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<p>Bimodal transformerless inverters are widely adopted due to their compact design and high efficiency, but they face challenges such as grid current distortion due to mode switching and the secondary ripple power inherent in single-phase systems. This paper proposes a sliding mode control method for the bimodal inverter to achieve smooth switching and power decoupling. For existing control, there is mode switching between different circuit modes, which leads to grid current distortion. In the proposed control strategy, mode switching can be avoided. Then the grid current quality is enhanced. Furthermore, the secondary ripple issue is an inherent phenomenon of single-phase inverters. To address this issue, the intermediate capacitor voltage is controlled to swing to buffer the secondary pulsating power. This reduces the necessity for a large decoupling capacitor, improving the power density of the system. First, this paper introduces the operation modes and switching states of the bimodal inverter in detail. Then controllers for the currents and voltage are introduced. Moreover, the selection criteria for the inductors and capacitors along with the power loss analysis are presented. The effectiveness of the proposed approach is confirmed through experimentation on a 400 W prototype.</p>

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Control strategy for bimodal transformerless inverters for improving the grid current and power density

  • 期刊论文

  • 发表日期：

    2025年9月8日

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  • Wentao Li,
  • Yonglu Liu,
  • Weiquan Feng,
  • Liang Yuan

摘要

Bimodal transformerless inverters are widely adopted due to their compact design and high efficiency, but they face challenges such as grid current distortion due to mode switching and the secondary ripple power inherent in single-phase systems. This paper proposes a sliding mode control method for the bimodal inverter to achieve smooth switching and power decoupling. For existing control, there is mode switching between different circuit modes, which leads to grid current distortion. In the proposed control strategy, mode switching can be avoided. Then the grid current quality is enhanced. Furthermore, the secondary ripple issue is an inherent phenomenon of single-phase inverters. To address this issue, the intermediate capacitor voltage is controlled to swing to buffer the secondary pulsating power. This reduces the necessity for a large decoupling capacitor, improving the power density of the system. First, this paper introduces the operation modes and switching states of the bimodal inverter in detail. Then controllers for the currents and voltage are introduced. Moreover, the selection criteria for the inductors and capacitors along with the power loss analysis are presented. The effectiveness of the proposed approach is confirmed through experimentation on a 400 W prototype.