Investigation and Assessment of Stabilization Solutions for DC Microgrid With Dynamic Loads

Several studies have been conducted to investigate the interaction dynamics of direct current (dc) microgrids supplying tightly regulated converters, which behave as constant power loads (CPLs). However, the presence of loads with open-loop control or of small closed-loop bandwidth (dynamic loads) in dc microgrids have not been studied to date. To fill this gap, this paper presents a comprehensive stability assessment of a dc microgrid with a high penetration level of dynamic loads. Unlike CPLs, it has been found that dynamic loads would dramatically affect the overall system stability margin at low-power demand than at rated power condition. Therefore, three solutions are proposed to mitigate the stability problems considering different operating and installation scenarios that a system integrator/designer may encounter. Moreover, the impact of system uncertainties, such as dc feeder length, bus capacitance, and the droop controllers, on system stability with/without the stability enhancement methods, is thoroughly addressed. Time-domain simulation studies based on nonlinear models are conducted to validate the analytical results. Furthermore, hardware-in-loop real-time simulation studies demonstrate the feasibility of the hardware implementation.