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

Abstract

This article presents a method for performing Real-Time Hybrid Model testing (ReaTHM testing) of a floating wind turbine (FWT). The advantage of this method compared to the physical modelling of the wind in an ocean basin, is that it solves the Froude-Reynolds scaling conflict, which is a key issue in FWT testing. ReaTHM testing allows for more accurate testing also in transient conditions, or degraded conditions, which are not feasible yet with physical wind. The originality of the presented method lies in the fact that all aerodynamic load components of importance for the structure were identified and applied on the physical model, while in previous similar projects, only the aerodynamic thrust force was applied on the physical model. The way of applying the loads is also new. The article starts with a short review (mostly references) of ReaTHM testing when applied to other fields than marine technology. It then describes the design of the hybrid setup, its qualification, and discusses possible error sources and their quantification. The second part of the article [1] focuses on the performance of a braceless semisubmersible FWT, tested with the developed method. The third part [2] describes how the experimental data was used to calibrate a numerical model of the FWT.

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

“…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.…”

“…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].…”

“…As described in greater detail in Part I [1], the aerodynamic and generator loads were calculated using AeroDyn and the "Bladed-style" DISCON controller defined for the OC3 study, with some modifications for cases where blade pitch fault or shutdown are to be included. The aerodynamic calculations are carried out in full scale, with the measured positions, orientations, and velocities, as well as the applied loads, scaled according to Froude scaling.…”

“…The test method is documented in Part I [1], while this work provides details of the test set-up and presents some of the interesting findings from the model test campaign. Calibration of a numerical model of the floating wind turbine is described in Part III [15].…”

“…When the experimental goal is to qualify the global performance of the system, a so-called "realtime hybrid model testing" approach may be applied: in the case of the FWT in the wave basin, this implies that the aerodynamic forces are actuated upon the physical model according to simultaneous (real-time) simulations of the turbine rather than being generated by a small-scale physical turbine [1,[12][13][14]. Real-time hybrid model testing will be referred to as ReaTHM TM testing (a trademark of MARINTEK) in the following.…”