A Low Distortion Collaborative Modulation for Zero-Crossing Distortion Pseudo DC Link Single-Stage Isolated Inverter

Zero-crossing distortion (ZCD) is an inherent defect that exists in pseudo dc link single-stage isolated inverters (PDL-SII) based on unidirectional dc–dc converter, leading to reduced output current quality. Despite its significance, the topic has received limited attention in the literature. The ZCD mechanism of PDL-SII is quantitatively analyzed in this letter. In addition, a novel low distortion collaborative modulation is proposed to suppress the PDL-SII ZCD issue by operating the rear-stage unfolder in high frequency during zero-crossing and thus enabling a conduction path for the reverse current. Both simulation and experimental results fully confirm the theoretical analysis.