USA: Working to expand solar energy use and find an efficient and cost-effective way to address the natural intermittency of photovoltaic power, researchers at the National Energy Technology Laboratory (NETL) are using three-port transformers that enable combined solar and battery grid integration.
The three-port configuration allows 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, according to the press release from NETL.
According to the researchers, combined PV/battery grid integration helps manage solar power's variability by storing energy for future use, allowing for a constant average power delivery and smoothing voltage spikes.
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 kHz versus 60 Hz). Doing so makes them smaller and increases power density.
Prototype converters up to 10 kW were tested and demonstrated successful power flow, while converters of 30 kW and 50 kW are being built and tested.