250 kW Solar String Inverter Using Silicon Carbide (SiC) Modular Architecture and Grid Support Functionality

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. DC-DC conversion to add dc-coupled battery storage to our revolutionary SiC solar string inverter technology is proposed. The add-on cost of the power electronics battery interface will be decreased from the current 4¢/W commercial state-of-the art to 1¢/W. This 4x reduction in capital cost will be achieved via our proprietary high-frequency SiC composite architecture technology and through integration of the dc-dc converter and dc-ac inverter functions into a single unit. The project will demonstrate full power prototype battery interfaces integrated into our inverters, and will support ongoing certification efforts. In the Phase II project, we have demonstrated increased output power (200 kW per MPPT zone, and 400 kW for the two-zone system) without significant increases in cost or size; this decreases our high-volume price to below $0.035/W and increases our power density to over 8 kW/kg. This significant advancement was achieved through further optimization of the magnetics, power stage design, and improved thermal management system. These demonstrated cost, power density, and power rating metrics significantly beat the commercial state of the art, and we believe they can be achieved with US manufacturing. The impact of BREK technology on the market is demonstrated by our signed licensing and development agreement with Yaskawa Solectria Solar to develop a 500 kW solar inverter to their specifications, based on the results of this SBIR project. Inverters will be fully manufactured in the U.S. BREK also has a signed licensing and development agreement with Emporia Energy to develop a bidirectional EV charger, based on the BREK core SiC inverter technology. To date, we have raised $750k in seed funding from Angel investors and the State of Colorado. We have received feedback from potential customers, leading to two primary recommendations: (1) obtain UL certification and begin product testing at customer sites, and (2) incorporate dc-side battery storage into the string inverter product. Hence, in Phase IIB, we propose to add SiC-based dc-dc conversion with bidirectional power flow to integrate battery storage interface functionality. In addition, we will extend our grid support functionality to meet the IEEE 1547 (2018) standard. These customer-driven changes, combined with IEEE/UL certifications, will enable BREK to fully commercialize this technology. The proposed project includes converter design and development, continued customer discovery, UL certification, customer site testing, and battery interface development, testing, and certification.