A chopper circuit comprises a first chopper circuit (1) and a second chopper circuit (2). A current input terminal of the first chopper circuit (1) is electrically connected to a VDC positive terminal of an intermediate direct-current circuit, and a current output terminal of the first chopper circuit (1) is electrically connected to a VDC negative terminal of the intermediate direct-current circuit. A current input terminal of the second chopper circuit (2) is electrically connected to the VDC positive terminal of the intermediate direct-current circuit, and a current output terminal of the second chopper circuit (2) is electrically connected to the VDC negative terminal of the intermediate direct-current circuit. The first chopper circuit (1) and/or the second chopper circuit (2) is used for being turned on when the bus voltage of the intermediate direct-current circuit exceeds a preset value to consume part of the bus voltage so as to decrease the bus voltage to a specified value. In this way, stability of a traction converter is improved, and further stability of a traction system is improved.
