Novel SHEPWM power balancing control strategy for hybrid cascaded H-bridge inverter
For a hybrid cascaded H-bridge inverter with a DC-side voltage ratio of 1∶1∶2,the traditional SHEPWM method faces an issue of unbalanced output power among different units. To address this issue,a dual-layer power balancing modulation strategy was proposed. In the modulation strategy,power balan-cing was achieved between high-voltage and low-voltage H-bridge units,referring to as outer-layer power balancing,by equivalently splitting the fundamental wave amplitude equation in the harmonic elimination equation set so that the sum of the output voltage fundamental wave amplitudes of the two low-voltage H-bridge units is equal to the output voltage fundamental wave amplitude of the high-voltage H-bridge unit. Secondly,logical operations were utilized to logically reorganize the initial driving signals of the low-volt-age units,achieving power balancing between the two low-voltage units,referring to as inner-layer power balancing. Then,an improved real-coded genetic algorithm (IRCGA-2) was used to solve the harmonic elimination equation set,eliminating specified harmonics and obtaining high-quality output voltage. Fi-nally,simulations and experiments prove correctness and effectiveness of this modulation strategy.
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