Bidirectional active power disturbance island detection method

Abstract

The invention discloses a bidirectional active power disturbance island detection method. The method comprises the following steps of: adding the disturbance quantity of positive and negative delta I into grid-connected current; calculating an absolute value of difference between Uold and Unew; comparing the absolute value of the difference between the Uold and the Unew with a set maximum permissible value of voltage difference between the Uold and the Unew; and if frequency that the absolute value of the difference between the Uold and the Unew is continuously greater than the set maximum permissible value of the voltage difference between the Uold and the Unew is greater than or equal to a set value, detecting an island phenomenon. By adoption of the bidirectional active power disturbance island detection method, the island phenomenon can be timely and effectively detected, and harmonic wave is slightly introduced to a common coupling point.

Description

Technical field: [0001] The invention relates to an island detection technology in the application field of a grid-connected inverter in a new energy power generation system, especially a photovoltaic grid-connected power generation system. Background technique: [0002] In the photovoltaic power generation system, the electric energy generated by the photovoltaic array is connected to the power grid after passing through the electric energy conversion device - photovoltaic grid-connected inverter. The system diagram is shown in the appendix figure 1 shown. The output of the grid-connected inverter is connected to the power grid after passing through the isolation transformer, and its connection point is called the public coupling point PCC. [0003] When the power grid is interrupted due to electrical failure, misoperation or natural factors, etc., if the grid-connected inverter cannot detect the power failure of the grid in time and continue to transmit energy outward, a ...

AI Technical Summary

Problems solved by technology

Active islanding detection methods usually use frequency perturbation method, harmonic injection method, etc. These detection methods can improve detection efficiency and reduce detection blind spots, but these methods have a certain impact on grid-connected power quality and increase grid-connected waveform harmonics. Wave

The traditional unidirectional active power disturbance method is an active detection method, which will cause the input side of the inverter to deviate from the normal operating point, especially in the photovoltaic grid-connected inverter, usually through the power control of the photovoltaic grid-connected inverter, so that The photovoltaic array works at the maximum power point. If the traditional unidirectional active power disturbance islanding detection method is used, the photovoltaic array will deviate from the maximum power point. The photovoltaic array will work at a certain value between MPPT (maximum power point tracking) and unidirectional active power disturbance. at a point of balance (see attached figure 2 ), which deviates from the maximum power point and reduces the system efficiency

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