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Step-down operation control method for hybrid MMC flexible direct current power transmission system

A flexible DC and power transmission system technology, applied in the direction of AC network voltage adjustment, AC power input conversion to DC power output, electrical components, etc. Reduced voltage operation ability, the effect that is conducive to stable operation

Active Publication Date: 2019-11-19
GUANGZHOU BUREAU CSG EHV POWER TRANSMISSION
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Problems solved by technology

[0004] The purpose of the present invention is to provide a hybrid MMC flexible direct current transmission system step-down operation control method to solve the problem that the bridge arm sub-modules cannot be equalized during the step-down operation of the hybrid MMC flexible direct current transmission system

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  • Step-down operation control method for hybrid MMC flexible direct current power transmission system

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Embodiment Construction

[0018] In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] Hybrid MMC consists of 6 bridge arms, each bridge arm consists of N sub-modules and bridge arm reactor L 0 Composition, the bridge arm sub-module includes a certain number of full-bridge sub-modules and half-bridge sub-modules, the topology and electrical quantities are marked as figure 1 shown.

[0020] According to the basic working principle of MMC, when the three bridge arms are completely symmetrical: DC working current I dc Evenly distributed among the 3 phase units, that is, the DC current in each phase unit is The AC current in each phase unit is equally divided between the upper and lower bridge arms, where a, b, and c represent phases A, B, and C. Accordingly, taking the phase unit of phase A as an example, the...

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Abstract

The invention discloses a step-down operation control method for a hybrid MMC flexible direct current power transmission system. The method includes the following steps: determining the step-down coefficient eta on an MMC direct current side and the stable voltage U on an MMC alternating current side according operation requirements; obtaining the alternating current system voltage Us and reactivepower Qv of the MMC alternating current side during step-down operation, obtaining the power factor of the MMC alternating current side, entering the next step if a condition shown in the descriptionis met, and otherwise, returning to the last step; judging the operation conditions of the MMC alternating current side, controlling MMC to absorb a certain reactive power if Us is greater than U, and adjusting the power factor to 1.45 eta; and controlling the MMC to emit a certain reactive power output if Us is less than or equal to U, and adjusting the power factor to 1.45 eta. The control method can be realized by depending on the self and original control capabilities of a control system, so that the problems of the unable voltage-sharing of the bridge arm sub-module of a hybrid MMC flexible direct current power transmission system during step-down operation can be solved, the capabilities of the hybrid MMC to realize step-down operation can be strengthened, and fault ride-through capabilities under the condition of direct current voltage reduction such as direct current line insulation faults can be enhanced.

Description

technical field [0001] The invention relates to flexible direct current transmission technology, in particular to a hybrid MMC flexible direct current transmission system step-down operation control method. Background technique [0002] In recent years, flexible direct current transmission technology has developed rapidly, and UHV flexible direct current transmission demonstration projects have gradually started construction. Compared with conventional high-voltage direct current transmission, UHV direct current transmission has higher requirements on the system insulation level. Under environmental conditions such as insulation problems that are prone to occur, if the DC overhead line is still operating at the rated DC voltage (UHV), a high failure rate may occur. In order to improve the reliability and availability of the transmission line, it is necessary to use a step-down On the other hand, in the case of DC line fault DC voltage reduction, maintaining the stability and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/16H02J3/36H02M7/483
CPCH02J3/16H02J3/36H02M7/483Y02E40/30Y02E60/60
Inventor 郑星星徐攀腾宋述波李金安包威杨学广周登波朱博谷裕李建勋焦石李倩顾硕铭郭云汉柳林海
Owner GUANGZHOU BUREAU CSG EHV POWER TRANSMISSION
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