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<p>In photovoltaic (PV) DC collection systems, variations in solar irradiance lead to significant fluctuations in the output power of PV arrays, which in turn affects the efficiency of the LLC resonant converter in the system, especially under light-load conditions where efficiency degradation is more pronounced. A novel hybrid modulation (NHM) method based on a full-bridge LLC resonant converter is proposed in this paper, with the aim of improving the overall efficiency across the entire load range of the converter, particularly under light-load conditions. The NHM method consists of two modulation modes: one is the conventional pulse frequency modulation (PFM) mode, and the other is the mixed resonant frequency modulation (MRFM) mode. The MRFM mode is realized by inserting series and parallel resonant cycles into the PFM. The two modulation modes can be smoothly transitioned between one another, while maintaining the voltage gain constant, ensuring good dynamic response performance of the converter. By adjusting the duration of the two modes, the effective load current can be varied for different load conditions, thereby improving the efficiency of the converter across the entire load range. An experimental prototype with an 80&#xa0;V input and 200&#xa0;V/2 A (400&#xa0;W) output has been built to validate the feasibility and effectiveness of the proposed modulation method.</p>

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Entire load range efficiency improvement for LLC resonant converters applied to photovoltaic power generation

  • 期刊论文

  • 发表日期：

    2026年2月23日

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  • Huakun Bi,
  • Chuijie Meng,
  • Weike Li,
  • Shuchen Yao

摘要

In photovoltaic (PV) DC collection systems, variations in solar irradiance lead to significant fluctuations in the output power of PV arrays, which in turn affects the efficiency of the LLC resonant converter in the system, especially under light-load conditions where efficiency degradation is more pronounced. A novel hybrid modulation (NHM) method based on a full-bridge LLC resonant converter is proposed in this paper, with the aim of improving the overall efficiency across the entire load range of the converter, particularly under light-load conditions. The NHM method consists of two modulation modes: one is the conventional pulse frequency modulation (PFM) mode, and the other is the mixed resonant frequency modulation (MRFM) mode. The MRFM mode is realized by inserting series and parallel resonant cycles into the PFM. The two modulation modes can be smoothly transitioned between one another, while maintaining the voltage gain constant, ensuring good dynamic response performance of the converter. By adjusting the duration of the two modes, the effective load current can be varied for different load conditions, thereby improving the efficiency of the converter across the entire load range. An experimental prototype with an 80 V input and 200 V/2 A (400 W) output has been built to validate the feasibility and effectiveness of the proposed modulation method.