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

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.