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In this paper, the operation of electrical, heat and gas networks with flexible energy hubs is presented, where hubs is contributed in energy market that is based on market clearing price. This scheme maximizes the difference between energy hubs profit and operation cost of generation units subjected to operation model of sources, storages and responsible load in hub format, flexibility limits of hubs, and optimal power flow model of energy networks. This formulation is based on market clearing price model, so that it obtain value of energy price according to balancing between the generation and demand in different buses if energy networks. Penalty function method in this paper uses to calculate of primal variables and some dual variables (energy prices). In the following, the stochastic optimization uses to model the uncertainties of load and renewable power. Finally, the obtained numerical results show the capabilities of the proposed scheme in the improving flexibility and economic situations of hubs. Also, optimal operation of hubs is able to improve the economic and operation induces of energy networks in comparison to load flow study, and it improves the social welfare based on reducing of energy price. So that 100% flexibility condition obtains for Hubs. In this condition, the operation cost, energy loss, voltage drop and temperature drop are reduced about to 19.8%, 7.1%, 19.5% and 16.7%, respectively, with respect to load flow analysis, but the pressure drop increases about to 4.9%. [ABSTRACT FROM AUTHOR]

Power management in microgrids is a major challenge due to its low total inertia and capacity. The lower the microgrid generation capacity is, the higher the share of each generation unit in total power will be, and the higher the frequency deviation in less time will be when an outage occurs. So, preventive actions can be more reasonable and affordable than corrective actions for microgrid power and frequency control. In this regard, a new primary frequency response-constrained unit commitment model is presented here to prevent excessive frequency deviations by more commitment of higher inertia power plants and more contribution of renewable energy resources or energy storage systems' fast inertia response. To have a mixed-integer linear programming model, the primary frequency response constraints are linearized. The model is solved by the combination of two commercial solvers named MOSEK and YALMIP in the MATLAB 2018 environment. The proposed model is examined on a real isolated microgrid (an island). The results show that by activating the primary frequency support of distributed energy resources, the power can be managed with lower costs because there will be less need to start up fast (and expensive) gas turbine generation units. In addition, although comparing the model with others shows the more expensive management procedure, better frequency stability is obtained in contingencies. [ABSTRACT FROM AUTHOR]