Discrete-Time Distributed Secondary Control for DC Microgrids via Virtual Voltage Drop Averaging

DC microgrids have been widely applied in industrial applications recently due to their robust reliability, high efficiency, and flexible accessibility to sustainable energy resources. Various distributed secondary control methods have been developed for DC microgrids to achieve current sharing and voltage restoration. However, the majority of these methods are presented with continuous-time controllers while digital controllers in real systems are in discrete time. Considering the inherent discrete-time property in practical implementations, this paper proposes a discrete-time distributed secondary control strategy. Using the concept of 'virtual voltage drop,' the proposed controller guarantees flexible current sharing and ensures accurate voltage regulation. Moreover, the proposed strategy allows for both resistive loads (linear loads) and constant power loads (CPLs, nonlinear loads). Both simulation and experiments are conducted to demonstrate the presented strategy.