Fault test system for DC circuit breakers and DC distribution networks

Abstract

The present application provides a fault test system and a DC distribution network for a DC circuit breaker, comprising a circuit end, a coupling interaction end, and a multi-physics field end; the circuit end is used to perform electromagnetic transient simulation on the DC circuit breaker through an electromagnetic transient simulation model to output a dynamic current value to the coupling interaction end; the coupling interaction end is used to convert the dynamic current value into a dynamic boundary condition and send the dynamic boundary condition to the multi-physics field end; the multi-physics field end is used to determine the physical parameter value based on the finite element model and dynamic boundary condition of multiple preset physical fields, and send the physical parameter value to the coupling interaction end; the coupling interaction end is used to update the current resistance parameter and admittance parameter of the arc according to the physical parameter value, and send the current resistance parameter and admittance parameter to the circuit end to indicate the next electromagnetic transient simulation. In this way, the connection between the multi-physics field end and the circuit end is established through the coupling interaction end, thereby improving the comprehensiveness of the fault test for the DC circuit breaker.

Description

Technical Field

[0001] The present application relates to the technical field of fault testing, and in particular to a fault testing system for a DC circuit breaker and a DC distribution network. Background Art

[0002] In today's power sector, with the rapid development of direct current (DC) transmission technology, high-voltage DC systems have become increasingly important in grid infrastructure construction due to their many advantages, such as low transmission losses over long distances and large transmission capacity, and have been widely used.

[0003] However, because fault current in DC systems lacks a natural zero-crossing point, the safety and stability of the entire power grid are directly impacted by the breaking capacity and response speed of the DC circuit breaker in HVDC systems. Traditional fault testing for DC circuit breakers simulates the breaking process based on initial parameters and offline data, resulting in poor fault testing effectiveness and accuracy, limiting its applicability. Summary of the Invention

[0004] This application proposes a fault testing system for DC circuit breakers, in order to achieve the connection between electromagnetic transient simulation and finite element simulation corresponding to the arc, establish a communication connection between the multi-physics field and the circuit in which the DC circuit breaker is located, and enable different types of simulations to work together to improve the comprehensiveness and accuracy of fault testing for DC circuit breakers.

[0005] An embodiment of the present application provides a fault testing system for a DC circuit breaker, comprising a circuit end, a coupling interaction end, and a multi-physics field end, wherein the circuit end is connected to the coupling interaction end, and the coupling interaction end is connected to the multi-physics field end;

[0006] The circuit end is used to perform the current electromagnetic transient simulation of the DC circuit breaker using a preset electromagnetic transient simulation model to output a dynamic current value to the coupling interaction end. The dynamic current value is the current value at the current moment. The electromagnetic transient simulation is used to simulate the operating state of the DC distribution network under a preset fault scenario;

[0007] A coupling interaction terminal, used to convert the dynamic current value into a dynamic boundary condition of the multi-physics terminal, and to send the dynamic boundary condition to the multi-physics terminal, where the dynamic boundary condition is used to indicate the constraint conditions of various physical quantities required by the multi-physics terminal in the current state;

[0008] The multi-physics terminal is used to determine the physical property parameter values ​​at the current moment based on the finite element model and dynamic boundary conditions of multiple preset physical fields. The physical property parameter values ​​at the current moment are used to simulate the arc behavior corresponding to the arc generated by the DC circuit breaker during the breaking process; and send the physical property parameter values ​​at the current moment to the coupling interaction terminal;

[0009] The coupling interaction end is also used to update the current resistance parameter and admittance parameter corresponding to the arc according to the physical parameter value corresponding to the arc at the current moment; and send the current resistance parameter and admittance parameter to the circuit end to indicate the next electromagnetic transient simulation.

[0010] In a possible embodiment, the coupling interaction terminal is used to send physical property parameters and initial boundary conditions in an initial state to the multi-physics field terminal before starting an online simulation operation for the DC circuit breaker. The initial boundary conditions are used to indicate constraint conditions of various physical quantities required by the multi-physics field terminal in the initial state.

[0011] The multi-physics end is used to construct a finite element model in the initial state based on the physical parameters and initial boundary conditions in the initial state to determine the initial simulation value; and send the initial simulation value to the coupling interaction end;

[0012] The coupling interaction end is also used to determine the initial resistance parameters and initial admittance parameters of the arc according to the initial simulation values;

[0013] The circuit end is used to perform electromagnetic transient simulation on the DC circuit breaker through the electromagnetic transient simulation model according to the initial resistance parameter and the initial admittance parameter, so as to output a dynamic current value after detecting a simulation start instruction.

[0014] In a possible embodiment, the coupling interaction end is further used to:

[0015] Before starting an online simulation operation for the DC circuit breaker, obtaining a preset total simulation time and a simulation step length, where the simulation step length is used to indicate the time required for the fault test system for the DC circuit breaker to complete a single online simulation operation; and

[0016] When performing an online simulation operation for a DC circuit breaker, if a dynamic current value sent by a circuit end is detected, a simulation step is superimposed once; and

[0017] When the total duration corresponding to the superimposed simulation step length is greater than or equal to the total simulation duration, the online simulation is determined to be finished, and data transmission between the circuit end and the multi-physics field end is stopped.

[0018] In one possible embodiment, when the DC circuit breaker is coupled to the DC distribution network, the DC circuit breaker includes a main current-carrying branch and a transfer branch, and the transfer branch is connected in parallel with the main current-carrying branch;

[0019] Before the DC circuit breaker is opened, the main current branch is in the conducting state and the transfer branch is in the disconnected state; and

[0020] When a fault occurs in the DC distribution network, the main current-carrying branch switches from a conducting state to an open state to generate an arc, and the transfer branch switches from an open state to a conducting state.

[0021] In one possible embodiment, when the DC circuit breaker is decoupled from the DC distribution network and connected to the electromagnetic transient simulation model, the equivalent circuit of the DC circuit breaker includes an arc resistor, a first equivalent inductor, a bidirectional solid-state switch module, and a second equivalent inductor. The arc resistor and the first equivalent inductor are connected in series to form a first series circuit, the bidirectional solid-state switch module and the second equivalent inductor are connected in series to form a second series circuit, the first series circuit and the second series circuit are connected in parallel, the first equivalent inductor is used to be equivalent to a main current-carrying branch of the DC circuit breaker coupled to the DC distribution network, and the second equivalent inductor is used to be equivalent to a transfer branch of the DC circuit breaker coupled to the DC distribution network. The arc resistance of the arc resistor is determined by a current resistance parameter sent by the coupling interaction end.

[0022] In a possible embodiment, the fault testing system for a DC circuit breaker further includes a server;

[0023] The server is used to send fault instructions to the coupled interaction terminal;

[0024] The coupling interaction end is also used to control the switching state of the bidirectional solid-state switch module to switch to the on state and adjust the arc resistance of the arc resistor to the current resistance parameter in response to the fault instruction when a fault instruction is detected.

