Fault test system for direct-current circuit breaker and direct-current power distribution network

Abstract

The invention provides a fault test system for a direct-current circuit breaker and a direct-current power distribution network. The fault test system comprises a circuit end, a coupling interaction end and a multi-physics field end, the circuit end is used for performing electromagnetic transient simulation on the direct current circuit breaker through an electromagnetic transient simulation model so as to output a dynamic current value to the coupling interaction end; the coupling interaction end is used for converting the dynamic current value into a dynamic boundary condition and sending the dynamic boundary condition to the multi-physical field end; the multi-physical field end is used for determining physical property parameter values based on the finite element models and the dynamic boundary conditions of a plurality of preset physical fields and sending the physical property parameter values to the coupling interaction end; and the coupling interaction end is used for updating the current resistance parameter and the admittance parameter of the arc according to the physical property parameter value, and sending the current resistance parameter and the admittance parameter to the circuit end to indicate the next electromagnetic transient simulation. In this way, connection between the multi-physical field end and the circuit end is constructed through the coupling interaction end, and the comprehensiveness of fault testing of the direct-current circuit breaker is improved.

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 DC transmission technology, high-voltage DC systems have occupied an increasingly important position in power grid infrastructure construction and have been widely used due to their many advantages, such as low loss in long-distance transmission and large transmission capacity.

[0003] However, since the fault current of the DC system does not have a natural zero-crossing point, the breaking capacity and response speed of the DC circuit breaker in the high-voltage DC system directly affect the safety and stability of the entire power grid operation. The traditional fault test for DC circuit breakers simulates the breaking process of the DC circuit breaker based on initial parameters and offline data, resulting in poor fault test effect and accuracy, and limited applicability. Summary of the invention

[0004] The present application proposes a fault testing system for a DC circuit breaker, in order to achieve the connection between electromagnetic transient simulation and finite element simulation corresponding to the arc, to build a communication connection between the multi-physical field and the circuit in which the DC circuit breaker is located, so that different types of simulations can work together to improve the comprehensiveness and accuracy of fault testing for the DC circuit breaker.

[0005] The 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-physical field end, wherein the circuit end is connected to the coupling interaction end, and the coupling interaction end is connected to the multi-physical field end;

[0006] The circuit end is used to perform the current electromagnetic transient simulation on the DC circuit breaker through 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 for converting a dynamic current value into a dynamic boundary condition of a multi-physics field terminal, and sending the dynamic boundary condition to the multi-physics field terminal, wherein the dynamic boundary condition is used for indicating constraint conditions of various physical quantities required by the multi-physics field terminal in a current state;

[0008] The multi-physics field terminal is used to determine the physical property parameter value at the current moment based on the finite element model and dynamic boundary conditions of multiple preset physical fields, and the physical property parameter value at the current moment is 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 value 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 the online simulation operation for the DC circuit breaker, and the initial boundary conditions are used to indicate the constraint conditions of various physical quantities required by the multi-physics field terminal in the initial state;

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

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

[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 the simulation start instruction.

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

[0015] Before starting the 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 the data transmission between the circuit end and the multi-physics field end is stopped.

[0018] In a 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 disconnected, the main current-carrying branch is in the on state and the transfer branch is in the off state; and,

[0020] When a fault occurs in the DC power distribution network, the main current-carrying 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.

[0021] In a 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 the main current branch of the DC circuit breaker coupled to the DC distribution network, the second equivalent inductor is used to be equivalent to the transfer branch of the DC circuit breaker coupled to 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.

[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 a fault instruction to the coupling interaction terminal;

[0024] The coupling interaction end is also used to control the switch 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 values ​​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 a possible embodiment, 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 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 test system for a DC circuit breaker includes a circuit end, a coupling interaction end, and a multi-physics field end. Among them, the circuit end includes an electromagnetic transient simulation model and a DC circuit breaker, and the multi-physics field end includes a finite element model. The coupling of the multi-physics field finite element simulation and the circuit electromagnetic transient simulation is realized through the coupling interaction end, so as to provide the DC circuit breaker with real-time dynamically changing boundary conditions and real-time changing arc behavior, improve 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 improve 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

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

[0031] Figure 2 It is a schematic diagram of a fault test process provided by an embodiment of the present application;

[0032] Figure 3 It 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 It 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 solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, 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", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

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

[0037] In the embodiments of the present application, "and / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent the following three situations: A exists alone; A and B exist at the same time; B exists alone. Among them, A and B can be singular or plural.

