System simulation is inherently an applied technology, driven by specific application demands. The Modelica language enables equation-based, system-level, multi-domain, and visual modeling, facilitating researchers conducting system simulation studies of nuclear power systems. This paper introduces the custom-built AESE library on the OpenModelica platform. Examples in AESE are provided to illustrate the development and simulation of system models for conventional pressurized water reactors (PWRs) and high-temperature gas-cooled reactors (HTGRs). The paper also describes tasks completed under different application scenarios, including hardware-in-the-loop simulation, multi-objective optimization, system identification, and rapid optimization, using model-driven and data-driven approaches with the AESE library. The further application of simulation models and data has significant practical and engineering value. This paper serves as a valuable reference for the intelligent application of energy system models in the context of advanced engineering challenges.