基于负载电流前馈的级联H桥整流器直流电压平衡策略

DC voltage balance strategy for cascaded H-bridge rectifier based on load current feedforward

针对级联H桥整流器输出电压平衡问题,采用比例脉冲补偿法进行了建模和分析,分析了负载电流扰动对平衡环节的影响,给出了扰动下系统跌落值和调整时间与系统动态指标之间的关系曲线。针对比例脉冲补偿法在负载大范围切换时动态特性差的问题,通过将负载电流引入平衡控制环路,提出了一种基于比例脉冲补偿法的负载电流前馈电压平衡控制策略,其可以在不影响原闭环系统稳定性的基础上,大幅提高平衡控制器的动态特性,并给出了电压平衡比例-积分(PI)控制器参数的设计公式。最后,基于级联H桥整流器的仿真模型和实验样机进行了比较测试,结果显示所提方法在切载情况下各单元之间的最大电压差降低了23 V,调整时间减小了75%。

As for the output voltage balance problem of cascaded H-bridge rectifier,the proportional pulse compensation method is employed for modeling and analyzing. Then,the influence of load current disturbance on the balance link is analyzed,and the relationship curves among voltage drop value,adjustment time and dynamic indexes under disturbances are given. As for the bad dynamic characteristics of proportional pulse compensation method in large-scale load switching,a load current feedforward voltage balance control strategy based on proportional pulse compensation is proposed,which introduces the load current into the balance control link. It can greatly improve the dynamic characteristics of the balance controller without affecting the stability of the original closed-loop system,and the designing formula of parameters for the voltage balance PI controller is given. Finally,the simulation model and experimental prototype based on cascaded H-bridge rectifier are compared and tested,and the results show that the maximum voltage difference between the units is reduced by 23 V and the adjustment time is reduced by 75% under load shedding.