Abstract: Disclosed is a DC circuit breaker capable of interrupting fault currents flowing in both forward and backward directions. The DC circuit breaker includes: a mechanical switch installed on a DC transmission line and being opened to interrupt a current in the DC transmission line when a fault occurs at one side or remaining side thereof on the DC transmission line; a first bidirectional switching device connected in parallel with the mechanical switch and switching currents flowing in both forward and backward directions; an LC circuit connected in parallel with the mechanical switch and including a capacitor and a reactor connected in series to induce LC resonance; a first unidirectional switching device connected in parallel with the LC circuit and switching a current to induce LC resonance; and a second bidirectional switching device connected in series with the LC circuit and switching currents flowing in both forward and backward directions.

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 is a DC circuit breaker capable of interrupting fault currents flowing in both forward and backward directions. The DC circuit breaker includes: a first mechanical switch for interrupting a current in a DC transmission line; a first diode connected in parallel with the first mechanical switch; a second mechanical switch, connected in series with the first mechanical switch, for interrupting a current in the DC transmission line; a second diode connected in parallel with the second mechanical switch; an LC circuit connected in parallel with the first and second mechanical switches and including a capacitor and a reactor connected in series to induce LC resonance; a first unidirectional switching device connected in parallel with the LC circuit and switching a current to induce LC resonance; and a bidirectional switching device connected in series with the LC circuit and switching currents flowing in both forward and backward directions.

Abstract: A large capacity battery system for managing a large capacity battery used for power system frequency regulation and a large capacity battery operation method are provided. The method may include the steps of: calculating an estimated frequency regulation signal for the next day using history information of past frequency regulation signals; calculating a bidding capacity and a basic value for the large capacity battery, matched to the estimated frequency regulation signal; and determining an operation plan using the calculated bidding capacity and basic value; bidding the bidding capacity and basic value for the large capacity battery according to the operation plan on the day-ahead frequency regulation market.

Abstract: Provided is a high voltage DC circuit breaker that interrupts a fault current flowing through a high voltage DC transmission line with a vacuum circuit breaker and a gas circuit breaker connected in series. The circuit breaker includes: a vacuum circuit breaker installed on a DC transmission line and operating to interrupt a current in the DC transmission line when a fault occurs on either side of the DC transmission line; a gas circuit breaker connected in series with the vacuum interrupter; an LC circuit connected in parallel with the vacuum circuit breaker and including a capacitor and a reactor connected in series to induce LC resonance; a first bidirectional switching device connected in series with the LC circuit and switching a current flowing in any of two opposite directions; and a second bidirectional switching device connected in parallel with the LC circuit.

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: Disclosed is a fast switch device including: a reactor that moves to an open position where the switch is opened and a close position where the switch is closed; an open coil portion that drives the reactor to the open position by virtue of an eddy current component; a close coil portion that drives the reactor the close position by virtue of an eddy current component; and a controller that performs control such that an electric current is applied to the close coil portion oppositely to a direction of an electric current flowing through the open coil portion in order to brake the reactor during an open operation for driving the reactor to the open position, and an electric current is applied to the open coil portion oppositely to a direction of an electric current flowing through the close coil portion.

Abstract: The present invention relates to a power supply apparatus and, more particularly, to a power supply apparatus for sub-modules of a MMC (Modular Multilevel Converter), the apparatus stably supplying power to the sub-modules of the MMC connected to an HVDC (High Voltage Direct Current) system.

Abstract: The present invention relates to a vacuum interrupter for a circuit breaker capable of forming and releasing a short circuit by moving two movable electrodes in forward/backward directions, and a driving method therefor. The vacuum interrupter according to the present invention includes: a housing with a vacuum state therein; and first and second movable electrodes partially accommodated within the housing, and attached to first and second movable contacts at respective ends thereof, wherein the first and second movable electrodes are capable of moving in forward/backward directions, and the first and second movable contacts contact each other and separate from each other by the movement in forward/backward directions of the first and second electrodes.

Abstract: Disclosed is a capacitor bushing and a method of manufacturing the same. The capacitor bushing includes insulating layers (20), formed by winding insulating fibers (22) around the outer side of a central conductor (10), and conductive layers (30) between the insulating layers (20). The wefts (34) and warps (36) that constitute the conductive fibers (32) are manufactured by sequentially forming a first coating layer (38) and a second coating layer (38?) on the surface of a core wire (37). The wefts (24 and 34) and the warps (26 and 36) of the insulating fibers (22) and the conductive fibers (32) extend obliquely with respect to the longitudinal direction of the central conductor (10). The wefts (24 and 34) and the warps (26 and 36) form a polygonal or circular shape. The present invention has a merit in that bubbles are prevented from being generated in the filling layers (40).

