Direct-current power distribution network fault current limiter and current limiting method

Abstract

The invention belongs to the field of power distribution, and relates to a DC power distribution network fault current limiter and a current limiting method, and the DC power distribution network fault current limiter comprises a current limiting resistor, a bypass switch and a control system. The current-limiting resistor is connected in parallel with the bypass switch; when the main loop is normal, the control system controls the bypass switch to be in a closed state and is used for bypassing the current-limiting resistor; and when the main loop is over-current, the control system controls the bypass switch to be in an off state, and the current-limiting resistor is connected to the main loop according to a resistance value R calculated by the control system. The simplified design of the primary system of the DC power distribution network fault current limiter not only reduces the manufacturing cost, but also simplifies the installation and maintenance process, improves the reliability and economical efficiency of the equipment, and is beneficial to wide popularization and application of the equipment. The application of closed-loop tracking control of the control system enables the current limiter to quickly respond when a fault occurs, effectively limits the diffusion of fault current, and protects sensitive equipment in a power grid from being damaged.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of power distribution, and relates to a DC power distribution network fault current limiter and a current limiting method. BACKGROUND

[0002] With the rapid development of modern power systems, DC power distribution networks have been widely used in the field of energy transmission and distribution due to their high efficiency and stability. However, DC power distribution networks may encounter various faults during operation, such as short circuits, overcurrents, etc. If these faults are not handled in a timely manner, they may cause damage to power equipment and even trigger large-scale power outages. Therefore, it is particularly important to develop a fault current limiter that can effectively limit fault currents and protect the safety of the power distribution network.

[0003] Traditional current limiters have long response times and limited current limiting effects, making it difficult to meet the needs of modern power systems for fast and accurate control. The DC power distribution network fault current limiter proposed in the application achieves fast response and effective limitation of fault currents through precise control strategies and primary system design, improving the safety and reliability of the DC power distribution network. SUMMARY

[0004] The purpose of the application is to solve the problems in the prior art and provide a DC power distribution network fault current limiter and a current limiting method. To achieve the above-mentioned application purposes, the application adopts the following technical solutions: A DC power distribution network fault current limiter, comprising a current limiting resistor, a bypass switch and a control system; the current limiting resistor and the bypass switch are connected in parallel; When the main circuit is normal, the control system controls the bypass switch to be in a closed state for bypassing the current limiting resistor; when the main circuit is overcurrent, the control system controls the bypass switch to be in an open state, and the current limiting resistor is connected to the main circuit according to the resistance value R calculated by the control system.

[0005] Preferably, the control system comprises an acquisition module, a parameter setting module, an adjustment module and an output control module; the acquisition module is connected to the current limiting resistor, the acquisition module and the parameter setting module are respectively connected to the adjustment module, and the output control module is respectively connected to the adjustment module, the current limiting resistor and the bypass switch; The acquisition module is used to acquire the positive voltage Ui Pos and the negative voltage Ui Neg at the input side of the current limiting resistor, the positive voltage Uo Pos and the negative voltage Uo Neg at the output side of the current limiting resistor, and the effective value I r of the measured current of the current limiting resistor; The parameter setting module is used to set the rated current value I n of the current limiter, the overcurrent multiple k, and the zero drift threshold Iz , current default value I0 and resistance default value R0, upper and lower limits k of overcurrent multiple max and k min , upper and lower limits R of resistance value of current limiting resistor max and R min ; The adjusting module is configured to calculate the resistance value R of the current limiting resistor and generate the control word of the bypass switch according to the data collected by the collecting module and the parameters set by the parameter setting module. The output control module is configured to output the resistance value R of the current limiting resistor calculated by the adjusting module to the current limiting resistor and output the control word of the bypass switch generated to the bypass switch.

[0006] Preferably, the zero drift threshold I z is a minimum value for determining whether the circuit has current; the current default value I0 is a maximum value for locking the calculation of the later stage of the control system; and the resistance default value R0 is a minimum value for locking the adjustment of the current limiting resistor.

