A method for overcurrent modeling in a power supply system and its terminal

Abstract

This invention discloses a method and terminal for overcurrent modeling of a power supply system. It establishes an equivalent circuit model of the DC bus transmission line during short-circuit transients using an R-C-L model to represent the DC network power transmission line. A fuse model is placed near the lithium-ion battery in the equivalent circuit model, and the fuse's melting process is divided into a pre-arc process and an arcing process. During the pre-arc process, the fuse's inductance is ignored, and it is equivalent to a variable resistor. Circuit equations for the pre-arc process are established, along with arcing conditions. During the arcing process, the arc initiation model is equivalent to a variable resistor in series with a voltage source. Dynamic circuit equations for the arcing process are established, along with fault judgment conditions and fuse melting conditions. Based on the equivalent circuit model and the fuse model, a system model of the power supply system is constructed. This invention establishes a more accurate system model, enabling more effective modeling and simulation.

Description

[0001] This case is a divisional application based on the invention patent filed on May 28, 2024, with application number 202410672825.1 and titled "A method for modeling overcurrent in a power supply system, a simulation method, and a terminal". Technical Field

[0002] This invention relates to the field of power simulation technology, and in particular to a method and terminal for modeling overcurrent in a power supply system. Background Technology

[0003] A large proportion of renewable energy generation needs to be connected to the grid via DC transmission, and DC power distribution is increasingly widely used in many fields. Compared to traditional AC distribution networks, DC distribution networks have characteristics of "low impedance and low inertia" in their power generation equipment, power consumption equipment, and transmission lines. When a short-circuit fault occurs, the current rises rapidly, threatening the safety of the facilities in the line. Especially when a DC distribution system contains energy storage batteries, its short-circuit discharge current response characteristics reach the millisecond level. Therefore, the protection of DC transmission lines has higher requirements in terms of speed, peak current, and time matching.

[0004] Figure 1 This is a typical low-voltage DC microgrid power supply topology. The vast majority of energy storage batteries are lithium-ion batteries. To achieve higher charging and discharging efficiency, lithium-ion batteries have very low DC resistance, and can reach peak current in milliseconds during an external short circuit, with the amplitude directly proportional to the battery capacity. In recent years, the single-cell capacity of lithium-ion batteries used for electrochemical energy storage has been continuously increasing, placing higher demands on the protection of the power supply system.

[0005] To limit peak short-circuit current, passive protection (circuit breakers, fuses, etc.) or active protection (power electronic converters) are typically used in conjunction with the power battery. Literature analysis on the short-circuit characteristics of low-voltage DC systems indicates that a battery-connected converter can limit the short-circuit current to a relatively small range. However, batteries require frequent charging and discharging in the system, and the converter's operating losses are taken into account. Especially in data center applications, the PUE (Power Usage Effectiveness) value will increase, reducing the economic efficiency. Passive protection using fuses connected in series in the line cannot achieve targeted protection when there is a mismatch between the device and the parameters of the source and line.

[0006] To address the current challenges, experimental or simulation methods can be used in engineering practice to design fuses that match their main parameters with protection requirements. This ensures protection against occasional faults such as short circuits and severe overloads, while also avoiding the need to use actual short-circuit tests to verify fuse selection and matching.

[0007] Currently, in the patent with publication number CN111859609B, titled "A Fuse Modeling and Simulation Method Based on MATLAB / SIMULINK," the source circuit uses an RLC circuit to simulate the internal structure of the source, which cannot fully reflect the characteristics of battery-type sources; it only uses I... 2 The t-counting module reflects the fuse's melting process but cannot fully reflect the characteristics of the electric arc; it does not involve the identification of power supply circuit parameters. In the patent CN111585270A, "A Simulation Method for Short-Circuit Protection of a Marine DC Grid-Connected System," although a simulation of the power supply circuit from the battery to the DC bus is established, it fails to analyze the fuse protection under conditions where the battery-type power supply directly supplies power to the bus load via a DC / DC converter. Furthermore, it does not provide the specific modeling principle of the fuse, nor the selection criteria for the short-circuit waveform and parameters.

