Design Methodology of Three-Phase LLC Charger Based on Time-Domain Model With Enhanced Analytical Accuracy and Power Efficiency

Three-phase LLC converters show considerable potential in battery chargers. However, existing parameter design methods for three-phase LLC converters have limitation in analytical accuracy and efficiency optimization over the wide voltage range. To address the above issues, this article proposes a time-domain model (TDM)-based design method for three-phase LLC chargers. Firstly, a comprehensive TDM for the three-phase LLC converter is developed, providing a detailed analysis of operating modes and mode distributions across the entire operating range. Then, based on TDM, a novel design method is proposed to optimize the efficiency of the entire charging process. The resonant root-mean-square (rms) current is selected as the optimization objective, and its relationship with design parameters is researched to derive the optimal constraints. Meanwhile, suitable operating modes are identified for each charging pattern to satisfy the soft-switching condition. A step-by-step design procedure is finally provided to determine the optimal parameters. The analysis proves that the proposed design methodology enhances accuracy and efficiency across the entire operating range of the three-phase LLC charger. The effectiveness is also validated through a 4.5-kW experimental setup with 98.1% peak efficiency.