An <i>LCL</i> Type Single-Stage Inverter Based on Accurate Time-Domain Modeling With Line-Cycle-Weighted Loss Optimization Design Strategy

Pseudo-DC-link single-stage isolated inverter (PDL-SII) based on conventional resonant DC-DC converter suffers from narrow voltage gain range and the resultant low-gain range output distortion. To solve this issue, a novel PDL-SII based on LCL resonant converter is proposed in this paper. Due to the excellent voltage step-down performance of LCL converter, the proposed PDL-SII features full range zero voltage switching characteristic and requires pulse frequency modulation only. The time-domain analysis of the LCL converter is carried out, and the operation principle and mode distribution of the LCL converter is derived. To optimize the efficiency of the LCL converter based PDL-SII, a novel line-cycle-weighted loss optimization design strategy, integrating voltage and current stresses, soft-switching range and gain range, is proposed in this paper. Different from the traditional design strategy in DC-DC application, the proposed design strategy considers the weighted average loss over the whole line cycle, which is more suitable for PDL-SII application. Simulation model and a single-stage LCL based inverter are built to verify the accuracy of the time domain analysis and the parameters. The total harmonic distortion rate of the prototype is 2.1% and the peak efficiency of the converter is up to about 96.8%.