三电平直流变换器的交错式PWM方法

三电平结构可将开关管的电压应力箝位于输入电压的一半,因此在高输入电压场合得到了广泛应用。为保证三电平变换器的正常运行,输入分压电容和隔直电容上的电压必须基本平衡,而实际电路中驱动电路延时不一致等问题可能导致电压失衡。本文提出了一种具有更强均压能力的脉冲宽度调制PWM(pulse width modulation)方法 ,该方法通过交错使用两种传统的PWM方法实现。交错式PWM方法将隔直电容电压与输入分压电容电压解耦,同时保证前者一直维持在理想值附近,大大简化了采样电路和均压策略,因此只需要调节驱动信号间的相位差便可以实现电压平衡。实验结果验证了所提调制方法和均压策略的有效性。

Interleaved PWM Method for Three-level DC/DC Converter

Since the voltage stress on power switches is only half of the input voltage through the utilization of a three-level(TL) structure, TL converters have been widely used in high-voltage applications. To ensure the normal oper-ation of TL converters, the voltages on the input-divided capacitors and the blocking capacitor must be balanced basically, whereas the asymmetry of time-delay in the drive circuit may result in voltage unbalance in practice. In this paper, a novel pulse width modulation(PWM) method with better voltage-balancing ability is proposed, which is imple-mented by interleaving two traditional PWM methods. The new PWM method decouples the blocking capacitor voltage from the voltages of input-divided capacitors, and ensures that the former voltage is always kept around its ideal value, which greatly simplifies the sampling circuit and the voltage-balancing strategy. In this way, only the phase shift between driving signals need to be adjusted to achieve voltage balance. Experimental results verified the effectiveness of the proposed modulation method and voltage-balancing strategy.