  Congestion caused in the electrical network due to renewable generation can
be effectively managed by integrating electric and thermal infrastructures, the
latter being represented by large scale District Heating (DH) networks, often
fed by large combined heat and power (CHP) plants. The CHP plants could further
improve the profit margin of district heating multi-utilities by selling
electricity in the power market by adjusting the ratio between generated heat
and power. The latter is possible only for certain CHP plants, which allow
decoupling the two commodities generation, namely the ones provided by two
independent variables (degrees-of-freedom) or by integrating them with thermal
energy storage and Power-to-Heat (P2H) units. CHP units can, therefore, help in
the congestion management of the electricity network. A detailed mixed-integer
linear programming (MILP) optimization model is introduced for solving the
network-constrained unit commitment of integrated electric and thermal
infrastructures. The developed model contains a detailed characterization of
the useful effects of CHP units, i.e., heat and power, as a function of one and
two independent variables. A lossless DC flow approximation models the
electricity transmission network. The district heating model includes the use
of gas boilers, electric boilers, and thermal energy storage. The conducted
studies on IEEE 24 bus system highlight the importance of a comprehensive
analysis of multi-energy systems to harness the flexibility derived from the
joint operation of electric and heat sectors and managing congestion in the
electrical network.