[0025] In one possible embodiment, the electromagnetic transient simulation model is used to: after obtaining the updated initial resistance parameter or current resistance parameter sent by the circuit end, determine the first admittance corresponding to the first series circuit, the second admittance corresponding to the second series circuit, and the arc resistance at the current moment according to the updated initial resistance parameter or current resistance parameter; obtain the voltage value at both ends of the equivalent circuit of the DC circuit breaker, as well as the first current value corresponding to the first series circuit, the second current value corresponding to the second series circuit, and the switch resistance of the bidirectional solid-state switch module, the first current value is the Nouton equivalent current of the main current branch, and the second current value is the Nouton equivalent current of the transfer branch; perform electromagnetic transient simulation to determine the dynamic current value according to the arc resistance, switch resistance, first current value, second current value, and voltage value at the current moment.

[0026] In one possible embodiment, the coupling interaction end also includes a display device; the display device is used to display the result value calculated in each online simulation operation for the DC circuit breaker, and the result value includes at least one of the following: the dynamic current value corresponding to the online simulation operation, the physical parameter value at the current moment, and the current resistance parameter and admittance parameter corresponding to the arc.

[0027] In a possible embodiment, the preset physical field corresponding to the finite element model includes at least one of the following types of physical fields: electromagnetic field, temperature field, flow field, and stress field.

[0028] In an embodiment of the present application, a fault testing system for a DC circuit breaker includes a circuit terminal, a coupling interaction terminal, and a multi-physics terminal. The circuit terminal includes an electromagnetic transient simulation model and a DC circuit breaker, and the multi-physics terminal includes a finite element model. The coupling interaction terminal couples multi-physics finite element simulation with circuit electromagnetic transient simulation, providing the DC circuit breaker with real-time, dynamically changing boundary conditions and arc behavior, improving the accuracy of electromagnetic transient simulation and the flexibility of finite element simulation, enabling the DC circuit breaker to adapt to different operating conditions and enhancing the accuracy and comprehensiveness of fault testing for the DC circuit breaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 This is a structural diagram of a fault testing system for a DC circuit breaker provided in an embodiment of the present application;

[0031] Figure 2 This is a flowchart of a fault test provided by an embodiment of the present application;

[0032] Figure 3 This is a structural schematic diagram of an equivalent circuit of a DC circuit breaker breaking process provided by an embodiment of the present application;

[0033] Figure 4 This is a structural schematic diagram of an electromagnetic transient model of a DC circuit breaker breaking process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0036] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0037] In the embodiments of this application, "and / or" describes the relationship between associated objects and indicates that three relationships can exist. For example, "A and / or B" can represent the following three situations: A exists alone; A and B exist simultaneously; and B exists alone. A and B can be singular or plural.

[0038] In the embodiments of the present application, the symbol " / " can indicate that the preceding and following objects are in an "or" relationship. In addition, the symbol " / " can also represent a division sign, that is, performing a division operation. For example, A / B can mean A divided by B.

[0039] In the embodiments of the present application, "at least one item" or similar expressions refers to any combination of these items, including any combination of single items or plural items, and refers to one or more, and multiple refers to two or more. For example, at least one item (item) of a, b, or c can represent the following seven situations: a, b, c, a and b, a and c, b and c, a, b, and c. Among them, each of a, b, and c can be an element or a set containing one or more elements.

[0040] In the embodiments of this application, "equal to" can be used in conjunction with "greater than" and is applicable to the technical solution adopted when "greater than" is used, and can also be used in conjunction with "less than" and is applicable to the technical solution adopted when "less than" is used. When "equal to" is used in conjunction with "greater than", it should not be used in conjunction with "less than"; when "equal to" is used in conjunction with "less than", it should not be used in conjunction with "greater than".

[0041] Please refer to the following Figure 1 , Figure 1 This is a structural diagram of a fault testing system for a DC circuit breaker provided in an embodiment of the present application. Figure 1As shown, the connection relationship between the various physical devices in the fault testing system for DC circuit breaker is as follows: the fault testing system 100 for DC circuit breaker includes a circuit terminal 110, a coupling interaction terminal 120, and a multi-physics field terminal 130. The circuit terminal 110 also includes a DC circuit breaker 111. Among them, the circuit terminal 110 is used to perform electromagnetic transient simulation on the DC circuit breaker 111 through a preset electromagnetic transient simulation model to simulate the operating state of the DC distribution network under a preset fault scenario, thereby testing the breaking capacity and response speed of the DC circuit breaker. In order to improve the comprehensiveness and authenticity of the simulation, the multi-physics field terminal 130 is used to simulate the arc behavior generated by the DC circuit breaker 111 during the process of breaking due to a DC distribution network fault. The coupling interaction terminal 120 is used to transmit data between the circuit terminal 110 and the multi-physics terminal 130. This allows for real-time coupling of the arc's thermal, electromagnetic, and magnetic multi-physics fields with circuit parameters through the establishment of a mutual feedback relationship. This allows the simulation process to dynamically reflect the arc's state changes at different times and in different spaces, avoiding the initial boundary conditions from ignoring the dynamic changes in current and voltage under fault conditions, thereby improving the accuracy of the simulation results. Furthermore, based on online simulation, the DC circuit breaker fault testing system 100 can promptly capture the arc's changing process and its impact on the circuit, providing a more reliable basis for circuit breaker design, system protection, and fault diagnosis.

[0042] In order to explain the fault testing system for DC circuit breaker provided by the present application in more detail, the following describes Figure 1 The various physical devices in the fault testing system 100 for a DC circuit breaker are shown.

[0043] Specifically, the fault testing system 100 for a DC circuit breaker includes a circuit terminal 110 , a coupling interaction terminal 120 and a multi-physics terminal 130 , wherein the circuit terminal 110 is connected to the coupling interaction terminal 120 , and the coupling interaction terminal 120 is connected to the multi-physics terminal 130 .

[0044] The circuit terminal 110 is used to perform the current electromagnetic transient simulation on the DC circuit breaker 111 through a preset electromagnetic transient simulation model to output a dynamic current value to the coupling interaction terminal. The dynamic current value is the current value at the current moment. The electromagnetic transient simulation is used to simulate the operating state of the DC distribution network under a preset fault scenario.

[0045] Electromagnetic transient simulation is a computer simulation technology used to study electromagnetic transient processes in power systems and electronic circuits. It primarily focuses on the changes in electrical quantities such as voltage and current within a system over extremely short timescales (microseconds to milliseconds). These transient processes are caused by sudden changes in circuit state (such as switching operations and fault occurrences) and are accompanied by rapid changes in the electromagnetic field. These electromagnetic transient processes are assumed to be caused by faults and are used to simulate the environment of a DC circuit breaker in a DC distribution network fault scenario, thereby testing the performance of the DC circuit breaker. When a short circuit occurs in a DC distribution network, the voltage and current in the power system in which the DC distribution network resides can undergo dramatic changes in an instant. Electromagnetic transient simulation can accurately simulate the magnitude and direction of the fault current, as well as the overvoltage caused by the fault. The electromagnetic transient simulation model can be run by a hardware simulator built into the circuit end, enabling real-time simulation of the electromagnetic transient processes of the DC distribution network. Closed-loop fault testing can be achieved through connection to the DC circuit breaker.

