44results about How to "Reduce fault current" patented technology

The invention discloses a bridge arm bypass protection circuit of a modularization multi-level converter aiming at a direct current short circuit fault, and belongs to a converter fault protection device range. The protection circuit is realized by arranging a bridge arm bypass, which is formed by serially connecting a bypass thyristor and a bypass resistor together, between the upper bridge arm and the lower bridge arm of every phase of the modularization multi-level converter. During common function, the bypass thyristor is in an off state, and the bridge arm bypass does not work. After the fault occurs, a sub-module IGBT is locked, and at the same time, the bypass thyristor is conducted, and because of the shunting function of the bridge arm bypass, fault current flowing through sub-module devices is reduced, and attenuation of direct current side current is also accelerated after trip-out of an alternating circuit breaker, and therefore fault recovery time is reduced, and a good fault protection function is provided for the devices and the alternating current system. For a system adopting the direct current circuit breaker, the protection circuit is used to reduce the fault current of the direct current side, and therefore a requirement on the switching-on / off of the current of the direct current circuit breaker is reduced, and economic performance and reliability are improved.

Provided are a multi-level converter having more than one converter arm in which a plurality of sub-modules are connected in series, multi-level converter comprising, a first bypass circuit connected in parallel to at least one sub-module included in more than one converter arm on a first side and including a first switching device, a second bypass circuit connected in parallel to more than one converter arm on a second side and including a diode, a second switching device included in more than one converter arm and having a first end connected in series to at least one sub-module and a second end connected to a first end of first bypass circuit at a single node and a third switching device included in more than one converter arm and having a first end connected in series to at least one sub-module and a second end connected to a first end of second bypass circuit at a single node.

The invention relates to a power electronic converter (20a) for use in high voltage direct current power transmission and reactive power compensation which comprises at least one converter limb (22) including first and second DC terminals (24a, 24b) for connection in use to a DC network (26), the or each converter limb (22) including at least one first converter block (32) and at least one second converter block (34) connected between the first and second DC terminals (24a, 24b); the or each first converter block (32) including a plurality of line-commutated thyristors (36) and at least one first AC terminal (28) for connection in use to an AC network (30), the or each second converter block (34) including at least one auxiliary converter including a plurality of self-commutated switching elements; wherein the self-commutated switching elements are controllable in use to inject a voltage to modify a DC voltage presented to the DC side of the converter limb (22) and / or modify an AC voltage and an AC current on the AC side of the power electronic converter (20a).

A permanent magnet (PM) machine includes a plurality of reconfigurable fault condition mechanisms disposed within a stator core portion, the plurality of reconfigurable fault condition mechanisms together automatically reconfigurable to reduce fault currents and internal heat associated with the PM machine during a fault condition. The plurality of reconfigurable fault condition mechanisms are disposed solely within the stator core portion according to one embodiment to automatically reduce stator winding fault currents and internal heat associated with the PM machine during a fault condition. A method of reconfiguring the fault condition mechanisms upon detecting a fault condition includes the steps of 1) selecting the plurality of reconfigurable fault condition mechanisms from a) a plurality of rotatable magnetically anisotropic cylinders disposed both within a stator back iron and stator slot openings, and b) a plurality of rotatable magnetically anisotropic cylinders disposed within a stator back iron and a sliding shield disposed with a stator slot opening portion of the stator core, and 2) reconfiguring the plurality of fault condition mechanisms together to automatically reduce fault currents associated with the PM machine upon detection of a fault condition.

The present invention relates to a reclosing control system and method using a superconducting fault current limiter. The reclosing control system includes a superconducting fault current limiting device in which two circuits, each having a switch and a superconducting fault current limiter connected in series with each other, are connected in parallel with each other. A recloser is disposed between the superconducting fault current limiting device and a distribution line and is configured to control reclosing. The distribution line is connected to the recloser and is configured to transfer power to a load.

The invention discloses a doubly-fed wind turbine generator set low-voltage rid through control method based on inductance simulation, and belongs to the technical field of wind power generation. When a fault occurs in a power grid, rotor side converter equivalent port impedance of the doubly-fed wind turbine generator set is simulated into a pure inductance form, an inductance value is dynamically adaptively adjusted in real time according to rotor voltage and current constraints, voltage and current margins of the rotor side converter can be made full use of, a rotor voltage requirement is lowered and rotor fault current are reduced, and a controllable low-voltage ride through capability of the doubly-fed wind turbine generator set is improved. The method provided by the invention can also effectively suppress electromagnetic torque pulsation, and has the advantages of being clear and definite in physical conception, and being simple in structure.

