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Power Flows – Husheng Li

by Theresa Pepin

Controlling how power flows is as important as producing it in the first place.

Husheng Li and his team are designing a wireless communication network to add “nerves” to “muscles” for controlling distributed energy resources in the smart grid. Planned to be flexible, reliable, “plug-and-play” and self-healing, the design of the communication network will be field tested in the Distributed Equipment Communication and Control laboratory at ORNL.

Led by Aleksandar Dimitrovski, the LDRD project will use inexpensive, saturable reactors to control the power flow in an experimental microgrid. Also known as saturable-core reactors, these devices work on the principle of magnetic saturation to provide a way for a large AC current to be controlled by a much smaller DC current—essentially stabilizing and improving the quality of the power load.

Husheng LiA communication channel is also indispensable for optimal coordination and flow control. Li’s wireless communication network will help coordinate the actions of the distributed saturable reactors, rendering microgrid power-flow controls more robust and efficient.

Microgrids are a key component in the goal of modernizing and securing “smart” electric grids. As defined by the Microgrid Exchange Group at a recent Department of Energy workshop, a microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries; it acts as a single controllable entity with respect to the grid and can connect or disconnect, enabling it to operate in both grid-connected or island-mode.

Basically, microgrids promise to allow for greater integration of renewable energy sources while increasing the reliability, efficiency, and security of electrical transmission and distribution systems.

By meeting end-user needs and ensuring energy supply for critical loads, these distributed systems can control power quality and reliability at the local level and promote customer participation through demand-side management and community involvement in electricity supply. Microgrids also support macrogrids by handling sensitive loads and the variability of locally produced renewables, while at the same time supplying ancillary services to the bulk power system.

Graduate StudentsLi and graduate students Kun Zheng, Rukun Mao, and Hannan Ma, will study access-channel and data-channel design and routing (especially re-routing) mechanism requirements such that the coordination of reactors and power flow control is not interrupted. They plan a “plug-and-play” network, wherein a new reactor equipped with a wireless transceiver will be able to broadcast its specifications and participate immediately in the control network; it will also be efficient in its use of frequency spectrum and “self-healing,” so that it can find new paths for data traffic in the case of a node outage.

With this collaboration, the JDRD team has the opportunity to go beyond traditional data such as multimedia to consider data traffic in cyber-physical systems. Their results will open channels to seek smart grid funding available from DOE, utility companies, and power equipment manufacturers.

JDRD project:
Wireless communication network design for flow control in microgrid
Husheng Li, UT Department of Electrical Engineering and Computer Science

LDRD project:
Power Flow Control Using Distributed Saturable Reactors
Aleksandar D. Dimitrovski, ORNL Energy and Transportation Science Division