SBIR-STTR Award

This project seeks to advance the prediction, monitoring, and control of solar power production and the capabilities of solar power electronics. The proposed new technology will provide string inverters for utility-scale photovoltaic farms having higher power ratings and higher power density, with a path to reduced cost and increased U.S. manufacturing competitiveness. The technology will contribute to grid reliability and will reduce the balance of system costs. The project will develop a transformational solar string inverter technology to achieve new levels of power (250 kW) at high power density and efficiency. Key components of this technology are new circuit approaches that take advantage of the emerging commercial silicon-carbide power transistors, new high-frequency high-power magnetic elements, and new controllers that take advantage of the high frequencies possible with silicon-carbide power devices. The significant improvement in string inverter power density opens a new path for the reduction in solar plant inverter and operating and maintenance costs. Phase I will demonstrate a proof-of-concept inverter module at the 20 kW level, to retire risks and to provide efficiency and loss data that will refine and calibrate theoretical loss models. These results will be employed to further optimize the 250 kW design. Phase I will include detailed circuit design, printed circuit board design, prototype fabrication, and testing. Based on the results of Phase I, the Phase II project will develop and test a full 250 kW prototype string inverter. This testing will employ the facilities of the Energy Systems Integration Laboratory at the National Renewable Energy Laboratory. Successful completion of Phase II will enable Phase III, in which the string inverter will be certified, field tested, and commercialized for use in utility-scale solar installations.

This project seeks to develop a new disruptive power electronics technology for solar power inverters that is manufacturable in the USA, provides a path to significant reductions in specific cost, leverages recent technological advances in silicon carbide (SiC) power MOSFETs, and develops a new proprietary inverter approach that realizes these goals. The new technology will provide compact string inverters for utility-scale photovoltaic farms having higher power ratings and higher power density, with a path to reduced cost and increased U.S. manufacturing competitiveness. The technology can contribute to grid reliability and will reduce the balance of system costs. The project will develop the BREK250™, a compact 250 kW string inverter product based on a new photovoltaic string inverter technology that leverages emerging SiC MOSFET technology to achieve transformational advances in cost, power density, efficiency, and reliability. The Phase I project led to a 125 kW prototype that was tested at the NREL Energy Systems Integration Facility, and that demonstrated the feasibility of using SiC switching modules for photovoltaics inverters capable of operating at higher temperatures and power densities than current Si-only technology. CEC efficiency in the 98.5% to 99% range was demonstrated. During Phase II, we will develop and demonstrate the full power electronics of a 250 kW string inverter, including modules and control algorithms not addressed in Phase I. This includes neutral-balancing circuitry, EMI filters, closed-loop current control, and improved optimization of efficiency via novel control algorithms. We will work with contract manufacturers to refine the accuracy of our bill of materials, assembly cost, and cost vs. volume. Phase II will culminate with testing of a 250 kW prototype string inverter at the NREL Energy Systems Integration Facility (ESIF), including measurement of operating characteristics and CEC efficiency. The project will provide compact three-phase 1500 V string inverters for large-scale domestic commercial and utility scale solar power installations.