Comparison of single and two stage topologies for interface of BESS or fuel cell system using the ABB standard power electronics building blocks

The two most popular topologies used to interface the DC voltage sources such as battery energy storage systems (BESS), fuel cells with the AC network are the single and two stage topologies. In case of the single stage topology the BESS or the fuel cell system is directly connected to the dc link of a voltage source converter and the voltage source converter is interfaced to the low voltage grid with a transformer. A two-stage solution is realized using a DC-DC conversion stage followed by a DC-AC conversion stage. The DC-DC stage boosts the DC voltage so that the DC-AC stage can be directly interfaced to the low voltage grid. Detailed comparison of these topologies is carried out using battery voltage and the installed power as variables. The commercially available ABB standard Lopak PEBB´s are used for comparison of the topologies. Both solutions are offered by ABB mainly depending on the dc voltage level of the BESS