CN112003252A - Line fault removing device and direct current system - Google Patents

Abstract

The present application relates to a line fault removal device and a DC system. The line fault removal device is provided with the current generation device. When a short-circuit fault occurs in any branch, the current generation device can generate a fault maintenance current. The fault maintenance current flows into the branch where the short-circuit fault occurs through the DC bus, so as to maintain the short-circuit current on the faulty branch, so that the circuit breaker on the faulty branch operates to cut off the short-circuit fault on the branch. By providing the current generating device in the embodiments of the present application, the technical problem of poor working stability of the current DC system existing in the prior art is solved, and the technical effect of improving the working stability of the DC system is achieved.

Description

Line fault removal device and DC system

technical field

The present application relates to the technical field of power grid fault safety, and in particular, to a line fault removal device and a DC system.

Background technique

At present, a DC system generally includes a DC bus and various branches, and each branch is generally provided with a converter. With the increasing development of the DC system, the fault protection of the converters in each branch has become more and more perfect. The converter can quickly enter the short-circuit protection state in the face of a short-circuit fault. For the sake of insurance, each branch is generally equipped with If there is a circuit breaker, the short-circuit protection action time of the converter is much shorter than the action time of the circuit breaker. When a short-circuit fault occurs in the branch, the converter stops working, but the circuit breaker has not been disconnected in time, and the fault cannot be eliminated in time. When the DC system is powered on again, because the fault of the faulty branch has not been eliminated, the remaining branches that have not failed will still enter the short-circuit protection and cannot work normally. Therefore, the current working stability of the DC system is poor.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a line fault removal device and a DC system for the problem of poor working stability of the current DC system.

A line fault removal device is applied to a DC system, the DC system includes a DC bus and a plurality of branches, the multiple branches are connected in parallel and are respectively electrically connected to the DC bus, and each branch is provided with There are circuit breakers and converters connected in series, and the line fault removal device includes:

A current generating device is used for being electrically connected to the DC bus, and used for generating a fault maintenance current, and the strength of the fault maintenance current is not less than that of the short-circuit current of each branch.

In one embodiment, the current generating device includes:

an AC power source for generating said fault to maintain the AC power;

A rectifier, the input end of the rectifier is electrically connected to the AC power source, and the output end of the rectifier is electrically connected to the DC bus, and the rectifier is used for converting the fault-sustaining alternating current into the fault-sustaining current.

In one of the embodiments, the AC power source is a single-phase AC power source.

In one embodiment, it also includes:

A transformer, the input end of the transformer is electrically connected to the AC power source, and the output end of the transformer is electrically connected to the rectifier.

In one embodiment, the rectifier includes:

a first diode assembly, the anode of the first diode assembly is electrically connected to the AC power source, and the cathode of the first diode assembly is electrically connected to the anode of the DC bus;

A second diode assembly, the cathode of the second diode assembly is electrically connected to the AC power source, and the anode of the second diode assembly is electrically connected to the cathode of the DC bus.

In one of the embodiments, the AC power source is a three-phase AC power source;

The first diode assembly includes three first diodes, the anodes of the three first diodes are respectively electrically connected to the three-phase of the AC power supply, and the three first diodes are electrically connected to each other. The negative electrodes are all electrically connected to the positive electrodes of the DC bus;

The second diode assembly includes three second diodes, the anodes of the three second diodes are respectively electrically connected to the three phases of the AC power supply, and the three second diodes are The negative electrodes are all electrically connected to the negative electrodes of the DC bus.

A direct current system comprising:

DC bus, including positive and negative wires,

a plurality of branches, which are connected in parallel with each other and are respectively electrically connected to the DC bus, and each branch is provided with a circuit breaker and a converter in series;

In the above-mentioned line fault removal device, the current generating device is electrically connected to the DC bus for generating a fault maintenance current, and the strength of the fault maintenance current is not less than that of the short-circuit current of each branch.

In one embodiment, the converter includes:

converter body;

A protector, one end of the protector is electrically connected to the circuit breaker, and the other end is electrically connected to the converter body, the protector is used to control the circuit breaker when the current flowing through the converter body exceeds a preset threshold The converter body stops working.

In one embodiment, the protector includes:

a current detection component, electrically connected to the converter body, for detecting the current flowing through the converter body;

The control assembly is signally connected to the inverter body and the current detection assembly respectively, and is used for controlling the inverter body to stop working when the current flowing through the inverter body exceeds a preset threshold.

