隔离式双向全桥DC-DC变换器预充电研究

Pre-Charge Strategy Study for Isolated Dual Active Bridge DC-DC Converter

隔离式双向全桥DC-DC变换器正常运行前,为了防止电流过大冲击和输出侧电容电压振荡过大,需对输出侧稳压电容进行预充电。本文提出了一种不需要外加电路预充电的方法:将输出侧H桥开关闭锁,相当于不控整流桥,调节输入侧H桥开关状态,使得输入侧H桥输出方波占空比D从0逐渐上升到0.5。根据隔离式双向全桥DC-DC变换器的工作特点,证明了预充电过程中输入侧H桥开关为零电流开通。并根据这种预充电方法,提出一种隔离式双向全桥DC-DC变换器自起动的策略。仿真验证了这种预充电方法电适用于单个DC-DC模块和模块级联系统。

Before the normal working of isolated dual active bridge DC-DC converter, the output side capacitor should be pre-charged to prevent over current and voltage oscillation. In this paper a pre-charging method which needs no extra circuits is proposed: the switches of the output side are blocked, and the status of switches in the input bridge side are adjusted, making the duty cycle of the input side square wave voltage changes from 0 to 0.5 step by step. This method is analyzed based on the characteristics of the isolated dual active bridge DC-DC converters, proving that zero current soft switching is achieved during the process of pre-charging. Also a self restart strategy is proposed based on this method. Simulations verify that the output voltage rises gradually to the rated voltage when the proposed DC-DC converter works both individually and in cascaded topologies.