Island detection method based on combination of phase mutation and active frequency drift

Abstract

The invention discloses an island detection method based on the combination of phase mutation and active frequency drift, and belongs to the field of anti-islanding protection of large-scale new energy centralized grid connection. The island detection method based on the combination of phase mutation and active frequency drift comprises the steps that (1) the phase difference delta phi between grid connection output current of an inverter and voltage of a public coupling point and the frequency f of the voltage of the public coupling point are detected; (2) whether the delta phi is larger than phi is judged, if yes, the step (5) is executed, and if not, the step (1) is executed again; whether the f is smaller than fmin or larger than fmax is judged, if yes, the step (5) is executed, and if not, the step (3) is executed; (3) frequency disturbance is added to the grid connection output current of the inverter through the active frequency drift technology in every period, and the frequency f' of the voltage of the public coupling point is detected; (4) whether the f' is larger than the fmax is judged, if yes, the step (5) is executed, and if not, the step (1) is executed again; (5) an island protection action is adopted. The island detection method based on the combination of phase mutation and active frequency drift resolves the problem that a single passive detection method fails under the condition of a resistance-similar load, has no detection blind area, and can effectively detect an island.

Description

technical field [0001] The invention belongs to the field of anti-island protection for large-scale new energy centralized grid connection, and in particular relates to an island detection method based on the combination of phase mutation and active frequency offset. Background technique [0002] Islanding means that after the power grid fails, the distributed generation system still supplies power to the surrounding loads, thus forming an uncontrollable local power supply network. Unplanned islands will bring some serious problems to the safe and stable operation of the power system. The main function of island detection is to disconnect the distributed power supply in time when the distributed system is separated from the main network, so as to prevent unplanned island operation. Currently commonly used islanding detection methods can be divided into three categories: remote method, passive detection method, and active detection method. The passive detection method is to...

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Problems solved by technology

If the load is a capacitive load or an inductive load, after the current passes through the RLC load, the offset angle set by the AFD method will be superimposed on the load phase angle. At this time, if the offset angle set by the AFD method is in the opposite direction to the load phase angle , will reduce the performance of the AFD method. When the offset angle set by the AFD method and the load phase angle just offset, the AFD method will fail

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