Segmented modeling method of fuse for direct current networking system based on arc resistance characteristic

Abstract

The invention provides an arc resistance characteristic-based segmented modeling method of a fuse for a direct current networking system, and relates to the technical field of common direct current bus system design, and the method comprises the steps: calculating the real-time arc resistance data of the fuse according to the continuously collected short-circuit voltage and short-circuit current at the two sides of the fuse in a short-circuit test process, and forming an arc resistance curve; intercepting an arc resistance curve from the peak moment of the short-circuit current to the slope descending moment of the arc resistance curve to obtain an arc starting stage arc resistance curve, and intercepting an arc resistance curve from the slope descending moment to the moment when the short-circuit current is zero to obtain an arc burning stage arc resistance curve; respectively carrying out data fitting according to the arc starting stage arc resistance curve and the arcing stage arc resistance curve to obtain a sectional arc resistance curve equation; and taking the arc resistance curve equation as a control signal to build and obtain a fuse simulation model based on the controlled resistor. The method has the advantages that the arc resistance curve is divided into two sections, the corresponding arc resistance curve equation is designed, the simulation precision is higher, and the method can be better suitable for different working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of common DC bus system design, and in particular to a segmented modeling method for a fuse for a DC networking system based on arc resistance characteristics. Background Art

[0002] In today's industrial landscape, the rapid development of power electronics technology is driving the widespread adoption of complex electrical systems. As an advanced power configuration architecture, the common DC bus system has gained widespread adoption and promotion in industrial applications due to its exceptional flexibility and reliability.

[0003] Common DC bus systems typically connect multiple rectifiers and DC converters in parallel to the DC busbar. The rectifiers convert AC power to DC, providing a stable power input for the DC busbar. The DC converters transform and regulate the DC busbar voltage according to the demands of various loads. Short-circuit faults are a common and serious type of fault in common DC busbar systems. Once a short circuit occurs, a massive current rapidly flows into the system, causing severe damage to the busbar and other non-faulty branch components. To protect the system, fuses are widely used for short-circuit protection.

[0004] Fuses, as nonlinear overcurrent protection devices, operate based on the thermal effect of current. When current flows through a fuse, the melt generates heat. If the current exceeds the rated value, the melt temperature rapidly rises and melts, thereby interrupting the circuit. A fuse's arc resistance is a key indicator of its protective performance. Arc resistance refers to the electrical resistance exhibited when an arc is generated during the fuse's melting process. The internal quenching filler material significantly influences the arc resistance of a fuse. Different quenching filler materials have varying physical and chemical properties, such as melting point, thermal conductivity, and electrical conductivity. These properties influence the arc generation, development, and extinction process, thereby altering the magnitude and behavior of the arc resistance. For example, some filler materials can quickly absorb arc energy, extinguishing the arc quickly and reducing arc resistance; while other filler materials may prolong the arc duration and increase arc resistance. This complex variation in arc resistance makes accurate fuse modeling challenging.

[0005] Typically, the industry uses a variable resistor or a controlled source structure equivalent to a variable resistor circuit structure, and through repeated manual iterative approximation, creates a simulation model to simulate the arc resistance characteristics of a fuse under different currents. To facilitate iterative parameter optimization, this approach typically uses a single, relatively simple, low-order function as the control variable, which cannot accurately fit the external arc resistance characteristics of the fuse. In actual applications, parameters such as peak current and external voltage may differ significantly from actual measurements, and the modeling process is complex and tedious, which inconveniences the overall safety and reliability design of the system.

[0006] Therefore, there is an urgent need to improve the existing modeling methods. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a segmented modeling method for a fuse for a DC networking system based on arc resistance characteristics, comprising: step S1, performing a short-circuit test on the fuse, and continuously collecting the short-circuit voltage and short-circuit current on both sides of the fuse during the short-circuit test; step S2, calculating real-time arc resistance data of the fuse based on the short-circuit voltage and the short-circuit current, and constructing an arc resistance curve based on the real-time arc resistance data; step S3, intercepting the arc resistance curve between the peak moment of the short-circuit current and the moment when the slope of the arc resistance curve decreases to obtain an arc resistance curve in the arcing stage, and intercepting the arc resistance curve between the moment when the slope decreases to the moment when the short-circuit current is zero to obtain an arc resistance curve in the arcing stage; step S4, performing data fitting on the arc resistance curve in the arcing stage and the arc resistance curve in the arcing stage, respectively, to obtain a segmented arc resistance curve equation; step S5, using the arc resistance curve equation as a control signal to construct a fuse simulation model based on controlled resistance.