[0046] Because the electromagnetic transient simulation model performs the current electromagnetic transient simulation on the DC circuit breaker, the electromagnetic transient simulation process itself changes rapidly over time, and the current can undergo drastic changes in a very short period of time. Therefore, the circuit end outputs dynamic current values ​​to show the trajectory of current changes over time, accurately reflecting the time-varying characteristics of the DC circuit breaker during the transient process and reflecting its status at different moments. In addition, by outputting dynamic current values, the circuit end allows technicians to observe the peak current, oscillations, and attenuation trends during the transient process, thereby evaluating the DC circuit breaker's current response capability, namely its current withstand capability and response speed under different transient conditions.

[0047] The coupling interaction terminal 120 is used to convert the dynamic current value into the dynamic boundary condition of the multi-physics field terminal and send the dynamic boundary condition to the multi-physics field terminal.

[0048] Among them, the dynamic boundary conditions are used to indicate the constraints of various physical quantities required by the multi-physics field end in the current state.

[0049] Based on the coupling relationships between physical fields, such as electromagnetic-mechanical coupling and electromagnetic-thermal coupling, different physical fields influence and interact with each other. The coupled interaction terminal can convert dynamic current values ​​into dynamic boundary conditions for the multi-physics terminal based on equivalent conversions of physical quantities and the use of relevant physical laws and mathematical models. Dynamic boundary conditions can constrain the solution scope of multi-physics fields, ensuring accuracy and efficiency; they can also enable information transfer and collaborative solutions between physical fields, facilitating collaborative computations across multiple physical fields to obtain accurate system responses and descriptions of physical phenomena.

[0050] The multi-physics field terminal 130 is used to determine the physical property parameter values ​​at the current moment based on the finite element models and dynamic boundary conditions of multiple preset physical fields; and to send the physical property parameter values ​​at the current moment to the coupling interaction terminal.

[0051] The physical parameter values ​​at the current moment are used to simulate the arc behavior corresponding to the arc generated by the DC circuit breaker during the breaking process.

[0052] Finite element models are an effective means of numerically simulating and analyzing different physical fields, while dynamic boundary conditions constrain and guide the solution. The combination of these two allows for the determination of physical property values. The physical property values ​​determined at the current moment by the multi-physics end have a specific purpose: to simulate the arc behavior corresponding to the arc generated during the DC circuit breaker's interruption process. By utilizing these physical property values, we can gain a deeper understanding of the arc behavior of DC circuit breakers during specific operating processes, improving the comprehensiveness and accuracy of online DC circuit breaker simulations.

[0053] The coupling interaction terminal 120 is further used to update the current resistance parameter and admittance parameter corresponding to the arc according to the physical parameter value corresponding to the arc at the current moment; and send the current resistance parameter and admittance parameter to the circuit terminal to indicate the next electromagnetic transient simulation.

[0054] For the arc generated during the DC circuit breaker's opening and closing process, its physical parameters reflect the arc's current state. These physical states are the result of the combined effects of multiple physical fields, such as electromagnetic effects affecting the current distribution in the arc, and thermal fields affecting the arc's temperature and, consequently, its conductivity. The arc's physical parameters are intrinsically linked to the resistance and admittance parameters of the circuit. These values ​​essentially reflect the circuit element's resistance to and conduction characteristics to current. As part of the circuit, changes in the arc's physical state inevitably cause changes in these electrical parameters. Therefore, the corresponding resistance and admittance parameters need to be updated based on the arc's physical parameters.

[0055] Furthermore, the role of electromagnetic transient simulation is to accurately simulate the dynamic changes of the entire system (the DC distribution network coupled with the DC circuit breaker) over time. In a system involving multiple physical fields and the presence of complex phenomena such as arcs, the results obtained from a simulation (i.e., the physical parameter values ​​at the current moment) can be used as feedback information to adjust the relevant parameters in the circuit end. By feeding back the updated current resistance parameters and admittance parameters to the circuit end, the circuit end can perform calculations based on parameters that are more in line with the actual physical changes during the next electromagnetic transient simulation, thereby achieving iterative simulation and making the entire simulation process continuously approach the actual state of the real system at each moment, thereby more accurately simulating the behavior of the arc at different stages and the dynamic response of the entire system in continuous time. In addition, the physical quantities in different physical fields constrain each other and need to be coordinated and consistent to ensure the accuracy of the simulation of the entire system. Updating and returning the resistance and admittance parameters based on the current physical parameter values ​​of the arc can ensure the coherence and consistency between the physical quantities on the circuit side and the multi-physics field side at different times, allowing the various physical fields to evolve synergistically under interaction, allowing the online simulation of the entire fault testing system to fully and accurately present complex physical processes including arc behavior.

[0056] Specifically, the traditional electromagnetic transient simulation for the opening and closing process of the DC circuit breaker usually simplifies the internal structure, electromagnetic characteristics, etc. of the DC circuit breaker, and fails to consider the nonlinear and local effects in the DC circuit breaker in detail, resulting in errors between the simulation results and the actual situation. The fault test system for the DC circuit breaker provided by the present application couples the multi-physical field terminal through the coupling interactive terminal to simulate the arc effect and nonlinear behavior (i.e., the dynamic change of current) that occurs during the opening and closing of the DC circuit breaker. In addition, the traditional electromagnetic transient simulation is highly dependent on the setting of boundary conditions, including the material parameters and current density distribution inside the circuit breaker, and usually adopts static boundary conditions, ignoring the dynamic changes of current and voltage under fault conditions, resulting in insufficient accuracy and applicability of the simulation results. The fault test system for the DC circuit breaker provided by the present application simulates the dynamic changes of current and voltage of the DC circuit breaker in the whole process under the fault scenario through the closed-loop feedback of online simulation, thereby improving the accuracy of online simulation.

[0057] See below Figure 2 , Figure 2 This is a flow chart of a fault test provided by the embodiment of the present application. Figure 2 To further introduce Figure 1 The shown diagram shows a fault testing process for a DC circuit breaker performed on various physical devices in the fault testing system 100 for a DC circuit breaker.

[0058] like Figure 2 Shown is Figure 1The data processing process implemented by the simulation software for controlling each physical device (i.e., the circuit terminal 110, the coupling interaction terminal 120, and the multi-physics field terminal 130) to perform corresponding functions in the fault testing system 100 for a DC circuit breaker shown in FIG. includes the following specific steps:

[0059] Step S201: Initialize the circuit side and the multi-physics field side.

[0060] This step occurs when the simulation software begins preparing to perform an online simulation of a DC circuit breaker fault test. This can be a simulation preparation instruction sent by a technician's terminal device. The initialization of the circuit and multi-physics side in step S201 is led by the simulation software running on the coupled interaction side.

