System Integration for Grid-scale Hybrid Battery Technologies

In this work, a modular and open-source platform has been developed for integrating hybrid battery energy storage systems that are intended for grid applications. Alongside integration, this platform will facilitate testing and optimal operation of hybrid storage technologies. Here, a hardware testbed and a control software have been designed, where the former comprises commercial Lithium-iron-phosphate
$(LiFePO_{4})$
and Lead Acid (Pb - acid) cells, custom built Dual Active Bridge (DAB) DC-DC converters, and a commercial DC-AC conversion system. In this testbed the batteries have an operating voltage range of ~11-15V, the DC-AC conversion stage has a DC link voltage of 24V, and it connects to a
$\boldsymbol{208}\mathbf{V}3-\phi$
grid. The hardware testbed can be scaled up to higher voltages. The control software is developed in Python, and the firmware for all the hardware components is developed in C. This software implements hybrid charge/discharge protocols that are suitable for each battery technology for preventing cell degradation, and perform uninter-rupted quality checks on selected battery packs. The developed platform provides flexibility, modularity, safety and economic benefits to utility-scale storage integration.