[0008] Therefore, a more effective modeling and simulation method is needed. Summary of the Invention

[0009] The technical problem to be solved by this invention is to provide a method and terminal for modeling overcurrent in a power supply system, so as to achieve more effective modeling and simulation.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] A method for modeling overcurrent in a power supply system, characterized by comprising the following steps:

[0012] S1. Using the model containing RCL as the equivalent DC bus transmission line, establish the equivalent circuit model of the DC network power transmission line at the moment of short circuit transient.

[0013] Establishing an equivalent circuit model for the short-circuit transient of the DC network power transmission line includes: establishing an equivalent model of the battery system, establishing equivalent circuits for the short-circuit transient of each converter in the DC network, and establishing equivalent circuits for the short-circuit transient of the DC network power transmission line.

[0014] S2. In the equivalent circuit model, a fuse model is set near the lithium-ion battery, and the fuse breaking process is divided into the pre-arc process and the arcing process:

[0015] During the pre-arc process, the inductance of the fuse itself is ignored, and the fuse is equivalent to a variable resistor. The circuit equations for the pre-arc process are established, and the conditions for arc ignition are established.

[0016] During the arcing process, the arc initiation model is equivalent to a variable resistor series voltage source. The circuit dynamic equations of the arcing process are established, and the fault judgment conditions and fuse blowing conditions of the fuse are established.

[0017] S3. Based on the equivalent circuit model and the fuse model, a system model of the power supply system is constructed by combining them.

[0018] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows:

[0019] A power supply system overcurrent modeling terminal includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the power supply system overcurrent modeling method described above.

[0020] The beneficial effects of this invention are as follows: The power supply system overcurrent modeling method, simulation method, and terminal of this invention use a model containing RCL to represent the DC bus transmission line, and in the construction of the fuse model, the fusing process is divided into the pre-arc process and the arcing process, respectively establishing circuit equations, and designing the arcing conditions, fuse fault judgment conditions, and fuse fusing conditions, resulting in a more accurate system model of the power supply system, realizing more effective modeling and simulation. It is applicable to the short-circuit current simulation of circuits with fuse-type protection devices powered by lithium-ion batteries, providing a basis for the design of power distribution facilities, and can determine whether the selection of fuses meets the requirements. Attached Figure Description

[0021] Figure 1 This is a typical low-voltage DC microgrid power supply topology diagram as described in the background art of this invention;

[0022] Figure 2 This is an example diagram of an equivalent battery system model for a power supply system overcurrent modeling method according to an embodiment of the present invention;

[0023] Figure 3 This is an intermediate diagram illustrating the construction of the equivalent circuit of each converter in the DC network during the short-circuit transient moment, as part of a power supply system overcurrent modeling method according to an embodiment of the present invention.

[0024] Figure 4 This is an example diagram of the equivalent circuit of each converter in the DC network during the short-circuit transient moment, according to an embodiment of the power supply system overcurrent modeling method of the present invention.

[0025] Figure 5 This is an example diagram of the equivalent circuit during the short-circuit transient of a DC network power transmission line, which is part of an embodiment of the present invention for a power supply system overcurrent modeling method.

[0026] Figure 6 This is a schematic diagram of the fuse location in a power supply system overcurrent modeling method according to an embodiment of the present invention;

[0027] Figure 7 This is a system model block diagram of a power supply system according to an embodiment of the present invention, which is a method for modeling overcurrent in a power supply system.

