  We propose an optimal operation control strategy for an electro-thermal
microgrid. Compared to existing work, our approach increases flexibility by
operating the thermal network with variable flow temperatures and in that way
explicitly exploits its inherent storage capacities. To this end, the microgrid
is represented by a multi-layer network composed of an electrical and a thermal
layer. We show that the system behavior can be represented by a discrete-time
state model derived from DC power flow approximations and 1d incompressible
Euler equations. Both layers are interconnected via heat pumps. By combining
this model with desired operating objectives and constraints, we obtain a
constrained convex optimization problem. This is used to derive a model
predictive control scheme for the optimal operation of electro-thermal
microgrids. The performance of the proposed operation control algorithm is
demonstrated in a numerical case study.
