26 results about "Dc fault" patented technology

The application discloses a method for controlling hybrid MMC sub-modules to clear DC short-circuit fault current. The method detects the real-time size of AC voltage, calculates the bridge arm voltage according to the principle of limiting AC current change and not affecting the speed of DC fault current clearing, and determines the number of improved sub-modules (sub-modules capable of providing counter electromotive force, such as full-bridge sub-modules) in each bridge arm according to the bridge arm voltage. Compared with the conventional method of directly locking all sub-modules to clear DC fault current, the application reduces the bridge arm current during the DC fault current clearing process, alleviates the overvoltage of the improved sub-modules, limits the influence on the speed of DC fault clearing, and improves the safety of the hybrid modular multilevel converter during the process of clearing DC fault current.

The present application relates to the technical field of power system stability control, and is a steady-state voltage control method and system for reducing transient voltage instability risk of a new energy collection station, the method comprising: establishing a new energy collection station bus transient voltage model of a new energy sending end power grid after a DC bipolar blocking fault; setting a new energy collection station transient voltage instability limit of the new energy sending end power grid after the DC bipolar blocking fault; and setting a steady-state voltage control threshold for reducing the transient voltage instability risk of the new energy collection station bus based on the new energy collection station bus transient voltage model. The present application can achieve the purpose of reducing transient voltage instability risk by controlling the steady-state operating voltage of a high-proportion new energy sending end power grid without increasing dynamic reactive power compensation equipment. The present application is used to solve the problem of transient voltage instability caused by new energy off-grid of a new energy collection station of a DC sending end power grid after a DC fault due to excessively high transient voltage caused by excessively high steady-state operating voltage of the power grid.

The present application relates to the field of high-voltage direct current transmission, and aims to provide a topology of bridge arm integrated current-limiting energy-consuming device, a converter valve and a coordinated control method. The topology is a modular MMC architecture of three-phase double bridge arms, which comprises a plurality of MMC sub-modules connected in series in the upper bridge arm, and a current-limiting energy-consuming device composed of a plurality of current-limiting energy-consuming sub-modules connected in series in the lower bridge arm; the current-limiting energy-consuming sub-module comprises a sub-module main power unit and a sub-condition energy-consuming unit, the latter at least contains two energy-consuming units adapted to different fault conditions, and each contains an energy-consuming resistor and an adaptive condition switching device. The present application integrates the functions of direct-current fault current limiting and alternating-current fault energy consumption in the same integrated device, realizes integrated protection of AC and DC faults, does not need to configure multiple sets of separate equipment, and solves the problem of functional redundancy of the traditional scheme. Redundant configuration can be reduced, hardware cost is reduced, system size is reduced, and operation and maintenance complexity is simplified; the risk of device overvoltage breakdown is avoided, and the service life of the equipment is improved.

The application discloses a kind of flexible direct current transmission line fault transient electrical quantity determination methods, comprising: according to the circuit parameter of MMC converter station, construct MMC equivalent circuit when inter-pole short circuit;According to the transmission line parameter obtained, establish the equivalent model of two-port of direct current transmission line under complex frequency domain;According to the equivalent circuit of MMC when inter-pole short circuit and the equivalent model of two-port of direct current transmission line, obtain the expression of direct current fault transient under complex frequency domain;The expression of direct current fault transient under complex frequency domain is carried out Laplace transformation to obtain time domain response, the whole trend of transient process after fault can be given more accurately by the application.The calculation process is simple, avoids the complicated modeling simulation process in traditional simulation method.Meanwhile, it can well reflect the occurrence wave process when overhead line fails.The method can accurately express the overall development trend of the fault current flowing through the protection installation before the converter station is locked after the fault occurs, and has a positive significance for the fault current suppression and protection setting design of MMC-HVDC system.

The present application relates to the technical field of high-voltage direct current transmission, and particularly relates to a non-blocking type direct current fault ride-through control method for a hybrid three-terminal direct current transmission system; comprising the following steps: S1, performing sub-module proportioning design on the hybrid three-terminal direct current transmission system; S2, performing fault detection and triggering, and when the triggering condition is met, performing S3; S3, performing hierarchical fault control strategy, including mode conversion of the LCC converter station and non-blocking control of the FHMMC converter station; S4, when the fault clearing condition is met, resetting the mode conversion of the LCC converter station and stopping the regulation of the DC current size of the FHMMC converter station by the current converter inhibitor. The technical problems of poor fault resistance and operation economy of the LCC-FHMMC hybrid three-terminal direct current transmission system are solved.

