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A Unified Power Flow Controller for Unbalanced Systems

A technology of power flow controller and converter, applied in flexible AC transmission system, multi-phase network asymmetry reduction, AC network to reduce harmonics/ripples, etc., can solve problems such as limiting large-capacity UPFC applications, and achieve High performance-to-price ratio, small number of components, and capacity-enhancing effects

Active Publication Date: 2015-08-05
CHINA EPRI SCIENCE & TECHNOLOGY CO LTD +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

These limit the application of large capacity UPFC

Method used

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  • A Unified Power Flow Controller for Unbalanced Systems
  • A Unified Power Flow Controller for Unbalanced Systems
  • A Unified Power Flow Controller for Unbalanced Systems

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0051] A three-phase four-wire MMC topology scheme with split capacitors on the series side of a unified power flow controller for unbalanced systems provided by the present invention is as follows: image 3 As shown, the unified power flow controller includes a static synchronous compensator 1 and a static synchronous series compensator 2; an upper split capacitor 3 and a lower split capacitor 4 are arranged between the static synchronous compensator 1 and the static synchronous series compensator 2; the upper split capacitor The capacitor 3 and the lower split capacitor 4 are connected in parallel with the static synchronous compensator 1 and the static synchronous series compensator 2 respectively after being connected in series; the upper split capacitor 3 and the lower split capacitor 4 are connected in series to form a split capacitor branch; the midpoint of the split capacitor branch is connected to The neutral point of the series transformer 11 of the static synchronous...

Embodiment 2

[0066] This embodiment is basically the same as Embodiment 1, but the difference is:

[0067] The positions of the reactors in the inverter 8 and the inverter 10 are different. The reactor in this embodiment is connected in series on the side of the positive and negative bus bars, and is used to suppress output harmonics of the converter device.

[0068] Specifically, the converter 8 is composed of three phases; the three phases are connected in parallel; each phase is composed of two upper and lower bridge arms connected in series; Each bridge arm of the upper and lower bridge arms includes a reactor and N submodules with the same structure; after the submodules of each bridge arm are cascaded, one end is connected to the starting circuit 6; after the submodules of each bridge arm are cascaded, The reactor at the other end is connected in series with the reactors of the other two-phase bridge arms to form the positive and negative busbars of the converter 8 .

[0069] The c...

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Abstract

The invention relates to a unified power flow controller used for an unbalanced system. The unified power flow controller comprises a static synchronization compensator and a static synchronization series compensator. An upper part split capacitance and a lower part capacitance are arranged between the static synchronization compensator and the static synchronization series compensator. The upper part split capacitance and the lower part split capacitance are connected in series and then respectively connected with the static synchronization compensator and the static synchronization series compensator in parallel. The upper part split capacitance and the lower part split capacitance are connected in series and then a split capacitance branch circuit is formed. A midpoint of the split capacitance branch circuit is connected with a neutral point of the static synchronization series compensator. Output ends of the static synchronization compensator and the static synchronization series compensator are respectively connected with a power grid. The unified power flow controller is convenient to split-phase control and modularization design, small in running loss, good in voltage control capacity, good in zero-sequence current controlling, few in element quantity, low in cost and high in cost performance.

Description

technical field [0001] The invention relates to a unified power flow controller in the field of flexible alternating current transmission, in particular to a unified power flow controller for an unbalanced system. Background technique [0002] The neutral point of the power grid with a voltage level of 110kV and above adopts a direct grounding method. When the three-phase load is asymmetrical, zero-sequence current will appear on the line. Three-phase voltage unbalance is an important index to measure the power quality of power grid. With the improvement of people's requirements for power quality, the problem of voltage imbalance is receiving more and more attention. In the three-phase system, the causes of voltage imbalance mainly come from two aspects: the output voltage imbalance of the generator and the load asymmetry. Theoretically speaking, the output voltage of the generator is not completely symmetrical and has a certain degree of unbalance, but it should be limite...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/26H02J3/01
CPCY02E40/50Y02E40/16Y02E40/10Y02E40/40
Inventor 王轩喻劲松闫殳裔李欣武守远何维国
Owner CHINA EPRI SCIENCE & TECHNOLOGY CO LTD