  Modern power systems are characterized by low inertia and fast voltage
dynamics due to the increase of sources connecting via power electronics and
the removal of large traditional thermal generators. Power electronics are
commonly equipped with fast controllers that are able to reach a desired
voltage setpoint within seconds. In this paper, we propose and compare two
approaches using Model Predictive Control (MPC) to compute optimal voltage
references for the power electronic devices in order to minimize the losses in
a DC microgrid: i) a traditional setpoint-tracking MPC which receives a
previously computed optimal setpoint; ii) an economic MPC which does not
require a priori computed setpoints. We show that the economic MPC outperforms
the setpoint-tracking MPC in simulations with the CIGRE benchmark system when
multiple load disturbances occur. Some insights and discussions related to the
stability of the closed-loop system using its dissipativity properties are
highlighted for both approaches.
