Large Signal Stabilization at System Level Using Port-Hamiltonian System Theory for Modular Islanded DC Microgrids

Modularity and unknown transmission line impedances in dc microgrids contribute to increased uncertainty, complicating system-level large-signal stability analysis. Passivity theory is recognized as a promising solution to this challenge, as it simplifies the large-signal stability analysis of dc microgrids by decomposing it into the passivity analysis of individual converters. The interconnection and damping assignment passivity-based control (IDA-PBC) approach, widely adopted based on the port-controlled hamiltonian (PCH) model, ensures that converters exhibit passivity in a closed-loop configuration. However, existing IDA-PBC methods fail to achieve input–output port passivity, preventing system-level large-signal stability due to unmodeled electrical interconnections and subsystem interactions. Additionally, these methods introduce singularities at equilibrium points because the PCH model structure is altered when deriving the unique mathematical expression for the duty cycle. This article proposes an IDA-PBC approach based on reference modification to address these issues. This controller accounts for electrical input variations within the closed-loop PCH model to achieve input-to-output port passivity. Furthermore, the reference for the converters is reconstructed to derive a unique duty cycle expression without altering the closed-loop PCH model, thereby avoiding singularities at equilibrium points. Finally, the system-level large-signal stability of the proposed control is validated through experiments.