An equivalent method and system for matching the short circuit current root mean square of an induction motor

Abstract

The application discloses an equivalent method and system for matching short-circuit current effective value of an induction motor, wherein the method comprises the following steps: determining multiple scenes of different power grid load compositions in a target area; establishing an induction motor detailed model and an induction motor equivalent model under the multiple scenes; setting a fault point for the induction motor detailed model and the induction motor equivalent model; obtaining standard alternating current components of short-circuit current generated by faults under each scene through the induction motor detailed model; obtaining comparative alternating current components of short-circuit current generated by faults under each scene through the induction motor equivalent model; matching the standard alternating current components and the comparative alternating current components under each scene until the absolute value of the difference percentage of the comparative alternating current components and the standard alternating current components is less than a preset threshold value, and recording the proportion of the induction motor in the induction motor equivalent model under each scene; and determining the equivalent proportion of the induction motor in the target area based on the recorded proportion of the induction motor under each scene.

Description

Technical Field

[0001] This invention relates to the fields of power system planning and operation technology, and more specifically, to an equivalent method and system for providing effective short-circuit current matching for an induction motor. Background Technology

[0002] In power system planning, design, and operation control, short-circuit current calculations are required for selecting system equipment capacity parameters, setting protection device settings, and arranging operating modes. The results of these calculations significantly impact the balance between system safety and economic efficiency. If the calculated result is too high, larger capacity switchgear needs to be selected, increasing investment; it may also cause short-circuit level assessments at many sites to exceed limits, necessitating additional current-limiting measures, further increasing investment and potentially reducing system reliability. Conversely, if the calculated result is too low, while initial equipment investment may be reduced, circuit breaker equipment may face insufficient breaking capacity, affecting equipment and system safety.

[0003] With the development of the power grid, the high short-circuit current in load center areas has become a global trend. For a long time, there has been inconsistency in the short-circuit current calculation boundaries between different decision-making departments. Different boundary conditions result in significantly different calculation results, making decision-making difficult. One key boundary condition is how to account for induction motors in the distribution network. Induction motors contribute short-circuit current during system short circuits. The proportion of induction motor loads varies significantly across different regions, and the contribution characteristics of induction motors to short-circuit current differ significantly depending on their type and voltage level. Furthermore, the sheer number of nodes and branches in the distribution network makes full-voltage-level modeling of the distribution network virtually impossible. When calculating and analyzing the main power grid, my country's power system planning and operation departments typically equate the load to a 110 kV bus. Short-circuit current calculations based on electromechanical transient simulation data and models directly consider the contribution of induction motors as a summation ratio, leading to overestimation of their contribution.

[0004] To address this situation, existing technology 1, "An Equivalent Modeling Method for the Contribution of Short-Circuit Current by Induction Motors in Distribution Networks," proposes a method to more accurately calculate the short-circuit current level of a region (province) by changing the proportion of induction motors in the total load, without altering the basic algorithm for short-circuit current and the fundamental data structure of electromechanical transients. Existing technology 1 is the first to propose a method for accurately simulating the short-circuit current provided by induction motors in distribution networks to the main power grid.

[0005] Existing technology 2, "A Substation-Level Load Modeling Method for Accurately Calculating Short-Circuit Current", proposes an accurate simulation method for the short-circuit current provided by the induction motor load of a specific substation.

[0006] The characteristic value for short-circuit current calculation is the initial effective value I of the periodic component of the short-circuit current.k ,satisfy In the detailed model of the induction motor in the distribution network, κ is 1.8 or 1.9.

[0007] In existing technologies 1 and 2, the consistency matching method for the short-circuit current provided by the induction motor in the equivalent model and detailed model of the distribution network is the short-circuit current peak value i. p Peak matching or full waveform matching methods are used. Peak matching does not require adjusting the induction motor model parameters in electromechanical transient simulation, making it convenient to apply. However, it is suitable for matching when the attenuation characteristics of the detailed model and the equivalent model of the induction motor in the distribution network are basically consistent. If the attenuation characteristics of the equivalent induction motor model differ significantly from the detailed model, i.e., κ is no longer close to 1.8 or 1.9, using the peak matching method will lead to errors in the matching result, specifically in the I” value. k The significant discrepancies lead to inaccurate short-circuit current calculations. While the full waveform matching method provides accurate simulation results, it requires altering various parameters of the equivalent induction motor in the electromechanical transient simulation model. Furthermore, different parameters may be used for each station, imposing a substantial workload on simulation analysts and hindering practical engineering applications.