[0007] Preferably, the adjusting module is configured to calculate the resistance value R of the current limiting resistor and generate the control word of the bypass switch according to the data collected by the collecting module and the parameters set by the parameter setting module, specifically as follows: (1) If the measured current effective value I r of the current limiting resistor is less than the set zero drift threshold I z of the current, the current limiting resistor is locked, and the resistance value of the current limiting resistor is always the resistance default value R0; the generated control word of the bypass switch is always 1, the bypass switch is in a closed state, and the current limiting resistor is in a bypassed state. (2) If the measured current effective value I r of the current limiting resistor is greater than or equal to the set zero drift threshold I z of the current and the measured current effective value I r of the current limiting resistor is less than kI n , the adjustment of the current limiting resistor is unlocked, but the resistance value of the current limiting resistor is still the resistance default value R0; the generated control word of the bypass switch is always 1, the bypass switch is in a closed state, and the current limiting resistor is in a bypassed state. (3) If the measured current effective value I r of the current limiting resistor is greater than or equal to kI n , the generated control word of the bypass switch is 0, the bypass switch is in an open state, the current limiting resistor is connected to the main circuit, and the resistance value R of the current limiting resistor is calculated.

[0008] Preferably, when the overcurrent multiple k min <k<k max , the actual current limiting value is k*I n , and when k≤k min , the actual current limiting value is kmin *I n , when k max ≤k, the actual current limiting value is k max *I n .

[0009] Preferably, the resistance R of the current limiting resistor is calculated as follows: ; wherein, is the resistance of the current limiting resistor at the last time, is the current resistance based on the resistance of the current limiting resistor at the last time, is the resistance correction value of the current limiting resistor.

[0010] Preferably, when the flow direction of the measured current effective value I r of the current limiting resistor is positive, the resistance correction value of the current limiting resistor is calculated as follows: .

[0011] Preferably, when the flow direction of the measured current effective value I r of the current limiting resistor is negative, the resistance correction value of the current limiting resistor is calculated as follows: .

[0012] Preferably, if R min < <R max , the actual current limiting resistance value is , if ≤R min , the actual current limiting resistance value is R min , if R max ≤ , the actual current limiting resistance value is R max .

[0013] A current limiting method of a DC power distribution network fault current limiter, which uses the DC power distribution network fault current limiter, comprises the following steps: (1) The control system judges whether the main loop is in a normal state or an overcurrent state; (2) If the main loop is in the normal state, the control system controls the bypass switch to be closed, and the current limiting resistor is in a bypass state; (3) If the main loop is in the overcurrent state, the control system controls the bypass switch to be opened, and the resistance R of the current limiting resistor is calculated, and the current limiting resistor is connected to the main loop according to the calculated resistance R of the current limiting resistor.

[0014] Compared with the prior art, the present application has the following advantages: The primary system simplified design of the DC power distribution network fault current limiter of the application not only reduces the manufacturing cost, but also simplifies the installation and maintenance process, improves the reliability and economy of the equipment, and is conducive to the wide promotion and application of the equipment.

[0015] The application of closed-loop tracking control of the control system enables the limiter to respond quickly when a fault occurs, effectively limiting the spread of fault current, thereby protecting sensitive equipment in the power grid from damage.

[0016] In addition, the adjustability and setting of all parameters provide high autonomy for the operator, so that the limiter can be personalized according to the specific power grid conditions and requirements, optimizing the current limiting effect.

[0017] By adopting the innovative bidirectional current limiting function, the applicability and flexibility of the equipment are significantly improved. This design enables the limiter to adapt to various different power grid conditions and fault types, ensuring the stability and safety of the power grid in the face of complex and variable operating environment.

[0018] Overall, the fault current limiter of the application not only ensures the safe and stable operation of the DC power distribution network, but also provides an economic and efficient solution for power grid operators. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual proportions.

[0020] Fig. 1 The schematic diagram of the DC power distribution network fault current limiter of the application.

[0021] Fig. 2 The specific schematic diagram of the DC power distribution network fault current limiter of the application.

[0022] Fig. 3 The simulation result diagram when the overcurrent multiple k is 1.5 and the fault resistance is 0.1Ω.

