Utilizing Dual Active Bridges to Integrate Battery Storage Systems into Medium Voltage MMC STATCOMs - A Feasibility Study

Over the coming decades, a significant number of high power battery storage systems will be integrated in electric grids to support the transition to renewable electricity generation. Currently, these storage systems are restricted to low voltage levels, but must be connected to medium or high voltage grids. As such, loss and cost efficient bidirectional converters for battery-grid connection are essential for the development of competitive battery storage systems. This study assesses the feasibility of a topology in which batteries are connected to the submodules of a Modular Multilevel Converter (MMC) topology via dual active bridges (DABs). Converter simulations enable the design of the dual active bridges and an efficiency comparison to conventional low voltage battery storage systems is provided. Results from the feasibility study indicate that, under the specified design constraints, the proposed inverter has an efficiency in the range of conventional battery storage systems.