  This paper investigates the use of fractional order (FO) controllers for a
microgrid. The microgrid employs various autonomous generation systems like
wind turbine generator (WTG), solar photovoltaic (PV), diesel energy generator
(DEG) and fuel-cells (FC). Other storage devices like the battery energy
storage system (BESS) and the flywheel energy storage system (FESS) are also
present in the power network. An FO control strategy is employed and the FO-PID
controller parameters are tuned with a global optimization algorithm to meet
system performance specifications. A kriging based surrogate modeling technique
is employed to alleviate the issue of expensive objective function evaluation
for the optimization based controller tuning. Numerical simulations are
reported to prove the validity of the proposed methods. The results for both
the FO and the integer order (IO) controllers are compared with standard
evolutionary optimization techniques and the relative merits and demerits of
the kriging based surrogate modeling are discussed. This kind of optimization
technique is not only limited to this specific case of microgrid control but
also can be ported to other computationally expensive power system optimization
problems.
