Abstract: A reactive power compensator includes a plurality of phase clusters each including plurality of cells and a controller configured to control the plurality of phase clusters. The controller performs control to generate an offset signal through phasor transformation based on respective voltage values and current values of the plurality of phase clusters and to compensate for energy errors between the plurality of phase clusters based on the generated offset signal.

Abstract: A reactive power compensator includes a plurality of phase clusters each including a plurality of cells, and a controller configured to control the plurality of phase clusters. When an energy error is generated in each of the plurality of phase clusters, the controller performs control to compensate for the energy error by generating an offset signal having a zero sequence component based on an error energy value of each of the plurality of phase clusters.

Abstract: A reactive power compensator includes a plurality of phase clusters each including plurality of cells and a controller configured to control the plurality of phase clusters. The controller performs control to generate an offset signal through phasor transformation based on respective voltage values and current values of the plurality of phase clusters and to compensate for energy errors between the plurality of phase clusters based on the generated offset signal.

Abstract: A control device for a voltage source converter connected to a wind farm is provided. The control device includes: a power source monitor unit sensing a direct current (DC) voltage of a whole grid connected to the voltage source converter; and a control unit comparing the DC voltage of the whole grid sensed with a reference voltage, wherein the control unit adjusts an alternating current (AC) supplying to the wind farm to a setting when as a result of comparison, the DC voltage of the whole grid sensed is out of a preset range of reference voltages.

Abstract: A reactive power compensator includes a plurality of phase clusters each including a plurality of cells, and a controller configured to control the plurality of phase clusters. When an energy error is generated in each of the plurality of phase clusters, the controller performs control to compensate for the energy error by generating an offset signal having a zero sequence component based on an error energy value of each of the plurality of phase clusters.

Abstract: A reactive power compensation apparatus includes one or more phase clusters each comprising a plurality of cells, and a controller controlling the one or more phase clusters. When at least one cell in a specific phase cluster among the one or more phase clusters is faulty, the controller controls a voltage of each cell in each of the remaining phase clusters except for the specific phase cluster to be controlled, using a modulation index.

Abstract: A reactive power compensation apparatus includes one or more phase clusters each comprising a plurality of cells, and a controller controlling the one or more phase clusters. When at least one cell in a specific phase cluster among the one or more phase clusters is faulty, the controller controls a voltage of each cell in each of the remaining phase clusters except for the specific phase cluster to be controlled, using a modulation index.

Abstract: The present disclosure relates a modular multi-level converter (MMC) including two arms including different types of sub modules according to the respective arms, two sub controllers corresponding to the two arms, respectively and configured to separately control the two arms, respectively, and a central controller configured to determine a switching operation condition of the sub module and to output a switching signal corresponding to the switching operation condition to each of the two sub controllers, wherein the two sub controllers control the respective corresponding arms based on the switching signal and, upon receiving a voltage change switching signal for controlling a voltage applied to one of the two arms, change the voltage applied to one of the two arms based on the voltage change switching signal.

Abstract: A method of controlling voltage balancing of a modular multi-level converter is provided. The method includes receiving state information on each of n sub modules in an arm module, grouping the n sub modules into m sub module groups, receiving first state information on each of sub modules in a first one of the m sub module groups, among the state information on each of the n sum modules, receiving second state information on each of sub modules not included in the first sub module group, among state information on each of the n sum modules previously stored in a memory, controlling switching of a sub module by using the first state information and the second state information, and updating the memory with the first state information.

Abstract: A converter and an operation method thereof are provided. A converter interconnected with a wind power generation farm includes a power monitor unit configured to detect a direct-current voltage of an entire system interconnected with the converter, a control unit configured to compare the detected direct-current voltage of the entire system with a reference voltage and adjust an alternating-current voltage that is supplied to the wind power generation farm to a preset value, and a switching unit configured to perform a switching operation based on the adjusted preset value to convert alternating-current power into direct-current power.

Abstract: A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; DC transmission lines W1 and W2 transmitting the DC power obtained from the rectifier through conversion to the inverter; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit controlling the operations of the rectifier and the inverter based on the first active power measured and the second active power measured, wherein the first control unit senses oscillation generated in the HVDC transmission system and generates a control signal for damping the sensed oscillation to control one or more of the rectifier and the inverter.