[0008] Therefore, further research is needed on practical engineering methods to accurately simulate the short-circuit current provided by induction motors in power distribution networks. Summary of the Invention

[0009] The present invention provides an equivalent method and system for matching the effective value of short-circuit current provided by an induction motor, so as to solve the problem of how to match the effective value of short-circuit current provided by an induction motor.

[0010] To address the above problems, this invention provides an equivalent method for matching the effective value of short-circuit current in an induction motor, the method comprising:

[0011] Identify multiple scenarios involving different power grid loads in the target area;

[0012] Detailed models and equivalent models of induction motors are established for multiple scenarios; and fault points are set for the detailed models and equivalent models of induction motors.

[0013] The standard AC component of the fault-generated short-circuit current under various scenarios is obtained through the detailed model of the induction motor; the comparative AC component of the fault-generated short-circuit current under various scenarios is obtained through the equivalent model of the induction motor.

[0014] The standard AC component and the initial effective value of the comparison AC component in each scenario are matched until the absolute value of the percentage difference between the comparison AC component and the standard AC component is less than a preset threshold. Then, the proportion of the induction motor in the equivalent model of the induction motor in each scenario is recorded.

[0015] Based on the recorded proportions of induction motors in each scene, the equivalent proportion of induction motors in the target area is determined.

[0016] Preferably, before establishing detailed models and equivalent models of induction motors under multiple scenarios, the method further includes:

[0017] Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

[0018] Preferably, the establishment of detailed models and equivalent models of induction motors under multiple scenarios includes:

[0019] When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

[0020] Preferably, setting fault points in the detailed model and equivalent model of the induction motor includes:

[0021] The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

[0022] Preferably, wherein:

[0023] The instantaneous value of the short-circuit current is expressed as:

[0024]

[0025] In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant.

[0026] make

[0027] The instantaneous value of the short-circuit current can be simplified as follows:

[0028]

[0029] In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3):

[0030]

[0031] In equation (3), f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; ID0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component.

[0032] The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 Given the AC component decay time constant τ1 and the DC component decay time constant τ2, determine the DC and AC components of the short-circuit current.

[0033] Based on another aspect of the present invention, the present invention provides an equivalent system for providing short-circuit current RMS matching for an induction motor, the system comprising:

[0034] The initial unit is used to determine multiple scenarios based on different power grid loads in the target area;

[0035] A model building unit is used to build detailed models and equivalent models of induction motors under multiple scenarios; and to set fault points for the detailed models and equivalent models of induction motors.

[0036] The acquisition unit is used to acquire the standard AC component of the fault-generated short-circuit current under various scenarios through the detailed model of the induction motor; and to acquire the comparative AC component of the fault-generated short-circuit current under various scenarios through the equivalent model of the induction motor.

[0037] The execution unit is used to match the initial effective value of the standard AC component and the comparison AC component in each scenario until the absolute value of the percentage difference between the comparison AC component and the standard AC component is less than a preset threshold, and then record the proportion of the induction motor in the equivalent model of the induction motor in each scenario.

[0038] The result unit is used to determine the equivalent proportion of induction motors in the target area based on the recorded proportions of induction motors in each scene.

[0039] Preferably, before establishing the detailed model and equivalent model of the induction motor under multiple scenarios, the initial unit is further used for:

[0040] Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

[0041] Preferably, the establishing unit is used to establish detailed models and equivalent models of induction motors under multiple scenarios, and is also used to:

[0042] When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

[0043] Preferably, the establishing unit is used to set fault points for the detailed model and equivalent model of the induction motor, and is also used to:

[0044] The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

[0045] Preferably, wherein:

[0046] The instantaneous value of the short-circuit current is expressed as:

[0047]

[0048] In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant.

