Power distribution systems for the U.S. Navy fleet are essential for peak operation and effectiveness.

Naval platforms are trending toward electric energy-based payloads for weapons systems as well as higher power radars and prolusion systems. Many of these systems require energy in the form of pulses that need energy storage to meet their demands. To get  energy where and when it’s needed from supplies and storage distributed around the ship, methods to effectively route and shape that energy are critical.

Electrical Engineering Professor Herb Ginn is currently in the middle of a $1 million, four-year Office of Naval Research (ONR) and Department of Defense-funded project that started in September 2023. The project aims to build upon developments in Ginn’s previous work with discretized energy control (DEC) for enabling packet-based energy flow for naval shipboard power distribution systems.

Connections to Ginn’s current research go back to the mid-1990s and an ONR-sponsored project at Virginia Tech University’s Center for Power Electronics Systems. The Power Electronics Building Blocks (PEBB) project developed several electronics conversion systems for marine applications to demonstrate advanced capabilities by using a modular approach to high power electronics.

You need to have fast communication for a building block approach, so we wanted to know how we could leverage it to do more.

- Herb Ginn

In 2015, Ginn became a collaborator in the PEBB project and performed work focused on control systems. At that time, the project investigated field programmable gate arrays (FPGAs), which are versatile integrated circuits that can be programmed to perform a variety of digital functions.

“FPGA’s were not the type of control gear that were traditionally used in power electronics,” Ginn says. “But we were interested in moving toward them because it could reduce the overall weight, size, and density of these building blocks by pushing the frequency of operation higher with faster control and communication systems.”

Based on the successful results of networked FPGA-based control of power electronics, Ginn received $750,000 over three years from the ONR for his discretized energy control project. His current project builds upon developments from his initial work.

The DEC framework utilizes voltage and current within each control cycle to enable the specification of an energy packet. Within each interval of time, an energy change is specified by the packet to move energy in or out of an electrical element with storage.

DEC also enables application functions within clusters of PEBBs by moving energy controlled in discrete units. Because the movement of energy is commanded in intervals corelated to the control and communication timing, all applications exist exclusively as data flows on the PEBB communication network.

“You need to have fast communication for a building block approach, so we wanted to know how we could leverage it to do more,” Ginn says. “DEC tries to couple communication to the low-level control and shifts everything into an energy pattern with each module commanded in a period of time.”

Ginn is currently using model predictive control methods to move energy coupled to control data network timing via a distributed model of the PEBB cluster. He is working on additional developments to expand the DEC concept beyond the PEBB cluster to encompass an entire shipboard microgrid.

The expansion includes extending the size of PEBB packet clusters, exchanging energy between PEBB clusters to include the entire ship distribution system, and allowing the adjustment of energy packets due to unexpected faults.

“The cluster might be as many as 20 building blocks, but the system may be hundreds across the ship,” Ginn says. “Since we made the clusters work and have a system of them, we’re now working on having them talk to one another and figure out how we'll get energy from this source to those loads in the prescribed amount of time and keep everything in operation.”

This type of networked power electronics-based distribution system is capable of faster energy flow when system control is performed at higher control layers. Adjusting energy flows via network traffic aims to create an efficient power distribution system.

“FPGA is a programmable digital platform that has numerous gigabit communication channels and processing power to enable predictive control techniques. We’ve embedded real-time models in each control node and leveraged co-simulation techniques to couple the models in a distributed fashion,” Ginn says. “The communication network is coupling all those models so that they're equivalent to one large model and make the control fast and precise.”

Over the first two years of his current project, Ginn has worked on some of the real-time techniques for the models that were embedded in the FPGAs with the goal of making the cluster size as large as possible.

“From a system level perspective, we want to know how we can represent the cluster to be efficient and pass on energy to other clusters,” Ginn says. “You want to capture all the relevant behaviors but not make it any more complicated than absolutely necessary.”

Ginn has also upgraded his digital platform to expand the cluster size. In the last two years of the project, new algorithms based on the cluster representation will be developed for managing the behavior to determine how they pass energy back and forth.

While Ginn says the applications and requirements for the U.S. Navy are more intense, the same technology can also be applied to other microgrid applications.

“We have a Department of Energy project that's just starting for rural micro-grid connectivity, and we’ll employ some of our previous work,” Ginn says. “It would be modularized power electronics on a smaller scale and be smaller than the PEBB clusters we're doing for the Navy.”

While Ginn’s current project may be expanded into a larger program, he is hoping to have a follow up project if his current work is successful.

“It would result in not just more funding but maturing some of the more applied practical de-risking and transition parts,” Ginn says. “We're doing algorithms and determining what will happen if the communication links fail. If it’s successful, then it has a chance to be picked up and some of this technology may show up in the Navy fleet.”