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to the U.S. Energy Information
Administration (EIA), by 2013 (the
latest year for which numbers are
available) U.S. electric utilities had
installed 51,924,502 smart meters of
which 89 percent were in residential
customer installations.
Smart meters are more than
just monitoring units that can be
interrogated remotely. A key advantage
of these intelligent devices is the
supply of information that allows both
utilities and consumers to manage
supply and demand. Utilities are able
to use the information to precisely
determine peaks in demand and
reserve generating capacity for similar
future peaks. The utility can also set
“dynamic” tariffs, reflecting the costs
(and carbon content) of generation
and distribution at any particular time,
or rewarding consumers for using
electricity at times when renewable
sources are producing a lot of power.
Consumers could even opt for
packages that allow appliances to be
turned on and off automatically by the
grid operator to help maintain virtually
a second-by-second balance between
supply and demand.
A downside of smart meters is the
requirement for them to be “always
on.” Each unit draws relatively little
current, but the combined effect of
millions is significant. The silicon
vendors have responded by cutting the
quiescent current of their high-voltage
power solutions for these always-on,
non-isolated systems for applications
such as smart meters.
Several manufacturers offer AC-to-
DC voltage regulators that meet the
tough demands of smart metering. For
example, STMicroelectronicssupplies a
power supply module, the VIPER06,
that can operate froman 85V to 265VAC
input and features an 800V power
metal-oxide semiconductor field-effect
transistor (MOSFET). The chip can
output up to 8W yet consumes just
a few hundred microamps quiescent
current.
For its part, TI has recently introduced
the UCC28880, an AC-to-DC switching
regulator for smart-meter applications.
The UCC28880 integrates the controller
and a 700V power MOSFET into one
device. The chip also integrates a
high-voltage current source, enabling
start-up and operation directly from
the rectified mains voltage.
The quiescent current of the device
is less than 100µA, improving the
efficiency of the solution. TI says that
by using the UCC28880 engineers
can design most common regulator
topologies using a minimum number
of external components.
Utilities have also implemented
“concentrators” as part of their smart-
metering systems. Concentrators
gather information from a group of
smart meters (for example, those
in a single apartment block) and
aggregate and analyze the data
before transmitting it wirelessly or
via a power line modem to the utility.
Concentrators can also be used to send
information from the central control
facility back to the smart-meter group
and facilitate maintenance functions
such as software updates.
In addition to supplying power modules
for smart meters, STMicroelectronics
also caters for the power requirements
of concentrators. The power
requirements for concentrators are
similar to those for smart meters,
although a little more demanding due
the additional computation performed
by the unit.
STMicroelectronics promotes the
Altair 04-900 AC-to-DC switching
voltage regulator for concentrator
applications. It is based on a quasi-
resonant flyback topology and is
capable of operating from a mains
input and features a 900V breakdown
power stage. The Altair features
low-standby consumption (around
1mA) and overcurrent protection
to safeguard against transformer
saturation and secondary diode short
circuiting. The company also provides
a power supply reference design for
smart-metering applications, under
the part number STEVAL-ISA105V1
(Figure 4).
Huge rewards
Modernizing decades-old electricity
infrastructure with computerization
and communications technology in
the U.S. and the rest of the developed
world is a huge task. The cost of the
exercise will run into billions of dollars
without even factoring in disruption to
customers as sections of the grid are
upgraded.
However, the rewards are great. A
smart grid will dramatically improve
the efficiency of the electricity system
by reducing system losses, make
it easier to switch in renewable
energy sources (thus reducing the
requirement for “base load” - fossil-
fuel generating capacity that must
be kept running permanently to cope
with anticipated peaks), and enable
utilities to encourage consumers
to reduce consumption through
flexible tariffs. Higher efficiency and
greater contributions from renewable
sources also helps authorities meet
their commitments to reduce carbon
emissions.
Smart grids also limit disruption caused
by outages by allowing operators
to quickly isolate faults and re-route
power to as many consumers as
possible while the problem is rectified.
The success of smart grids will rely
heavily on novel silicon and innovative
design engineers; and those products
will in turn rely on specialized power
modules that meet the particular
requirements of smart- grid application
such as wide-input voltage ranges and
low-quiescent currents. The good
news is that there are already many
integrated solutions commercially
available for engineers looking to take
a slice of this lucrative market sector.
For more information about the parts
discussed in this article, use the links
provided to access product pages on
the Digi-Key website.
References:
1.
“Carbon Emission Reductions by
the Implementation of a Smart Grid,”
Steven Keeping, NOJA Power, 2013.
2.
“Smart Grid & Energy Solutions
Guide,” Texas Instruments, 2015.
Contributed By Electronic
Products, DigiKey Electronics
New-Tech Magazine Europe l 32