Alternating current and direct current arc resistance model construction method, device and medium

Abstract

The invention discloses an alternating current and direct current arc resistance model construction method and device and a medium. The method comprises the steps that a basic module needed for constructing an alternating current and direct current arc resistance model is determined; connecting a diode with a leakage resistor in parallel to construct a leakage resistor module, and connecting the leakage resistor module with the basic module in series to determine a circuit structure corresponding to the arc model; wherein the leakage resistance module is used for simulating an arc corona discharge stage of an arc; acquiring arc data at a plurality of sampling moments, and calculating instantaneous arc resistance of arcing according to the arc data based on the differential equations corresponding to the basic modules; according to the instantaneous arc resistance and the arc data at the adjacent sampling moments, determining a proportionality coefficient corresponding to each basic module; and based on the circuit structure, according to the differential equations and the proportionality coefficients corresponding to the leakage resistance module and the basic module, constructing an arc model, and performing arc fault simulation through the arc model.

Description

Technical Field

[0001] The present application relates to the field of AC / DC hybrid power distribution, and specifically to a method, device, and medium for constructing an AC / DC arc resistance model. Background Art

[0002] With the widespread adoption of new energy power systems and power electronics, hybrid AC / DC power distribution scenarios are increasing. Series arc faults, due to their high concealment and destructiveness, have become a core threat to system security. Arc models can be divided into two types: impedance models and dynamic models. The impedance model calculates the equivalent impedance value of the arc. While traditional impedance models can simulate the dynamic conductivity changes and energy balance of the arc, their applicability is limited by model assumptions and parameter settings, and they have significant limitations under mixed AC / DC operating conditions. Dynamic models, including diode models, are only applicable when there is no time delay between the power supply voltage and arc current, and thus also have limitations.

[0003] However, the complexity of dynamic currents in renewable energy systems (such as AC harmonics superimposed on DC components and transient currents caused by high-frequency power electronic switching) makes it difficult for existing arc models to accurately describe the dynamic impedance characteristics and energy dissipation process of arcs. This is especially true for arc faults such as those occurring in photovoltaic system inverters, where existing fault detection algorithms have significant deficiencies in sensitivity and reliability. Therefore, establishing an effective simulation model for a wide range of dynamic currents has become a pressing issue. Summary of the Invention

[0004] In order to solve the above problems, this application proposes a method for constructing an AC / DC arc resistance model, including:

[0005] Determining basic modules required for constructing an AC / DC arc resistance model; wherein the basic modules include a first module for simulating an arc zero-crossing phase, a second module for simulating a high current steady-state phase, and a third module for simulating a nonlinear heat dissipation scenario;

[0006] Connecting a diode and a leakage resistor in parallel to construct a leakage resistor module, and connecting the leakage resistor module in series with the basic module to determine a circuit structure corresponding to the arc model; wherein the leakage resistor module is used to simulate the arc corona discharge stage of the arc;

[0007] Acquire arc data at multiple sampling moments, and calculate the instantaneous arc resistance of the arc according to the arc data based on the differential equations corresponding to the basic modules;

[0008] Determining a proportional coefficient corresponding to each basic module according to the instantaneous arc resistance and the arc data at adjacent sampling moments;

[0009] Based on the circuit structure, an arc model is constructed according to the differential equations and proportional coefficients corresponding to the leakage resistance module and the basic module, so as to perform arc fault simulation through the arc model.

[0010] In one implementation of the present application, before connecting the leakage resistance module where the leakage resistance is located in series with the basic module, the method further includes:

[0011] Connect the diode and the leakage resistor in parallel to build a leakage resistor module;

[0012] Determine the conduction threshold of the diode, and simulate the arc corona discharge stage of the arc through the leakage resistance module according to the arc current and whether the conduction threshold is met; wherein, when the leakage resistance is less than the conduction threshold, the arc belongs to the arc corona discharge stage.

[0013] In one implementation of the present application, the arc model is expressed as:

[0014] R arc =K1×R1+K2×R2+K3×R3+ε(-|i(t)|+I s )×R0

[0015] Among them, R arc represents the arc resistance, R1, R2 and R3 represent the instantaneous arc resistance corresponding to each basic module, ε(x) represents the first step function, i(t) represents the arc current, I s represents the conduction threshold, and R0 represents the leakage resistance value.

[0016] In one implementation of the present application, determining the circuit structure corresponding to the arc model specifically includes:

[0017] Connecting a switch module for controlling whether to connect to an arc fault into the circuit structure; wherein the switch module is controlled by a second step function;

[0018] By setting the step time of the second step function, the occurrence time of the arc fault is controlled when the arc fault simulation is performed using the arc model.

