A Seventeen-Level Step-Up Switched-Capacitor-Based Multilevel Inverter With Reduced Charging Current Stress on Capacitors for PV Applications

Because of serious challenges such as air pollution, global warming, and fossil fuels limitations, renewable energy sources such as photovoltaic (PV) systems are increasingly being integrated into the power systems around the world. In this article, a new grid-tied system is proposed for PV applications which consists of an improved flyback DC-DC converter and a new switched-capacitor (SC) based multilevel inverter. Over previously introduced topologies in the same class, the proposed SC-based multilevel inverter has many advantages like reduced number of power switches and DC voltage sources, and also increased number of voltage levels produced at the output. In the proposed structure, one of the most important problems of the capacitive switching inverters, i.e. the occurrence of the impact currents during charging capacitors, is solved by using an inductor with a parallel diode in the capacitive charging current path. This increases the efficiency of the converter and reduces the charging current stress on the capacitors. To validate the performance of the proposed topology, comprehensive experiments and comparisons have been performed and presented. In the experiments, a current controller is used to control the amount of active and reactive power injected to the grid by the proposed grid-tied 17-levels inverter.