Impedance-Based Stability of Grid-Connected DC Distribution Power Systems: AC- and DC-Side Stability Criteria, Equivalence, and Difference

The impedance-based stability analysis methods for ac or dc electronic power systems are always separately reported. Even in hybrid ac-dc systems, few studies adopt both ac and dc stability criteria simultaneously, let alone discuss their correlation and differences. In this article, the small-signal stability of grid-connected dc distribution power systems is investigated at both ac and dc sides. First, by modeling the system's input-to-output transfer functions, two equivalent-minor-loop-gain-based stability criteria without right-half-plane (RHP) poles are proposed, and their equivalence is mathematically proved. Then, the existing subsystems-based stability criteria are further proven to be equivalent to each other and to the equivalent-minor-loop-gain-based stability criteria. Meanwhile, the differences of all the aforementioned stability criteria are analyzed and discussed. Finally, sufficient case studies and experiments validate the proposed methods and viewpoints.