Distributed power source island detecting method based on grid-tied point characteristic harmonic wave voltage measurement

Abstract

The invention discloses a distributed power source island detecting method based on grid-tied point characteristic harmonic wave voltage measurement. A distributed power source is connected with an inverter, and the inverter and a transformer access power grid make up a distributed power source grid tying system sequentially via an inlet filter. The distributed power source island detecting method includes selecting at least two groups of characteristic harmonic wave times as reference subharmonic waves for island detection according to IGBT (insulated gate bipolar transistor) switch frequency of the inverter; synchronously sampling the voltage between the output end of the inverter and grid-tied points between the transformer and the power grid, and acquiring reference subharmonic wave voltage corresponding to the selected characteristic harmonic times after conversion and disintegration; judging whether the reference subharmonic voltages exceed the preset detection threshold values of the harmonic voltage or not, if yes, judging that island effect occurs when duration time exceeds the preset time limit. The method is reliable and easy to implement and is high in power grid applicability and applicable to actual use of projects.

Description

technical field [0001] The invention relates to the technical field of distributed power island detection, in particular to a method for detecting distributed power islands based on the measurement of characteristic harmonic voltages of grid-connected points. Background technique [0002] In recent years, with the increasingly prominent energy shortage and environmental problems, new energy power generation technology has developed rapidly with the strong support of national policies, and a large number of new energy power generation devices are connected in the form of distributed generation (DG). Into the power grid, while relieving the pressure on the power grid, it also brings problems in terms of power quality and operation planning to the power grid, among which the island effect is a major problem. [0003] In distributed generation grid-connected power generation systems such as photovoltaic power generation, wind power generation, and fuel cell power generation, whe...

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Problems solved by technology

The disadvantage of this method is that the fluctuation during normal operation of the power grid may also cause misjudgment

In addition, if the output power of the distributed power source matches the load power, when the grid power supply is interrupted, the voltage and frequency of the grid-connected point will not change enough to detect whether the islanding effect occurs, that is, there will be a large detection blind zone

The existing active islanding detection method is to give a certain disturbance to the amplitude, frequency, and phase of the inverter output current, so that the frequency or phase of the output voltage will be shifted accordingly to determine whether the islanding effect occurs, but the detection method Due to the addition of disturbances, it will affect the power quality of the grid

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