A Voltage-Controlled Split-pi Converter Interfacing a High-Voltage ESS with a DC Microgrid: Modeling and Experimental Validation

The Split-pi converter can be used for the bidirectional connection of an energy storage system (ESS) and a DC microgrid. It is common to have a DC bus voltage higher than the ESS voltage, but sometimes a high-voltage ESS is needed to satisfy current constraints and still reach high power levels. Therefore, in these scenarios, the grid-side voltage can be lower than the ESS voltage, for example, when the DC bus voltage is as low as 48 V. This paper presents a model of the Split-pi converter interfacing a high-voltage ESS to a low-voltage DC bus. In the three considered scenarios, the converter’s output voltage is the main controlled variable. A state-space model is developed accounting for the parasitic elements. Compared to the case of a Split-pi working with a DC bus voltage higher than the ESS voltage, the controllers’ design is more challenging due to the presence of the input LC filter. Finally, the proposed model is validated through simulations and experimental tests on a prototype implementation of the Split-pi converter.