An integral approach for the synthesis of optimum operating procedures of thermal power plants towards better operational flexibility

Abstract

To deal with the challenge of a balance between the large-scale introduction of variable renewable energies and intermittent energy demand scenarios in the current electrical systems, operational flexibility plays a key role. The electrical system operational flexibility can be addressed from different areas such as power generation, transmission and distribution systems, energy storage (both electrical and thermal), demand management, and coupling sectors. Regarding power generation, specifically at the power plant level, operational flexibility can be managed through the cyclic operation of conventional power plants which involve load fluctuations, modifications in ramp rates, and frequents startup and shutdowns. Since conventional power plants were not designed to operate under cyclic operating schemes with involve fast response times, must develop these capabilities through the design of operating procedures that minimize the time needed to take the power plant from an initial state to the goal state without compromising the structural integrity of critical plant components. This thesis proposes a dynamic optimization methodology to the synthesis of optimum operating procedures of thermal power plants which determine the optimal control valves sequences that minimize its operating times based on techniques of dynamic simulation, metaheuristic optimization, and surrogate modeling. Based on such an approach, the power plants must be increasing its operational flexibility to address a large-scale introduction of variable renewable energies and intermittent energy demand scenarios. This thesis proposes a dynamic optimization framework based on the implementation of a metaheuristic optimization algorithm coupled with a dynamic simulation model, using the modeling and simulation environment OpenModelica and a surrogate model to estimate in a computationally efficient way the structural integrity constraint of the dynamic optimization problem. Two case studies are used to evaluate the proposed framework by comparing their results against information published in the literature. The first case study focuses on managing the thermal power plant's flexible operation based on the synthesis of the startup operating procedure of a drum boiler. The second case study addresses the synthesis of an optimum operating strategy of a combined heat and power system to improve the electric power system’s operational flexibility.