[0028] Figure 8 This is a flowchart of an overcurrent simulation method for a power supply system according to an embodiment of the present invention;

[0029] Figure 9 In a power supply system overcurrent simulation method according to an embodiment of the present invention, the current I when a short circuit occurs at load feeder location F is obtained through simulation. F Waveform diagram;

[0030] Figure 10 The current I at position X of the battery feeder obtained in the simulation of an overcurrent simulation method for a power supply system according to an embodiment of the present invention is... X ;

[0031] Figure 11 This is a schematic diagram of the structure of a terminal according to an embodiment of the present invention;

[0032] Label Explanation:

[0033] 1. A terminal; 2. A processor; 3. A memory. Detailed Implementation

[0034] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0035] Please refer to Figures 1 to 7 A method for modeling overcurrent in a power supply system, comprising the following steps:

[0036] S1. Using the model containing RCL as the equivalent DC bus transmission line, establish the equivalent circuit model of the DC network power transmission line at the moment of short circuit transient.

[0037] S2. In the equivalent circuit model, a fuse model is set near the lithium-ion battery, and the fuse breaking process is divided into the pre-arc process and the arcing process:

[0038] During the pre-arc process, the inductance of the fuse itself is ignored, and the fuse is equivalent to a variable resistor. The circuit equations for the pre-arc process are established, and the conditions for arc ignition are established.

[0039] During the arcing process, the arc initiation model is equivalent to a variable resistor series voltage source. The circuit dynamic equations of the arcing process are established, and the fault judgment conditions and fuse blowing conditions of the fuse are established.

[0040] S3. Based on the equivalent circuit model and the fuse model, a system model of the power supply system is constructed by combining them.

[0041] As can be seen from the above description, the beneficial effects of the present invention are as follows: The present invention provides a power supply system overcurrent modeling method, which uses a model containing RCL to represent a DC bus transmission line, and divides the fusing process into the pre-arc process and the arcing process in the construction of the fuse model, establishes circuit equations for each process, and designs the arcing conditions, fuse fault judgment conditions, and fuse fusing conditions, thereby obtaining a more accurate system model of the power supply system, achieving more effective modeling and simulation. It is applicable to the short-circuit current simulation of circuits with fuse-type protection devices powered by lithium-ion batteries, provides a basis for the design of power distribution facilities, and can determine whether the selection of fuses meets the requirements.

[0042] Furthermore, the circuit equations for the pre-arc process are as follows:

[0043]

[0044] t∈(0,t a );

[0045] Among them, t a Indicates the moment of arc ignition, I represents the current flowing through the lithium-ion battery, fuse, and load, and R represents the current at which the arc ignition occurs. L R represents the load. f L represents a variable resistor. ip and L in R represents the line inductance. ip and R in U represents the line resistance. B This represents the output of the lithium battery equivalent model.

[0046] As described above, the arc-precession characteristic mainly reflects the fuse's ability to withstand overcurrent, and its circuit equation is constructed as shown above.

[0047] Furthermore, the arcing conditions are expressed as:

[0048] I>I Bmin and

[0049] Among them, I Bmin The minimum breaking current is A, and the arc current is I. 2 t, t a Indicates the moment of arc ignition.

[0050] As described above, the fuse maintains its resistance characteristics until the current I reaches the minimum breaking current. Once this current is reached, the arcing condition is determined, and the condition is expressed as shown above.

[0051] Furthermore, the circuit dynamic equation for the arcing process is expressed as:

[0052]

[0053] t∈(t a , t b );

[0054] Among them, t a Indicates the moment of arc ignition, t b At the moment of fuse failure, I represents the current flowing through the lithium-ion battery, fuse, and load, and R... L R represents the load. f R represents a variable resistor. C L represents the resistance at the short-circuit position. ip and L in R represents the line inductance. ip and R in U represents the line resistance. B U represents the output of the lithium battery equivalent model. f This represents the arc voltage.

[0055] As described above, after entering the arcing process, the fuse arcing model is equivalent to a variable resistor Rf connected in series with a voltage source Uf, where Uf is used to simulate the arc voltage. The circuit dynamic equations for the arcing process are shown above.