[0038] In the embodiment of the present application, the symbol " / " can indicate that the objects associated with each other are in an "or" relationship. In addition, the symbol " / " can also indicate a division sign, that is, performing a division operation. For example, A / B can indicate A divided by B.

[0039] In the embodiments of the present application, "at least one item" or similar expressions refer to any combination of these items, including any combination of single items or plural items, and refer to one or more, and multiple refers to two or more. For example, at least one 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 the present application, "equal to" can be used in conjunction with greater than, and is applicable to the technical solution adopted when greater than, and can also be used in conjunction with less than, and is applicable to the technical solution adopted when less than. When equal to is used in conjunction with greater than, it is not used in conjunction with less than; when equal to is used in conjunction with less than, it is not used in conjunction with greater than.

[0041] Please refer to the following Figure 1 , Figure 1 Schematic 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 test system for DC circuit breakers is as follows: the fault test system 100 for DC circuit breakers includes a circuit terminal 110, a coupling interaction terminal 120 and a multi-physics field terminal 130, and 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 field terminal 130, so as to achieve real-time coupling of the arc's thermal-electric-magnetic multi-physics field and circuit parameters by establishing a mutual feedback relationship, so that the simulation process can dynamically reflect the state changes of the arc at different times and spaces, avoid ignoring the dynamic changes of current and voltage under fault conditions due to initial boundary conditions, and improve the accuracy of the simulation results. In addition, based on online simulation, the fault test system 100 for DC circuit breakers can timely capture the change process of the arc and its impact on the circuit, thereby 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 field 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 field terminal 130 .

[0044] The circuit end 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 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.

[0045] Among them, electromagnetic transient simulation is a computer simulation technology used to study electromagnetic transient processes in power systems and electronic circuits. It mainly focuses on the changes in electrical quantities such as voltage and current in the system in a very short time (microseconds to milliseconds). These transient processes are caused by sudden changes in circuit states (such as switch operations, faults, etc.) and are accompanied by rapid changes in electromagnetic fields. The electromagnetic transient process here defaults to being caused by a fault, and is used to simulate the environment in which the DC circuit breaker is in a fault scenario of the DC distribution network, thereby testing the performance of the DC circuit breaker. When a short circuit fault occurs in the DC distribution network, the voltage and current in the power system where the DC distribution network is located will change dramatically in an instant. Through electromagnetic transient simulation, the magnitude and direction of the fault current and the overvoltage caused by the fault can be accurately simulated. The electromagnetic transient simulation model can be run by the built-in hardware simulator in the circuit end, so that it can simulate the electromagnetic transient process of the DC distribution network in real time, and realize closed-loop fault testing through connection with the DC circuit breaker.

[0046] Among them, since 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 will change dramatically in a very short time. Therefore, the circuit end will output dynamic current values ​​to show the trajectory of current changes over time, so as to accurately reflect the time-varying characteristics of the DC circuit breaker in the transient process and reflect the state at different times. In addition, by outputting dynamic current values, the circuit end allows technicians to observe the peak value, oscillation, and attenuation trend of the current in the transient process, and then evaluate the current response capability of the DC circuit breaker, that is, the current tolerance 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] 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] Among them, based on the coupling relationship between physical fields, such as electromagnetic-mechanical coupling, electromagnetic-thermal coupling, etc., different physical fields influence and interact with each other. The coupling interaction end can convert the dynamic current value into the dynamic boundary conditions of the multi-physical field end based on the equivalent conversion of physical quantities and with the help of relevant physical laws and mathematical models. On the one hand, the dynamic boundary conditions can constrain the solution scope of multi-physical fields and ensure the accuracy and efficiency of the solution; on the other hand, it can realize information transmission and collaborative solution between physical fields, and assist in the collaborative calculation of multi-physical fields to obtain accurate system response and physical phenomenon description.