[0061] In one possible embodiment, the coupling interaction terminal is used to send the physical parameters and initial boundary conditions in the initial state to the multi-physics field terminal before the online simulation operation of the DC circuit breaker begins; the multi-physics field terminal is used to construct a finite element model in the initial state based on the physical parameters and initial boundary conditions in the initial state to determine the simulation initial values; and send the simulation initial values ​​to the coupling interaction terminal; the coupling interaction terminal is also used to determine the initial resistance parameters and initial admittance parameters of the arc based on the simulation initial values; the circuit terminal is used to perform electromagnetic transient simulation of the DC circuit breaker through the electromagnetic transient simulation model based on the initial resistance parameters and initial admittance parameters, so as to output a dynamic current value after detecting the simulation start instruction.

[0062] The initial boundary conditions are used to indicate the constraints of various physical quantities required at the multi-physics field end in the initial state.

[0063] Among them, the function realized by the coupling interaction end shown in this example is the specific process of initializing the circuit end and the multi-physics field end corresponding to step S201. Among them, the coupling interaction end can simulate the operation process of the DC circuit breaker system from the initial state more realistically and accurately by setting the physical parameters, initial boundary conditions, etc. in the initial state in advance before the online simulation operation. And considering the coupling relationship between multiple physical fields from the initial state, by sending relevant parameters to the multi-physics field end to construct a finite element model, the interaction between different physical fields (such as electromagnetic, thermal, mechanical, etc.) in the initial state can be fully considered, avoiding the result deviation caused by unreasonable initial condition setting in the subsequent simulation process. The first dynamic current value output at the end can provide reliable data support for the subsequent simulation of the operation test of the DC circuit breaker under the fault scenario.

[0064] The physical parameters and parameters included in the initial boundary conditions sent by the coupling interaction end in the initial state are determined based on an understanding of the DC circuit breaker's physical characteristics and actual operating environment. These parameters can be determined by technicians based on an analysis of the DC circuit breaker's operating scenarios in actual DC distribution networks. Physical parameters can include the initial electrical conductivity and thermal conductivity of the DC circuit breaker material, reflecting the physical properties of the DC circuit breaker's components in their initial state. Initial boundary conditions are set based on the basic laws of physical fields and actual operating conditions. For example, in electromagnetic fields, these may include the boundary ranges of the initial electric and magnetic field strengths, which are used to constrain the value ranges of various physical quantities at the multi-physics end in the initial state.

[0065] It can be seen that in this example, by coupling the interactive end, the multi-physics field end, and the circuit end, the model is constructed and simulated using the initial parameters, and the current value of the first round of online simulation is output for the DC circuit breaker electromagnetic transient simulation, thereby improving the accuracy of subsequent closed-loop simulations and gradually improving the stability of the online simulation of the DC circuit breaker.

[0066] Step S202: electromagnetic transient simulation calculation.

[0067] Among them, this step is specifically completed by the electromagnetic transient simulation model preset in the circuit end. After completing the initial state construction, the electromagnetic transient simulation model performs electromagnetic transient simulation on the DC circuit breaker during the fault test to perform electromagnetic transient simulation calculation. The output result after calculation is the dynamic current value.

[0068] Step S203: finite element simulation calculation.

[0069] Among them, this step is specifically completed by the finite element model preset in the multi-physics field end. After completing the initial state construction and receiving the boundary conditions determined by the coupling interaction end based on the dynamic current value, the finite element model performs finite element simulation calculations according to the boundary conditions. The output results after calculation are the physical parameters related to the arc.

[0070] During the interruption of a DC circuit breaker, arcs are generated by the effects of electric, magnetic, and flow fields, as well as thermal effects. This involves magnetohydrodynamics (MHD). Specifically, the equations involved include Maxwell's equations and the Navier-Stokes equations. The Navier-Stokes equations describe fluids like liquids and air, while the Maxwell equations are a set of partial differential equations describing the relationship between electric and magnetic fields, charge, and current. They are fundamental equations in classical electromagnetism.

[0071] Among them, Maxwell's equations include the following equations:

[0072] in represents the electric potential, Indicates the electric field strength;

[0073] σ is the conductivity, represents the current density;

[0074] represents the magnetic induction intensity, represents the magnetic vector;

[0075] μ0 represents magnetic permeability;

[0076]

[0077] The Navier-Stokes equations include the conservation equations for mass, momentum, and energy. When solving magnetohydrodynamics in a finite element model, the coupling interaction terminal needs to input physical properties such as the density, specific heat capacity, and conductivity of the medium. Under the influence of current boundary conditions, the Maxwell equations and the Navier-Stokes equations are used to simulate and solve the arc's behavior, physical properties, and multi-physics fields, thereby calculating the arc's resistance parameters. Finally, the arc's resistance parameters are sent to the coupling interaction terminal, which then transmits them to the circuit terminal.

[0078] Specifically, the arc resistance parameter R arc The solution formula is:

[0079]

[0080] Where T, P, S, and l are the temperature, pressure, area, and length of each finite element, respectively. A finite element is the finite number of units that make up the finite element model. Each finite element is assigned a number, and i in the formula indicates the corresponding finite element number. Furthermore, finite elements are connected to each other via nodes. By establishing physical equations for each unit and considering the connection conditions and boundary conditions between units, an approximate solution for the resistance parameter is ultimately obtained.

[0081] Step S204: Detect fault settings.

[0082] This step is designed to be flexible and adjustable compared to traditional simulation methods for DC circuit breakers. Traditional simulation methods are usually based on offline data and require setting the fault time and circuit breaker action time before simulation, which is not flexible and real-time. However, the fault testing system for DC circuit breakers provided in this application can achieve flexible fault settings. The specific setting principle is as follows:

[0083] In one possible embodiment, when a DC circuit breaker is coupled to a DC distribution network, the DC circuit breaker includes a main current branch and a transfer branch, and the transfer branch is connected in parallel with the main current branch; before the DC circuit breaker is opened, the main current branch is in an on state and the transfer branch is in an off state; and when a fault occurs in the DC distribution network, the main current branch switches from the on state to the off state to generate an arc, and the transfer branch switches from the off state to the on state.

[0084] When coupled to a DC distribution network, the DC circuit breaker consists of a main current-carrying branch consisting of mechanical switches, a transfer branch consisting of power electronic switches, and an energy dissipation branch consisting of metal oxide semiconductor devices (MOVs). Before the DC circuit breaker opens, there is no arc, the main current-carrying branch is conductive, and the transfer branch is disconnected.

[0085] Specifically, the circuit structure of the DC circuit breaker has a fault protection mechanism. When a fault occurs in the DC distribution network (such as a short circuit fault), a large overcurrent will be generated at the fault point. In order to protect other equipment in the power grid (such as transformers, lines, etc.) from damage caused by excessive current, the main current branch needs to be disconnected. This disconnection is based on the triggering of the protection system. The protection system will detect the abnormal electrical quantities (such as overcurrent, overvoltage, etc.) generated by the fault, and then issue a command to open the switching devices in the main current branch (such as the contacts of the circuit breaker), thereby cutting off the fault current. In addition, at the moment when the main current branch switches from on to off, due to the rapid change in current, according to the law of electromagnetic induction, a high induced electromotive force will be generated around the disconnection point. At the same time, the magnetic field energy stored in the inductive elements (such as reactors) in the circuit will be released at the moment of disconnection. This energy causes electrons to continue to move in the disconnection gap, forming an arc.

