二级式三电平逆变器不连续调制及中点电位平衡策略

Discontinuous modulation and neutral-point potential balance strategy for two-stage three-level inverter

针对常见的前置TL-Boost变换器的二级式三电平逆变器,为降低逆变器开关损耗,同时控制中点电位平衡,文中提出了一种空间矢量不连续调制及其中点电位平衡策略。首先设计了不连续调制算法,分析不连续调制下逆变器中点电位波动情况;然后基于电荷平衡原理,定量计算TL-Boost变换器电荷补偿量,推导变换器占空比调整量表达式,控制流经中点的总电荷量为零。通过两级系统协调控制,不仅可发挥逆变器不连续调制低开关损耗的优势,同时可实现中点电位平衡控制,降低逆变器调制策略复杂度。该控制策略适用于二级式三电平逆变器,可有效提高系统效率,同时保证输出波形质量。

In order to reduce the switching loss of the inverter and control the neutral-point potential balance,a novel discontinuous space vector modulation are proposed for the typical two-stage TL-Boost converter and three-level inverter.Firstly,the discontinuous modulation algorithm is designed,and the fluctuation of the neutral-point potential of the inverter is analyzed.The charge compensation of the TL-Boost converter is quantitatively calculated based on charge balance principle.Then,the adjustment of duty ratio is deduced,aiming at controlling the total amount of charge flowing through the neutral-point to zero.Through the two-stage coordinated control strategy,it can not only take advantage of the low-switching loss of the discontinuous modulation,but also suppress the neutral-point potential fluctuations.The strategy is applicable to the two-stage three-level inverter,which can obvious y improve the system efficiency while guaranteed the quality of output waveform.