[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] Among them, the finite element model is an effective means of numerical simulation analysis of different physical fields, while the dynamic boundary conditions play a role in constraining and guiding the solution. The combination of the two can realize the determination of the physical parameter values. And the physical parameter values ​​at the current moment determined by the multi-physical field end have a clear purpose, that is, to simulate the arc behavior corresponding to the arc generated by the DC circuit breaker during the breaking process. By using these physical parameter values, we can have a deeper understanding of the arc performance of the DC circuit breaker in a specific working process, and improve the comprehensiveness and accuracy of the online simulation of the DC circuit breaker.

[0053] The coupling interaction terminal 120 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 terminal to indicate the next electromagnetic transient simulation.

[0054] Among them, for the arc generated by the DC circuit breaker during the breaking process, its physical parameter values ​​reflect the physical state of the arc at the current moment, and these physical states are the result of the joint action of multiple physical fields, such as electromagnetic effects affecting the current distribution in the arc, thermal fields affecting the temperature of the arc and thus affecting its conductivity, etc. The physical parameters of the arc are intrinsically related to the resistance and admittance parameters in the circuit, because the resistance and admittance essentially reflect the obstruction and conduction characteristics of the circuit elements to the current. As a part of the circuit, the change in the physical state of the arc will inevitably cause changes in these electrical parameters, so it is necessary to update the corresponding resistance and admittance parameters based on the physical parameter values ​​of the arc.

[0055] Furthermore, the role of electromagnetic transient simulation is to accurately simulate the dynamic change process of the entire system (DC distribution network coupled with DC circuit breaker) over time. In a system involving multiple physical fields and 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 constantly 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 physical parameter values ​​of the arc at the current moment can ensure the continuity and consistency between the physical quantities at the circuit end and the multi-physical field end at different times, allowing the physical fields to evolve synergistically under interaction, so that the online simulation of the entire fault test system can fully and accurately present the complex physical process 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 end through the coupling interaction end to simulate the arc effect and nonlinear behavior (i.e., the dynamic change of current) that occurs during the opening and closing process of the DC circuit breaker. In addition, the traditional electromagnetic transient simulation relies heavily on the setting of boundary conditions, including material parameters and current density distribution inside the circuit breaker, and usually uses static boundary conditions, ignoring the dynamic changes of current and voltage under fault conditions, making the accuracy and applicability of the simulation results insufficient. The fault test system for the DC circuit breaker provided by the present application simulates the dynamic changes of current and voltage of the entire process of the DC circuit breaker in the fault scenario through the closed-loop feedback of the online simulation, thereby improving the accuracy of the online simulation.

[0057] See below Figure 2 , Figure 2 This is a schematic diagram of a fault test flow provided by an embodiment of the present application. Figure 2 To further introduce Figure 1 The shown is a fault testing process for a DC circuit breaker performed on each physical device 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-physical field terminal 130) to perform corresponding functions in the fault test system 100 for a DC circuit breaker shown in the figure has the following specific steps:

[0059] Step S201, the circuit end and the multi-physics field end are initialized.

[0060] The prerequisite for this step is that the simulation software starts to prepare to perform online simulation for the fault test of the DC circuit breaker, which may be a simulation preparation instruction sent by the terminal device of the technician. The circuit end and the multi-physics field end initialization of step S201 are led by the coupled interaction end running the simulation software.

[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 starts; 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 value; and send the simulation initial value to the coupling interaction terminal; the coupling interaction terminal is also used to determine the initial resistance parameter and initial admittance parameter of the arc according to the simulation initial value; the circuit terminal 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.

