Insulation resistance detection circuit and method

Abstract

The application discloses an insulation resistance detection circuit and method, which relate to the grid-connected field of inverters and are used for detecting whether the DC input end of the inverter is short-circuited to ground or has low impedance. The insulation resistance detection circuit includes: a controller, an inverter circuit, a first DC voltage source, a second DC voltage source, a filter circuit, and a switch circuit; the controller is used to disconnect the first relay, close the second relay or switch the second relay The switching state of at least one relay; according to the first measured value between the positive input terminal of the inverter circuit and the ground point, it is determined whether the positive input terminal of the inverter circuit is short-circuited to ground or has low impedance; according to the negative input terminal of the inverter circuit The second measured value between the ground point and the ground point determines whether the negative input terminal of the inverter circuit is short-circuited to ground or has low impedance; wherein, the first relay refers to a relay with at least one resistor connected in parallel among the M relays, and the second relay refers to Relays other than the first relay among the M relays.

Description

technical field [0001] The present application relates to the field of grid-connected inverters, and in particular to an insulation resistance detection circuit and method. Background technique [0002] In the scenario where a DC power generation device (such as a solar cell) is connected to an AC grid, it needs to be connected to the grid through an inverter. [0003] In the prior art, for a non-isolated AC power grid that is not connected to a transformer on the grid side, when the chassis of the inverter is not safely grounded (protecting earth, PE) or is poorly grounded, if the DC input terminal of the inverter is short-circuited to ground (the impedance to ground is zero) or low impedance, if it is directly connected to the grid at this time, the DC input end of the inverter will form a short circuit with the AC grid, resulting in an explosion. Contents of the invention [0004] Embodiments of the present application provide an insulation resistance detection circuit...

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Problems solved by technology

[0003] In the prior art, for a non-isolated AC power grid that is not connected to a transformer on the grid side, when the chassis of the inverter is not safely grounded (protecting earth, PE) or is poorly grounded, if the DC input terminal of the inverter is short-circuited to ground (the impedance to ground is zero) or low impedance, if it is directly connected to the grid at this time, the DC input terminal of the inverter will form a short circuit with the AC grid, resulting in a bombing

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