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An Analytical Method for Harmonic Transmission Characteristics of AC and DC Sides of Modular Multilevel Converter

A modular multi-level, transmission characteristic technology, applied in the direction of power transmission AC network, instruments, electrical components, etc., can solve the quantitative analysis that cannot be used for harmonic transmission, the analysis of harmonic transmission characteristics that is not applicable to MMC, and the error of analysis results, etc. question

Active Publication Date: 2020-10-09
STATE GRID ECONOMIC TECH RES INST CO +2
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Problems solved by technology

However, weak AC and new energy systems are susceptible to harmonic disturbances and nonlinear equipment. In some extreme cases, harmonics of certain frequencies on the AC side will cause resonance in the DC network, resulting in system instability, and through the DC network to other interconnected communication systems
[0003] On the one hand, due to the complex coupling relationship between the MMC bridge arm current, the sub-module capacitor voltage and current, and the modulation wave, the previous analytical method for two-level VSC is not suitable for the analysis of MMC harmonic transmission characteristics
On the other hand, the voltage of the MMC bridge arm will play an important role in the harmonic transmission process. The previous steady-state operation analysis methods have ignored the internal harmonic components of the MMC sub-module or only considered the second harmonic component, simplifying the system analysis process and at the same time , causing large errors in the analysis results, and cannot be used for quantitative analysis of harmonic transmission

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  • An Analytical Method for Harmonic Transmission Characteristics of AC and DC Sides of Modular Multilevel Converter
  • An Analytical Method for Harmonic Transmission Characteristics of AC and DC Sides of Modular Multilevel Converter
  • An Analytical Method for Harmonic Transmission Characteristics of AC and DC Sides of Modular Multilevel Converter

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Embodiment Construction

[0031] The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0032] The present invention provides a method for analyzing the harmonic transmission characteristics of the AC and DC side of a modular multilevel converter, comprising the following steps:

[0033] Step 1: Collect the actual value v of the three-phase AC voltage at the grid-connected point of the fixed power station in the flexible DC grid abc , The actual value of the three-phase AC current i abc and the actual value of the DC side voltage u dc , and carry out per unitization;

[0034] figure 1 Shows the topological diagram of the MMC main circuit; the actual value of the three-phase AC voltage v of the converter station in the figure abc , The actual value of t...

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Abstract

The invention discloses a method for analyzing the harmonic transmission characteristics of the AC and DC side of a modular multilevel converter. The method firstly analyzes the influence of background harmonics on both the MMC control system and the electrical system, and proposes a background harmonic The calculation method of the influence of electrical quantity and control quantity on MMC. Based on this, the coupling relationship between the control system and the electrical system of MMC-HVDC is analyzed, and the equivalent circuit of the MMC electrical system considering the influence of the internal voltage fluctuation of the sub-module and the circulating current of the bridge arm is established. Using this equivalent circuit, the background harmonic Analytical expression for the effect of the wave on the other side of the MMC.

Description

technical field [0001] The invention belongs to the field of safe operation of flexible direct current transmission, and in particular relates to an analysis method for the harmonic transmission characteristics of the AC and DC sides of a modular multilevel converter, which is used to analyze the background harmonics of the AC and DC sides through the modularized multilevel In the propagation process of the converter (Modular Multilevel Converter, MMC), avoiding the harmonics of certain frequencies on the AC side will cause the resonance of the DC network, resulting in system instability. Wave suppression and stability analysis are of great significance. Background technique [0002] In recent years, with the gradual establishment of large-capacity flexible DC power grid projects, its potential stability problems have become increasingly prominent. With the development of new energy, more and more weak systems and new energy electric fields are interconnected through MMC. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/00H02J3/36G06F30/20G06F113/04
CPCH02J3/00H02J3/36H02J2003/365G06F30/20H02J2203/20Y02E60/60
Inventor 乐波梅念王跃徐鹏帆尹太元王璋
Owner STATE GRID ECONOMIC TECH RES INST CO
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