Consensus based Ideal Current Sharing Controller for DC Microgrid

Distributed secondary controllers in dc microgrid are used for low voltage regulation and proportional current sharing among the source converters. These controllers depend on the calculation of global average of the source voltages and ideal value of the current that each source must share. These values are usually calculated using an all-to-all communication network which is not easily scalable. In this paper, ideal current sharing based controller is extended for reduced communication network. For each converter, the presented method involves a consensus-based ideal current estimator and average voltage estimator. The error between these estimates with respect to the current/voltage of the converter is used to modify its droop characteristic. In literature, it is shown that similar performance can be achieved even in the presence of a reduced communication network by using higher values of weights on communication links. As the information communicated among the sources is discrete, higher values of weights may lead to unstable operation. In this paper, an upper bound is determined on the range of weight. Roots loci plots are used to show the effect of variation in weights of communication links in a given communication graph on small signal stability of the system. The efficacy of consensus based controller is validated using detailed simulation studies in Matlab/Simulink.