News

7 August 2009

 

SemiSouth helps drive Fraunhofer ISE’s PV inverters to world record efficiency

Germany’s Fraunhofer Institute for Solar Energy Systems (FISE), based in Freiburg, says it has set a world record of 99.03% for the efficiency of inverters used in photovoltaic systems. By using new components and improving circuit technology, FISE researchers have reduced losses compared to their own previous top-level performance by a third.

“We now use junction field-effect transistors (JFETs) made of silicon carbide (SiC) manufactured by SemiSouth Laboratories Inc. This is the main reason for the improvement”, said Prof Bruno Burger, leader of the Power Electronics Group at FISE. “In addition, we have optimised the gate units and many other details of the circuit.”

The record was measured for a complete PV inverter, including its internal power supply, a digital signal processor for controls, an LCL grid filter and a relay for connection to the grid.

According to the researchers, further advantages result when the improvements are transferred to series production, where higher efficiency means lower thermal losses, smaller cooling devices and a more compact construction. These savings also help to compensate for the higher price for the new components. 

“I see enormous potential for the new silicon carbide transistors. They are constantly becoming better and less expensive, whereas the costs for passive components, which contain significant amounts of copper and other metals, are rising continuously,” says Burger.

The researchers add that SiC transistors are significantly better than conventional silicon (Si) IGBTs, particularly for higher reverse voltages. The main reasons are the breakdown field strength, which is ten times higher for SiC than Si, and the band gap, which is three times larger for SiC than Si.

Inverters convert the DC current generated by photovoltaic systems into AC current and feed it into the public AC electricity grid. The higher the inverter efficiency, the higher is the system yield. For a 30 kW system, an efficiency value which is 1% higher results in an additional yield over ten years of 3000 kWh or EUR 1300.00.

The work was supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) within the project entitled “Ultra-compact PV inverters with silicon carbide semiconductors and high efficiency values”.

See related items:

SemiSouth receives SBIR contract to develop new class of high-speed JFETs

Fraunhofer ISE sets PV inverter efficiency record

Search: SemiSouth SiC JFETs Inverters

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