage of non-destructive testing to document the condition of the specimen from initial crack formation until integrity loss is explained followed by a comparison between the component fatigue test results and the material-based life-time forecast. A strength increase for chill-cast large components in the range of 50% is indicated. Simulation-based crack propagation studies are performed to qualitatively verify the loads responsible for the observed cracks of the component test and to further develop the possible method for crack predictions.
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