Island detection method and device

Abstract

The invention discloses an island detection method and device. According to the method, a real time voltage angle is obtained according to power grid three-phase voltage calculation, a synchronous voltage angle is further determined according to a phase-locked loop based on the real time voltage angle; under normal circumstances, the real time voltage angle is approximately equal to the synchronous voltage angle; when an island and phase jump of grid point voltage occur, the real time voltage angle also changes suddenly with the phenomenon to enable a phase jump value to exist between the real time voltage angle and the synchronous voltage angle; if the average value of the voltage phase jump value of the grid point is larger than a preset jump threshold value in one circulation period, then the occurrence of the island is determined. The island detection method and device are simple in control process and convenient to achieve; the island can be detected in the one circulation detection period after occurrence, and therefore the detection efficiency is high; disturbance quantity is not needed to be added into the output of an inverter, and the output electric energy quality of the inverter can not be influenced; determination is conducted according to the average value of the phase jump, all interference factors are excluded, and the detection precision is improved; detection dead zones are reduced.

Description

technical field [0001] The present application relates to the technical field of power grid monitoring, in particular to an islanding detection method and device. Background technique [0002] Island effect, that is, when the power supply system of the power company stops working due to failure, accident or power outage maintenance, the photovoltaic grid-connected power generation system installed at each user end fails to detect the power outage state in time and cannot quickly cut itself off from the mains network. A self-sufficient power supply island phenomenon that cannot be controlled by a power company that results in a photovoltaic grid-connected power generation system supplying power to surrounding loads. The island effect may have adverse effects on the entire power distribution system equipment and the equipment at the user end, such as endangering the life safety of power maintenance personnel, affecting the protection switch action program on the power distribu...

AI Technical Summary

Problems solved by technology

[0004] Active island detection is to control the inverter so that there is a certain disturbance in the output current, frequency or phase. When the power grid is normal, due to the balance of the power grid, these disturbances cannot be detected. When the power grid is disconnected, the inverter output The effects of these disturbances will quickly accumulate, and finally the voltage or frequency will exceed the allowable range, thereby detecting the occurrence of islanding; although this type of method has high detection accuracy, the control method is complicated, and the increased disturbance reduces the output of the inverter. power quality

[0005] Passive islanding detection is to detect the islanding effect according to the voltage and frequency changes at the output terminal of the inverter when the grid is powered off; this type of method has a large detection blind spot, such as over / undervoltage and over / underfrequency When the local load carried by the transformer and its output power are close to match, the deviation of voltage and frequency will be very small or even zero, and islanding cannot be detected

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