论文标题
基于阻抗的AC/DC终端建模和MMC-BTB系统的分析
Impedance-based AC/DC Terminal Modeling and Analysis of MMC-BTB system
论文作者
论文摘要
基于阻抗的小信号稳定性分析被广泛应用于模块化多级转换器（MMC）的实用工程中。但是，现有阻抗模型（IMS）的缺陷和单个MMC的理想扩展影响了多微型系统中的分析。本文中关注基于MMC的背对背系统，可以填补此类差距。为了获得系统的稳态轨迹，首先根据频域中的牛顿 - 拉夫森迭代提出了一种数值方法。然后，通过将共享终端动力学替换为主动或被动设备，理论AC/DC IMS考虑使用纯时间延迟的典型控制回路，可以基于多辅助线性化直接建立。进一步在当前文献中的衍生IMS（即功率变压器对低频阻抗特征的影响）和使用简化IMS进行高频共振研究的合理性的进一步帮助。可以证实，应在AC和DC终端全面分析相互联系系统的稳定性。这有助于定位不稳定性来源，获得稳定余量并指导补充控制策略。所有IM和分析均通过PSCAD中的频率扫描和模拟来验证。
Impedance-based small-signal stability analysis is widely applied in practical engineering with modular multilevel converters (MMCs). However, the deficiencies of existing impedance models (IMs) and the idealized extension for the single MMC influence the analyses in multiterminal systems. Such gaps are filled by focusing on an MMC-based back-to-back system in this paper. To obtain the steady-state trajectory of the system, a numerical method is first proposed based on Newton-Raphson iteration in the frequency domain. Then, by substituting the shared terminal dynamics with active or passive devices, theoretical AC/DC IMs that consider typical control loops with the pure time delay, are directly established based on the multiharmonic linearization. Further aided by the derived IMs, two neglected aspects in the current literature, i.e., the influence of power transformers on low-frequency impedance characteristics and the rationality of using simplified IMs for high-frequency resonance studies, are investigated. It is confirmed that the stability of interlinking systems should be comprehensively analyzed at both AC and DC terminals. This helps position the instability source, obtain the stability margin, and guide the supplementary control strategy. All IMs and analyses are verified by frequency scans and simulations in PSCAD.
