A Modified Switched-Capacitor Based Seventeen-Level Inverter with Reduced Capacitor Charging Spike for RES Applications

Abstract

This article presents a grid-connected system for renewable energy source (RES) applications. The proposed system consists of a modified switched-capacitor (SC) based multilevel inverter and a DC-DC flyback converter. By using the DC-DC flyback converter the voltages of DC-link capacitors are adjusted to the same values. This modified SC-based multilevel inverter has benefits like limited capacitor charging spike, reasonable size, power density, cost per output power, active and reactive power support, adjusted injected current to the grid, and reduced number of input power DC supplies. Two isolated DC sources are generated using a flyback converter to supply the SC-based inverter and increase the number of voltage levels produced at the output. In this topology, one of the most important problems of the switched capacitor, i.e., the occurrence of the inrush currents during charging capacitors, is solved by using a circuit unit that consists of an inductor with a parallel power diode in the capacitive charging current path. To confirm the performance of the presented structure, comprehensive experiments and comparisons are provided. In the experiments, the peak current control (PCC) method is applied to control both the active and reactive power injected into the grid by the modified 17-levels grid-connected inverter.