[0008] Preferably, in step S1, a short-circuit test is performed on the fuse through a pre-built short-circuit test platform for the fuse, and the short-circuit test platform includes: a DC voltage regulator source, wherein both ends of the DC voltage regulator source are respectively connected to one end of the contactor and one end of the supporting capacitor, and the other end of the contactor is connected to the other end of the supporting capacitor; a fuse branch, and is connected to both ends of the supporting capacitor, wherein the fuse branch includes a first circuit breaker and the fuse connected in series; an impedance device, wherein one end of the impedance device is connected to the other end of the supporting capacitor, and the other end of the impedance device is connected to one end of the fuse branch.

[0009] Preferably, the process of performing a short-circuit test on the fuse includes: step S11, disconnecting the first circuit breaker, and then closing the contactor so that the DC voltage stabilization source charges the supporting capacitor; step S12, closing the contactor after the supporting capacitor is charged, and then closing the first circuit breaker to perform a short-circuit test on the fuse, and using an oscilloscope to record the short-circuit voltage and the short-circuit current at both ends of the fuse.

[0010] Preferably, the short-circuit test platform also includes a discharge branch connected in parallel with the fuse branch, and the discharge branch also includes a second circuit breaker and a discharge resistor connected in series; after the short-circuit test is performed on the fuse, it also includes closing the second circuit breaker to release the residual capacitor voltage in the support capacitor through the discharge resistor.

[0011] Preferably, the arc resistance curve equation is expressed as follows:

[0012] in, represents the arc resistance value of the fuse at time t; Represents the arc resistance curve in the arc starting stage; Representing the arc resistance curve in the arcing stage; and is a constant, obtained by fitting the arc resistance curve in the arc starting stage; and is a constant, which is obtained by fitting the arc resistance curve in the arcing stage.

[0013] Preferably, in step S4, the LM least squares method is used to perform data fitting on the arc resistance curve in the arc starting stage and the arc resistance curve in the arc burning stage to obtain the corresponding constants.

[0014] Preferably, after executing step S5, it also includes: obtaining the simulated current of the fuse obtained by simulating the fuse simulation model and the Joule integral curve of the simulated current, and judging whether the difference between the simulated current and the Joule integral curve and the corresponding measured data is greater than the difference threshold: if not, the fuse simulation model is used as the segmented modeling result of the fuse; if so, the initial guess value of the LM least squares method is adjusted, and then returning to step S4.

[0015] Preferably, the initial guess value is obtained by preliminary estimation using a linear regression method.

[0016] Preferably, the fuse simulation model includes: an input module, connected to the input ends of the first current judgment module and the second current judgment module respectively, the output end of the first current judgment module is connected to the input end of the first multiplier, the output end of the second current judgment module is connected to the second multiplier, the integrator and the arcing moment judgment module in sequence, and the output end of the arcing moment judgment module is connected to the input end of the first multiplier through a NOT gate; a first switching switch, the input end of the first switching switch is connected to the output end of the input module and the arcing moment judgment module respectively, and the output end of the first switching switch is connected to the negative output port of the fuse through the rated resistance of the fuse; a second switching switch, the input end of the second switching switch is connected to the input module and the output end of the first multiplier respectively, the output end of the second switching switch is connected to the negative output port through a variable resistor, and the resistance control end of the variable resistor is connected to the arc resistance curve equation as a control signal; the output end of the NOT gate is the fuse working state output port, the output end of the input module is the simulation current output port, and the output end of the integrator is the Joule integral curve output port of the simulation current.

[0017] Preferably, the calculation formula of the real-time arc resistance data is as follows:

[0018] Wherein, z(t) represents the real-time arc resistance data at time t, represents the short-circuit voltage at time t, represents the short-circuit current at time t.

