D211 実風況下における水平軸風力発電システムの実験的研究(OS2 再生可能エネルギー(風力設備の被害と最適化))

Key challenges and prospects for large wind turbines

Advanced control of large-scale wind turbines: Structural load reduction and lifetime control

Presently, wind energy is one of the fastest growing sources in the world. The increase in the size of wind turbines can have significant benefits. By having wind turbines of large capacities, it is possible to reduce the total number of wind turbines needed to produce the same amount of power. Large wind turbines are not suitable for onshore due to transportation and installation limits which is enabled in offshore. Furthermore, floating offshore wind turbine projects have fewer turbines to transport, install and service compared to onshore. University of Ulsan (UOU) has proposed a concept of 12-MW wind turbine. It is now extended to the floating type, where the support structure is scaled up from OC4 semi-submersible platform. This paper aims to design a suitable station-keeping system which is a studless chain catenary mooring system. An in-house code computes suitable positions for anchors and the nominal diameter of mooring chains. The station keeping system is coupled analyzed with the 12 MW floating wind turbine by NREL FAST code. Considering 50 years return period environmental conditions and 20 years operation of wind turbine system, long-term prediction of extreme load of mooring lines are obtained.

Rapid growth in wind generation is accompanied with increasingly large wind turbine sizes. While the large rotor size of utility-scale wind turbines can deliver greater economic benefits, the challenges associated with control system development can get significantly amplified with increases in turbine rotor spans. The aim of this paper is to identify and quantify the trade-offs involved with controlling various conflicting control objectives, such as power output maximisation and mitigation of blade and tower loading, in utility-scale wind turbines. In order to do this, first a comprehensive high-fidelity simulation model of a 6 MW wind turbine is developed. This is followed by the development of a series of rule-based, conventional PI and modern LQR controllers. Each of the controllers is designed separately for various control objectives, both independently and as combinations of control objectives. The controllers are validated on high-fidelity wind turbine model under realistic wind and turbulence conditions. A grading scheme is proposed to score the performance of each controller in meeting control objectives when the wind turbine is operated in a range of wind conditions. As a result, the overall performance of various control methods and the computational cost considerations for the control systems development in large utility-scale wind turbines are established.

To enhance effectiveness and efficiency of wind power generation, size of wind turbine and the height of the tower have been enlarged. Recently, many researches to develop generating systems combined with wind energy and other renewable energies are being conducted. In this study, section design of tower structure supporting a wind turbine and two tidal turbines was suggested by applying a DSCT structure. An automatic design tool for DSCT columns, AutoDSCT program was used to generate new bottom sections of the tower with different hollow ratios and thicknesses of each tube. The DSCT towers with suggested design sections were carried out with moment resisting performance evaluation through nonlinear analysis in CoWiTA program.

Wind turbines are operating under very complex and uncontrolled environmental conditions, including atmospheric turbulence, atmospheric boundary layer effects, directional and spatial variations in wind shear, etc. Over the past decades, the size of a commercial wind turbine has increased considerably. All the complex and uncontrolled conditions mentioned above result in uncertainties of aerodynamic loads calculation on very large wind turbine blades and thus better numerical codes are needed for predicting the loads in the design phase. With the aim to eliminate these uncontrolled effects and improve the aerodynamic models, in last decades, several important experimental campaigns of different wind turbine models have been performed in large wind tunnels. The objective of such experiments (e.g. using the NREL wind turbine and the MEXICO rotor) is to provide high quality measurement data which can be used to validate numerical models and improve different fidelity numerical codes, particularly for predicting wind turbine aerodynamic loads.

Extensive model validation for generic IEC 61400-27-1 wind turbine models

Performance evaluation of full-scale tuned liquid dampers (TLDs) for vibration control of large wind turbines using real-time hybrid testing

SummaryWind energy has shown a remarkable potential for fulfilling the increasing world's energy demand in a clean and sustainable way. The wind energy industry has installed increasingly sophisticated and larger wind turbines particularly in offshore regions to capture such energy as efficiently and cost effectively as possible. The rapid growth in size and capacity of wind turbines together with harsh climate conditions and limited accessibility in offshore regions all result in higher failure rates and increased maintenance requirements and costs. Such difficulties motivate the use of advanced fault detection and diagnosis and fault‐tolerant control schemes in wind farms to improve their reliability and availability. Given the importance of this issue, this paper uses a fuzzy model reference adaptive control approach in a cooperative framework that is oriented to the design and development of a novel fault‐tolerant cooperative control scheme in a wind farm. This scheme handles decreased power generation faults in a wind farm caused by turbine blade erosion and debris buildup on the blades over time. The effectiveness and performance of the proposed scheme is demonstrated by a series of simulations on an advanced large offshore wind farm benchmark model in the presence of wind turbulence, measurement noise, load variations, and realistic fault scenarios.

This paper proposes a wind turbine simulator (WTS) equipped with real-time monitoring and a user-friendly parameter setup controlled by a C2000 microcontroller. This simulator consists of a 5-hp separate-excited DC motor, SIMOREG DC-Converter, which can provide the demanding torque precisely, for researching and developing wind turbine generator systems instead of using actual wind turbines. A grid-connected asymmetrical two-phase induction generator is used to test the operation of the wind turbine simulator. The experimental results confirm that the simulator provides the characteristics like an actual wind turbine. The proposed wind turbine simulator offers flexibility for analyzing the performance of the generator system for an energy conversion system under various operating conditions.