Abstract: Disclosed is an method and apparatus for electric power distribution in an energy storage system. The electric power distribution method of the energy storage system (ESS) includes computing a total power amount on the basis of a received user output target power amount and a deviation amount, determining a power distribution power conditioning system (PCS) to which the total power amount is distributed out of the PCSs included in the ESS, and distributing the total power amount on the basis of the power distribution PCS. The deviation amount is a difference between an existing user output target power amount used in an existing power distribution process and an existing total power amount.

Abstract: The present invention relates to a state of charge (SOC) management system of an energy storage device, the system comprising at least one energy storage device, wherein the SOC management system of the energy storage device manages SOC of the energy storage device by performing P-f (active power-frequency) droop control on the basis of a droop coefficient, a reference frequency, and a dead band, which determine the output of each energy storage device.

Abstract: 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.

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: Provided is a circuit breaker for a DC current using a magnetic field, which generates a magnetic flux and extinguishes an arc current generated in a main switch. The circuit breaker includes a main switch installed in a DC line, a coil wound so as to generate a magnetic flux in a direction vertical to the direction of an arc current generated when the main switch is opened, a semiconductor switch for switching current application to the coil, a capacitor connected in series to the semiconductor switch, and a first diode for conducting the electric current of the DC line, supplied from one side of the main switch, to the capacitor, wherein the semiconductor switch is turned on, in case a fault occurs, so that the electric current is applied to the coil by the voltage charged in the capacitor.

Abstract: The present invention relates to a power management system (PMS) for multiple energy storage systems (ESS) that is for integrated management of the system having multiple ESS for controlling a frequency and having a hierarchical control structure. The PMS for ESS comprises: a plurality of ESS; a local management system (LMS) for managing one or more ESS of the plurality of ESS for each local unit; an ESS Controller (ESSC) for general management of the LMS, judging a state of the LMS and determining an output value of one or more ESS in the LMS, and transmitting the determined output value to the respective ESS; and a PMS for general management of the entire system comprising the plurality of ESS, the LMS and the ESSC, judging the state of the entire system and participating in a power grid frequency control market through a grid operator contract, controlling the output of the LMS, and adjusting a control parameter for output control.

Abstract: An electromagnetic repulsion actuator for a circuit breaker is provided. The actuator can include a housing; a first fixed electrode having therein an operating space open at both sides; a pair of movable electrodes capable of reciprocally moving and being electrically connected to the first fixed electrode; second fixed electrodes selectively contacting the pair of movable electrodes to be electrically connected thereto, thereby transferring power supplied from a first side to a second side; and actuating coils selectively moving the movable electrodes in a direction of being separated from the second fixed electrodes by generating electromagnetic force from induced current. In the present invention as above, the structure of a circuit breaker is simplified and moving speeds of the movable electrodes are increased since the movable electrodes move by using induced current generated by a close coil and open coils to perform an open operation.

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 high-voltage direct current (DC) circuit breaker for cutting off a fault current from flowing through a line during a malfunction in a high-voltage DC line. A DC circuit breaker according to the present invention comprises: a mechanical switch disposed on a DC line; an L/C circuit connected in parallel with the mechanical switch (110), and comprising a capacitor and a reactor connected in series to each other to generate LC resonance; a first semiconductor switch, connected in parallel to the L/C circuit, for switching the unidirectional flow of the current; and a second semiconductor switch, connected in parallel to the first semiconductor switch, for switching the uni- and reverse-directional flow of current.

Abstract: Provided is a high-voltage direct current (DC) circuit breaker which interrupts a fault current flowing in a power transmission or power distribution DC line when a fault occurs in the DC line. The high-voltage DC circuit breaker includes: a main switch, installed in the DC line, for interrupting a current in the DC line by being opened when a fault occurs in one side or the other side of the DC line; a nonlinear resistor, connected in parallel to the main switch, for consuming overvoltage; and an LC circuit connected in parallel to the main switch and comprising a capacitor and an inductor that are connected to each other in series to generate LC resonance.