Abstract：Energy transmission in key scenarios, such as DC microgrids, electric vehicles, and energy storage, relies on DC-DC converters with high-power, high-voltage conversion ratios, and high efficiency. Among mainstream circuit topologies, the dual-active-bridge (DAB) converter and the LLC resonant converter are the most widely used. Although the DAB converter has the capability of wide-range voltage regulation, it suffers from inherent issues, such as limited soft-switching range, circulating power loss, and large turn-off current stress. As a result, its operating efficiency over a wide voltage and power range is relatively low. The LLC-Buck/Boost two-stage topology can meet the need for wide-range voltage regulation, but the two-stage power conversion process significantly reduces overall system efficiency. The LLC-DAB converter, which combines the LLC and DAB converters, can achieve high efficiency and wide voltage gain simultaneously, attracting significant attention in recent years. In high-capacity application scenarios, adopting the input-parallel output-parallel (IPOP) configuration for multiple DC-DC converters is a practical and effective way to expand the system capacity. However, due to unavoidable deviations in each module's circuit parameters, current or power imbalance among modules will occur. Extensive research has been conducted on current-sharing technologies for IPOP-type LLC resonant converters and IPOP-type DAB converters, including both active and passive current-sharing methods. Nevertheless, research on current sharing for IPOP systems with LLC-DAB converters as submodules is rare, and the mechanism for such systems remains unclear. First, this paper systematically establishes a simplified equivalent circuit model of the LLC-DAB converter, analyzes its intrinsic voltage-regulation principle and power-control mechanism, and rigorously derives the mathematical model of a single LLC-DAB converter. Then, based on the mathematical model of a single module, a comprehensive current-sharing error model for the IPOP parallel system is established. Second, the intrinsic relationships among the current sharing of LLC-DAB modules, the current sharing of sub-units, and the power balancing of sub-units are analyzed. It is found that, even when stable current sharing is achieved at the module level in the IPOP-type LLC-DAB converter, an obvious power imbalance persists among the sub-units within each module. A three-loop control strategy for synchronous current-power balancing is proposed, and its implementation mechanism is analyzed. Finally, a two-phase 1.2 kW experimental platform for parallel operation of LLC-DAB converters is built. The experimental results show that the current-sharing performance of the IPOP-type LLC-DAB converter system is mainly determined by the degree of mismatch in the series inductor parameters of the DAB sub-units. The resonant parameters of the LLC sub-units have little impact on the current-sharing performance. Under different input/output voltage conditions and load operating conditions, the proposed strategy enables the parallel system to stably achieve current sharing among modules and power balancing among sub-units simultaneously.
孙志峰, 陈炎堃, 庞赫, 曾进辉, 兰征. 输入并联输出并联LLC-DAB变换器电流-功率同步均衡三环控制策略[J]. 电工技术学报, 2026, 41(10): 3381-3395.
Sun Zhifeng, Chen Yankun, Pang He, Zeng Jinhui, Lan Zheng. Current Power Synchronous Balancing Three Loop Control Strategy for Input Parallel Output Parallel LLC-DAB Converter. Transactions of China Electrotechnical Society, 2026, 41(10): 3381-3395.
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2026, Vol. 41 
