A resistance emulation approach to optimize the wave energy harvesting for a direct drive point absorber

Mendonça, Hugo; Martínez, Sergio

doi:10.1109/tste.2015.2466097

Cited by 33 publications

(22 citation statements)

References 37 publications

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“…The configuration of a realistic PTO system can be complicated. To focus on the scope of the present research, the PTO system is numerically treated as a spring-damper system, which is a reasonable approximation [17] and widely adopted by the other researchers [18]. The initial position of the WEC refers to 1 = -2.…”

Section: Clearly Demonstrate the Benefits Of The Multi-stablementioning

confidence: 99%

Multi-Stable Mechanism of an Oscillating-Body Wave Energy Converter

Zhang

Yuan

et al. 2020

IEEE Trans. Sustain. Energy

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The present research aims to utilize the multi-stable mechanism to increase the energy conversion of the oscillatingbody wave energy converter (WEC). Considering that a majority of WEC concepts are linear and single-stable, a nonlinear springdamper model is proposed to achieve the multi-stable mechanism. The system is either monostable or bistable depending on the initial condition of the springs. The energy conversion of a heaving point-absorber with the nonlinear spring-damper model is investigated in the present research. Firstly, a state-space dynamic model of the heaving point-absorber is developed. Then the energy conversion at both the monostable mode and the bistable mode is simulated. The present research also illustrates the response feature at the two stable modes. It is found the nonlinear pointabsorber behaves like a linear system in the monostable mode. The energy conversion is just increased slightly. Nevertheless, the energy absorption is increased substantially in the bistable mode. It is found that the velocity phase is adjusted in the bistable mode, leading to the enhancement of the energy conversion.

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Section: Clearly Demonstrate the Benefits Of The Multi-stablementioning

confidence: 99%

Multi-Stable Mechanism of an Oscillating-Body Wave Energy Converter

Zhang

Yuan

et al. 2020

IEEE Trans. Sustain. Energy

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“…In this work, according to the classification proposed in [16], a point absorber has been considered, and the details about the WEC dynamics can be found in [29,38]. This absorber is a cylindrical buoy limited to heave motion and rigidly connected to the PTO system.…”

Section: Wave-to-wire Modelmentioning

confidence: 99%

“…On the other hand, the grid-side converter is responsible for the DC-AC conversion stage, and it can be also used to help to comply with some grid connection requirements by means of a VSC (voltage source converter) controller. The current controller is implemented with the resistance emulation (R em ) approach [29], and a strategy to mitigate the voltage fluctuations (described later) is implemented with a PWM-based VSC controller under unbalanced input voltages [39].…”

Section: Wave-to-wire Modelmentioning

confidence: 99%

“…To do so, an unbalanced three-phase load flow that is able to take into account the unbalance of loads, the asymmetry due to un-transposed lines and the presence of single-phase and two-phase lines has been implemented. The performance of the proposed strategy is assessed with a continuation load flow [28] implementing a test distribution grid, coupled to a wave-to-wire model of the WEC [29].…”

Section: Introductionmentioning

confidence: 99%

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Voltage Impact of a Wave Energy Converter on an Unbalanced Distribution Grid and Corrective Actions

et al. 2017

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Renewable energy is steadily increasing its penetration level in electric power systems. Wind and solar energy have reached a high degree of maturity, and their impacts on the grid are well known. However, this is not the case for emerging sources like wave energy. This work explores the impact of the fluctuating power injected by a wave energy converter on the distribution grid voltage and proposes a strategy for mitigating the induced voltage fluctuations. The paper describes the mechanics of how a fluctuating active power injection leads to grid voltage fluctuations and presents an unbalanced three-phase power flow tool that allows one to quantitatively analyze the voltage evolution at every phase and bus of a distribution grid driven by this power injection. The paper also proposes a corrective action for mitigating the voltage fluctuations that makes use of the hardware resources already available in the wave energy converter, by means of a control strategy on the reactive capability of the grid-side inverter. The use of a STATCOM as additional reactive compensation equipment is also explored. The effectiveness of the proposal is assessed in the IEEE 13-bus test feeder showing that, in some cases, the wave energy converter by itself is able to mitigate the voltage fluctuations that it causes. If not, a STATCOM can provide the extra reactive capability needed.

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“…The PTO tuning consists of adjusting the damping of the system, if a passive control method is adopted, or it may require adjustment of both the system damping and the stiffness for a reactive control method. The tuning strategies usually require knowledge of the incident wave frequency [1]- [5] or the excitation force frequency [8], [9]. Since these frequencies change with time for non-stationary signals, a time-frequency representation for the waves is expected -i.e.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Time–Frequency Estimation Methods on the Performance of Wave Energy Converters Under Passive and Reactive Control

Garcia‐Rosa

Ringwood

Fosso

et al. 2019

IEEE Trans. Sustain. Energy

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A number of wave energy controllers tune the power take-off (PTO) system to the frequency of incident waves. Since real ocean waves are non-stationary by nature and not defined by a single frequency component, the PTO can be either tuned at a constant frequency characterized by the local spectrum, or continuously tuned to a representative wave frequency. In either case, a time-frequency representation of the waves is expected since the wave profile changes over time. This paper discusses about the PTO tuning problem for passive and reactive controllers, in real waves, by comparing different methods for time-varying frequency estimation: the extended Kalman filter (EKF), frequency-locked loop (FLL), and Hilbert-Huang transform (HHT). The aim is to verify the impact of such methods on the absorbed and reactive powers, and the PTO rating. It is shown that the mean estimated frequency of the EKF, and FLL, converges respectively to the mean centroid frequency, and energy frequency, of the excitation force spectrum. Moreover, the HHT mean frequency has no correlation with the spectral statistical properties. A comparison of the energy absorbed shows that up to 37% more energy is obtained with the HHT over the other estimation methods. Numerical simulations are performed with sea elevation data from the Irish coast.

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A resistance emulation approach to optimize the wave energy harvesting for a direct drive point absorber

Cited by 33 publications

References 37 publications

Multi-Stable Mechanism of an Oscillating-Body Wave Energy Converter

Multi-Stable Mechanism of an Oscillating-Body Wave Energy Converter

Voltage Impact of a Wave Energy Converter on an Unbalanced Distribution Grid and Corrective Actions

The Impact of Time–Frequency Estimation Methods on the Performance of Wave Energy Converters Under Passive and Reactive Control

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