  One of the most important challenges facing an electric grid is to
incorporate renewables and distributed energy resources (DERs) to the grid.
Because of the associated uncertainties in power generations and peak power
demands, opportunities for improving the functioning and reliability of the
grid lie in the design of an efficient, yet pragmatic distributed control
framework with guaranteed robustness margins. This paper addresses the problem
of output voltage regulation for multiple DC-DC converters connected to a grid,
and prescribes a robust scheme for sharing power among different sources. More
precisely, we develop a control architecture where, unlike most standard
control frameworks, the desired power ratios appear as reference signals to
individual converter systems, and not as internal parameters of the system of
parallel converters. This makes the proposed approach suited for scenarios when
the desired power ratios vary rapidly with time. Additionally, the proposed
control framework is suitable to both centralized and decentralized
implementations, i.e., the same control architecture can be employed for
voltage regulation irrespective of the availability of common load-current (or
power) measurement, without the need to modify controller parameters. The
control design is obtained using robust optimal-control framework. Case studies
presented show the enhanced performance of prescribed optimal controllers for
voltage regulation and power sharing.