Wind turbines located near radar installations can significantly interfere with a radar's ability to detect its intended targets. In order to better understand and mitigate the adverse effects of wind turbines on radar, the government and wind farm community need tools that can be used to analyze the radar returns from wind turbines. Remcom's XGtd® software is a high frequency solver capable of calculating the radar cross section of electrically large objects. In this paper, interference from wind turbines is predicted using XGtd simulations and new post-processing algorithms that calculate Doppler shift quantities based on points of interaction with the rotating turbine blades. Results of the analysis are used to calculate the bistatic radar cross section and Doppler shift from two blade orientations. In addition, the time-varying monostatic radar cross section and Doppler shift for a single wind turbine are analyzed and shown to agree well with measured data from actual wind turbines.

For performance improvement of cross-flow wind turbine for small size wind power generation, a casing (Dual Flow Deflector Casing) with two flow deflector plates and tail plate was devised. The two flow deflector plates are to improve ambient wind environment of the wind turbine and the tail plate is for attitude control of the casing to face toward the wind. In this preliminary study, to investigate the effect of size of wind turbine, by using two types of small size wind turbine test models with different diameters (114 mm and 171mm respectively), The performance tests of these wind turbines with/without the casing were done. As a result, each size of wind turbine with the casing showed higher performance than that without the casing.

Offshore wind energy has received a lot of interest as one important renewable energy source. One promising way to reduce the Levelized Cost of Electricity (LCOE) of offshore wind energy is by developing large wind farms and turbines with large ratings. The average wind turbine size has reached 4.2 MW in 2015 and turbine sizes of 6-8 MW have already been seen in the wind market. Even larger turbine sizes are managing to pave their way from studies to market. The trend towards larger ratings and more offshore installations asks for innovations in power generation, which requires lower weight and cost, smaller size, higher efficiency and reliability. Due to the high current-carrying capability and no DC losses of the superconductors, superior power to weight/volume ratio with high efficiency of a superconducting generator can be achived. Moreover, direct current (DC) transmission has been put forward for the offshore wind farms mainly due to the overall economic benefit, as they are located far away from the land. Hence, this thesis introduces a DC generation and transmission scheme which consists of superconducting DC wind generators and superconducting DC cables as a possible technical solution. This enables a highly efficient and compact generator and in addition a new and also very efficient generator connection scheme at DC. The work presented in the thesis focuses on the feasibility study and design of a superconducting DC wind generator. In part, an optimisation method will be developed by taking superconducting tape length (cost), mass, volume, and efficiency into a simplified objective function. All necessary analytical equations will be derived to connect the electromagnetic design and mechanical design with properties of the superconducting tapes and iron materials. To increase the design accuracy, analytical equations to calculate flux density distribution in the superconducting DC generator will be verified by finite element analysis. Not only the active parts but also inactive structural materials will be included in the mass calculation. Based on the design method, the design of a 10 kW superconducting DC generator demonstrator will be described. The losses of the demonstrator and its commutation, torque and efficiency at different wind speeds will be addressed. As first steps towards the demonstrator, properties of key components, superconducting tapes, iron materials and a superconducting coil, will be tested and characterized. Moreover, a preliminary test of a superconducting coil at 77 K will be completed. In order to identify the potientials that a large scale superconducting DC wind generator could offer, a 10 MW superconducting DC generator will be designed and a comparison with conventional synchronous generators will be made. Additionally, this work will also discuss the savings of HTS tapes by optimizing outer rotor diameter, pole pair number, and superconducting coil height, which contribute to a more competitive alternative to conventional generators.

Wind power plants may need to be modeled as aggregate models for power system studies. The aggregation is typically done by scaling up the relevant wind power plant components, and representing the wind power plant collection network either by equivalent parameters or omitting the collection network representation. The collection network representation in an aggregate wind power plant model has influence on the precision of wind power plant internal power losses and reactive power feed. The equivalent collection network parameters in an aggregate model provide accurate results for active and reactive power in the case of identical operation of the wind turbines. This paper analyses the aggregate model collection network representation accuracy and related errors of different wind power plant topologies and wind power plant operating states in the case of un-identical operation of wind turbines. Different wind turbine sizes, wind turbine spacing, and collection network voltage levels are considered.

Background: During the whole life cycle of an offshore wind farm, from cradle to grave, logistics is needed. Particularly during wind turbine construction, vessels are intensively used. However, no study has been found to evaluate logistics costs during this particular turbine construction phase. Objective: In order to close this gap, this paper aims to propose an Offshore Logistics Cost (OLC) framework, evaluate OLC impact on total cost and identify recommendations to reduce this impact. Methodology: This study considers two quantitative approaches to evaluate OLC share. First quantitative approach is based on cost information found in twenty related studies from literature. Second quantitative approach was developed in two steps. A first step is a bottom up calculation model. This model performs OLC calculations for each scenario identified. In a second step, OLC results are used as input to two existing calculation models: National Renewable Energy Laboratory (NREL) simplified model and commonly accepted model developed by Megavind. Variance of results are then analyzed to determine a representative range for OLC impact on total cost. Results: Using some related values from literature review, this study assesses wind turbine construction offshore logistics to represent around 1.2% of Levelized Cost of Energy (LCOE). Using bottom up approach, this study evaluates offshore logistics during wind turbine construction with a broader contribution, conservatively from 0.6 to 7.6% of LCOE for offshore wind turbines over 4 MW power rating. It is also demonstrated that the higher the wind turbine size, the lower offshore logistics impact on LCOE. Conclusion: Offshore wind logistics costs during construction phase can represent between 0.6 and 7.6% of LCOE and it appears necessary to optimize these costs to contribute to a competitive LCOE. As main offshore logistics cost drivers have been identified, areas to reduce LCOE impact are suggested: increasing weather limits to reduce waiting on weather costs, minimizing work offshore, improving processes, using economy of scale and optimizing vessel use.