Method and apparatus for detecting insulation impedance of direct current side of photovoltaic inverter

A method for detecting insulation impedance of a direct current side of a photovoltaic inverter, wherein the photovoltaic inverter comprises a direct current input terminal, a positive terminal of a direct current bus, a negative terminal of the direct current bus, a signal ground, and a protective earthing, and the direct current input terminal of the photovoltaic inverter is used to connect at least one string of photovoltaic panels;

• and
• the method comprises the following steps:
• sampling a voltage of the protective earthing and a voltage of the positive terminal of the direct current bus, respectively;
• obtaining a first voltage difference between voltages of the protective earthing at different moments and a second voltage difference between voltages of the positive terminal of the direct current bus at different moments;
• and
• calculating the insulation impedance of the direct current side of the photovoltaic inverter based on the first voltage difference, the second voltage difference, a resistance of an equivalent resistor between each terminal of the photovoltaic inverter and the signal ground, and resistances of equivalent resistors between the positive terminal and the negative terminal of the direct current bus and the protective earthing.

An apparatus for detecting insulation impedance of a direct current side of a photovoltaic inverter, wherein the apparatus comprises:

• a voltage sampling unit, configured to sample a voltage of a protective earthing and a voltage of a positive terminal of a direct current bus of the photovoltaic inverter;
• and
• a processing unit, comprising a calculating unit for calculating a first voltage difference between voltages of the protective earthing at different moments and a second voltage difference between voltages of the positive terminal of the direct current bus at different moments;
• and
• calculating the insulation impedance of the direct current side of the photovoltaic inverter based on the first voltage difference, the second voltage difference, a resistance of an equivalent resistor of each terminal of the photovoltaic inverter to a signal ground, and resistances of the equivalent resistors between the positive terminal and a negative terminal of the direct current bus and the protective earthing.