采用双向半主动钳位结构的改进型HERIC式并网光伏逆变器

Abstract While transformerless inverters provide several advantages, ground leakage current poses a quality risk related to performance and a safety concern, particularly in traditional inverter topologies. Careful design along with mitigation techniques are crucial to addressing this issue, as mandated by international regulations. In an effort to minimize ground leakage current, researchers have developed various transformerless inverter configurations. Of these, the H5, H6, and HERIC topologies have established themselves as the most prevalent and widely adopted. However, despite boasting the highest efficiency, the HERIC inverter suffers from severe common-mode (CM) behavior issues caused by parasitic junction capacitance in its switches, mandating a bulky CM choke at the output. This study proposes a refined HERIC inverter, named the RHERIC-BSAC inverter, to address the CM voltage fluctuations that occur during zero-voltage freewheeling periods in the HERIC inverter. The proposed RHERIC-BSAC inverter topology utilizes a novel bidirectional semi-active clamp circuit with two MOSFETs, eliminating the dead time problem unlike traditional active clamping circuits. By keeping the CM voltage at the center of the DC input consistent throughout the entire grid cycle, this design significantly reduces the ground leakage current to its 50 Hz component upon being connected to the electrical grid. Moreover, the proposed inverter enhances efficiency by suppressing leakage current, delivering a full three-level output voltage, and enabling reactive power injection. The superiority of the proposed solution’s performance over the original HERIC design was confirmed through a series of MATLAB/Simulink simulations and subsequent experimental validations.