Harmonic characteristic analytical method of MMC (Modular Multilevel Converter)

An analytical method and technology of harmonic characteristics, applied in the field of harmonic characteristics analysis of MMC, can solve problems such as calculation accuracy influence and error

Active Publication Date: 2013-12-04
ZHEJIANG UNIV
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Problems solved by technology

However, the average switching function of this method only takes the fundamental component under ideal conditions, and the bridge arm current only takes into account the fundamental component, while ignoring the second and above harmonics, which is inconsistent with the actual situation and will lead to to some error
In addition, Song Qiang et al. introduced a method that considers the bridge arm current two The MMC steady-state electrical quantity analysis method of the multiplier component, but the average switching function of this method only takes the fundamental component under ideal conditions, and the calculation accuracy will also be affected

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[0065] In order to describe the present invention more specifically, the technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0066] figure 1 (a) is a schematic diagram of a modular multilevel converter type DC transmission single-phase topology, the bridge arm of the converter adopts figure 1 (b) The half-bridge sub-modules (submodule, SM) shown in (b) are cascaded. Each bridge arm is composed of N sub-modules and a series reactor L.

[0067] In order to simplify the analysis and facilitate understanding, the theoretical derivation of this embodiment is based on the following assumptions

[0068] 1) MMC adopts real-time trigger mode. Real-time triggering can be regarded as a trigger method to control the infinite frequency;

[0069] 2) All submodules are identical;

[0070] 3) Before the MMC is officially put into operation, the pre-charge voltage of the sub-module is V d...

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Abstract

The invention discloses a harmonic characteristic analytical method of an MMC (Modular Multilevel Converter). The harmonic characteristic analytical method comprises utilizing operation conditions and system parameters of the MMC and considering a second harmonic component of the bridge arm current to calculate the bridge arm current of every bridge arm of the MMC; calculating the average capacitive current of sub-modules of the MMC through an average switching function model under the actual condition; calculating the average capacitive voltage of the sub-modules of the MMC according to the relationship between the voltage at two ends of a capacitor and the current which flows through the capacitor; calculating the total voltage of phase bridge arms of the MMC through the average switching function model under the actual condition; utilizing the fourier series harmonic analysis method and extracting second harmonics to perform analysis to calculate the double frequency circular current of the bridge arms. According to the harmonic characteristic analytical method of the MMC, a harmonic component of every electric parameter of the MMC can be calculated, so that the computation commonality is strong, the application range is wide, and the accuracy is greatly improved in comparison with the existing methods.

Description

technical field [0001] The invention belongs to the technical field of power electronic system performance evaluation, and in particular relates to an MMC harmonic characteristic analysis method. Background technique [0002] Modular multilevel converter (MMC) adopts sub-module cascading form to avoid direct series connection of a large number of switching devices, has good voltage output characteristics, and does not have problems such as dynamic voltage equalization, and is very suitable for high-voltage direct current Power transmission occasions. At the two international power electronics conferences in 2010 and 2011, R. Marquardt, a scholar at the Bundeswehr University in Munich, Germany, further proposed the concept of a generalized MMC, which uses sub-modules as the basic unit and divides sub-modules into three types according to their internal structures. Basic types: half bridge sub-module (HBSM), full bridge sub-module (FBSM) and clamp double sub-module (CDSM). ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M1/12
Inventor 徐政肖晃庆薛英林唐庚刘高任宣羿
Owner ZHEJIANG UNIV
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