The application discloses a method for removing DC fault by temporary blocking of a new energy island power grid sending-out system. When the receiving end detects that the DC current reaches zero for the first time, the fault current is removed by temporary blocking, and the sending end island energy balance is realized by cooperating with an AC energy consumption device, so that the system DC overhead line fault is self-cleared. Compared with the prior art, the proportion of full-bridge sub-modules is reduced, the engineering investment is saved, and the DC current can be prevented from repeatedly fluctuating around zero, and the DC current arc extinction time is shortened. When the DC fault is detected, the outer ring controller of the fault pole of the sending end is switched to the stator module capacitor voltage control. When single-pole operation is performed, the sending end also selects whether to input the AC energy consumption device according to the size of the sub-module voltage, so as to reduce the risk of overvoltage of the fault pole sub-module capacitor and improve the technical problems that the output negative pressure strategy of the prior art needs a high proportion of full-bridge sub-modules, the cost is high, the sub-module overvoltage tripping risk is high, and the DC current arc extinction time is long.

The application discloses a D-T hybrid multi-port DC fault current limiter topology structure and a control method thereof, and belongs to the technical field of DC power transmission and distribution. The fault current limiter is composed of a current limiting branch, an energy consumption branch and a control branch. The current limiting branch contains multiple current limiting inductors; the energy consumption branch includes two branches in which thyristor valve groups and energy consumption resistors are respectively connected in series, and one of the thyristors is replaced by an IGBT; and the control branch is composed of multiple groups of unidirectional diode valve groups. The control method comprehensively judges by monitoring the line current change in real time and combining the DC circuit breaker tripping signal to distinguish between real faults and system disturbances and control corresponding power electronic devices to act. The application adopts a mixed configuration of diode valve groups and thyristors, and is supplemented by key IGBTs, thereby significantly reducing the number of required fully controlled devices under the premise of guaranteeing the multi-port collaborative current limiting and reliable shutdown capability, and having the advantages of low cost, high reliability, and the like.

This invention proposes a hybrid MMC fault clearing control method and apparatus with a low full-bridge ratio. The invention includes: when a DC fault is detected, the DC controller of the sending-end converter switches to fault mode, generates a fault DC internal potential through proportional control, and applies negative limiting to cut off the fault current; the AC controller switches to fault mode, adjusts the energy storage reference value of the full-bridge submodule, and generates an AC frequency deviation; the grid-side converter of the wind turbine sets the AC power reference value to zero, generates a wind turbine frequency deviation based on the power deviation, and updates the voltage phase; after the fault current returns to zero, each controller switches back to normal mode to restore power transmission. This method can quickly cut off the fault current, stabilize wind turbine operation, and ensure system fault ride-through and reliable recovery.

This invention proposes a DC fault ride-through method and apparatus for a new energy islanded DC transmission system. The invention includes: in the event of a DC fault, controlling the receiving-end converter station to enter a zero DC current mode and the sending-end converter station to enter a zero DC voltage mode; the generation unit identifies the fault based on the AC frequency, switches to a load shedding mode, and engages an unloading circuit to dissipate surplus power; when the capacitor voltage of the sending-end converter station submodule drops to a preset threshold, it switches to the zero DC current mode, outputting a negative voltage to quickly suppress the DC current; after the fault is cleared and power is balanced, the converter station resumes normal operation, the generation unit ramps up power recovery, and unloading stops. This invention can quickly suppress faults, stabilize system operation, and achieve smooth recovery after a fault.

The present application relates to a kind of active unloading type true bipolar flexible DC converter and collaborative control method, including converter valve, distributed active unloading branch, DC fast mechanical switch and fault current transfer branch;Distributed active unloading branch includes thyristor, inductance, energy dissipation resistance and thyristor, is closed in normal operation, first guide thyristor to form RLC loop unloading when fault, current reaches threshold and then turns on thyristor bypass inductance and drags tail energy dissipation;DC fast mechanical switch is disconnected after fault and half-bridge submodule is blocked;Fault current transfer branch is closed in normal operation, is closed after DC fast mechanical switch is disconnected, is limited by voltage through diode D current limiting, and fault current is dissipated by energy dissipation resistance.Compared with prior art, the present application has the advantages of quickly blocking DC fault, reducing dependence on external DC circuit breaker, no additional steady-state loss, guaranteeing system operation efficiency and the like.

