Smaller, lighter power converters with SiC

Smaller, lighter power converters with SiC

Technology News |
By Christoph Hammerschmidt

The physical properties of silicon carbide power semiconductors (SiC) make it possible to realize very fast and low-loss unipolar device concepts such as MOSFETs or Schottky diodes even for high blocking voltages such as in photovoltaic inverters. These properties make it possible to use inverter circuits with considerably higher clock frequencies and at the same time reduce losses. In the case of photovoltaic inverters, a significantly higher power density can be achieved because the weight and cost-determining magnetic elements can now be designed much smaller. Savings can also be made on the heat sink as another volume-driving element.

Together with partners from industry, the Fraunhofer Institute for Energy Economics and Energy System Technology IEE in Kassel has developed a demonstrator of a PV inverter with 30 kVA power, which demonstrates the advantages of SiC semiconductors in the application, in the state-funded research project PV-LEO. In conventional inverter systems that operate at typical clock frequencies of 17 kHz, the choke components and cooling account for up to 50% of the total weight of the system.

By increasing the clock frequency to 50 kHz, the weight of the choke components could be roughly halved. Due to the smaller size of the chokes, however, additional heat dissipation measures must be taken during assembly to avoid hotspots within the components.

The achieved power-to-weight ratio of the newly developed overall system is 0.93 kg/kW. By using SiC semiconductors, a significant weight reduction can be achieved compared to the state of the art (2.3 kg/kW on average). In a follow-up project, the partners are striving to achieve a further reduction in weight.

Despite considerably higher expenditures for SiC semiconductors, an improvement in the cost position for the manufacturer of these systems can already be achieved at system level. Therefore, a very fast penetration of the new SiC technology within this area of application is expected.

Among those involved in the research consortium were Kaco new energy GmbH (coordination), Fraunhofer IEE, Infineon, and SUMIDA Components & Modules GmbH.

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