Short-Term Scheduling of Integrated Power and Spinning Reserve of a Wind-Hydrothermal Generation System with AC Network Security Constraints

The world energy matrix has diversified and has become a mix of hydroelectric, thermoelectric and renewable sources, such as wind energy. However, wind power is uncertain and variable, and its random intermittence leads to great challenges in coordinating it with a large hydrothermal system, for example. These questions require increased availability of spinning reserve as a solution to reduce the risk of deficit in moments when there is no wind power generation. This spinning reserve must be appropriately allocated between the hydraulic and thermal generating units so that, when necessary, they will be available and operational. To carry out this adequate allocation, besides considering the conventional operational limits of a problem of generation dispatch, it is also necessary to take into consideration the limits of the interchange lines that connect the subsystems that compose the electric network. So, in cases of congestion of these transmission lines, the subsystem itself can supply its spinning reserve under different hydrological conditions. Thus, this work proposes a mathematical formulation to dispatch power generation and allocate spinning reserve simultaneously, considering different hydrological day-ahead conditions. To do this, a nonlinear and dynamic optimal power flow is modeled, which, in addition to performing the active and reactive power dispatch of a hydrothermal system (including electrical and energy restrictions) for a day-ahead horizon, is also capable of carrying out an optimal allocation of the spinning reserve (hydraulic and thermal). The model is tested using a system of 33 buses to represent the system of the southern region of Brazil. © 2017, Brazilian Society for Automatics--SBA.