This paper suggests a methodology for the identification, classification, and evaluation of various types of interactions that may occur in an HVDC link based on modular multi-level converters (MMC). The methodology incorporates the most suitable analytic tools for the frequency-domain study of each interaction category. To do so, a detailed nonlinear model of an MMC-based HVDC link that consists of master and slave MMCs, AC grids, and the DC transmission system is derived. Then, it is linearized to obtain a multi-input multi-output (MIMO) linear model that represents the dynamics of the complete MMC-based HVDC link. Based on the control loops of interest, interactions are classified as (1) state variable interactions, (2) disturbance interactions, (3) control loop interactions, and (4) overall system interactions. Then, through the application examples, the mentioned four categories of interactions are studied in frequency domain via the relevant analytic tools. The results obtained from the frequency-domain analysis are validated by time-domain simulation.

本文提出了一种基于模块化多电平转换器 (MMC) 的 HVDC 链路中可能发生的各种类型交互的识别、分类和评估方法。该方法结合了最适合每个交互类别的频域研究的分析工具。为此，导出了基于 MMC 的 HVDC 链路的详细非线性模型，该链路由主和从 MMC、交流电网和直流输电系统组成。然后，对其进行线性化以获得一个多输入多输出 (MIMO) 线性模型，该模型代表了完整的基于 MMC 的 HVDC 链路的动态。基于感兴趣的控制回路，相互作用分为（1）状态变量相互作用，（2）干扰相互作用，（3）控制回路相互作用，和（4）整体系统相互作用。然后，通过应用实例，通过相关的分析工具在频域研究了上述四类相互作用。从频域分析获得的结果通过时域仿真得到验证。