[0086] Furthermore, when the main current-carrying branch is disconnected, the fault current requires a new path to avoid continued harm at the fault point. The transfer branch exists to provide such a backup path, directing the fault current from the main current-carrying branch to the transfer branch. Its conduction mechanism is typically controlled by a protection system. Upon detecting a fault disconnection in the main current-carrying branch, the protection system simultaneously or within a very short period of time issues a command to turn on the switching devices (such as power electronic devices like thyristors) in the transfer branch. The conduction of the transfer branch serves the dual purposes of fault isolation and current diversion. By diverting the fault current to the transfer branch, the fault area can be isolated from the normally operating area, reducing the scope of the fault's impact on the entire DC distribution network. Furthermore, the design parameters of the transfer branch (such as current-carrying capacity and conduction time) are determined based on the system's fault current characteristics and protection requirements to ensure that it can effectively carry the fault current after the main current-carrying branch is disconnected, maintaining relative grid stability.

[0087] It can be seen that in this example, the circuit structure setting of the DC circuit breaker enables the DC circuit breaker to switch between the main and transfer branch states when a distribution network fault occurs, thereby ensuring the safety of the distribution network and controlling the fault current path and arc generation.

[0088] In one possible embodiment, when the DC circuit breaker is decoupled from the DC distribution network and connected to the electromagnetic transient simulation model, the equivalent circuit of the DC circuit breaker includes an arc resistor, a first equivalent inductor, a bidirectional solid-state switch module, and a second equivalent inductor. The arc resistor and the first equivalent inductor are connected in series to form a first series circuit, the bidirectional solid-state switch module and the second equivalent inductor are connected in series to form a second series circuit, and the first series circuit and the second series circuit are connected in parallel.

[0089] Among them, the first equivalent inductance is used to be equivalent to the main current branch of the DC circuit breaker coupled with the DC distribution network, the second equivalent inductance is used to be equivalent to the transfer branch of the DC circuit breaker coupled with the DC distribution network, and the arc resistance of the arc resistor is determined by the current resistance parameter sent by the coupling interaction end.

[0090] For example, see Figure 3 , Figure 3 Schematic diagram of the equivalent circuit of a DC circuit breaker breaking process provided by an embodiment of the present application. Figure 3 As shown in Figure 2, when the DC circuit breaker is decoupled from the DC distribution network and connected to the electromagnetic transient simulation model, the equivalent circuit of the DC circuit breaker includes the arc resistance R arc , the first equivalent inductance L MB , bidirectional solid-state switch module U T and the second equivalent inductance L COM Among them, the arc resistance R arc With the first equivalent inductance L MB The first series circuit is connected in series, and the bidirectional solid-state switch module U T and the second equivalent inductance L COM The series circuit is the second series circuit, and the first series circuit and the second series circuit are connected in parallel. Assume that the voltage across the parallel circuit is v, and the current i (i.e., the current across the DC circuit breaker) is input from the positive pole of the external power supply of the equivalent circuit and output from the negative pole of the external power supply of the equivalent circuit. The current in the first series circuit is expressed as i mb (i.e. the main flow branch current), the current magnitude i in the second series circuit com (Transfer branch current). Before the DC circuit breaker is opened, there is no arc, the main current branch is in the on state, the transfer branch is in the off state, and the electromagnetic transient simulation model operates normally. After the distribution network is set to fail, the DC circuit breaker begins to disconnect the main current branch to generate an arc. The generated arc can be equivalent to a dynamically variable resistor (i.e., equivalent to the arc resistance R arc ), the transfer branch is turned on, and the power electronic switch can be equivalent to a resistor (i.e., equivalent to a bidirectional solid-state switch module UT The equivalent circuit of the DC circuit breaker breaking process is as follows: Figure 3 As shown in the figure, an arc is generated when the main branch mechanical switch is disconnected, and the arc resistance is R arc ,The bidirectional solid-state switch module is a power electronic switch that ,is switched to the on state during the opening and ,disconnecting process of the DC circuit breaker.

[0091] As can be seen, in this example, the circuit end constructed the equivalent circuit of the decoupled DC circuit breaker and implemented electromagnetic transient simulation of the DC circuit breaker. The role of each component and its coupling relationship with the distribution network were clarified. The arc resistance was determined through the interactive end, which facilitated the accurate simulation of DC distribution network faults.

[0092] In one possible embodiment, the fault testing system for a DC circuit breaker also includes a server; the server is used to send a fault instruction to the coupling interaction end; the coupling interaction end is also used to respond to the fault instruction when a fault instruction is detected to control the switching state of the bidirectional solid-state switch module to switch to the on state, and adjust the arc resistance value of the arc resistor to the current resistance parameter.

[0093] In this example, a technician can interact with the coupling interactive terminal through a server to set a fault online. The coupling interactive terminal controls the switching state of the bidirectional solid-state switch module through the fault command sent by the server, and adjusts the arc resistance of the arc resistor to simulate the opening and closing process of the DC circuit breaker due to a DC distribution network fault. The coupling interactive terminal can adjust the resistance of the arc resistor to the pre-set current resistance parameter according to the command, thereby accurately reproducing the impact of the arc resistance characteristics under different fault conditions, and then comprehensively testing the performance of the DC circuit breaker under various fault conditions. The purpose of the coupling interactive terminal's control operation on the bidirectional solid-state switch module is to change the connectivity of the circuit, thereby creating a fault scenario and prompting the DC circuit breaker to initiate protection action, thereby facilitating the observation and detection of key performance indicators such as the circuit breaker's response speed and action accuracy under such abnormal conditions.

[0094] Compared to traditional DC circuit breaker fault testing, the coupled interactive terminal in this example can flexibly and precisely control the arc resistance value. This arc resistance control is based on the fact that arc resistance significantly affects electrical parameters such as current and voltage during the DC circuit breaker's interruption process. By varying its resistance value, circuit environments with varying fault severity can be simulated. For example, a smaller arc resistance value resembles a minor fault, resulting in a relatively gradual current change; a larger resistance value simulates a severe fault, causing a sharp drop in current and a significant increase in voltage. This allows the DC circuit breaker to be observed for its ability to effectively interrupt the circuit and to determine its arc extinguishing capability and ability to withstand voltage surges.

[0095] It can be seen that in this example, the server collaborates with the coupled interactive terminal, the fault instruction triggers switch switching and resistance adjustment, simulates the fault scenario, enhances the system's simulation capability for fault response, and improves the system's practicality and flexibility, enabling the setting of online faults.

[0096] Step S205, calculating the resistance parameter; Step S206, updating the admittance parameter.

[0097] Among them, these two steps are the subsequent processes after the coupling interaction end determines that the fault setting is detected during the execution of step S204, and are also the normal data processing process. After the coupling interaction end updates the resistance parameters and admittance parameters of the arc, the coupling interaction end will send these parameters to the circuit end to perform the next round of electromagnetic transient simulation.

