半桥三电平直流变换器的中点平衡控制方法

摘要

Half-bridge three-level DC/DC converter with clamping diodes mainly apply to high-voltage input occasion for the reason that the voltage stress across the primary switches is only half of the input DC bus voltage.Besides,it realizes the zero voltage switching(ZVS) turning on of the primary switches and suppresses the peak voltage of the rectifier bridge,improving the efficiency of converters.However,the difference of the driving circuit and switches will bring the safety hazard when the voltage stress that across the primary switches and rectifier diodes is different.A novel neutral-point balancing digital control method is presented to realize the voltage-sharing control of input dividing capacitors which regulates the duty by amending the modulating wave in the single-carrier,doublet trigger mode.Finally,an 18 kW prototype is built and the validity of the neutral-point balancing control method is verified.%带箝位二极管的半桥三电平直流变换器主要用于高压输入场合,其初级功率管电压应力仅为直流母线电压的一半,不仅可以实现初级开关管的零电压开关(ZXS)开通,且能抑制次级整流桥的尖峰电压,有效提高了变换器效率.但实际平台中存在的驱动电路和开关管差异性也会带来输入侧上下分压电容不均压的中点平衡问题,从而导致初级功率管以及次级整流桥二极管电压应力不同,存在安全隐患.针对该问题,提出了一种中点平衡的数字控制方法,在单载波、双沿触发模式下通过修正调制波来调节正负半周期的占空比,实现输入分压电容的均压控制.最后试制了一台18 kW的实验样机,实验结果验证了该中点平衡控制方法的有效性.