The invention provides a hybrid DC circuit breaker for reducing reclosing impact and a control method. The hybrid DC circuit breaker for reducing reclosing impact comprises a main through current branch, a main breaking branch and a reclosing damping branch, wherein the reclosing damping branch comprises multiple damping units, the multiple damping units are serially connected, each damping unit comprises a power electronic switch and a damping resistor, the power electronic switch and the damping resistor are in parallel connection, and the reclosing damping branch and the main breaking branch are serially connected and are then parallelly connected with the main through current branch for reducing secondary impact on the system in the case of reclosing at permanent fault. The circuit breaker of the invention can not only minimize the reclosing impact, but also accurately detect permanent fault with a high resistance property and realize flexible reclosing.

The invention provides an emergency power control method and system of an offshore wind power flexile and direct access system. The emergency power control method comprises the steps of receiving a control signal sent from a system dispatching center by a communication system built in advance; starting a corresponding emergency power control method according to the type of the control signal, wherein the emergency power control method can act on a land braking resistor and / or offshore wind power field AC system; and arranging the land braking resistor at a DC outlet of a land converter station. The characteristic that a flexible DC active power can be rapidly and independently adjusted is utilized, an emergency power control method is designed, the power injected to a main grid system canbe effectively adjusted, and the offshore wind power control flexibility is improved.

The invention relates to an alternating current side wiring structure of a direct current transmission system of a power supply converter and a control method of the alternating current side wiring structure. The wiring structure comprises an upper stage circuit breaker CB1, an access circuit breaker CB2, a transformer T, a start resistor R and an alternating current circuit breaker CB3, wherein an alternating current incoming line of a converter station is led to a power supply from the upper stage circuit breaker CB1, the upper stage circuit breaker CB1 is connected with the transformer T through the access circuit breaker CB2, the start resistor R and the alternating current circuit breaker CB3 constitute a parallel circuit, and the transformer T is connected with the converter C through the parallel circuit constituted by the start resistor R and the alternating current circuit breaker CB3. When the direct current side of the converter breaks down, control protection is performed to simultaneously send commands for skipping the alternating current incoming line circuit breaker and the circuit breaker connected with the start resistor in parallel. Under the condition that the alternating current incoming line circuit breaker fails, the start resistor is connected into the fault circuit, and thus a fault current flowing through the converter before the skipping of the upper stage circuit breaker is effectively reduced, safety of a converter valve is protected and design parameters of original components of equipment are reduced.

Provided are a multi-level converter having more than one converter arm in which a plurality of sub-modules are connected in series, multi-level converter comprising, a first bypass circuit connected in parallel to at least one sub-module included in more than one converter arm on a first side and including a first switching device, a second bypass circuit connected in parallel to more than one converter arm on a second side and including a diode, a second switching device included in more than one converter arm and having a first end connected in series to at least one sub-module and a second end connected to a first end of first bypass circuit at a single node and a third switching device included in more than one converter arm and having a first end connected in series to at least one sub-module and a second end connected to a first end of second bypass circuit at a single node.

The invention provides a fault direction judgment method suitable for a wind power access system and belongs to the technical field of power transmission line protection of the wind power access system. The technical problem is that the invention provides a non-earth-fault direction judgment method which is suitable for the wind power access system, and can effectively prevent direction misjudgement caused when a direction element is applied to the wind power side of a link line of the wind power access system. The technical scheme is characterized in that the method comprises the following steps: to begin with, collecting current and voltage at the protection installation place of the wind power side of the link line of the wind power access system; after obtaining the sampling value of a voltage fault component, obtaining positive-sequence component discrete values of the current, voltage and fault voltage; and finally, carrying out judgment on the fault according to the numerical values. The fault direction judgment method is suitable for an electric system.

