Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine: Part II — Experimental Results

Abstract

Real-Time Hybrid Model (ReaTHM) tests of a braceless semi-submersible wind turbine were carried out at MARIN-TEK's Ocean Basin in 2015. The tests sought to evaluate the performance of the floating wind turbine (FWT) structure in environmental conditions representative of the Northern North Sea. In order to do so, the tests employed a new hybrid testing method, wherein simulated aerodynamic loads were applied to the physical structure in the laboratory. The test method was found to work well, and is documented in [1].The present work describes some of the experimental results. The test results showed a high level of repeatability, and permitted accurate investigation of the coupled responses of a FWT, including unique conditions such as blade pitch faults. For example, the influence of the wind turbine controller can be seen in decay tests in pitch and surge. In regular waves, aerodynamic loads due to constant wind had little influence on the structure motions (except for the mean offsets). Tests in irregular waves with and without turbulent wind are compared directly, and the influence of the wave-frequency motions on the aerodynamic damping of wind-induced low-frequency motions can be observed.

Real-Time Hybrid Model Testing of a Braceless Semi-Submersible Wind Turbine: Part I — The Hybrid Approach

“…Transient motions of FWT, transient loads on the mooring lines and at the tower base could be studied, as well as the dynamics of the FWT in shutdown or degraded mode. Selected results of (1)-(3) are reported in detail in [1]. Even if not tested during the present test campaign, the developed methodology enables (4) testing generators and rotors from various manufacturers on the same substructure in a quite efficient way, (5) testing various control strategies for the wind turbine controller, without necessarily disclosing the details of the controller, and (6) performing detailed sensitivity studies to the wind modelling (including effect of large waves on the wind field).…”

“…ReaTHM testing has been identified as a promising technology for testing of FWTs. The review in Part II [1] provides details on this issue, its importance, and the various solutions that have been suggested by others [19,20]. Copyright c 2016 by ASME Nomenclature ReaTHM testing techniques have been developed and used in various fields, quite independently from each other.…”

“…The physical substructure included the semi-submersible of the 5-MW-CSC design [3], and the tower design described in [22]. Details regarding the geometry and mass properties of the physical substructure are given in Part II [1]. The numerical substructure included all components of the wind turbine mounted on the top of the tower.…”

“…A mesh of 28x28 elements covering a surface of 160x160m was used. Detailed properties regarding the incoming wind field are given in Part II [1]. The aerodynamic load calculations were carried out in full-scale using the open source code AeroDyn [25].…”

“…For completeness, Section 5 briefly lists the types of investigations that ReaTHM testing enables in the field of wind engineering. For a complete case study, the reader is referred to Part II [1], which shows in particular that this technique enabled accurate investigation of the coupled responses of the FWT and its controller. Unique test conditions, such as blade pitch fault situations and shutdown, could also be investigated.…”