This paper proposes a new modulation method for modular multilevel cascade converter-based active power filters (MMC-APFs). The proposed modulation method uses the same pulse width modulation (PWM) controller as a traditional bipolar modulation method, and the generated PWM signals are interchanged among the bridge cells. This method makes it possible to shift the carrier phase angle between two switching legs in one cell, reducing the ripple current through the cell capacitor without increasing the number of PWM channels. This is important to reduce the cost of the control circuit, especially in low-voltage applications of MMCs. An experimental circuit of a 3.3kVA MMC-APF demonstrates a 20% reduction in the ripple current and a 38% reduction in the power loss in the cell capacitor.
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