Discrete-time modelling, stability analysis, and active stabilization of dc distribution systems with constant power loads

This paper presents the stability analysis of a dc distribution system supplying multi-converter loads. The load converters are tightly controlled, behaving as constant power load with low damped LC input filters. The dynamic behavior of the system in high frequency range is often not studied with the classical tools based on average linearization. Whereas, small LC filters with high cutoff frequency are common in transportation systems. Therefore, in this paper, the stability analysis of the system is established based on a discrete-time model of pulse width modulated converters considering the switching effect and intrinsic nonlinearities of the system. The impacts of the filter parameters and interactions among the loads are investigated with the discrete-time method. Moreover, an active stabilizer is included in the system model in order to extend the stability domain. Experimental results, conducted on a dc distribution system, are given in order to validate the analytical stability analysis and stabilizer.