Constrained Control of Moored Ocean Current Turbines With Cyclic Blade Pitch Variations

Ngo, Tri D.; Sultan, Cornel; VanZwieten, James H.; Xiros, Nikolaos I.

doi:10.1109/joe.2020.2985599

Cited by 11 publications

(5 citation statements)

References 29 publications

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“…Hence, the momentum portion of the blade element model determines the blade root angle according to the last rotor blade to pass its location. In addition, the open-and closed-loop flight controller is applied to move this OCT, which operates according to harmonic oscillations of blade root angles [44] [58].…”

Section: B Previously Developed Oct Simulation Algorithmsmentioning

confidence: 99%

“…Position and power signals in all cases have perturbations at frequencies around 0.0036 Hz (periods around 4.6 minutes) that are likely related minimally damped position states being excited by low-frequency turbulence perturbations. The stability of moored ocean current turbines is discussed in detail in [58], and these oscillations can be dampened through active control.…”

Section: Oct Operating In An Oceanic Environmentmentioning

confidence: 99%

See 1 more Smart Citation

Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine

Hasankhani

VanZwieten²,

Tang³

et al. 2021

Int. J. Mar. Ene.

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Increased global renewable power demands and the high energy density of ocean currents have motivated the development of ocean current turbines (OCTs). These compliantly mooring systems will maintain desired near-surface operating depths using variable buoyancy, lifting surface, sub-sea winches, and/or surface buoys. This paper presents a complete numerical simulation of a 700 kW variable buoyancy controlled OCT that includes detailed turbine system, inflow, actuator (i.e., generator and variable buoyancy), sensor, and fault models. Simulation predictions of OCT performance are made for normal, hurricane, and fault scenarios. Results suggest this OCT can operate between depths of 38 m to 329 m for all homogeneous flow speeds between 1.0-2.5 m/s. Fault scenarios show that rotor braking results in a rapid vertical OCT system assent and that blade pitch faults create power fluctuations apparent in the frequency domain. Finally, simulated OCT operations in measured ocean currents (i.e., normal and hurricane conditions) quantify power statistics and system behavior typical and extreme conditions.

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Section: B Previously Developed Oct Simulation Algorithmsmentioning

confidence: 99%

Section: Oct Operating In An Oceanic Environmentmentioning

confidence: 99%

Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine

Hasankhani

VanZwieten²,

Tang³

et al. 2021

Int. J. Mar. Ene.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Linear Model: The linearization process averages the MCT dynamics over the rotor rotation to remove the dependence on rotor azimuth angle and cable node states as suggested in [28] and is expanded to account for variable buoyancy control as proposed in [29] (with the justification that the linear and nonlinear models are in good agreement). The nonlinear dynamic model of the MCT is linearized around the equilibrium points, namely:…”

Section: Equations Of Motionmentioning

confidence: 99%

Integrated Path Planning and Tracking Control of Marine Current Turbine in Uncertain Ocean Environments

Hasankhani¹,

Ondes²,

Tang³

et al. 2021

Preprint

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This paper presents an integrated path planning and tracking control of marine hydrokinetic energy harvesting devices. To address the highly nonlinear and uncertain oceanic environment, the path planner is designed based on a reinforcement learning (RL) approach by fully exploring the historical ocean current profiles. The planner will search for a path to optimize a chosen cost criterion, such as maximizing the total harvested energy for a given time. Model predictive control (MPC) is then utilized to design the tracking control for the optimal path command from the planner subject to problem constraints. The planner and the tracking control are accommodated in an integrated framework to optimize these two parts in a real-time manner. The proposed approach is validated on a marine current turbine (MCT) that executes vertical waypoint path searching to maximize the net power due to spatiotemporal uncertainties in the ocean environment, as well as the path following via an MPC tracking controller to navigate the MCT to the optimal path. Results demonstrate that the path planning increases harnessed power compared to the baseline (i.e., maintaining MCT at an equilibrium depth), and the tracking controller can successfully follow the reference path under different shear profiles.

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“…The fill fractions are limited by the ratio between the buoyancy tank size 𝜈 B and the base buoyancy tank size 𝜈 b B (as formulated in ( 21)). It is noted that the linear model has one less state than the non-linear model as the rotor rotation angle state, 𝜙 r , is eliminated during the linearization process as described in [25]. Given that the nominal condition is defined by an averaged homogeneous flow speed of 𝑣 eq = 1.6m/s, the nominal states and control inputs are characterized by 𝑥 eq = [0 0 0 0 1.49 0 0 554.50 0.38 50 0.01 0.00 3.14] and 𝑢 eq = [0.4677 0.4677 − 188280].…”

Section: B Oct Dynamic Modeling For Controlmentioning

confidence: 99%

Control Co-Design for Buoyancy-Controlled MHK Turbine: A Nested Optimization of Geometry and Spatial-Temporal Path Planning

Hasankhani¹,

Tang²,

Snyder³

et al. 2021

Preprint

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Recent research progress has confirmed that using advanced controls can result in massive increases in energy capture for marine hydrokinetic (MHK) energy systems, including ocean current turbines (OCTs) and wave energy converters (WECs); however, to realize maximum benefits, the controls, power-take-off system, and basic structure of the device must all be co-designed from early stages. This paper presents an OCT turbine control co-design framework, accounting for the plant geometry and spatial-temporal path planning to optimize the performance. Developing a control co-design framework means that it is now possible to evaluate the effects of changing plant geometry on a level playing field when accounting for the OCT plant power optimization. The investigated framework evaluates the key design parameters, including the sizes of the generator, rotor, and variable buoyancy tank in the OCT system, and formulates these parameters' effect on the OCT model and harnessed power through defining a power-toweight ratio, subject to the design and operational constraints. The control co-design is formulated as a nested optimization problem, where the outer loop optimizes the plant geometry and the inner loop accounts for the spatial-temporal path planning to optimize the harnessed power with respect to the linear model of the OCT system and ocean current uncertainties. Compared with a baseline design, results verify the efficacy of the proposed framework in co-designing an optimal OCT system to gain the maximum power-to-weight ratio.

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Constrained Control of Moored Ocean Current Turbines With Cyclic Blade Pitch Variations

Cited by 11 publications

References 29 publications

Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine

Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine

Integrated Path Planning and Tracking Control of Marine Current Turbine in Uncertain Ocean Environments

Control Co-Design for Buoyancy-Controlled MHK Turbine: A Nested Optimization of Geometry and Spatial-Temporal Path Planning

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