[0023] Fig. 4 The simulation result diagram when the overcurrent multiple k is 1.2 and the fault resistance is 0.1Ω.

[0024] Fig. 5 The simulation result diagram when the overcurrent multiple k is 1.5 and the fault resistance is 0.2Ω.

[0025] Fig. 6 The flowchart of the method of the application. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0028] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0029] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0030] Example 1: like Figs. 1-2 As shown, this embodiment provides a fault current limiter for a DC distribution network, including a current-limiting resistor, a bypass switch, and a control system; the current-limiting resistor is connected in parallel with the bypass switch; When the main circuit is normal, the control system keeps the bypass switch closed to bypass the current-limiting resistor; when the main circuit is overcurrent, the control system keeps the bypass switch open and the current-limiting resistor is connected to the main circuit according to the resistance value R calculated by the control system.

[0031] The control system includes a data acquisition module, a parameter setting module, an adjustment module, and an output control module. The data acquisition module is connected to a current-limiting resistor, the data acquisition module and the parameter setting module are respectively connected to the adjustment module, and the output control module is respectively connected to the adjustment module, the current-limiting resistor, and the bypass switch. The acquisition module is used to acquire the positive voltage Ui on the input side of the current-limiting resistor. Pos and negative voltage Ui Neg The positive voltage Uo on the output side of the current-limiting resistor Pos and negative voltage Uo Neg The measured effective value of the current I of the current-limiting resistor r; The parameter setting module is configured to set the rated current value I n , the overcurrent multiple k, the zero drift threshold I z of the current, the default value I0 of the current and the default value R0 of the resistance, the upper and lower limits k max and k min of the overcurrent multiple, and the upper and lower limits R max and R min of the resistance value of the current-limiting resistance. The adjustment module is configured to calculate the resistance value R of the current-limiting resistance and generate the control word of the bypass switch according to the data collected by the collection module and the parameters set by the parameter setting module. The output control module is configured to output the resistance value R of the current-limiting resistance calculated by the adjustment module to the current-limiting resistance, and output the control word of the bypass switch generated by the adjustment module to the bypass switch.

[0032] Specifically, the zero drift threshold I z of the current is a minimum value for determining whether the circuit has current; the default value I0 of the current is a maximum value for locking the calculation of the control system; and the default value R0 of the resistance is a minimum value for locking the adjustment of the current-limiting resistance.

[0033] The adjustment module calculates the resistance value R of the current-limiting resistance and generates the control word of the bypass switch according to the data collected by the collection module and the parameters set by the parameter setting module, specifically as follows: (1) If the measured current effective value I r of the current-limiting resistance is less than the set zero drift threshold I z of the current, the current-limiting resistance is locked, and the resistance value of the current-limiting resistance is always the default value R0 of the resistance; the generated control word of the bypass switch is always 1, the bypass switch is in a closed state, and the current-limiting resistance is in a bypassed state. (2) If the measured current effective value I r of the current-limiting resistance is greater than or equal to the set zero drift threshold I z of the current and the measured current effective value I r of the current-limiting resistance is less than kI n (i.e. I n multiplied by k), the adjustment of the current-limiting resistance is unlocked, but the resistance value of the current-limiting resistance is still the default value R0 of the resistance; the generated control word of the bypass switch is always 1, the bypass switch is in a closed state, and the current-limiting resistance is in a bypassed state. (3) If the measured current effective value I r of the current-limiting resistance is greater than or equal to kI n , the generated control word of the bypass switch is 0, the bypass switch is in an open state, the current-limiting resistance is connected to the main circuit, and the resistance value R of the current-limiting resistance is calculated. The calculation method of the resistance value R of the current-limiting resistance is as follows: ; wherein, is the resistance value of the current limiting resistor at the last time, is the current resistance value corrected on the basis of the resistance value of the current limiting resistor at the last time, is the resistance value correction value of the current limiting resistor.

[0034] The application has a bidirectional current limiting function, when the flow direction of the measured current effective value I r of the current limiting resistor is the positive direction, the calculation method of the resistance value correction value of the current limiting resistor is as follows: .

[0035] When the flow direction of the measured current effective value I r of the current limiting resistor is the reverse direction, the calculation method of the resistance value correction value of the current limiting resistor is as follows: .

