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Method for detecting islanding by frequency deviation applying pulse current interference

A technology of frequency offset and pulse application, applied in the field of solar photovoltaic power generation, can solve problems such as extension

Inactive Publication Date: 2010-07-14
SOUTHEAST UNIV
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  • Application Information

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Problems solved by technology

In addition, when cf is positive and the load is inductive, or cf is negative and the load is capacitive, the detection is faster, otherwise the time required for detection will be extended

Method used

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  • Method for detecting islanding by frequency deviation applying pulse current interference
  • Method for detecting islanding by frequency deviation applying pulse current interference
  • Method for detecting islanding by frequency deviation applying pulse current interference

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Embodiment Construction

[0035] The present invention chooses timely application of current amplitude disturbance to improve the traditional frequency offset method, the basic flow chart of its control and detection is as follows Figure 5 shown. First of all, the frequency offset method applies a small disturbance to the inverter output current to change the frequency, so that the frequency of the PCC point is different from the normal situation when the power grid is faulty; considering the harmonic influence on the power grid, THD image 3 It can be seen that the value range of cf is (0, 0.03). The present invention takes cf=0.01 for verification. Secondly, once the frequency monitoring system detects that the frequency of the PCC point continues to change in one direction, it is considered that there is a possibility of a grid fault, and a current amplitude interference signal that can quickly determine the possibility of a fault is applied, such as Figure 6 shown. Finally, if the voltage monito...

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Abstract

The invention relates to a method for detecting islanding by frequency deviation applying pulse current interference, which comprises the steps of: selecting an AFD method of which the chopping rate cf is equal to 0.01 to perform small-range deviation on the frequency of a point of common coupling; if detecting that the frequency of the point of common coupling fluctuates continuously towards a direction, considering that the failure of a power grid possibly exists, and aiming at completing islanding detection and disconnecting synchronization before high-speed reclosing, applying current amplitude interference with an appropriate period; once discovering that the possibility of the failure is removed, revoking the current interference; and when detecting that voltage frequency exceeds the limit of OVP / UVP and OFP / UFP, performing anti-islanding protection. The method can accelerate the detection of the failure and reduce detection dead zones, and has the small influence on the power grid. The detection method can make up the defects caused by independent use of the two methods, judge the occurrence of the failure accurately and quickly, and provide guarantee for the safe and reliable operation of the power grid by adopting corresponding measures.

Description

technical field [0001] The invention relates to a method for detecting frequency offset islands by applying pulse current interference, which is an improvement to the traditional frequency offset (AFD) method and belongs to the technical field of solar photovoltaic power generation. Background technique [0002] With the rapid development of the economy, the demand for energy in all countries in the world has increased sharply. Energy consumption and environmental protection have become the two bottlenecks of sustainable economic development. The development and utilization of renewable energy has become the consensus of the world. As a new green energy, solar energy is being rapidly popularized and applied due to its advantages of inexhaustibility, no pollution, and no limitation of geographical resources. In the long run, photovoltaic power generation will be one of the most potential strategic alternative power generation technologies. Solar photovoltaic power generation...

Claims

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Application Information

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IPC IPC(8): H02H7/26G01R31/00
Inventor 林明耀顾娟林克曼
Owner SOUTHEAST UNIV
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