Realization of Parasitics in the Stability of Dc-Dc Converters Loaded by Constant-Power Loads in Discontinuous Conduction Mode

Constant power load (CPL) characteristics of tightly regulated dc-dc converters in multi-converter distributed power systems is equivalent to the dynamic negative impedance, destabilizing the dc bus and consequently the system. Various techniques have been developed to control ideal/lossless converters loaded by CPLs. Neglecting loss components simplifies the modeling and analysis. Loss components significantly enhance the stability of the cascaded converters. In this paper, effects of parasitics in behavior of dc-dc converters operating in discontinuous conduction mode (DCM) and loaded by CPLs are investigated. Design criteria are presented, which gives recommendations on the design of multi-converter dc power systems to avoid negative impedance instability. The proposed stable operation criteria are validated with hardware measurements and detailed simulation analyses.