This paper presents the design and modeling of a hybrid energy storage system (HESS) for a grid-connected photovoltaic (PV) application. The proposed system integrates batteries and supercapacitors to address the inherent variability of solar power generation and to enhance grid stability. A boost converter is employed to regulate and elevate the PV output voltage, while a maximum power point tracking (MPPT) algorithm based on the incremental conductance method ensures optimal energy extraction under varying environmental conditions. The system is interfaced with the grid through a three-phase voltage source inverter controlled by pulse width modulation (PWM). The hybrid storage configuration combines the high energy density of batteries with the high power density of supercapacitors, enabling efficient management of both low-frequency and transient power fluctuations. A bidirectional DC–DC buck–boost converter with PI-based control is used to coordinate charging and discharging processes. Simulation results demonstrate that the proposed system effectively reduces power fluctuations, minimizes grid dependency during peak demand, and improves overall system reliability. Furthermore, the hybrid approach alleviates battery stress, thereby extending its operational lifetime. The study confirms that integrating hybrid energy storage significantly enhances the performance and stability of grid-connected PV systems.