To address the challenges of heavy reliance on traditional power grids, high line losses, and limited renewable energy integration in highway energy supply systems, this paper proposes a “Source-Grid-Load-Storage” microgrid architecture based on flexible interconnection of distribution zones. A hybrid AC/DC system is developed, integrating distributed photovoltaic stations, energy routers, and energy storage devices, enabling dynamic capacity expansion and energy sharing across transformer areas. Using TRNSYS for thermal load simulation and HOMER for electrical load modeling, a coordinated photovoltaic-storage capacity optimization model is established. Engineering validation demonstrates that, under a 750 V DC bus configuration, the system achieves a photovoltaic self-consumption rate of 92%, reduces transformer overload risk by 37%, and lowers the levelized cost of electricity to 0.13 CNY/kWh. The results provide critical technical support for the development of green transportation infrastructures.