[0036] The working principle of the DC power distribution network fault current limiter of the application is as follows: (1) initialization setting: Before the DC power distribution network fault current limiter is put into use, the user sets the following parameters through the parameter setting module according to the specific conditions and protection requirements of the power grid: the rated current value I n of the current limiter, the overcurrent multiple k, the current zero drift threshold I z , the current default value I0 and the resistance default value R0, the upper and lower limits of the overcurrent multiple k max and k min , and the upper and lower limits of the resistance value of the current limiting resistor R max and R min . These parameters will be used as the basic data of the control system and stored in the storage module of the control system.

[0037] In the case where the current limiting current is not set, the maximum output current of the DC power distribution network fault current limiter is the current default value I0, which realizes the basic protection of the subsequent circuit. The current default value I0 is usually large, and it is recommended to take 2 times of the rated operating current to prevent inaction.

[0038] The upper and lower limits of the overcurrent multiple k max and k min , the overcurrent multiple k and the rated current I n together determine the actual current limiting value. When k min <k<k max , the actual current limiting value is k*I n , when k min , the actual current limiting value is k min *I n , and when k max≤ k, the actual current limiting resistor value is k max I n .

[0039] the resistance correction value of the current limiting resistor and the current limiting resistor value of the last moment together determine the value of the current limiting resistor at the next moment If R min , If R max , the actual current limiting resistor value is R If R ≤ R min , the actual current limiting resistor value is R min If R max ≤ , the actual current limiting resistor value is R max .

[0040] (2) Operation during normal operation Under the normal working state of the DC power distribution network, the acquisition module continuously acquires the positive and negative voltages U iPos , U iNeg , U oPos , U oNeg at the input side and output side of the current limiting resistor, and the measured current effective value I r . The regulation module of the control system calculates and outputs the control word S of the bypass switch and the control word R of the current limiting resistor according to the acquired data and the set parameters. In the normal working state, the control word S of the bypass switch is set to 1, so that the bypass switch remains closed and the resistance value of the current limiting resistor remains at the default resistance value R0, thereby bypassing the current limiting resistor.

[0041] (3) Fault response and processing When the measured current effective value Ir exceeds the current zero drift threshold I z , the control system enters the fault response mode. If I r is less than kI n (i.e. I n multiplied by k), the regulation module unlocks the current limiter resistance adjustment, but keeps the resistance value of the current limiting resistor at R0, and the control word S of the bypass switch remains at 1. If I r is greater than kI n , the regulation module starts the automatic adjustment mechanism of the current limiting resistor, and adjusts the R value in real time according to the fault intensity, and the adjustment formula is: ; ; If the current flow direction is reverse, the calculation formula of the correction value is adjusted accordingly to realize bidirectional current limiting. The calculation formula corresponding to is: .

[0042] (4) Troubleshooting and System Recovery After the fault current is effectively limited, the control system monitors the current value to return to a safe range. Once the fault is confirmed to be cleared, the DC distribution network fault current limiter automatically returns to normal operation, the control word S of the bypass switch remains at 1, and the resistance value R of the current limiting resistor returns to R0, awaiting the next fault detection.

[0043] For example, assuming the bus voltage is 0.75kV, the equivalent load resistance is 2Ω, and the rated current of the current limiter is I... n Set to 1.2kA, with the upper and lower limits of the current limiting factor set to 1.5 and 1.2 respectively, the upper and lower limits of the current limiting resistor set to 1Ω and 0.0075Ω respectively, the current limiting zero drift threshold set to 0.01A, the default value of the current limiting resistor set to 1Ω, and the fault duration set to 500ms.

[0044] The simulation results when the overcurrent factor k is 1.5 and the fault resistance is 0.1Ω are shown in the attached figure. Fig. 3 As shown.

[0045] The simulation results when the overcurrent factor k is 1.2 and the fault resistance is 0.1Ω are shown in the attached figure. Fig. 4 As shown.

[0046] The simulation results when the overcurrent factor k is 1.5 and the fault resistance is 0.2Ω are shown in the attached figure. Fig. 5 As shown.

