Anti-islanding grid-connection switch protection method for distributed type power supply system and grid-connection switch device

The invention discloses an anti-islanding grid-connection switch protection method for a distributed type power supply system and a grid-connection switch device. The distributed type power supply system is converted into alternating current power through an inverter, and the alternating current power is converted into electric energy of corresponding voltage through a transformer and is connected into a power distribution network through a grid-connection switch; the grid-connection switch protection method comprises the following steps: injecting certain disturbance into the output power, the frequency or the phase of a grid-connection inverter by controlling the grid-connection inverter, and detecting the output situation of the inverter, wherein when a power grid works normally, a disturbance signal cannot change the output characteristic of the grid-connection inverter under the balance action of the power grid; when the power grid fails or powers down, the output characteristic of the grid-connection inverter can be quickly accumulated and exceed an allowable range under the feedback action of the disturbance signal, so that quick detection is realized; if the output current, the output voltage and the output power, detected by injection of the disturbance signal into the grid-connection inverter, of the grid-connection inverter exceed the allowable range, a signal is generated to trigger a protection device of the grid-connection switch to enable the protection device to trip.