[0019] The above technical solution has the following advantages or beneficial effects: 1) According to the actual working conditions of the fuse, the peak moment of the short-circuit current is used as the starting moment of the arc resistance curve in the arcing stage, the moment when the slope of the arc resistance curve decreases is used as the ending moment of the arc resistance curve in the arcing stage and the starting moment of the arc resistance curve in the arcing stage, and the moment when the short-circuit current reaches zero is used as the ending moment of the arc resistance curve in the arcing stage. The arc resistance curve is divided into two sections and the corresponding arc resistance curve equation is designed. This has higher simulation accuracy and can be better applied to different working conditions. 2) Compared with the traditional arc resistance theoretical analysis scheme, the present invention does not need to analyze the specific filling material and internal structure, but only needs to perform waveform analysis on the measured real-time arc resistance data, which is more practical; 3) Compared with traditional solutions based on variable resistors or controlled source equivalent circuits, the present invention requires fewer iterations, and the resulting arc resistance curve equation can already reproduce the arc resistance characteristics of the fuse relatively well, usually without the need for simulation model adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 11 is a flow chart of a segmented modeling method for a fuse for a DC networking system based on arc resistance characteristics in a preferred embodiment of the present invention; Figure 2 Schematic diagram of the structure of a short-circuit test platform in a preferred embodiment of the present invention; Figure 3 1 is a flow chart of a process for performing a short-circuit test on a fuse in a preferred embodiment of the present invention; Figure 4 Schematic diagram of the structure of a fuse simulation model in a preferred embodiment of the present invention; Figure 5 A waveform comparison diagram between the simulated current output by the fuse simulation model and the measured short-circuit current in a preferred embodiment of the present invention; Figure 6 This is a waveform comparison diagram between the Joule integral curve output by the fuse simulation model and the integral value of the measured short-circuit current in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0022] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a segmented modeling method for a fuse for a DC networking system based on arc resistance characteristics is provided. Figure 1 As shown, it includes: step S1, performing a short-circuit test on the fuse, and continuously collecting the short-circuit voltage and short-circuit current on both sides of the fuse during the short-circuit test; step S2, calculating the real-time arc resistance data of the fuse according to the short-circuit voltage and the short-circuit current, and constructing an arc resistance curve according to the real-time arc resistance data; step S3, intercepting the arc resistance curve between the peak moment of the short-circuit current and the moment when the slope of the arc resistance curve decreases to obtain the arc resistance curve of the arc starting stage, and intercepting the arc resistance curve between the moment when the slope decreases to the moment when the short-circuit current is zero to obtain the arc resistance curve of the arc burning stage; step S4, performing data fitting according to the arc resistance curve of the arc starting stage and the arc resistance curve of the arc burning stage respectively, to obtain a segmented arc resistance curve equation; step S5, using the arc resistance curve equation as a control signal to construct a fuse simulation model based on controlled resistance.

[0023] Specifically, in this embodiment, the short-circuit voltage and short-circuit current during the short-circuit test are obtained by measuring the fuse, and then the real-time arc resistance data of the fuse is calculated. Then, the arc resistance curve formed by the real-time arc resistance data is analyzed to obtain the arc resistance curve equation that characterizes the change of the arc resistance of the fuse over time, and then use it as a control signal to build a fuse simulation model. The entire process does not require analysis of the specific filling material and internal structure inside the fuse, and is highly practical.

[0024] Furthermore, in order to realize the actual test of the fuse, it is necessary to build a short-circuit test platform for the fuse in advance to perform a short-circuit test on the fuse, such as Figure 2 As shown, the short-circuit test platform includes: a DC voltage regulator 100, the two ends of the DC voltage regulator 100 are respectively connected to one end of the contactor 200 and one end of the supporting capacitor 300, and the other end of the contactor 200 is connected to the other end of the supporting capacitor 300; a fuse branch, which is connected to the two ends of the supporting capacitor 300, and the fuse branch includes a first circuit breaker 400 and a fuse 500 connected in series; an impedance device 600, one end of the impedance device 600 is connected to the other end of the supporting capacitor 300, and the other end of the impedance device 600 is connected to one end of the fuse branch.

[0025] Specifically, in this embodiment, the above-mentioned DC voltage regulator 100 is preferably a programmable DC voltage regulator. On the one hand, it can accurately set the output voltage and current values, so that in the fuse short-circuit test, the voltage and current conditions under various actual working conditions can be accurately simulated according to different test requirements. For example, when testing the short-circuit characteristics of fuses of different specifications, the current size can be accurately adjusted from a small overload current to a very large short-circuit current to comprehensively evaluate the response time and fusing characteristics of the fuse at different current levels. On the other hand, its programmable characteristics enable testers to easily change the output parameters without the need for complex mechanical adjustments like traditional power supplies. The voltage and current values ​​can be modified in real time during the test, or the parameters can be gradually changed according to a preset program to achieve testing of the fuse under different dynamic conditions, such as simulating sudden changes in current.

[0026] In a preferred embodiment of the present invention, Figure 3 As shown, the process of performing a short-circuit test on a fuse includes: step S11, disconnecting the first circuit breaker, and then closing the contactor to allow the DC voltage regulator to charge the supporting capacitor; step S12, closing the contactor after the supporting capacitor is charged, and then closing the first circuit breaker to perform a short-circuit test on the fuse, and using an oscilloscope to record the short-circuit voltage and short-circuit current at both ends of the fuse.

[0027] In a preferred embodiment of the present invention, the short-circuit test platform also includes a discharge branch connected in parallel with the fuse branch, and the discharge branch also includes a second circuit breaker 700 and a discharge resistor 800 connected in series; after the fuse is short-circuited, it also includes closing the second circuit breaker to release the residual voltage of the capacitor in the supporting capacitor through the discharge resistor.