[0056] Furthermore, the fuse maintains the characteristics of a voltage source containing internal resistance, and has a fault judgment condition for the peak current flowing through it. The fault judgment condition is expressed as follows:

[0057] I Pmax and

[0058] Among them I Pmax B is the maximum breaking current, and I is the fuse current. 2 t, I represents the current flowing through the lithium-ion battery, fuse, and load. a Indicates the moment of arc ignition, t b This is the moment the circuit breaker is triggered.

[0059] As described above, during the arcing process, the fuse maintains the characteristics of a voltage source with internal resistance and has a fault judgment condition for the peak current flowing through it. When this judgment condition is reached, the model sets a fault signal, indicating that the fuse cannot withstand the expected short-circuit current. The fault judgment condition is shown above.

[0060] Furthermore, if the fuse blows when the arc is extinguished, then the fuse blowing condition is equivalent to the arc extinguishing condition:

[0061] U f <0 and

[0062] Where B is the circuit breaker I 2 t, U f The arc voltage is represented by I, the current flowing through the lithium-ion battery, fuse, and load is represented by t.​a Indicates the moment of arc ignition, t b This is the moment the circuit breaker is triggered.

[0063] As described above, the fuse tripping conditions are set as shown above.

[0064] Please refer to Figure 8 A power supply system overcurrent simulation method, based on the system model of the power supply system constructed by the power supply system overcurrent modeling method described above, includes the following steps:

[0065] S1. Obtain project parameters;

[0066] S2. Substitute the engineering parameters into the system model and run the simulation.

[0067] As can be seen from the above description, the beneficial effects of the present invention are as follows: The power supply system overcurrent simulation method of the present invention is based on the power supply system overcurrent modeling method described above. It uses a model containing RCL to represent the DC bus transmission line, and divides the fusing process into the pre-arc process and the arcing process in the construction of the fuse model. Circuit equations are established separately, and arcing conditions, fuse fault judgment conditions, and fuse fusing conditions are designed to obtain a more accurate system model of the power supply system, realize more effective modeling and simulation, and is applicable to the short-circuit current simulation of circuits with fuse-type protection devices powered by lithium-ion batteries. It provides a basis for the design of power distribution facilities and can determine whether the selection of fuses meets the requirements.

[0068] Furthermore, the engineering parameters include the output capacitors of each converter or inverter, the inductance of the DC bus, and the resistance of the DC bus.

[0069] As described above, the above engineering parameters are collected and substituted into the system model for simulation operation.

[0070] Furthermore, the resistance of the DC bus is calculated by collecting the voltage at the connection points of adjacent power feeders on the bus, and the calculation expression is:

[0071]

[0072] Where x1 and x2 represent the connection points of two adjacent power feeders on the bus.

[0073] As described above, the resistance of the DC bus is calculated by collecting the voltage at the connection points of adjacent power feeders on the bus.

[0074] Please refer to Figure 11A terminal includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the above-described power supply system overcurrent modeling method or the above-described power supply system overcurrent simulation method.

[0075] The present invention provides a power supply system overcurrent modeling method, simulation method, and terminal, applicable to short-circuit current simulation of circuits powered by lithium-ion batteries and containing fuse-type protection devices.

[0076] Please refer to Figures 1 to 7 Embodiment 1 of the present invention is as follows:

[0077] A method for modeling overcurrent in a power supply system, comprising the following steps:

[0078] S1. Using the model containing RCL as the equivalent DC bus transmission line, establish the equivalent circuit model of the DC network power transmission line at the moment of short circuit transient.

[0079] In this embodiment, the equivalent circuit model of the DC network power transmission line during the short-circuit transient is constructed according to the following steps:

[0080] (1) Use MATLAB / SIMULINK to build a simulation model of the battery system.

