110 results about "Dc fault" patented technology

The invention relates to a direct current fault ride-through method, a direct current fault ride-through device, direct current fault ride-through equipment and a medium. The method comprises the following steps: switching a control mode of network-forming type energy storage into an alternating-current voltage control mode or a direct-current control strategy, carrying out coordinated control on devices in a multi-terminal direct-current collecting and sending-out system, clearing fault current, and clearing the fault current by utilizing an active step-down control strategy or the direct-current control strategy at the same time. According to the method, measures such as additional direct current circuit breakers are not needed, control is flexible and easy to achieve, the multi-terminal direct current collecting and sending-out system after fault clearing is controlled to be recovered by judging the operation state of the multi-terminal direct current collecting and sending-out system, and safe and stable operation of the multi-terminal direct current collecting and sending-out system is facilitated.

The invention discloses a flexible direct-current power transmission system and a fault ride-through method and system thereof. The flexible direct-current power transmission system comprises a main control module, and a new energy sending-out system, an alternating-current energy consumption device, a sending-end converter, a direct-current circuit breaker, a receiving-end converter and a receiving-end alternating-current power grid which are connected in sequence, the direct current circuit breaker is deployed on a direct current power transmission line between the sending end converter and the receiving end converter, and the receiving end converter is a modular multi-level converter formed by cascading a plurality of half-bridge sub-modules with damping branches; the main control module is in communication connection with the half-bridge sub-modules, the direct-current circuit breaker and the alternating-current energy consumption device and used for controlling the damping branches of the half-bridge sub-modules in the running state, the direct-current circuit breaker and the alternating-current energy consumption device to act when a direct-current fault occurs so as to restrain direct current and adjust direct-current voltage to be within a set voltage range. Therefore, no-locking fault ride-through is completed. According to the invention, high-reliability and low-cost DC fault ride-through can be realized.

The invention relates to the technical field of high-voltage direct-current transmission, and particularly provides an LCC-full-bridge MMC series light HVDC converter station control method, which comprises the following steps: a rectification side of a power grid commutation converter adjusts direct-current power through an outer ring and an inner ring adopts linear trigger angle control to generate a trigger pulse; transformer tap adjustment is supplemented; on the basis of the established stable direct current system, an inversion side selects a minimum trigger angle as a control signal by coordinating three control rings of a turn-off angle, direct current voltage and direct current to form a control system; the full-bridge modularized multi-level converter is switched to a power grid following and network construction control mode according to power grid conditions; and when a direct current fault is detected, setting the trigger angle of the commutation converter of the power grid to be 90 degrees and switching the full-bridge modular multi-level converter to an STATCOM mode, thereby realizing direct current fault ride-through without locking the converter. According to the invention, direct-current fault rapid ride-through of the non-locking converter is realized.

The invention provides a medium-voltage direct-hanging multi-level energy storage grid-connected direct-current fault isolation method and device. The method comprises the following steps of: establishing corresponding protection partitions on a phase arm, a bus section and a battery cluster, configuring a polarity controllable blocking sub-module capable of being inserted with reverse voltage on the phase arm, and respectively configuring direct-current circuit breakers on the bus section and the battery cluster; generating a criterion set based on the measured value, and performing consistency voting on the criterion set to obtain a direct current fault determination result and a partition positioning result; when a fault is determined, issuing modulation and zero setting, and calculating a reverse equivalent voltage according to the change rate of the phase arm current and the target current to trigger the insertion of a polarity controllable blocking sub-module; selectively driving a corresponding direct current circuit breaker to be switched on and off according to a partition positioning result, or splitting a fault phase arm; and after selective switching-off is completed, outputting an isolation state to a grid-connected control unit of the energy storage grid-connected system. According to the invention, millisecond-level robust fault discrimination, partition selective isolation, cooperation of current limiting and on-off can be realized, and the removal range is narrowed.

