The integration of renewable energy sources such as photovoltaic (PV) systems into the power grid demands robust and efficient control strategies to ensure reliable and stable operation. In PV applications, Maximum Power Point Tracking (MPPT) is essential for extracting maximum available power. While conventional PI controllers are widely used due to their simplicity, they often suffer from limitations such as slow dynamic response, sensitivity to parameter variations, and poor disturbance rejection, making them less effective in rapidly changing environmental conditions. This study presents an improved MPPT approach combining an adaptive step-size P&O algorithm with Super Twisting Sliding Mode Control (ST-SMC) for a 100 kW PV system using a DC-DC boost converter. ST-SMC, a non-linear control technique, offers strong robustness against system uncertainties and external disturbances. The proposed method significantly enhances dynamic performance, providing fast response (9.22%) with minimal overshoot, reduced settling time, and near-zero steady-state error (0.002%), even under sudden irradiance changes. Simulation results demonstrate the superiority of the proposed approach over the conventional PI-based control technique, particularly in terms of MPPT efficiency (99.99%) from 1000 to 200 W/m2, transient response, and system stability. This study highlights the potential of advanced non-linear control methods in improving the reliability and performance of PV power conversion systems.