Single carrier PWM-based power balancing for five-level CHB inverter

Although Cascaded H-Bridge Multilevel Inverters using the traditional Level-Shifted Phase Disposition PWM technique provide better Total Harmonic Distortion performance than phase-shifted PWM, they are rarely adopted in CHB systems. This is because they result in uneven power distribution among the H-bridges, leading to uneven thermal stress, component failure, reduced efficiency and reliability. In a five-level CHB inverter using PDPWM, this imbalance primarily occurs because the DC sources are utilised unevenly to generate the intermediate voltage levels of ±VDC. To overcome these challenges, this study proposes a power balancing technique integrated into a single carrier-based Level Shifted PWM technique. The proposed method achieves power balancing by alternately using each source in successive half-cycles to generate the intermediate voltage levels of ±VDC. While ensuring power balance, this modulation technique maintains the quality of output voltage and current waveforms, similar to conventional LSPWM. By embedding the power balancing feature into a single-carrier PWM scheme, the proposed method minimises the number of required PWM modulators and simplifies implementation in digital controllers. Finally, simulation and experimental results are provided to validate its effectiveness.