[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 build 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] Among them, the physical parameters in the initial state sent by the coupling interaction end and the parameters contained in the initial boundary conditions are determined based on the understanding of the physical characteristics of the DC circuit breaker and the actual operating environment. These can be determined by technicians based on the analysis of the working scenario of the DC circuit breaker in the actual DC distribution network. The physical parameters may include the initial electrical conductivity and thermal conductivity of the DC circuit breaker material, etc. These parameters reflect the physical properties of each component of the DC circuit breaker in the initial state. The initial boundary conditions are set according to the basic laws of the physical field and the actual working conditions. For example, in the electromagnetic field, they may include the boundary range of the initial electric field strength and magnetic field strength, etc., which are used to constrain the value range of each physical quantity at the multi-physical field 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, so as to output the current value of the first round of online simulation for the electromagnetic transient simulation of the DC circuit breaker, improve the accuracy of the subsequent closed-loop simulation, and gradually improve 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 the electromagnetic transient simulation model completes the initial state construction, the electromagnetic transient simulation during the fault test of the DC circuit breaker is performed to perform electromagnetic transient simulation calculations, and the output result after the 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] Among them, during the opening and closing process of the DC circuit breaker, arcs are generated under the action of electric field, magnetic field, flow field and thermal effect, which involves magnetohydrodynamics. The specific formulas involved are Maxwell equations and Navier-Stokes equations. Navier-Stokes equations refer to Navier-Stokes equations, which are a set of equations describing fluid substances such as liquids and air. Maxwell equations are a set of partial differential equations that describe the relationship between electric field, magnetic field, charge and current. It is the basic equation of 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] Among them, the Navier-Stokes equations include the mass conservation equation, momentum conservation equation, and energy conservation equation. When solving the magnetohydrodynamics in the finite element model, the coupled interactive end needs to input the density, specific heat capacity, conductivity and other physical parameters of the medium. Under the action of the current boundary conditions, the Maxwell equations and Navier-Stokes equations are used to simulate and solve the arc's behavior and physical parameters as well as the multi-physics field, and then the arc's resistance parameters are calculated. Finally, the arc's resistance parameters are sent to the coupled interactive end, and then the coupled interactive end transmits the resistance parameters to the circuit end.

[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. The finite element is a finite number of units that constitute the finite element model. Each finite element has a corresponding number, and the i in the formula is used to indicate the number of the corresponding finite element. In addition, the finite elements are connected to each other through nodes. By establishing physical equations for each unit and considering the connection conditions and boundary conditions between units, the approximate solution of the resistance parameter is finally solved.

[0081] Step S204, detecting fault settings.

[0082] Among them, this step is a flexible and adjustable step set for the traditional simulation method for DC circuit breakers. Traditional simulation methods are usually based on offline data for simulation, and it is necessary to set the fault time and circuit breaker action time before simulation, which is not flexible and real-time. The fault test system for DC circuit breakers provided in this application can realize flexible fault settings. The specific setting principle is as follows:

[0083] In a possible embodiment, when the 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 disconnected, 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 an on state to an off state to generate an arc, and the transfer branch switches from an off state to an on state.

[0084] Among them, when the DC circuit breaker is coupled with the DC distribution network, the DC circuit breaker includes a main current branch composed of a mechanical switch, a transfer branch composed of a power electronic switch, and an energy dissipation branch composed of a metal oxide sensitive device (MOV). Before the DC circuit breaker is disconnected, there is no arc, the main current branch is in the on state, and the transfer branch is in the off state.

[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 quantity (such as overcurrent, overvoltage, etc.) generated by the fault, and then issue an instruction to open the switch device (such as the contact of the circuit breaker) in the main current branch, thereby cutting off the fault current. In addition, at the moment when the main current branch switches from on to off, due to the sharp change of 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 element (such as the reactor, etc.) in the circuit will be released at the moment of disconnection. This energy prompts the electrons to continue to move in the disconnection gap to form an arc.

[0086] Furthermore, when the main current branch is disconnected, the fault current needs a new path to avoid continued harm at the fault point. The existence of the transfer branch is to provide such a backup path to guide the fault current from the main current branch to the transfer branch. Its conduction mechanism is usually also controlled by the protection system. After detecting that the main current branch is disconnected due to a fault, the protection system will issue an instruction at the same time or in a very short time to turn on the switching devices (such as power electronic devices such as thyristors) in the transfer branch. The conduction of the transfer branch is to achieve the dual purposes of fault isolation and current transfer. By transferring the fault current to the transfer branch, the fault area can be isolated from the normal operating area, reducing the impact of the fault on the entire DC distribution network. At the same time, the design parameters of the transfer branch (such as the current carrying capacity, conduction time, etc.) are determined according to the fault current characteristics and protection requirements of the system to ensure that the fault current can be effectively carried after the main current branch is disconnected, and the relative stability of the power grid is maintained.