A method, system, and medium for intelligent AC / DC fault localization based on multi-scale feature adaptive fusion includes: constructing fault datasets X for each region; inputting X into a time-series data convolution module and a gated recurrent unit to obtain and ; obtaining gate weights based on and , and then obtaining fused features; performing graph convolution operations and using an activation function to output fault localization prediction values; obtaining a label smoothed cross-entropy loss function, and updating the fault localization model parameters according to backpropagation until the recognition accuracy meets the requirements; the fault localization model performs fault localization based on AC / DC system fault event data. This invention can realize automated localization of various electrical faults in AC / DC transmission systems, improving the efficiency of fault handling.

This invention discloses a method, system, medium, and device for detecting DC arc faults. The method includes: acquiring line current signals, performing feature processing to obtain feature values, and saving the average value of the features within a preset time period as initial feature values; filtering effective frequency bands whose noise floor values ​​meet set conditions based on the noise floor values ​​of each feature frequency band using a frequency band selection method; calculating arc energy values ​​to obtain dynamic arc energy and static arc energy; and detecting DC arc faults: when both dynamic arc energy and static arc energy exceed their respective thresholds, and the number of DC arc occurrences within a preset time period reaches a preset number, a DC fault arc is detected; otherwise, it is detected as normal. This invention is applied to DC fault arc circuit breakers, which can significantly improve the accuracy and reliability of DC arc detection and reduce the risk of false positives and false negatives in DC arc detection.

This utility model relates to a multifunctional, modularly integrated flexible interconnection device, comprising an AC / DC conversion power unit, a DC fault protection unit, and an expandable power distribution interface unit integrated within a cabinet. The AC input side of the AC / DC conversion power unit is connected to the grid-side distribution area via an isolation transformer. The DC output side of the AC / DC conversion power unit is connected to the DC input side of the DC fault protection unit. The DC output side of the DC fault protection unit is connected to the expandable power distribution interface unit via a first electrical switch for detecting and blocking DC fault current. This utility model can reduce the operational risk of the flexible interconnection device during DC-side short-circuit faults and provides expanded functionality on the output side.

The application discloses a DC high-resistance fault protection method and system for a double-ended hybrid DC system, and belongs to the field of power system relay protection. The method comprises the following steps: when an AC fault occurs at the local side, the double-ended hybrid DC system is switched to an AC fault ride-through mode to remove the AC fault; when a DC fault occurs at the local side, the following operations are performed: according to the fault direction and the fault type of the DC fault, the control mode of the double-ended hybrid DC system is switched; the absolute value of the average value of the DC line voltage in a preset time window under the current control mode is calculated, when the absolute value of the average value is lower than a preset threshold, the DC fault is an intra-zone fault, otherwise, the DC fault is an inter-zone fault; and the DC fault is removed by using corresponding intra-zone fault removal measures or inter-zone fault removal measures. The scheme does not depend on a communication system, has low requirements on devices, has strong tolerance to transition resistance, and is high in protection reliability.

The present application relates to the field of power system fault recovery, and more particularly to a kind of boost converter DC fault adaptive recovery method, device and equipment, adaptive recovery control is carried out to MMC-DR type DC boost converter, comprising: the difference of wind farm active power instruction value and active power actual value is obtained, the active power-voltage control link of realizing internal grid-connected point voltage amplitude coordinated stability is realized through no-static-difference active power control, and d-axis voltage reference value is generated;The difference of reactive power instruction value and reactive power actual value is obtained, the reactive frequency control link of realizing internal grid-connected point frequency coordinated stability is realized through the reactive droop control based on phase-locked loop, q-axis voltage instruction value is generated and real-time angular frequency and phase information are obtained;Through voltage control ring and current control ring, MMC control signal is generated;When detecting that the DC fault of certain port MMC occurs, the MMC of this end is locked, and the MMC of non-fault end is adaptively coordinated to operate at new operating point, i.e. internal AC voltage is stabilized at new amplitude and frequency, to realize fault ride-through;After removing fault, the MMC of fault end is unlocked and MMC control signal is updated, to realize the recovery of fault port.

