The operation schedule of the power generation units in electrical power systems is determined by the optimisation problem known as unit commitment (UC), aiming at minimising the total cost considering the generation constraints. To obtain a feasible solution from the network perspective, the security-constrained UC (SCUC) problem has been defined to embed the network constraints in the optimisation problem as well. Also, the higher penetration of renewable energy sources (RES) has increased the difficulty of UC problem, mainly due to the uncertainty and the high variability of RES. This paper proposed a SCUC with economic dispatch (SCUCED) optimisation developed in two stages. The first one is the solution of a merit-order based zonal day-ahead market (ZDAM) optimisation to define a preliminary generation schedule. In the second stage, the SCUCED is solved based on AC load flow routines and sensitivity factors to embed the full network representation. The approach is applied to a modified version of the IEEE 39-bus test system.

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The dispatch schedule of the electrical power plant units is the result of the solution to the unit commitment optimisation problem, and it minimises the cost of production considering pre-defined technical limits. The security-constrained unit commitment problem has been defined as including the network constraints in the previously mentioned optimisation problem to obtain a feasible power system solution. The traditional security-constrained unit commitment methods are based on the DC-power flow model, where the network losses and voltage magnitudes are neglected in the problem formulation. This paper proposed a bi-stage security-constrained unit commitment with an economic dispatch (SCUCED) optimisation problem. A merit-order-based zonal day-ahead market problem is solved in the first stage to define a preliminary generation commitment. In the second stage, the SCUCED is solved based on the AC-power flow model and sensitivity factors to embed the full network representation in the optimisation problem. In this paper, the proposed method is illustrated by an application to a modified version of the IEEE 39-bus test system.@en