In one embodiment, it also includes:

A central control device is signal-connected to a plurality of the circuit breakers respectively, and the central control device is used to determine whether a plurality of the branches are faulty according to the operation state of the circuit breakers, and to determine a faulty branch when a fault occurs.

The line fault removal device provided in the embodiment of the present application is provided with the current generating device, and when a short-circuit fault occurs in any branch, the current generating device can generate a fault maintenance current, and the fault maintenance current flows into the DC bus through the DC bus. The branch in which the short-circuit fault occurs, so as to maintain the short-circuit current on the faulty branch, so that the circuit breaker on the faulty branch operates to cut off the short-circuit fault on the branch. By providing the current generating device in the embodiments of the present application, the technical problem of poor working stability of the current DC system existing in the prior art is solved, and the technical effect of improving the working stability of the DC system is achieved.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the traditional technology, the following briefly introduces the accompanying drawings that are used in the description of the embodiments or the traditional technology. Obviously, the drawings in the following description are only the For some embodiments of the application, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

1 is a schematic structural diagram of a line fault removal device and an application environment thereof provided by an embodiment of the present application;

2 is a schematic structural diagram of a current generating device in a line fault removal device provided by an embodiment of the present application;

3 is a schematic structural diagram of a rectifier in a line fault removal device provided by an embodiment of the present application;

4 is a schematic structural diagram of a line fault removal device and an application environment thereof provided by an embodiment of the present application;

5 is a schematic structural diagram of a part of a line fault removal device provided by an embodiment of the present application;

6 is a schematic structural diagram of a DC system provided by an embodiment of the present application;

7 is a schematic structural diagram of a converter in a DC system provided by an embodiment of the present application;

8 is a schematic structural diagram of a protector in a DC system provided by an embodiment of the present application;

FIG. 9 is a schematic structural diagram of a DC system provided by an embodiment of the present application.

Description of reference numbers:

10. Line fault removal device;

100. Current generating equipment;

110. AC power supply;

120. Rectifier;

121. A first diode assembly;

1211. The first diode;

122. A second diode assembly;

1221, the second diode;

200, transformer;

30. DC system;

300, DC bus;

400, branch;

410, circuit breaker;

420. Converter;

421. The converter body;

422, protector;

4221. Current detection components;

4222. Control components;

500. Central control equipment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the following embodiments and in conjunction with the accompanying drawings, a line fault removal device and a DC system of the present application will be further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

The serial numbers themselves, such as "first", "second", etc., for the components herein are only used to distinguish the described objects, and do not have any order or technical meaning. The "connection" and "connection" mentioned in this application, unless otherwise specified, include both direct and indirect connections (connections). In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", The orientation or positional relationship indicated by "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description , rather than indicating or implying that the referred device or element must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation on the present application.

In this application, unless otherwise expressly stated and defined, a first feature "on" or "under" a second feature may be in direct contact with the first and second features, or the first and second features indirectly through an intermediary touch. Also, the first feature being "above", "over" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

Referring to FIG. 1 , an embodiment of the present application provides a line fault removal device 10 , which can be applied to a DC system 30 for removing short-circuit faults in the DC system 30 . The DC system 30 generally includes a DC bus 300 and a plurality of branches 400. The plurality of branches 400 are connected in parallel and are respectively electrically connected to the DC bus 300. Each of the branches 400 is arranged in series with each other. circuit breaker 410 and converter 420. When a short circuit fault occurs in one of the branches 400 , the line fault removal device 10 operates the circuit breaker 410 by generating a fault sustaining current, thereby removing the line fault of the faulty branch 400 . The following embodiments are described in detail by taking the application of the line fault removal device 10 to the DC system 30 as an example.

An embodiment of the present application provides a line fault removal device 10 , including: a current generating device 100 .

The current generating device 100 is electrically connected to the DC bus 300 for generating a fault-sustaining current, and the strength of the fault-sustaining current is not less than that of the short-circuit current of each branch 400 . The current generating device 100 may be a fixed power supply, a mobile power supply, or other voltages with stable and large current output. The fault maintenance current can be determined according to the historical data of the daily short-circuit fault currents of the multiple branches 400, such as 80A, 106A, etc., or can be determined according to real-time measurement, which is not limited in this embodiment, and can be determined according to actual needs. specific selection or setting. The fault maintenance current may be fixed or adjustable, for example, according to the different loads on each of the branches 400, according to the short-circuit current of the branch 400 when a short-circuit fault occurs, determine the different strengths of the current. the fault holding current.

