  In this paper, we propose a minimax model predictive control (MPC)-based
energy management system that is robust with respect to uncertainties in
renewable infeed and load. The MPC formulation includes a model of low-level
droop control with saturation at the power and energy limits of the units.
Robust MPC-based energy management systems tend to under-utilize the renewable
energy sources to guarantee safe operation. In order to mitigate this effect,
we further consider droop control of renewable energy sources. For a microgrid
with droop-controlled units, we show that enhancing droop feedback with
saturation enlarges the space of feasible control actions. However, the
resulting controller requires to solve a mixed-integer problem with additional
variables and equations representing saturation. We derive a computationally
tractable formulation for this problem. Furthermore, we investigate the
performance gained by using droop with saturation, renewable droop and
combination of both in a case study.
