Quasi-Online Low-Frequency Impedance Monitoring Scheme for Submodule Capacitors in Modular Multilevel Converters

2019 IEEE Applied Power Electronics Conference and Exposition (APEC) Pub Date : 2019-03-17 DOI:10.1109/APEC.2019.8722277

D. Ronanki, S. Williamson

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引用次数: 8

Abstract

Despite being the most fragile component, aluminum electrolytic capacitors (AECs) are preferred in modular multilevel converters (MMC) due to their high volumetric efficiency and low price. Due to the ageing of AECs, its capacitance decreases and equivalent series resistance (ESR) increases. This can result in an increased voltage ripple, power loss, and could damage the operation of the MMC. Therefore, condition monitoring of submodule (SM) capacitors in an MMC is indispensable to enhance system reliability. This paper presents a new condition monitoring technique for SM capacitors based on the measurement of its low-frequency impedance. The low-frequency impedance is evaluated based on the information of the second harmonic component in the SM capacitor voltage and current. In this scheme, a low-frequency voltage signal is injected in the control loop of the MMC with available hardware and controller for converter control. The proposed scheme has been validated through PLECS simulations on a three-phase half-bridge submodule (HB-SM) based MMC. This technique is also verified experimentally on a single-phase MMC with a four HB-SMs per arm.

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模块化多电平变换器中子模块电容的准在线低频阻抗监测方案

尽管铝电解电容器(aec)是最脆弱的元件，但由于其高体积效率和低价格，在模块化多电平转换器(MMC)中是首选。由于aec老化，其电容减小，等效串联电阻(ESR)增大。这可能导致电压纹波增加，功率损失，并可能损坏MMC的操作。因此，对MMC中的子模块电容器进行状态监测是提高系统可靠性的必要手段。本文提出了一种基于SM电容器低频阻抗测量的状态监测新技术。根据电容电压和电流中二次谐波分量的信息来评估低频阻抗。在该方案中，利用可用的硬件和控制器将低频电压信号注入到MMC的控制回路中，用于转换器的控制。该方案已通过基于三相半桥子模块(HB-SM)的MMC的PLECS仿真验证。该技术还在每个臂有四个HB-SMs的单相MMC上进行了实验验证。

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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2019 IEEE Applied Power Electronics Conference and Exposition (APEC)

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