Voltage-Frequency Droop Scheme for Standalone Hybrid Microgrids

The concept of hybrid microgrid is gaining attention as it offers advantages of both dc and ac systems. The interlinking converter (ILC) is a critical element in this grid as it manages bidirectional power and regulates global variables. This paper presents a voltage-frequency droop scheme for ILC in a standalone hybrid microgrid. The goal is to map any voltage deviations at dc bus to ac bus frequency variations so that both grids can adjust power accordingly to satisfy the loads. The voltage-frequency droop coefficient is defined by the ratio of two scaling factors. Compared to other primary control schemes of hybrid microgrid, the proposed strategy allows us to define the amount of power change in ac/dc grid owing to a load change in dc/ac gird. This is particularly significant for grids with different power generation capacities. Simulations performed in PSCAD/EMTDC confirm the validity of the scheme.