Improved reactive power disturbance island detection algorithm

Abstract

The invention relates to an improved reactive power disturbance island detection algorithm, which comprises the following steps: 1) when an island occurs, detecting the forward zero crossing of the voltage of a PCC point; 2) adding a periodic reactive disturbance quantity to reduce the influence of the periodic reactive disturbance quantity on the grid-connected power quality; 3) detecting the voltage amplitude and frequency of the PCC point, and judging whether an island occurs or not according to the voltage amplitude or voltage frequency of the PCC point when one of the following four conditions is met; 4) if the voltage frequency fi of the PCC point is greater than or equal to 49.5 Hz and less than or equal to 50.5 Hz after the island occurs, setting a disturbance quantity conversion criterion, realizing unidirectional large disturbance according to the local load property through the disturbance quantity conversion criterion, and quickly increasing the disturbance quantity along with the frequency change so as to trigger an island protection device. The algorithm has the advantages of being high in stability, high in detection speed and small in influence on electric energy quality.

Description

technical field [0001] The invention relates to the technical field of distributed photovoltaic grid-connected island detection, in particular to an improved reactive power disturbance island detection algorithm. Background technique [0002] Although the passive island detection method has the advantages of fast detection speed, good economy, and simple implementation, it usually has the disadvantages that the threshold is difficult to set, and it is easy to fall into the detection blind spot when power matching, which greatly restricts the passive island detection method. Widely used, so the passive detection method is often used in conjunction with the active detection method; although the active island detection method reduces the detection blind area through the introduction of the disturbance strategy, when the power grid is in normal operation for a long time, the inverter The disturbance of the output current frequency of the inverter will lead to the increase of cur...

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Problems solved by technology

[0002] Although the passive island detection method has the advantages of fast detection speed, good economy, and simple implementation, it usually has the disadvantages that the threshold is difficult to set, and it is easy to fall into the detection blind spot when power matching, which greatly restricts the passive island detection method. Widely used, so the passive detection method is often used in conjunction with the active detection method; although the active island detection method reduces the detection blind area through the introduction of the disturbance strategy, when the power grid is in normal operation for a long time, the inverter The disturbance of the output current frequency of the inverter will lead to the increase of current harmonics, which will have an adverse effect on the power quality of the grid.

At the same time, the islanding detection algorithm based on active current disturbance may cause grid voltage fluctuations due to active current amplitude disturbances, and even lead to instability of the entire system; An improved reactive power disturbance islanding detection algorithm is very necessary

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