Implementation of Hierarchical Control in DC Microgrids

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

“…Oppositely, the tertiary (and also the secondary when present) requires information about the status of other/all units to operate properly. There is extensive literature on defining the upper level control mechanisms and optimization algorithms, including the type and the format of the information messages that should be exchanged among the units and (possibly) to a central controller [6][7][8][9][10][11][12]18,23,24]. An interesting result is presented in [24]; there, besides showing how to implement the optimal dispatch (standard control application on the tertiary level) in a distributed manner without a central controller, the authors also rigorously show that the sufficient information that is necessary to optimally assign duties to each DER is the average values of the disposable power, the power demand and the power cost in the system.…”

“…The design approach where the feedback loops of the optimal controllers are enabled by an external communication system inherently reduces the reliability of the control system. In contrast, recent approaches for MG control avoid (crucially) relying on external communication networks [6][7][8] equivalent, whose parameters determine the channel state and can be estimated, enabling the design of power talk constellations that perform optimally in terms of symbol error probability.…”

From DC nano- and microgrids towards the universal DC distribution system - a plea to think further into the future

“…In LVdc, different communication methods are used for different applications. In [14], wireless communication is implemented for dc grid control. Moreover, wireless communication is a common practice in stand-alone PV [15], dc LED lighting [16] and parallel dc/dc converters for current sharing [17].…”

On Secondary Control Approaches for Voltage Regulation in DC Microgrids

“…The secondary control approach has been carried out to compensate the voltage drop due to the droop method. Secondary regulators can be implemented with either a centralized or a decentralized control policy [8], [11]- [15]. In both cases, the secondary controller should regulate the dc voltage of the MG.…”