[0087] It can be seen that in this example, the circuit structure setting of the DC circuit breaker realizes the switching of the main and transfer branch states of the DC circuit breaker 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 a 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 is connected in series with the first equivalent inductor to form a first series circuit, the bidirectional solid-state switch module is connected in series with the second equivalent inductor to form a second series circuit, and the first series circuit is connected in parallel with the second series circuit.

[0089] Among them, the first equivalent inductance is used to be equivalent to the main current branch of the DC circuit breaker coupled to the DC distribution network, the second equivalent inductance is used to be equivalent to the transfer branch of the DC circuit breaker coupled to 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 an 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 The second equivalent inductance L COM The series connection 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 magnitude on the first series circuit is represented by i mb (i.e. the main current branch current), the current magnitude i in the second series circuit com (Transfer branch current). Before the DC circuit breaker is disconnected, 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 (that is, equivalent to the arc resistor R arc ), the transfer branch is turned on, and the power electronic switch can be equivalent to a resistor (that is, 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 resistance of the arc 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 ,opening process of the DC circuit breaker.

[0091] It can be seen that in this example, the circuit end constructs the equivalent circuit of the decoupled DC circuit breaker and realizes the electromagnetic transient simulation of the DC circuit breaker, clarifies the role of each component and the coupling relationship with the distribution network, and determines the arc resistance through the interactive end, which is conducive to 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 of the arc resistor to the current resistance parameter.

[0093] Among them, in this example, the technician can interact with the coupling interactive terminal through the server to set the 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 disconnection process of the DC circuit breaker due to the DC distribution network fault. The coupling interactive terminal can adjust the resistance of the arc resistor to the preset current resistance parameter according to the instruction, so as to accurately reproduce the impact of the arc resistance characteristics under different fault conditions, and then comprehensively test the performance of the DC circuit breaker under various fault conditions. The purpose of the coupling interactive terminal to implement control operations 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 start the protection action, so as to facilitate the observation and detection of key performance indicators such as the response speed and action accuracy of the circuit breaker under such abnormal conditions.

[0094] Compared with the traditional fault test of DC circuit breakers, the coupling interaction end in this example can flexibly and accurately control the resistance value of the arc resistor. The principle of controlling the arc resistance value is that the arc resistance has a huge impact on electrical parameters such as current and voltage during the opening and closing process of the DC circuit breaker. By changing its resistance value, the circuit environment under different fault severity can be simulated. For example, a smaller arc resistance value is similar to a minor fault, and the current change is relatively mild; a larger resistance value can simulate a serious fault, causing a sharp drop in current and a sharp rise in voltage, to observe whether the DC circuit breaker can effectively cut off the circuit and judge its arc extinguishing ability and voltage shock tolerance performance.

[0095] It can be seen that in this example, the server collaborates with the coupling interaction terminal, the fault instruction triggers switch switching and resistance adjustment, simulates fault scenarios, enhances the system's simulation capability for fault response, and improves the system's practicality and flexibility, and can realize online fault settings.

[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 values ​​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 shown in Figure 1 is shown in Figure 2, where 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 is 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 that performs electromagnetic transient simulation, and △t refers to the time step, that is, the electromagnetic transient model discretizes time and divides the time interval 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., the 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 (i.e. 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 at both ends of 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 the like 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 ≥ the total simulation time.

[0107] Among them, this step is a numerical value judgment step, which judges whether the superimposed simulation step is greater than or equal to the preset total simulation time. This step is the if-or-no branch of step S204 and the subsequent step of step S206. When the coupling interaction end determines that the superimposed simulation step is greater than or equal to the total simulation time, the simulation ends. When the coupling interaction end determines that the superimposed simulation step is less than the total simulation time, step S208 is executed.

