Latching control of a floating oscillating-water-column wave energy converter

Henriques, J.C.C.; Gato, L.M.C.; Falcão, António F. de O.; Robles, Eider; Faÿ, François-Xavier

doi:10.1016/j.renene.2015.12.065

Cited by 87 publications

(43 citation statements)

References 19 publications

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“…Due to the differences in power absorption principles between point absorbers and OWC converters, control strategies suggested for point absorbers cannot always be implemented on OWCs. There are three main possibilities to control an OWC converter: Phase control by latching [59,75,76] or by reactive control [77,78], air chamber pressure control by means of a relief valve installed in parallel to the air turbine [79,80], and rotational speed control [7,81]. Reactive control is relatively ineffective for OWC WECs, due to the relatively low efficiency of the air turbine when operating as a compressor [44].…”

Section: Air Turbinesmentioning

confidence: 99%

“…Regarding OWC control, control inputs (α in Figure 2) may be different depending on the implemented control strategy. The control input for the reactive phase control is the angle of the rotor blade of the Wells turbine [78], while for latching and chamber pressure control, the control input is the area of the control valve, implemented in series or in parallel [76,80]. In the case of the rotational speed control, load torque is adjusted via the electrical generator excitation or the power converter switching angle, depending on the configuration of the PTO system.…”

Section: Air Turbinesmentioning

confidence: 99%

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A Review of Wave-to-Wire Models for Wave Energy Converters

2016

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Control of wave energy converters (WECs) has been very often limited to hydrodynamic control to absorb the maximum energy possible from ocean waves. This generally ignores or significantly simplifies the performance of real power take-off (PTO) systems. However, including all the required dynamics and constraints in the control problem may considerably vary the control strategy and the power output. Therefore, this paper considers the incorporation into the model of all the conversion stages from ocean waves to the electricity network, referred to as wave-to-wire (W2W) models, and identifies the necessary components and their dynamics and constraints, including grid constraints. In addition, the paper identifies different control inputs for the different components of the PTO system and how these inputs are articulated to the dynamics of the system. Examples of pneumatic, hydraulic, mechanical or magnetic transmission systems driving a rotary electrical generator, and linear electric generators are provided.

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Section: Air Turbinesmentioning

confidence: 99%

Section: Air Turbinesmentioning

confidence: 99%

A Review of Wave-to-Wire Models for Wave Energy Converters

2016

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“…Henriques et al [14] applied latching control to an oscillating-water-column WEC. Son and Yeung [15] applied a real-time control to a pointabsorber by adjusting the PTO damping.…”

Section: Introductionmentioning

confidence: 99%

“…Tom et al [13] optimized the power capture of an oscillating surge WEC using the pseudo-spectral control method. Henriques et al [14] applied latching control to an oscillating-water-column WEC. Son and Yeung [15] applied a real-time control to a pointabsorber by adjusting the PTO damping.…”

Section: Introductionmentioning

confidence: 99%

Wave Force Prediction Effect on the Energy Absorption of a Wave Energy Converter With Real-Time Control

Yuan

Gao

et al. 2019

IEEE Trans. Sustain. Energy

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Liang Li et al.: Wave force prediction effect on the energy absorption of a wave energy converter with real-time control Abstract-Real-time control has been widely adopted to enlarge the energy extraction of a wave energy converter (WEC). In order to implement a real-time control, it is necessary to predict the wave excitation forces in the close future. In many previous studies, the wave forces over the prediction horizon were assumed to be already known, while the wave force prediction effect has been hardly examined. In this paper, we investigate the effect of wave force prediction on the energy absorption of a heaving point-absorber WEC with real-time latching control. The real-time control strategy is based on the combination of optimal command theory and first order-one variable grey model GM(1,1). It is shown that a long prediction horizon is beneficial to the energy absorption whereas the prediction deviation reduces extracting efficiency of the WEC. Further analysis indicates that deviation of wave force amplitude has little influence on the WEC performance. It is the phase deviation that leads to energy loss. Since the prediction deviation accumulates over the horizon, a moderate horizon is thus recommended.Index Terms-real-time control, wave energy converter, energy absorption, renewable energy, wave force prediction I. IntroductionT is expected that the global demand for energy will climb up to 25 percent by 2040 and the world is pursuing economic and renewable energy sources to keep up with this considerable demand growth [1]. Among various of ocean energy resources, sea waves take the advantage of high power density and all-day availability. To extract energy from ocean waves, WECs with various operation mechanisms have been developed. Li et al. [2] showed the power output of an oscillating-body WEC installed on a spar-type floating wind turbine. Boren et al. [3] presented a testing of a scaled vertical axis pendulum WEC. He et al. [4] utilized a floater breakwater to harvest energy from the waves. Experimental study of the concept was performed.Control action is introduced to the WEC to enlarge the energy absorption and broaden the bandwidth. Babarit et al. [5] studied how the declutching control influenced the energy absorption of a WEC in regular and irregular waves. Zou et al.[6] investigated constrained and unconstrained optimal control of a heaving point-absorber. Park et al. [7] proposed an phase L. Li, Z. M. Yuan (corresponding author), and Y. Gao, are with Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, (e-mail: liang.li@strath.ac.uk; zhiming.yuan@strath.ac.uk; yan.gao@strath.ac.uk ).control by estimating the wave period using velocity and acceleration information.The latching control was first proposed by Budal and Falnes [8]. They found that one condition for maximizing energy absorption was to keep the velocity in phase with the wave excitation force. Therefore, the latching control is a kind of phase control. Hoskin and Nichols [9] used op...

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“…Optimal latching of a floating spar-buoy OWC with bi-radial turbine was studied in Henriques et al (2016) considering full scale air compressibility. The optimal latching controller was implemented using a receding horizon formulation, where the optimal latching and unlatching times over a future time-period, or horizon, were determined using Pontryagin's maximum principle considering exact knowledge of the excitation force time-series over the future horizon.…”

Section: Introductionmentioning

confidence: 99%