Discontinuous Modulation Scheme for a Differential-Mode Ćuk Inverter

The differential-mode Ćuk inverter (DMCI) is a single-stage inverter with low device count. It offers advantages over other topologies because of compactness, higher power density, and reduced cost. It is a promising topological configuration for renewable-/alternative-energy applications with isolated as well as nonisolated structures. The continuous modulation scheme (CMS), which was introduced originally for this inverter, activates all the modules of the DMCI. The new discontinuous modulation scheme (DMS) deactivates one module in each half line-cycle leading to discontinuous operation of modules. This paper outlines the DMS and a mechanism to realize it. The experimental open-loop and closed-loop results of the DMCI using CMS and DMS are provided along with a comparison of their performances. It is shown that, the DMS reduces the circulating power and hence mitigates the losses. The voltage ratings of the devices also are reduced with the DMS. In contrast, the CMS has wider linearity in its normalized dc-voltage gain and yields reduced harmonic distortion of the output voltage. For DMS, to achieve comparable linearity in normalized dc-voltage gain and distortion, harmonic compensation under closed-loop control is a pathway that has been demonstrated.