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<p>As photovoltaic plants scale up and trend toward medium-voltage grid interconnection, conventional MV interfaces that combine a line-frequency transformer and a three-phase inverter suffer from bulky magnetics, high maintenance cost, and limited grid-current waveform quality. This paper proposes a three-phase, high-frequency-link (HFL), quasi-single-stage MV PV grid-connected inverter and a feedforward-decoupled grid-current closed-loop control strategy. Each phase is composed of M identical submodules connected in parallel at the input and in series at the output. Each submodule integrates a phase-shifted full-bridge HFL isolation stage and a line-frequency polarity-reversal bridge. Moreover, the submodule-side LC components together with a single external grid-side inductor form an inherent cascaded LCL-like filter, achieving harmonic attenuation comparable to a conventional LCL filter with reduced external passive components. The modulation, grid-interfacing control, steady-state operating principle, and high-frequency switching waveforms are analyzed, including ZVZCS soft-switching characteristics and duty-loss mechanisms. A 500VA 12-20VDC/190VAC50Hz laboratory prototype is built for concept validation and safety testing. Owing to the modular parallel-input/series-output architecture and per-phase identical control, the proposed topology and control can be scaled to higher voltage and power levels after redesign of device ratings, isolation, and control parameters.</p>

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A quasi-single-stage three-phase medium-voltage grid-connected inverter with high-frequency isolation for photovoltaic application

  • 期刊论文

  • 发表日期：

    2026年3月9日

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  • Sicheng An,
  • Jiaqi Sun,
  • Jiahui Jiang,
  • Zhihao Liang

摘要

As photovoltaic plants scale up and trend toward medium-voltage grid interconnection, conventional MV interfaces that combine a line-frequency transformer and a three-phase inverter suffer from bulky magnetics, high maintenance cost, and limited grid-current waveform quality. This paper proposes a three-phase, high-frequency-link (HFL), quasi-single-stage MV PV grid-connected inverter and a feedforward-decoupled grid-current closed-loop control strategy. Each phase is composed of M identical submodules connected in parallel at the input and in series at the output. Each submodule integrates a phase-shifted full-bridge HFL isolation stage and a line-frequency polarity-reversal bridge. Moreover, the submodule-side LC components together with a single external grid-side inductor form an inherent cascaded LCL-like filter, achieving harmonic attenuation comparable to a conventional LCL filter with reduced external passive components. The modulation, grid-interfacing control, steady-state operating principle, and high-frequency switching waveforms are analyzed, including ZVZCS soft-switching characteristics and duty-loss mechanisms. A 500VA 12-20VDC/190VAC50Hz laboratory prototype is built for concept validation and safety testing. Owing to the modular parallel-input/series-output architecture and per-phase identical control, the proposed topology and control can be scaled to higher voltage and power levels after redesign of device ratings, isolation, and control parameters.