[0019] In one implementation of the present application, based on the differential equations corresponding to the basic modules and according to the arc data, calculating the instantaneous arc resistance of the arc specifically includes:

[0020] determining basic module parameters corresponding to the basic module according to the arc data;

[0021] Calculating the arc conductance corresponding to each sampling moment according to the arc data, and determining the arc time constant corresponding to the basic module according to the arc conductance;

[0022] Based on the differential equations corresponding to the basic modules, the instantaneous arc resistance of the arc is calculated according to the basic module parameters and the arc time constant.

[0023] In one implementation of the present application, the proportional coefficient corresponding to each basic module is determined according to the instantaneous arc resistance and the arc data at adjacent sampling moments, specifically including:

[0024] Determining a functional relationship between the actual arc resistance value and the instantaneous arc resistance at adjacent sampling moments according to a series proportional relationship between the basic modules;

[0025] The functional relationship is expressed as:

[0026] R arc_a =K1×R 1a +K2×R 2a +K3×R 3a

[0027] R arc_b =K1×R 1b +K2×R 2b +K3×R 3b

[0028] Among them, R arc_a and R arc_b represents the adjacent sampling time t a and t b The actual resistance value, K1, K2 and K3 represent the proportional coefficients corresponding to each basic module, R 1a 、R 2a and R 3a Respectively represent the basic modules at t a The instantaneous arc resistance at the moment, R 1b 、R 2b and R 3b Respectively represent the basic modules at t a The instantaneous arc resistance at the moment;

[0029] The actual resistance value is calculated based on the arc data, and the actual resistance value and the instantaneous arc resistance are substituted into the functional relationship to determine the proportional coefficient corresponding to each basic module; wherein the sum of the proportional coefficients is 1.

[0030] In one implementation of the present application, determining the basic module parameters corresponding to the basic module according to the arc data specifically includes:

[0031] The arc data includes the arc voltage and current for stable arcing, the minimum voltage and current required to maintain the arc, and the arc voltage and arc current collected at the sampling moment;

[0032] determining a dissipated power corresponding to the first module according to a product of the arc-stabilizing arcing voltage and the current, and using the dissipated power as a basic module parameter corresponding to the first module;

[0033] Using the arc stable burning voltage as a basic module parameter corresponding to the second module;

[0034] The minimum power required for the third module to maintain the arc is determined according to the product of the minimum voltage and the minimum current, and the minimum power is used as a basic module parameter corresponding to the third module.

[0035] In one implementation of the present application, based on the differential equations corresponding to the basic modules, according to the basic module parameters and the arc time constant, the instantaneous arc resistance of the arc is calculated, specifically including:

[0036] Determine the differential equations corresponding to each of the basic modules; wherein the differential equations corresponding to the basic modules are:

[0037]

[0038] Among them, g1, g2 and g3 represent the arc conductance corresponding to the first module, the second module and the third module respectively, τ1, τ2 and τ3 represent the arc time constant corresponding to the first module, the second module and the third module respectively, P loss represents the dissipated power, U arc Indicates the arc stable burning voltage, P m represents the minimum power, t is the sampling time, is the difference operator;

[0039] The instantaneous arc resistance of the arc in each basic module is calculated according to the basic module parameters and the arc time constant.

[0040] The present application provides an AC / DC arc resistance model construction device, comprising:

[0041] at least one processor;

[0042] and, a memory communicatively coupled to the at least one processor;

[0043] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method for constructing an AC / DC arc resistance model as described in any one of the above items.

[0044] An embodiment of the present application provides a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured to:

[0045] A method for constructing an AC / DC arc resistance model as described in any one of the above items.

[0046] The AC / DC arc resistance model construction method proposed in this application can bring the following beneficial effects:

[0047] Constructing a composite arc model based on various basic modules overcomes the limitations of traditional impedance and dynamic models in mixed AC / DC operating conditions. It effectively covers a wide range of arc current values ​​and enables high-fidelity simulation of complex operating conditions. Dynamically calculating differential equation parameters based on experimental data allows for precise matching of different arc fault scenarios by setting appropriate parameters. Incorporating the leakage resistance module's physical model to simulate the arc's initial discharge phase, fault simulation fully considers the characteristics of the arc's initial stage, improving the accuracy of arc simulation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0049] Figure 1 A schematic flow chart of a method for constructing an AC / DC arc resistance model provided in an embodiment of the present application;

[0050] Figure 2 A schematic diagram of a differential equation of a first module provided in an embodiment of the present application;

[0051] Figure 3 A schematic diagram of the circuit structure of a first module provided in an embodiment of the present application;

[0052] Figure 4 A schematic diagram of a differential equation of a second module provided in an embodiment of the present application;

[0053] Figure 5 A schematic diagram of the circuit structure of a second module provided in an embodiment of the present application;

[0054] Figure 6 A schematic diagram of a differential equation of a third module provided in an embodiment of the present application;