[0049] make

[0050] The instantaneous value of the short-circuit current can be simplified as follows:

[0051]

[0052] In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3):

[0053]

[0054] In equation (3), I” k φ is the initial effective value of the periodic component of the short-circuit current; f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component.

[0055] The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 Given the AC component decay time constant τ1 and the DC component decay time constant τ2, determine the DC and AC components of the short-circuit current.

[0056] According to another aspect of the present invention, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program for executing an equivalent method for providing effective short-circuit current matching for an induction motor.

[0057] According to another aspect of the present invention, the present invention provides an electronic device, characterized in that the electronic device comprises: a processor and a memory; wherein,

[0058] The memory is used to store the processor-executable instructions;

[0059] The processor is configured to read the executable instructions from the memory and execute the instructions to implement an equivalent method for providing effective short-circuit current matching for an induction motor.

[0060] This invention provides an equivalent method and system for matching the effective value of short-circuit current provided by an induction motor. The method includes: determining multiple scenarios with different power grid loads in a target area; establishing detailed models and equivalent models of induction motors in multiple scenarios; setting fault points in the detailed and equivalent models of induction motors; obtaining the standard AC component of the short-circuit current generated by the fault in each scenario through the detailed model of the induction motor; obtaining the comparative AC component of the short-circuit current generated by the fault in each scenario through the equivalent model of the induction motor; matching the initial effective values ​​of the standard AC component and the comparative AC component in each scenario until the absolute value of the percentage difference between the comparative AC component and the standard AC component is less than a preset threshold; recording the proportion of induction motors in the equivalent model of the induction motor in each scenario; and determining the equivalent proportion of induction motors in the target area based on the recorded proportion of induction motors in each scenario. This invention proposes an equivalent method and system for matching the effective value of short-circuit current provided by an induction motor. In the technical solution of this invention, the matching amount of short-circuit current provided by the equivalent model of the induction motor and the detailed model of the induction motor in the distribution network for electromechanical transient calculation of a large power grid is directly adopted using the effective value of the periodic component of the short-circuit current. This value is a direct characteristic quantity for short-circuit current calculation. The method has rigorous logic. In principle, the technical solution of this invention is applicable to both situations where the DC and AC component attenuation of the equivalent model of the induction motor in the electromechanical transient of a large regional power grid is consistent with that of the detailed model of the distribution network, and situations where the attenuation difference between the two is large, thus possessing strong robustness. Attached Figure Description

[0061] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0062] Figure 1 A flowchart illustrating an equivalent method for matching the effective value of short-circuit current in an induction motor according to a preferred embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of a detailed electromagnetic transient simulation model of a power distribution network according to a preferred embodiment of the present invention;

[0064] Figure 3 This is a schematic diagram of an equivalent distribution network electromagnetic transient simulation model according to a preferred embodiment of the present invention;

[0065] Figure 4 This is a schematic diagram of the simulation curve fitting of a certain scene according to a preferred embodiment of the present invention;

[0066] Figure 5 A flowchart illustrating an equivalent method for matching the effective value of short-circuit current in an induction motor according to a preferred embodiment of the present invention; and

[0067] Figure 6 An equivalent system structure diagram is provided for short-circuit current RMS value matching of an induction motor according to a preferred embodiment of the present invention. Detailed Implementation

[0068] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0069] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0070] Figure 1 A flowchart illustrating an equivalent method for matching the effective value of short-circuit current to an induction motor according to a preferred embodiment of the present invention.

[0071] This invention addresses the significant discrepancy between the attenuation characteristics of an equivalent induction motor model in electromechanical transient simulation and the actual detailed model of a power distribution network. This discrepancy leads to a decrease in the initial effective value I” of the short-circuit current periodic component when using the short-circuit current peak matching method. k To address situations where matching fails, short-circuit current calculations are inaccurate, or the full-waveform matching method is complex to apply in engineering, this study proposes a method for matching the effective value of the short-circuit current using a detailed model and an equivalent model of the induction motor. The proposed method directly uses the characteristic quantity I" of the short-circuit current for calculation. kThis method ensures the accuracy of short-circuit current calculations provided by induction motors without altering the induction motor model parameters in the electromechanical transient simulation model, facilitating practical applications. The proposed method can be directly applied to the verification of short-circuit current levels in the planning and operation of power grids at all levels. It provides technical support and decision-making basis for selecting electrical equipment capacity in power grid planning and design schemes, conducting preliminary feasibility studies and scheme comparisons for major engineering projects, scientifically carrying out power grid planning and design, and ensuring safe operation, thus promoting a balance between power grid safety and economy.

