Method and circuit fir detecting ground insulation impedance of photovoltaic array

Abstract

The embodiment of the invention discloses a method and circuit for detecting ground insulation impedance of a photovoltaic array. The circuit is composed of a positive voltage division circuit and a negative voltage division circuit, wherein the resistance ratio of the positive voltage division circuit to the negative voltage division circuit is at least N1, N2, N3 and N4; and N3 is greater than 1 / 5 but less than or equal to 1 / N4, N1 is greater than 1 / N4 but less than or equal to 1 / N2, and 1 / N2 is greater than or equal to N1 but less than 1. The method for detecting the ground insulation impedance of the photovoltaic array comprises the steps of: respectively connecting the positive voltage division circuit and the negative pressure division circuit between a positive bus and a ground line and between the ground line and the negative bus during the detection; when a bus voltage is not greater than the product of a maximum output voltage of the photovoltaic array and the N1, adjusting the positive voltage division circuit and / or the negative voltage division circuit to enable the resistance ratio to be respectively N1 and N2; calculating the ground insulation impedance value of the photovoltaic array based on a serial partial pressure principle; and when the bus voltage is greater than the product, selecting the N3 and the N4 for corresponding operation and calculation so as to obtain a ground insulation impedance value. According to the embodiment of the invention, the problem that the ground insulation impedance cannot be detected exactly within a full voltage range when the differential value of the ground insulation impedances of the positive bus and the negative bus is very great in the prior art is solved.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, in particular to a method and circuit for detecting insulation impedance of a photovoltaic array to ground. Background technique [0002] With the popularity of photovoltaic power generation, the insulation resistance of photovoltaic array PV busbars to ground has gradually attracted the attention and attention of the industry. If the insulation resistance of the photovoltaic array to the ground is poor or the resistance value is lower than a certain value, it will cause the photovoltaic array to form a high voltage to the ground, which will cause the equipment shell to be charged, which will not only easily damage the equipment, but also pose a huge threat to personal safety. Therefore, it is necessary to detect the insulation resistance of the photovoltaic array to the ground, so as to take corresponding adjustment measures in time to ensure that the insulation resistance ...

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Problems solved by technology

[0004] In view of this, the present invention provides a photovoltaic array-to-ground insulation resistance detection method and circuit to solve the problem that the existing detection scheme cannot achieve accurate detection in the full voltage range when the difference between the positive and negative busbars to the ground insulation resistance is large. Detect problems with insulation resistance to ground

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