The working principle of the line fault removal device 10 provided in the embodiment of the present application is as follows:

The embodiments of the present application provide a line fault removal device 10 including a current generating device 100 . When the DC bus 300 works normally, the plurality of branches 400 also work normally. When a short circuit fault occurs in one of the branches 400, the current on the branch 400 increases instantaneously to generate a short-circuit current. The action time of the circuit breaker 410 is much longer than the action time of the converter 420. Therefore, once a short-circuit current is generated, the converter 420 will act first, automatically shut down, and start the protection mode, so that the circuit breaker 410 has not yet worked. , the short-circuit current on the branch 400 has been cleared, and the circuit breaker 410 has not yet operated, which means that the short-circuit fault on the branch 400 has not been removed. Once the line is powered on again, the short-circuit fault of the branch 400 still exists, and most of the current on the DC bus 300 flows into the faulty branch 400, so that other unfaulted branches 400 cannot work normally. In this embodiment, the current generating device 100 is provided, the current generating device 100 can generate a fault maintenance current, and the current generating device 100 is electrically connected to the DC bus 300 as the DC bus 300 and the fault branch 400 Provides a fault maintenance current, the fault maintenance current flows into different branches 400 through the DC bus 300, and most of the current flows into the branch 400 in which the short-circuit fault occurs, thereby maintaining the short-circuit current of the branch 400 in which the short-circuit fault occurs, so that all The circuit breaker 410 is activated to remove the short-circuit fault on the branch 400 . When the line is powered on again, the circuit breaker 410 has been disconnected, the short-circuit fault has been removed, and the other branches 400 can continue to work normally, thereby maintaining the normal and stable operation of the line.

By providing the current generating device 100 in this embodiment of the present application, when a short circuit fault occurs in any branch 400 , the current generating device 100 can generate a fault maintenance current, and the fault maintenance current flows into the DC bus 300 and a short circuit occurs. The faulty branch 400 is used to maintain the short-circuit current on the faulty branch 400 , so that the circuit breaker 410 on the faulty branch 400 operates to cut off the short-circuit fault on the branch 400 . By providing the current generating device 100 in the embodiment of the present application, the technical problem of poor working stability of the current DC system 30 existing in the prior art is solved, and the technical effect of improving the working stability of the DC system 30 is achieved.

Referring to FIG. 2 , in one embodiment, the current generating device 100 includes: an AC power source 110 and a rectifier 120 .

The AC power source 110 is used to generate a fault to maintain the AC power. The AC power source 110 can provide stable current for the DC bus 300 and is easy to obtain, for example, it can directly draw electricity from the grid, or use a portable power generating device such as a hand generator to generate electricity directly, with high flexibility. The output voltage of the AC power source 110 may be 110V, 220V, etc., which is not limited in this embodiment, and only needs to satisfy the function of providing stable AC power.

The input end of the rectifier 120 is electrically connected to the AC power source 110, and the output end of the rectifier 120 is electrically connected to the DC bus bar 300. The rectifier 120 is used to convert the AC power to the DC power. The rectifier 120 is used for converting the fault-sustaining alternating current into the fault-sustaining current, so as to be conveniently provided to the DC bus 300 for maintaining the short-circuit current in the branch where the short-circuit fault occurs. The rectifier 120 can use a traditional silicon rectifier, the technology is mature, and the price is relatively low. The rectifier 120 can also use other types of rectifiers. This embodiment does not limit the specific model, type, etc. of the rectifier 120. It can be selected according to the actual situation, and only needs to satisfy the function of converting the fault-sustaining alternating current into the fault-sustaining current.

Referring to FIG. 3 , in one embodiment, the rectifier 120 includes: a first diode component 121 and a second diode component 122 .

The anode of the first diode assembly 121 is electrically connected to the AC power source 110 , and the cathode of the first diode assembly 121 is electrically connected to the anode of the DC bus 300 . The first diode assembly 121 may include a plurality of diodes, and the plurality of diodes may be connected in parallel or in series in sequence. When the plurality of diodes are connected in parallel, the anodes of the plurality of diodes are connected to each other. The AC power source 110 is electrically connected, and the cathodes of the diodes are all electrically connected to the anodes of the DC bus 300 . Therefore, when the DC bus 300 is working normally, each branch 400 is loaded, and the potential of the DC bus 300 is higher than that of the current generating device 100, so the current at the DC bus 300 will not flow backwards to the current generating device 100 end. Only when a short-circuit fault occurs at the end of the DC bus 300, the load at the end of the branch circuit 400 is reduced, and the potential at the end of the DC bus 300 is lower than the potential of the current generating device 100, so that the fault generated by the current generating device 100 is maintained. Current can flow to the DC bus 300 to maintain the short circuit current of the faulty branch 400 so that the circuit breaker 410 can operate to clear the line fault of the faulty branch 400 . The diodes may be contact diodes, surface contact diodes, planar diodes, etc., which are not specifically limited in this embodiment, and may be selected according to actual conditions.