[0108] For details about the concepts of simulation step length and total simulation duration, please refer to 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 the simulation step once; 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 ended, and stop data transmission between the circuit end and the multi-physical 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 principle. 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 ends within a reasonable simulation time range. For example, in each simulation step, the circuit end performs electromagnetic transient simulation and outputs dynamic current values ​​based on the current parameters, the multi-physics field end calculates the physical parameter values ​​based on boundary conditions, and the coupling interaction end performs corresponding parameter updates and transmissions. When the total simulation time is reached, the data transmission is terminated to ensure the integrity and rationality of the collaborative work of all parts of the entire fault test system, and to avoid meaningless data interaction and excessive consumption of computing resources. According to the simulation step, the data transmission between the circuit end and the multi-physics field end is stopped in time to avoid unnecessary data exchange and calculation, effectively saving the computer's computing resources, storage resources, and network bandwidth. Especially for complex multi-physics field coupling and large-scale circuit simulation scenarios, reasonable resource utilization can improve the operating efficiency of the entire fault test system, ensure that the system can run stably and quickly obtain effective simulation results. Among them, the total simulation time and simulation step setting make the entire simulation operation have a standardized process, which is convenient for repeated verification in different research scenarios and different personnel operations.

[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, which effectively controls the online simulation process, simulates the working status of the DC circuit breaker in different time stages, and improves the stability and coordination of the system in executing online simulation operations.

[0113] Step S208, superimposing a simulation step.

[0114] Among them, this step is that after the simulation software determines that the superimposed simulation step is less than the total simulation time, the simulation step is superimposed on the superimposed simulation step again, so as to internally time whether the online simulation operation of the DC circuit breaker is completed. And, after the execution of this step, based on the calculation results obtained in step S205 and step S206, the coupling interaction end and the circuit end will interact to perform the next online simulation operation, so that the accuracy of the online simulation of the DC circuit breaker is gradually improved, and the comprehensiveness of the fault test of the DC circuit breaker is improved.

[0115] In a possible embodiment, the coupling interaction end further includes a display screen device; the display screen device is used to display the 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] Exemplarily, when the display device displays the dynamic current value, the display device can display a current waveform, with time as the horizontal axis and the current size as the vertical axis, showing the curve of the current changing over time. The dynamic processes of the current rising, falling, and oscillating can be intuitively seen. For example, at the moment when the DC circuit breaker is disconnected, the current will drop sharply, and this change can be clearly shown through the waveform. And the coupling interaction end can determine the current peak value and the current effective value according to the change of the current value in 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 a 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 in the transient process, such as the oscillation frequency and damping condition of the circuit. This helps to 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, such as whether the circuit breaker can successfully cut off the fault current within the specified time, and whether overheating will occur due to excessive current under normal working conditions.

[0118] For example, when the current resistance parameter and admittance parameter of the arc corresponding to the display screen device are displayed, the display screen device can display the arc resistance value, that is, display the resistance of the arc at the current moment. The change of arc resistance will affect the current distribution and energy loss in the circuit, and its size is related to factors such as the temperature, length, and gas composition of the arc. And the display screen device can also display the arc admittance value, which is the reciprocal of the arc resistance. This parameter is used to measure the arc's ability to conduct current. The change in admittance value reflects the change in the arc's conductive properties. Through the display of the above content, researchers can understand the generation, development, and extinguishing process of the arc during the breaking process of the DC circuit breaker. For example, as the arc extinguishing process proceeds, the arc resistance will gradually increase, and the admittance will gradually decrease, and these parameters can be used to analyze parameters such as the equivalent impedance and power factor at the circuit end, and then analyze the stability of the circuit and the energy transmission efficiency.

