Power Talk for Multibus DC MicroGrids: Creating and Optimizing Communication Channels

Abstract

We study a communication framework for nonlinear multibus DC MicroGrids based on a deliberate modification of the parameters of the primary control and termed power talk. We assess the case in which the information is modulated in the deviations of reference voltages of the primary control loops and show that the outputs of the power talk communication channels can be approximated through linear combinations of the respective inputs. We show that the coefficients of the linear combinations, representing equivalent channel gains, depend on the virtual resistances of the primary control loops, implying that they can be modified such that effective received signal-to-noise ratio (SNR) is increased. On the other hand, we investigate the constraints that power talk incurs on the supplied power deviations. We show that these constraints translate into constraints on the reference voltages and virtual resistances that are imposed on all units in the system. In this regard, we develop an optimization approach to find the set of controllable virtual resistances that maximize SNR under the constraints on the supplied power deviations.

Decentralized DC Microgrid Monitoring and Optimization via Primary Control Perturbations

“…The model above defines the input-output relation of a real, linear, synchronous communication channel with channel vector given by the gradient h n (evaluated at the nominal droop values) which contains the real coefficients of the equivalent linear channels that controller n sees to the other controllers; in localized and strongly connected MGs, the entries in h n do not differ significantly (see also [33]), i.e., the channel ( 18) experiences strong all-to-all property.…”

“…The scheme suits well channels with strong all-to-all property, i.e., channels where the gains in h k do not differ significantly; this is the case for small and localized MGs. As the system grows in size and scope, the all-to-all property ceases to be valid and one should consider applying more sophisticated digital modulation/demodulation and scheduling schemes, including error protection coding; see[32],[33] for alternatives.…”