Improved modulation strategy for type Ⅱ asymmetric three cell CHB inverter
Compared with the symmetrical cascaded H-bridge inverter,the hybrid cascaded H-bridge in-verter has the advantage of using fewer cascaded H-bridge units to output more voltage levels,but the tra-ditional modulation strategy of the hybrid cascaded inverter has the problems of current backflow and en-ergy feedback.In order to solve the problem of current backflow and energy feedback in the traditional modulation strategy of Type Ⅱ asymmetric three-unit hybrid cascade H-bridge inverter,a modulation strategy of switching state function optimization was proposed,and on this basis,the modulation wave was optimized twice,and the pulse was logically calculated and combined.The proposed strategy eliminates the switching state function with current backflow,solves the current backflow and energy feedback prob-lems existing in the traditional modulation strategy of type Ⅱ asymmetric three-unit inverter,reduces the difficulty of modulation realization,and ensures the output power quality.Finally,the feasibility and ef-fectiveness of the proposed modulation strategy were analyzed and verified by setting up the simulation mod-el and experimental platform of Type Ⅱ asymmetric three-unit inverter with a DC voltage ratio of 1∶2∶4.
multilevel inverterhybrid cascademodulation strategycurrent backflowswitch state optimization
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