The present disclosure relates to an active neutral-point clamped (ANPC) three-level converter, and a method and controller for controlling thereof. The ANPC three-level converter includes at least one bridge leg, and a controller. Each of the at least one bridge leg includes multiple input terminals, an output terminal, and multiple switches connected between the multiple input terminals and the output terminal. The multiple input terminals include a first input terminal, a second input terminal, and a third input terminal. The multiple switches include a first external switch, a first internal switch, a first clamp switch, a second external switch, a second internal switch, and a second clamp switch. The method for controlling the NPC three-level converter includes a method for controlling the ANPC three-level converter to stop operating, and a method for controlling the ANPC three-level converter to start to operate.