Hybrid cascaded H-bridge inverters with multiple low-voltage cells have more redundant switching states during level switching. The carrier amplitude shift method can well solve the current backflow problem for low-voltage cells modulation. However

due to its own characteristics

the multi-carrier amplitude shift method has the disadvantages of unbalanced output power of cascaded cells and low equivalent switching frequency of inverter output voltage. For this reason

for the hybrid cascaded nine-level inverter with a DC side voltage ratio of 1:1:2

a hybrid modulation strategy combining PWM modulation and ladder wave modulation was proposed to enable the high-voltage cells to work in the fundamental frequency state

and to enable the low-voltage cells to work at high frequency through a hybrid modulation method similar to unipolar frequency multiplication

which improved the equivalent switching frequency of the inverter output voltage. At the same time

the low-voltage cells adopted a 1/4 cycle cyclic modulation method to realize the low-voltage cells within half a cycle. The output power was balanced between the two

and the feasibility and correctness of the theoretical analysis were verified through simulation and experimental results analysis.