Publications

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Paper targets SPEEDAM 2024 (https://www.speedam.org). The paper provides details of a model predictive control designed to operate a four-zone medium-voltage AC/DC electric ship.

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Our present electric power grid maximizes spinning inertia of fossil fuel generators (inherent energy storage) to meet stability and performance requirements. Our goal is to begin to investigate the replacement of the large spinning inertia of fossil fuel generators with energy storage systems (ESS) including information flow as a necessary part of the renewable energy sources (RES) and subject to certain criteria. General criteria metrics include: energy storage, information flow, estimation, communication links, central versus decentralized, etc. Our focus is on evaluating the Fisher Information Equivalency (FIE) metric as a multi-criteria trade-off cost function for the minimization of ESS options and information flow. This paper begins with a formal conceptual definition of an infinite bus. Then a simple example of a One Machine Infinite Bus (OMIB) system with a Unified Power Flow Controller (UPFC) to demonstrate the FIE-based approach to minimize the ESS. A second more detailed example of several spinning machines are included with representative power electronic and ESS for RES that are attached to the electric power grid. A simple trade-study begins to highlight requirements to support large penetration of RES. Keep in mind for a large scale high penetration of RES will require large investments in ESS which we want to minimize.

A high altitude electromagnetic pulse (HEMP) caused by a nuclear explosion has the potential to severely impact the operation of large-scale electric power grids. This paper presents a top-down mitigation design strategy that considers grid-wide dynamic behavior during a simulated HEMP event - and uses optimal control theory to determine the compensation signals required to protect critical grid assets. The approach is applied to both a standalone transformer system and a demonstrative 3-bus grid model. The performance of the top-down approach relative to conventional protection solutions is evaluated, and several optimal control objective functions are explored. Finally, directions for future research are proposed.

The following article describes an optimal control algorithm for the operation and study of an electric microgrid designed to power a lunar habitat. A photovoltaic (PV) generator powers the habitat and the presence of predictable lunar eclipses necessitates a system to prioritize and control loads within the microgrid. The algorithm consists of a reduced order model (ROM) that describes the microgrid, a discretization of the equations that result from the ROM, and an optimization formulation that controls the microgrid’s behavior. In order to validate this approach, the paper presents results from simulation based on lunar eclipse information and a schedule of intended loads.

The National Aeronautics and Space Administration’s (NASA) Artemis program seeks to establish the first long-term presence on the Moon as part of a larger goal of sending the first astronauts to Mars. To accomplish this, the Artemis program is designed to develop, test, and demonstrate many technologies needed for deep space exploration and supporting life on another planet. Long-term operations on the lunar base include habitation, science, logistics, and in-situ resource utilization (ISRU). In this paper, a Lunar DC microgrid (LDCMG) structure is the backbone of the energy distribution, storage, and utilization infrastructure. The method to analyze the LDCMG power distribution network and ESS design is the Hamiltonian surface shaping and power flow control (HSSPFC). This ISRU system will include a networked three-microgrid system which includes a Photo-voltaic (PV) array (generation) on one sub-microgrid and water extraction (loads) on the other two microgrids. A system's reduced-order model (ROM) will be used to create a closed-form analytical model. Ideal ESS devices will be placed alongside each state of the ROM. The ideal ESS devices determine the response needed to conform to a specific operating scenario and system specifications.

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This new research provides transformative marine energy technology to effectively power the blue economy. Harmonizing the energy capture and power from Wave Energy Converter (WEC) arrays require innovative designs for the buoy, electric machines, energy storage systems (ESS), and coordinated onshore electric power grid (EPG) integration. This paper introduces two innovative elements that are co-designed to extract the maximum power from; i) individual WEC buoys with a multi-resonance controller design and ii) synchronized with power packet network phase control through the physical placement of the WEC arrays reducing ESS requirements. MATLAB/Simulink models were created for the WEC array dynamics and control systems with Bretschneider irregular wave spectrum as inputs. The numerical simulation results show that for ideal physical WEC buoy array phasing of 60 degrees the ESS peak power and energy capacity requirements are minimized while the multi-resonant controllers optimize EPG power output for each WEC buoy.

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This paper presents a nonlinear control design technique that capitalizes on an hour glass (HG) variable geometry wave energy converter (WEC). The HG buoy is assumed to operate in the heave motion of the wave. The unique interaction between the HG buoy and the wave creates a nonlinear cubic storage effect that produces actual energy storage or reactive power during operation. A multi-frequency Bretschneider spectrum wave excitation input is reviewed for the HG design both with constant and varying steepness angle profiles which demonstrates further increased power generation. Numerical simulations are performed to demonstrate the increase in power generation with changing sea states. The objective is to increase the power generation from multi-frequency nonlinear dynamic sources.

Pulse power loads are becoming increasingly more common in many applications primarily due to applications like radar, lasers, and the technologies such as EMALS (ElectroMagnetic Aircraft Launch Systems) on next-generation aircraft carriers. Pulse power loads are notorious for causing stability issues. Stability for pulse power loads can be defined as metastable, where the system can be unstable for a portion of the pulse as long as the stability is re-established over the entire pulse. Dynamic characteristics for step changes in load can be improved with a modified boost converter topology in conjunction with bang-bang control. Improvement in the metastability margins will be presented through simulations with the application of the modified topology to pulse power loads.

An array of Wave Energy Converters (WEC) is required to supply a significant power level to the grid. However, the control and optimization of such an array is still an open research question. This paper analyzes two aspects that have a significant impact on the power production. First the spacing of the buoys in a WEC array will be analyzed to determine the optimal shift between the buoys in an array. Then the wave force interacting with the buoys will be angled to create additional sequencing between the electrical signals. A cost function is proposed to minimize the power variation and energy storage while maximizing the delivered energy to the onshore point of common coupling to the electrical grid.

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