The invention discloses a hybrid high-voltage direct-current circuit breaker based on a bidirectional current limiting module, which comprises a through-current branch and a fault removal branch connected in parallel, wherein the through-current branch comprises a mechanical switch and m bidirectional current limiting sub modules which are connected in series with each other; the fault removal branch comprises n bidirectional current limiting sub modules which are connected in series, and m is smaller than n; the bidirectional current limiting sub module comprises a first current limiting branch and a second current limiting branch; the first current limiting branch comprises a power electronic module M1, a current limiting inductor L1 and a power electronic module M3 which are sequentially connected in series; and the second current limiting branch comprises a power electronic module M4, a current limiting inductor L2 and a power electronic module M2 which are sequentially connected in series. The requirement for the over-current capability is low, reliable turn-off of the power device can be guaranteed, the number of the power devices connected in parallel can be correspondinglyreduced, and the cost is reduced; and the amplitude of the switched-off fault current is small, the technical requirement on the circuit breaker is lower, and meanwhile, the damage of the fault current to the power supply system is smaller.

The invention discloses an energy storage charging system, which comprises an AC / DC converter and a DC / DC converter, wherein the high-frequency isolation conversion AC / DC converter takes power from power grid to supply power to a load, and the high-frequency isolation conversion DC / DC converter discharges power from battery to supply power to the load. The energy storage charging system is chargedby converting the charging ACDC into direct current electric energy, and meanwhile, the high-frequency isolated DCDC conversion device can discharge electricity to the load power supply bus, and simultaneously, the ACDC connected with the alternating current converts the alternating current electric energy into direct current electric energy to the load power supply bus to supply power to the load. The charging ACDC is isolated through the high-frequency isolation transformer, and the electric energy passing through a transformer is adjusted, so that the charging voltage and current of the direct-current bus to an energy storage device are adjusted; and a power supply DCDC is isolated through the high-frequency isolation transformer, the electric energy passing through the transformer isadjusted, and the power supply voltage and current of the load power supply bus are adjusted, so that the purpose of charging an electric vehicle or other types of loads is achieved.

The embodiment of the invention provides a power generator relay protection method and a device which are used for a scene of parallel operation of a plurality of power generators in a data center. Aneutral point grounding manner of the power generators is small resistance single-point grounding. The method comprises the steps of acquiring neutral point side current of the power generators, and outgoing line side current of the power generator, and determining whether the power generators have faults in a protection scope according to the neutral point side current, the outgoing line side current and action current of a differential current relay. The neutral point side current is current transformed by current transformers on neutral point sides of the power generators, and the outgoingline side current is current transformed by current transformers on outgoing line sides of the power generators.

The invention provides a feeder automation protection terminal based on an embedded platform, and relates to the technical field of power supply network security and electrical equipment. A DSP chip TMS320F28335 is used as a core processor, and the S232 / RS485 communication is realized by two serial ports on a chip. Ethernet communication is carried out by expanding W5100, and remote control is realized by an I / O pin of the chip through optical isolation control; the remote measurement is realized by a 16-bit high-precision AD chip ADS8556 through bus expansion, and remote signaling is realizedby photoelectric isolation of a bus interface. The invention has the beneficial effects that 1, high-precision data acquisition and calculation of micro signals can be realized; 2, zero sequence power protection of the distribution network; 3, distribution network grounding composite current protection; and 4, an embedded hardware platform with ultra-low power consumption.

The invention discloses a power distribution network single-phase earth fault arc extinguishing method, device and equipment and a storage medium, and the method comprises the steps: determining a feeder line with a reduced phase voltage and an increased phase current from a power distribution network, and enabling the feeder line to serve as a fault feeder line with an earth fault; calculating the impedance value of a grounded impedance branch according to the load impedance of the fault feeder line, and setting an impedance branch; connecting the impedance branch to a bus where the fault feeder is located; detecting the zero-sequence current of the fault feeder line; and adjusting the impedance value of the impedance branch based on the zero-sequence current so as to reduce the zero-sequence current. The impedance value of the impedance branch is calculated by using the load impedance of the fault feeder line, so that the impedance branch can be matched with the fault feeder line, and when the impedance branch is connected to the bus where the fault feeder line is located, the fault current of the fault feeder line is eliminated to the maximum extent; and the impedance value of the impedance branch is adaptively adjusted according to the zero-sequence current of the fault feeder line, so that the fault current of the fault feeder line can be further reduced.

