Stationary energy storage system based on modular high voltage battery modules

This paper focuses on the design and control of a stationary energy storage system based on multiple modular high voltage battery modules. The system achieves bi-directional power flow directly from 400V dc grid to the 12V battery modules via a bi-directional dc-dc converter with high conversion ratio as an interface. One merit of such a system is its extensibility and scalability for higher power rating for future use by dispatching more battery modules together. A 2kWh energy storage system prototype which is made up by one grid-connected solid state transformer (SST) emulator and two bi-directional dc-dc converters are designed, fabricated and tested. Based on the modified droop control, a double-loop digital control system for the SST emulator and a single-loop digital control system for the dc-dc converter are implemented respectively. At last, experimental results are presented to verify the proposed distributed control strategy.