This invention belongs to the field of chip integration technology and relates to an integrated DC-DC fault handling circuit based on feedback tolerance. It includes: a DC-DC output terminal connected to the input terminal of an output control unit and a fault modulation-feedback coordination unit; an output terminal of the output control unit connected to the input terminal of the fault modulation-feedback coordination unit; an output terminal of the fault modulation-feedback coordination unit connected to the input terminal of a primary-side latch unit and the input terminal of a power transmission control unit; an output terminal of the primary-side latch unit connected to a PG signal module and the input terminal of the power transmission control unit; an output terminal of the PG signal module connected to the input terminal of a dual unlocking control unit; an output terminal of the dual unlocking control unit connected to the input terminals of the primary-side latch unit and the power transmission control unit; and an output terminal of the power transmission control unit connected to the DC-DC input terminal. The fault handling circuit of this invention provides a complete fault detection-modulation-demodulation-latch-unlocking process path, enabling fault handling.

This invention discloses a thyristor-clamped AC voltage MMC and its DC fault current clearing method. The hybrid MMC is equipped with three anti-parallel thyristor branches, forming a loop at the upper end of the upper bridge arm reactor, flowing from phase A to phase B to phase C and back to phase A. When a DC-side short-circuit fault occurs, the thyristor branches are triggered sequentially according to the phase of the three-phase voltage at that time. The back EMF provided by the full-bridge submodule during lockout quickly interrupts the DC fault current. Then, the disconnecting switch is disconnected to isolate the converter from the faulty line. The AC current is naturally interrupted by the thyristor's automatic turn-off characteristic at the zero-crossing point of the AC current. This invention, by controlling the triggering sequence of the thyristor branches, limits a portion of the short-circuit current injected from the AC side into the DC fault location during a fault. This achieves rapid DC fault current interruption while reducing the proportion of the full-bridge submodule and avoiding excessive AC-side overcurrent.

The present application relates to the technical field of direct current (DC) combining, and discloses a DC fault isolation circuit, a combiner box, and a power converter. In the DC fault isolation circuit, among DC power sources connected to any positive-pole switch and DC power sources connected to any negative-pole switch, the number of DC power sources connected to both switches is less than two, so that no parallel connection exists between any two DC power sources; when any DC power source is connected in reverse, and corresponding switches are opened, no reverse currents will be generated between the DC power sources, so that the DC power source connected in reverse can be directly disconnected from the switches connected to both sides thereof without causing arcing, thereby reducing the risk of electric shock to persons and fire. In addition, by cross-connecting DC power sources between different DC / DC converters, the number of switches used can be reduced.

This invention pertains to the fields of DC power transmission and distribution networks and DC microgrids, specifically disclosing an open-winding transformer-type multi-active bridge converter for medium- and low-voltage DC distribution networks and DC microgrids. After a DC port fault occurs, DC fault ride-through can be quickly achieved by bypassing the fault-side converter submodule. Due to the open-winding structure of the transformer, the transformer flux linkage will not feed power to the faulty DC port after bypassing the submodule. Simultaneously, utilizing the fast switching characteristics of power semiconductor devices, a significant amount of fault clearing time is saved compared to mechanical circuit breakers. Meanwhile, the non-faulty submodules can continue to operate normally without interrupting power transmission. This invention provides an effective and feasible DC fault ride-through solution for medium- and low-voltage DC distribution networks and DC microgrids based on dual-active bridge or multi-active bridge converters.

The application discloses a kind of based on the multi-terminal direct current system relay protection method and device of MMC active current limiting, belong to power grid protection field;By limiting the direct current fault current of MMC at k1 times rated current, thereby effectively eliminating short-time direct current short-circuit fault, control is relatively simple, and reliability is higher.On this basis, a kind of MMC hardware and software combined end direct current system relay protection method is presented, reduces the demand to direct current side current limiting reactor, can realize the accurate control of fault current.In addition, a kind of strategy for coping with permanent fault is also proposed, to ensure that multi-terminal direct current system MMC has excellent fault response capability whether in short-time fault or permanent fault.Finally, the MMC dominant direct current short-circuit fault selective protection strategy is presented, using the injected amplitude droop type ac current signal realizes the three-stage selective protection of short-circuit fault, reduces the cost and design requirement of direct current line protection, and is suitable for the multi-terminal direct current system containing complex branch structure.