[0072] like Figure 1 As shown, the present invention provides an equivalent method for providing effective short-circuit current matching for an induction motor, the method comprising:

[0073] Step 101: Identify multiple scenarios involving different power grid loads in the target area;

[0074] This invention investigates the typical power supply structure of regional distribution networks, including transformer capacity, parameters, lines, average transformer load rate, and average power supply radius of lines.

[0075] Step 102: Establish detailed models and equivalent models of induction motors under multiple scenarios; and set fault points for the detailed models and equivalent models of induction motors.

[0076] Preferably, before establishing detailed models and equivalent models of induction motors under multiple scenarios, the method further includes:

[0077] Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

[0078] Preferably, detailed models and equivalent models of induction motors are established for multiple scenarios, including:

[0079] When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

[0080] Preferably, fault points are set in the detailed model and equivalent model of the induction motor, including:

[0081] The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

[0082] This invention analyzes the equivalent model of an induction motor, the load structure of a typical power plant, and the actual model of an induction motor used for electromechanical transient calculations of a large power grid in the research area.

[0083] This invention proposes n actual scenarios for the load composition of a regional distribution network.

[0084] This invention establishes detailed models of the n distribution network scenarios proposed in the above steps, and establishes an equivalent model of the distribution network in the study area.

[0085] This invention sets fault points, calculates the short-circuit current provided by the load side in n scenarios, and outputs n short-circuit current curves.

[0086] In this invention, the actual models of induction motors in the research area may include multiple types. For engineering purposes, only the most typical models need to be selected. Additionally, models with similar parameters can be appropriately merged. For example, a typical load model for a certain area obtained from the survey is shown in Table 1. Among them, the parameters of the refrigeration equipment motor and the industrial small motor are the same, and the parameters of the irrigation motor are close to those of the industrial small motor. Therefore, it is considered that the industrial small motor will be used to replace the irrigation motor in subsequent modeling.

[0087] Table 1. Parameters of main induction motors in a certain regional power distribution network

[0088]

[0089]

[0090] This invention establishes a basic framework for the distribution network based on the power supply structure and transformer and line parameters of the research area. Following the typical scenarios proposed in the preceding steps, detailed electromagnetic transient simulation models and equivalent models are established for each scenario. It is important to note that the large-scale power grid induction motor model is a single-cage model or a wound-rotor model, and the model used in the electromagnetic transient simulation must also adopt this type of model, ensuring that the load factor is consistent with the equivalent model of the large-scale power grid induction motor. Taking a 220 / 110 / 10kV distribution network structure as an example, a detailed distribution network structure for a certain scenario is established (as follows). Figure 2 (as shown) and equivalent power grid structure (as shown below) Figure 3 (As shown).

[0091] Step 103: Obtain the standard AC component of the fault-generated short-circuit current under each scenario through the detailed model of the induction motor; obtain the comparative AC component of the fault-generated short-circuit current under each scenario through the equivalent model of the induction motor.

[0092] Preferably, wherein:

[0093] The instantaneous value of the short-circuit current is expressed as:

[0094]

[0095] In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant.

[0096] make

[0097] The instantaneous value of the short-circuit current can be simplified as follows:

[0098]

[0099] In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3):

[0100]

[0101] In equation (3), I” k φ is the initial effective value of the periodic component of the short-circuit current; f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component.

[0102] The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 Given the AC component decay time constant τ1 and the DC component decay time constant τ2, determine the DC and AC components of the short-circuit current.

[0103] This invention extracts the AC and DC components of the short-circuit current curve.

[0104] The fault point selection, fault start time, and fault end time of the equivalent model and the detailed distribution network simulation model of this invention are consistent. The fault point can be set at the high-voltage side of the transformer (220kV bus) or the medium-voltage side of the transformer (110kV bus). First, the short-circuit current provided by the load side of the detailed model in n scenarios is solved respectively, which serves as the basis for equivalent matching of the equivalent model, and n short-circuit current curves are output.

