Photovoltaic grid-connected island detection algorithm based on abrupt phase change and active phase shifting

Abstract

Disclosed is a photovoltaic grid-connected island detection algorithm based on abrupt phase change and active phase shifting. The photovoltaic grid-connected island detection algorithm comprises the steps of (1) collecting a grid-connected current frequency value, a common point voltage phase and a grid-connected current phase through a phase-locked loop apparatus; (2) setting upper and lower threshold values of a frequency, a common point voltage and a phase deviation threshold value of a grid-connected current; according to national island detection standard, setting the frequency threshold valve |f-f0| to be less than or equal to 0.5Hz; and setting the phase difference |delta <phi>| to be less than or equal to 2 degrees; and (3) when the grid-connected current frequency, or the common point voltage and the phase deviation of the grid-connected current exceed the corresponding threshold values, starting island protection; and when the current frequency of the grid-connected point and the |delta <phi>| are not greater than the corresponding threshold values, applying phase perturbation, wherein theta<SMS> is equal to 5 degrees sin(pi / 2*delta f / 3), on an inverted output current until the current frequency of the grid-connected point or the |delta <phi>| is greater than the corresponding threshold value, starting island protection. By adoption of the photovoltaic grid-connected island detection algorithm, seamless switching of different algorithms can be realized; detection blind regions can be reduced while the detection speed can be accelerated when a passive method is adopted singly; and in addition, the power grid current THD can be lowered when an active phase shifting method is adopted singly.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation. Background technique [0002] Island operation means that when the power grid is interrupted due to electrical failure, misoperation or natural factors, the photovoltaic micro-grid power supply system continues to output power to the grid and supply power to local loads as an independent power source, thus forming a self-sufficient power supply that the grid cannot control isolated island. When the distributed photovoltaic power generation system is operating in an isolated state, it may affect the power quality or even damage the electrical equipment, and may endanger the personal safety of maintenance personnel in severe cases. Therefore, no matter from the aspect of safety or reliability, the islanding operation status should be detected effectively in time, and the photovoltaic inverter should be disconnected from the point of common connection (PCC), which is the islan...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to propose a photovoltaic grid-connected island detection algorithm based on phase mutation and active phase shift, to solve the problem that the active method causes the current THD of the grid-connected point to increase and the passive method has a large detection blind area

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