与换流器控制方式解耦损耗分析方法研究

Research on Decoupling the MMC Losses Analysis and the Modulation Mode for Modular Multilevel Converters

模块化多电平换流器(MMC)避免了器件直接串联,大幅降低了器件开关频率,成为柔性直流输电和基于全控器件的新型高压FACTS装置采用的最主要拓扑。MMC换流器因其制控制方式多采用最近电平逼近方式,其开关规律难以准确表达,导致其损耗分析困难。在此提出一种损耗分析方法,该方法综合考虑影响损耗各因素,绘制了损耗随各因素变化总表,与仿真计算相结合,通过查表来计算MMC损耗,既实现了MMC损耗分析与控制方式解耦,又满足了仿真对算法快速性要求。结合算例,对该方法对MMC损耗特性进行了计算,并给出相应的分析。

Since no direct series connections are present in the modular multilevel converter（MMC）,which significantly reduces the switching frequency of components,the MMC has become the most important topology applied to light-HVDC and full-controller-based FACTS.Since the nearest level modulation is used by most MMCs and it is of great difficulty to express the switching rule in an exact way,it is difficult to analyze the power losses.Here a method is proposed for power losses analysis.In this method,the loss-factor curves are plotted based on all the factors affecting the losses,and then it is combined with simulation calculations,and the MMC losses can be figured out via table look-up.This method can decouple the MMC losses analysis and the modulation mode and it can also meet the simulation demand for rapid algorithm.Based on an example,the losses characteristics of MMCs are worked out by means of the method,and the associated analysis is carried out.