一种无需在每个开关上单独并联谐振电容的高效谐振直流链逆变器

Many existing resonant dc-link inverters incorporate separate shunt resonant capacitors for at least one switch. However, when the voltage across these capacitors exceeds zero, the accidental switching-on of the switches due to control disturbances in industrial applications can trigger a sudden discharge of the capacitors, resulting in electrical surges, increased switching-on losses, and potential false triggering of the driver IC protection. In addition, the efficiency of many existing resonant dc-link inverters under light-load conditions is inferior to that of hard-switching inverters. To address these issues, this article proposes a novel resonant dc-link inverter. The proposed design features simple auxiliary circuits placed on the dc link, which are activated prior to the main switches to reduce the dc-link voltage to zero, enabling zero switching loss for the main switches. Notably, none of the switches are equipped with separate shunt resonant capacitors, thereby preventing potential additional switching-on losses and false triggering of the driver IC protection in complex industrial environments. Furthermore, the reduction of the dc-link voltage relies solely on energy transfer between resonant capacitors, ensuring that only the load current flows through the auxiliary circuits during this process. This design minimizes losses in the auxiliary circuits and improves efficiency, particularly under light-load conditions. This article provides a detailed operational modal analysis of the inverter during a switching cycle and outlines the relevant design requirements. Experimental waveforms demonstrate that the switches achieve soft switching, and efficiency tests reveal that the novel inverter achieves up to 98% efficiency at rated operation. Moreover, the proposed inverter exhibits superior efficiency compared to existing designs, especially under light-load conditions. In summary, the key contributions of the novel resonant dc-link inverter are the elimination of separate shunt resonant capacitors for each switch, which mitigates potential switching-on losses, and the significant improvement in efficiency, particularly at light loads, compared to conventional resonant dc-link inverters.