Large-signal stability analysis of DC distribution systems with cascading converter structure

Abstract

DC–DC converters are major components of the dc distribution systems. The converters interface with external power inputs, internal dc buses, and loadings of subsystems. The interfacing dc–dc converters should be stable locally and globally under mutual interactions through a dc bus within the system. Current research efforts have focused on the analysis of the stability of the dc distribution system subject to small-signal disturbance. However, in practice, the system routinely operates under large-signal disturbances, such as when an additional subsystem is turned on after being connected to the dc bus. In this scenario, the small-signal model may fail to fully describe the dynamics of the system. In this article, we identify and analyze the bifurcation process when the system undergoes abrupt load changes. According to the nonlinear operation of the interconnected system, a large-signal stability criterion is derived. This criterion is simple and can be easily extended to multiple connected converter systems. The criterion is also consistent with the result from bifurcation analysis. Finally, the validity of the proposed criterion is verified by the full-circuit simulations and the experimental works.