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. Wireless
charging is hot design trend for mobile phone and other
such wireless device charging and also for electric vehicle
charging.
A new prototype developed at NC State addresses the problem
of tuning receiver and transmitter 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 Ph.D. 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
and was supported by the Advanced Transportation Energy
Center at NC State. The paper was co-authored by Pantic
and Lukic
Author: Srinivasa Reddy N
