Method and apparatus for insulation monitoring, and system for generating electricity from renewable energy

A method and a device for insulation monitoring, as well as a system for generating electricity from renewable energy are provided. Alternating-current insulation monitoring is 5 constantly performed at the alternating-current side in a period during which the inverter is shut down. Direct-current insulation monitoring is performed before the inverter is connected to the grid when alternating-current insulation resistance meets a preset normal alternating-current resistance condition and the inverter operates and meets a grid-connected condition. When direct-current insulation resistance meets a preset normal direct-current 0 resistance condition, the inverter is connected to the power grid, and the alternating-current insulation monitoring and the direct-current insulation monitoring stop. The anti-PID device and the alternating-current insulation monitoring device are controlled to alternately operate in the period during which the inverter is connected with the grid. Therefore, insulation monitoring can be performed around the clock while preventing the PID. - 32- Control an altemating-current insulation monitoring device to constantly perform alternating-current insulation monitoring at an Sl0l alternating-current side and control an anti-PID device to operate at a direct-current side when it is monitored that a photovoltaic inverter is shut down Perform, when it is monitored that altemating-current insulation S102 resistance meets a preset normal alternating-current resistance condition and that the inverter operates and meets a grid-connected condition, direct-current insulation monitoring before the inverter is connected to a power grid Control the inverter to be connected to the power grid and stop the altemating-current insulation monitoring and the direct-current S103 insulation monitoring when it is monitored that direct-current insulation resistance meets a preset normal direct-current resistance condition, and control an anti-PID device and the alternating current insulation monitoring device to alternately operate in a period during which the inverter is connected with the grid Figure 1 - 1/7-