Climate change, driven by the reliance on traditional energy sources, has prompted the need for environmentally friendly production methods like wind and photovoltaic power generation. While these renewable energy sources reduce carbon emissions, their intermittent nature causes supply-demand imbalances. Conventional solutions, such as increased energy storage and fossil fuel use, present sustainability and cost challenges. This paper introduces a novel system integrating Electric Spring (ES) and Onboard Charging (OBC) technologies to stabilize the electrical grid and ensure a consistent battery energy supply. An advanced control method is proposed to mitigate the harmonic effects induced by the ES system and the grid bus, enhancing the power quality of Critical Loads (CLs). The paper details the ES-OBC system topologies, a cutting-edge control strategy integrating the Second-Order Generalized Integrator (SOGI) to refine CL voltage Total Harmonic Distortion (THD) and direct current control paired with harmonic suppression techniques. Supported by mathematical formulations and simulation results, the proposed system demonstrates practical applicability and significant advantages in real-world scenarios. The findings underscore the potential impact of the ES-OBC system on future grid stability and energy management, offering valuable insights into advanced control strategies for integrating renewable energy sources.