HVDC Distribution Study of Intelligent Power System

University of Dayton Research Institute

High Voltage Direct Current (HVDC) aviation electrical power systems (EPS) provide many advantages, particularly in the area of weight savings. Despite the advantages, there are technical challenges for these systems as the power and dynamic response demanded by high power and more-electric loads increases. High power HVDC systems require low source impedance which makes larger fault energy available to the system. In addition, flight and mission critical loads demand constant power and fast response by a tightly regulated EPS. These loads on a HVDC distribution can cause dynamically negative resistance resulting in poor power quality and/or loss of system stability.

AFRL’ s objective is to develop an intelligent power system to advance the state of the art in system efficiency and safety. This is a far-reaching and broad area of research that is best served by the participation of multiple research institutions that have developed expertise in specific areas. To that end, this Statement of Objectives outlines work where Michigan Technological University (MTU) has demonstrated outstanding research.
Specific areas of research that AFRL is interested in having MTU participate in this program are outlined below. The results of this research and development effort shall be available to all other parties collaborating on the AFRL Intelligent Power System Program as well as industry concerns involved with United States aviation power systems so that best practices and recommendations can be incorporated in future power system design concepts.

1.1 Analysis, Design, and Control of components (ns – ms level)
1.2 Distributed management/optimization of source and loads (ms – s level):
1.3 Mission level load planning(> 1 s level)
1.4 Energy Storage (ES) for pulsed power loads

Investigators: Wayne Weaver, Gordon Parker

Bo Chen


Dr. Chen is the Dave House Associate Professor of Mechanical Engineering and Electrical Engineering in the Department of Mechanical Engineering – Engineering Mechanics and Department of Electrical and Computer Engineering at Michigan Technological University. She received her Ph.D. degree from the University of California, Davis, in 2005. Dr. Chen conducts interdisciplinary researches in the areas of mechatronics and embedded systems, agent technology, modeling and control of hybrid electric vehicles, cyber-physical systems, and automation. Her research projects are funded by National Science Foundation, Department of Energy, and industrial partners. Dr. Chen has authored or co-authored over 70 peer-reviewed journal and conference papers. She received the Best Paper Award at 2008 IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications.

Dr. Chen is currently serving as the Chair of the Technical Committee on Mechatronics and Embedded Systems of IEEE Intelligent Transportation Systems Society and the Chair of the Technical Committee on Mechatronic and Embedded Systems and Applications of ASME Design Engineering Division. She is an Associate Editor of the IEEE Transactions on Intelligent Transportation Systems. Dr. Chen has served as Program Chair, Symposium Chair, and Session Chair for a number of international conferences. She was the General Chair of 2013 ASME/IEEE International Conference on Mechatronic and Embedded Systems and Applications.
Areas of Expertise
Mechatronics and embedded systems
Agent Technology
Monitoring and control networks
Hybrid electric vehicles
Smart grid

Research Interests
Modeling and control of hybrid electric vehicles
EV-smart grid integration
Distributed monitoring and control
Battery control for HEV and energy storage systems
IC engine management systems
Sensor information fusion

CAREER: Autonomous Underwater Power Distribution System for Continuous Operation

National Science Foundation

Success of numerous long-term robotic network missions in space, air, ground, and water is measured by the ability of the robots to operate for extended time in highly dynamic and potentially hazardous operating environments. The proposed work responds to the urgency for development of innovative mobile power distribution systems that lower deployment and operating costs, while simultaneously increasing mission efficiency, and supporting the network’s need to be responsive to changing physical conditions. The overall CAREER goal is to develop a power distribution system that responds to individual robot needs, as well as, overall robotic network goals to guarantee persistence of long-term operation in uncertain and unstructured environments.

The proposed work is informed by the hypothesis that network persistence hinges on the ability to establish stable energy transfer cycles necessary to accomplish coverage specifications, while simultaneously dealing with physical and environmental constraints. To test this hypothesis and as an example of such a system, this work will focus on creating a reliable autonomous recharging system for autonomous underwater vehicles (AUVs) that enables continuous real-time marine observation and data collection in the presence of continuously changing underwater environmental circumstances. The key challenges are two-fold: there are fundamental hardware challenges connected to energy transfer in the harsh underwater environment, but more importantly there are basic network science needs that are novel to a mobile power network. The specific research thrusts for this CAREER work include: 1) Task and Energy Routing Scheduling for Persistent Mission Planning. 2) Efficient Network Path Planning and Coordination to Accomplish Persistent Mission Plan. 3) Experimental Validation through Test-bed Development. 4) Design-based, Research-integrated Education Plan for Broadening Underrepresented Participation in STEM.