[0081] Obtain the parameter set R: {RB0, RB1, ..., RBn} related to DC resistance, and the parameter set C: {CB0, CB1, ..., CBn} related to AC capacitance, and establish an equivalent model of the battery system based on this. (Refer to...) Figure 2 The output UB of this battery equivalent model can fully reflect the battery's response characteristics to external stimuli.

[0082] (2) Use MATLAB / SIMULINK to build the equivalent circuit of each converter in the DC network during the short-circuit transient.

[0083] by Figure 1 The low-voltage DC microgrid power supply topology diagram shown is used as an example. When lithium-ion battery system A is connected to the DC bus, and other lithium-ion battery systems B, photovoltaic power generation units, etc., can be selectively connected to the DC bus, it simulates a DC microgrid system with direct battery connections. When analyzing the transient state of a DC bus short-circuit fault, since each converter or inverter has power electronic level overcurrent protection or electrical isolation at its connection point to the bus, the overcurrent from the input terminal to the bus terminal can be limited. Its output-side capacitor needs to be equivalently connected in parallel to the bus to discharge to the short-circuit location at the moment of the short circuit. Here, C1 to Cn are the output-side capacitors of each of the n units (excluding battery system A) connected to the bus, such as... Figure 3 As shown.

[0084] When C1 discharges to Cn, the capacitance is equivalent to that of an ideal capacitor in series with its internal resistance ESR, such as... Figure 4 As shown.

[0085] In engineering applications, the output capacitor parameters of converters or inverters are readily available.

[0086] (3) Use MATLAB / SIMULINK to build the equivalent circuit for the short-circuit transient moment of the DC network power transmission line.

[0087] The DC bus transmission line is equivalently represented using a model including RCL. Since the coupling capacitance on the positive and negative bus lines is very small compared to the converter output capacitance, it can be further established... Figure 5 The diagram shows a power transmission bus network model directly powered by a battery, including circuit R and line inductance L.

[0088] In practical microgrid applications, the load on the DC bus can be located anywhere between the transmission network and the converter or inverter. As an example, Figure 5 The load RL is located at the end of the transmission network, the simulation is powered only by battery, and the load is short-circuited at that location.

[0089] S2. In the equivalent circuit model, a fuse model is set near the lithium-ion battery, and the fuse breaking process is divided into the pre-arc process and the arcing process:

[0090] During the pre-arc process, the inductance of the fuse itself is ignored, and the fuse is equivalent to a variable resistor. The circuit equations for the pre-arc process are established, and the conditions for arc ignition are established.

[0091] The circuit equations for the pre-arc process are:

[0092]

[0093] t∈(0,t a );

[0094] Among them, t a Indicates the moment of arc ignition, I represents the current flowing through the lithium-ion battery, fuse, and load, and R represents the current at which the arc ignition occurs. L R represents the load. f L represents a variable resistor. ip and L in R represents the line inductance. ip and R in U represents the line resistance. B This represents the output of the lithium battery equivalent model;

[0095] The conditions for arc ignition are expressed as follows:

[0096] I>I Bmin and

[0097] Among them, I Bmin The minimum breaking current is A, and the arc current is I. 2 t, t a Indicates the moment of arc ignition.

[0098] In this embodiment, when the fuse is used to protect the lithium-ion battery and the bus line, it is installed in the line near the lithium-ion battery, as can be referred to... Figure 6 The fusing process of a fuse is divided into the pre-arc process and the arcing process. The pre-arc characteristics mainly reflect the fuse's ability to withstand overcurrent. Figure 6 Before a short circuit occurs at the load RL, the circuit is in a steady state. Since the lithium-ion battery is the only source of power to RL, the average current flowing into and out of each branch of capacitors C1, C2...Cn is zero. The current flowing through the lithium-ion battery, the fuse, and the load RL is all I. Ignoring the inductance of the fuse itself, the fuse is equivalent to a variable resistor Rf during the pre-arc process. The circuit equations for the pre-arc process are shown above.

