These Transformers Could Better Integrate Solar PV on the Grid
Researchers at the National Energy Technology Laboratory (NETL) are working to expand solar energy use while also finding an efficient and cost-effective way to address the natural intermittency of photovoltaic power.
With funding from the SunShot National Laboratory Multiyear Partnership (SuNLaMP) program, researchers are using three-port transformers that enable combined solar and battery grid integration.
The researchers say that combined PV/battery grid integration helps manage solar power's variability by storing energy for future use. This allows for a constant average power delivery and smoothing voltage spikes.
The three-port configuration allow a PV energy source to hook into the same transformer as an energy storage or battery device. The alternative would be to connect each energy source to separate AC-coupled transformers, then connect to the electric grid.
Transformer design can vary, but NETL researchers reconfigured the windings in such a way to maximize power flow and enhance flexibility. The transformers also transfer electrical energy at a higher frequency (10-50 kilohertz versus 60 hertz). Doing so makes them smaller and increases power density.
Estimates suggest an increase in power density by 10 times or more for commercial-scale installations as compared to traditional technologies.
Prototype converters up to 10 kilowatts (kW) were tested and demonstrated successful power flow, increased power density, and efficiencies approaching 99 percent versus traditional efficiencies of about 94 percent.
Converters of 30kW and 50kW are being built and tested. And simulations suggest the potential for successful operation of full-scale 1 megawatt combined solar/energy storage inverter for utility-scale grid-tie inverter applications.
Image Caption: Annotated image of the transformer design being tested by NETL. Credit: NETL.