[0055] Figure 7 A schematic diagram of the circuit structure of a third module provided in an embodiment of the present application;

[0056] Figure 8 A schematic diagram of a leakage resistance module provided in an embodiment of the present application;

[0057] Figure 9 A schematic diagram of a diode module simulation provided in an embodiment of the present application;

[0058] Figure 10 A schematic diagram of an experimental measurement verification circuit provided in an embodiment of the present application;

[0059] Figure 11 A schematic diagram of a series arc drawing device provided in an embodiment of the present application;

[0060] Figure 12 A schematic diagram of the circuit structure of an arc model provided in an embodiment of the present application;

[0061] Figure 13 A schematic diagram of a simulation waveform of an AC arc simulation result provided in an embodiment of the present application;

[0062] Figure 14 A schematic diagram of a DC arc simulation result provided in an embodiment of the present application;

[0063] Figure 15 A schematic diagram of the structure of an AC / DC arc resistance model construction device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0064] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the specific embodiments of this application and the corresponding drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0065] The following describes in detail the technical solutions provided by various embodiments of the present application in conjunction with the accompanying drawings.

[0066] like Figure 1 As shown, an embodiment of the present application provides a method for constructing an AC / DC arc resistance model, comprising:

[0067] S101: Determine basic modules required for constructing an AC / DC arc resistance model; wherein the basic modules include a first module for simulating an arc zero-crossing phase, a second module for simulating a high current steady-state phase, and a third module for simulating a nonlinear heat dissipation scenario.

[0068] The modeling of DC series arcs is primarily based on the classical arc differential equation model. Commonly used basic models include Mayr, Cassie, Schwarz, and their improved parameters or equations. The Mayr model is only applicable to low-current stages (near zero-crossing points), with significant errors in the high-current region. The Cassie model is only applicable to high-current steady-state arcs, and its low-current zero-crossing behavior is inaccurate. The Schwarz model is used in nonlinear heat dissipation scenarios and introduces a dynamic term for heat dissipation power. However, parameter calibration relies more on arc voltage measurements (such as extracting Um from the volt-ampere characteristic curve), and it lacks sufficient response to high-frequency transient currents. In addition, there are some simplified practical models, such as using a diode series resistor to simulate the unidirectional conduction and voltage drop of an arc. However, this model is overly simple, and while computationally efficient, it lacks accuracy and is only suitable for quick analysis.

[0069] Based on the principle of conservation of energy, this embodiment of the present application proposes a composite arc simulation and analysis method. This method, based on the three basic modules mentioned above, constructs AC and DC arc resistance models for simulating arc faults. This overcomes the drawback that a single model cannot simulate the full life cycle characteristics of an arc. By combining modules, the arc model is constructed to reduce fault simulation errors. The basic modules include a first module for simulating the arc zero-crossing phase, a second module for simulating the high-current steady-state phase, and a third module for simulating nonlinear heat dissipation scenarios. The first module is the Mayr model, the second module is the Cassie model, and the third module is the Schwarz model.

[0070] The core of the first module is energy conservation, assuming that the energy stored in the arc is equal to the energy supplied to the arc P in and the dissipated energy P out The difference is equal, that is:

[0071]

[0072] This module simulates the energy dissipated from the arc gap as a constant. The energy dissipation depends on heat conduction and radial diffusion. In other words, the arc temperature changes with the radial distance from the arc axis and time. The arc impedance Z is:

[0073]

[0074] where Θ is the time constant, which depends on several parameters including the electrode size. out Approximately equal to P in When the arc is stable, the arc energy will no longer change. When the energy supplied by the circuit to the arc is greater than the energy dissipated by the arc (P in >P out ), the arc temperature will increase, thermal ionization will be strengthened, and the arc impedance Z will tend to decrease; when P in <P outWhen , the arc temperature will decrease, thermal ionization will weaken, and Z will tend to increase.

[0075] At low currents, the arc has not reached thermal saturation, and the plasma expansion effect at high currents is ignored. It can be assumed that the arc has the shape of a cylindrical gas channel with a constant diameter. At low currents, heat dissipation dominates, and the Joule heat power P in =i 2 (t)g(t), where g(t) represents the resistance and conductance, R(t) is the resistance, g(t)=1 / R(t), and the heat dissipation power P out At the same level, the energy balance equation directly reflects the arc's "thermal collapse" or "maintenance" process. At low currents, the arc volume and temperature gradient are small, and the convection and radiation heat dissipation power can be approximated as a constant value P that is independent of the current. out =P loss , P loss Represents the dissipated power. At this time, the arc has not reached the thermal saturation state, and the energy storage linear assumption is approximately valid, that is, the energy storage is proportional to the conductivity: E stored =τP loss g(t),E stored represents the arc energy storage, and τ is the arc time constant.