Intellectual Merit:
This project builds a roadmap to achieve robust continuous marine autonomy that advances unmanned marine systems ability to perform autonomous long-term missions. More specifically the proposed work will provide: 1) resource based task scheduling, 2) path planning formation for mission and charging, and 3) integration tools for testing. Expected outcomes will overcome the current challenge of significant interruptions during underwater missions due to battery limitations and recharging needs. Through this CAREER proposal, the Pl will establish the theoretical, computational, and experimental foundation for mobile power delivery and onsite recharging capability for autonomous underwater vehicles (AUVs). The developed power distribution system will be able to reconfigure itself depending on the scope of the mission, as well as, the energy consumption needs of the network, the number of operational AUVs and required operation time, recharging specifications, communication and localization means, and environmental variables.

Such a system will play a vital role in real-time controlled applications across multiple disciplines, such as: sensor networks, robotics, and transportation systems where limited power resources and unknown environmental dynamics pose major constraints. All developed tools will be suited for the capabilities of not only low-cost AUVs with limited sensing and computational resources, but also high-tech AUVs with state of the art sensor packages.

Broader Impacts:
The developed active power distribution system focuses on underwater scenarios, but will be transferrable to space, air, and ground missions as well. This type of feasible power distribution solution can be used to optimize: 1) immediate high-risk disaster recovery missions like the Fukushima nuclear plant accident; 2) search missions that require vast underwater inspection and detection like the Malaysia MH370 passenger aircraft; and 3) long-term space observation and monitoring like that of the lunar skylight or Europa space mission. The findings from this project will be disseminated through publications, software sharing, and technology commercialization. The project provides interdisciplinary training opportunities for graduate, undergraduate, and pre-college students, including those from underrepresented groups. Research activities will be integrated with education through curriculum development, outreach and improved GUPPIE design.

Investigator: Nina Mahmoudian

Collaborative Research: On Making Wave Energy an Economical and Reliable Power Source for Ocean Measurement Applications

National Science Foundation

Work Plan:
Task 1: Wave-by-wave control and Multi-resonant control
(a-i) Wave-by-Wave Control: Generalize to conversion from relative oscillation in surge, heave, and pitch modes. This step places high expectations on geometry design, because the chosen geometry needs to maximize wave radiation (radiation damping) by relative oscillation in all three modes. Typically, for small axi-symmetric buoys, radiation damping in surge and pitch modes is considerably smaller than that in heave mode. Therefore, greater oscillation excursions are typically required for optimal conversion in these modes. In addition, the power requirements of the wave measurement hardware also need to be included in the daily/annual powver calculations. For the X-band Radar hardware applicable to the up-wave distances of interest to us (on the order of 1000 m), the power consumption is expected to be less than 300 W (average). This could pose a challenge in some wave conditions, but it is likely that the use of multiple modes and optimized geometries will help to provide sufficient usable power for the iFCB application we are pursuing in this work. We plan to extend the current simulations to address these needs.
(a-ii) Geometry Design: New geometry design/utilization approaches to maximize the radiation damping for the 3 relative oscillation modes are being considered. These will be evaluated through detailed simulations in the forthcoming period.
(b) Multi-resonant Control: Current implementations need to be extended to incorporate realistic oscillation constraints. Further extensions to 2-body systems with power capture from relative oscillation are also required, and are planned for the forthcoming period. Finally, the procedure also needs to be extended to investigate multiple-mode conversion (i.e. relative heave, pitch, and surge oscillations).
Task 2: Actuator Design and Energy Storage
Work is planned for the forthcoming period where propose to examine favorably interacting buoy-instrument cage geometries that will minimize the need for large amounts of reactive power to flow through the system. Particular attention will be given to hydrodynamic and mechanical coupling effects and ways to provide negative stiffness through geometry design.
In addition, non-polluting high-lubricity hydraulic fluids will be evaluated through actuator dynamic models over the frequency range of interest.
Task 3: Simulation of Complete System and Wave Tank Testing
This is an important part of the project. The complete system will be simulated following inclusion of multiple-mode relative oscillation conversion and more detailed actuator design. Besides the power requirements of the wave measurement system, all other non-function-critical power needs embedded within the overall system (on-board electronics, etc.) will be included in this simulation.
Wave tank tests are planned as part of this project. Preparations are currently underway to install a wave tank (with flap type absorbing wave makers) capable of providing accurate and repeatable sea states for this project. 1/2 or 1/5 scale models are planned.

