Cascade H-bridge multilevel inverter has high-quality output characteristics and practicability

whereas

the traditional modulation strategy of asymmetric cascade H-bridge multilevel inverter can cause problems of current inversion and energy feedback. To solve these problems

we proposed an unipolarly double-frequency modulation strategy of type-Ⅱ asymmetric hybrid cascaded H-bridge inverter

in which the sub-regional logic operation and combination were conducted at the modulation frequency. As a result

not only the problems of current flow backward and energy feedback can be solved in traditional modulation strategies

but also the maximum switching frequency can be reduced by 50%. Moreover

the harmonic characteristics of output voltage waveform can be improved

and the quality and efficiency of the output power can be ensured. The simulation models and experimental results show that the modulation strategy is feasible and effective.