[0028] Specifically, in this embodiment, the entire process of performing a short-circuit test on a fuse based on the short-circuit test platform includes the following four stages: 1. Initial state setting stage Before performing a short-circuit test on a fuse, the first priority is to ensure that the entire test circuit is in a safe initial state. Specifically, carefully check and confirm that both the first circuit breaker 400 and the second circuit breaker 700 are in the disconnected state. This operation is crucial because when the two circuit breakers are in the disconnected state, it means that both the fuse branch and the discharge branch are not conducting, which can effectively avoid accidental current flow during the preparation stage and prevent damage to the test equipment, fuse samples, and operators. For example, if subsequent operations are performed without confirming the status of the circuit breaker, an arc may be generated due to accidental conduction of the circuit, causing a safety accident, and also interfering with the accuracy of the experimental data.

[0029] 2. Support capacitor charging stage After completing the initial state setup, the support capacitor charging phase begins. At this point, contactor 200 needs to be closed. Contactor 200 plays a key role in controlling the flow of current in the circuit. When closed, the DC voltage regulator 100 and the support capacitor 300 form a conductive loop, and the DC voltage regulator 100 begins charging the support capacitor 300.

[0030] Preferably, during the charging process, it is necessary to closely monitor the charging status to ensure that the charging process proceeds smoothly. Generally speaking, the charging completion can be determined by monitoring the voltage changes on both sides of the support capacitor 300. When the voltage reaches a preset value and remains stable for a period of time, the charging is considered complete.

[0031] 3. Short circuit test phase After charging is completed, the contactor 200 should be closed in time to cut off the connection between the DC voltage regulator 100 and the supporting capacitor 300 to avoid the DC voltage regulator 100 interfering with the test results. Then, the first circuit breaker 400 of the fuse branch is closed. At this time, the fuse 500 is connected to the circuit and the short-circuit test officially begins. During the short-circuit test, an oscilloscope is used to capture the voltage and current changes in the circuit in real time and display them in the form of waveforms. The specific data that needs to be recorded includes the short-circuit voltage v on both sides of the fuse 500 f (t) and short-circuit current i f (t), and the voltage i on both sides of the support capacitor 300 c(t) discrete waveform data. This data is crucial for analyzing the performance characteristics of a fuse under short-circuit conditions. For example, by analyzing the waveforms of the short-circuit voltage and current, we can understand information such as the fuse's opening time and the energy changes during the opening process. The voltage changes across the supporting capacitor 300 reflect the energy released by the capacitor during the short-circuit process.

[0032] 4. Experimental final stage After the short-circuit test is completed, the experiment cannot be ended immediately, and important finishing work needs to be carried out. At this time, it is necessary to close the second circuit breaker 700 of the discharge branch. After the second circuit breaker 700 is closed, the support capacitor 300 and the discharge resistor 800 form a conduction loop, and the residual voltage of the capacitor stored in the support capacitor 300 will be gradually released through the discharge resistor 800. This step is very necessary, because if there is residual voltage in the capacitor, it may cause an electric shock hazard to the operator during the next experiment or equipment maintenance, and may also affect the accuracy of the next experiment. During the discharge process, it is preferably possible to monitor the voltage on both sides of the support capacitor 300. When the voltage drops below the safe value, it can be considered that the discharge is complete and the entire experiment is finished.

[0033] After obtaining the measured short-circuit voltage and short-circuit current of the fuse based on the above short-circuit test process, the real-time arc resistance data of the fuse can be calculated. In a preferred embodiment of the present invention, the calculation formula of the real-time arc resistance data is as follows:

[0034] Among them, z(t) represents the real-time arc resistance data at time t, represents the short-circuit voltage at time t, Represents the short-circuit current at time t.

[0035] It can be understood that the above-mentioned real-time arc resistance data is a series of discrete data of the arc resistance of the fuse changing with time. It is preferred to construct an arc resistance curve with time as the horizontal axis and the corresponding arc resistance value as the vertical axis. The arc resistance curve here includes the arc resistance data of the entire short-circuit test process.

[0036] Furthermore, three key moments were identified in the arc resistance curve, which served as the basis for subsequent stage division and equation construction. The three key moments are: 1) Peak moment of short-circuit current At the moment a short circuit occurs, the current rises rapidly and reaches a peak. This peak moment marks the maximum short-circuit current, marking the moment when the arc is formed and the physical conditions within the arc channel undergo drastic changes. By monitoring the short-circuit current curve and using numerical analysis methods (such as the derivative method, where the peak moment is the time when the current derivative with respect to time is zero), the peak moment can be accurately determined. This moment is a key characteristic of the arc initiation phase and reflects the dynamic characteristics of the current at the moment of short-circuit fault occurrence.