The embodiment of the invention provides a method and a system for adjusting the capacitance value of a half-bridge sub-module. The method comprises the following steps: acquiring an initial capacitance value of a capacitor meeting steady-state operation voltage fluctuation constraint and dynamic response time constraint; obtaining a resistance value range of a resistor in the damping branch under the multi-condition constraint; wherein the multi-condition constraint comprises a current limiting condition constraint of the flexible direct-current power transmission system based on the initial capacitance value when a direct-current fault occurs, and a transient stability condition constraint of the flexible direct-current power transmission system when an alternating-current fault occurs; based on the resistance value range, obtaining an introduced transient voltage fluctuation range of the capacitor through simulation; obtaining a selectable capacitance value range in which the capacitance meets the transient operation condition constraint corresponding to the introduced transient voltage fluctuation range; and replacing the initial capacitance value with the capacitance value in the optional capacitance value range to obtain a target capacitance value of the capacitor. According to the invention, the engineering cost of the flexible DC power transmission system can be reduced on the basis of realizing AC / DC fault non-locking fault ride-through.

The application discloses a DC line single-end fault ranging method and system with self-calibration capability, and belongs to the technical field of DC line fault positioning. The technical problem to be solved is that the anti-interference capability of a DC fault ranging technology is weak, parameter drift cannot be calibrated, double-end synchronization is required, and engineering implementation is complex. Technical scheme points are as follows: an excitation signal is injected into a fault line through an H-bridge circuit unit, an H-bridge output voltage and a line port voltage after an external calibration inductor are synchronously collected, and a line fault loop current zero-crossing moment is detected; at the zero-crossing moment, two groups of voltage equations are used to solve an external calibration inductor calculation value in real time, the inductor calculation value is compared with a nominal value to obtain an inductor correction coefficient, online self-calibration of the line inductor is realized; and based on the calibrated line inductor, fault discrimination and distance calculation are completed in combination with a relationship between a port voltage and a current slope.

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 application discloses a DC fault ride-through method of a sea-land integrated DC system of offshore wind power based on a fast communication link, and the method comprises the following steps: when a DC fault occurs, the voltage drop speed and the voltage drop amplitude of an onshore converter station are obtained; when the voltage drop speed is lower than a voltage drop speed threshold value and the voltage drop amplitude is lower than a voltage drop amplitude threshold value, a fan energy consumption input instruction is sent to an offshore converter station, so that the offshore converter station transmits the fan energy consumption input instruction to each communication forwarding device through a bidirectional ring network optical fiber channel, and then the fan energy consumption input instruction is transmitted to corresponding fan energy consumption devices by the communication forwarding devices, so that the fan energy consumption devices absorb the fault surplus power according to the fan energy consumption input instruction; wherein the time from the issuance of the fan energy consumption input instruction from the HVDC side to the start of the fan energy consumption device is not greater than the maximum allowable delay duration.

The invention discloses a DC fault current analysis and calculation method suitable for multi-type MMC converters, and the method comprises the steps: determining the topology type of an MMC converter related to a fault line, and collecting core parameters; constructing an RLC series unified equivalent circuit model of the MMC, and correcting the RLC series unified equivalent circuit model based on the topology type to obtain an equivalent circuit correction model; and determining a DC fault current based on the equivalent circuit correction model. According to the method, a technical architecture of'unified modeling + differential correction 'is constructed, multiple types of MMC converters are abstracted into an RLC basic equivalent model, local parameter correction is carried out only for fault characteristic differences of different topologies, and the tedious process of repeated modeling is effectively avoided; meanwhile, converter active current limiting strategies such as locking and negative input control are considered in the modeling process of fault current analytical calculation, the model architecture has good expansibility, various control strategies can be flexibly fused, and deep fusion of the electromagnetic transient process and the control process is achieved.

The application discloses a kind of hybrid line DC fault ride-through control method, device and system, belong to flexible HVDC transmission technology.The DC fault ride-through control method of the application, first, the actual DC current corresponding to DC line in flexible HVDC transmission system is monitored, and the actual DC current in abnormal target line is obtained;Then according to the actual DC current corresponding to target line, the DC reference voltage corresponding to target line is adjusted to fault ride-through voltage reference value, to control the DC current corresponding to target line to be set value of fault ride-through;Finally, in the case where the actual DC voltage corresponding to target line satisfies preset recovery condition, the DC reference voltage corresponding to target line is restored to preset reference voltage value.The DC fault ride-through method of the application is fast in response speed, can also reduce the influence on output power, reduce power loss, improve the stability and reliability of flexible HVDC transmission system operation.

