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An Equivalence Method for AC and DC Systems Based on Ward Equivalence

An AC-DC system, equivalent method technology, applied in the field of value calculation, can solve problems such as unfavorable receiving end system power flow evacuation

Active Publication Date: 2020-10-09
STATE GRID CORP OF CHINA +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] With the construction of the UHV DC project, the DC transmission capacity continues to increase, and the DC landing point is becoming more and more concentrated. The existing DC single-layer access method will not be conducive to the power flow evacuation of the receiving end system. Support and other aspects will cause a series of problems

Method used

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  • An Equivalence Method for AC and DC Systems Based on Ward Equivalence
  • An Equivalence Method for AC and DC Systems Based on Ward Equivalence
  • An Equivalence Method for AC and DC Systems Based on Ward Equivalence

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0181] (1) IEEE 30-node standard system

[0182] Table 1 presents the detailed results of IEEE-30 node division.

[0183] Table 1 IEEE-30 node division

[0184]

[0185] Apply the equivalent program to the standard 30-node example for equivalent calculation, the boundary equivalent machine (treated as a PQ node), the boundary node virtual branch impedance value, and boundary parallel compensation data are shown in Table 2, Table 3, and Table 4.

[0186] Table 2 Boundary equivalent machine (unit: MW / MVAR)

[0187]

[0188] Table 3 Boundary node virtual branch impedance value (pu.)

[0189]

[0190] Table 4 Boundary parallel compensation value (pu.)

[0191]

[0192] In order to verify the accuracy of the equivalent results, it is necessary to compare the power flows of the pre-equivalent system and the post-equivalent system. In the same operation mode, the power flow calculation is performed on the equivalent system, and the results are shown in Table 5.

[01...

Embodiment 2

[0201] Example 2: 36-node AC-DC hybrid system of China Electric Power Research Institute.

[0202] Taking the 36-node AC-DC hybrid system of China Electric Power Research Institute as an example, the equivalent branch method and the equivalent power source method proposed in this report are used to conduct equivalent analysis on the AC-DC hybrid system.

[0203] (1) Equivalent branch method

[0204] First calculate the power flow for the test system. The AC node power flow results (pu.) on both sides of the DC line are shown in Table 7, where the positive direction is related to Figure 13a , Figure 13b same definition.

[0205] Table 7 Power flow results

[0206]

[0207] Table 7, P 33 and Q 33 represent active power and reactive power injected by node 33 respectively, P 34 and Q 34 Respectively represent the active power and reactive power injected by node 34; V 33 and Respectively represent the node 33 voltage amplitude and phase angle, V 34 and represent ...

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Abstract

The invention relates to a WARD equivalence-based alternating current direct current system equivalence method. The alternating current direct current system equivalence method comprises the steps ofestablishing each basic element model, obtaining nodes in the whole network to be used as basic data, and determining the data format; performing power flow calculation on the whole network and obtaining the power flow solution of the whole network; dividing the nodes into an internal node set, a boundary node set and an external node set, wherein the elements in each set are arranged from small to big based on node numbers; forming a node admittance matrix of the whole network, and forming partitioned node admittance matrixes used for equivalence calculation according to the divided node sets; calculating an equivalence matrix, a boundary equivalence capacitor and a boundary equivalent injection power; forming a new structural data body, and storing the basic data of the system after equivalence to be defined as R<empc>; and performing power flow calculation on the system after equivalence, making comparison on the power flow results of the retained branch and the nodes before and after equivalence, and selectively outputting the power flow results. By virtue of the alternating current direct current system equivalence method, it is effectively ensured that the power flow error ofthe retained system before and after equivalence can be in the minimum, so that the method can be applied to an extra-high voltage direct current layering system.

Description

technical field [0001] The invention relates to the field of calculation of UHV AC / DC equivalents in power systems, in particular to an AC / DC system equivalent method based on WARD equivalents. Background technique [0002] With the construction of the UHV DC project, the DC transmission capacity continues to increase, and the DC landing point is becoming more and more concentrated. The existing DC single-layer access method will not be conducive to the power flow evacuation of the receiving end system. There will be a series of problems in terms of support and so on. Due to the layered connection of UHV DC, the topology of the DC system is more complex, and the interaction between the AC and DC systems and between the two layers of receivers has also become a research issue that needs to be paid attention to. In order to accurately simulate the transient characteristics of large-scale AC and DC power grids with hierarchical access during asymmetric faults, or to design AC ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/36
CPCH02J3/36H02J2203/20Y02E60/60
Inventor 郭贤珊赖清平马为民薛英林吴方劼石岩杨一鸣张涛胡志坚罗福玲付颖杜晓磊郝致远李达季一鸣程炜赵峥常云辉勇智韩旭杉
Owner STATE GRID CORP OF CHINA
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