[0098] In one possible embodiment, the electromagnetic transient simulation model is used to: after obtaining the updated initial resistance parameter or current resistance parameter sent by the circuit end, determine the first admittance corresponding to the first series circuit, the second admittance corresponding to the second series circuit, and the arc resistance at the current moment according to the updated initial resistance parameter or current resistance parameter; obtain the voltage value at both ends of the equivalent circuit of the DC circuit breaker, as well as the first current value corresponding to the first series circuit, the second current value corresponding to the second series circuit, and the switch resistance of the bidirectional solid-state switch module, the first current value is the Nouton equivalent current of the main current branch, and the second current value is the Nouton equivalent current of the transfer branch; perform electromagnetic transient simulation to determine the dynamic current value according to the arc resistance, switch resistance, first current value, second current value, and voltage value at the current moment.

[0099] For example, see Figure 4 , Figure 4 Schematic diagram of the structure of an electromagnetic transient model of a DC circuit breaker breaking process provided by an embodiment of the present application. Figure 4 As shown, the circuit structure is Figure 3 The electromagnetic transient model of the equivalent circuit is shown in FIG. Figure 4 i, i in MB 、i COM They are the current at both ends of the DC circuit breaker, the main current branch current and the transfer branch current, Y LMB 、Y LCOM The admittance of the equivalent inductance of the main current branch and the transfer branch, ih LMB and ih LCOM are the Norton equivalent historical currents of the main current branch and the transfer branch, respectively. The equivalent inductance of the main current branch is usually small, while the transfer branch is usually composed of multiple power electronic modules (i.e., bidirectional solid-state switch modules U T ) and has a large equivalent inductance, whose value can be obtained by finite element simulation.

[0100] also, Figure 4 The calculation formula corresponding to the electromagnetic transient calculation performed by the electromagnetic transient model of the equivalent circuit shown in is:

[0101] i(t)=G MB v(t)-ih LMB (t)+G COM v(t)-ih COM (t);

[0102] in,

[0103] Among them, G MB and G COM are the equivalent admittances of the main flow branch and the transfer branch, R T Bidirectional solid-state switch module U T The corresponding switch resistance value, t refers to the current time corresponding to the circuit end, that is, the current system time of the simulation software performing electromagnetic transient simulation, and △t refers to the time step, that is, the time interval divided by the electromagnetic transient model to discretize time in order to simulate the dynamic change process of the system over time.

[0104] Among them, through the above calculation, the electromagnetic transient simulation model can be based on the updated initial resistance parameter or the current resistance parameter (i.e. arc resistance R arc ), and a preset first equivalent inductance L MB The corresponding first admittance Y LMB and the second equivalent inductance L COM The corresponding second admittance Y LCOM , determine the first admittance corresponding to the first series circuit (i.e. G MB ), the second admittance corresponding to the second series circuit (i.e. G COM ) and the arc resistance R at the current moment arc (ie the updated initial resistance parameter or the current resistance parameter). Then according to the first admittance G MB , the second admittance G COM and the subsequent collected current values ​​i at both ends of the DC circuit breaker and the current values ​​of each branch (i.e. the first current value ih LMB and the second current value ih LCOM ), the voltage value v across the equivalent circuit of the DC circuit breaker, and the bidirectional solid-state switch module U T The corresponding switch resistance R T , perform the next round of electromagnetic transient simulation on the DC circuit breaker, and then obtain the dynamic current value of the next round of output.

[0105] It can be seen that in this example, the electromagnetic transient simulation model determines the admittance and other parameters based on the resistance parameters, and performs simulation to obtain the dynamic current value in combination with the circuit parameters, thereby improving the accuracy of simulating the electromagnetic transient characteristics of the circuit breaker and improving the accuracy and effectiveness of the online simulation.

[0106] Step S207: The superimposed simulation step length is greater than or equal to the total simulation time.

[0107] This step is a numerical value determination step, which determines whether the superimposed simulation step size is greater than or equal to the preset total simulation duration. This step is the "if no" branch of step S204 and a subsequent step of step S206. When the coupled interactive end determines that the superimposed simulation step size is greater than or equal to the total simulation duration, the simulation ends. If the coupled interactive end determines that the superimposed simulation step size is less than the total simulation duration, step S208 is executed.

[0108] Specifically, the concepts of simulation step length and total simulation time are described in the following embodiments.

[0109] In a possible embodiment, the coupling interaction end is also used to: obtain a preset total simulation time and simulation step before the online simulation operation for the DC circuit breaker begins; and when performing the online simulation operation for the DC circuit breaker, if the dynamic current value sent by the circuit end is detected, superimpose a simulation step; and when the total time corresponding to the superimposed simulation step is greater than or equal to the total simulation time, determine that the online simulation is finished and stop data transmission between the circuit end and the multi-physics field end.

[0110] The simulation step size is used to indicate the time required for the fault test system of the DC circuit breaker to complete a single online simulation operation.

[0111] Among them, the control principle of this example includes time control and iteration principles. Before the simulation starts, the total simulation time and simulation step length preset by the technician are saved in the coupling interaction terminal. The simulation step length determines the time interval for each online simulation operation, and the continuous simulation process is analyzed step by step according to fixed time segments. After the circuit end outputs the dynamic current value, the simulation step length is superimposed once, which means that as each new current value is obtained, the simulation time advances according to the set step length to achieve an orderly iterative simulation of the entire fault test process in the time dimension, until the total time after superposition reaches or exceeds the preset total simulation time length, representing the end of the entire simulation cycle. In addition, the coupling interaction terminal, as a key link in coordinating the circuit end and the multi-physics field end, controls the start and end of data transmission according to the simulation step length to ensure that data interaction is carried out in an orderly manner between the various ends within a reasonable simulation time range. For example, within each simulation step, the circuit side performs electromagnetic transient simulation based on current parameters and outputs dynamic current values. The multiphysics side calculates physical property values ​​based on boundary conditions and other factors. The coupled interaction side performs corresponding parameter updates and transfers. When the total simulation duration is reached, data transmission ends, ensuring the integrity and rationality of the coordinated operation of all components of the fault testing system and avoiding meaningless data exchange and excessive computational resource consumption. Data transmission between the circuit side and the multiphysics side is stopped appropriately based on the simulation step length, avoiding unnecessary data exchange and computation, effectively conserving computer computing resources, storage resources, and network bandwidth. Especially for complex multiphysics coupling and large-scale circuit simulation scenarios, rational resource utilization can improve the operational efficiency of the entire fault testing system, ensuring stable system operation and quickly generating valid simulation results. The total simulation duration and simulation step size settings standardize the entire simulation process, facilitating repeated verification in different research scenarios and by different operators.

[0112] It can be seen that in this example, the coupling interaction end can obtain the duration and step length, and superimpose the step length according to the detection of the dynamic current value during operation. When the superimposed step length reaches the total duration, the simulation is determined to be over, effectively controlling the online simulation process, simulating the working status of the DC circuit breaker in different time stages, and improving the stability and coordination of the system in executing online simulation operations.