The invention provides a low-conduction-loss direct-current circuit breaker with a fault type judgment function and a judgment method, and belongs to the field of circuit fault detection. In order to solve the problems that in an existing hybrid high-voltage direct-current circuit breaker, the conduction loss of a load commutation switch is high, and a circuit device does not have the fault type discrimination capability, the direct-current circuit breaker comprises a load branch, a multifunctional branch, a main breaking branch and an energy absorption branch. The discrimination method comprises the following steps: in a normal operation mode, a load branch is conducted; the capacitor pre-charging mode operates in parallel to charge the capacitor C; when the circuit is short-circuited, a thyristor turn-off mode is entered, and the T1 is turned off; and entering a load commutation mode, converting the fault current to a main breaking branch, introducing an energy absorption branch, and entering an energy absorption mode. And injecting a controlled RLC oscillation current, analyzing current waveform characteristics to judge a direct current fault type, and performing reclosing or maintenance of the circuit breaker according to the analyzed direct current fault type.

The invention provides a direct-current fault arc extinguishing system, which is applied to a direct-current power grid and comprises a magnetic core module with an air gap, a driving module and a control module, and the driving module is connected with the magnetic core module and the control module; the magnetic core module is used for reconstructing and generating reverse voltage based on fault current in the direct-current power grid; and the control module is used for acquiring fault current at a first sampling frequency, determining a current change rate based on the first sampling frequency and the fault current, determining a control strategy for the air gap when the current change rate is greater than or equal to a preset threshold value, controlling the driving module to adjust the air gap based on the control strategy, and changing the magnetic coupling strength of the magnetic core module. Therefore, the reverse voltage is controlled to reach a voltage arc extinguishing threshold value. The magnetic coupling strength of the magnetic core is changed by dynamically adjusting the air gap, accurate control over reverse voltage is achieved, stable arc extinguishing voltage output is maintained when fault current fluctuates, and the action reliability of an arc extinguishing system is improved.

The invention provides a quantitative evaluation method and system suitable for the voltage supporting capability of multiple types of reactive power equipment, and a storage medium. By setting alternating current and direct current faults, grid-connected point data of different reactive power devices are obtained; based on the dynamic characteristics of the reactive power equipment and factors affecting the power grid strength, a reactive power equipment voltage supporting capacity multi-index evaluation system considering the two aspects of the reactive power equipment and a power system is provided; constructing a cooperative game combination weight optimization model by adopting a deviation minimization principle, and calculating the weight of each index; proposing a construction method of a central point mixed sine whitening weight function, and carrying out gray fixed weight clustering evaluation on the voltage supporting capability of the multi-type reactive power equipment; and finally, verifying the accuracy and universality of the method provided by the invention based on PSASP simulation. According to the method, the influence of the dynamic characteristics of the reactive power equipment on the voltage supporting capacity is considered, and the index system is more comprehensive, the index weighting is more reasonable and the evaluation result is more credible based on the improved grey whitening weight function fixed weight clustering evaluation.

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 invention relates to the technical field of direct current fault detection, and discloses a direct current series arc fault detection method and device, a photovoltaic inverter and a medium. And processing the input voltage and the input current of the photovoltaic inverter to obtain a characteristic data training set under the condition that the arc generator simulates the photovoltaic inverter to generate a direct current series arc fault and the condition of normal operation, wherein each arc fault detection model is obtained by pre-training based on the corresponding characteristic data set. The method comprises the following steps: firstly, acquiring an input side voltage and an input side current of the photovoltaic inverter, and processing the input side voltage and the input side current respectively to obtain multiple groups of feature data including voltage feature parameters and current feature parameters; then, the multiple sets of feature data are input into a pre-trained corresponding arc fault detection model for processing, and multiple fault detection results are obtained. And finally, based on a plurality of fault detection results, a voting mechanism is adopted to determine whether the photovoltaic inverter has a DC series arc fault.

