Insulation resistance detection circuit and detection method of photovoltaic inverter, and photovoltaic inverter

Abstract

This application discloses an insulation resistance detection circuit and detection method of a photovoltaic inverter, and the photovoltaic inverter. The detection circuit is composed of a first switch, a second switch, a first detection resistor and a second detection resistor. The first switch is connected in series with the first detection resistor to form a first branch; and a first end of the first branch is connected to a positive bus of a photovoltaic inverter and a second end of the first branch is connected to a ground wire. The second switch is connected in series with the second detection resistor to form a second branch; and a first end of the second branch is connected to a negative bus of the photovoltaic inverter and a second end of the second branch is connected to a ground wire. According to the detection circuit, the total ground insulation resistance of the photovoltaic array can be measured precisely in a full input voltage range. The detection circuit and detection method can be applied to any inverter with the any number of paths of inputs; and no additional device is needed for a multi-path series string input.

Description

technical field [0001] The invention relates to photovoltaic inverter technology, in particular to an insulation resistance detection circuit and detection method of a photovoltaic inverter and a photovoltaic inverter. Background technique [0002] With the popularization of photovoltaic grid-connected power generation applications, the safety of photovoltaic grid-connected power generation systems has received more and more attention. At present, the photovoltaic grid-connected standards of many countries have regulations on the insulation resistance of non-isolated photovoltaic grid-connected inverters, such as VDE-0126, UL1741, etc. It requires that the insulation resistance of the positive and negative terminals of the photovoltaic input of the photovoltaic inverter to the chassis (ground wire) is not less than the specified value before grid-connected power generation can be performed. Therefore, in the corresponding non-isolated grid-connected inverter products, it is...

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Problems solved by technology

However, the existing insulation resistance detection methods are not suitable for multi-input inverters. When it is necessary to measure the insulation resistance of multi-channel photovoltaic (PV), multiple resistors and switches need to be added. With the increase of detection circuits and calculation methods, the detection circuits and calculation methods are becoming more and more complex, and the circuits and methods are not universal.

Or, it is necessary to change the photovoltaic input through illumination changes or artificially, so as to obtain multiple equations to solve the insulation resistance. This detection method is difficult to realize automatic control and has poor practicability.

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