Analysis and Modeling of Self-Powered Cascaded Resonant Switched Capacitor Power Supply for Medium-Voltage DC Systems

DC power grid is considered as the future trend for distribution networks. However, the pure medium-voltage direct current (MVdc) grid faces great challenges in designing power supplies with high-voltage input but small power output requirements. The continuous power supply from the MVdc bus typically requires power converters with complex circuit structures and control algorithms. This article presents a power supply with a simple circuit structure for MVdc systems. The proposed power supply is comprised of cascaded standardized submodules to cope with high-voltage input and reduce the isolation requirement, and the voltage balance of all dc-link capacitors can be ensured with submodules operating independently. A start-up strategy and a simple self-powering strategy for the proposed converter are proposed in this article, and the average current model is established to characterize the proposed power supply. To verify the analysis, an average model and a switching model are constructed and simulated in Simulink and a 600-W prototype comprised of five submodules is built and tested to validate the design, and the maximum input voltage can reach 2700 V.