On the Modeling of DC-DC Converters for Stability Assessment of DC Zeds on Ships

Advanced naval platforms are based on innovative DC distribution to enable reconfigurability during ship mission, and flexibility in use of cutting-edge pulsed loads. To this aim, zonal power grids are designed to ensure the stable supply of high-dynamics loads by means of controlled DC-DC power converters. A not perfect integration between converters' control bandwidths and filtering stages can be the cause of a strong reduction in stability margins, even forcing unstable behavior. The paper wants to provide a stability analysis on a cascaded DC system. Differently from the standard impedance approach, a mathematical modeling is instead envisaged in this work to properly ponder how the system stability (i.e. intersection on Gauss plane) depends from LC filters and feedback control loops. On an exemplifying system, a sensitivity analysis identifies the limit bandwidth conditions, later verified on HIL tests. Additional considerations also focus on offline measuring techniques to differently characterize the system impedances.