[0113] Step S208: superimpose a simulation step.

[0114] In this step, after the simulation software determines that the superimposed simulation step size is less than the total simulation duration, it superimposes another simulation step size on the superimposed simulation step size to internally time whether the online simulation operation for the DC circuit breaker has ended. Furthermore, after this step is completed, based on the calculation results obtained in steps S205 and S206, the coupling interaction terminal and the circuit terminal interact to perform the next online simulation operation, gradually improving the accuracy of the online simulation for the DC circuit breaker and enhancing the comprehensiveness of the DC circuit breaker fault testing.

[0115] In a possible embodiment, the coupling interaction end further includes a display device; the display device is used to display a result value calculated in each online simulation operation for the DC circuit breaker.

[0116] The result value includes at least one of the following: a dynamic current value corresponding to the online simulation operation, a physical parameter value at the current moment, and a current resistance parameter and admittance parameter corresponding to the arc.

[0117] For example, when the display device displays the dynamic current value, the display device can display a current waveform graph, with time as the horizontal axis and the current magnitude as the vertical axis, showing the curve of the current changing over time. The dynamic processes of the current such as the rise, fall, and oscillation can be intuitively seen. For example, at the moment the DC circuit breaker is disconnected, the current will drop sharply, and this change can be clearly shown through the waveform graph. The coupled interaction end can determine the current peak value and the current effective value based on the change of the current value during the simulation process, where the current peak value is the maximum value reached by the current, which can be used to evaluate the ability of the circuit breaker to withstand the current shock in the event of a fault, and the current effective value is used to measure the equivalent heating effect of the current in one cycle (for AC) or a period of time (for DC), which can be used to evaluate the heating condition and thermal stability of the DC circuit breaker. By displaying the dynamic current value, researchers can analyze the characteristics of the circuit during the transient process, such as the oscillation frequency and damping of the circuit. This helps evaluate the stability and dynamic response performance of the circuit, and can be used to evaluate the performance of the DC circuit breaker based on parameters such as current peak value and effective value. For example, it can determine whether the circuit breaker can successfully cut off the fault current within the specified time, and whether it will cause overheating due to excessive current under normal working conditions.

[0118] For example, when the display screen device displays the current resistance and admittance parameters corresponding to the arc, the display screen device can display the arc resistance value, that is, the resistance of the arc at the current moment. Changes in arc resistance will affect the current distribution and energy loss in the circuit. Its magnitude is related to factors such as the arc temperature, length, and gas composition. The display screen device can also display the arc admittance value, which is the inverse of the arc resistance. This parameter is used to measure the arc's ability to conduct current. Changes in the admittance value reflect changes in the arc's conductive properties. The display of the above content allows researchers to understand the generation, development, and extinction process of the arc during the DC circuit breaker's opening and closing process. For example, as the arc extinguishing process progresses, the arc resistance will gradually increase and the admittance will gradually decrease. These parameters can also be used to analyze parameters such as the equivalent impedance and power factor at the circuit end, thereby analyzing the circuit's stability and energy transmission efficiency.

[0119] It can be seen that in this example, the setting of the display device at the coupling interactive end enables it to intuitively present the simulation result values, making it easier for researchers to view and analyze the changes in current, physical properties, and arc parameters during the online simulation of the DC circuit breaker. This improves the practicality of the system in performing online simulations through visualization, making it easier for researchers to subsequently optimize the DC circuit breaker.

[0120] In a possible embodiment, the preset physical field corresponding to the finite element model includes at least one of the following types of physical fields: electromagnetic field, temperature field, flow field, and stress field.

[0121] The rationale behind setting the electromagnetic field is that electromagnetic fields are a key physical field in scenarios involving DC circuit breakers. When current flows through the various branches of a circuit breaker, a magnetic field is generated in the surrounding space. According to Ampere's circuit law, there is a close relationship between current and magnetic field. For example, when the main current branch is conducting, a strong magnetic field is distributed around the branch. When a fault occurs and the main current branch is disconnected, generating an arc, the motion of charged particles in the arc plasma also generates a complex electromagnetic field. Finite element models of the electromagnetic field can be used to determine the spatial distribution and temporal variations of physical quantities such as electric and magnetic field strengths, thereby analyzing the impact of electromagnetic forces on the internal structure of the circuit breaker and arc behavior. Furthermore, the rationale behind setting the temperature field is that the thermal effect of current, particularly in the conductive components of the main current branch and transfer branches, generates Joule heating. According to Joule's law, heat is generated when current flows through a conductor with resistance. This heat will cause the internal temperature of the circuit breaker to rise. The change in the temperature field will affect the physical properties of the material. Through the finite element model of the temperature field, the temperature distribution of the circuit breaker under different working conditions (such as normal operation, fault interruption, etc.) can be simulated, and the possible overheating area can be predicted, providing a basis for thermal management and material selection.

[0122] Furthermore, the rationale behind setting up a finite element model for the physical field of the flow field is that the flow field plays a significant role within a circuit breaker, particularly in situations involving arc extinguishing or gas insulation. For example, within the arc extinguishing chamber, the gas flow state affects the cooling and extinguishing of the arc. The gas flow can remove heat generated by the arc and change the distribution of the arc plasma. The finite element model of the flow field can analyze the distribution of physical quantities such as gas flow rate and pressure, facilitating the design of more effective arc extinguishing devices and optimizing gas insulation systems. Furthermore, the rationale behind setting up a physical field for the stress field is that when the branch state of a circuit breaker changes (such as when the main current branch is disconnected and an arc is generated), the internal structure of the circuit breaker will experience varying degrees of stress due to factors such as electromagnetic forces and thermal expansion. According to the principles of material mechanics, thermal expansion and electromagnetic forces caused by temperature changes can lead to strain and stress in components. The finite element model of the stress field can predict structural deformation, stress concentration areas, and other factors, providing a reference for the mechanical design of the circuit breaker and ensuring its mechanical reliability under various operating conditions.

[0123] As can be seen in this example, the finite element model encompassing multiple physical fields comprehensively accounts for the various physical phenomena involved in the operation and failure of a DC circuit breaker. Rather than being limited to the analysis of a single physical field, the model comprehensively considers the inter-coupling relationships among electromagnetic, temperature, flow, and stress fields. This allows for a more realistic simulation of the actual operation of the DC circuit breaker, providing a foundation for accurate simulation of its multi-physics coupling behavior and improving the comprehensiveness and accuracy of fault testing.

[0124] It can be seen that in this application, the fault testing system for DC circuit breakers provided in this application realizes the coupling of the finite element simulation model in the multi-physical field and the electromagnetic transient simulation model in the circuit end through the coupling interaction end, thereby providing the DC circuit breaker with real-time dynamically changing boundary conditions and real-time changing arc behavior, improving the accuracy of electromagnetic transient simulation and the flexibility of finite element simulation, so that the DC circuit breaker can adapt to different working conditions, and improving the accuracy and comprehensiveness of fault testing for DC circuit breakers.