[0037] 2) When the slope of the arc resistance curve decreases The slope of the arc resistance curve reflects the rate of change of arc resistance over time. As the arc develops, the rate of change of arc resistance changes due to variations in temperature, pressure, particle concentration, and other factors within the arc channel. A significant decrease in the slope of the arc resistance curve indicates that the arc has entered a new phase. By taking the derivative of the arc resistance curve, we can generate a curve showing the rate of change of arc resistance over time. By analyzing the trend of this curve, we can determine the point at which the slope decreases. This point typically marks the end of the arc starting phase and the beginning of the arc burning phase.

[0038] 3) The moment when the short-circuit current is zero As the arc burns and energy is consumed, the short-circuit current gradually decreases until it reaches zero. The moment the short-circuit current reaches zero indicates that the arc has extinguished and the short-circuit fault has ended. Similarly, by monitoring the short-circuit current curve, when the current value approaches zero and remains near zero for a period of time, this moment is identified as the moment of zero short-circuit current. This moment marks the end of the arc development process and is crucial for analyzing the arc extinction characteristics and the power system recovery process.

[0039] After locating the above-mentioned key moments, the arc resistance curve can be divided into different stages according to these moments, and the arc resistance curves of the arc starting stage and the arc burning stage can be extracted respectively.

[0040] The arc resistance curve for the arc starting phase is obtained by taking the peak moment of the short-circuit current as the starting moment and the moment when the slope of the arc resistance curve decreases as the ending moment. The arc resistance curve for this period of time is intercepted from the complete arc resistance curve. The arc starting phase is the process from arc formation to initial stabilization. During this phase, the physical processes within the arc channel are very complex, including the evaporation of electrode materials, the ionization and recombination of gases, etc. The characteristics of the arc resistance curve during the arc starting phase reflect the energy accumulation and channel establishment process in the initial stage of the arc, and are of great value for studying the arc initiation mechanism and arc starting characteristics.

[0041] The arc resistance curve for the burning phase is obtained by intercepting the arc resistance curve during the period starting from the moment the arc slope decreases and ending at the moment the short-circuit current reaches zero. The burning phase is the process of the arc burning steadily and gradually extinguishing. During this phase, the arc energy is dissipated to the surrounding environment primarily through heat conduction, convection, and radiation. Changes in the arc resistance curve during the burning phase reflect the energy balance and physical state changes of the arc during the combustion process, which is important for analyzing the combustion characteristics and extinction conditions of the arc.

[0042] After separating the arc resistance curves of the arc starting stage and the arc burning stage, the corresponding arc resistance curve equation can be constructed according to the characteristics of each stage. In a preferred embodiment of the present invention, the arc resistance curve equation is expressed as follows:

[0043] in, Indicates the arc resistance of the fuse at time t; Indicates the arc resistance curve in the arc starting stage; Indicates the arc resistance curve during the arc burning stage; and is a constant, which is obtained by fitting the arc resistance curve in the arc starting stage; and is a constant and is obtained by fitting the arc resistance curve during the arcing stage.

[0044] Specifically, in this embodiment, the arc starting phase is the process of gradual arc formation. During this phase, changes in arc resistance are primarily influenced by factors such as the increase in arc length and changes in the electrode surface condition. These factors contribute to a relatively regular change in arc resistance, typically exhibiting a near-linear growth trend. Using a linear equation to describe arc resistance changes during the arc starting phase simplifies the model structure, reduces the number of parameters to be determined, and thus reduces computational complexity and improves efficiency.

[0045] The arcing stage is the process of the arc burning steadily and gradually extinguishing. The change in arc resistance is affected by a variety of complex factors such as energy loss, arc contraction, gas ionization and recombination, and exhibits highly nonlinear variation characteristics. The curve shape of the low-order equation is relatively simple and cannot flexibly adapt to the complex changes such as bends and turns that may appear in the arc resistance curve during the arcing stage. By introducing higher-order terms, the high-order equation increases the degree of freedom of the equation, which can better fit the various morphological characteristics of the curve and make the fitted curve closer to the measured curve. The high-order equation can be regarded as a mathematical abstraction and approximation of these complex physical processes. By introducing higher-order quantities to reflect the nonlinear coupling relationship between different physical factors, the variation pattern of the arc resistance during the arcing stage can be more accurately described.

[0046] In a preferred embodiment of the present invention, in step S4, the arc resistance curve in the arc starting stage and the arc resistance curve in the arc burning stage are respectively fitted with data using the LM least squares method to obtain corresponding constants.

[0047] Specifically, in this embodiment, the arc resistance curve in the arc starting stage is formed by the arc resistance values ​​corresponding to different time points in the arc starting stage obtained by actual measurement. An initial guess value can be obtained by preliminary analysis of each measured arc resistance value, and then the LM least squares method is used for iterative fitting based on the initial guess value to finally obtain the above-mentioned and The arc resistance curve fitting process for the arcing stage is the same and will not be repeated here. Establishing a segmented arc resistance characteristic curve equation based on the fitted coefficients can more accurately describe the change of arc resistance over time, providing a more reliable theoretical basis for arc-related research and the design and protection of power equipment.

