Insulation resistance detection circuit and method and photovoltaic system applying same

Abstract

The invention relates to an insulation resistance detection circuit and method and a photovoltaic system applying the same. The circuit comprises a voltage sampling module which is used for sampling avoltage value of a ground PE relative to a common-connection negative electrode PV- of each solar cell panel and the voltage value of each solar cell panel; a detection resistor; a first branch circuit which is used for connecting detection resistor between the ground PE and each solar cell panel; and a second branch which is used for connecting the detection resistor between the ground PE and apositive electrode of each solar cell panel. According to the invention, the method achieves the calculation of the insulation resistance according to different states of the insulation resistance detection circuit. The photovoltaic system comprises a plurality of solar cell panels, an inverter and the insulation resistance detection circuit. The insulation resistance detection precision can be improved, and meanwhile, the system cost is saved.

Description

technical field [0001] The invention belongs to the field of power electronics, and in particular relates to a novel insulation resistance detection scheme applied in a photovoltaic inverter system. Background technique [0002] In a photovoltaic system, the insulation resistance (insulation resistance) of the DC side to the ground characterizes the insulation performance of the DC system. If the impedance is too low, the leakage current generated by it will pose a threat to people. Therefore, the current safety standards require that when the insulation resistance of the DC side to the ground is less than a certain value, the system is not allowed to operate in parallel with the grid. Based on this, the photovoltaic inverter needs to detect the insulation resistance value of the photovoltaic system. [0003] In the utility model patent with the application number 201320481819.5, a high-precision multi-channel common ground DC power supply insulation resistance detection ci...

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Problems solved by technology

However, because the essence of this scheme is to calculate the insulation resistance through the voltage difference before and after the common ground switch is opened and closed, and the closing of the common ground switch will cause the detection terminal voltage to decrease, so the improvement effect of this scheme is limited

[0004] It can be seen that the existing insulation resistance detection scheme still has the problem of low accuracy when the insulation resistance of the common ground terminal of the photovoltaic system to the ground itself is relatively low.

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