[0125] Furthermore, the present application also provides a DC distribution network, wherein a distribution master station includes any one of the fault testing systems for DC circuit breakers mentioned in the above embodiments.

[0126] It should be understood that all solutions and products implemented based on the above-mentioned fault testing system for DC circuit breakers should fall within the scope of protection of this application.

[0127] Those skilled in the art will clearly understand that for the sake of convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0128] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A fault testing system for a DC circuit breaker, characterized in that: It includes a circuit end, a coupling interaction end and a multi-physics field end, wherein the circuit end is connected to the coupling interaction end, and the coupling interaction end is connected to the multi-physics field end; The circuit end is used to perform a current electromagnetic transient simulation on the DC circuit breaker using a preset electromagnetic transient simulation model to output a dynamic current value to the coupling interaction end, where the dynamic current value is the current value at the current moment. The electromagnetic transient simulation is used to simulate the operating state of the DC distribution network under a preset fault scenario; The coupling interaction terminal is used to convert the dynamic current value into a dynamic boundary condition of the multi-physics field terminal, and send the dynamic boundary condition to the multi-physics field terminal, wherein the dynamic boundary condition is used to indicate the constraint conditions of various physical quantities required by the multi-physics field terminal in a current state; The multi-physics field terminal is configured to determine, based on finite element models of multiple preset physical fields and the dynamic boundary conditions, a physical property parameter value at a current moment, wherein the physical property parameter value at the current moment is used to simulate arc behavior corresponding to an arc generated during a breaking process of the DC circuit breaker; and to send the physical property parameter value at the current moment to the coupling interaction terminal; The coupling interaction end is further used to update the current resistance parameter and admittance parameter corresponding to the arc according to the physical parameter value corresponding to the arc at the current moment; and send the current resistance parameter and the admittance parameter to the circuit end to indicate the next electromagnetic transient simulation.

2. The fault testing system for DC circuit breaker according to claim 1, characterized in that: The coupling interaction terminal is used to send physical property parameters and initial boundary conditions in an initial state to the multi-physics field terminal before starting an online simulation operation for the DC circuit breaker, wherein the initial boundary conditions are used to indicate constraint conditions of various physical quantities required by the multi-physics field terminal in the initial state; The multi-physics field terminal is used to construct the finite element model in the initial state based on the physical property parameters in the initial state and the initial boundary conditions to determine the simulation initial value; and, sending the simulation initial value to the coupling interaction terminal; The coupling interaction end is further used to determine the initial resistance parameter and initial admittance parameter of the arc according to the simulation initial value; The circuit end is used to perform electromagnetic transient simulation on the DC circuit breaker through the electromagnetic transient simulation model according to the initial resistance parameter and the initial admittance parameter, so as to output the dynamic current value after detecting the simulation start instruction.

3. The fault testing system for DC circuit breaker according to claim 2, characterized in that: The coupling interaction end is also used for: Before starting the online simulation operation for the DC circuit breaker, obtaining a preset total simulation time and a simulation step length, wherein the simulation step length is used to indicate the time required for the fault test system for the DC circuit breaker to complete a single online simulation operation; as well as, When performing the online simulation operation for the DC circuit breaker, if the dynamic current value sent by the circuit end is detected, superimposing the simulation step length once; as well as, When the total duration corresponding to the superimposed simulation step lengths is greater than or equal to the total simulation duration, it is determined that the online simulation is ended, and data transmission between the circuit end and the multi-physics field end is stopped.

4. The fault testing system for DC circuit breaker according to claim 3, characterized in that: When the DC circuit breaker is coupled to a DC distribution network, the DC circuit breaker comprises a main current-carrying branch and a transfer branch, wherein the transfer branch is connected in parallel with the main current-carrying branch; Before the DC circuit breaker is opened, the main current branch is in a conducting state and the transfer branch is in a disconnected state; as well as, When the DC power distribution network fails, the main current-carrying branch switches from the conducting state to the disconnected state to generate the arc, and the transfer branch switches from the disconnected state to the conducting state.

5. The fault testing system for DC circuit breaker according to claim 4, characterized in that: When the DC circuit breaker is decoupled from the DC distribution network and connected to the electromagnetic transient simulation model, the equivalent circuit of the DC circuit breaker includes an arc resistor, a first equivalent inductor, a bidirectional solid-state switch module, and a second equivalent inductor. The arc resistor and the first equivalent inductor are connected in series to form a first series circuit, and the bidirectional solid-state switch module and the second equivalent inductor are connected in series to form a second series circuit. The first series circuit and the second series circuit are connected in parallel. The first equivalent inductor is used to be equivalent to a main current-carrying branch of the DC circuit breaker coupled to the DC distribution network, and the second equivalent inductor is used to be equivalent to a transfer branch of the DC circuit breaker coupled to the DC distribution network. The arc resistance of the arc resistor is determined by the current resistance parameter sent by the coupling interaction terminal.

6. The fault testing system for DC circuit breaker according to claim 5, characterized in that: The fault testing system for DC circuit breaker further includes a server; The server is configured to send a fault instruction to the coupling interaction terminal; The coupling interaction end is also used to control the switching state of the bidirectional solid-state switch module to switch to the conducting state and adjust the arc resistance of the arc resistor to the current resistance parameter in response to the fault instruction when the fault instruction is detected.

7. The fault testing system for a DC circuit breaker according to claim 5, characterized in that: The electromagnetic transient simulation model is used to: After obtaining the updated initial resistance parameter or the current resistance parameter sent by the circuit end, determining a first admittance corresponding to the first series circuit, a second admittance corresponding to the second series circuit, and the arc resistance at the current moment according to the updated initial resistance parameter or the current resistance parameter; Obtaining voltage values ​​across the equivalent circuit of the DC circuit breaker, a first current value corresponding to the first series circuit, a second current value corresponding to the second series circuit, and a switch resistance of the bidirectional solid-state switch module, wherein the first current value is a Naughton equivalent current of the main current-carrying branch, and the second current value is a Naughton equivalent current of the transfer branch; The electromagnetic transient simulation is performed to determine the dynamic current value according to the arc resistance, the switch resistance, the first current value, the second current value, and the voltage value at a current moment.

8. The fault testing system for a DC circuit breaker according to any one of claims 1 to 7, characterized in that: The coupling interaction end also includes a display screen device; The display screen device is used to display the result value calculated in each online simulation operation of the DC circuit breaker, and the result value includes at least one of the following: the dynamic current value corresponding to the online simulation operation, the physical parameter value at the current moment, and the current resistance parameter and the admittance parameter corresponding to the arc.

9. The fault testing system for a DC circuit breaker according to any one of claims 1 to 7, characterized in that: The preset physical field corresponding to the finite element model includes at least one of the following types of physical fields: Electromagnetic field, temperature field, flow field, stress field.

10. A DC distribution network, characterized in that: The DC distribution network includes the fault testing system for a DC circuit breaker according to any one of claims 1 to 9.

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