The application discloses a new energy sending end power grid DC fault transient overvoltage influence evaluation method and system and a readable storage medium, and belongs to the technical field of power grid fault detection. The method takes overvoltage amplitude, overvoltage duration, fault type and system impedance as influencing factors, determines the membership degrees of various factors at different influence levels according to the corresponding single-factor fuzzy evaluation membership degree matrix of the factor level query, and performs weighted summation on the membership degrees of various factors at different influence levels and the influence weights of various factors to calculate the final membership degrees of various influence levels, and takes the influence level corresponding to the maximum final membership degree as the evaluation level. Through effective processing of fuzzy information, the application can make accurate evaluation under complex power grid fault conditions, thereby reducing the potential risk of overvoltage to the system and equipment and improving the safety and reliability of the power system.

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 application discloses a kind of generator phase-advancing capability analysis method and system based on power grid transient stability constraint, comprising the following steps: according to power grid system stability and converter station bus voltage control condition obtains single machine maximum phase-advancing depth;According to single machine maximum phase-advancing depth, obtain the phase-advancing depth of power plant and the phase-advancing depth reserved by whole plant.This application mainly aims at the problem that the regulation range of other regulating means such as shunt reactor is limited when voltage is too high due to excessive reactive power, fully considers factors such as stator end heating and power angle static stability, determines single machine maximum phase-advancing depth, considers the most serious situation of overvoltage of DC converter station, determines the phase-advancing capability of power plant and the phase-advancing capability reserved by whole plant after DC fault tripping based on whether steady-state overvoltage exceeds voltage limit, fully develops the voltage regulating capability of generator, so as to more economically and efficiently ensure the stable operation of power grid voltage.

The invention provides a DC fault ride-through method and device of a current converter, a storage medium and a current conversion system, the current converter comprises three phases, each phase comprises two bridge arms, and the method comprises the following steps: a first obtaining step: obtaining a first current and a historical bridge arm state; a first determination step of determining that the first bridge arm operates in a first target state according to the magnitude of the first current and the number of locking states, the number of the locking states being the number of second bridge arms corresponding to the locking states in the historical bridge arm states; a first control step of controlling the first bridge arm to operate in a first target state; and a first repeating step: sequentially repeating the first obtaining step, the first determining step and the first control step for at least one time, and in the repeating process, updating the first bridge arm in the first obtaining step to be the next bridge arm of the first bridge arm until the control of all bridge arms is completed, the technical problem of how to avoid the overall locking of the converter in the DC fault ride-through process of the converter in the prior art is solved.

The application discloses a hybrid MMC control method and system, which comprises the following steps: under the working conditions of voltage reduction / half voltage operation of a converter station, on-line switching of a single valve group and DC fault ride-through, a control pulse is formulated according to a converter voltage reference value formulated by capacitor voltage of a sub-module in an MMC converter valve, an arm current loop injection voltage value formulated by a time-varying value of an arm current loop and a DC voltage given value formulated by a DC current given value, and the hybrid MMC is controlled to be put into operation. According to the converter voltage reference value formulated by the capacitor voltage of the sub-module in the MMC converter valve, the hybrid MMC can ensure that the MMC arm current zero-crossing point is guaranteed, capacitor voltage balance is realized and system collapse caused by separation of capacitor voltage of a full-bridge sub-module and the capacitor voltage of the sub-module is avoided under special working conditions. The time-varying value formulated by the arm current loop of the MMC converter valve obtains an expected value of the arm current loop injection, and the arm current always has a zero-crossing point through an arm current loop injection link, so that the safe operation of the MMC arm is ensured.

According to the multi-mode programmable direct-current cable fault current simulation device and the control method thereof, the coil is wound on the magnetic core of the Hall current sensor of the direct-current cable, and the current source is controlled to inject the programmable current into the coil, so that non-intrusive fault current simulation is realized; the system can effectively reproduce steady-state fault current, transient sudden-increase fault current and a superposition process thereof, is convenient for testing, debugging and verification of a direct-current fault early warning system, and has the advantages of simple structure, flexible control, safety and reliability.

