Island detection method based on negative sequence power positive feedback

Abstract

The invention discloses an island detection method based on negative sequence power positive feedback, which belongs to the technical field of distributed generation system detection. A negative sequence power positive feedback loop is added in a distributed generation (DG) system, and when a microgrid is converted into island operation from grid-connected operation, microgrid voltage is acted with inverter output current through the positive feedback loop to increase negative sequence power, so an island can be detected by analyzing the square root H of the negative sequence power. The method comprises the following steps of: calculating the square root H of the DG output negative sequence power in the microgrid and setting the threshold theta 1 of H; and then judging whether the island occurs or not, namely judging whether the island occurs or not according to the set value of H. The method is simple in principle and wide in application range; the island can be effectively detected under various failure conditions and other terrible conditions; the method is not affected by a pseudo island; the requirement on application on site can be met; and the method has practical engineering significance.

Description

technical field [0001] The invention relates to the technical field of distributed power generation system detection, in particular to an island detection method based on negative sequence power positive feedback. Background technique [0002] When a grid-connected distributed generation (distributed generation, DG) is disconnected from the large grid and continues to supply power to the local load RL in the event of a large grid failure, it is called island operation. Islanding detection, as a necessary link in the transition of microgrid (local power supply) operation mode, has received more and more attention. [0003] Islanding detection methods are roughly divided into three categories: (1) Passive detection methods, that is, detecting the characteristics of changes in electrical quantities such as voltage, frequency, and power output, to determine the occurrence of an islanding state. The advantage of this method is that the principle is simple and has no influence on...

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Problems solved by technology

Its characteristic is that it can reduce or eliminate the blind area of ​​island detection, but the active disturbance it introduces has a negative impact on power quality, so most of these methods are destructive

(3) Switch state detection method, which uses communication to detect islands. This type of method is simple in principle and has a small blind area, but the cost of equipment is high and the structure design is complicated. It has not been widely used in island detection.

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