Power Balance Optimization Modulation Strategy for Hybrid Cascaded H-Bridge Inverter

The traditional modulation strategies based on hybrid cascade H -bridge inverters frequently integrate two modulation approaches: step-wave modulation and carrier cascade modulation. To address the power imbalance issue when the traditional modulation strategy is implemented in the hybrid cascade 11-level inverter with a DC voltage ratio of $1: 2: 2$, an enhanced hybrid modulation strategy is put forward. This strategy is optimized in all operational modes of the units at all levels, and the optimal working mode switching path is established, ensuring that the output voltage polarity of the high and low voltage units remains consistent throughout the output cycle and fulfilling the prerequisite of no current inversion. The dual high-voltage units adopt high-frequency PWM (pulse width modulation)wave modulation, and the output voltage waveforms are complementary and symmetrical, thereby achieving self-balancing of the output power. The simulation and experimental results demonstrate that this strategy can eliminate the current backfilling phenomenon and realize the power balance among high voltage units.