An Islanding Detection Method Based on Harmonic Distortion Rate and Frequency

Abstract

The invention discloses an island detection method based on harmonic distortion rate and frequency. The method herein includes the following steps: based on historical data, determining the maximum value (H<1>) of the harmonic distortion rate when a distributive photovoltaic power generation system joints a power grid and the minimum value (H<2>) of the harmonic distortion rate when the distributive photovoltaic power generation system is an island, if (H<1> is greater than H<2>) or the values of H<1> and H<2> can not be determined, and after it is detected that the harmonic distortion rate suddenly increases and lasts for a while, starting the harmonic distortion rate criterion and frequency varying amount to determine an island state; if (H<1> is smaller than H<2>), directly starting the harmonic distortion rate criterion and frequency varying amount to determine an island state. According to the invention, the method herein does not add a disturbing signal to the distributive photovoltaic power generation system, does not affect the quality of the electric energy of the distributive photovoltaic power generation system, and does not cause damage; uses the harmonic distortion rate and frequency, has small detection blind areas, increases the reliability of system island detection; and avoid sudden disturbance in the power grid by using a certain time delay, and prevents temporary change to the detected electric quantity from causing wrong determination of island detection.

Description

technical field [0001] The invention belongs to the technical field of power system new energy control, and in particular relates to an islanding detection method based on harmonic distortion rate and frequency. Background technique [0002] The island effect is a major problem in the protection of photovoltaic power generation systems. An isolated island refers to a grid connected to a distributed photovoltaic generation system (photovoltaic generation, PVG). Due to a fault in some circuits of the grid or a power outage for maintenance, the PVG did not detect the disconnection of the grid in time and stopped running, but continued to supply local loads independently. Phenomenon of power supply, thereby producing an isolated power generation system that is uncontrolled and self-sufficient. [0003] Isolated islands will bring harm to grid maintenance personnel and system equipment, and will also damage the power quality of PVG. The current practical approach is to detect is...

AI Technical Summary

Problems solved by technology

Passive island detection judges whether islanding occurs by monitoring whether the terminal voltage amplitude, frequency, phase, and harmonics output by the inverter are abnormal. The advantage is that it is simple to implement and does not damage the power quality. The disadvantage is that there is a large detection blind zone And the threshold is difficult to determine; active island detection injects a small disturbance signal into the system through the power supply, and then detects the island by measuring the response difference generated by the disturbance signal before and after the island. Quality, destructive; detection based on communication channel uses communication technology between power supply and power system, usually there is no detection blind spot, detection is accurate and reliable, but due to low economy and complex design, it has not been widely used in PVG. With the development of power grid, this method will have great development potential

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