In single-phase grid-connected photovoltaic (PV) systems, maintaining a constant input power while dealing with a pulsating output power is a crucial challenge. This isolation is typically achieved using an energy storage element, most commonly a high-voltage DC link capacitor. The AC array structure of such systems consists of a single solar array connected to the grid through an inverter. Since the inverter's operational lifespan should align with that of the solar array, the choice of capacitor plays a critical role in system reliability. Electrolytic capacitors, despite their cost-effectiveness, exhibit a significantly shorter lifespan than solar arrays, necessitating the use of high-cost film capacitors with enhanced durability. A key challenge in designing the DC link voltage controller is mitigating voltage fluctuations in the capacitor and suppressing second harmonic ripple, both of which are inversely related to capacitor capacity and, consequently, system cost. Traditional approaches often require large capacitors to reduce these fluctuations, leading to increased cost and bulkiness. This paper proposes a digital control strategy for stabilizing the DC link capacitor voltage in single-phase grid-connected PV systems. The proposed method employs a low-pass finite impulse response (FIR) filter, which effectively suppresses voltage oscillations while maintaining system efficiency. The digital implementation of this controller enhances flexibility, reliability, and cost-effectiveness compared to conventional analog controllers. Simulation and experimental results demonstrate the effectiveness of the proposed approach in reducing voltage ripple and improving the stability of the DC link, thereby extending the lifespan of the inverter and enhancing overall system performance.