Multivariable direct-drive linear generators for wave energy

Huang, Sy‐Ruen; Chen, Hong-Tai; Chung, Chih‐Hung; Chu, Chen-Yeon; Li, Gung-Ching; Wu, Chueh-Cheng

doi:10.1016/j.apenergy.2012.03.038

Cited by 26 publications

(11 citation statements)

References 18 publications

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“…A point absorber type of WEC to be studied in this paper has a float with a constant radius cylinder on the sea surface. Wave energy can be captured using different power take-off (PTO) mechanisms, for example the PTO based on a direct linear generator [31], or the one based on a hydraulic motor and converters [32]. Fig.…”

Section: Modelling Of Wec and Problem Formulationmentioning

confidence: 99%

Robust Optimal Control of Wave Energy Converters Based on Adaptive Dynamic Programming

Wang

et al. 2019

IEEE Trans. Sustain. Energy

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This paper presents a robust adaptive optimal control strategy for wave energy converters (WECs). We first propose a new estimator in a simple form to address modeling uncertainties and formulate the control of WECs as an optimal control problem. Then a novel energy maximization control strategy is developed based on the concept of adaptive dynamic programming (ADP), where a critic neural network (NN) is used to approximate the time-dependent optimal cost value. To achieve guaranteed convergence, a recently proposed adaptive law based on the parameter estimation error is further tailored to online update the weights of critic NN. Consequently, the critic NN output, e.g. the costate, can be used to compute the optimal feedback control. The proposed robust ADP WEC control method is not only effective in handling dynamic uncertainties, but also computationally efficient with a very fast online convergence rate for the weights of the critic NN (less than 20 seconds for irregular sea waves as demonstrated in the simulations). These advantages significantly enhance the real-time applicability of the proposed method. Simulation results show that this approach is robust to model uncertainties and has significantly reduced computational costs for implementation. Index Terms-Wave energy converter, adaptive optimal control, adaptive dynamic programming, uncertainty estimator.

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Section: Modelling Of Wec and Problem Formulationmentioning

confidence: 99%

Robust Optimal Control of Wave Energy Converters Based on Adaptive Dynamic Programming

Wang

et al. 2019

IEEE Trans. Sustain. Energy

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“…The excitation wave force drives the float, resulting in the relative heave motion between the piston fixed to the buoy and the cylinder fixed to the seabed (or anchored through mooring lines, but with a negligible heave motion of anti-heave plate compared to that of the float). This relative motion creates fluid flow that drives the power take-off (PTO) system to generate power; the typical PTO mechanism includes direct linear generators [14] and hydraulic motors connected to electricity generators [15]. The external manipulated force f u acting on the piston is the control input.…”

Section: Introductionmentioning

confidence: 99%

Linear Optimal Noncausal Control of Wave Energy Converters

Zhan

2019

IEEE Trans. Contr. Syst. Technol.

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This paper addresses the fundamental theoretical development of a linear optimal noncausal control for wave energy converters (WECs) in a closed analytic form. It is well known that wave energy converter control is a noncausal control problem, i.e. the future wave information contributes to the present control action. This paper provides a reliable, efficient and simple linear optimal controller with guaranteed stability for WEC control problem. The proposed WEC linear optimal control (LOC) consists of a causal linear state feedback part and an anticausal linear feedforward part to incorporate the influence of future incoming waves. The stability of the closed-loop WEC control system with the proposed linear optimal controller is proven. The contribution of the noncausal term using wave prediction information to the optimal control and the energy output is analyzed quantitatively. The proposed linear controller can be more preferred when constraint satisfaction becomes a less important issue for mild sea states and some well-designed WECs with an ample operation range. The proposed optimal control strategy can be extended for a generic class of energy maximization problems. Numerical simulations are presented to justify the efficacy of the proposed WEC optimal control.

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“…Since the linear velocity of WED obtained from the oceanic wave is variable, the linear generator runs at irregular speed [7]. Different types of flat and tubular type linear generators have been investigated; almost all of them have a solid translator of steel cores with large mass [8]- [12].…”

Section: Introductionmentioning

confidence: 99%

Design and Analysis of a Novel Lightweight Translator Permanent Magnet Linear Generator for Oceanic Wave Energy Conversion

et al. 2017

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At present, most of the linear generators contain a heavy translator for harvesting wave power from the ocean into electrical power. As the translator is connected to the buoy, the buoy dynamic performance is reduced by the large mass and as a result low velocity of the translator would degrade the electricity generation of the linear generator. This problem has been minimized by the new design in this paper, where the translator is clipped off at first and split into two separate portions to minimize its weight and a secondary stator coupled magnetically with a special m-shaped main stator is used to flow the necessary magnetic flux. The weight of the proposed translator is 21.82% lower than the conventional one and 49.1% by using a recently available permanent magnet with higher specifications. The finite element method is applied for the analysis and comparison between the new and conventional designs with the aid of ANSYS simulation software. Different parameters of the existing and the proposed linear generator have been presented and compared. The simulation results show that the proposed one can generate the same amount of electricity as the existing one with almost half of the translator size. According to the mathematical model, it is understood that the dynamics of the translator would be higher for its lower mass and vice versa. Therefore, minimizing the translator size would result in decrease of mass, which increases the dynamics of the buoy connected to the translator.Index Terms-Linear generator, m-shaped stator, split translator, secondary stator, wave energy converter.

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Multivariable direct-drive linear generators for wave energy

Cited by 26 publications

References 18 publications

Robust Optimal Control of Wave Energy Converters Based on Adaptive Dynamic Programming

Robust Optimal Control of Wave Energy Converters Based on Adaptive Dynamic Programming

Linear Optimal Noncausal Control of Wave Energy Converters

Design and Analysis of a Novel Lightweight Translator Permanent Magnet Linear Generator for Oceanic Wave Energy Conversion

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