[0048] In a preferred embodiment of the present invention, after executing step S5, it also includes: obtaining the simulated current of the fuse obtained by simulating the fuse simulation model and the Joule integral curve of the simulated current, and judging whether the difference between the simulated current and the Joule integral curve and the corresponding measured data is greater than the difference threshold: if not, the fuse simulation model is used as the segmented modeling result of the fuse; if so, the initial guess value of the LM least squares method is adjusted, and then returning to step S4.

[0049] In a preferred embodiment of the present invention, the initial guess value is obtained by preliminary estimation using a linear regression method.

[0050] In a preferred embodiment of the present invention, Figure 4 As shown, the fuse simulation model includes: an input module 1, which is connected to the input ends of the first current judgment module 2 and the second current judgment module 3 respectively, the output end of the first current judgment module 2 is connected to the input end of the first multiplier 4, the output end of the second current judgment module 3 is sequentially connected to the second multiplier 5, the integrator 6 and the arcing moment judgment module 7, the output end of the arcing moment judgment module 7 is connected to the input end of the first multiplier 4 through the NOT gate 8; a first switching switch 9, the input end of the first switching switch 9 is connected to the output end of the input module 1 and the arcing moment judgment module 7 respectively, and the first switching switch The output end of 9 is connected to the negative output port of the fuse through the fuse rated resistor 10; the second switching switch 11, the input end of the second switching switch 11 is respectively connected to the output end of the input module 1 and the first multiplier 4, the output end of the second switching switch 11 is connected to the negative output port through the variable resistor 12, and the resistance control end of the variable resistor 12 is connected to the arc resistance curve equation as a control signal; the output end of the NOT gate 8 is the fuse working state output port, the output end of the input module 1 is the simulated current output port, and the output end of the integrator 6 is the Joule integral curve output port of the simulated current.

[0051] Specifically, in this embodiment, Figure 4 As shown, the input module 1 includes a positive input port Fuse1+ of the fuse, which is used to access the current signal of the external circuit as the current input source of the fuse simulation model. The positive input port Fuse1+ is preferably connected to the current sensing module, and the output of the current sensor module is transmitted through the absolute value module. Connect to the input end of the first current judgment module 2 and the second current judgment module 3.

[0052] Among them, the first current judgment module 2 is a conditional operator, which is used to judge whether the current current exceeds the rated current of the fuse. The output of is connected to the conditional judgment port of the conditional operator, which is used to output 1 when the input current is greater than the set rated current value, otherwise the output is 0.

[0053] The second current judgment module 3 is also a conditional operator, which is used to judge whether the current exceeds the rated current of the fuse. The output is connected to the condition judgment port of the conditional operator and the first output port, and is used to output the absolute value of the input current, that is, a high-level signal, when the input current is greater than the set rated current value, otherwise the output is 0.

[0054] During the normal operation phase of the fuse: the input current is not greater than the rated current, the outputs of the first current judgment module 2 and the second current judgment module 3 are both 0, so that the output of the first multiplier 4 is 0, that is, the second switching switch 11 (i.e., the arcing branch switch) is in the open state, and the first switching switch 9 (i.e., the rated resistance branch) is in the closed state. At this time, the current mainly passes through the rated resistance branch, that is, the current input from Fuse1+ passes through the branch where the first switching switch 9 is located, and then output from Fuse1-.

[0055] The rated fuse resistance 10 represents the fuse's resistance under normal operating conditions. In the simulation model, this resistor is connected in series with the circuit. When the first switching switch 9 is closed, it blocks the current. Its resistance is set according to the actual fuse specifications to accurately simulate the fuse's resistance effect on the circuit.

[0056] At this time, since the conditions for arcing and melting are not met, the arc resistance is in a normal state (which can be understood as the initial fixed resistance value, reflected by the rated resistance of the fuse), the fuse will not melt, and the current will continue to be conducted stably.

[0057] In the overcurrent and heat accumulation stage of the fuse: When the input current exceeds the rated current, the outputs of the first current judgment module 2 and the second current judgment module 3 are both high-level signals. The integrator 6 (1 / s) starts to integrate the current and calculates the current square time (i 2 t) value. As the current continues to flow, the integral value continues to increase. However, the first switching switch 9 (i.e., the rated resistance branch) remains closed, and the second switching switch 11 (i.e., the arcing branch switch) remains open, so the current continues to flow through the rated resistance branch.

[0058] At this time, the arc resistance has no obvious change temporarily, but as i 2 As the t value increases, the heat accumulation inside the fuse gradually increases, preparing for the subsequent possible melting. At this time, the fuse is still in the conducting state, but it is already in the overcurrent warning stage.

