Abstract: The present invention provides a method of MMC for HVDC. According to the present invention, there is provided a redundancy control method of an MMC for HVDC, wherein the MMC includes multiple converter arms each has multiple submodules in operation and redundancy modules for spares, the method including: checking whether a breakdown of a submodule in operation of a first converter arm among the multiple converter arms occurs in a case where the all redundancy modules of the first converter arm are applied in operation; and lowering an output voltage of each submodule of other converter arms in such a manner that a DC link voltage of each of the other converter arms is controlled to be equal to a DC link voltage of the first converter arm when the breakdown of the submodule of the first converter arm occurs.

Abstract: A Modular Multilevel Converter (MMC) includes multiple sub-modules connected in series with each other and a controller for controlling on/off switching of the sub-modules, in which the multiple sub-modules include N sub-modules that participate in the operation of the MMC and M redundant sub-modules for replacing at least one N sub-modules when the at least one N sub-modules fail, and the controller switches on a sub-module if a carrier signal assigned thereto is higher than a preset reference signal, and switches off the sub-module if the carrier signal assigned thereto is lower than the preset reference signal.

Abstract: Provided is a power control apparatus for sub-modules in an MMC, which controls stable supply of power to sub-modules in MMC connected to an HVDC system and a STATCOM. The power control apparatus has at least one first resistor connected between P and N buses of MMC; a second resistor connected in series with the first resistor; a switch connected in series with the second resistor; a third resistor connected in parallel with the second resistor and the switch which are connected in series; a Zener diode connected in parallel with the third resistor; and a DC/DC converter connected between both ends of the Zener diode and configured to convert voltage across both ends of the Zener diode into low voltage, and supply the low voltage to the sub-modules, wherein a magnitude of current flowing through the Zener diode is controlled depending on ON/OFF switching of the switch.

Abstract: The present invention relates to a modular cooling apparatus for a high-voltage direct-current transmission system. A sub-module (10) according to the present invention comprises a power unit (12) in the front and a capacitor unit (13) in the rear, and a heat sink (30) for discharging heat generated from the interior is provided in an interior space (14?) of a power unit housing (14) forming the exterior of the power unit (12). A coolant path (31) is provided in the interior of the heat sink (30). The entrance and exit of the coolant path (31) are located adjacent to the bottom surface of the interior space (14?). Connecting couplers (20) for supplying coolant to the interior space (14?) are provided on the sloped surface (16) on the bottom end of the front surface (15) of the power unit housing (14). The sloped surface (16) is formed so as to face the ground at an angle.

Abstract: The present invention provides a method of MMC for HVDC. According to the present invention, there is provided a redundancy control method of an MMC for HVDC, wherein the MMC includes multiple converter arms each has multiple submodules in operation and redundancy modules for spares, the method including: checking whether a breakdown of a submodule in operation of a first converter arm among the multiple converter arms occurs in a case where the all redundancy modules of the first converter arm are applied in operation; and lowering an output voltage of each submodule of other converter arms in such a manner that a DC link voltage of each of the other converter arms is controlled to be equal to a DC link voltage of the first converter arm when the breakdown of the submodule of the first converter arm occurs.

Abstract: Disclosed herein is a power supply apparatus for a sub-module controller of a Modular Multilevel Converter (MMC), which supplies driving power to the sub-module controller of an MMC connected to a High Voltage Direct Current (HVDC) system. The power supply apparatus includes a bridge circuit unit including N (N?2, integer) energy storage units for storing a DC voltage in series-connected sub-modules in the MMC and multiple power semiconductor devices connected in parallel with the N energy storage units in a form of a bridge; and a DC/DC converter for converting a voltage output from output terminals formed between both ends of n (1?n<N) series-connected energy storage units, among the N energy storage units, into a low voltage and supplying the low voltage to the sub-module controller.

