Symmetrical operation of modular multilevel converter during sub-module faults

IF 3.3 3区工程技术 Q2 ENGINEERING, ELECTRICAL & ELECTRONIC Electric Power Systems Research Pub Date : 2024-10-16 DOI:10.1016/j.epsr.2024.111157

Shilpi Kedia, Rohit S. Thute, Himanshu J. Bahirat

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Abstract

The strategies for handling sub-module (SM) faults in modular multilevel converters (MMCs) are essential for improving the reliability of HVDC grids. The SM faults are generally mitigated through the by-passing of faulty SMs. However, this results in an unbalance in three-phase voltages and currents, which is not desirable for the efficient operation of the MMC. Therefore, fault-tolerant strategies are required to compensate for the impact of the loss of SM. In this work, the unbalance introduced due to the by-passing of SMs has been studied by detailed simulation using the switched model of MMC. Further, a strategy to detect a by-passed SM based on arm-current analysis is presented. This paper also proposes an algorithm for restoring voltage balance during SM faults. In this algorithm, the number of healthy SMs in each arm is maintained equal, and the corresponding insertion indices are determined for symmetrical operation. The proposed algorithm is validated by simulating a simple circuit example of an MMC with fifty SM per arm using MATLAB/Simulink.

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子模块故障期间模块化多电平转换器的对称运行

模块化多电平转换器（MMC）中处理子模块（SM）故障的策略对于提高高压直流电网的可靠性至关重要。一般情况下，通过旁路故障 SM 来缓解 SM 故障。然而，这会导致三相电压和电流不平衡，不利于 MMC 的有效运行。因此，需要采用容错策略来补偿 SM 丢失造成的影响。在这项工作中，通过使用 MMC 的开关模型进行详细模拟，研究了 SM 旁路引起的不平衡。此外，还提出了一种基于臂电流分析的 SM 旁路检测策略。本文还提出了一种在 SM 故障期间恢复电压平衡的算法。在该算法中，每个臂中健康 SM 的数量保持相等，并为对称运行确定相应的插入指数。通过使用 MATLAB/Simulink 模拟一个每臂有 50 个 SM 的 MMC 的简单电路示例，验证了所提出的算法。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Electric Power Systems Research 工程技术-工程：电子与电气

CiteScore

7.50

自引率

17.90%

发文量

963

审稿时长

3.8 months

期刊介绍： Electric Power Systems Research is an international medium for the publication of original papers concerned with the generation, transmission, distribution and utilization of electrical energy. The journal aims at presenting important results of work in this field, whether in the form of applied research, development of new procedures or components, orginal application of existing knowledge or new designapproaches. The scope of Electric Power Systems Research is broad, encompassing all aspects of electric power systems. The following list of topics is not intended to be exhaustive, but rather to indicate topics that fall within the journal purview. • Generation techniques ranging from advances in conventional electromechanical methods, through nuclear power generation, to renewable energy generation. • Transmission, spanning the broad area from UHV (ac and dc) to network operation and protection, line routing and design. • Substation work: equipment design, protection and control systems. • Distribution techniques, equipment development, and smart grids. • The utilization area from energy efficiency to distributed load levelling techniques. • Systems studies including control techniques, planning, optimization methods, stability, security assessment and insulation coordination.