Design of a Robust Free-Running Solar Inverter Power Conversion Unit for Instantaneous Backup with Near-Sinusoidal Output

This paper presents a small, scalable, and affordable solar-powered inverter system, designed to provide a continuous power supply in off-grid settings and during grid outages worldwide. The proposed system utilizes lithium-ion batteries charged by solar energy to power a high-efficient and low power dissipation inverter constructed using durable power transistors, a step-up transformer, and a custom-designed filter circuit. The inverter generates a near-sinusoidal AC output capable of supporting a wide range of loads, thereby reducing dependency on fuel-generated grid electricity, particularly in underserved regions. The system emphasizes cost-free energy storage and reducing energy losses within components. It maintains a stable near-sinusoidal voltage under practical load conditions. The modular design integrates energy conversion, storage, and AC power delivery into a unified system. With a Total Harmonic Distortion (THD) of only 2.17%, the inverter delivers high-quality voltage output with a near-sinusoidal waveshape at lower complexity compared to conventional systems. The system is suitable for mobile applications, emergency supply of power during outages, disaster relief, and rural electrification. The proposed solution demonstrates the accessibility and effectiveness of solar technology in practical, real-world applications.