Abstract: A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes: a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; a DC transmission line transmitting, to the inverter, the DC power obtained through conversion by the rectifier; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit detecting an abnormal voltage state on the DC transmission line based on the first and second active power measured.

Abstract: A method of controlling voltage balancing of a modular multi-level converter is provided. The method includes receiving state information on each of n sub modules in an arm module, grouping the n sub modules into m sub module groups, receiving first state information on each of sub modules in a first one of the m sub module groups, among the state information on each of the n sum modules, receiving second state information on each of sub modules not included in the first sub module group, among state information on each of the n sum modules previously stored in a memory, controlling switching of a sub module by using the first state information and the second state information, and updating the memory with the first state information.

Abstract: The present disclosure provides a method for controlling a multilevel converter, the method including, detecting modulation state values and current directions of sub-modules, and designating, by one sub-module, an average number of switching for each period of an output waveform, wherein the step of designating the average number of switching includes, grouping the sub-modules according to being in ON state or in OFF state, comparing the number of sub-modules in previous ON state and the number of sub-modules in OFF state to obtain a difference therebetween, and changing a state as much as the difference, comparing a sub-module of ON state in charged state and in discharged state with a sub-module of OFF state, and changing the compared states of sub-modules of ON state and OFF state.

Abstract: A converter and an operation method thereof are provided. A converter interconnected with a wind power generation farm includes a power monitor unit configured to detect a direct-current voltage of an entire system interconnected with the converter, a control unit configured to compare the detected direct-current voltage of the entire system with a reference voltage and adjust an alternating-current voltage that is supplied to the wind power generation farm to a preset value, and a switching unit configured to perform a switching operation based on the adjusted preset value to convert alternating-current power into direct-current power.

Abstract: A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; DC transmission lines W1 and W2 transmitting the DC power obtained from the rectifier through conversion to the inverter; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit controlling the operations of the rectifier and the inverter based on the first active power measured and the second active power measured, wherein the first control unit senses oscillation generated in the HVDC transmission system and generates a control signal for damping the sensed oscillation to control one or more of the rectifier and the inverter.

Abstract: Provided is a high voltage direct current transmission system including a power transmission part converting AC power into DC power; a power receiving part converting DC power into AC power; and a DC power transmission part transferring the DC power converted in the power transmission part to the power receiving part, wherein one of the power transmission part and the power receiving part includes a measuring part measuring an AC voltage; an AC voltage control unit generating a first reactive power control signal based on the measured AC voltage and a reference AC voltage; a reactive power control unit generating a second reactive power control signal based on the first reactive power control signal and a reference reactive power signal; and a power control unit controlling reactive power of the power transmission part or the power receiving part based on the second reactive power control signal.

Abstract: A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes: a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; a DC transmission line transmitting, to the inverter, the DC power obtained through conversion by the rectifier; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit detecting an abnormal voltage state on the DC transmission line based on the first and second active power measured.

Abstract: A control device for a voltage source converter connected to a wind farm is provided. The control device includes: a power source monitor unit sensing a direct current (DC) voltage of a whole grid connected to the voltage source converter; and a control unit comparing the DC voltage of the whole grid sensed with a reference voltage, wherein the control unit adjusts an alternating current (AC) supplying to the wind farm to a setting when as a result of comparison, the DC voltage of the whole grid sensed is out of a preset range of reference voltages.

Abstract: A method of controlling a multilevel converter is provided. In the method of controlling a multilevel converter according to an embodiment, a sub-module having the maximum voltage and a sub-module having the minimum voltage respectively are extracted from among a plurality of sub-modules. An amount of state variation of each of the plurality of sub-modules is determined. When the amount of state variation is not determined to be 0, a direction of a current flowing through the plurality of sub-modules is detected. A subsequent state of at least one sub-module is determined according to at least one of the amount of the state variation and current direction. Subsequently an arrangement time for sub-module values can be efficiently reduced while the number of the sub-modules increases in the voltage balancing.