Communication-Theoretic Model of Power Talk for a Single-Bus DC Microgrid

Abstract

Power talk is a method for communication among voltage control sources (VSCs) in DC microgrids (MGs), achieved through variations of the supplied power that is incurred by modulation of the parameters of the primary control. The physical medium upon which the communication channel is established is the voltage supply level of the common MG bus. In this paper, we show how to create power talk channels in all-to-all communication scenarios and implement the signaling and detection techniques, focusing on the construction and use of the constellations or arbitrary order. The main challenge to the proposed communication method stems from random shifts of the loci of the constellation symbols, which are due to random load variations in the MG. We investigate the impact that solutions that combat the effects of random load variations by re-establishing the detection regions have on the power talk rate.

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

“…where ∆p vr n is the power deviation due to deviations in the virtual resistances ∆r n , see (21), while ∆p rv n (t) are the power deviations related to the reference voltage deviation ∆x n (t), n = 1, ..., N , see (12), respectively. In the proposed communication scheme, the virtual resistances are fixed to their optimized values, such that p n n + ∆p vr n is the power supplied by VSC m in absence of the reference voltage deviations.…”

“…The previous works [8]- [12] investigated the performance of power talk in presence of random load changes, when standard communication techniques, such as line-coding and pilot-sequence based training are applied. In addition, [8]- [12] focused on a simple single bus DC MG system where the effect of the distribution lines can be ignored and all units observe the same output. In this paper we expand the analysis of power talk in several ways, as elaborated below.…”

“…The power talk communication channel shows some challenging properties that are not commonly encountered in communication systems: i) non-linear input-output relation, ii) configurations of primary controllers of all communicating units jointly determine the values of the observed channel outputs, i.e., voltage/power levels of MG buses, iii) configurations of primary controllers are also jointly subject to constraints in terms of the allowed supplied power deviations, and iv) dependence of the channel outputs on the configuration of the rest of the system, i.e., distribution line impedances and the instantaneous values of the loads that change randomly. The previous works [8]- [12] investigated the performance of power talk in presence of random load changes, when standard communication techniques, such as line-coding and pilot-sequence based training are applied. In addition, [8]- [12] focused on a simple single bus DC MG system where the effect of the distribution lines can be ignored and all units observe the same output.…”