Why should the grid-tie inverter stop working when power failure?
When installing photovoltaic system, some people will hold the mentality of "even if the power grid is cut off, if there is the sun, their home can also use the electricity". The reality is that, when the power grid is cut off, their home photovoltaic system will only be in the sun, will also stop running, and also can't use the electricity.
The reason for this phenomenon is that the grid-tie inverter must be equipped with anti-island device. When the grid voltage is zero, the inverter will stop working. Anti-island device is a necessary device for all grid-connected photovoltaic inverters. The reason for this is mainly for the safety consideration of the power grid. When the power grid is cut off, maintenance personnel are ready to repair the circuit. Therefore, the national standard stipulates that photovoltaic grid-tied inverters must have island-effect detection and control functions.
Island effect detection methods include passive detection and active detection. The passive detection method detects the amplitude of voltage and current at the output terminal of grid-tie inverter. The inverter does not add interference signals to the power grid. This method does not cause grid pollution, nor will there be energy loss. And active detection refers to the grid inverter, timing, actively exert some disturbance signal of power grids, such as frequency and phase movement. Due to the power grid can be as an infinity of voltage source, a power grid when the interfering signal will be absorbed by power grid, power grid in the event of power failure, the jamming signal will form a positive feedback, will eventually form the frequency or voltage levels, which can determine whether the islanding.