Evaluation of DC-DC-converter impedance passivity using pseudo-random test signals

DC microgrids have recently attracted attention from academic and industrial research since they offer a multifunctional and efficient way to locally interconnect energy resources as well as loads. By applying the DC link voltage as an ubiquitous accessible parameter for all components, defined low-flow conditions both under grid-tied and islanded operation can be realized using voltage droop curves. However, due to lacking system inertia stabilizing conventional AC grids, stability of a DC microgrid entirely depends on the control loop setup and grid-side passive components of its power electronic converters. In the following, the passivity-based stability criterion is selected as design basis. A simple analytical way to set up droop-controlled power electronic converters for stable grid operation is introduced. Lastly, the chosen approach is verified in a practical trial by complex impedance measurements using pseudo-random test signals.