The proposed generalized control algorithm, implemented
in the inverter control layer, enables the DGs to operate in
all three modes without changing the control structure in the
inverter control layer and seamlessly transitioning between the
operating modes. The latter feature is obtained by designing the
multiloop controller in the inverter control layer in such a way
that the closed-loop dynamics of the inverter, together with the
LC filter, present unity gain. Thus, the disturbances associated
with the mode transitions are fully canceled. In contrast to
the complex algorithms usually found in literature, the design
process of the proposed controller is very simple and requires
only a reasonable knowledge of the LC filter and decoupling
inductance parameters. The stability of the proposed method
has been discussed as well, and proper controller parameters
are well tuned. Other studies such as the influence of highfrequency
harmonics of the grid current to the proposed inverter
control algorithm and the sensitivity analysis regarding
the parameter mismatch have been included and discussed in
detail. The effectiveness of the proposed control algorithm is
validated by numerical simulations and HIL experiments. More
importantly, a comparison of the proposed algorithm with the
conventional method in the inverter level demonstrates that the
proposed method has better reference tracking, less overshoot,
and faster dynamics during the transition between different
operation modes; therefore, a superior performance is achieved
with the proposed method.