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.