Abstract: A shorting device for facilitating the grounding of a converter to which a plurality of sub modules is connected in series. The device includes: a moving rod (40) provided on a main frame (10) on which sub modules (S) are provided, and moving in the direction traversing the sub modules (S); and contactors (50) provided at the moving rod (40) to be electrically connected to each sub module outer casing (1) according to the movement of the moving rod (40). In addition, a connection means (C) electrically connects the contactor (50), the sub module outer casing (1), and another adjacent sub module outer casing (1) to enable simultaneous grounding thereof. This invention connects the sub module outer casings (1), which form the converter, through the operation of the shorting device to ground the sub modules (S).

Abstract: The present invention relates to a modular apparatus for a high-voltage direct-current transmission system. A sub-module (10), which is a modular apparatus, comprises according to the present invention a power unit (12) in the front and a capacitor unit (13) in the rear, and on the lower end of a front surface (14?) of a power unit housing (14) forming the exterior of the power unit (12) is a sloped surface (15). The sloped surface (15) has a hexahederal shape created by removing the edge formed by the front surface (14?) and the bottom surface of the power unit housing (14) and faces the ground at an angle. A display unit (16) is provided on the sloped surface (15) so that the status of the sub-module (10) can be easily checked by a worker from the ground on which a structure stands.

Abstract: The present invention relates to a module extraction apparatus of a high voltage direct current system. In the present invention, a fixed base (30) is secured to a structure (82), and a sub-module (10) is mounted on a movable base (60) that slides on the fixed base (30), thereby enabling the sub-module (10) to be extracted from the structure (82). The sub-module (10) may be separated into a power unit (12) and a capacitor unit (24) which may be separately extracted from the structure (82). A connection support (84) is connected to the fixed base (30) and installed to protrude toward the outside of the structure (82), and the tip end of the connection support (84) extending toward the outside of the structure (82) is supported by a wire (86). As described above, the present invention has an advantage of more easily extracting the module, which is a heavy object, from the structure (82) to carry out the maintenance thereof.

Abstract: Provided is a module replacement device of a high voltage direct current transmission system. In the device, a replacement base is provided in a structure by using a support member such that a sub-module movably provided at a fixing base of the structure can be replaced by being withdrawn outside of the structure. Further, the replacement base can easily and firmly be provided in the structure such that the module can be replaced in an easy and safe manner.

Abstract: The present invention relates to a power control apparatus for sub-modules in a Modular Multilevel Converter (MMC), which controls the supply of power to sub-modules in an MMC connected to an HVDC system and to a STATCOM.

Abstract: The present invention provides a Modular Multilevel Converter (MMC) in which M redundant sub-modules are additionally arranged in addition to the N sub-modules that are needed for operation, and the N+M sub-modules are controlled so as to participate in switching in turn. The MMC according to an embodiment of the present invention includes multiple sub-modules connected in series with each other and a controller for controlling on/off switching of the sub-modules. Here, the multiple sub-modules include N sub-modules that participate in the operation of the MMC and M redundant sub-modules for replacing a failing sub-module when at least one of the N sub-modules fails, and the controller switches on the sub-module if the carrier signal assigned thereto is higher than a preset reference signal, and switches off the sub-module if the carrier signal assigned thereto is lower than the reference signal.

Abstract: Disclosed herein is a power control apparatus for sub-modules in an MMC, which controls stable supply of power to sub-modules in MMC connected to an HVDC system and a STATCOM. The power control apparatus includes at least one first resistor connected between P and N buses of MMC; a second resistor connected in series with the first resistor; a switch connected in series with the second resistor; a third resistor connected in parallel with the second resistor and the switch which are connected in series; a Zener diode connected in parallel with the third resistor; and a DC/DC converter connected between both ends of the Zener diode and configured to convert voltage across both ends of the Zener diode into low voltage, and supply the low voltage to the sub-modules, wherein a magnitude of current flowing through the Zener diode is controlled depending on ON/OFF switching of the switch.

