Browsing by Author "Robles, Eider"
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Item Analysis of electrical drive speed control limitations of a power take-off system for wave energy converters(2017-12) Gaspar, José F.; Kamarlouei, Mojtaba; Sinha, Ashank; Xu, Haitong; Calvário, Miguel; Faÿ, François-Xavier; Robles, Eider; Guedes Soares, C.; Tecnalia Research & Innovation; RENOVABLES EFICIENCIA ENERGETICA Y CIRCULARIDAD; RENOVABLES OFFSHOREThe active control of wave energy converters with oil-hydraulic power take-off systems presents important demands on the electrical drives attached to their pumps, in particular on the required drive accelerations and rotational speeds. This work analyzes these demands on the drives and designs reliable control approaches for such drives by simulating a wave-to-wire model in a hardware in-the-loop simulation test rig. The model is based on a point absorber wave energy converter, being the wave, hydrodynamic and oil-hydraulic part simulated in a computer that sends and receives signals from the real embedded components, such as the drive generator, controller and back-to-back converter. Three different control strategies are developed and tested in this test rig and the results revealed that despite the drive limitations to acceleration levels, well above 1 × 104 rpm/s, these do not significantly affect the power take-off efficiency, because the required acceleration peaks rarely achieve these values. Moreover this drive is much more economical than an oil-hydraulic and equivalent one that is able to operate at those peaks of acceleration.Item Control strategies for combining local energy storage with wells turbine oscillating water column devices(2015-11-01) Ceballos, Salvador; Rea, J.A.; Robles, Eider; Lopez, Iraide; Pou, Josep; O´Sullivan, D.; O'Sullivan, Dara; POWER ELECTRONICS AND SYSTEM EQUIPMENT; RENOVABLES OFFSHOREThis paper proposes three generator control strategies for Wells turbine-based floating oscillating wáter column (OWC) devices comprising electrical or mechanical energy storage systems. The first control strategy is indicated for low inertia turbine OWC devices that include ultracapacitors. This control law optimizes the power take-off efficiency by means of an instantaneous speed controller that allows variation of the turbine rotational speed in a wave-by-wave basis. In addition, the profile of the electrical power injected into the grid is smoothed, so that a high penetration of wave energy does not threaten the grid stability. The second and third control laws are developed for OWC systems comprising a flywheel. Quasi-constant and variable speed controllers are proposed. These control laws do not maximize the system efficiency but allow the use of simpler, smaller and cheaper power electronics. Additionally the power quality is also optimized. The development of the proposed control algorithms is accomplished by means of simulations and verified with an experimental test rig.Item An Iterative Refining Approach to Design the Control of Wave Energy Converters with Numerical Modeling and Scaled HIL Testing(2020-05) Delmonte, Nicola; Robles, Eider; Cova, Paolo; Giuliani, Francesco; Faÿ, François Xavier; Lopez, Joseba; Ruol, Piero; Martinelli, Luca; Tecnalia Research & Innovation; RENOVABLES OFFSHORE; RENOVABLES EFICIENCIA ENERGETICA Y CIRCULARIDADThe aim of this work is to show that a significant increase of the e_ciency of aWave Energy Converter (WEC) can be achieved already at an early design stage, through the choice of a turbine and control regulation, by means of an accurate Wave-to-Wire (W2W) modeling that couples the hydrodynamic response calibrated in a wave flume to a Hardware-In-the-Loop (HIL) test bench with sizes and rates not matching those of the system under development. Information on this procedure is relevant to save time, because the acquisition, the installation, and the setup of a test rig are not quick and easy. Moreover, power electronics and electric machines to emulate turbines and electric generators matching the real systems are not low-cost equipment. The use of HIL is important in the development of WECs also because it allows the carrying out of tests in a controlled environment, and this is again time- and money-saving if compared to tests done on a real system installed at the sea. Furthermore, W2W modeling can be applied to several Power Take-O_ (PTO) configurations to experiment di_erent control strategies. The method here proposed, concerning a specific HIL for testing power electronics and control laws for a specific WECs, may have a more general validity.Item Sea trial results of a predictive algorithm at the Mutriku Wave power plant and controllers assessment based on a detailed plant model(2020-02) Faÿ, François-Xavier; Robles, Eider; Marcos, Marga; Aldaiturriaga, Endika; Camacho, Eduardo F.; Tecnalia Research & Innovation; RENOVABLES EFICIENCIA ENERGETICA Y CIRCULARIDAD; RENOVABLES OFFSHOREImproving the power production in wave