[0059] Arc starting stage: When the output value of integrator 6 (i 2 When the current (t value) exceeds the threshold set by the arcing moment judgment module 7, it means that the heat accumulation of the current has reached a level that may cause arcing. The arcing moment judgment module 7 outputs a low-level signal, which is inverted by the NOT gate and outputs a high-level signal. The second switching switch 11 (i.e., the arcing branch switch) closes, turning on the arcing branch, and the current begins to flow partially or completely through the arcing branch. In the fuse simulation model, the arcing branch simulates the current path when an arc is generated. After the switch is closed, current can flow through this branch, thereby changing the current distribution and electrical characteristics of the entire circuit to simulate the actual arcing situation of a fuse.

[0060] At this point, as the arcing branch conducts, arc resistance begins to take effect. The magnitude of arc resistance varies with current, voltage, and other conditions after arcing. Generally, arc resistance undergoes a dynamic change after arcing, initially being small and then changing as the arc develops. While the fuse may not yet have completely blown, the electrical characteristics of the circuit have already changed due to arcing.

[0061] Fusing stage: As the current continues to over-flow and heat accumulates, when i 2 The t value reaches the rated fuse i 2 When the t value is reached, the first switching switch 9 (ie, the rated resistance branch) is disconnected, cutting off the rated resistance branch, and the current can no longer pass through the normal path.

[0062] At this point, the fuse has completed its melting action and the circuit is disconnected. The arc resistance may change significantly at the moment of melting. For example, after the arc is extinguished, the arc resistance becomes infinite (under ideal circumstances), thus realizing the fuse's protective function for the circuit, preventing the current from continuing to flow and protecting other devices in the circuit from damage caused by overcurrent.

[0063] The fuse simulation model has three model output ports: a fuse operating status output port, derived from the output of NOT gate 8, which outputs the fuse operating status, i.e., the current operating state of the fuse. For example, it can output signals indicating different states, such as normal operation, arcing, and blown. This allows external systems to promptly understand the operating status of the fuse and take appropriate measures based on the different states, such as disconnecting the circuit or issuing an alarm signal when the fuse blows.

[0064] The simulated current output port, derived from the output of Input Module 1, corresponds to the current flowing through the output fuse, that is, the current value input to the fuse simulation model from Fuse1+. This output allows users to monitor the actual current in the fuse in real time and understand the current flow inside the fuse, which is important for analyzing circuit overcurrent protection.

[0065] The Joule integral curve output port is derived from the output of the integrator 6 and corresponds to the output fuse i 2 t (current square time) value. This value is obtained by integrating the current with an integrator and reflects the heat accumulation of the fuse during the power-on process. It is one of the key parameters to determine whether the fuse will blow. Users can predict the working status and life of the fuse by monitoring this value. For example, when i 2 The t value reaches the rated fuse i 2 When the t value is reached, the fuse will blow

[0066] As a preferred implementation, taking a certain fuse as an example, the data fitting results are shown below:

[0067] It is used as the control signal of the fuse simulation model to simulate the fuse's simulated current i(t) and its Joule integral curve i 2 t(t), where the waveform of the simulated current i(t) is as follows Figure 5 As shown by the smooth curve in the figure, the corresponding measured short-circuit current waveform is as follows Figure 5 The zigzag curve in the middle shows the Joule integral curve i 2 The waveform of t(t) and the corresponding measured data are as follows Figure 6 It can be seen that the difference between the simulation data and the measured data is small, that is, the fuse simulation model built by the segmented modeling method of the present invention has a higher accuracy.

[0068] The specific data comparison is shown in the following table: Table 1 Comparison of simulation and measured results

[0069] As can be seen from Table 1 above, the fuse simulation model built using this solution has high accuracy, can better simulate the actual working conditions of the fuse, and provide a corresponding reference for the selective protection of the common DC model system.

[0070] In summary, the fuse model established by the present invention cooperates with the external circuit configuration in which the fuse is located to jointly simulate the transient process of fuse blowing. The fuse model has good adjustability. After the actual test of the fuse blowing process, the parameters of the model are adjusted using the measured short-circuit current, voltage waveform and other data to obtain an accurate fuse model, which better simulates the details of the fuse blowing process and can achieve high simulation accuracy. It has guiding significance for the protection design and protection selectivity verification of the common DC bus system distribution. Compared with previous fuse modeling and simulation methods, the method of the present invention is closely integrated with the protection characteristics of the common DC bus distribution system, does not require the use of a complex arc resistance model, and has better engineering feasibility.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A segmented modeling method for a fuse for a DC networking system based on arc resistance characteristics, characterized in that: include: Step S1, performing a short-circuit test on the fuse, and continuously collecting the short-circuit voltage and short-circuit current on both sides of the fuse during the short-circuit test; Step S2, calculating the real-time arc resistance data of the fuse according to the short-circuit voltage and the short-circuit current, and constructing an arc resistance curve according to the real-time arc resistance data; Step S3, intercepting the arc resistance curve between the peak moment of the short-circuit current and the slope decreasing moment of the arc resistance curve to obtain the arc resistance curve of the arc starting stage, and intercepting the arc resistance curve between the slope decreasing moment and the moment when the short-circuit current is zero to obtain the arc resistance curve of the arc burning stage; Step S4, performing data fitting according to the arc resistance curve of the arc starting stage and the arc resistance curve of the arc burning stage respectively, to obtain a segmented arc resistance curve equation; Step S5, using the arc resistance curve equation as a control signal to construct a fuse simulation model based on controlled resistance.

