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Method and system for detecting isolated islands

A technology of island detection and photovoltaic power generation system, applied in the field of electric power, can solve the problems of dangerous maintenance, isolated islands where the power grid cannot control self-supply power supply, and electric shock of maintenance personnel.

Active Publication Date: 2017-01-18
GREE ELECTRIC APPLIANCES INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] The island effect is that when the power grid stops working due to faults, accidents or power outage maintenance, the grid-connected photovoltaic power generation system fails to detect the power outage in time and cannot quickly cut itself off from the network, forming a photovoltaic power generation system that should be connected to the grid. The isolated island where the system supplies power to the surrounding loads, and the main control system of the power grid generally cannot control the isolated island of self-sufficient power supply
When the power grid is out of power, it generally needs to be repaired, and the independent power supply of the island will bring danger to the maintenance, which may cause the maintenance personnel to get an electric shock

Method used

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  • Method and system for detecting isolated islands
  • Method and system for detecting isolated islands
  • Method and system for detecting isolated islands

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Experimental program
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Embodiment 1

[0037] figure 1 It is a flow chart of an island detection method provided by the embodiment of the present application.

[0038] like figure 1 As shown, the island detection method provided in this embodiment includes the following steps:

[0039] S101: Acquire a voltage signal.

[0040] Obtain the voltage signal of the grid-connected point of the photovoltaic power generation system. That is, the voltage signal at the connection point between the filter inductance of the inverter of the photovoltaic power generation system and the grid is obtained.

[0041] S102: Extracting the negative sequence component of the current fundamental wave.

[0042] Extracting the current fundamental wave negative sequence component from the obtained voltage signal specifically includes the following steps: first extracting the voltage fundamental wave negative sequence component from the voltage signal, and then obtaining the current fundamental wave negative sequence component from the vol...

Embodiment 2

[0053] figure 2 A structural diagram of an island detection system provided by another embodiment of the present application.

[0054] like figure 2 As shown, the islanding detection system provided by this embodiment includes a voltage detection module 10 , a negative sequence component extraction module 20 , a calculation module 30 , a proportional-integral module 40 and a signal feedback module 70 .

[0055] The voltage detection module 10 is used to obtain the voltage signal of the grid connection point 51 of the photovoltaic power generation system. The grid connection point 51 is the connection point between the filter inductance of the inverter 50 of the photovoltaic power generation system and the grid.

[0056] The negative sequence component extraction module 20 is used to extract the negative sequence component of the current fundamental wave from the voltage signal, specifically including a first extraction unit (not shown) for extracting the negative sequence ...

Embodiment 3

[0062] image 3 A structural diagram of an island detection system provided by another embodiment of the present application.

[0063] Such as image 3 It shows the connection relationship and block diagram of the islanding detection system.

[0064] u dc * is the reference value of DC bus voltage, u dc is the detected DC bus voltage, e a 、e b 、e c is the grid-connected point voltage, i a i b i c is the grid current, F is the grid voltage negative sequence component extraction module, αβ / dq transforms the physical quantity from the two-phase stationary coordinate system to the two-phase rotating coordinate system to realize the park transformation, and dq / αβ transforms the physical quantity from the two-phase rotating coordinate system to the two-phase The phase-stationary coordinate system realizes the inverse park transformation.

[0065] When the power grid is working normally, the voltage imbalance at the grid-connected point is less than 2%, which has little ef...

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Abstract

The application provides an island detection method and an island detection system. The detection method comprises the steps of: firstly obtaining a voltage signal of a grid-connection point of a photovoltaic power generation system, obtaining an electric current fundamental wave negative sequence component from the voltage signal, adding an electric current inner ring reference value of the inverter of the photovoltaic power generation system, and then subtracting a feed value, thus obtaining a first control signal; performing proportional integral control to the first control signal to obtain a second control signal, using the second control signal to control the inverter to output three-phase alternating current, and using the electric current signal of a power grid which is separated from the inverter by a filter inductor as a feed signal, thus completing detection on island effect; when three phases, two phases or one phase of the power grid is in outage, three-phase voltage of the grid-connection point is imbalance, the electric current fundamental wave negative sequence component of which the content exceeds a certain number appears, and thereby the island effect can be detected based on the positive feedback principle.

Description

technical field [0001] The present application relates to the field of electric power technology, and more specifically, to an islanding detection method and system. Background technique [0002] The island effect is that when the power grid stops working due to faults, accidents or power outage maintenance, the grid-connected photovoltaic power generation system fails to detect the power outage in time and cannot quickly cut itself off from the network, forming a photovoltaic power generation system that should be connected to the grid. The isolated island where the system supplies power to the surrounding loads, and the main control system of the power grid generally cannot control the isolated island of self-sufficient power supply. When the power grid fails, maintenance is generally required, and the independent power supply of the isolated island will bring danger to the maintenance, which may cause the maintenance personnel to get an electric shock. Therefore, in orde...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/00
Inventor 刘瑞孙丰涛
Owner GREE ELECTRIC APPLIANCES INC