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Method for balancing capacitor voltage of modularization multilevel converter

A modular multi-level, capacitive voltage technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problems of high sorting frequency, inconsistency, and high switching frequency of switching devices. Achieve cost savings, consistent switching stress, and low real-time requirements

Active Publication Date: 2014-11-19
ZHEJIANG UNIV
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Problems solved by technology

[0007] Aiming at the above-mentioned technical problems existing in the prior art, the present invention provides a method for equalizing the capacitance voltage of a modular multilevel converter, which can simultaneously solve the problems of high sorting frequency and high and inconsistent switching frequency of switching devices in the prior art. question

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  • Method for balancing capacitor voltage of modularization multilevel converter
  • Method for balancing capacitor voltage of modularization multilevel converter

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Embodiment Construction

[0047] 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.

[0048] figure 1 The topology of the three-phase modular multilevel converter is shown. It has six three-phase bridge arms. Each bridge arm is composed of N sub-modules and bridge arm inductors cascaded. The output is from the upper and lower bridge arm inductors. lead out. The sub-module is the basic unit of the modular multi-level converter, and the sub-module circuit can be divided into main power circuit, control circuit and communication circuit according to the function. There are three basic structures of the main power circuit: half-bridge structure, full-bridge structure and double-clamp structure, as shown in Figure 2. The control circuit includes a sampling circuit, a driving circuit and a protection circuit, etc. The sampling circuit is used...

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Abstract

The invention discloses a method for balancing capacitor voltage of a modularization multilevel converter. The method comprises the following steps: (1) the present value of submodule capacitor voltage is sampled to obtain increment of capacitor voltage in a power frequency period; (2) the increment of the capacitor voltage and the present value of submodule capacitor voltage are ranked; (3) a new corresponding relation between a drive signal and a submodule is obtained; (4) the drive signal is allocated to the submodule again according to the new corresponding relation. According to the method, the requirement for real-time performance is lower, and the computing resource of controllers is saved, so that the controllers can be used for processing a large-scale MMC system; no bridge arm current needs to be detected, so that the communication complexity among the controllers is simplified, part of the cost of a current sensor is saved, an additional hardware circuit is not needed to be added, and additional system cost is avoided; under the control of the method, all switch frequencies of the submodule are the same, the switch frequency is lower, the switch stresses are consistent and the system thermal design is facilitated and the system reliability is realized.

Description

technical field [0001] The invention belongs to the technical field of power electronic systems, and in particular relates to a method for equalizing capacitor voltage of a modular multilevel converter. Background technique [0002] With the rapid development of clean new energy power generation technologies such as wind power and solar power, the flexible DC transmission technology based on voltage source converters has attracted extensive attention from industry and academia. Compared with conventional multilevel voltage source converters, modular multilevel converters (Modular Multilevel Converter, MMC) have the advantages of high modularity, easy expansion, and less harmonic content in output waveforms. The design scheme avoids the direct series-parallel connection of switching devices, and successfully resolves the contradiction between the huge difference between the power level of switching devices and the power level of the grid. Moreover, this modular system struct...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483H02M7/487
Inventor 邓焰彭浩王昆王莹吕自波李广地
Owner ZHEJIANG UNIV
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