基于多频段动态相量法的MMC换流器建模方法

Research of Modeling Method of Modular Multilevel Converter Based on Multi-frequency Bands Dynamic Phasor

大规模交直流电网中,为了提高仿真速度,换流器通常采用外特性建模。动态相量法和频率偏移法是两种常用的外特性建模方法。传统的动态相量法能够增大仿真步长,但由于存在较大的谐波截断误差导致精度较差。频率偏移法仅用于以工频为主导频率的窄带信号,当信号含有较高频率成份时,无法适用。该文应用提出的多频段动态相量法,进行模块化多电平换流器(modular multilevel converter,MMC)的外特性建模,实现仿真精度和速度的兼顾。该文首先建立MMC的开关函数模型,给出开关函数的高阶解析式,以此为基础,建立MMC换流器多频段动态相量频段耦合模型。然后,面向CPU的多核芯特点,分析MMC的运行特性,建立MMC多频段动态相量频段解耦模型,实现频段间的并行大步长仿真。最后通过仿真算例,与MMC详细模型进行对比,验证模型的有效性。

The output characteristic model of convertor is usually explored for speed the electromagnetic transient simulation(EMT) of large-scale hybrid AC/DC power grid. The dynamic phasor(DP) and shifted frequency analysis are two popular methods for the output modeling. But the accuracy of traditional DP is very poor due to the big harmonic truncation error and SFA is usually used for the narrow band signal which is near the fundamental frequency. This paper proposed an output characteristic modeling improved method of modular multilevel converter(MMC) based on the multi-frequency band dynamic phasor(MFBDP) which is both high simulation speed and accuracy. Firstly, the coupled multi-frequency band dynamic phasor model(CMFBDP) of MMC was founded based on the high-order analytical expression of MMC switching function and MFBDP. Then the model was decoupled based on the operation characteristics of MMC, and the decoupled multi-frequency band dynamic phasor model(DMFBDP) of MMC was obtained, which can be used on CPU multi-core parallel with large time step. Finally, a study case was given to verify the validity of the model by comparing it with the detailed MMC model.