Single-DC-source 7-level CHB inverter with multicarrier level-shifted PWM

摘要

This paper presents a 7-level cascaded H-bridge (CHB) multilevel inverter using a single DC source. The second DC bus is a capacitor that its voltage is controlled by switching sequences. The capacitor voltage is regulated at half of the DC source amplitude to have seven voltage levels at the output. Seven voltage levels include each DC bus voltage, their sum and subtraction. Switching pattern is designed based on the redundant switching states and multicarrier level-shifted pulse width modulation (PWM) technique to help controlling the capacitor voltage at the desired level. Simulation results are presented to validate the effective voltage balancing procedure integrated into switching technique and consequently generating the 7-level voltage waveform at the output with low harmonic contents.