Abstract: A multi-voltage level direct current grid system and a control protection method, the direct current grid system comprising: at least two direct current buses; at least one direct current transformer, one end of which is connected to a first direct current bus while another end is connected to a second direct current bus or a lead-out wire, which may achieve direct current voltage conversion; and at least one lead-out wire current limiter, one end of the lead-out wire current limiter being connected to the second direct current bus while another end is connected to the lead-out wire; the lead-out wire current limiter comprises a first current-limiting unit, and the first current limiting unit comprises a group of direct current switches, as well as a first bypass switch and a first current-limiting resistor unit that are connected in parallel.

Abstract: A redundant energy acquisition circuit of a power module includes at least one power semiconductor device, a first capacitor, and a first bypass switch. The redundant energy acquisition circuit of the power module includes: a power supply board acquiring energy from the first capacitor, supplying power to a control board, and charging a discharge circuit. A first charging circuit has one end connected to a positive electrode of the first capacitor and another end connected to the discharge circuit, and charges the discharge circuit when the power supply board is not operating normally. The control board controls the discharge circuit to close. The discharge circuit discharges and triggers the first bypass switch to close after the discharge circuit is closed.

Abstract: A bipolar bidirectional DC converter comprises at least two valve group series (101, 102) and at least six magnetic elements (103), and said valve group series are divided into a Type-I valve group series (102) and a Type-II valve group series (101) each valve group series (101, 102) comprises a high-voltage DC port, a low-voltage DC port and at least three AC ports, and each AC port is connected to a magnetic element (103); and the other ends of the magnetic elements (103), which are connected to all the AC ports in the same valve group series (101, 102), are connected.

Abstract: A multi-voltage level direct current grid system and a control protection method, the direct current grid system comprising: at least two direct current buses; at least one direct current transformer, one end of which is connected to a first direct current bus while another end is connected to a second direct current bus or a lead-out wire, which may achieve direct current voltage conversion; and at least one lead-out wire current limiter, one end of the lead-out wire current limiter being connected to the second direct current bus while another end is connected to the lead-out wire; the lead-out wire current limiter comprises a first current-limiting unit, and the first current limiting unit comprises a group of direct current switches, as well as a first bypass switch and a first current-limiting resistor unit that are connected in parallel.

Abstract: A bipolar bidirectional DC converter comprises at least two valve group series (101, 102) and at least six magnetic elements (103), and said valve group series are divided into a Type-I valve group series (102) and a Type-II valve group series (101) each valve group series (101, 102) comprises a high-voltage DC port, a low-voltage DC port and at least three AC ports, and each AC port is connected to a magnetic element (103); and the other ends of the magnetic elements (103), which are connected to all the AC ports in the same valve group series (101, 102), are connected.

Abstract: A unidirectional DC voltage conversion device comprises a front end circuit (2), a main power circuit (1), a preceding-stage auxiliary isolation switch (5), and a subsequent-stage auxiliary isolation switch (6). A preceding-stage port of the main power circuit (1) and a subsequent-stage port of the front end circuit (2) form a cascade connection. The preceding-stage auxiliary isolation switch (5) is connected to a negative terminal (8) of a preceding-stage port of the front end circuit (2), and forms, together with a positive terminal (7) of the preceding-stage port of the front end circuit (2), a first input port of the unidirectional DC voltage conversion device.

Abstract: A closing control method for a high-voltage DC circuit breaker. The method comprises: closing breaking units of the transfer branch (2) group by group, then closing the main branch (1), and finally open the transfer branch. During the process of closing the breaking units of the transfer branch group by group, determine whether there is a fault in the power transmission system after closing current breaking unit group. if there is no fault, proceed to close the next breaking unit group until all breaking unit groups are closed before proceeding to the next step; if there is a fault, all the breaking units that have been closed are opened and the closing operation is ended. The method can pre-charge the power transmission system during the closing process of the high-voltage DC circuit breaker, and lower the overvoltage and system oscillation caused by the closing operation.