[0076] Therefore, the differential equation corresponding to the first module is:

[0077]

[0078] Among them, g1 represents the arc conductance corresponding to the first module, τ1 represents the arc time constant corresponding to the first module, is the difference operator.

[0079] At low currents, the arc conductivity g(t) is extremely low (resistance is extremely high), and a small change in input power will cause significant fluctuations in g(t). The nonlinear term i in the equation 2 (t) / P loss It is sensitive to the initial state and can accurately capture the dynamics of arc breakdown or extinction.

[0080] Based on this, the differential equation diagram of the first module is as follows Figure 2 As shown, |u| 2 Indicates i 2 (t), which is related to P loss That is, after w is triggered and subtracted from g(t), it is subtracted from the time constant tao1. Multiplying together, we get Through the integrator right Perform time integration and output the conductivity g(t) at the current moment. The initial condition of the integration is provided by the initial value of g10 conductivity (i.e., the conductivity g(0) at t=0). The g(t) output by the integrator will be fed back to the subtraction module and continuously participate in The final output is (Right now ), that is, R1. By multiplying R1 and the proportional coefficient K1 corresponding to the first module (i.e., module 1), the module proportion corresponding to the first module in the arc model can be obtained.

[0081] like Figure 3 The circuit structure diagram of the first module shown uses a variable resistor to control the arc resistance. The large resistor (1×109Ω) is connected in parallel. This is because the resistance of the variable resistor is controlled by the circuit current. The output module is in the form of a current source. When multiple resistors are connected in series, the circuit model may be incompatible.

[0082] The core assumption of the second module is that the arc voltage remains constant in steady state. The energy balance equation (1) describes the dynamic changes in arc conductivity, making it suitable for analyzing the negative resistance characteristics and dynamic response of high-current arcs. A high-current steady-state arc can be viewed as a well-defined cylindrical gas channel with a uniform temperature distribution across its cross section and a relatively large impedance outside its diameter. As the current through this arc channel changes, its diameter also changes, but the arc temperature remains constant in both space and time.

[0083] In a power frequency current wave, the arc voltage gradient remains constant. Therefore, the energy and the rate of energy dissipation are proportional to the change in the arc column cross section. Energy dissipation is caused by airflow or airflow-related arc column deformation processes. The arc impedance Z is:

[0084]

[0085] Where V is the loop voltage.

[0086] Based on plasma stability, the arc is in a fully ionized state at high current, and the voltage U arc It is determined by the plasma characteristics (such as gas type and pressure), rather than heat dissipation. Arc stable arc voltage U arc Approximately a constant that has nothing to do with the current, the input power P in =i(t)·U arc .

[0087] Assume that the heat dissipation power is related to the arc volume, that is, P diss =k·A(t), where k represents the heat dissipation volume ratio coefficient, P diss is the heat dissipation power, A(t) is the arc cross-sectional area, and further assumes that the current density Constant, substituting into Simplifying assumptions, let but K represents the heat dissipation coefficient. Assuming that the stored energy is related to the conductivity g(t), where τ is the arc time constant.

[0088] Assume that the arc voltage is constant in steady state but And the steady-state condition can be determined The differential equation corresponding to the second module is:

[0089]

[0090] Among them, g2 represents the arc conductance corresponding to the first module, τ2 represents the arc time constant corresponding to the first module, U arc Indicates the arc stable burning voltage.

[0091] Based on this, the differential equation diagram of the second module is as follows Figure 4 As shown, |u| 2 Indicates i 2 (t) and U 2 arc , U 2 arc After multiplication with g(t), 2 (t) is divided and obtained Then with the time constant tao2, Multiplying together, we get Through the integrator right Perform time integration and output the conductivity g(t) at the current moment. The initial condition of the integration is provided by the initial value of g20 (i.e. the conductivity g(0) at t=0). The g(t) output by the integrator will be fed back to the subtraction module and continuously participate in The final output is (Right now ), which is R2. Since K1+K2+K3=1, by multiplying R2 by K2 derived from K1 and K3, the module ratio corresponding to the second module (i.e., module 2) in the arc model can be obtained.

[0092] like Figure 5 The circuit structure diagram of the second module shown uses a variable resistor to control the arc resistance, and a large resistor (1×109Ω) is connected in parallel.

[0093] The third module is suitable for AC / DC hybrid systems and nonlinear heat dissipation scenarios. By introducing the concept of dynamic heat dissipation power, it significantly improves the accuracy of the arc model in a wide current range and complex heat dissipation scenarios, and constructs a more general differential equation:

[0094]

[0095] Among them, g3 represents the arc conductance corresponding to the third module, τ3 represents the arc time constant corresponding to the third module, P m Indicates minimum power.

