Abstract For the hybrid cascaded seven-level inverter with a DC-side voltage ratio of 1∶2, it is necessary to ameliorate the conventional modulation method to improve the practicality of the topology. The general hybrid modulation method has a power reverse problem in some modulation ratio interval. Although the unipolar pulse width modulation (PWM) method solves this problem, the high voltage cell working at high frequency in some interval limits the switching frequency of the whole system. The hybrid frequency method reduces the switching frequency of the high voltage cell to a certain extent, but the harmonic characteristics of output voltage will be affected. In view of this, a double frequency modulation method based on the level-shifted PWM (LS-PWM) is proposed in this paper, which not only avoids the power reverse problem but also has a good harmonic characteristic with low switching frequency in high voltage cell. Computer simulations and experiments have verified the proposed method.
Chen Zhong,Xu Yaming,Yuan Tao. A Double Frequency Modulation Method Based on the Level-Shifted Pulse Width Modulation[J]. Transactions of China Electrotechnical Society, 2018, 33(10): 2334-2344.
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2018, Vol. 33 
