Researchers from North
Carolina State University have developed a new way to
fine-tune wireless power transfer (WPT) receivers, making the systems more
efficient and functional. WPT systems hold promise for charging electric
vehicles, electronic devices, and other technologies.

Researchers have shown that it is possible to transmit power wirelessly by
using magnetic resonance. Even minor changes in how the transmitter or receiver
is tuned, however, can result in faulty power transmission.

A new prototype developed at NC State addresses the problem by automatically—and
precisely—re-tuning the receivers in WPT systems. The researchers focused on
receivers because methods already exist that allow researchers to use
electronics to precisely tune the transmitters.

“We’re optimistic that this technology moves us one step closer to realizing
functional WPT systems that can be used in real-world circumstances,” says Dr.
Srdjan Lukic, an assistant professor of electrical and computer engineering at
NC State and co-author of a paper on the research.

WPT systems work by transmitting magnetic waves on a specific frequency from
a transmitter to a receiver. These magnetic waves interact with a coil in the
receiver to induce an electric current. If the coil is tuned so that its resonant
frequency matches the frequency of the magnetic waves, the current it produces
is amplified. However, if the receiver and the transmitter are out of tune, the
system becomes inefficient and doesn’t transfer a significant amount of power.
The receiver coil still picks up a trace amount of current, but it is not
amplified.

This is a problem because many factors can affect the tuning of a receiver
or transmitter, such as temperature or proximity to other magnetic objects. In
other words, a hot summer day could wreak havoc on the tuning of a receiver.

Lukic and NC State PhD student Zeljko Pantic developed an electronic
prototype that incorporates additional circuitry into the receiver that does
two things: It injects small amounts of reactive power into the receiver coil
as needed to maintain its original resonant frequency; and, if the
transmitter’s tuning changes, the prototype can read the trace amount of
current being transmitted and adjust the receiver’s tuning accordingly.

“Because we are using electronics to inject reactive power into the receiver
coil, we can be extremely precise when tuning the receiver,” Lukic says. “This
degree of fine-tuning maximizes the efficiency of the WPT system.

“The next step is to try incorporating this work into technology that can be
used to wirelessly charge electric vehicles.”

The paper, “Framework and Topology for Active Tuning of Parallel Compensated
Receivers in Power Transfer Systems,” is published online in IEEE
Transactions on Power Electronics.

Source: North Carolina State University