This paper illustrates an approach to the modeling of a point absorbing Wave Energy Converter (WEC) with the intent of analyzing the sensitivity of the system response to variation in the model parameters. Using first principles, the nonlinear equations of motion are formed to describe the heave motion of a 3 body system. A linearized model is developed and used to simulate the system in both the time and frequency domains. The input to the model is a time series displacement and a time series velocity that describes the incident waves. A sensitivity analysis is then performed on the system parameters to show how the characteristics of the heave plate, the component masses, and the mass of the entrained fluid affect the performance of the system. The model is validated by numerically modeling a generation 1 device produced by Oscilla Power Inc., which is compared against experimental data from a field test on Lake Washington. The WEC is designed to provide tension along a series of tethers with connected power take off units. The wave input is specified using frequency spectra measured with a nearby Datawell Waverider MK III buoy during the field testing, from which time domain waves are reconstructed.
to address overall systems operation, reliability, safety, power quality, and institutional issues. This subcontract to develop, model, and test the DENNIS TM household/neighborhood controller approach supports the program's R&D focus of strategic research. Specifically, the project meets the needs for automated, adaptive, intelligent interconnection and control as well as technology to enable aggregation, grid support, and ancillary services from distributed resources. The objective of this subcontract over its 3-year duration is to develop a household controller module and demonstrate the ability of a group of these household controllers to operate through an intelligent, neighborhood controller. The controllers will provide a smart, technologically advanced, simple, efficient, and economic solution for aggregating a community of small distributed generators into a larger single, virtual generator capable of selling power or other services to a utility, independent system operator (ISO), or other entity in a coordinated manner. 1. Switching and power-conversion devices in the laboratory had remote-operation capabilities built in, and each of these devices was tested from a central computer. 2. A 500-W proton exchange membrane (PEM) fuel cell was added to the existing photovoltaic and wind generation capacity installed at the laboratory.
In many advanced control strategies the wave excitation force is key to determining the control input. However, it is often difficult to measure the excitation force on a Wave Energy Converter (WEC). The use of Kalman filters to estimate the wave excitation force based on readily available measurement data can potentially fill the gap between the development of WEC control strategies and the data that is available. Two different estimation methods using an nonlinear Extended Kalman Filter are tested on experimental wave tank data for a heaving semi-submerged float. The first method relies on directly including the excitation force as a state in the first order dynamics-which allows the "random walk" of the Kalman filter to identify an estimate of the excitation force.The second method of estimation involves modeling the wave excitation force as a harmonic oscillator comprised of sinusoidal components. Both methods are evaluated for a variety of incident waves and additional sensitivity analyses are performed to investigate the susceptibility of these estimation methods to changes in the model, measurement noise, and sampling rate.
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