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.

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.

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.

An electrical assembly including a voltage sourced converter for connection to an AC network, a controller programmed so that, responsive to detection of a fault in the AC network, the controller obtains a first set of voltage and current measurements taken at an interface connection point, change operation of the voltage sourced converter to inject a modified fault current, and then obtain a second set of voltage and current measurements, determine operating parameters of the voltage sourced converter for injecting a target fault current having a target phase angle that is substantially the same as a phase angle of a reference fault current that would have resulted from operation of the voltage sourced converter in accordance with pre-fault steady-state voltage phase and magnitude values, and operate the voltage sourced converter in accordance with the determined operating parameters so as to inject the target fault current at the target phase angle.

An electrical assembly including a voltage sourced converter for connection to an AC network, a controller programmed so that, responsive to detection of a fault in the AC network, the controller obtains a first set of voltage and current measurements taken at an interface connection point, change operation of the voltage sourced converter to inject a modified fault current, and then obtain a second set of voltage and current measurements, determine operating parameters of the voltage sourced converter for injecting a target fault current having a target phase angle that is substantially the same as a phase angle of a reference fault current that would have resulted from operation of the voltage sourced converter in accordance with pre-fault steady-state voltage phase and magnitude values, and operate the voltage sourced converter in accordance with the determined operating parameters so as to inject the target fault current at the target phase angle.

An insulation design apparatus performing the insulation design of a high voltage direct current (HVDC) transmission system is provided. The insulation design apparatus includes a first insulation model generation unit; a second insulation model generation unit; an insulation verification unit, wherein the second insulation model generation unit selects the positions of each facility, device and arrester of the HVDC transmission system through a system single line diagram to select a representative facility in the HVDC transmission system, divides the HVDC transmission system into the plurality of regions based on the selected representative facility, and generates an insulation model for each region.

Provided is a power supply apparatus for sub-modules of a Modular Multilevel Converter (MMC) which stably supplies power to the sub-modules of the MMC in connection with an HVDC system. The power supply apparatus for sub-modules of an MMC can include a charging unit in which an input voltage between P and N busses of the MMC is stored, a relay unit connected in parallel with the charging unit, a resistor connected in series with the relay unit, a TVS diode connected in series with the resistor, a Zener diode connected in series with the TVS diode, a transformer for delivering the input voltage (in a primary winding) to a secondary winding thereof, and a switch for switching the flow of current supplied to the transformer.

Provided is a power supply apparatus for sub-modules of a Modular Multilevel Converter (MMC) which stably supplies power to the sub-modules of the MMC in connection with an HVDC system. The power supply apparatus for sub-modules of an MMC can include a charging unit in which an input voltage between P and N busses of the MMC is stored, a relay unit connected in parallel with the charging unit, a resistor connected in series with the relay unit, a TVS diode connected in series with the resistor, a Zener diode connected in series with the TVS diode, a transformer for delivering the input voltage (in a primary winding) to a secondary winding thereof, and a switch for switching the flow of current supplied to the transformer.

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 (N2, 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 (1n<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.

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 (N2, 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 (1n<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.