[0096] Based on this, the differential equation diagram of the third module is as follows Figure 6 As shown, |u| 2 Indicates i 2 (t), which is related to P m That is, after w is triggered and subtracted from g(t), it is subtracted from the time constant tao3. Multiplying together, we get Through the integrator right Perform time integration and output the conductivity g(t) at the current moment. The initial condition of the integration is provided by the initial value of the conductivity g30 (i.e. the conductivity g(0) at t=0). The g(t) output by the integrator will be fed back to the subtraction module and continuously participate in The final output is (Right now ), that is, R3. By multiplying R1 and the proportional coefficient K3 corresponding to the third module, the module proportion corresponding to the third module (i.e., module 3) in the arc model can be obtained.

[0097] like Figure 7 The circuit structure diagram of the third module shown is similar to the first and second modules, using a variable resistor to control the arc resistance and a large resistor (1×109Ω) in parallel.

[0098] S102: Connecting a diode and a leakage resistor in parallel to construct a leakage resistor module, and connecting the leakage resistor module and the basic module in series to determine a circuit structure corresponding to the arc model; wherein the leakage resistor module is used to simulate the arc corona discharge stage of the arc.

[0099] The above-mentioned basic module is usually used to simulate the main discharge stage of the arc, when the arc is in a strong ionization state and has the characteristics of low resistance and high conductivity. The embodiment of the present application introduces a leakage resistance module where the leakage resistance is located, which is specifically used to simulate the corona discharge stage of the arc (such as the weak ionization transition stage or edge leakage phenomenon before the arc is extinguished). At this time, the arc is in a weak ionization state, the resistance is high, and the current contains part of the leakage component passing through the surrounding medium. After the leakage resistance module and the basic module are connected in series, the circuit structure corresponding to the arc model is obtained, which can simultaneously reflect the low-resistance conductive characteristics of the main arc and the high-resistance leakage characteristics of the corona stage, covering the full life cycle of the arc from strong ionization to weak ionization.

[0100] Before connecting the leakage resistor module, where the leakage resistor resides, in series with the base module, the specific structure and connection principle of the leakage resistor module must be determined. First, a diode and leakage resistor are connected in parallel to construct the leakage resistor module. Then, the diode's conduction threshold is determined. Based on the arc current and whether the conduction threshold is met, the leakage resistor module simulates the arc corona discharge stage. When the leakage resistor is less than the conduction threshold, the arc is in the arc corona discharge stage.

[0101] Specifically, Figure 8 This is the schematic diagram of the leakage resistance module, such as Figure 8 As shown, when the arc current is -I s to I s Between , the diode does not conduct, but within this range, corona discharge occurs. The corona current is very low compared to the arc current, and this discharge is approximated as a current leakage that heats the external environment, and is considered to be purely resistive. The discharge path is through the parallel resistor with a resistance of 1Ω. The diode in the figure should not be regarded as a traditional diode with a voltage threshold, but as a current diode with a current threshold (I s ), the conduction threshold represents the transition between corona discharge and arc discharge. When simulating the leakage resistance module through Simulink, the diode module simulation diagram is as follows Figure 9 As shown in the figure, the simulation in Simulink uses a standard diode connected in series with a variable resistor that changes linearly with the current passing through it to simulate the current threshold diode, and at the same time adds a delay module to prevent the result from not converging.

[0102] S103: Obtain arc data at multiple sampling moments, and calculate the instantaneous arc resistance of the arc based on the arc data based on the differential equations corresponding to each basic module.

[0103] The arc test is carried out on the photovoltaic system inverter to obtain arc data at multiple sampling moments, with the interval between adjacent sampling moments less than 0.1s. The arc data includes the arc stable arc voltage U arc and current I arc , Minimum voltage U required to maintain the arc m and minimum current I m , as well as the arc voltage u(t) and arc current i(t) collected at the sampling moment. Based on the differential equations corresponding to the above basic modules and these arc data, the instantaneous arc resistance of the arc can be calculated.

[0104] First, according to the arc data, the basic module parameters corresponding to the basic module are determined.

[0105] Specifically, the power dissipation corresponding to the first module is determined based on the product of the arc stabilization voltage and current, and the power dissipation is used as the basic module parameter corresponding to the first module. The arc stabilization voltage is used as the basic module parameter corresponding to the second module. In addition, the minimum power required to maintain the arc in the third module is determined based on the product of the minimum voltage and the minimum current, and the minimum power is used as the basic module parameter corresponding to the third module.

[0106] Then, the arc conductance corresponding to each sampling moment is calculated according to the arc data, and the arc time constant corresponding to the basic module is determined according to the arc conductance.

[0107] Specifically, since arc conductance is the inverse of instantaneous arc resistance, the arc conductance g(t) corresponding to the sampling moment can be obtained by calculating the ratio between arc current and arc voltage at each sampling moment based on the arc data collected above. loss 、U arc and P m Based on the arc data i(t) and arc conductance g(t), the known parameter values ​​are substituted into formulas (4)(7)(9) to calculate the arc time constants τ1, τ2 and τ3 corresponding to each basic module at each sampling moment.