The cathode of the second diode assembly 122 is electrically connected to the AC power source 110 , and the anode of the second diode assembly 122 is electrically connected to the cathode of the DC bus 300 . The second diode assembly 122 may include a plurality of diodes, and the plurality of diodes may be connected in parallel or in series in sequence. When the plurality of diodes are connected in parallel, the anodes of the plurality of diodes are connected to each other. The negative electrodes of the DC bus 300 are electrically connected, and the negative electrodes of the plurality of diodes are all electrically connected to the AC power source 110 . The second diode component 122 is used to maintain the unidirectional conduction of the circuit, so that the current can flow unidirectionally from the negative electrode of the DC bus 300 to the AC power source 110 to form a unidirectional loop, and prevent the current from flowing back to ensure The stability of the operation of the current generating device 100 and the entire circuit. The diodes may be contact diodes, surface contact diodes, planar diodes, etc., which are not specifically limited in this embodiment, and can be selected according to actual conditions, as long as the function of maintaining the unidirectional conduction of the loop is required.

In one embodiment, the AC power source 110 may be a single-phase AC power source 110, that is, one wire drawn from the three-phase AC power source in the power grid system is used as a phase wire, and the other wire is taken as a neutral wire. The phase line and the neutral line form a loop through the load, and an additional line is grounded for grounding. The phase line and the neutral line form a loop to provide a stable power supply for the DC bus 300, and the ground wire plays a protective role. The single-phase AC power source 110 has a wide range of sources and is relatively safe to use, such as a household 220V AC power source, etc., and has high flexibility.

Referring to FIG. 4 , in one embodiment, the AC power source 110 is a three-phase AC power source 110 , the first diode component 121 includes three first diodes 1211 , three of the first diodes The anodes of the tubes 1211 are respectively electrically connected to the three phases of the AC power source 110 , and the cathodes of the three first diodes 1211 are all electrically connected to the anodes of the DC bus 300 . The second diode assembly 122 includes three second diodes 1221, the anodes of the three second diodes 1221 are respectively electrically connected to the three-phase of the AC power supply 110, and the three second diodes 1221 are The cathodes of the diodes 1221 are all electrically connected to the cathodes of the DC bus 300 . The three-phase AC power supply 110 can generate a rotating magnetic field, save wires in power transmission to reduce costs, the three-phase AC power supply can be powered by an asynchronous motor, etc., and has high flexibility. At the same time, the three-phase AC power supply 110 The power supply to the single-phase load is not excluded, and the compatibility is strong, and the application range and use flexibility of the line fault removal device 10 in this embodiment can be greatly improved by using the three-phase AC power supply. The first diode 1211 and the second diode 1221 may be any one or a combination of contact diodes, surface contact diodes, and planar diodes, which are not specifically limited in this embodiment. Choose according to the actual situation.

Referring to FIG. 5 , in one embodiment, the line fault removal device 10 further includes: a transformer 200 .

The input end of the transformer 200 is electrically connected to the AC power source 110 , the output end of the transformer 200 is electrically connected to the rectifier 120 , and the transformer 200 is used to convert the voltage of the AC power source 110 into a preset voltage , that is, the voltage required to generate the fault-sustaining current. The preset voltage is set according to the actual situation, and is adjusted according to the loads of different DC systems 30. The transformer 200 can greatly improve the adaptability and application range of the fault removal device.

Referring to FIG. 6 , an embodiment of the present application provides a DC system 30 , including: a DC bus 300 , a branch circuit 400 , and a line fault removal device 10 .