[0047] Through the above embodiments, the DC distribution network fault current limiter of the present invention can effectively limit fault current under various fault conditions, protecting the safe and stable operation of the power grid. Its bidirectional current limiting function and flexible parameter settings enable the current limiter to adapt to different power grid environments and fault types, giving it high practical value and broad application prospects.

[0048] Example 2: This embodiment provides a current limiting method for a DC distribution network fault current limiter, which includes the following steps: (1) The control system determines whether the main circuit is in a normal state or an overcurrent state; wherein, the control system collects the positive voltage Ui on the input side of the current limiting resistor. Pos and negative voltage Ui Neg The positive voltage Uo on the output side of the current-limiting resistor Pos and negative voltage Uo Neg The measured effective value of the current I of the current-limiting resistor r Set the rated current value I n Overcurrent factor k, current zero drift threshold I z, current default value I0 and resistance default value R0, upper and lower limits k of overcurrent multiple max and k min , upper and lower limits R of resistance value of current limiting resistor max and R min ; according to the relationship between the measured current effective value I r of the current limiting resistor and kI n , it is judged whether overcurrent occurs, when the measured current effective value I r of the current limiting resistor is greater than or equal to the set current zero drift threshold I z and the measured current effective value I r of the current limiting resistor is less than kI n , it is judged as normal state, when the measured current effective value I r of the current limiting resistor is greater than or equal to kI n , it is judged as overcurrent state.

[0049] (2) If the main circuit is in normal state, the bypass switch control word generated by the control system is 1, the bypass switch is closed, and the current limiting resistor is in bypass state; (3) If the main circuit is in overcurrent state, the bypass switch control word generated by the control system is 0, the bypass switch is opened, and the resistance value R of the current limiting resistor is calculated, and the current limiting resistor is connected to the main circuit according to the calculated resistance value R of the current limiting resistor.

[0050] The calculation method of the resistance value R of the current limiting resistor is as follows: ; Wherein, is the resistance value of the current limiting resistor at the last moment, is the current resistance value corrected on the basis of the resistance value at the last moment, is the resistance value correction value of the current limiting resistor.

[0051] The present application has bidirectional current limiting function, when the flow direction of the measured current effective value I r of the current limiting resistor is positive direction, the calculation method of the resistance value correction value of the current limiting resistor is as follows: .

[0052] When the flow direction of the measured current effective value I r of the current limiting resistor is negative direction, the calculation method of the resistance value correction value of the current limiting resistor is as follows: .

[0053] Those skilled in the art can understand that the modules of the examples described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the components of the examples have been described in general terms in the foregoing description. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0054] In the embodiments provided by the present application, it should be understood that the division of modules is only a logical functional division, and actual implementation can have another division manner, for example, multiple modules can be combined into one module, one module can be split into multiple modules, or some features can be ignored, etc.

[0055] In addition, each functional module in each embodiment of the present application can be integrated in one processing module, or each module can exist physically independently, or two or more modules can be integrated in one module. The integrated module can be realized in the form of hardware or in the form of a software functional module.

[0056] When the integrated module is realized in the form of a software functional module and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various media that can store program codes.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A fault current limiter for DC distribution networks, characterized in that, It includes a current-limiting resistor, a bypass switch, and a control system; the current-limiting resistor is connected in parallel with the bypass switch; When the main circuit is normal, the control system keeps the bypass switch closed to bypass the current-limiting resistor; when the main circuit is overcurrent, the control system keeps the bypass switch open and the current-limiting resistor is connected to the main circuit according to the resistance value R calculated by the control system.