Abstract: A redundant energy acquisition circuit of a power module includes at least one power semiconductor device, a first capacitor, and a first bypass switch. The redundant energy acquisition circuit of the power module includes: a power supply board acquiring energy from the first capacitor, supplying power to a control board, and charging a discharge circuit. A first charging circuit has one end connected to a positive electrode of the first capacitor and another end connected to the discharge circuit, and charges the discharge circuit when the power supply board is not operating normally. The control board controls the discharge circuit to close. The discharge circuit discharges and triggers the first bypass switch to close after the discharge circuit is closed.

Abstract: A chained multi-port grid-connected interface apparatus includes a commutation chain, at least one direct-current converter, and at least one direct-alternating converter. The commutation chain is formed by at least two sub-module units connected in series in the same direction, one end of the direct-current converter is connected to a direct-current end of the sub-module unit, and the other end is a direct-current interaction port of the chained multi-port grid-connected interface apparatus. A direct-current connection end of the direct-alternating converter is connected to the direct-current end of the sub-module unit, and an alternating-current connection end is an alternating-current interaction port of the chained multi-port grid-connected interface apparatus.

Abstract: A bridge-type circuit comprises a H-bridge switch module and a buffering and reclosing module. The H-bridge switch module comprises four power semiconductor switch devices. Every two of the four power semiconductor switch devices are connected in series in the same direction to form a bridge arm, and the two bridge arms are further connected in parallel. Middle points of the two bridge arms respectively serve as an input terminal and an output terminal. The buffering and reclosing module is connected in parallel with the two bridge arms of the full bridge module. Also provided are a direct current breaking device formed by connecting the above bridge-type circuits in cascade and a control method thereof. The direct current breaking device is provided with the buffering and reclosing module, such that line voltage fluctuation generated during a reclosing operation is small.

Abstract: A direct current switch-off device comprises an on-state current branch circuit and a current commutating and breaking unit which are connected in parallel. The on-state current branch circuit has a mechanical switch (S) and a current transfer module which are connected in series. The current commutating and breaking unit comprises a bridge-type branch circuit and a current-breaking branch circuit. The current-breaking branch circuit and two bridge arms of the bridge-type branch circuit are connected in parallel. The current-breaking branch circuit comprises a nonlinear resistor (RI) and a valve group consisting of fully-controlled devices connected in series. The nonlinear resistor (RI) and the valve group are connected in parallel. Two ends of each fully-controlled device in the valve group are connected in parallel with a buffering and reclosing circuit.

Abstract: A closing control method for a high-voltage DC circuit breaker. The method comprises: closing breaking units of the transfer branch (2) group by group, then closing the main branch (1), and finally open the transfer branch. During the process of closing the breaking units of the transfer branch group by group, determine whether there is a fault in the power transmission system after closing current breaking unit group. if there is no fault, proceed to close the next breaking unit group until all breaking unit groups are closed before proceeding to the next step; if there is a fault, all the breaking units that have been closed are opened and the closing operation is ended. The method can pre-charge the power transmission system during the closing process of the high-voltage DC circuit breaker, and lower the overvoltage and system oscillation caused by the closing operation.

Abstract: A locomotive regenerative electric energy feedback system with an ice melting function, comprising two regenerative electric energy feedback devices (1). A direct-current side positive electrode of the regenerative electric energy feedback device (1) is connected to a positive electrode bus of a subway traction network, wherein the positive electrode bus is connected to an uplink contact network and a downlink contact network respectively via a first switching switch (4) and a second switching switch (5). A direct-current side negative electrode of the regenerative electric energy feedback device (1) is connected to the downlink contact network or the uplink contact network via a third switching switch (2), and the direct-current side negative electrode is connected to a negative electrode bus of the subway traction network via a fourth switching switch (3). Further disclosed is a control method corresponding to the system.

Abstract: A bridge-type circuit comprises a H-bridge switch module and a buffering and reclosing module. The H-bridge switch module comprises four power semiconductor switch devices. Every two of the four power semiconductor switch devices are connected in series in the same direction to form a bridge arm, and the two bridge arms are further connected in parallel. Middle points of the two bridge arms respectively serve as an input terminal and an output terminal. The buffering and reclosing module is connected in parallel with the two bridge arms of the full bridge module. Also provided are a direct current breaking device formed by connecting the above bridge-type circuits in cascade and a control method thereof. The direct current breaking device is provided with the buffering and reclosing module, such that line voltage fluctuation generated during a reclosing operation is small.