The DC bus 300 refers to the DC common bus in the power consumption system, and belongs to the drive system in the power consumption system. The DC bus 300 generally includes two wires: a positive wire and a negative wire. The DC system 30 is generally an independent power source, which is not affected by the operation mode of the generator and the motor system used in the power plant, and can ensure that the backup power source or the battery continues to provide DC voltage in the event of an external AC power interruption. The DC bus 300 is to connect the external power source and the loads in the system to form a local topology network, and provide current for each load in the power consumption system. The DC bus 300 can be a plastic cable, a high-medium and low-voltage cross-linked cable, etc. Both the plastic cable and the high-medium and low-voltage cross-linked cable can be buried underground, with a large cross-section, which can support high-voltage and ultra-high-voltage remote power transmission, and has a wider application range. , so as to improve the application range of the DC system 30 in this embodiment. This embodiment does not impose any limitation on the type or quantity of the DC bus bars 300, and can be selected according to actual conditions.

The number of the branches 400 is multiple, the multiple branches 400 are connected in parallel, each of the branches 400 is electrically connected to the DC bus 300, and each of the branches 400 is connected to each other. independent. Each branch 400 is an independent line with different loads to perform different functions, but each branch 400 is provided with a circuit breaker 410 and a converter 420 connected in series. Different numbers and types of loads are connected in series with the device 420 . The circuit breaker 410 is used to disconnect and remove the short-circuit fault in time when a short-circuit fault occurs in the branch circuit 400, so as to protect the branch circuit 400 from being damaged or even burnt due to short-circuit current. The converter 420 is an electronic device for performing DC-DC conversion, and the converter 420 converts the current on the DC bus 300 into the working current required by the load on the branch 400 to ensure that the branch The working stability of the load on the road 400.

The line fault removal device 10 includes a current generating device 100, the current generating device 100 is electrically connected to the DC bus 300, and is used for generating a fault maintenance current, the strength of the fault maintenance current is not less than that of each branch circuit 400 is the strength of the short-circuit current to provide the faulty branch 400 with an operating current. The beneficial effects of the line fault removal device 10 have been described in the above embodiments, and are not repeated in this embodiment.

Referring to FIG. 7 , in one embodiment, the converter 420 includes: a converter body 421 and a protector 422 .

The converter body 421 refers to converting the alternating current on the DC bus 300 into the working current required by the load on the branch 400 to ensure the working stability of the load on the branch 400 . The converter body 421 can realize four-quadrant operation without intermediate DC energy storage links, has excellent input current waveform and output voltage waveform, freely controllable power factor, and high flexibility. This embodiment does not make any restrictions on the specific type and model of the converter body 421, which can be selected according to the actual situation, and only needs to meet the requirements that the alternating current on the DC bus 300 can be converted into the branch 400. The function of the working current required by the load is sufficient.

One end of the protector 422 is electrically connected to the circuit breaker 410 , and the other end is electrically connected to the converter body 421 , and the protector 422 is used for when the current flowing through the converter body 421 exceeds a preset threshold At this time, the inverter body 421 is controlled to stop working. The protector 422 may be a fuse, a circuit breaker, etc., and automatically stops the operation of the converter body 421 when the current of the branch 400 exceeds a preset threshold. The type and model of the protector 422 are not arbitrarily limited in this embodiment, and can be selected according to the actual situation. It only needs to satisfy the requirement that the current flowing through the converter body 421 can be controlled when the current flowing through the converter body 421 exceeds a preset threshold. It is sufficient that the inverter main body 421 stops working.

Referring to FIG. 8 , in one embodiment, the protector 422 includes: a current detection component 4221 and a control component 4222 .

The current detection component 4221 is electrically connected to the inverter body 421 for detecting the current flowing through the inverter body 421 . The current detection component 4221 may be an ammeter, which is connected in series in the branch circuit 400 to detect the current in the branch circuit 400 , which is low in cost and easy to popularize. The current detection component 4221 can also be a current transformer, which is convenient for measuring large currents. The current detection component 4221 can also be other electronic devices with a current detection function. The current detection component 4221 is not specifically limited in this embodiment, and can be selected according to the actual situation. The function of the current of the inverter body 421 is sufficient.

The control component 4222 is signal-connected to the converter body 421 and the current detection component 4221 respectively, for controlling the converter body 421 to stop working when the current flowing through the converter body 421 exceeds a preset threshold , so as to protect the converter body 421 from being damaged by the short-circuit current. The preset threshold may be set according to actual conditions, which is not specifically limited in this embodiment. The controller can be a microprocessor, a control chip, a PLC chip, etc. This embodiment does not make any limitation on the control component 4222, which can be selected according to the actual situation, only limited to meet the requirements of the power flowing through the converter body 421. When the current exceeds a preset threshold, the function of controlling the inverter body 421 to stop working can be controlled.

