The increasing integration of renewable energy sources like wind and solar energy in the existing power grid is extremely challenging for conventional power plants. Actually, power plant operators have to shift their focus onto flexibility and grid stabilization rather than base load supply. Since the changes in the energy market have not been foreseeable when constructing the currently existing power plants, they are facing load scenarios they were not designed for. Consequently, the theoretically applicable ancillary services are often unused or are only available at particular loads. In cooperation with the University of Rostock, FVTR developed a full-physical digital clone of the entire power plant. Besides the main heat exchangers and steam turbine stages, the complete boiler with its fuel and flue gas system has been modelled in a one-dimensional discretisation scheme. The focus of this project was the simulation-based identification of internal storages for optimization and extension purposes regarding the ancillary services. To ensure the outstanding accuracy of the simulation results with respect to the real measurements even at extremely dynamic operation, the majority of the unit control has been implemented as a high detailed block-arranged structure. In addition to the successful identification of thermal storages, we performed a control parameter optimization as a feasibility analysis for our customer. This was to increase the quality of his prequalification curve and additionally to enhance the marketable amount of secondary control output by approximately 35 %.