Coordinated voltage equalization start-up method for flexible direct current transmission system based on combined converters

A flexible DC and power transmission system technology, applied to electrical components, power transmission AC networks, output power conversion devices, etc., can solve problems such as voltage charging imbalance, and achieve the effect of raising the average voltage

Active Publication Date: 2019-08-06
XJ ELECTRIC
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Problems solved by technology

[0008] The purpose of the present invention is to provide a coordinated start-up method for flexible direct current transmission system based on combined converters to solve the problem that the traditional start-up control strategy easily causes unbalanced voltage charging of each basic converter unit sub-module in the converter station

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  • Coordinated voltage equalization start-up method for flexible direct current transmission system based on combined converters
  • Coordinated voltage equalization start-up method for flexible direct current transmission system based on combined converters

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Embodiment Construction

[0031] The method for coordinated voltage equalization start-up of a flexible direct current transmission system based on combined converters provided by the present invention is applied to a passive start-up system or an active joint start-up system. This embodiment takes passive start-up as an example. figure 1 It is a combined converter flexible direct current transmission system that supplies power to passive systems. It is composed of N basic converter units connected in series to supply power to passive systems. Wherein, in this embodiment, the basic commutation unit is a single MMC.

[0032] The coordinated voltage equalization startup method of the flexible direct current transmission system based on combined converters generally includes three steps: A, pre-charging phase, B, controllable voltage equalization charging phase, and C, unlocking operation phase.

[0033] Wherein, the pre-charging stage means that in this stage, the sub-modules of each basic converter unit...

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Abstract

The invention relates to a method for coordinated voltage equalization start-up of a flexible direct current transmission system based on a combined converter, wherein the combined converter is composed of N basic converter units connected in series for voltage boosting. For one control cycle, the number of submodules removed in each bridge arm of each basic converter unit is determined, and then the corresponding number of submodules in each bridge arm is removed, and other input submodules are charged. Among the cutting principles of the number of sub-modules, the first principle can ensure that the average value of the capacitor voltage of the sub-modules of all basic converter units in the station can reach and stabilize around the rated value. The second principle can realize the charging equalization of the sub-module capacitors of each basic converter unit. Moreover, after the number of sub-modules in each bridge arm is determined, the sub-modules with higher charging voltage are preferentially removed, which can realize the voltage balance among the sub-modules in the basic converter unit. Therefore, through this start-up method, the basic Coordinated voltage equalization among converter units starts.

Description

technical field [0001] The invention relates to a coordinated voltage equalization starting method for a flexible direct current transmission system based on a combined converter, and belongs to the technical field of direct current transmission system start-up. Background technique [0002] With the rapid development of modern power grids and the upgrading of power electronics technology, flexible DC transmission systems based on Modular Multilevel Converter (MMC) technology have made great progress and gradually realized engineering applications. However, compared with the traditional direct current transmission system (also known as grid commutated converter high voltage direct current transmission system, Line Commutated Converter Based High Voltage Direct Current, LCC-HVDC), its voltage level and transmission capacity need to be further improved. [0003] Referring to the topology of the high-voltage transmission system of the traditional DC transmission system, the MMC...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M1/36H02J3/36
CPCH02J3/36H02M1/36H02M1/0067Y02E60/60
Inventor 马焕吴金龙王先为张浩杨美娟胡丁文
Owner XJ ELECTRIC
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