2. The segmented modeling method according to claim 1, characterized in that: In the step S1, a short-circuit test is performed on the fuse through a pre-built short-circuit test platform for the fuse, and the short-circuit test platform includes: a DC voltage regulator source, wherein the two ends of the DC voltage regulator source are respectively connected to one end of the contactor and one end of the supporting capacitor, and the other end of the contactor is connected to the other end of the supporting capacitor; a fuse branch, and is connected to the two ends of the supporting capacitor, and the fuse branch includes a first circuit breaker and the fuse connected in series; an impedance device, wherein one end of the impedance device is connected to the other end of the supporting capacitor, and the other end of the impedance device is connected to one end of the fuse branch.

3. The segmented modeling method according to claim 2, characterized in that: The process of performing a short-circuit test on the fuse includes: step S11, disconnecting the first circuit breaker, and then closing the contactor so that the DC voltage stabilization source charges the supporting capacitor; step S12, closing the contactor after the supporting capacitor is charged, and then closing the first circuit breaker to perform a short-circuit test on the fuse, and using an oscilloscope to record the short-circuit voltage and the short-circuit current at both ends of the fuse.

4. The segmented modeling method according to claim 2, characterized in that: The short-circuit test platform also includes a discharge branch connected in parallel with the fuse branch, and the discharge branch also includes a second circuit breaker and a discharge resistor connected in series; after the short-circuit test is performed on the fuse, it also includes closing the second circuit breaker to release the residual capacitor voltage in the support capacitor through the discharge resistor.

5. The segmented modeling method according to claim 1, characterized in that: The arc resistance curve equation is expressed as follows: ； in, represents the arc resistance value of the fuse at time t; Represents the arc resistance curve in the arc starting stage; Representing the arc resistance curve in the arcing stage; and is a constant, obtained by fitting the arc resistance curve in the arc starting stage; and is a constant, which is obtained by fitting the arc resistance curve in the arcing stage.

6. The segmented modeling method according to claim 5, characterized in that: In the step S4, the LM least square method is used to perform data fitting on the arc resistance curve in the arc starting stage and the arc resistance curve in the arc burning stage to obtain the corresponding constants.

7. The segmented modeling method according to claim 6, characterized in that: After executing step S5, it also includes: obtaining the simulated current of the fuse obtained by simulating the fuse simulation model and the Joule integral curve of the simulated current, and judging whether the difference between the simulated current and the Joule integral curve and the corresponding measured data is greater than the difference threshold: if not, the fuse simulation model is used as the segmented modeling result of the fuse; if so, the initial guess value of the LM least squares method is adjusted, and then returning to step S4.

8. The segmented modeling method according to claim 7, characterized in that: The initial guess value is obtained by preliminary estimation using a linear regression method.

9. The segmented modeling method according to claim 1, characterized in that: The fuse simulation model includes: an input module, connected to the input ends of a first current judgment module and a second current judgment module, respectively; the output end of the first current judgment module is connected to the input end of a first multiplier; the output end of the second current judgment module is connected to the second multiplier, an integrator, and an arcing moment judgment module in sequence; the output end of the arcing moment judgment module is connected to the input end of the first multiplier through a NOT gate; a first switching switch, wherein the input end of the first switching switch is connected to the output end of the input module and the arcing moment judgment module, respectively; the output end of the first switching switch is connected to the negative output port of the fuse through the rated resistance of the fuse; a second switching switch, wherein the input end of the second switching switch is connected to the input module and the output end of the first multiplier, respectively; the output end of the second switching switch is connected to the negative output port through a variable resistor; the resistance control end of the variable resistor is connected to the arc resistance curve equation as a control signal; the output end of the NOT gate is the fuse working state output port, the output end of the input module is the simulation current output port, and the output end of the integrator is the Joule integral curve output port of the simulation current.

10. The segmented modeling method according to claim 1, characterized in that: The calculation formula of the real-time arc resistance data is as follows: ； Wherein, z(t) represents the real-time arc resistance data at time t, represents the short-circuit voltage at time t, represents the short-circuit current at time t.

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