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Method for detecting piconet island state

A detection method and micro-grid technology, applied in the field of micro-grid, can solve problems such as unsatisfactory fast detection and slow detection time

Inactive Publication Date: 2010-08-04
HUAZHONG UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method can still detect the island state when the difference in active power is small, and is not affected by system disturbances. However, when the difference in active power is large, the detection time of this method is slow, which cannot meet the requirements of fast detection.

Method used

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  • Method for detecting piconet island state
  • Method for detecting piconet island state
  • Method for detecting piconet island state

Examples

Experimental program
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Effect test

example

[0041] Using PSCAD / EMTDC electromagnetic transient simulation software to establish as figure 2 The simulation circuit shown.

[0042] The main grid is an ideal power supply of 50MVA, and the distributed power supply DG adopts a synchronous generator with a capacity of 5.4MVA, active power of 4.6MW, reactive power of 2.4Mvar, and an inertia coefficient of 6.07s. Load 1 and load 2 adopt a constant power model, the total active power is 6.0MW, and the reactive power is 2.4Mvar. The nominal frequency of the system is 50Hz.

[0043] In this example, take V limit = 0.93 p.u, f' min = 0.2Hz / s, f' max =0.5Hz / s, t=2S, α set = 3°.

[0044] When the three-phase circuit breakers BRKs1, BRKs2, BRK1, and BRK2 are all closed, the microgrid is connected to the grid and runs stably. After 7 seconds, the three-phase circuit breaker BRKs1 is disconnected, and the microgrid forms an island state. At this time, the measured microgrid The grid frequency change rate and phase change are as fo...

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Abstract

The invention discloses a method for detecting a piconet island state according to the self-characteristic of a piconet. The method comprises the following steps of: (1) detecting electrical characteristic value when the piconet runs; (2) judging whether the voltage at a load end is higher than the definite value or not, if yes, entering step (3), and if not, considering that the piconet is not in the island state; (3) judging whether the frequency changing rate is higher than the upper limit of the definite value or not, if yes, sending out a trip signal and then finishing, and if not, entering step (4); (4) detecting and judging whether the frequency changing rate is higher than the lower limit of the definite value or not, if yes, judging whether the phase difference is more than the phase difference setting valve or not, if yes, finishing the detection and sending out the trip signal, and if not entering step (5); and (5) after delaying for a period of time, judging whether the phase difference is more than the phase difference setting valve or not, if yes, sending out the trip signal, and if not, considering that the piconet is in the island state. Compared with the existing detection method, the method has the characteristics of rapid and reliable detection, and guarantees comparatively high anti-interference capability at the same time.

Description

technical field [0001] The invention belongs to the microgrid technology, and in particular relates to a method for detecting the island state of the microgrid. The method is a comprehensive method based on the coordinated judgment of the frequency change rate and the phase change amount. Background technique [0002] With the improvement of social requirements for power supply reliability and the rapid development of renewable clean energy power generation technology, microgrid as a new form of power grid has received more and more attention, but the application of microgrid still faces a series of problems that need to be solved scientific and technological issues. Among them, the microgrid islanding effect caused by faults or disturbances is a huge challenge. Under the premise that the current island effect utilization technology is not very mature, the formation of isolated islands will have a huge impact on users, and it also violates the highest standards of power sys...

Claims

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Application Information

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IPC IPC(8): H02H7/26
Inventor 林湘宁赵志敏李正天薄志谦郑胜翁汉琍
Owner HUAZHONG UNIV OF SCI & TECH
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