Startup Implementation in Universal Power Electronics Interface with Dual-Standard Output for DC Microgrid Applications

This work studies soft start implementation in the universal power electronics interface (UPEI) with dual-standard output for dc microgrid applications (350/700V). It is based on a series-resonant converter designed to operate with quality factors below unity at a constant switching frequency. It must pre-charge output capacitors to prevent inrush current and false triggering of protection devices when connecting to a dc microgrid. This work proposes a soft start implementation method to limit the inrush currents by implementing a simple PI-based topology morphing control. Also, it requires an extra safety switch added between the output capacitors of the converter and the output dc port. This paper compares converter startup operation with/without the soft start by initial charging of its output capacitor. The verification of the proposed strategy has been performed using PSIM.