Robust Hybrid Modulation Strategy Incorporating Unipolar Phase-Shifted Control for Multi-Cell Asymmetric Cascaded H-Bridge Converters

Asymmetric cascaded H-bridge (ACHB) converters with unequal DC-link voltages offer a promising solution to mitigate the substantial increase in power devices, energy storage components, and overall inverter volume that typically accompanies conventional cascaded H-bridge converters with a large number of output levels. However, existing modulation techniques often result in output power imbalance and current backflow among cascaded cells, and are typically limited to specific numbers of cascaded cells. To address these challenges, this paper first proposes a generalized ACHB converter topology scalable to an arbitrary number of cascaded cells, consisting of a main power cell and multiple switching cells. A robust hybrid modulation strategy is then developed, integrating dynamically adjusted staircase modulation for the main power cell and unipolar carrier phase-shifted modulation for the switching cells, enabling coordinated output power control across all cells. Simulation and experimental results validate the effectiveness of the proposed method in achieving balanced output power allocation and avoiding current backflow in multi-cell ACHB converters.