改进型零电压开关PWM三电平直流变换器

该文介绍了改进型零电压开关脉宽调制三电平直流变换器(ZVSPWMTL变换器)，该变换器是将传统的ZVSPWMTL变换器的变压器和谐振电感位置互换，使得变压器与滞后管相连。改进后的变换器箝位二极管在一个周期中只导通一次，同时零状态谐振电感电流较小，有利于提高变换器的效率，占空比丢失也减小。该文详细分析了该变换器的工作原理。为了防止变压器直流磁化，一般在变换器中加入隔直电容，该文分析了隔直电容与变压器或谐振电感串联时对电路工作的影响，确定一种最佳方案，并通过实验验证理论分析的正确性。

AN IMPROVED ZVS PWM THREE-LEVEL CONVERTER

An improved zero-voltage-switching pulse- wide-modulation three-level converter (ZVS PWM TL converter) is proposed, which is improved from original ZVS PWM TL converter just by exchanging the position of the resonant inductance and the transformer which is connected with the lagging switches. The improved converter has several advantages over the original one, e.g., the clamping diodes conduct only once in a switching period, and the resonant inductance current is smaller when in zero state, that leads to a higher efficiency and lower duty cycle loss. A blocking capacitor is usually introduced to the primary side to prevent the transformer from saturating, its effects are analysed in different positions and an scheme is determined. A 2.5kW prototype converter verifies the effectiveness of the improved converter and the optimal scheme for the blocking capacitor.