2. The DC distribution network fault current limiter according to claim 1, characterized in that, The control system includes a data acquisition module, a parameter setting module, an adjustment module, and an output control module; the data acquisition module is connected to a current-limiting resistor, the data acquisition module and the parameter setting module are respectively connected to the adjustment module, and the output control module is respectively connected to the adjustment module, the current-limiting resistor, and the bypass switch; The acquisition module is used to acquire the positive voltage Ui on the input side of the current-limiting resistor. Pos and negative voltage Ui Neg The positive voltage Uo on the output side of the current-limiting resistor Pos and negative voltage Uo Neg The measured effective value of the current I of the current-limiting resistor r ; The parameter setting module is used to set the rated current value I of the current limiter. n Overcurrent factor k, current zero drift threshold I z Default current value I0 and default resistance value R0, upper and lower limits of overcurrent factor k max and k min The upper and lower limits of the current-limiting resistor R max and R min ; The adjustment module is used to calculate the resistance value R of the current limiting resistor and generate the control word of the bypass switch based on the data collected by the acquisition module and the parameters set by the parameter setting module. The output control module is used to output the resistance value R of the current-limiting resistor calculated by the adjustment module to the current-limiting resistor, and to output the control word of the generated bypass switch to the bypass switch.

3. The DC distribution network fault current limiter according to claim 2, characterized in that, Zero drift threshold I of current z The minimum value is used to determine whether there is current in the circuit; the default current value I0 is the maximum value, used for subsequent calculations in the interlocking control system; the default resistance value R0 is the minimum value, used for adjusting the interlocking current limiting resistor.

4. The DC distribution network fault current limiter according to claim 2, characterized in that, The adjustment module is used to calculate the resistance value R of the current-limiting resistor and generate the control word for the bypass switch based on the data collected by the acquisition module and the parameters set by the parameter setting module, as follows: (1) If the measured effective value of the current limiting resistor I r The current is less than the set zero drift threshold I. z The current-limiting resistor is locked out, and its resistance value is always the default value R0. The control word of the generated bypass switch is always 1, the bypass switch is in the closed state, and the current-limiting resistor is in the bypassed state. (2) If the measured effective value of the current limiting resistor I r The zero-drift threshold I of the current is greater than or equal to the set threshold. z And the measured effective value I of the current-limiting resistor r Less than kI n Unlock the adjustment of the current limiting resistor, but the resistance value of the current limiting resistor is still the default value R0; the generated bypass switch control word is always 1, the bypass switch is in the closed state, and the current limiter resistor is in the bypassed state. (3) If the measured effective value of the current limiting resistor I r Greater than or equal to kI n The generated bypass switch control word is 0, the bypass switch is in the open state, the current limiting resistor is connected to the main circuit, and the resistance value R of the current limiting resistor is calculated.

5. The DC distribution network fault current limiter according to claim 4, characterized in that, When the overcurrent multiple k min <k<k max The actual current limiting value is k*I n When k≤k min The actual current limiting value is k. min *I n When k max ≤k, the actual current limiting value is k max *I n .

6. The DC distribution network fault current limiter according to claim 4, characterized in that, The resistance value R of the current-limiting resistor is calculated as follows: ； in, It is the resistance value of the current-limiting resistor at the previous moment. The current resistance value is a correction based on the resistance value of the current-limiting resistor at the previous moment. This is the correction value for the current-limiting resistor.

7. The DC distribution network fault current limiter according to claim 6, characterized in that, When the measured effective value of the current limiting resistor I r When the flow direction is positive, the resistance correction value of the current-limiting resistor is... The calculation method is as follows: 。 8. The DC distribution network fault current limiter according to claim 6, characterized in that, When the measured effective value of the current limiting resistor I r When the flow direction is reversed, the resistance correction value of the current-limiting resistor is... The calculation method is as follows: 。 9. The DC distribution network fault current limiter according to claim 6, characterized in that, If R min < <R max The actual current-limiting resistor value is ,if ≤R min The actual current-limiting resistor value is R. min If R max ≤ The actual current-limiting resistor value is R. max .

10. A current limiting method for a fault current limiter in a DC distribution network, characterized in that, The DC distribution network fault current limiter according to any one of claims 1-9 includes the following steps: (1) The control system determines whether the main circuit is in a normal state or an overcurrent state; (2) If the main circuit is in normal condition, the control system controls the bypass switch to close, and the current limiting resistor is in the bypass state; (3) If the main circuit is in an overcurrent state, the control system controls the bypass switch to open and calculates the resistance value R of the current limiting resistor. The current limiting resistor is connected to the main circuit according to the calculated resistance value R.

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