Imagine a system that handles electricity flow not just from the power company to our homes, but also back from our homes to the power company. North Carolina State University researchers say an existing technology – the solid-state transformer — could make the conceptual "smart grid" a reality.

The NC State team developed a complex model that simulates the behavior of a power distribution system, accounting for the electronics-based transformers, energy sources, and energy storage. The model is scalable, and hence, can be used to predict the behavior of power distribution systems of any size.

Dr. Iqbal Husain, ABB Distinguished Professor of Electrical and Computer Engineering at NC State.

“We have shown how multiple units of these solid-state transformers can function reliably in the context of the larger power grid,” said Dr. Iqbal Husain, ABB Distinguished Professor of Electrical and Computer Engineering at NC State and director of the FREEDM Center.

“Using this model, we found that SSTs can greatly enhance the functionalities of tomorrow’s power grid.”

Tech Briefs: What is a solid-state transformer, and how can it be used to support a new kind of smart grid?

Dr. Iqual Husain: A solid-state transformer (SST) is an electronic transformer designed and developed to serve as the next-generation transformers to be used in the power distribution system, replacing the traditional iron core based transformers.

Being electronic in nature, the SSTs are controllable with embedded intelligence, which enables them to not only step up or down AC voltages but also to regulate and route energy flow.

In addition, SSTs can deliver DC voltages unlike traditional transformers that deliver only AC voltages. The control and energy routing is enabled through communication with other SSTs in the system. The idea is for these SSTs to work together throughout the larger power grid in order to coordinate power distribution efficiently.

Tech Briefs: Let's say a smart grid, enabled by solid-state transformers, becomes a reality. Take me through how it would work, and how the energy would travel from homes to businesses and back into the power grid.

Husain: The smart grid enabled by solid-state transformers serves as an energy router where power can flow in either direction. Thus, if there is renewable generation, such as rooftop solar available in a home, and there is excess generation, then the homeowner can sell to other homes or businesses connected to another section of the power grid through another solid-state transformer.

In this scenario, one solid-state transformer will enable energy flow from the home with excess generation to the power grid, and the second solid-state transformer will deliver that energy from the power grid to the other home or business in need of power.

Tech Briefs: What has prevented the smart grid from being a reality?

Solid-state transformers, developed at North Carolina State University. (Credit: NC State)

Husain: Today's power distribution system does not allow energy routing among multiple customers, and is extremely limited in its ability to allow reverse power flow from home or business back to the power grid. The solid-state transformers forming the power distribution grid and their intelligent controllers provide the technical means to allow the customer to participate in the energy market based on economic, social, security, and environmental considerations.

Tech Briefs: What is most exciting to you about this study?

Husain: The most exciting aspect of this study is the feasibility of reliable operation of a power distribution network formed with solid-state transformers which will enable significantly higher level of penetration of renewable energy penetration. In this smart grid network, the customer will be empowered to make choices and benefit financially.

Tech Briefs: What are your goals for the next year?

Husain: Our goal next year is to demonstrate the multi-SST operation and energy exchange among multiple customers in a demonstration platform in FREEDM headquarters on NC State Centennial Campus. It will become both a model and lab as FREEDM researchers continue to refine the components that will change both the grid and how we interact with it: a solid-state transformer that allows bi-directional flow and takes away the need to convert DC current to AC for home use, and the controllers and algorithms that allow them to work together.

What do you think? Will the smart grid become a reality? Share your thoughts below.

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