A frequency-based economical-sharing strategy for low-voltage DC microgrids

Abstract

This paper introduces a frequency-based control strategy to minimize the total generation cost in low-voltage dc microgrids. In dc microgrids, although the voltage is the only variable for controlling the outputs of sources, it is not a common variable for all sources due to the different line resistances. Hence, applying the conventional voltage-based droop control will not be able to share the load among the sources accurately. Within the context alluded above, to realize an accurate load sharing in dc microgrids, the communication-based approaches are employed. However, any link failure in these approaches may impair the controller functionality and consequently, render the whole system inoperable. To cope with the associated problems of the communication-based approaches, the frequency-based control strategy has been introduced for accurate load sharing in dc microgrids which operates without any communication network. This study proposes a frequency-based economical-sharing control strategy that has the capability to minimize the total generation cost and regulate the voltage of sources. The main advantage of this strategy over the previously addressed frequency-based strategies is providing an optimal combination of dispatchable sources to supply the required load on the grid. Through the employed control strategy, the incremental costs of all dispatchable sources will be equal in the steady state which causes the optimal operation of the dc microgrid. The small-signal modeling of the proposed strategy is also carried out to analyze the system stability and parameter sensitivity. A complete set of simulation studies is provided in PLECS software to verify the effectiveness of the proposed control strategy.