A New Switched-Capacitor Five-Level Inverter Suitable for Transformerless Grid-Connected Applications

Abstract

Transformerless grid-connected inverters have been extensively popular in renewable energy-based applications owing to some interesting features such as higher efficiency, reasonable cost, and acceptable power density. The major concern of such converters is the leakage current problem and also the step-down feature of the output voltage, which causes a costly operation for a single-stage energy conversion system. A new five-level transformerless inverter topology is presented in this study that is able to boost the value of the input voltage and can remove the leakage current problem through a common-ground architecture. Here, providing the five-level of the output voltage with only six power switches is facilitated through the series-parallel switching of a switched-capacitor module. Regarding this switching conversion, the self-voltage balancing of the integrated capacitors over a full cycle of the grid's frequency can be acquired. Additionally, to inject a tightly controlled current to the local grid, a peak current controller-based technique is employed, which can regulate both the active and reactive power support modes. Theoretical analyses besides some experimental results are also given to corroborate the correct performance of the proposed topology.