[0099] Before the current I reaches the minimum breaking current, the fuse maintains its resistive characteristics. Once this current is reached, the arcing condition is determined, as shown above. Upon reaching this condition, the arcing process begins.

[0100] During the arcing process, the arc initiation model is equivalent to a variable resistor series voltage source. The circuit dynamic equations of the arcing process are established, and the fault judgment conditions and fuse blowing conditions of the fuse are established.

[0101] The circuit dynamic equation for the arcing process is expressed as:

[0102]

[0103] t∈(t a , t b );

[0104] Among them, t a Indicates the moment of arc ignition, t b At the moment of fuse failure, I represents the current flowing through the lithium-ion battery, fuse, and load, and R... L R represents the load. f R represents a variable resistor. C L represents the resistance at the short-circuit position. ip and L in R represents the line inductance. ip and R in U represents the line resistance. B U represents the output of the lithium battery equivalent model. f Indicates arc voltage;

[0105] The fuse maintains the characteristics of a voltage source with internal resistance and has a fault judgment condition for the peak current flowing through it. The fault judgment condition is expressed as follows:

[0106] I Pmax and

[0107] Among them I Pmax B is the maximum breaking current, and I is the fuse current. 2 t, I represents the current flowing through the lithium-ion battery, fuse, and load. a Indicates the moment of arc ignition, t b This is the moment the circuit breaker is triggered.

[0108] If the fuse blows when the electric arc is extinguished, then the fuse blowing condition is equivalent to the arc extinguishing condition:

[0109] U f <0 and

[0110] Where B is the circuit breaker I 2 t, U f The arc voltage is represented by I, the current flowing through the lithium-ion battery, fuse, and load is represented by t. a Indicates the moment of arc ignition, t b This is the moment the circuit breaker is triggered.

[0111] As described above, after entering the arcing process, the fuse arcing model is equivalent to a variable resistor Rf connected in series with a voltage source Uf, where Uf is used to simulate the arc voltage. The current I begins to rise at the instant of the short circuit, and the rate of rise is determined by the response characteristics of the lithium-ion battery's external voltage UB, the time constants of all L and R in the transmission line, and the short-circuit resistance RC. Since the battery's internal parameters constitute the source's own time constant and inherent response characteristics, the output UB has already been described in the established lithium-ion battery model. Therefore, the dynamic equations of the arcing process circuit are shown above.

[0112] During arcing, the fuse maintains the characteristics of a voltage source with internal resistance, and has fault judgment conditions for the peak current flowing through it, as shown above. When this judgment condition is met, the model sets a fault signal, indicating that the fuse cannot withstand the expected short-circuit current.

[0113] The fuse blows when the arc is extinguished. The arc extinguishing condition is shown above.

[0114] S3. Based on the equivalent circuit model and the fuse model, a system model of the power supply system is constructed by combining them.

[0115] In this embodiment, based on the equivalent circuit model and fuse model established above, the system model is combined into a form with...​ Figure 7 A block diagram of the functions in the middle.

[0116] Please refer to Figure 1 as well as Figures 8 to 10 Embodiment two of the present invention is as follows:

[0117] A power supply system overcurrent simulation method, based on the power supply system model constructed by the power supply system overcurrent modeling method described in Embodiment 1 above, includes the following steps:

[0118] S1. Obtain project parameters;

[0119] The engineering parameters include the output capacitor of each converter or inverter, the inductance of the DC bus, and the resistance of the DC bus.

[0120] The resistance of the DC bus is calculated by collecting the voltage at the connection points of adjacent power feeders on the bus, and the calculation expression is:

[0121]

[0122] Where x1 and x2 represent the connection points of two adjacent power feeders on the bus.

[0123] In this embodiment, after modeling using the above-described power supply system overcurrent modeling method, the values ​​of the bus line resistance parameters are obtained using an online detection method, and the values ​​of other parameters are obtained using other engineering methods. Specifically, the methods are as follows:

[0124] by Figure 1 Taking the actual DC microgrid power supply system shown as an example, point X is the connection point between the lithium-ion battery system and the bus, and points A to F are the connection points between the converter or inverter and the bus. Point F is the connection point between the bus and the load unit feeder (in this example, the feeder at point F is short-circuited).

