A Distributed Control Strategy for Coordination of an Autonomous LVDC Microgrid Based on Power-Line Signalling

In a MG, an energy management control is essential in order to handle the variety of prime movers which may include different types of renewable energy sources (RES) and energy storage systems (ESS). Specifically, the recharging process of secondary battery, the most prominent ESS, should be done in a specific manner to preserve its life-time, common MG bus voltage must be kept within the bounds and the energy offered by RES should be utilized as efficiently as possible. This paper proposes a method for coordination of an autonomous low-voltage direct-current (LVDC) MG that consists of a number of sources using power-line signaling (PLS), a distributed control strategy in which the units inject sinusoidal signals of specific frequency into the common bus in order to communicate with each other. The control structure that allows the application of this method is revealed and the optimal range of operating PLS frequencies is specified. In order to achieve a zero steady-state error of injected signals in the common bus, primary control of batteries has been extended with dedicated proportional-resonant (PR) controllers that are switched on only during injection period. Finally, a method for coordination among the units using the PLS concept was developed and experimentally tested, confirming its applicability for autonomous LVDC MGs.