energy plants is essential to lower the cost of energy production from this type of installations. Oscillating Water Column is among the most studied technologies to convert the wave energy into a useful electrical one. In this paper, three control algorithms are developed to control the biradial turbine installed in the Mutriku Wave Power Plant. The work presents a comparison of their main advantages and drawbacks first from numerical simulation results and then with practical implementation in the real plant, analysing both performance and power integration into the grid. The wave-to-wire model used to develop and assess the controllers is based on linear wave theory and adjusted with operational data measured at the plant. Three different controllers which use the generator torque as manipulated variable are considered. Two of them are adaptive controllers and the other one is a nonlinear Model Predictive Control (MPC) algorithm which uses information about the future waves to compute the control actions. The best adaptive controller and the predictive one are then tested experimentally in the real power plant of Mutriku, and the performance analysis is completed with operational results. A real time sensor installed in front of the plant gives information on the incoming waves used by the predictive algorithm. Operational data are collected during a two-week testing period, enabling a thorough comparison. An overall increase over 30% in the electrical power production is obtained with the predictive control law in comparison with the reference adaptive controller.Item A Simplified Modeling Approach of Floating Offshore Wind Turbines for Dynamic Simulations(2022-03-18) López-Queija, Javier; Robles, Eider; Llorente, Jose Ignacio; Touzon, Imanol; López-Mendia, Joseba; Tecnalia Research & Innovation; RENOVABLES OFFSHORECurrently, floating offshore wind is experiencing rapid development towards a commercial scale. However, the research to design new control strategies requires numerical models of low computational cost accounting for the most relevant dynamics. In this paper, a reduced linear time-domain model is presented and validated. The model represents the main floating offshore wind turbine dynamics with four planar degrees of freedom: surge, heave, pitch, first tower foreaft deflection, and rotor speed to account for rotor dynamics. The model relies on multibody and modal theories to develop the equation of motion. Aerodynamic loads are calculated using the wind turbine power performance curves obtained in a preprocessing step. Hydrodynamic loads are precomputed using a panel code solver and the mooring forces are obtained using a look-up table for different system displacements. Without any adjustment, the model accurately predicts the system motions for coupled stochastic wind–wave conditions when it is compared against OpenFAST, with errors below 10% for all the considered load cases. The largest errors occur due to the transient effects during the simulation runtime. The model aims to be used in the early design stages as a dynamic simulation tool in time and frequency domains to validate preliminary designs. Moreover, it could also be used as a control design model due to its simplicity and low modeling order.Item Standardising Marine Renewable Energy Testing: Gap Analysis and Recommendations for Development of Standards: Gap analysis and recommendations for development of standards(2021-09-06) Noble, Donald R.; O’Shea, Michael; Judge, Frances; Robles, Eider; Martinez, Rodrigo; Khalid, Faryal; Thies, Philipp R.; Johanning, Lars; Corlay, Yann; Gabl, Roman; Davey, Thomas A. D.; Vejayan, Nithiananthan; Murphy, Jimmy; RENOVABLES OFFSHOREMarine renewable energy (MRE) is still an emerging technology. As such, there is still a lack of mature standards and guidance for the development and testing of these devices. The sector covers a wide range of disciplines, so there is a need for more comprehensive guidance to cover these. This paper builds on a study undertaken in the MaRINET2 project to summarise recommendations and guidance for testing MRE devices and components, by reviewing the recently published guidance. Perceived gaps in the guidance are then discussed, expanding on the previous study. Results from an industry survey are also used to help quantify and validate these gaps. The main themes identified can be summarised as: the development progression from concept to commercialisation, including more complex environmental conditions in testing, accurately modelling and quantifying the power generated, including grid integration, plus modelling and testing of novel moorings and foundation solutions. A pathway to a standardised approach to MRE testing is presented, building on recommendations learnt from the MaRINET2 round-robin testing, showing how these recommendations are being incorporated into the guidance and ultimately feeding into the development of international standards for the marine renewable energy sector.