Investigator: Umesh Korde

Hydrodynamic Control Using X-Band Radar for Wave Energy Converter Technology

U.S. Dept of Defense, Naval Facilities Engineering Command

The current approach for designing wave energy converters is to use a floating-body tuned to the wave climate, which results in a very large device that is expensive to build, service and deploy. Additionally, because the device is designed to be tuned to a specific climate, it will not work effectively in a different location ·with a different climate. Therefore, the current approach for designing wave energy converters is not conducive to long-term economic application.

Economically significant size reduction and year-round power increases are only possible through operation near theoretical efficiency limits in constantly changing wave conditions, which requires active hydrodynamic control. However, the wave-by-wave control necessary for best conversion is not possible without wave-elevation information up to some duration into the future (this in large part is because of the force due to the waves generated by body oscillation in response to the incident wave field). By incorporating wave-elevation prediction based on a deterministic propagation model that accounts for a realistic range of wave-group velocities in conjunction with wave measurements in the up-wave directions, we have been able to confirm, through simulations, a 10-fold increase in power conversion under a swept-volume oscillation constraint for an omni-directional heaving buoy type device.
Availability of instantaneous wave profile (“wave surface elevation” or “wave elevation”) measurements and wave surface elevation predictions is important to the success of the control approach being pursued in this work. Equally important is the near-optimal wave-by-wave control approach itself.

Proposed research:
1. A method for obtaining instantaneous wave surface elevation information on a wave-by wave basis using a low-cost X-band Radar (the state of the art, as represented by the commercially available WaMOS system is optimized to provide spectral information.
2. A method for providing constrained near-optimal wave-by-wave control for maximizing the energy conversion by small wave energy converters.
3. Although the focus of the proposed research is wave energy converter technology, the results of this work are expected to find application in other forthcoming Navy developments. Wave-by-wave surface elevation prediction and near-optimal power absorption techniques demonstrated in this effort can be extended to facilitate critical mid-sea shipboard operations such as helicopter/ aircraft landing, cargo handling, etc. The techniques demonstrated as part of this research will also provide technology to enhance and optimize seakeeping characteristics of Navy ocean platforms.

Investigator: Umesh Korde

Increasing Ship Power System Capability throught Exergy Control

U.S. Dept. of Defense, Office of Naval Research

The main objective of this effort is to develop an exergy control strategy, applied to a ship medium voltage de (MVDC) grid that exploits exergy flow coupling between multiple subsystems. This work involves: 1) exergy control strategy development and 2) mapping exergy control system performance to ship-relevant metrics. A ship power grid Challenge Problem model will be developed to illustrate and resolve the fundamental gaps of exergy control. The model will also compare and contrast feedforward and feedback exergy control with conventional strategies.

Ship subsystems and mission modules perform energy conversion during their operation resulting in a combination of electricity consumption, heat generation and mechanical work. Mission module thermal management requirements further impact the ship’s electrical grid, for example, via chiller operation. Subsystems often have opportunities for performing an energy storage role during their operation cycle. A ship crane is one example where potential energy is stored in the raised load and can be converted into electrical energy during lowering. Whether subsystem requirements are dominated by electrical, thermal or mechanical functions, they are coupled through energy and information flows, often by the ship’s electrical power grid. Treating each subsystem as a disconnected entity reduces the potential for exploiting their inherent interconnection and likely results in over designed shipboard systems with higher than necessary weight and volume. Realizing the opportunity of coupled subsystem operation requires modeling and control schemes that are unavailable today, but that we believe should require few infrastructure changes. We propose that the design and control of coupled ship subsystems should be based on exergy- the amount of energy available for useful work. A recent study, applied to a room heating system, showed that exergy control increased the overall efficiency by 18%. Since the system was powered electrically, this translated directly to a decrease in the electrical load. The main objective of this effort is to develop an exergy control strategy, applied to a ship medium voltage de (MVDC) grid that exploits exergy flow coupling between multiple subsystems.

An exergy approach to control permits consideration of both mission modules and the platform infrastructure as mixed physics power systems that may act as loads, storage or sources depending on the situation. Instead of separately designed and managed subsystems that satisfy electrical and thermal requirements via static design margins a, multi-physics, unified system-of-systems approach is needed to enable affordable mid-life upgrades as requirements and mission systems evolve over the platform’s lifespan. Being able to translate the benefits of exergy control into savings in mass, volume, energy storage requirements and fuel usage is necessary for making rational design decisions for new ship platforms and for increasing the efficiency of legacy ship systems. Currently, there does not exist an analysis technique to map control system performance into ship-relevant performance metrics. This restricts ship designers from understanding the tradeoffs of adopting advanced control schemes that may exploit subsystem coupling. One of the objectives of this work is to develop a method for extrapolating control system performance into ship-relevant metrics that impact mass, volume, energy storage, and fuel usage.

