Browsing by Keyword "energy conversion"

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    Efficiency optimization in low inertia wells turbine-oscillating water column devices
    (2013) Ceballos, Salvador; Rea, Judy; Lopez, Iraide; Pou, Josep; Robles, Eider; Osullivan, Dara L.; POWER ELECTRONICS AND SYSTEM EQUIPMENT; RENOVABLES OFFSHORE
    The Wells turbine is a bidirectional air turbine which operates efficiently over a restricted range of air flow. The optimization of its efficiency requires control of rotational velocity in order to maintain the ratio between airflow and tip speed within the high efficiency range. This paper introduces two generator control strategies that optimize the power take-off efficiency for low inertia turbine systems in which instantaneous control of the turbine air flow to tip speed ratio is a realistic goal. The first control strategy requires measurement of turbine rotational speed and air chamber pressure, and the second strategy removes the requirement for air pressure measurement. The implementation issues associated with this level of control are examined and the simulation results are validated in an experimental test rig.
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    Evaluation of electromechanical systems dynamically emulating a candidate hydrokinetic turbine
    (2016-01-01) Cavagnaro, Robert J.; Neely, Jason C.; Faÿ, Franois Xavier; Mendia, Joseba Lopez; Rea, Judith A.; RENOVABLES EFICIENCIA ENERGETICA Y CIRCULARIDAD; RENOVABLES OFFSHORE
    Implications of conducting hardware-in-the-loop testing of a specific hydrokinetic turbine on controllable motor-generator sets or electromechanical emulation machines (EEMs) are explored. The emulator control dynamic equations are presented, methods for scaling turbine parameters are developed and evaluated, and experimental results are presented from three EEMs programmed to emulate the same vertical-axis fixed-pitch turbine. Although hardware platforms and control implementations varied, results show that each EEM is successful in emulating the turbine model at different power levels, thus demonstrating the general feasibility of the approach. However, performance of motor control under torque command, current command, or speed command differed. In a demonstration of the intended use of an EEM for evaluating a hydrokinetic turbine implementation, a power takeoff controller tracks the maximum power-point of the turbine in response to turbulence. Utilizing realistic inflow conditions and control laws, the emulator dynamic speed response is shown to agree well at low frequencies with numerical simulation but to deviate at high frequencies.
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    Modeling and control of a wave energy farm including energy storage for power quality enhancement: The bimep case study
    (2014-05) Tedeschi, Elisabetta; Santos-Mugica, Maider; POWER SYSTEMS
    This paper presents a complete wave-to-wire approach to the modeling of wave energy farms. It captures all the main peculiarities of such applications, from the variability of sea waves to the issues related to the grid integration of a multi-MW wave farm, including the hydrodynamic modeling of wave energy converters (WECs). The paper specifically discusses the different levels of control of a wave farm and their integration and coordination. These are crucial to meet the power quality requirements at the point of common coupling (PCC) and ensure the efficiency of the power transfer from the waves to the main electric grid. A specific real-time technique for the centralized control of a wave farm is also proposed, which is exemplified with reference to the PCC voltage control in the real test case of bimep. Critical cases of weaker grids are also considered to extend the validity of the analysis.