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A method of island detection

An islanding detection and islanding technology, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve the problems of power quality influence, difficulty in finding power matching point, voltage impact, etc., and achieve small power quality influence, fast and effective islanding detection Functional, easy-to-implement effects

Inactive Publication Date: 2017-06-13
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

However, if the method of periodically inputting capacitors is adopted, if the input capacitor is large, the grid-connected operation may cause uninterrupted voltage shocks to the distribution network system with a small capacity, which will have a certain impact on the power quality; secondly, this method The reliability of the switch is high, and periodic switching will shorten the service life of the switch
The second is to cooperate with the switch at the PCC point, such as figure 1 The middle switch S1, when the switch S1 is turned off, the switch S2 is closed, and the external capacitor is incorporated into the system, which destroys the power balance of the system
The disadvantage of this method is that the switching of the capacitor needs to cooperate with the switch at the PCC point, and the capacitor must be detected that the switch at the PCC point has been disconnected. If the detection device fails, the island detection will fail.
In addition, this method must find the power matching point, but the power flow of the power system changes frequently, and it is difficult to find a fixed power matching point
[0007] Based on the above analysis, it can be seen that the voltage / frequency detection method can effectively detect islands when the output power of the DG system inverter and the local load power are unbalanced, but when the output power of the DG system inverter and the local load power are balanced, the method failure

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Embodiment Construction

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] The islanding detection method based on harmonic detection capacitor switching combined with voltage / frequency detection includes the following steps:

[0027] Step 1: Use the over / under frequency device and the over / under voltage device to detect the frequency and voltage of the PCC point in real time, and use the active detection method, that is, the harmonic detection device to detect the harmonic distortion rate in real time;

[0028] Step 2: Determine whether the detected frequency and voltage exceed the set threshold, if yes, go to step 5, if not, judge whether the harmonic distortion rate exceeds the threshold, if yes, go to step 3; if not, go to step one;

[0029] Step 3: Start delaying for 1S. If the voltage, frequency and harmonic distortion rate are detected not exceeding the threshold after the 1S delay ends, return to step 1; if the harmonic distorti...

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Abstract

An islanding detection method, which combines the passive method with the active method, adopts over / under frequency and over / under voltage methods to quickly detect the island without affecting the power quality; when the island occurs, and the power in the island system matches When using the capacitor switching method with harmonic detection as the criterion, the power matching of the system can be destroyed, and the voltage and frequency in the system will change, thereby detecting islanding.

Description

technical field [0001] The invention belongs to the field of anti-islanding protection for large-scale new energy centralized grid connection, is an anti-islanding protection detection scheme combining passive detection and active detection, and particularly relates to an islanding detection method for voltage / frequency detection and harmonic detection capacitor switching . Background technique [0002] Islanding means that after the power grid fails, the distributed generation system still supplies power to the surrounding loads, thus forming an uncontrollable local power supply network. Unplanned islands will bring some serious problems to the safe and stable operation of the power system. For example, the voltage and frequency in the island cannot be controlled, which may cause damage to the user's equipment; the lines in the island are still live, which may endanger the maintenance personnel. personal safety etc. The main function of island detection is to disconnect t...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/00G01R31/08
Inventor 郑涛王燕萍袁飞王增平黄雯刘逸辰
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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