[0119] It can be seen that in this example, the setting of the display screen device at the coupling interactive end enables it to intuitively present the simulation result values, which is convenient for researchers to view and analyze the changes in current, physical properties and arc parameters during the online simulation of the DC circuit breaker, and improves the practicality of the system in performing online simulation through visualization, which is convenient 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] Among them, the principle of setting the physical field of the electromagnetic field is that the electromagnetic field is one of the key physical fields in the scenario involving DC circuit breakers. When the current passes through the branches of the circuit breaker, a magnetic field is generated in the surrounding space. According to Ampere's loop law, there is a close relationship between current and magnetic field. For example, when the main flow branch is turned on, there will be a strong magnetic field distributed around the branch; when a fault occurs and the main flow branch is disconnected to generate an arc, the movement of charged particles in the arc plasma will also generate a complex electromagnetic field. The finite element model of the electromagnetic field can be used to solve the spatial distribution and time variation of physical quantities such as electric field intensity and magnetic field intensity, and then analyze the influence of electromagnetic force on the internal structure of the circuit breaker and the arc behavior. And, the principle of setting the physical field of the temperature field is that due to the thermal effect of the current, Joule heat will be generated in the conductive elements, especially in the main flow branch and the transfer branch. According to Joule's law, heat is generated when current passes through a conductor with resistance. This heat will cause the internal temperature of the circuit breaker to rise. The change of temperature field will affect the physical properties of the material. Through the finite element model of 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] Further, the principle of setting the finite element model of the physical field of the flow field is that the flow field plays an important role inside the circuit breaker, especially in the case of arc extinguishing process or gas insulation medium. For example, in the arc extinguishing chamber, the flow state of the gas will affect the cooling and extinguishing of the arc. The flow of gas can take away the 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 the flow rate and pressure of the gas, which is helpful to design more effective arc extinguishing devices and optimize gas insulation systems. And, the principle of setting the physical field of the stress field is that when the branch state of the circuit breaker changes (such as the main flow branch is disconnected to generate an arc), the internal structure of the circuit breaker will be subjected to different degrees of stress due to factors such as electromagnetic force and thermal expansion. According to the principles of material mechanics, the thermal expansion and electromagnetic force caused by temperature changes will cause strain and stress in the components. The finite element model of the stress field can predict the deformation of the structure, the stress concentration area, etc., provide a reference for the mechanical structure design of the circuit breaker, and ensure the mechanical reliability of the circuit breaker under various working conditions.

[0123] It can be seen that in this example, through the finite element model containing multiple physical fields, various physical phenomena involved in the operation and failure process of the DC circuit breaker can be fully considered. It is no longer limited to the analysis of a single physical field, but comprehensively considers the mutual coupling relationship between the electromagnetic field, temperature field, flow field and stress field, which can more realistically simulate the actual working conditions of the DC circuit breaker, provide a basis for accurately simulating its multi-physical field coupling behavior, and improve the comprehensiveness and accuracy of fault testing.

[0124] It can be seen that in the present application, the fault testing system for DC circuit breakers provided in the present 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 power distribution network, wherein a power 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 protection scope of this application.

[0127] Those skilled in the art can clearly understand that for the convenience and simplicity 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 embodiments of the present application, and should all be included in the protection scope 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-physical field end, wherein the circuit end is connected to the coupling interaction end, and the coupling interaction end is connected to the multi-physical field end; The circuit end is used to perform the current electromagnetic transient simulation on the DC circuit breaker through a preset electromagnetic transient simulation model to output a dynamic current value to the coupling interaction end, wherein the dynamic current value is the current value at the current moment, and 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 the current state; The multi-physics field terminal is used to determine the physical property parameter value at the current moment based on the finite element model of multiple preset physical fields and the dynamic boundary conditions, and the physical property parameter value at the current moment is 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 value at the current moment to the coupling interaction terminal; 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 the admittance parameter to the circuit end to indicate the next electromagnetic transient simulation.

2. The fault testing system for a 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 the 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 also 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 a DC circuit breaker according to claim 2, characterized in that: The coupling interaction end is also used for: Before the online simulation operation for the DC circuit breaker starts, a preset total simulation time and a simulation step length are obtained, 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 a 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, and the transfer branch is connected in parallel with the main current-carrying branch; Before the DC circuit breaker is disconnected, the main current-carrying 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 on state to the off state to generate the arc, and the transfer branch switches from the off state to the on state.

5. The fault testing system for a 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. 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. 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 a DC circuit breaker according to claim 5, characterized in that: The fault testing system for DC circuit breaker also includes a server; The server is used to send a fault instruction to the coupling interaction terminal; The coupling interaction end is also used to control the switch 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 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 ​​at both ends of the equivalent circuit of the DC circuit breaker, as well as 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 the Nouton equivalent current of the main current branch, and the second current value is the Nouton 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 the 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 comprises a fault testing system for a DC circuit breaker according to any one of claims 1 to 9.

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