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Island detection method and reference current extremum calculation method for AC/DC hybrid power grid

An AC-DC hybrid, reference current technology, applied in AC network circuits, AC/pulse peak measurement, measurement of electricity and other directions, can solve problems such as the lengthening process of the system returning to a steady state, AC system fault fluctuations, and frequency collapse. , to shorten the recovery time, reduce the fluctuation of the AC voltage amplitude, and achieve the effect of fast and accurate detection

Active Publication Date: 2019-09-13
SICHUAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The existing HVDC islanding detection technology has the following defects: The traditional HVDC islanding detection technology is based on phase and frequency detection. Although the frequency and phase are sensitive to power and can quickly respond to the islanding situation, they cannot be detected during load switching. Larger fluctuations also occur when the AC system fails
In order to avoid false switching of the converter station under the above circumstances, a larger threshold and duration threshold are usually set for the offset phase and frequency, but setting a larger threshold may lengthen the process of the system returning to a steady state, resulting in Frequency collapse and other situations occur, especially when the flexible direct current transmission system supplies power to the passive network. The passive network is a very weak system, so the frequency deterioration will be more serious during the detection and switching process

Method used

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  • Island detection method and reference current extremum calculation method for AC/DC hybrid power grid
  • Island detection method and reference current extremum calculation method for AC/DC hybrid power grid
  • Island detection method and reference current extremum calculation method for AC/DC hybrid power grid

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Embodiment 1

[0051] This embodiment is used to detect whether the method can avoid the misjudgment that the AC line is in an island state due to a fault in the AC system.

[0052] A three-phase short-circuit fault is set at the exit bus of the converter station at the receiving end. The fault occurs in 0.6s and disappears after 50ms. combine Figure 4 , 5 , the output active power of the converter station continued to decrease during the short circuit, reaching the minimum value of -10.6MW at 0.653s, and the power difference was 109.4MW. After that, the active power starts to rise up to the set value. combine Figure 6 , The maximum value during power recovery is 0.49kA, which has a margin of 69% compared with the setting value of 0.828kA.

Embodiment 2

[0054] This embodiment is used to detect whether the method can quickly detect whether the AC line is in an island state.

[0055] refer to figure 2 , the AC line 1 is cut off at 0.6s, and the AC line 2 is cut off at 0.7s to form an isolated island system at the receiving end. The island detection method proposed by the present invention is adopted for the system and a constant AC voltage control is adopted after switching.

[0056] refer to Figure 7 , the curve in the figure shows the change of the voltage effective value U at the outlet bus of the converter station at the receiving end. combine Figure 8 , the curve in the figure shows the variation of frequency f of the island system at the receiving end when the system adopts the islanding detection method proposed by the present invention, combined with Figure 9 , when the AC line 1 was cut off at 0.6s, the frequency and voltage of the receiving end system did not fluctuate, the d-axis reference current of the recei...

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Abstract

The invention relates to the technical field of DC transmission and discloses an island detection method and reference current extremum calculation method for an AC / DC hybrid power grid. The island detection method for the AC / DC hybrid power grid is characterized in that an island is detected according to the change of local electric quantity, namely d-axis reference current, of a flexible DC system after the island is formed. According to the method, a slope input response model is adopted for an outer loop controller, and various disturbances of the power grid can be effectively avoided through calculating, analyzing and setting a reasonable d-axis reference current threshold, thereby achieving accurate judgment on the island condition. The island detection method has the beneficial effects that the response speed to the island of the system is high and the island can be quickly judged; the possibility of misjudgment under a large disturbance can be avoided through setting the reasonable threshold, thereby accurately and reliably distinguishing the island condition from the non-island condition; and the island detection method is convenient to implement and a complicated controllink does not need to be introduced.

Description

technical field [0001] The invention relates to the technical field of direct current transmission, in particular to an island detection method and a reference current extremum calculation method for an AC / DC hybrid power grid. Background technique [0002] The Voltage Source Converter based High Voltage Direct Current Transmission (VSC-HVDC) technology was proposed by Boon-Teck Ooi and others at McGill University in Canada in 1990. It is a voltage source converter based , a new power transmission technology based on self-shutdown devices and pulse width modulation (PWM) technology, this power transmission technology can supply power to passive networks, there will be no commutation failure, no communication between converter stations, and it is easy to form a multi-terminal DC system Etc. As a new generation of DC transmission technology, flexible DC transmission is similar in structure to HVDC, and is still composed of a converter station and a DC transmission line (usual...

Claims

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Application Information

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IPC IPC(8): G01R31/08G01R19/04H02J3/00
CPCG01R31/086G01R31/088G01R19/04H02J3/00H02J3/388H02J2203/20
Inventor 王渝红叶葳李天泽陈勇
Owner SICHUAN UNIV