World-Gen Volume 27 No 1 - page 11

Lou Lambruschi explains why central
inverters are intended for larger applica-
tions at higher voltage levels, so they are
more likely to be self-contained and field-
ready than string and microinverters.
In performing basic DC to AC conver-
sion, they are similar to string and micro
inverters, but central units are more likely
to include advanced features like power fac-
tor control, reactive power on demand and
revenue metering. Central inverters gener-
ally include robust fault ride-through provi-
sions, allowing them not only to continue to
operate through a fault, but also to offer
grid support. Thanks to their larger size,
redundancy can be designed into these
inverters to offer continued operation even
during a component failure. Users also ben-
efit from the intrinsic lower cost per kilo-
watt of a larger inverter, which — com-
bined with the right feature set and high
efficiency — can result in a lower total cost
of ownership.
Some manufacturers are incorporating
liquid cooling technology in their central
inverter models for a smaller footprint and
little or no air filter maintenance. While
water/glycol cooling systems are the most
widely used, a two-phase evaporative cool-
ing system with pumped refrigerant is
emerging as an alternative. This results in a
more compact and efficient system that
removes a lot of heat with a little liquid.
Such a system also minimizes consumable
items like filters and coolant additives. This
non-conductive system is also much safer
than mixing water with high-power elec-
On the operational side, central invert-
ers are evolving into more than just power
conversion devices. Features that make the
inverters more grid interactive increase
their value to the owner as a dispatchable
asset. Many models offer flexibility with
dual operating modes, allowing the inverter
to work equally well on command in grid-
parallel or island mode. Improved monitor-
ing and fault detection with a robust com-
munication interface is another increasingly
desirable feature.
Serviceability is also an important con-
cern with central inverters. While a smaller
inverter can be literally swapped out on
site, central inverters have traditionally had
larger and harder to access components. To
counter this disadvantage, newer modular
designs with lightweight interchangeable
phase modules, capacitors, inductors and
fans improve field serviceability. With an
accessible, modular design, scheduled
maintenance or even major repairs can be
done in an hour or less — rather than sev-
eral days. Preferably, all serviceable compo-
nents can be accessed externally without
requiring an operator to enter the inverter
enclosure. External access panels also
enhance safety and simplify permitting.
Central inverters tend to be most
attractive options for ground-mounted
installations that are 400 kW and higher,
and when 1000-V or higher input capability
is required. Central inverters designed and
built with environmental sealing and self-
contained cooling systems can be sited in
desert or coastal conditions without need-
ing housing. Central inverters with “smart”
features are also desirable in situations that
require energy management. Such central
inverters can provide grid support with
power factor control or by providing reac-
tive power on demand.
As more renewable sources are
deployed, grid power quality will become
an increasing concern. There will likely be
a corresponding demand for “smart” cen-
tral inverters that can support the grid. We
see a growing demand for devices that will
meet both current and proposed industry
regulations, and anticipate that this trend
will continue.
Parker Hannifin Energy Grid Tie
Division is located in Charlotte, NC, and is
part of Parker’s Automation Group. The
division focuses its operational and global
growth strategies on power conversion for
renewable energy and on utility scale and
micro-grid energy storage products and
technology. Its products are used to support
the rapidly expanding renewable energy
market and the associated energy storage
requirements needed to integrate renewable
sources and to improve utility grid stability
and quality. The charter of the division is to
continue rapid development and accelerated
growth of this emerging market for energy
storage, solar power, wind power, and other
fast growing grid tie systems.
The Charlotte facility includes manufac-
turing and test capabilities, as well as prod-
uct design and project engineering. Field
engineering and startup service are provid-
ed by a team of direct service engineers
deployed regionally, and international sup-
port is augmented by Parker’s extensive
network of global facilities.
Parker’s track record in energy storage
includes installations beginning in 2008,
and over 100 megawatts of capacity
installed to date. Major projects include a
32 megawatt system at Laurel Mountain
WV, an AES wind farm, and a 12 megawatt
system in Chile at AES – Gener. Parker is a
founding member of MESA (Modular
Energy Storage Architecture) Standards
Alliance, and provided MESA compliant
power conversion equipment for the
Snohomish PUD project.
Louis Lambruschi has worked in the
field of electrical power conversion for over
three decades with Parker and other firms.
During his tenure with Parker, he has
worked extensively in the field of grid tie
inverters as applied to electricity storage and
the harvesting of renewable energy. Lou
earned a Bachelor of Science degree in elec-
trical engineering from Rensselaer
Polytechnic Institute in Troy, NY.
Marketing Communications & E-Business Manager
Parker Hannifin-Energy Grid Tie Division
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