[0108] Finally, based on the differential equations corresponding to each basic module, the instantaneous arc resistance of the arc is calculated according to the basic module parameters and the arc time constant.

[0109] All parameters in the differential equations for the basic module are known. Substituting the basic module parameters and the arc time constant into the above differential equations can calculate the predicted arc conductances g1(t), g2(t), and g3(t). Based on the inverse relationship between arc conductance and instantaneous arc resistance, the instantaneous arc resistance R(t) can be calculated accordingly.

[0110] S104: Determine the proportional coefficient corresponding to each basic module according to the instantaneous arc resistance and arc data at adjacent sampling moments.

[0111] In the process from arc generation to extinction, there are obvious differences in the resistance characteristics of each stage. By setting the proportional coefficient for each basic module, the arc model can track the transformation of the arc state in real time. At the same time, by adjusting the proportional coefficient to adjust the proportion of different modules, different arc resistances can be simulated.

[0112] When calculating the proportional coefficient of each basic module, it is first necessary to determine the functional relationship between the actual arc resistance value and the instantaneous arc resistance at adjacent sampling moments based on the series proportional relationship between the basic modules, that is:

[0113] R arc_a=K1×R 1a +K2×R 2a +K3×R 3a (10)

[0114] R arc_b =K1×R 1b +K2×R 2b +K3×R 3b (11)

[0115] Among them, R arc_a and R arc_b represents the adjacent sampling time t a and t b The actual resistance value, K1, K2 and K3 represent the proportional coefficients corresponding to each basic module, R 1a 、R 2a and R 3a Respectively represent the basic modules at t a The instantaneous arc resistance at the moment, R 1b 、R 2b and R 3b Respectively represent the basic modules at t a The instantaneous arc resistance at the moment.

[0116] The arc model is derived from the series connection of each basic module. The arc resistance value obtained by directly sampling the arc model is equivalent to the calculated sum of the instantaneous arc resistances corresponding to the three basic modules after proportional distribution. Therefore, the above process expresses the actual arc resistance value at adjacent sampling moments as the sum of the instantaneous arc resistances corresponding to each basic module based on the series proportional relationship between the basic modules, thereby obtaining a functional relationship between the actual resistance value and the instantaneous arc resistance.

[0117] Next, based on this functional relationship, the proportionality coefficients are solved. Since the sum of the proportionality coefficients is 1, all values ​​can be solved based on knowing two proportionality coefficients. Therefore, only the instantaneous arc resistance at two adjacent moments and the measured actual resistance value are needed to determine the proportionality coefficient corresponding to each basic module. The actual resistance value can be calculated from the ratio between the arc voltage and arc current in the arc data.

[0118] In the embodiment of the present application, the basic modules are divided into different physical processes of arc discharge, and the complex physical process of the arc is decomposed into basic units that can be described independently. Then, dynamic combination is achieved through proportional coefficients, which effectively improves the adaptability of the model to the entire life cycle of the arc, and significantly enhances the simulation accuracy and engineering practicality under complex working conditions in power system simulation.

[0119] S105: Based on the circuit structure, an arc model is constructed according to the differential equations and proportional coefficients corresponding to the leakage resistance module and the basic module, so as to perform arc fault simulation through the arc model.

[0120] After clarifying the proportional coefficients corresponding to each basic module, based on the circuit structure constructed above, an arc model can be constructed according to the differential equations and proportional coefficients corresponding to the leakage resistance module and basic modules. The arc model can be used for arc fault simulation, including AC series arc obstacles and DC series arc obstacles that may occur in photovoltaic system inverters.

[0121] The arc model is expressed as:

[0122] R arc =K1×R1+K2×R2+K3×R3+ε(-|i(t)|+I s )×R0(13)

[0123] Among them, R arc represents the arc resistance, R1, R2 and R3 represent the instantaneous arc resistance corresponding to each basic module, ε(x) represents the first step function, i(t) represents the arc current, I s represents the conduction threshold, and R0 represents the leakage resistance value.

[0124] The first step function is 0 when x<0, and the leakage resistance module is not connected. When x>0, the first step function is 1, and i(t) is at -I s to I s Between x and x, a leakage resistance module is connected to the arc model to simulate the corona discharge stage at the beginning of the arc. At x = 0, the first step function is 1 / 2. This first step function can control the magnitude of the fault resistance connected to the arc model.

[0125] It should be noted that the arc model's circuit structure also includes a switch module for controlling whether to connect to an arc fault. This switch module allows for customizing the arc occurrence time. Specifically, the switch module is controlled by a second step function. By setting the step time of the second step function, the second step function can jump from 0 to 1 within a certain period of time, thereby maintaining the entire circuit structure in a connected state. The basic modules and the leakage resistance module serve as fault resistances to simulate the connection of an arc fault. Thus, when simulating an arc fault using the arc model, the step time of the second step function can be used to control the arc fault occurrence time.

