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

The Split-pi converter is a suitable choice to interface an electrical storage system (ESS) with a DC microgrid. Usually, the ESS voltage is lower than the grid-side voltage. However, due to current limits, the use of a high-voltage ESS is unavoidable when high power levels are required. In such cases, the ESS voltage can be higher than the microgrid voltage, especially with low microgrid voltages such as 48 V. The present work aims at modeling the Split-pi converter operating with an ESS voltage higher than the grid-side voltage in three typical microgrid scenarios in which the controlled variable is the converter's output voltage. The devised state-space model considers the parasitic elements and the correct load model for each scenario. It is shown that the presence of the input LC filter can make the design of the controllers more complicated with respect to those of a Split-pi operating with ESS voltage lower than grid-side voltage. Simulations and experimental tests on a lab prototype validated the study.