级联不对称五电平逆变器电容值分析

Analysis of Capacitor Values in Cascade Asymmetric Five- Level Converters

相对于其他大多数对称拓扑结构的逆变器而言,级联不对称五电平逆变器在生成五电平的同时,开关状态减少至对称拓扑结构逆变器的二分之一,并且降低了钳位电容和二极管的使用数量,此外,母线电容中点电压也可以实现自平衡。文中基于级联不对称五电平逆变器的拓扑结构,分析了在载波移相PWM调制策略下直流母线电容和悬浮电容的取值问题,并对该拓扑结构进行仿真分析。仿真结果表明,该拓扑结构开关函数简单易于控制,母线电容电压基本保持稳定且能够实现自平衡。选取适当的母线电容值以及悬浮电容值能够非常有效地减小输出的谐波分量,并提高电容的利用率。

Compared with other converters with symmetric topology,the cascade asymmetric five - level converter can reduce switching states by one - half and decrease the number of capacitors or diodes for use. Moreover,it realizes the self - balance of bus capacitor voltage. Based on a five - level cascaded asymmetric converter topology,the PSPWM strategy is used to calculate values of DC bus capacitors and flying capacitors. Simulation result shows that the switc-hing functions are simple and easy to control,while the bus capacitor voltage is basically stable and able to achieve self - balancing. When appropriate capacitance values are selected,it can be very effective to reduce harmonic com-ponent of the output and improve the utilization of the capacitors.