Reactive-power-disturbance-based grid-connected island detection method for photovoltaic system

Abstract

The invention discloses a reactive-power-disturbance-based island detection method for a photovoltaic grid-connected power generation system. The method is characterized by comprising the following steps of: detecting the voltage amplitude and frequency of a grid connection point in real time by using the system, judging whether the voltage amplitude and frequency of the grid connection point reach system protection threshold values or not, and if the voltage amplitude and frequency of the grid connection point reach the system protection threshold values, enabling an anti-island protection signal; and if the voltage amplitude and frequency of the grid connection point do not reach the system protection threshold values, controlling an inversion output signal of the system by using bilateral intermittent periodical reactive power disturbance to realize the change of the output voltage amplitude and frequency of the system, and detecting the change of the output voltage amplitude and frequency of the system in real time, wherein a bilateral intermittent period comprises a reactive power output time period and an intermittent time period, reactive power disturbance values of each time period take the voltage period of a power grid voltage and the sampling period of the system as regulation variables, and the reactive power disturbance realizes the change of the output voltage amplitude and frequency of the system by the inversion control of a reactive power ring. By the method, the rapid and accurate power-grid island running detection of the photovoltaic system can be realized, and the disturbance to the power-grid system can be reduced.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic grid-connected power generation, in particular to a detection method for photovoltaic system grid-connected islands based on reactive power disturbance. Background technique [0002] Energy has become a major issue of common concern to the international community. New energy such as solar energy has been paid more and more attention due to its renewable and clean characteristics, and grid-connected photovoltaic power generation is an important way to utilize solar energy on a large scale. The photovoltaic system converts the direct current generated by the solar cells into alternating current through the grid-connected inverter, and directly supplies power to the grid without requiring energy storage devices such as batteries, and the construction and maintenance costs of the system are low. [0003] When the power grid is abnormal, the photovoltaic power generation system and some local load...

AI Technical Summary

Problems solved by technology

Passive detection technology generally monitors the state of the power grid, such as voltage and frequency, as the basis for judging whether the power grid is faulty. The advantage of passive monitoring is that it does not require external disturbances, so it will not affect the power quality. When the load power is balanced, the system voltage and frequency will not change significantly after the power grid is cut off, and the island operation phenomenon cannot be detected

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