Modular Universal Converter for MVDC Applications

Abstract

This paper presents the design and build of a universal MVDC converter that can interface either LVAC or LVDC while providing bi-directional power flow and high-frequency isolation. The proposed universal MVDC converter module can serve as a building block for higher-voltage higher-power systems. The converter modules are based on the soft-switching solid-state transformer (S4T), realized using 3.3 kV SiC MOSFETs, and can provide integrated high-frequency isolation, low EMI through low dv/dt, and high efficiency over the full operating load range realized with soft-switching techniques. The topology, operating principle, control philosophy addressing challenges associated with modular converters including dynamic and steady-state voltage sharing between modules on the HV side, design and selection of components to realize a 50 kVA 5 kV DC to 600 V DC/480 V AC is presented. Simulation results verifying the operation of the MVDC converter are also presented.