The invention discloses a high-frequency isolation conversion energy storage system, which comprises high-frequency isolation conversion two-way DC / DC conversion devices and a direct current bus, wherein a first connecting point of each two-way DC / DC device is connected with an energy storage device; a second connecting point is connected to the direct current bus; through the two-way DC / DC devices, electric energy in the energy storage devices can be subjected to two-way alternating with the direct current bus through high-frequency isolation conversion. A plurality of energy storage devicesare isolated from the high-frequency isolation transformers of the two-way conversion devices subjected to high-frequency isolation from the direct current bus; the electric energy passing through a transformer is limited, so that the fault current of the direct current bus is reduced; the goal of safe protection is achieved; the plurality of groups of energy storage devices are connected with thebus through respectively independent two-way isolation conversion devices; the differences among different energy storage devices cannot generate mutual influence; the energy storage devices with different properties can even be used in a combined way.

The invention discloses a bidirectional hybrid direct-current circuit breaker based on capacitor commutation, and a direct-current power transmission system. The direct-current circuit breaker comprises an ultra-fast mechanical switch unit, a load change-over switch unit, a capacitor current conversion unit and an energy absorption unit, wherein the ultra-fast mechanical switch unit is connected in series with the load change-over switch unit, the capacitor current conversion unit is connected in parallel with the ultra-fast mechanical switch unit and the load change-over switch unit which areconnected in series, the energy absorption unit is connected in parallel with the capacitor current conversion unit, the capacitor current conversion unit is used for providing a low-voltage branch for the ultra-fast mechanical switch unit and the load change-over switch unit to ensure normal switching-on and switching-off of the ultra-fast mechanical switch unit and the load change-over switch unit when a short-circuit fault occurs in the system, and cutting off fault current by utilizing a self-switching-off function, and the energy absorption unit is used for absorbing energy stored by aninductive element in a power system after the fault current is cut off after the on-off fault. The bidirectional hybrid direct-current circuit breaker based on capacitor commutation provided by the invention can realize on-off of fault current and energy absorption limitation of a lightning arrester.

The invention discloses a five-end high-voltage direct-current power transmission system. The system comprises five convertor stations, a transformer, a circuit breaker and a pentagonal direct-current grid. Fault current is reduced to the minimum when a ground fault happens through combined control of voltage between the convertor stations, and meanwhile, according to the power generation cost and load power required values of all power sources of a multi-end high-voltage direct-current power transmission system, the output power value of each power source is controlled, so that the power distribution reliability is improved and the power consumption cost is reduced.

The invention provides a bridge arm circuit and method inhibiting a fault current of a large-capacity MMC submodule, and mainly aims at inhibition of the fault current of the large-capacity MMC submodule. In a design scheme of bridge arms of a large-capacity MMC, each bridge arm (phase unit) in the converter is designed as an integral body, and reactors are arranged in DC and AC sides of each bridge arm respectively in a manner that bridge arm reactors are dispersed. The total inductance value of the reactors in each bridge arm is kept constant, and the weight coefficients of the reactance in the AC and DC sides in the reactance of the bridge arm are checked according to system parameters. Each arm is connected to the external via the reactors in the AC and DC wire outlets. The bridge arm design scheme of the invention can be used to reduce the peak value of the fault current of the submodule and inhibit the rise rate of the fault current effectively, and further improve utilization rate of power devices in equipment, the cost of primary equipment is not increased, and the economical performance is high.

The invention relates to a novel quick-response direct-current current limiter and a current limiting method. Through additionally arranging an auxiliary branch circuit to a right iron core column ofa traditional two-column saturated iron core type direct-current current limiter, the negative effect of prolonging the fault current drop time of an original current limiter when a direct-current circuit breaker fails and is broken is eliminated, the breaking process is accelerated, the energy absorption stress of the circuit breaker is reduced, the overvoltage stress is reduced, the response speed is accelerated, and the insulation cost is reduced.

