非隔离混合型三电平柔性潮流转供装置的漏电流抑制和直流电压平衡控制策略

doi:10.19595/j.cnki.1000-6753.tces.250319

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摘要针对非隔离型柔性潮流转供装置存在的漏电流抑制难度大、直流电压扰动多、多目标控制耦合性强等问题,该文提出一种三相三线和三相四线制混合的三电平柔性潮流转供装置,并针对该装置研发了共模漏电流直接闭环调节抑制方法和直流电压平衡控制策略。首先,建立非隔离混合型三电平柔性潮流转供装置的共模等效电路模型,得出共模漏电流的主要分量为3、9次谐波,进而提出共模漏电流特征次谐波分量直接闭环抑制策略。其次,为了应对潮流转供、共模漏电流抑制等过程中双侧变流器中二极管钳位电流引起的直流电压不均衡问题,提出二极管钳位电流的低频特征分量在线估算方法,并基于整流侧中线电流主动谐波注入实现了直流电压的高度均衡。最后,通过实验验证了所提方法的有效性。

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关键词 ：柔性潮流转供装置, 三电平变流器, 漏电流, 钳位电流估算, 直流电压平衡

Abstract：Non-isolated flexible current transfer devices face three challenges in engineering applications. (1) Leakage current suppression difficulty. Due to the lack of a physical isolation layer, the high-frequency switching action generated by the common-mode voltage and the system-to-ground parasitic capacitance can form a resonant loop, triggering leakage currents at the ampere level. (2) The DC voltage multi-source perturbation is significant. The coupling of power mutation, impedance network resonance, and other multi- physical fields exacerbates the risk of DC bus voltage instability. (3) Strong coupling of multi-objective control, such as the power dynamic response, leakage current amplitude, midpoint potential equilibrium, redundant vector selection, and the voltage loop bandwidth.
This paper proposes a three-phase, three-wire and a three-phase, four-wire hybrid three-level flexible current transfer device. A direct closed-loop regulation suppression method of common-mode leakage current and a DC voltage balance control strategy are developed. Firstly, the common-mode equivalent circuit model of the non-isolated hybrid three-level flexible trend-switching device is established. The main components of the common-mode leakage current are the third and ninth harmonics. A direct closed-loop suppression strategy is proposed for the characteristic subharmonic components of the common mode leakage current. Secondly, an online estimation method is proposed for the low-frequency eigencomponent of the diode clamping current. A high degree of DC voltage equalization is achieved through the active harmonic injection of the midline current on the rectifier side.
The experimental results show that the proposed method efficiently suppresses common-mode leakage current. The inverter-side grid current is close to sinusoidal, with a total harmonic distortion (THD) of 2.64%. As the rectifier-side converter needs to balance the DC bus voltage through midline current control, the rectifier-side current distortion rate increases (THD=4.64%). The peak common-mode leakage current is reduced to 0.25 A, approximately 83% lower than that of the conventional control system. In addition, through DC voltage balance control, diode clamping current, and common-mode leakage current feed-forward compensation, the DC voltage deviation is 2.53 V, a 50% decrease compared to the traditional control system.
The following conclusions can be drawn. (1) The isolation transformer with high cost and large size is completely removed, which provides a new idea for the compact, flexible current transfer device. (2) The control objective of DC voltage balance and common mode leakage current suppression is realized, avoiding the strong coupling problem caused by vector selection. (3) The capacitor voltage fluctuation suppression provides an accurate estimation of the clamping current of the three-level converter.

Key words： Flexible current transfer device three-level converter leakage current clamp current estimation DC voltage balance

收稿日期: 2025-02-27

PACS:

TM46

基金资助:国家电网总部科技资助项目（521001250022-064-ZN）

通讯作者: 何晋伟男,1983年生,教授,博士生导师,研究方向为微电网和分布式发电、新能源并网装备与控制、电能质量等。E-mail: jinwei.he@tju.edu.cn

作者简介: 包明骏男,2000年生,硕士研究生,研究方向为微电网和分布式发电、新能源并网。E-mail: 2022234410@tju.edu.cn

引用本文:

包明骏, 何晋伟, 张宸宇, 袁宇波, 王成山. 非隔离混合型三电平柔性潮流转供装置的漏电流抑制和直流电压平衡控制策略[J]. 电工技术学报, 2026, 41(4): 1298-1310. Bao Mingjun, He Jinwei, Zhang Chenyu, Yuan Yubo, Wang Chengshan. Leakage Current Suppression and DC Voltage Balance Control for Non-Isolated Hybrid Three-Level Flexible Power Flow Converter. Transactions of China Electrotechnical Society, 2026, 41(4): 1298-1310.

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