Discrete-Time Modeling, Stability Analysis, and Active Stabilization of DC Distribution Systems With Multiple Constant Power Loads

This paper presents the stability analysis of dc distributed power systems with multiple converter-controlled loads. The load converters are tightly controlled, behaving as constant power loads with low-damped $LC\;$ filters. The dynamic behavior of the system in high frequency range is often not studied with the classical tools based on conventional averaging techniques. However, dc power systems with the reduced size filter, and consequently, the high resonant frequency, are widely used in transportation applications. In this paper, the stability analysis of the system is established based on a discrete-time model of the system, taking into account the switching frequency and intrinsic nonlinearities of the system model. The impacts of the filter parameters and interactions among the constant power loads are investigated with the proposed discrete-time method. Moreover, an active stabilizer is developed and included in the dynamic model of the system, in order to extend the stability margin. The theoretical observations are then validated experimentally on a laboratory hardware prototype.