The invention provides a grounding method of a neutral point of a medium-voltage system, which is used for a medium-voltage transformer of a small resistance grounding system and is mainly used for atransformer of a star-connection system. The method comprises the following steps: comprehensively counting the length and the laying mode of the high-voltage cables in the factory, classifying the laying modes into overhead laid cables and non-overhead laid cables; calculating a cable distributed capacitance current, selecting a transformer that can run with a small resistance, configuring zero-sequence current protection for the transformer with possible small resistance grounding, and installing a neutral point grounding knife switch which can be remotely controlled at a neutral point of astation power transformer, which can reduce the operation overvoltage level, the fault current, the fault point current and the influence on other cable equipment, so that the problem of voltage risecaused by operation overvoltage is solved, the problem of overlarge current caused by single-phase grounding is alleviated, the problem of poor selectivity of zero-sequence protection after the medium-voltage system is grounded is solved, and the insulation design of the equipment can be designed according to the original design level without large investment.

The invention discloses a method for enhancing the fault current resistance of a three-phase coaxial superconducting cable, and the method comprises: enabling a three-phase coaxial superconducting cable branch and a conventional wire branch to be connected to a bus in parallel, and enabling three phases of the conventional wire branch and three phases of the superconducting cable branch to be connected in parallel. By applying the method provided by the invention, when the superconducting cable branch breaks down, the short-circuit current exceeds the critical current of the superconducting cable, the superconducting cable is rapidly quenched, and the superconducting cable is in a high resistance state. At the moment, the impedance of the bypass conventional wire branch is smaller than theimpedance of the superconducting cable branch, thereby achieving a shunting effect, greatly reducing the fault current passing through the superconducting cable branch, improving the fault current tolerance level of a superconducting cable system, and protecting the safety of a superconducting power-on conductor. Compared with a conventional reactor connected in series, the system loss under thenormal operation condition is greatly reduced; and compared with the use of a superconducting current limiter, the cost is lower, and the coordination is simple.

The invention discloses a 66kV collection access-based flexible direct-current offshore converter station, a system and a control method, and the flexible direct-current offshore converter station is characterized in that the offshore converter station comprises a connection transformer, a flexible direct-current converter valve and a bridge arm reactor, wherein the primary side of the connection transformer is connected with a bus bar of an offshore wind plant; the primary side is connected with the input end of the flexible direct current converter valve, the output end of the flexible direct current converter valve is connected with the first end of the bridge arm reactor, and the second end of the reactor is connected with the direct current submarine cable. And the investment and maintenance cost of an offshore booster station is saved. By increasing control strategies, increasing module voltage, reducing the total number of converter valve modules, reducing capacitance value, improving transmission capacity of equipment and reducing size and weight of an offshore wind power plant, the problems of land occupation, large load, high cost and the like of an offshore converter station can be effectively solved, technical cost of engineering implementation is remarkably reduced, and the method is suitable for large-scale popularization and application. The method has better economical efficiency and is of great significance to large-scale development and utilization of offshore wind power.

The invention discloses a generator transformer bank grid-connected circuit breaker flashover protection method. Aiming at the problem of long action delay of the existing circuit breaker flashover protection method, the invention provides an instantaneous action flashover protection method, and the method adopts the action condition of the phase angle difference between the terminal voltage and the main transformer high-voltage side bus voltage as well as a phase current action element, so that the protection reliability can be ensured. The relay protection method provided by the invention is simple and reliable in principle and relatively high in feasibility, conforms to the basic'four-property 'principle of relay protection, namely, the reliability, sensitivity, selectivity and quick action principle, is extremely low in implementation cost, can greatly improve the rapidness and reliability of flashover protection of the grid-connected circuit breaker of the generator transformer bank, and has a relatively high application value.

The invention relates to a DC power grid topology based on a coupling transformer under high impedance grounding, and a fault positioning method thereof. The positioning method comprises the followingsteps: firstly detecting a DC voltage signal of a DC line through a way of detecting the voltage signal, initially judging whether the fault occurs; after judging that the fault occurs, controlling to short-circuit a high-impedance grounding line arranged between the neutral point of the coupling transformer and the ground, in this case, the fault current can produce in the DC line since the highimpedance arranged between the neutral point of the coupling transformer and the ground is short-circuited; and then detecting the fault positioning according to the fault current. Therefore. The fault positioning method is suitable for the DC power grid topology based on the coupling transformer high-impedance grounding, the fault positioning can be realized, and then the fault overhauling can be performed according to the fault location, and a fault positioning demand of the DC power grid topology based on coupling transformer high impedance grounding can be satisfied; furthermore, the fault positioning method is simple and practical, easy for engineering field implementation, and capable of improving the reliability of the DC power grid.