模块化多电平矩阵变换器电容电压纹波稳态分析

Steady-state Analysis of Sub-modular Capacitor Voltage Ripple in Modular Multilevel Matrix Converters

模块化多电平矩阵变换器(modular multilevel matrixconverters,M3C)是一种新型的基于级联H桥的直接交-交变换器拓扑结构,可用中/高压功率频率变换场合,但其应用范围受H桥子模块直流侧电容纹波电压的限制。从能量守恒角度研究M3C子模块电容电压的一般性波动规律,导出稳态条件下电容纹波电压与M3C输入/出频率、功率因数、电压比值等参量之间的定量关系。对各参量对纹波电压的影响程度进行理论分析并得出下列结论:电容纹波电压中一般含有输入/输出频率的二倍频、差频及和频4种频率成分,在几种特例中仅包含3种频率成分;电容纹波电压幅值对输入/输出频率比值变化非常敏感,当输入和输出频率彼此接近或一个趋近于零时,纹波电压幅值会逐渐变得很大,导致M3C无法正常工作。仿真计算验证了理论分析的正确性。

The modular multilevel matrix converter （M3C） is a novel direct AC converter topology based on the cascaded H-bridge, and is available in medium/high voltage power frequency conversion occasions. However, its application fields are limited by the DC capacitor ripple voltage of the H-bridge sub-module. In this paper, a general variation rule of the capacitor voltage ripple was studied from the energy conservation point of view, and the quantitative relationships among the ripple voltage and the M3C input/output frequency, power factor, voltage ratio were derived on the steady-state conditions. The impacts of the different parameters on the ripple voltage were analyzed in details. The following conclusions were drawn： the ripple voltage in general contains the doubling, difference and sum frequency components of the Mac input and output, while only three kinds of frequency components were included in several special cases; the ripple voltage amplitude was very sensitive to the input/output frequency ratio, and when the input and output frequencies approach each other or one of them tends to zero, the ripple voltage amplitude will gradually become very large, causing the Mac to work improperly. The simulation and calculation results validate the correctness of the theoretical analysis.