[0126] Based on the known proportional coefficients of each basic module, appropriate parameters can be set according to different arc fault conditions to simulate different arc fault conditions. The following is a specific experimental verification plan:

[0127] Figure 10This is a schematic diagram of an experimental measurement verification circuit provided in an embodiment of the present application. Figure 11 A schematic diagram of a series arc drawing device provided in an embodiment of the present application. The experimental circuit includes an AC / DC power supply, a load, a discharge electrode, and a sensing (voltage, current) part, which is connected to the PC end through a digital oscilloscope to obtain the waveform. The discharge electrode part includes a moving electrode, a fixed electrode, a terminal, a stepping electrode, a base and a caliper. Connect the circuit before the experiment starts, start the stepping electrode at the moment of the simulated series arc, draw the arc, and record the arc voltage u(t) and arc current i(t) collected at the sampling time t, where the time interval between adjacent sampling is less than 0.1s.

[0128] The arc model is constructed as follows Figure 12 As shown in the figure, the arc model consists of three modules for solving differential equations related to arc resistance, a leakage resistance module, and a second step function control switch module that controls the fault occurrence time. The module for solving differential equations to control the variable resistor consists of three submodules: the first module for the zero-crossing phase of the AC arc, the second module for high-current steady-state arcs, and the third module for arcs in nonlinear heat dissipation scenarios. The leakage resistance module has three branches that simulate the corona discharge at the beginning of the arc.

[0129] Based on the experimental data, the simulation parameters are calculated as shown in Table 1:

[0130] Table 1

[0131]

[0132]

[0133] Based on the simulation parameters in Table 1, arc fault simulation is performed. When the voltage is 220V and 50Hz, the AC arc simulation result waveform is as follows: Figure 13 As shown, the voltage and current waveforms are both periodically changing curves. The voltage waveform shows certain fluctuations on the time axis, the current waveform has obvious peaks, and the voltage waveform is relatively stable as a whole.

[0134] When the power supply is 100V DC, the DC arc simulation results are as follows: Figure 14 As shown, the voltage rises to a stable state and the current gradually decreases to a stable state.

[0135] The above are embodiments of the method proposed in this application. Based on the same idea, some embodiments of this application also provide devices and non-volatile computer storage media corresponding to the above methods.

[0136] Figure 15 This is a schematic diagram of the structure of an AC / DC arc resistance model building device provided in an embodiment of the present application. Figure 15 Shown, including:

[0137] at least one processor; and,

[0138] at least one processor communicatively connected to a memory; wherein,

[0139] The memory stores instructions that can be executed by at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method for constructing an AC / DC arc resistance model as described in any one of the above items.

[0140] An embodiment of the present application provides a non-volatile computer storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured as follows:

[0141] A method for constructing an AC / DC arc resistance model as described in any one of the above items.

[0142] The various embodiments in this application are described in a progressive manner. Similar portions between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the device and medium embodiments are generally similar to the method embodiments, so their descriptions are relatively simple. For relevant portions, refer to the descriptions of the method embodiments.

[0143] The devices and media provided in the embodiments of the present application correspond one-to-one to the methods. Therefore, the devices and media also have similar beneficial technical effects to their corresponding methods. Since the beneficial technical effects of the methods have been described in detail above, the beneficial technical effects of the devices and media will not be repeated here.

[0144] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0145] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0146] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0147] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0148] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0149] Memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

[0150] Computer-readable media includes permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0151] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0152] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for constructing an AC / DC arc resistance model, characterized in that: The method comprises: Determining basic modules required for constructing an AC / DC arc resistance model; wherein the basic modules include a first module for simulating an arc zero-crossing phase, a second module for simulating a high current steady-state phase, and a third module for simulating a nonlinear heat dissipation scenario; Connecting a diode and a leakage resistor in parallel to construct a leakage resistor module, and connecting the leakage resistor module in series with the basic module to determine a circuit structure corresponding to the arc model; wherein the leakage resistor module is used to simulate the arc corona discharge stage of the arc; Acquire arc data at multiple sampling moments, and calculate the instantaneous arc resistance of the arc according to the arc data based on the differential equations corresponding to the basic modules; Determining a proportional coefficient corresponding to each basic module according to the instantaneous arc resistance and the arc data at adjacent sampling moments; Based on the circuit structure, an arc model is constructed according to the differential equations and proportional coefficients corresponding to the leakage resistance module and the basic module, so as to perform arc fault simulation through the arc model.

