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<p>An LCL filter is an essential element in a grid-connected inverter, as it attenuates high-frequency switching harmonics and reduces total harmonic distortion (THD), ensuring grid current quality and compliance with harmonic standards. In order to ensure grid code compliance, it is crucial to design the LCL filter with consideration of the THD constraint. This paper presents a structural approach for designing an LCL filter in a grid-connected inverter, where targeting THD is considered as a design constraint. This design method is suitable for medium-power applications, as it does not use high switching frequency, which results in reduced switching losses and less thermal stress on power semiconductors. The design method focuses on the practical limitations of filter components and controller stability constraints. The inverter-side inductance is determined based on the allowable peak-to-peak ripple current on the inductor, and the filter capacitor is determined based on the power factor variation limit, whereas the grid-side inductance is designed based on the target THD of the grid-side current. Additionally, the designed parameters of the LCL filter ensure the stable operation of the current controller because the switching-to-resonance frequency ratio is within the limit ranges. The designed parameter is evaluated by implementing it in PLECS simulation and hardware-in-the-loop (HIL) experimentation with a 200&#xa0;kW grid-connected inverter. The designed THD target and the implemented THD results of implementing the LCL filter are closely matched at 2%, and the system meets the IEEE-519 standards.</p>

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LCL Filter Design for Medium Power Grid-Connected Inverter Considering THD Constraint and Control Stability

  • 期刊论文

  • 发表日期：

    2026年2月19日

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  • Chhaya Seng,
  • JoungJin Seo,
  • Myung-Hwan Min,
  • Hanju Cha

摘要

An LCL filter is an essential element in a grid-connected inverter, as it attenuates high-frequency switching harmonics and reduces total harmonic distortion (THD), ensuring grid current quality and compliance with harmonic standards. In order to ensure grid code compliance, it is crucial to design the LCL filter with consideration of the THD constraint. This paper presents a structural approach for designing an LCL filter in a grid-connected inverter, where targeting THD is considered as a design constraint. This design method is suitable for medium-power applications, as it does not use high switching frequency, which results in reduced switching losses and less thermal stress on power semiconductors. The design method focuses on the practical limitations of filter components and controller stability constraints. The inverter-side inductance is determined based on the allowable peak-to-peak ripple current on the inductor, and the filter capacitor is determined based on the power factor variation limit, whereas the grid-side inductance is designed based on the target THD of the grid-side current. Additionally, the designed parameters of the LCL filter ensure the stable operation of the current controller because the switching-to-resonance frequency ratio is within the limit ranges. The designed parameter is evaluated by implementing it in PLECS simulation and hardware-in-the-loop (HIL) experimentation with a 200 kW grid-connected inverter. The designed THD target and the implemented THD results of implementing the LCL filter are closely matched at 2%, and the system meets the IEEE-519 standards.