The Hybrid Modular Multilevel Converter with Embedded Supercapacitor Energy Storage System (MMC-SESS) combines the advantages of the Modular Multilevel Converter (MMC) and energy storage system, making it highly suitable for large-scale integration of renewable energy sources. Compared with the conventional Hybrid MMC, the Hybrid MMC-SESS not only retains DC fault ride-through capability but also supports bidirectional active power exchange with the grid, thereby enhancing system stability and reliability. However, the Hybrid MMC-SESS features a complex structure, and its detailed model (DM) is computationally intensive, leading to low simulation efficiency. To accelerate simulation, this paper develops an equivalent model (EM) for the Hybrid MMC-SESS. First, topology analysis of the submodule (SM) is performed, and its companion circuit is established using discretization based on the trapezoidal integration method. Next, EMs of the SM and the arm are established based on the Nested Fast Solution Method (NFSM) and Thévenin equivalent modeling approach. The EM of the Hybrid MMC-SESS is then derived according to series and parallel relationships. Finally, DM is implemented in PSCAD/EMTDC. Comparative verification is conducted between the proposed EM and the DM, including steady-state operation and DC fault scenarios. The results demonstrate that the EM achieves excellent simulation accuracy and computational efficiency.