Modulation signal analysis and parameter selection for modularmulti‑level converters with harmonic injection method

Qifan Zeng; Fei Xiao; Qiang Ren; Sheng Ai

Modulation signal analysis and parameter selection for modularmulti‑level converters with harmonic injection method

Vol. 20, No. 2, pp. 455-465, Mar. 2020

10.1007/s43236-020-00058-y

Modular multilevel converter

Harmonic injection method

Circulating current modulation signal

Overmodulation

Parameter selection

Full-Text

Abstract

The harmonic injection method is widely used in modular multilevel converters (MMCs) to suppress the significant amplitude of the submodule (SM) capacitor voltage fluctuation under low-frequency operation. A method is required to inject high-frequency common-mode voltages and circulating currents, which both occupy modulation space and are prone to over-modulation. This paper focuses on the modulation signal required for circulating current injection, which has been neglected in previous studies. In addition, this paper redefines the amplitude references of the injected harmonics to reserve modulation space for the injected circulating current. By analyzing the characteristics of an MMC system with the harmonic injection method, the relationship between the modulation signal for the circulating current and other variables (such as the output modulation index, output frequency and injection frequency) is obtained. Using the obtained relationship, a strategy for selecting the amplitude and frequency of the injected harmonics is presented to avoid over-modulation under variable conditions while suppress the SM capacitor voltage fluctuation. The theoretical analysis, the proposed injection method and its parameter selection strategy are verified by experimental results.

Statistics

Show / Hide Statistics

Cumulative Counts from September 30th, 2019
Multiple requests among the same browser session are counted as one view. If you mouse over a chart, the values of data points will be shown.

Cite this article

[IEEE Style]

Q. Zeng, F. Xiao, Q. Ren, S. Ai, "Modulation signal analysis and parameter selection for modularmulti‑level converters with harmonic injection method," Journal of Power Electronics, vol. 20, no. 2, pp. 455-465, 2020. DOI: 10.1007/s43236-020-00058-y.

[ACM Style]

Qifan Zeng, Fei Xiao, Qiang Ren, and Sheng Ai. 2020. Modulation signal analysis and parameter selection for modularmulti‑level converters with harmonic injection method. Journal of Power Electronics, 20, 2, (2020), 455-465. DOI: 10.1007/s43236-020-00058-y.