Detection method and detection circuit for insulation resistance of photovoltaic panels to ground

Abstract

The invention discloses an insulation-against-ground impedance detection method and detection circuit for a photovoltaic cell panel. The main circuit of the detection circuit comprises resistors R1-R6 and switches S1-S2, wherein PV+ is grounded through the R1, R3 and R5 while PV- is grounded through the R2, R4 and R6; one end of the S1 is connected with a linking point of the R3 and R5 while the other end of the S1 is connected with a linking point of the R2 and R4; one end of the S2 is connected with a linking point of the R1 and R3 while the other end of the S2 is connected with a linking point of the R4 and R6; compared with a condition that two switches are both switched off, after the S2 is closed, the equivalent parallel resistance of the R+ is decreased while the equivalent parallel resistance of the R- is increased; and on the contrary when the S1 is closed. The detection method comprises the steps of if the voltage-to-ground ratio of V1 to V2 of the positive electrode and the negative electrode of the photovoltaic cell panel is not smaller than a first threshold value when the S1 and the S2 are both switched off, controlling the S2 to be closed; if the V1 to V2 is smaller than a second threshold value, controlling the S1 to be closed; and or otherwise, controlling the S2 or the S1 to be closed. By adoption of the insulation-against-ground impedance detection method and detection circuit, the insulation-against-ground impedance detection accuracy for the photovoltaic cell panel is improved.

Description

technical field [0001] The invention relates to the technical field of power electronics, and more specifically, to a detection method and a detection circuit for the insulation resistance of a photovoltaic battery panel to ground. Background technique [0002] In the photovoltaic power generation system, since the photovoltaic panels are placed in the open air, affected by weather factors such as dust, rain, snow, and heavy fog, the insulation resistance of the positive and negative poles of the photovoltaic panels to the ground will change, which not only affects the performance of the photovoltaic power generation system. Safe operation, but also a threat to personal safety. Therefore, before the start-up of the photovoltaic power generation system, it is necessary to detect the insulation resistance of the photovoltaic panels to the ground, so as to detect and eliminate potential safety hazards in time. [0003] The basic idea of ​​testing the insulation resistance of p...

AI Technical Summary

Problems solved by technology

However, when R + >>R - (i.e. V 1 >>V 2 ), since the negative voltage of the photovoltaic panel to the ground is very small, so simply changing R - The equivalent parallel resistance of the photovoltaic panel will not change the voltage of the positive and negative poles of the photovoltaic panel to the ground too much, then k 2 with k 1 The gap is very small, due to sampling and quantization errors, truncation errors and rounding errors in the data processing process, it will cause k 2 -k 1 The calculation accuracy is low, which in turn leads to R + / / R - The calculation accuracy is low

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