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 invention provides a bridge arm multiplexing type MMC system based on structural adaptation and a dynamic switching strategy and a direct current fault clearing method. According to the fault clearing method, after a direct current side short circuit fault is detected, a structurally adaptive dual-channel auxiliary commutation circuit is utilized to reconstruct a specific bridge arm from parallel connection to bidirectional serial connection, and dynamic switching control logic is executed in combination with the bridge arm current flow direction monitored in real time; and automatically matching the optimal back pressure path from a plurality of preset transient modes. Through cooperation of hardware topology reconstruction and a software control strategy, the reverse electromotive force of the system can be instantaneously increased to a rated voltage level, the problem of current turn-off failure caused by insufficient reverse voltage under a bridge arm multiplexing architecture is effectively solved, and the uncontrollable rectification overvoltage risk of a non-multiplexing bridge arm is synchronously avoided.

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 kind of DC fault arc precision detection and efficient protection method under power electronic interference, based on system output current signal, the frequency information of the signal short-time Fourier transform is made variance processing to obtain first characteristic quantity, the common frequency band of fault arc is obtained by combining evidence classifier and with normal waveform sampling comparison, whether there is fault arc existence is judged from this, similarly, the difference frequency band of fault arc is obtained by evidence classifier, the topological structure and control strategy of fault arc difference frequency band identification device can be reached, and the purpose of efficient protection is further achieved.The application can significantly improve the effect of DC fault arc precision detection and efficient protection.

The invention relates to the technical field of power system relay protection, and discloses a DC fault current processing method and system for a DR-MMC hybrid cascade system. The method comprises the following steps: dividing a DC fault process of the DR-MMC hybrid cascade converter into a plurality of fault stages based on fault loop state change; the fault current dynamic change characteristic of each fault stage is analyzed, and a fault current analysis sub-result of the corresponding fault stage is determined; integrating each fault current analysis sub-result according to the time interval of the corresponding fault stage, and determining a fault current analysis result of the DR-MMC hybrid cascade converter covering the DC fault process; and parameter optimization is carried out on the DR-MMC hybrid cascade converter based on the fault current analysis result, and the safe operation boundary of the DR-MMC hybrid cascade system is determined. The method provides a theoretical basis for fault protection design, equipment selection and safe and stable operation of the DR-MMC hybrid cascade system.

The application relates to a direct-current fault ride-through sending-end alternating-current voltage stability control method of a new energy sending end. The method comprises the following steps: acquiring direct-current line operation data; in the case that the direct-current line operation data is detected to have abnormal data, sending an instruction to switch the control mode of a fault pole of a sending-end converter from a network-constructing type control mode to a network-following type control mode, and starting a de-ionization process by reducing the direct-current side voltage; the network-following type control mode is an active power and reactive power decoupling control mode; after the de-ionization process is completed, the fault pole of the sending-end converter is controlled to recover from the network-following type control mode to the network-constructing type control mode, and the fault pole of the sending-end converter and a non-fault pole of the sending-end converter are controlled to be put into a capacitor voltage average value control mode; in the case that the capacitor voltage average value control mode exceeds a preset time period, the capacitor voltage reference value change amount is controlled to be zero according to a preset descending rate, and a corresponding target voltage value of a direct-current transmission line is output, so that the stability of the sending-end alternating-current voltage can be improved.

The invention discloses a multi-port alternating current and direct current fault handling device for a multi-port direct current transmission sending-out system, and the device is provided with n ports which are recorded as Port1-Portn. Each port is respectively connected with one end of a bypass branch, one end of a feed flow branch and one end of an injection branch; the other end of the bypass branch, the other end of the feed current branch and the other end of the injection branch are connected to a direct-current bus Bus1, a direct-current bus Bus2 and a direct-current bus Bus3 respectively. In the fault current breaking process, the feed current branch, the injection branch and the valve group Valve1 form an H-bridge structure, so that the bidirectional fault current breaking capacity is realized; when the Bus1 or the Bus3 has a direct-current fault, the fault current is blocked by the H-bridge structure; the device has DC fault isolation and AC / DC fault ride-through capabilities, can quickly cut off a fault current when a DC short circuit occurs, and stabilizes a DC voltage during an AC fault or DC fault de-dissociation period.