The application discloses a kind of multiport adaptive direct current fault current limiter, the multiport adaptive direct current fault current limiter includes multiple magnetic core units and circuit unit, wherein, one end of multiple magnetic core units is connected with corresponding direct current port by corresponding direct current circuit breaker, the other end of multiple magnetic core units is connected to high-voltage direct current bus;Circuit unit includes diode bridge circuit and external freewheeling branch, wherein, the midpoint of each bridge arm of diode bridge circuit is respectively connected with the one end of each magnetic core unit, the common cathode end and common anode end of diode bridge circuit are respectively connected with external freewheeling branch to form energy consumption loop.The application can realize the bidirectional, fast, adaptive limitation for the short-circuit fault current of multiport flexible direct current system.

The application discloses a solid-state transformer topology based on complementary sub-module pairs and a fault blocking method, and the topology comprises a medium-voltage alternating-current end, a medium-voltage direct-current end, a low-voltage alternating-current end, a low-voltage direct-current end and a three-phase circuit topology, wherein the three-phase circuit topology comprises three identical single-phase lines, the single-phase line comprises a plurality of complementary sub-module pairs, the complementary sub-module pair comprises a first sub-module and a second sub-module which are structurally identical, and the fault blocking method comprises the following steps: in the case of a direct-current fault, the pulse of all switch tubes in each sub-module is turned off; the capacitor in the capacitor bridge arm is introduced into the current path, and the reverse blocking of the conducting diode is realized by using the capacitor voltage, so that the current path is cut off. Compared with a traditional topology, the number of switch tubes is reduced, and the power density is improved; in the case of a direct-current fault, the current path is effectively cut off, and the stability of the system is significantly improved.

This application provides a cascaded solid-state DC circuit breaker and its control method. The circuit breaker includes a fault detection module, a main switch module, a single-ended drive module, a voltage triggering module, and a dynamic voltage equalization module. The fault detection module generates a drive command when the current meets the fault conditions. The main switch module consists of at least two normally-on SiC JFETs connected in series, used to withstand the DC bus voltage and serve as a fault current interruption path. The single-ended drive module is connected to the gate and source of the lowest-level SiC JFET and applies a turn-off negative bias voltage to it upon receiving the drive command. The voltage triggering module includes an MOV connected in parallel across the drain and source of each SiC JFET, used to apply a reverse bias to the gate and source of the adjacent upstream SiC JFET using the MOV's on-state voltage, triggering the upstream SiC JFET to turn off. The dynamic voltage equalization module includes an RC buffer network connected in parallel across the drain and source of each SiC JFET, used to suppress transient voltage fluctuations during turn-off. Through this structure, rapid interruption and energy absorption of DC fault current are achieved.

The application relates to the technical field of power system relay protection, and discloses a DR-MMC hybrid cascaded system direct-current fault current processing method and system. In the method, based on fault loop state changes, the direct-current fault process of a DR-MMC hybrid cascaded converter is divided into a plurality of fault stages; the dynamic change characteristics of fault current in each fault stage are analyzed, and a fault current analysis sub-result corresponding to the fault stage is determined; each fault current analysis sub-result is integrated according to the time interval of the corresponding fault stage, and a fault current analysis result covering the direct-current fault process of the DR-MMC hybrid cascaded converter is determined; based on the fault current analysis result, the DR-MMC hybrid cascaded converter is subjected to parameter optimization, and the safe operation boundary of the DR-MMC hybrid cascaded system is determined. The application provides a theoretical basis for DR-MMC hybrid cascaded system fault protection design, equipment selection and safe and stable operation.

The application discloses a kind of flexible direct current converter station fault automatic diagnosis method and system, method includes: when the system alarm or tripping is caused by the fault in the flexible direct current converter station station, by collecting monitoring background SER message, fault waveform, and automatically analyzing fault waveform, the fault position and fault type information are obtained, the application realizes the rapid analysis, positioning and auxiliary decision of direct current fault, provides effective technical support for relay protection professional, operating personnel and dispatch personnel, further improves the timeliness, accuracy and reliability of flexible direct current converter station fault judgment and disposal.