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A Threshold Setting Method for Harmonic Islanding Detection

A technology of island detection and harmonics, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve the problem of difficult setting of the action threshold, and achieve the effects of easy implementation, improved engineering practical value, and simple principle

Active Publication Date: 2021-03-12
NARI TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The purpose of the present invention is to propose a threshold setting method for harmonic island detection in view of the problem that the action threshold of the harmonic island detection method mentioned in the above background technology is difficult to set

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  • A Threshold Setting Method for Harmonic Islanding Detection
  • A Threshold Setting Method for Harmonic Islanding Detection
  • A Threshold Setting Method for Harmonic Islanding Detection

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Embodiment 1

[0017] In order to better understand this embodiment, an islanding detection method formed by combining harmonic voltage and frequency changes before and after the islanding is described first. This method judges the island when both the rise of the harmonic voltage and the deviation of the frequency after the island meet the operating conditions. Since the frequency does not change when the grid background harmonic is large, misjudgment is avoided. Moreover, due to the combination of harmonic voltage, the frequency criterion is not easy to be misjudged, and a relatively small frequency action threshold can be set, thereby improving sensitivity, reducing detection blind spots, and avoiding over / under frequency detection and harmonic detection methods when used alone Existing problems. Specific steps are as follows:

[0018] Step 1: Set the inverter switching frequency as f C , modulation frequency f S 50Hz, collect and calculate the 5th, 7th, 11th, 13th harmonic voltage an...

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Abstract

The invention discloses a threshold setting method for harmonic island detection, which belongs to the technical field of photovoltaic power generation systems. The present invention obtains the load impedance from the load capacity, approximates the system impedance from the short-circuit capacity, and then converts it to the harmonic impedance at the corresponding frequency, and can obtain the change of the harmonic impedance before and after the island, thereby obtaining the change multiple theory of the harmonic voltage before and after the island Reference value, set the action threshold. The invention provides a reference method for setting the action threshold of harmonic island detection, and improves its engineering practical value.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation systems, and more precisely, the invention relates to a threshold value setting method for harmonic island detection. Background technique [0002] The occurrence of isolated islands will bring a series of problems, and the grid-connected photovoltaic power generation system should have the ability to detect and protect isolated islands. Among the common islanding detection methods, there are various problems whether it is over / under frequency, over / under voltage islanding detection method or pure harmonic islanding detection method. Combining the changes of harmonic voltage and frequency before and after the island can constitute a new type of islanding detection method, which detects the island when the harmonic voltage rises after the island and the frequency shifts to a certain extent. Since the frequency does not change when the background harmonics of the power grid ar...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38G01R31/00
CPCG01R31/00H02J3/383H02J3/388Y02E10/56
Inventor 唐冠军陈永华陈汹王森许士光李雪明薛峰罗剑波陈勇周汝勇邹亚平
Owner NARI TECH CO LTD