Abstract：As the core component of the modular multilevel converter (MMC) systemsub-module (SM), the capacitoris one of the most fragile components due to its long-term working environment of high-frequency and high-power. Therefore, real-time monitoring of capacitor status is very important to ensure the reliable operation of the MMC system. In this paper, an online monitoring method for SM capacitance in MMC based on Haar wavelet transform reconstruction switch sequence is proposed. Firstly, the input and excision switch sequence of submodule is reconstructed by Haar wavelet transform on the capacitor voltage signal of the MMC system. Secondly, the voltage signal during charging period of the capacitor is selected based on the reconstructed switching sequence, and the capacitance value is monitored online combined with the bridge current signal. Finally, the accuracy and effectiveness of proposed method are verified by the MMC system working condition simulation platform. The proposed method can evaluate the capacitance through the capacitor voltage and arm current signals from the control system, which greatly reduces the difficulty of monitoring by removing the need for switching signals. It provides theoretical and method support for capacitor condition monitoring and active operation and maintenance of the MMC system.
罗丹, 陈民铀, 赖伟, 夏宏鉴, 冉立. 基于Haar小波变换重构开关序列的MMC子模块电容值在线监测方法[J]. 电工技术学报, 2022, 37(20): 5278-5289.
Luo Dan, Chen Minyou, Lai Wei, Xia Hongjian, Ran Li. Online Monitoring Method for Sub-Module Capacitance in Modular Multilevel Converter Based on Haar Wavelet Transform Reconstruction Switch Sequence. Transactions of China Electrotechnical Society, 2022, 37(20): 5278-5289.
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