Islanding detection method based on voltage harmonic fault component

Abstract

The invention discloses an islanding detection method based on voltage harmonic fault component. Through detecting differences presented by voltage signals at specific frequencies of 150 Hz, 250 Hz and 350 Hz in the case of normal grid-connected operation and islanding operation, the islanding operation state is detected. A sliding data window is used for calculating absolute values |DeltaU3|, |DeltaU5|, and |DeltaU7| for voltage specific subharmonic fault components at the grid-connected inverter end, and whether islanding happens according to the sizes of the |DeltaU3|, the |DeltaU5|, and the |DeltaU7|. The quality of electric energy outputted by the grid-connected inverter is not influenced, the transient response of the system is not disturbed, the sampling frequency is lowly required, and hardware realization is facilitated. The method of the invention can quickly and effectively detect islanding effects in the most serious islanding condition defined by the IEEE Std.1547.1 standard, is applicable to various broken circuit conditions, and has good practicality.

Description

technical field [0001] The invention belongs to the technical field of grid connection of distributed power sources, and in particular relates to an island detection method based on voltage harmonic mutation. Background technique [0002] The island effect means that in the distributed power generation system, when the grid power supply trips due to a fault accident or power outage maintenance, the distributed grid-connected power generation system at each user end fails to detect the power outage in time and cuts itself off from the mains network. A self-sufficient power supply island power generation system is formed by the grid-connected power generation system of distributed power stations and its connected loads. [0003] The island effect makes the voltage and frequency out of control. If the distributed generation system does not have the ability to adjust the voltage and frequency, and there is no voltage and frequency protection relay to limit the deviation of the v...

AI Technical Summary

Problems solved by technology

Local islanding detection methods can be further divided into two types: passive and active: the passive method only judges the occurrence of islanding based on the abnormal voltage or frequency output by the grid-connected inverter, and usually the passive method has relatively large detection blind spots; and The active method injects disturbances into the power grid, and uses the corresponding changes in system voltage, frequency, and impedance caused by the disturbance signals to judge the occurrence of islanding. Although this method can effectively reduce detection blind spots, it will have certain impact on power quality. Impact

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