Referring to FIG. 9 , in one embodiment, the DC system 30 further includes: a central control device 500 .

The central control device 500 is signal-connected to a plurality of the circuit breakers 410 respectively, and the central control device 500 is configured to determine whether a plurality of the branch circuits 400 are faulty according to the operation state of the circuit breakers 410 and whether a fault occurs or not. When the faulty branch 400 is determined. For example, if the circuit breaker 410 of a certain branch 400 operates, it can be determined that a short-circuit fault has occurred in the branch 400 , and other branches 400 do not operate, it can be determined that no short-circuit fault has occurred in the other branches 400 . The central control device 500 can complete the fault line selection through the action state of the circuit breaker 410, and the method is simple and easy to operate. The control device may be an electronic device with data processing functions such as a processor, a server, a mobile phone, a control chip, or the like, which is not specifically limited in this embodiment, as long as it satisfies the requirement that multiple determinations can be made according to the action state of the circuit breaker 410 . It is only necessary to determine whether the branch 400 is faulty and determine the function of the faulty branch 400 when the fault occurs.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as a limitation on the scope of the patent application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims (10)

1. The utility model provides a line fault remove device, is applied to direct current system, direct current system includes direct current bus and many branch roads, parallelly connected between many branch roads, and respectively with direct current bus electricity is connected, and every branch road is provided with the circuit breaker and the converter of establishing ties, its characterized in that, line fault remove device includes:

and the current generating equipment is electrically connected with the direct current bus and used for generating fault maintaining current, and the intensity of the fault maintaining current is not less than that of each branch circuit short-circuit current.

2. The line fault cut-off device of claim 1, wherein the current generating apparatus comprises:

an alternating current power supply for generating the fault-sustaining alternating current;

the input end of the rectifier is electrically connected with the alternating current power supply, the output end of the rectifier is electrically connected with the direct current bus, and the rectifier is used for converting the fault maintenance alternating current into the fault maintenance current.

3. The line fault clearing apparatus of claim 2, wherein said ac power source is a single phase ac power source.

4. The line fault cut-off device of claim 2, further comprising:

and the input end of the transformer is electrically connected with the alternating current power supply, and the output end of the transformer is electrically connected with the rectifier.

5. The line fault cut-off device of claim 2, wherein the rectifier comprises:

the anode of the first diode component is electrically connected with the alternating current power supply, and the cathode of the first diode component is electrically connected with the anode of the direct current bus;

and the cathode of the second diode component is electrically connected with the alternating current power supply, and the anode of the second diode component is electrically connected with the cathode of the direct current bus.

6. The line fault clearing apparatus of claim 5, wherein said ac power source is a three-phase ac power source;

the first diode assembly comprises three first diodes, anodes of the three first diodes are respectively electrically connected with the three phases of the alternating current power supply, and cathodes of the three first diodes are electrically connected with the anode of the direct current bus;

the second diode assembly comprises three second diodes, the anodes of the three second diodes are respectively connected with the three-phase electricity of the alternating current power supply, and the cathodes of the three second diodes are electrically connected with the cathode of the direct current bus.

7. A direct current system, comprising:

the direct current bus comprises a positive electrode wire and a negative electrode wire,

the multiple branches are connected in parallel and are respectively and electrically connected with the direct current bus, and each branch is provided with a circuit breaker and a converter which are connected in series;

the line fault clearing apparatus according to any one of claims 1 to 6, said current generating device being electrically connected to said DC bus for generating a fault holding current, said fault holding current having a magnitude not less than a magnitude of each of said branch short circuit currents.

8. The dc system of claim 7, wherein the converter comprises:

a converter body;

and one end of the protector is electrically connected with the circuit breaker, the other end of the protector is electrically connected with the converter body, and the protector is used for controlling the converter body to stop working when the current flowing through the converter body exceeds a preset threshold value.

9. The direct current system of claim 8, wherein the protector comprises:

the current detection assembly is electrically connected with the converter body and is used for detecting the current flowing through the converter body;

and the control assembly is respectively in signal connection with the converter body and the current detection assembly and is used for controlling the converter body to stop working when the current flowing through the converter body exceeds a preset threshold value.

10. The direct current system of claim 9, further comprising:

and the central control equipment is in signal connection with the circuit breakers respectively and is used for determining whether the branches have faults or not according to the action states of the circuit breakers and determining the fault branch when the branches have the faults.

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