Low-temperature refrigeration control method, device and system for air conditioner unit

The invention discloses a low-temperature refrigeration control method, device and system for an air conditioner unit. The method comprises the following steps: when the air conditioner unit is started to enter a running state of low-temperature refrigeration, detecting the opening and closing state of an exhaust pressure switch of the unit; if the exhaust pressure switch is in a closing state, reducing the wind speed gear of an outdoor fan of the unit according to a first preset rule until the exhaust pressure switch is turned off or the wind speed gear is reduced to the lowest gear. The method solves the technical problems that when the air conditioner unit in the prior art is in the running state of low-temperature refrigeration, the unit has the phenomenon of running with liquid as the exhaust pressure of the unit is low, and the running reliability of the unit is low.