An improved model-based interlink converter control design in hybrid AC/DC microgrids

In hybrid AC/DC microgrids, a bidirectional interlink converter (IC) connecting the AC subgrid and DC subgrid is controlled to manage proper power sharing between both subgrids. This study proposes the design scheme of a model-based IC controller for frequency and voltage regulation of connected subgrids. System identification is used to estimate the state-space model representing the hybrid AC/DC microgrid dynamics. A step response is applied to observe the hybrid microgrid dynamic where the IC power is considered as the input while the output is the deviation of voltage or frequency in each subgrid. As the system characteristics in grid-connected mode and islanded mode might be different, the active power and reactive power transfer schemes are designed specifically for each operating mode to improve the performance of IC controller. According to simulation results, it is verified that an efficient gain scheduling by model-based gain tuning can deal with various operating conditions.