[0125] The system control unit controls the lithium-ion battery system A to stably supply power to the DC load unit at point F through point X at maximum load, while keeping other converters or inverters in a powered-off state, but enabling voltage acquisition at their respective bus connection ports; it collects the bus voltage acquisition values ​​UX to UF from point X to point F, as well as the current I of branch F. F The bus line resistance between adjacent nodes can be obtained using the following expression:

[0126]

[0127] Where x1 and x2 represent arbitrary power feeder connection points of the bus.

[0128] The output capacitors C1 to Cn and ESRc1 to ESRcn of each converter or inverter can be obtained by checking the corresponding component datasheets of the product.

[0129] Since the DC bus is a low-resistance conductor, its inductance is mainly related to the conductor length. According to engineering experience, the inductance of a low-resistance conductor can be estimated as 0.9 to 1.1 μH / m.

[0130] S2. Substitute the engineering parameters into the system model and run the simulation.

[0131] Substituting all the acquired parameters into the model, the simulation yields the current I when a short circuit occurs at load feeder location F. F Waveform as Figure 9 As shown, the current I at battery feeder position X. X like Figure 10 As shown. Where I X The fuse is designed to protect the battery, DC bus, and feeder from position F to the short circuit point from overload, overheating, and other safety hazards, given the current flowing through it. Simulation shows that the fuse blows within approximately 5ms, achieving I... X The peak current is approximately 9kA, and an arc voltage U is generated across the fuse at the moment of fuse failure. f The voltage is approximately 2.6kV, and the short-circuit current at feeder F is approximately 36kA, with a duration of approximately 1ms.

[0132] Component selection verification. For the fuse F1 selected in the actual project, the main parameters are rated current IN of 300A and minimum breaking current I. Bmin It has an 8IN voltage of 2.4kA and a maximum arc voltage withstand capability U. f The maximum breaking current is 4kA. Pmax The peak short-circuit current withstand capability (Ikmax) is 50kA; the impulse voltage withstand capability of peripheral circuit devices connected to the fuse is 5kV; for the selected feeder W1 copper busbar, the peak short-circuit current withstand capability (Ikmax) is 50kA. This indicates that all major parameters meet the design requirements.

[0133] This simulation modeling and short-circuit verification method is applicable not only to the analysis of short circuits occurring at the end of the busbar but also to the analysis of any node on the busbar connected to the battery. The parameters involved can be automatically acquired through programming or implementation control of the system control unit. It establishes a simulation process of the electric arc from a mechanistic perspective, achieving high accuracy. This avoids the need for engineering verification through actual short circuits or multiple iterative parameter calibration methods, thus improving the safety of related design verification.

[0134] Please refer to Figure 11 Embodiment 3 of the present invention is as follows:

[0135] A terminal 1 includes a processor 2, a memory 3, and a computer program stored in the memory 3 and executable on the processor 2. When the processor 2 executes the computer program, it implements the steps in the power supply system overcurrent modeling method described in Embodiment 1 above, or the steps in the power supply system overcurrent simulation method described in Embodiment 2 above.

[0136] In summary, the present invention provides a power supply system overcurrent modeling method, simulation method, and terminal. It uses a model containing an RCL (Remote Current Channel) to represent the DC bus transmission line, and divides the fusing process into a pre-arc process and an arcing process in the fuse model construction. Circuit equations are established for each process, and arcing conditions, fuse fault judgment conditions, and fuse fusing conditions are designed to obtain a more accurate system model of the power supply system. This enables more effective modeling and simulation, and is applicable to short-circuit current simulation of circuits with lithium-ion battery power supply and fuse-type protection devices. It provides a basis for power distribution facility design and can determine whether the fuse selection meets the requirements.

