Optimized Phase-shift Tuning via Equivalent Small Parameter Modeling for Ripple Reduction in Asymmetric Parallel Multi-Module DC-DC Converters

Abstract

In photovoltaic power generation applications, multiple low-voltage PV modules must be boosted and connected in parallel for high power output. However, due to the variability of PV energy input, the parallel DC-DC converter modules often operate under asymmetric conditions, which deteriorates bus voltage ripple and reduces system stability and component lifespan. To address these issues, this paper proposes an optimal phase-shift modulation method with asymmetric phase shifts to effectively suppress the ripples at the point of common coupling of parallel-connected converters. To do so, a model for the output voltage ripple of boost and buck–boost parallel converter is established using the equivalent small parameter method (ESPM) with the optimal phase-shift angle determined by this modulation approach. Furthermore, a triple-loop current-sharing control strategy is implemented to ensure current sharing among the modules, enhancing the overall ripple suppression capability of the proposed modulation technique. Simulation and experimental results indicate that this integrated approach significantly improves the performance and stability of parallel converter systems.