Effects of instantaneous constant-power loads on DC micro-grids for sustainable power systems

This paper discusses stability issues in dc micro-grids with cascade distributed architectures. In these architectures point-of-load converters behave as instantaneous constant-power loads to line regulating converters located upstream. Constant-power loads introduce a destabilizing effect into a dc micro-grid that may cause its main bus voltages to show significant oscillations or to collapse. Mitigating strategies such as load shedding, use of linear and nonlinear (geometric) controllers, or addition of resistive loads, filters or energy storage directly connected to the main bus are explained. Advantages and disadvantages of these methods are discussed and the analysis is verified through simulations and experiments with prototypes.