Abstract: A locomotive regenerative electric energy feedback system with an ice melting function, comprising two regenerative electric energy feedback devices (1). A direct-current side positive electrode of the regenerative electric energy feedback device (1) is connected to a positive electrode bus of a subway traction network, wherein the positive electrode bus is connected to an uplink contact network and a downlink contact network respectively via a first switching switch (4) and a second switching switch (5). A direct-current side negative electrode of the regenerative electric energy feedback device (1) is connected to the downlink contact network or the uplink contact network via a third switching switch (2), and the direct-current side negative electrode is connected to a negative electrode bus of the subway traction network via a fourth switching switch (3). Further disclosed is a control method corresponding to the system.

Abstract: Disclosed are a modulation method of a modular multilevel converter and a fault isolation method of a submodule unit. The modulation method comprises a first mode and a second mode, and the first mode and the second mode operate cyclically. In the first mode, a first power semiconductor switch and a second power semiconductor switch are turned on alternately, while a third power semiconductor switch is turned off normally and a fourth power semiconductor switch is turned on normally. In the second mode, the third power semiconductor switch and the fourth power semiconductor switch are turned on alternately, while the first power semiconductor switch is turned on normally and the second power semiconductor switch is turned off normally.

Abstract: A direct current switch-off device comprises an on-state current branch circuit and a current commutating and breaking unit which are connected in parallel. The on-state current branch circuit has a mechanical switch (S) and a current transfer module which are connected in series. The current commutating and breaking unit comprises a bridge-type branch circuit and a current-breaking branch circuit. The current-breaking branch circuit and two bridge arms of the bridge-type branch circuit are connected in parallel. The current-breaking branch circuit comprises a nonlinear resistor (RI) and a valve group consisting of fully-controlled devices connected in series. The nonlinear resistor (RI) and the valve group are connected in parallel. Two ends of each fully-controlled device in the valve group are connected in parallel with a buffering and reclosing circuit.

Abstract: Disclosed are a fault current-suppressing damper topology circuit and a control method thereof and a converter. An anode of a separate diode is connected to a positive electrode of a second switch module, a cathode of the separate diode is connected to one end of an energy storage capacitor, and the other end of the energy storage capacitor is connected to a negative electrode of a first switch module; a damping resistor is connected in parallel with an arrester and then with the first switch module; a bypass switch is connected in parallel between a terminal x1 and a terminal x2 of the damper topology circuit; a power supply system acquires energy from the energy storage capacitor and supplies power to a control system; and the control system controls an operating state of the damper topology circuit by controlling the bypass switch, the first switch module and the second switch module. The fault current-suppressing damper topology circuit is applied to voltage source converters.

Abstract: Disclosed are a modulation method of a modular multilevel converter and a fault isolation method of a submodule unit. The modulation method comprises a first mode and a second mode, and the first mode and the second mode operate cyclically. In the first mode, a first power semiconductor switch and a second power semiconductor switch are turned on alternately, while a third power semiconductor switch is turned off normally and a fourth power semiconductor switch is turned on normally. In the second mode, the third power semiconductor switch and the fourth power semiconductor switch are turned on alternately, while the first power semiconductor switch is turned on normally and the second power semiconductor switch is turned off normally.

Abstract: Disclosed are a fault current-suppressing damper topology circuit and a control method thereof and a converter. An anode of a separate diode is connected to a positive electrode of a second switch module, a cathode of the separate diode is connected to one end of an energy storage capacitor, and the other end of the energy storage capacitor is connected to a negative electrode of a first switch module; a damping resistor is connected in parallel with an arrester and then with the first switch module; a bypass switch is connected in parallel between a terminal x1 and a terminal x2 of the damper topology circuit; a power supply system acquires energy from the energy storage capacitor and supplies power to a control system; and the control system controls an operating state of the damper topology circuit by controlling the bypass switch, the first switch module and the second switch module. The fault current-suppressing damper topology circuit is applied to voltage source converters.