AUGUST 2004
Princeton Power Begins Testing New
Distributed Wind Turbine Inverter
Technology
By Kathy Belyeu
AWEA Staff
 s
part of a research effort to make distributed small wind turbines
more cost effective for individuals, the U.S. Department of Energy
(DOE) has undertaken an initiative to fund
public/private partnerships into improved
components and wind power systems. DOE and one of its national
laboratories, the National Renewable Energy Laboratory (NREL),
awarded a grant last year to Princeton Power
Systems (PPS) to design and develop an advanced
technology power inverter to control the power output from
wind turbines, using its patented AC-link conversion technology. The
"concept and feasibility system" prototype has recently been
completed and hooked up to a test device that simulates a 50-kW wind
turbine. For the next couple of months, PPS will collect data on the
inverter to prove its efficiency, and to demonstrate power control at
low and high speeds. DOE is investing $588,834 for a research project
expected to last 18-24 months.
PPS expects that the new inverter will be able to lower generator noise
due to less voltage distortion, yield a higher system efficiency, and
extend the generator's life, which means a quieter and less expensive
wind turbine. The inverter is designed for a 50-kW wind turbine, and
can be "stacked" for use in a 100-kW turbine. The company has been
working with Bergey Windpower and Northern Power Systems to make the
converter compatible with their wind turbines in
development. "On today's advanced
variable-speed small wind turbines, the power
electronics are a critical link in the system," stated Mike Bergey,
president of Bergey Windpower. "We are excited about Princeton Power
Systems' AC-link technology, and look forward to assisting them in
this important development program." Darren
Hammell, president and CEO of Princeton Power
Systems, said that the AC-link converter is
expected to operate at a system efficiency of
96-97%, whereas typical inverters in use today operate at full system
efficiencies of 92-93%. That could lower the cost of energy by 30%.
The technology breakthrough that PPS is researching is
advanced software control that allows use of a
Silicon Controlled Rectifier (SCR) transistor
instead of the Insulated Gate Bipolar Transistor (IGBT) that
is usually used in wind turbine inverters. Hammell said that in the
past, SCR inverters were not able to provide power that was
compatible with the utility grid, because the SCR
transistors were difficult to control, so there
was too much distortion.
The next phase would be to optimize the component and
package it as a commercial product.
PPS is a start-up technology company founded by four Princeton
graduates. In addition to the inverter, it is also working on other
power conditioning devices to enable renewable energy production and
energy conservation. More information on Princeton Power is available
at
http://www.princetonpower.com .
The June Windletter contained information about two other
grants that were awarded as part of DOE's research
initiatives: a $2-million award to Northern Power
Systems to design a 100-kW NorthWind Wind Turbine
for broad application, and a $1.5-million development grant to a
consortium of engineers and manufacturers headed by Dr. Woody
Stoddard, of Amherst, Mass., to adapt reaction
injection molding to medium-size wind turbine
blades.
In the small wind turbine roadmap that AWEA developed in
conjunction with DOE, specific areas of interest
were identified that relate to future advances in
distributed wind technology. These areas of interest
include: 1) reduction in turbine system costs; 2) reduction in
manufacturing costs; 3) improvements in reliability; 4) improvements
in power electronics design and reliability; 5)
reduction of noise; 6) development of better
analytical tools; 7) improvement in overspeed
control knowledge; and 8) development of more cost-effective, taller
towers. The roadmap is available at
http://www.awea.org/smallwind/documents/31958.pdf
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