A Step-Up 5-Level Transformer-Less Switched Capacitor Inverter Without Leakage Current for PV System Application

This article proposes a 1-phi transformer-less inverter for grid-tied PV systems. The proposed inverter has the capability to produce five distinct voltage levels at the output stage. Moreover, it is a compact switched-capacitor (SC) based design that incorporates eight power switches, an ultra-fast power diode, and two electrolytic SCs. This topology reduces the number of power electronic components, resulting in decreased cost and weight. Due to the direct connection of the negative dc line of the proposed inverter to the null of the grid voltage, the leakage current is completely removed for PV application. Another advantage of this topology is that it can easily boost the output voltage by a factor of two without the need for any magnetic or active devices. During the grid voltage period, the SC's are charged in series with the input voltage, resulting in automatic balancing. As a result, the proposed inverter eliminates the need for a complex control method to balance the SC's. Design guidelines have been developed for the proposed inverter. Also, the quantitative comparative study with similar five-level topologies is presented to show superiority of the proposed inverter. Moreover, the proposed inverter alongside a PV system is simulated to demonstrate the capability of the proposed inverter in a closed-loop D-Q control system. This topology is validated using a laboratory prototype for a 1 kW system at a grid-tied connection.