Reliability Improvement of a Three-port Converter for Standalone PV-Battery Applications

Three-port converters are increasingly preferred for standalone PV?battery systems due to their versatility and multi functional operation, which allow the system to effectively miti gate the effects of intermittency in renewable power generation. However, their reliability is often lower than that of two-port converters, as they involve more components, experience higher thermal stress, require complex control algorithms, and operate in multiple modes. This paper investigates and evaluates the reliability of a three-port power converter under different oper ating modes using the MIL-HDBK-217F standard. Component level failure rates were analyzed, and design improvements were proposed to reduce stress and enhance performance. Based on the reliability analysis, a novel reliability-oriented control strategy is proposed to enhance the resilience of the standalone system. By implementing a State-of-Charge (SoC) based management algorithm, the converter avoids high-stress operating modes, such as the SISO PV-load mode, thereby extending the expected operational lifetime. The effectiveness of these improvements was verified through LTspice simulations and Scilab calculations, providing a robust validation method given that physical lifecycle testing requires extended operational durations. Results indicate a significant reduction in failure rates, improved system efficiency, and extended operational lifetime.