A modified hierarchical control structure for
distributed generation (DG) in microgrid is applied in accordance
to the recommendations by the IEEE Std. 1676. In
the inverter control layer, a generalized control algorithm
is developed to enable the DGs to operate in all three
modes (i.e., grid-forming, grid-feeding, and grid-supporting
modes) with a single control structure, facilitating the
seamless transition between the operating modes. This
feature is obtained by designing the multiloop controller in
the inverter control layer using inverse plant modeling techniques
so that the dynamics of the inverter and the LC filter
are fully compensated, virtually transforming the controlled
DG in the unity gain from the application layer perspective.
Thus, effects of disturbances associated with the mode
transitions are thus fully eliminated. The effectiveness of
the proposed control algorithm is validated by numerical
simulations and hardware-in-the-loop experiments. The results
show that the DGs can fulfill the tasks defined in the
system control layer with fast dynamics, desired accuracy,
and good transient behavior