Single-Stage Three-Level Inverter Approach for Connecting High Voltage Batteries to the Grid

The cost effectiveness and energy efficiency of AC-coupled high voltage battery systems depend on the power electronics that are needed to connect the battery to the grid. In most cases two-stage designs are used to convert the battery DC voltage to the desired AC grid voltage. This paper discusses the requirements and dependencies for a single-stage approach that can save costs and increase system efficiency.

To connect batteries to the AC grid, in most cases two power electronic components are used: an AC/DC inverter that is connected to the grid and a DC/DC converter that adapts the battery voltage window to the required DC link voltage of the AC/ DC inverter. As most DC/DC converters can cover a wide input voltage range, the benefits of this two-stage design are the flexibility of the number of in-series connected cells and therefore the voltage window of the battery used. The downside of the
two-stage design includes the additional hardware costs and the loss of efficiency within the DC/DC converter. One way to optimize this system is to try to eliminate the DC/DC converter and connect the battery directly to the DC link of the AC/DC inverter.