Seven-Level Packed U-Cell (PUC) Converter with Natural Balancing of Capacitor Voltages

Abstract

A Packed U-Cell (PUC) converter is presented in this paper. The converter uses a single DC source and two capacitors. The capacitors converge to the desired voltages without any closed loop control. The isolated DC source and the capacitor voltages together are maintained at a ratio of 3:2:1. Therefore, the PUC converter can generate a seven-level output voltage at unity modulation index. When compared to cascaded H-bridge converters, the PUC converters offer limited number of switching states for a given number of DC sources. These limited number of states have been utilized to deal with the capacitor voltages in open loop and is the main advantage of the proposed PUC converter. So, capacitors of the proposed PUC converter, have the ability to settle down to their steady state voltages from any arbitrary initial conditions. The proposed inverter can work for any practical load power factor. Operation of the topology is validated through simulations in MATLAB/ Simulink.