Module Power Balance Modulation Method for Cascaded Multilevel Inverters With Full Modulation Ratio Range

The cascaded H-bridge (CHB) inverters has drawn much attention in renewable energy and industrial applications. Conventional modulation strategies for CHB inverters face challenges in simultaneously achieving optimal output voltage harmonic characteristics and active power balancing among cascaded units. To address this issue, this paper proposes a novel power-balancing modulation strategy based on carrier cycle adjustment for nine-level CHB inverters with full modulation ratio range. The proposed method extends conventional Phase Disposition (PD) modulation by synchronously rearranging the carriers above and below the time axis, thereby creating a new carrier period cycle that can improve the output of internal power units. Within this framework, duty cycle expressions for each cascaded unit are derived, and the corresponding fundamental voltage components are analytically obtained. The analysis demonstrates that the proposed strategy achieves effective power balancing across all cascaded units within a single fundamental cycle. Finally, both simulation and experimental results confirm the effectiveness and practicality of the method.