2. The method for constructing an AC / DC arc resistance model according to claim 1, wherein: Connect the diode and the leakage resistor in parallel to build a leakage resistor module, which includes: Connect the diode and the leakage resistor in parallel to build a leakage resistor module; Determine the conduction threshold of the diode, and simulate the arc corona discharge stage of the arc through the leakage resistance module according to the arc current and whether the conduction threshold is met; wherein, when the leakage resistance is less than the conduction threshold, the arc belongs to the arc corona discharge stage.

3. The method for constructing an AC / DC arc resistance model according to claim 2, wherein: The arc model is expressed as: R arc =K1×R1+K2×R2+K3×R3+ε(-|i(t)|+I s )×R0 Among them, R arc represents the arc resistance, R1, R2 and R3 represent the instantaneous arc resistance corresponding to each basic module, ε(x) represents the first step function, i(t) represents the arc current, I s represents the conduction threshold, and R0 represents the leakage resistance value.

4. The method for constructing an AC / DC arc resistance model according to claim 3, wherein: Determine the circuit structure corresponding to the arc model, including: Connecting a switch module for controlling whether to connect to an arc fault into the circuit structure; wherein the switch module is controlled by a second step function; By setting the step time of the second step function, the occurrence time of the arc fault is controlled when the arc fault simulation is performed using the arc model.

5. The method for constructing an AC / DC arc resistance model according to claim 1, wherein: Based on the differential equations corresponding to the basic modules and according to the arc data, the instantaneous arc resistance of the arc is calculated, specifically including: determining basic module parameters corresponding to the basic module according to the arc data; Calculating the arc conductance corresponding to each sampling moment according to the arc data, and determining the arc time constant corresponding to the basic module according to the arc conductance; Based on the differential equations corresponding to the basic modules, the instantaneous arc resistance of the arc is calculated according to the basic module parameters and the arc time constant.

6. The method for constructing an AC / DC arc resistance model according to claim 1, wherein: Determining the proportional coefficient corresponding to each basic module according to the instantaneous arc resistance and the arc data at adjacent sampling moments, specifically including: Determining a functional relationship between the actual arc resistance and the instantaneous arc resistance at adjacent sampling moments based on a series proportional relationship between the basic modules; The functional relationship is expressed as: R arc_a =K1×R 1a +K2×R 2a +K3×R 3a R arc_b =K1×R 1b +K2×R 2b +K3×R 3b Among them, R arc_a and R arc_b represents the adjacent sampling time t a and t b The actual resistance value, K1, K2 and K3 represent the proportional coefficients corresponding to each basic module, R 1a 、R 2a and R 3a Respectively represent the basic modules at t a The instantaneous arc resistance at the moment, R 1b 、R 2b and R 3b Respectively represent the basic modules at t a The instantaneous arc resistance at the moment; The actual resistance value is calculated based on the arc data, and the actual resistance value and the instantaneous arc resistance are substituted into the functional relationship to determine the proportional coefficient corresponding to each basic module; wherein the sum of the proportional coefficients is 1.

7. The method for constructing an AC / DC arc resistance model according to claim 5, wherein: Determining basic module parameters corresponding to the basic module according to the arc data, specifically including: The arc data includes the arc voltage and current for stable arcing, the minimum voltage and current required to maintain the arc, and the arc voltage and arc current collected at the sampling moment; determining a dissipated power corresponding to the first module according to a product of the arc-stabilizing arcing voltage and the current, and using the dissipated power as a basic module parameter corresponding to the first module; Using the arc stable burning voltage as a basic module parameter corresponding to the second module; The minimum power required for the third module to maintain the arc is determined according to the product of the minimum voltage and the minimum current, and the minimum power is used as a basic module parameter corresponding to the third module.

8. The method for constructing an AC / DC arc resistance model according to claim 5, wherein: Based on the differential equations corresponding to the basic modules, according to the basic module parameters and the arc time constant, the instantaneous arc resistance of the arc is calculated, specifically including: Determine the differential equations corresponding to each of the basic modules; wherein the differential equations corresponding to the basic modules are: Among them, g1, g2 and g3 represent the arc conductance corresponding to the first module, the second module and the third module respectively, τ1, τ2 and τ3 represent the arc time constant corresponding to the first module, the second module and the third module respectively, P loss represents the dissipated power, U arc Indicates the arc stable burning voltage, P m represents the minimum power, t is the sampling time, is the difference operator; The instantaneous arc resistance of the arc in each basic module is calculated according to the basic module parameters and the arc time constant.

9. An AC / DC arc resistance model construction device, characterized in that: The device comprises: at least one processor; and, a memory communicatively coupled to the at least one processor; The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method for constructing an AC / DC arc resistance model as described in any one of claims 1 to 8.

10. A non-volatile computer storage medium storing computer executable instructions, characterized in that: The computer executable instructions are configured to: A method for constructing an AC / DC arc resistance model according to any one of claims 1 to 8.

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