P3R: Partial Power Postregulated Grid-Forming Converter for Prosumer DC Buildings

This article introduces a concept based on a step-up/down series partial power converter to perform droop control in dc grid-forming converters for buildings. Being responsible for processing all the power between the dc building and the grid, the high efficiency of this converter is essential. This study investigates the feasibility of combining two high-performance solutions-series-resonant dc-dc (DCX) converter, which features a constant voltage transfer ratio of 700/350 V and a partial power postregulator ((PR)-R-3) that follows the droop control curves for prosumer dc buildings. In this application, the DCX is required to ensure isolation between ac and dc parts as required by standards for residential dc installations while also providing the necessary voltage matching. A 5-kW prototype was built and tested to evaluate the performance and effectiveness of the concept. The results show that (PR)-R-3 can provide the required output voltage regulation with an efficiency of around 99%, resulting only in minimal impact on the overall system efficiency. The realized dc grid-forming converter comprising DCX and (PR)-R-3 features an overall efficiency of 96.5% at rated power, with a very flat efficiency curve, presenting a promising solution instead of frequency, or duty-cycle controlled SRC, which results in lower efficiency at high power.