[0137] This invention enables the use of effective testing or simulation methods in engineering design, ensuring that the main parameters of fuses are matched with protection requirements. This provides protection against occasional faults such as short circuits and severe overloads, while improving system efficiency and reducing energy consumption. It also avoids the need for actual short-circuit tests to verify fuse selection and matching. This method is applicable to short-circuit current simulation in circuits powered by lithium-ion batteries and incorporating fuse-type protection devices, providing a basis for power distribution facility design and determining whether fuse selection meets requirements.

[0138] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for modeling overcurrent in a power supply system, characterized in that, Including the following steps: S1. Using the model containing RCL as the equivalent DC bus transmission line, establish the equivalent circuit model of the DC network power transmission line at the moment of short circuit transient. Establishing an equivalent circuit model for the short-circuit transient of the DC network power transmission line includes: establishing an equivalent model of the battery system, establishing equivalent circuits for the short-circuit transient of each converter in the DC network, and establishing equivalent circuits for the short-circuit transient of the DC network power transmission line. S2. In the equivalent circuit model, a fuse model is set near the lithium-ion battery, and the fuse breaking process is divided into the pre-arc process and the arcing process: During the pre-arc process, the inductance of the fuse itself is ignored, and the fuse is equivalent to a variable resistor. The circuit equations for the pre-arc process are established, and the conditions for arc ignition are established. During the arcing process, the arc initiation model is equivalent to a variable resistor series voltage source. The circuit dynamic equations of the arcing process are established, and the fault judgment conditions and fuse blowing conditions of the fuse are established. S3. Based on the equivalent circuit model and the fuse model, construct a system model of the power supply system. The establishment of the equivalent model of the battery system is specifically as follows: Obtain and establish an equivalent model of the battery system based on the parameter sets related to DC resistance and AC capacitance; The circuit equations for the pre-arc process are: ； in, Indicates the moment of arc ignition; I represents the current flowing through the lithium-ion battery, fuse, and load. Indicates load, Indicates a variable resistor. and Indicates line inductance. and This represents the line resistance, and n represents the number of converters connected to the bus other than the battery system. This represents the output of the lithium battery equivalent model; The circuit dynamic equation for the arcing process is expressed as: ； ； in, Indicates the moment of arc ignition. At the moment of fuse failure, I represents the current flowing through the lithium-ion battery, the fuse, and the load. Indicates load, Indicates a variable resistor. Indicates the resistance at the short-circuit position. and Indicates line inductance. and Indicates the line resistance. This represents the output of the lithium battery equivalent model. This represents the arc voltage.

2. The overcurrent modeling method for a power supply system according to claim 1, characterized in that, The conditions for arc ignition are expressed as follows: and ; Where I represents the current flowing through the lithium-ion battery, fuse, and load. The minimum breaking current is given by A, where A is the arc advance current. , Indicates the moment of arc ignition.

3. The overcurrent modeling method for a power supply system according to claim 1, characterized in that, The fuse maintains the characteristics of a voltage source with internal resistance and has a fault judgment condition for the peak current flowing through it. The fault judgment condition is expressed as follows: and ; in, B is the maximum breaking current, and B is the fuse strength. I represents the current flowing through the lithium-ion battery, fuse, and load. Indicates the moment of arc ignition. This is the moment the circuit breaker is triggered.

4. The overcurrent modeling method for a power supply system according to claim 1, characterized in that, If the fuse blows when the electric arc is extinguished, then the fuse blowing condition is equivalent to the arc extinguishing condition: and ; Where B represents the circuit breaker. , This represents the arc voltage, and I represents the current flowing through the lithium-ion battery, fuse, and load. Indicates the moment of arc ignition. This is the moment the circuit breaker is triggered.

5. A power supply system overcurrent modeling terminal, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps in the power supply system overcurrent modeling method according to any one of claims 1-4.

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