模块化多电平变换器环流及电容电压的稳态解析表达式

Steady State Analytic Expressions of Circulating Currents and Capacitor Voltages of the Modular Multilevel Converter

环流谐波及电容电压波动是模块化多电平变换器(MMC)的一个重要研究课题。本文通过一个MMC的等效模型推导出了由输出电流引起的环流谐波及电容电压波动的解析表达式,指出环流谐波本质上是存在于系统直流侧的谐波电压引起的激励,分析了环流谐波相生的原理。根据表达式,分析了系统参数对环流谐波的影响,得出结论,即环流谐波幅值随系统频率等参数的变化呈谐振特性。最后通过仿真研究证实了所提表达式的正确性。

The study of the circulating harmonic currents and the capacitor voltage fluctuation of the modular multilevel converter （MMC） is a hot topic, so the analytic expressions of the circulating harmonic currents and capacitor voltages in steady state based on an existing equivalent model of the MMC is deduced. During this course, it concluded that the circulating harmonic currents are essentially products of the exciting course of a harmonic voltage upon the dc loop, and the principle of the circulating harmonics produced each other. According the deduced expressions, effects of the system parameters upon the circulating harmonics are analyzed. Finally the simulation study proved the deduced expressions.