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A control method for reducing the fluctuation rate of mmc sub-module capacitor voltage

A technology of capacitor voltage and control method, applied in the field of power system, can solve the problems of restricting the popularization and application of flexible DC transmission technology, increasing the weight, volume and cost of flexible DC converter valve, etc., to achieve light weight, reduce capacitance value, reduce Effect of Capacitor Voltage Fluctuation Rate

Active Publication Date: 2019-05-31
ZHEJIANG UNIV +3
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] From the above comparative analysis, it can be seen that with the increase of voltage level and system capacity, the weight, volume and cost of the flexible DC converter valve will increase greatly, thus limiting the flexibility Popularization and Application of DC Transmission Technology

Method used

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  • A control method for reducing the fluctuation rate of mmc sub-module capacitor voltage
  • A control method for reducing the fluctuation rate of mmc sub-module capacitor voltage
  • A control method for reducing the fluctuation rate of mmc sub-module capacitor voltage

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Embodiment Construction

[0018] 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.

[0019] From the mathematical model of MMC, it can be seen that the bridge arm current includes DC components, fundamental wave air volume and double frequency air volume, which can be expressed as follows:

[0020]

[0021] The average switching function of MMC can be expressed as:

[0022]

[0023] In this way, the average capacitive current of the sub-module can be obtained as:

[0024]

[0025] The relationship between the average capacitor voltage of the sub-module and the average capacitor current of the sub-module is:

[0026]

[0027] The formula (3) and formula (4) can be obtained simultaneously, and the expression of the average capacitor voltage of the sub-module is:

[0028]

[0029] According to formula (1), the effective valu...

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Abstract

The invention discloses a control method for reducing the capacitor voltage fluctuation rate of a modular multilevel converter (MMC) sub module. According to the control method, on the basis of a reasonable controller design, a second harmonic component of the average capacitance voltage of the sub module is suppressed to be zero, so that the capacitance value of the sub module is reduced substantially under the circumstance of the same capacitor voltage fluctuation rate and the light-weight trend of a flexible direct-current converter valve is realized. Therefore, on the same capacitor voltage fluctuation rate condition, the capacitance value of the MMC sub module is reduced substantially and the light-weight trend of the flexible direct-current converter valve is realized. Because of noneed of injection of bridge arm ring current, the losses of the flexible direct-current converter valve are not increased.

Description

technical field [0001] The invention belongs to the technical field of power systems, and in particular relates to a control method for reducing the voltage fluctuation rate of an MMC sub-module capacitor. Background technique [0002] The flexible DC converter valve based on Modular Multilevel Converter (MMC) is the core equipment of flexible DC transmission technology. The construction of high-voltage and large-capacity flexible DC The development of the flexible direct current converter valve puts forward an urgent demand. Compared with the ±500kV / 3000MW flexible direct-current converter valve, the mature ±320kV / 1000MW flexible direct-current converter valve and the ±200kV / 400MW flexible direct-current The weight is 6×57 tons, the floor area is 34×22m (length×width), and the cost is about 200 million yuan; the total weight of a unit of ±320kV / 1000MW flexible DC converter valve is 6×69 tons, and the floor area is 39.87×22m (length × width), the cost is about 400 million ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/00
CPCH02M7/00
Inventor 徐政肖晃庆徐雨哲王世佳李继红陆翌
Owner ZHEJIANG UNIV
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