As described above, there are two main thrusts to this work: (1) exergy control strategy development and (2) mapping exergy control system performance to ship-relevant metrics. We will develop a ship power grid Challenge Problem model that will illustrate the fundamental gaps of exergy control that will be addressed. The model will also be used to compare and contrast feedforward and feedback exergy control with conventional strategies. Techniques for mapping the results of the exergy control to weight, volume, and energy storage requirements will be developed and applied to the Challenge Problem throughout the project.

Investigators: Gordon Parker and Rush Robinett, and Ed Trinklein.

On Integrating New Capability into Coastal Energy Conversion Systems

National Science Foundation -South Dakota School of Mines & Technology

Analyze and simulate the power capture from arrays of wave energy converters (WECs) with and without the presence of an object. Nonlinear WECs will be analyzed and exploited for more energy capture. For object detection, MTU will develop an estimator. In addition to having a model that detects the presence of an object, the estimator will use that model and account for uncertainties that we have in the model and also measurement errors; in any case we need to know statistical characteristics about these uncertainties and errors. MTU will participate in the WEC array overall design, analysis, modeling and simulations; control design for Design 2, nonlinear modeling and control, and topology optimization.

Investigator: Ossama Abdelkhalik and Mark Vaughn

Umesh Korde

Umesh Korde has been active in the area of ocean wave energy utilization since 1982. He has worked on several aspects of the problem, though his research over the last three decades has primarily been concerned with the dynamics, control, and hydrodynamics of oscillating bodies and pressure distributions performing as the primary working element of a wave energy converter. Of particular interest in the last few years have been small devices capable of integration into measurement and sensing systems in the ocean, as well as shore and ocean based microgrids serving a variety of applications. A focal area of his current research has been new techniques for modeling and control, including novel ways to utilize existing approaches.

Dr. Korde has also worked on the dynamics and control of flexible bodies including lightweight membranes, for space applications such as steering and shaping of laser beams, tunable passive damping of lightweight structures, and self-healing of structures using focused stress waves. Dr. Korde serves as an associate editor for the journal J Ocean Engineering and Marine Energy (Springer), and is a Fellow of the American Society of Mechanical Engineers.

Research Specialties

  • Dynamics and control: floating body hydrodynamics, hydrodynamic modeling of buoys, cables;
  • Modeling and control of flexible and smart structures;
  • Wave energy converters, near-optimal control in the time domain;
  • Adaptive and nonlinear control of floating bodies;
  • Low-dissipation actuator and mechanism development, development of new detection and sensing modalities;
  • Deterministic wave prediction;
  • Control of ship-board systems
  • Wave powered microgrids
  • Wave Energy Conversion (WECs)

    WECS are devices with moving elements that are directly activated by the cyclic oscillation of the waves for Ocean wave energy utilization and energy harvesting. Power is extracted by converting the kinetic energy of these displacing parts into electric current; dynamics, control, and hydrodynamics of oscillating bodies and pressure distributions performing as the primary working element of a wave energy converter. Specific recent research has been on small devices capable of integration into measurement and sensing systems in the ocean, as well as shore and ocean based microgrids serving a variety of applications. A focal area of this current research has been new techniques for modeling and control, including novel ways to utilize existing approaches.

    Toward Undersea Persistence

    Office of Naval Research

    The current challenge impeding advances in the U.S. Navy’s mobility is significant interruptions during undersea missions. Missions such as studying arctic physical environments; understanding the effects of sound on marine mammals; submarine detection and classification; and mine detection and neutralization in both the ocean and littoral environment require persistent operation of unmanned systems in challenging and dynamic environments. The proposed work will create an architecture that integrates three elements of energy, communication, and docking to guarantee undersea persistence where limited power resources and unknown environmental dynamics pose major constraints. The architecture will take into account: the number of operational AUVs required for different operation periods, recharging specifications, communication and localization means, and environmental variables.

    The overall goal of this project is: to develop a mobile power delivery system that lowers deployment and operating costs while simultaneously increasing network efficiency and response in dynamic and often dangerous physical conditions. The aim is to create network optimization and formation strategies that will enable a mobile power deliver system to meet overall mission specifications by: 1) reconfiguring itself depending on the number of operational AUVs and; 2) responding to energy consumption needs of the network, situational condition, and environmental variables. The outcome of this work will be a theoretical, computational, and experimental roadmap for building and implementing an autonomous distributed system with mobile power delivery and onsite recharging capability. This roadmap will address fundamental hardware and network science challenges. The long-term outcome of this work will be a persistent and stealthy large area presence of AUV fleets able to perform undersea Navy missions by accurately and autonomously responding to energy needs, situational dynamics and environmental variables.

    Investigator: Nina Mahmoudian