Insulation resistance detection circuit and insulation resistance detection method

Abstract

The invention discloses an insulation resistance detection circuit and an insulation resistance detection method. The insulation resistance detection circuit comprises a positive busbar-to-earth voltage sampling circuit, which is used for sampling positive busbar-to-earth voltage; a positive busbar-to-earth voltage amplifying circuit, which is used for amplifying the sampled positive busbar-to-earth voltage, and comprises a first primary amplifying circuit and a first secondary amplifying circuit; a negative busbar-to-earth voltage sampling circuit, which is used for sampling negative busbar-to-earth voltage; a negative busbar-to-earth voltage amplifying circuit, which is used for amplifying the sampled negative busbar-to-earth voltage, and comprises a second primary amplifying circuit and a second secondary amplifying circuit; and a state switching circuit, which is used to switch connection between a positive busbar and a grounding point, connection between a negative busbar and the grounding point, and connection between earth and the grounding point to enable the insulation resistance detection circuit to be in different working states.

Description

technical field [0001] Example embodiments of inventive concepts relate to an insulation resistance detection circuit and a detection method thereof. Background technique [0002] Before the photovoltaic inverter is connected to the grid, it is necessary to detect the insulation resistance of the DC input side to the ground. Low insulation resistance not only threatens the safety of field technicians, but also seriously affects the service life of solar panels. Therefore, insulation resistance detection is an essential function of photovoltaic inverters. [0003] At present, the insulation resistance detection circuit usually adopts the principle of a balanced bridge. The balanced bridge method can only detect the decrease of the insulation resistance of a certain pole, and the measurement result is inaccurate for the decrease of the insulation resistance of the positive and negative poles at the same time. In the balanced bridge method, two ground-to-ground voltage divide...

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Problems solved by technology

First, the insulation resistance detection circuit connected to the DC bus for a long time does not have a self-test function, which will lead to potential safety hazards in the system; second, the low accuracy of insulation resistance detection will affect the judgment of the control system and further increase the safety of the system Hidden danger

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