Grid-connected inverter island detection method based on parameter adaptive Sandia frequency shift (SFS)

Abstract

The invention discloses a grid-connected inverter island detection method based on parameter adaptive Sandia frequency shift (SFS). The method uses a digital correlation principle for detecting a phase difference angle between a common coupling point voltage and an inverter output current, initial chopped wave coefficient cf0 in the SFS is made to automatically adjust along with inverter frequency detection errors according to the detected phase difference angle, and meanwhile a positive feedback gain K in the SFS can be made to carry out adaptive modulation along with the difference of local loaded quality factors. The grid-connected inverter island detection method based on the parameter adaptive SFS overcomes the defect that a dilutive effect caused by traditional SFS due to frequency detection errors under a multi-inverter grid-connected condition can lead to the failure of island detection, solves the problem that the island detection is difficult and even can not be achieved when the local loaded quality factors are quite high, and quickly achieves the island detection and island protection under the condition that power supply quality of a distributed type power generation system is ensured.

Description

technical field [0001] The invention belongs to the technical field of islanding detection of a distributed grid-connected power generation system, and in particular relates to a method for detecting islanding of a grid-connected inverter based on a parameter adaptive Sandia frequency offset method. Background technique [0002] With the intensification of the energy crisis and the enhancement of environmental protection awareness, distributed power generation systems based on renewable energy such as solar energy and wind energy have attracted more and more attention. These renewable energies are usually converted into electrical energy first, and then sent to the grid through grid-connected inverters. The islanding effect is a phenomenon that may occur in distributed grid-connected power generation systems. The so-called island phenomenon means that when the power grid is interrupted for some reason, the inverter still transmits power to the grid, and forms a self-suffici...

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Problems solved by technology

[0005] The object of the present invention is to aim at the deficiencies in the traditional Sandia frequency offset method, to provide a grid-connected inverter island detection method based on the parameter adaptive Sandia frequency offset method, which can overcome the traditional Sandia frequency offset method in multiple Under the grid-connected condition of the inverter, the dilution effect caused by the frequency detection error will lead to the failure of the island detection, and it also solves the problem that the island detection is difficult or even impossible to detect when the local load quality factor is high, without affecting the distributed On the premise of the power supply quality of the power generation system, the islanding detection and islanding protection can be quickly completed, and it has the advantage of small blind area of ​​the islanding detection

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