Three-cell Asymmetric Cascade H-bridge Modulation Strategy and Its Generalization
The output voltage harmonic performance of the 3∶1∶1 asymmetric cascaded H-bridge multilevel inverter is excellent,but under the traditional modulation strategy,there is a problem of current backfilling between high and low voltage units,and the traditional modulation strategy is only suitable for 3∶1∶1 asymmetric cascade H-bridge,which cannot be popularized.In some intervals,an improved mixed frequency modulation strategy is proposed based on the control signal complementarity and phase-shift carrier modulation strategies of high and low-voltage units.The modulation strategy proposed in this paper not only solves the problem of current backfilling between high and low voltage units under the traditional modulation strategy,but also can be generalized to n∶1∶1…Modulation strategy for type multilevel inverters.At the same time,a multilevel inverter gives a general expression of the switch control signal of the stage unit and can achieve a power balance between all low-voltage units.Simulation and experimental results show the modulation strategy's feasibility,correctness,and generalizability.
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