A Modular Multilevel Converter with Boosting, Self-Balancing, and Scaling Capabilities for High- Voltage Transformerless PV Applications

Abstract

This paper proposes a single source modular multilevel inverter with self-balancing and boosting capabilities. The proposed topology uses several half-bridge cells, load-side switches, and one charging unit. In high-voltage PV applications the load-side switches consisting of several series-connected switches should be employed in the proposed topology. This is termed as the switch string. In the proposed topology, the charging unit charges the capacitors inserted into the modules. The charging process of the capacitors is done using a charging inductor. This inductor can both mitigate the capacitor inrush currents and limit the fault current. Furthermore, the proposed topology draws a continuous current from the dc side. Simulation results, carried out in Matlab/Simulink, are provided to demonstrate the versatility and feasibility of the proposed topology.