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Awards vFinal DR 18/12/09 09:37 Page 38
Industry Development Award
Issue VI 2009
The Fraunhofer Institute for Solar Energy
Systems ISE is recognised for its work, which
has seen a new world record of 99.03 % for the
efficiency of inverters used in photovoltaic
systems. By using new components and
improving the circuit technology, the researchers have thus reduced losses
compared to their own previous top-level
performance by a further third.
“We now use junction field-effect transistors
(JFETs) made of silicon carbide (SiC)
manufactured by SemiSouth Laboratories Inc. conventional IGBTs of silicon (Si) used
This is the main reason for the improvement”, commonly today, particularly for higher reverse
explained Prof. Bruno Burger, leader of the voltages. The main reasons are the breakdown
Power Electronics Group at Fraunhofer ISE. “In field strength, which is ten times higher for SiC
addition, we have optimised the gate units and than Si, and the band gap, which is three times
many other details of the circuit.” larger for SiC than Si.
The world record was measured for a complete Inverters convert the DC current generated by
PV inverter, including its internal power supply, photovoltaic systems into AC current and feed it
a digital signal processor (DSP) for controls, an into the public AC electricity grid. The higher
LCL grid filter and a relay for connection to the the inverter efficiency, the higher is the system
grid. Further advantages result when the yield. For a 30 kW system, an efficiency value
improvements are transferred to series which is 1 % higher results in an additional yield
production: Higher efficiency means lower over ten years of 3000 kWh or 1300 Euros. The
thermal losses, smaller cooling devices and a Fraunhofer Institute for Solar Energy Systems
more compact construction. These savings also ISE is a world leader in the field of PV inverters.
help to compensate the higher price for the new More than 25 years ago, its engineers
components. presented the first transformerless inverter and
have continued to develop this technology
Bruno Burger stated, “I see enormous potential further up to the present. In the meantime, it
for the new silicon carbide transistors. They are has become fully established for solar power
constantly becoming better and less expensive, generation.
whereas the costs for passive components,
which contain significant amounts of copper SemiSouth Laboratories Inc. was founded as a
and other metals, are rising continuously.” spin-off of Mississippi State University in 2002.
The next steps toward application in series It is a leading enterprise in the development of
production include further testing of the semiconductor components based on SiC. The
components and adaptation of the circuits and work to improve the inverter efficiency was
switching frequencies to the new specifications. supported by the German Federal Ministry for
Finally, field tests are planned to demonstrate the Environment, Nature Conservation and
viability in practice. Nuclear Safety (BMU) within the project entitled
“Ultra-compact PV inverters with silicon carbide
SiC transistors are significantly better than the semiconductors and high efficiency values”.
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