30kVA SiC demonstrator targets photovoltaic inverters

March 17, 2019 //By Christoph Hammerschmidt
Smaller, lighter power converters with SiC
A consortium of companies and research institutes has developed a demonstrator of a photovoltaic inverter with 30 kVA power, which illustrates the advantages of SiC semiconductors in the application. The achieved power-to-weight ratio of the newly developed overall system is 0.93 kg/kW - compared to an average of 2.3 kg/kW for conventional semiconductors.

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.

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