Abstract: Disclosed herein is a power supply apparatus for a sub-module controller of a Modular Multilevel Converter (MMC), which supplies driving power to the sub-module controller of an MMC connected to a High Voltage Direct Current (HVDC) system. The power supply apparatus includes a bridge circuit unit including N (N?2, integer) energy storage units for storing a DC voltage in series-connected sub-modules in the MMC and multiple power semiconductor devices connected in parallel with the N energy storage units in a form of a bridge; and a DC/DC converter for converting a voltage output from output terminals formed between both ends of n (1?n<N) series-connected energy storage units, among the N energy storage units, into a low voltage and supplying the low voltage to the sub-module controller.

Abstract: The present invention relates to a power control apparatus for sub-modules in a Modular Multilevel Converter (MMC), which controls the supply of power to sub-modules in an MMC connected to an HVDC system and to a STATCOM.

Abstract: A power supply device for HVDC controller is provided. The power supply device comprises: a first High Voltage Direct Current (HVDC) converter unit connected to an active power grid; a second HVDC converter unit connected to a passive power grid, the second HVDC converter unit being capable of receiving first DC power from the first HVDC converter unit by being connected to the first HVDC converter unit via a Direct Current (DC) transmission line; and an HVDC controller, arranged in the second HVDC converter unit, for receiving the first DC power, applied from the first HVDC converter unit to the second HVDC converter unit, by being connected to the DC transmission line that connects the first HVDC converter unit with the second HVDC converter unit.

Abstract: The present invention relates to a module replacement device of a high voltage direct current transmission system. In the present invention, a replacement base (40) is provided in a structure (1) by using a support member (70) such that a sub-module (30) movably provided at a fixing base (10) of the structure (1) can be replaced by being withdrawn outside of the structure (1). A rear end of a base plate (42) of the replacement base (40) is hooked to an insulation support part (9) of the structure (1), and a front end of the replacement base (40) is supported by the support member (70) hooked to one side of the structure (1). The support member (70) is provided with a turn buckle (74) so as to adjust the replacement base (40) such that the replacement base is horizontally provided thereto.

Abstract: The present invention consists of: a first HVDC converter unit which is connected to a powered electrical grid; a second HVDC converter unit which is connected to a powerless electrical grid and connected to the first HVDC converter unit through a DC transmission line so as to receive a first DC power source from the first HVDC converter unit; a voltage distributor which is connected to the DC transmission line connecting the first HVDC converter unit and the second HVDC converter unit so as to receive and distribute the first DC power source applied from the first HVDC converter unit to the second HVDC converter unit, and output a second DC power source that is lower than the first DC power source; and a DC-DC converter which is connected to the voltage distributor so as to receive the second DC power source, convert the second DC power source into actuating power for use in a HVDC controller and output the actuating power.

Abstract: The present invention relates to a modular cooling apparatus for a high-voltage direct-current transmission system. A sub-module (10) according to the present invention comprises a power unit (12) in the front and a capacitor unit (13) in the rear, and a heat sink (30) for discharging heat generated from the interior is provided in an interior space (14?) of a power unit housing (14) forming the exterior of the power unit (12). A coolant path (31) is provided in the interior of the heat sink (30). The entrance and exit of the coolant path (31) are located adjacent to the bottom surface of the interior space (14?). Connecting couplers (20) for supplying coolant to the interior space (14?) are provided on the sloped surface (16) on the bottom end of the front surface (15) of the power unit housing (14). The sloped surface (16) is formed so as to face the ground at an angle.

Abstract: The present invention relates to a module extraction apparatus of a high voltage direct current system. In the present invention, a fixed base (30) is secured to a structure (82), and a sub-module (10) is mounted on a movable base (60) that slides on the fixed base (30), thereby enabling the sub-module (10) to be extracted from the structure (82). The sub-module (10) may be separated into a power unit (12) and a capacitor unit (24) which may be separately extracted from the structure (82). A connection support (84) is connected to the fixed base (30) and installed to protrude toward the outside of the structure (82), and the tip end of the connection support (84) extending toward the outside of the structure (82) is supported by a wire (86). As described above, the present invention has an advantage of more easily extracting the module, which is a heavy object, from the structure (82) to carry out the maintenance thereof.