[0105] In this step, the instantaneous value expression of the short-circuit current is given by equation (1):

[0106]

[0107] In the formula, This is the AC component of the short-circuit current. This represents the DC component of the short-circuit current.

[0108] make

[0109] The instantaneous value of the short-circuit current can be simplified to equation (2):

[0110]

[0111] In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3):

[0112]

[0113] There are a total of 6 variables in equation (3), I” k φ is the initial effective value of the periodic component of the short-circuit current; f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the attenuation time constant of the AC component, and τ3 is the attenuation time constant of the DC component.

[0114] I” can be solved by curve fitting. k f, φ, I D0 τ1, τ2, and the DC component can be extracted.

[0115] Figure 1 The fitting result of a simulation curve for a certain scene. The fitting order in this case is 5. The values ​​of each variable obtained are as follows:

[0116] I” k =2.09kA, f=45.71Hz, φ=2.54rad, I D0 =2.35kA, τ1=24.39ms, τ2=19.84ms. Therefore, the AC component expression is: The expression for the DC component is:

[0117] Step 104: Match the initial effective values ​​of the standard AC component and the comparison AC component in each scenario until the absolute value of the percentage difference between the comparison AC component and the standard AC component is less than the preset threshold, and record the proportion of the induction motor in the equivalent model of the induction motor in each scenario.

[0118] This invention matches the short-circuit current calculation results of the equivalent model with the detailed model according to the effective value of the AC component of the short-circuit current, and proposes the equivalent ratio for each scenario.

[0119] In this invention, an equivalent model is needed to match the initial effective values ​​of the AC components of the short-circuit current in the n scenarios extracted in the above steps. Specifically, by adjusting the proportion of the induction motor in the equivalent model, the short-circuit current simulation curve provided by the induction motor in the equivalent model is obtained. Following the method described in the above steps, the initial effective values ​​of the AC components in the short-circuit current simulation curve are extracted, and these values ​​are matched with the initial effective values ​​I" of the periodic components of the short-circuit current in each scenario of each detailed model. kComparison, until the equivalent model and the detailed model are |I” k | <1%, and the proportion of induction motors in an equivalent model is recorded for each scenario.

[0120] Step 105: Based on the recorded proportions of induction motors in each scene, determine the equivalent proportion of induction motors in the target area.

[0121] This invention can fit the equivalent proportions of various scenarios to obtain the equivalent proportions of induction motors in a region, thereby generating short-circuit current calculation data.

[0122] This invention proposes an equivalent method for matching the effective value of short-circuit current provided by an induction motor. In this method, the matching amount of short-circuit current provided by the equivalent model of the induction motor and the detailed model of the induction motor in the distribution network in the electromechanical transient calculation of a large power grid is directly adopted using the effective value of the periodic component of the short-circuit current. This value is a direct characteristic quantity for short-circuit current calculation. The method has rigorous logic. In principle, this method is applicable to both situations where the DC and AC component attenuation of the equivalent model of the induction motor in the electromechanical transient calculation of a large regional power grid is consistent with that of the detailed model of the distribution network, and situations where the attenuation difference between the two is large. It has strong robustness.

[0123] Compared with the short-circuit current full waveform matching method, this invention does not require adjusting the parameters of the equivalent model of the induction motor in the electromechanical transient simulation of a large power grid, which is beneficial for practical engineering applications.

[0124] Compared with the short-circuit current peak matching method, this invention is not limited by whether the attenuation of the DC and AC components of the equivalent model of the induction motor in the electromechanical transient simulation of the large power grid is consistent with that of the detailed model of the induction motor in the distribution network, and has better model adaptability.

[0125] This invention takes a provincial power grid as an example. In 2023, the province replaced its equivalent model for electromechanical transient induction motors. The model before the replacement is referred to as the "old model," and the model after the replacement is referred to as the "new model." In the old model, because the overall decay time constants of the DC and AC components differed slightly from the overall decay time constants of the detailed distribution network model, the peak-matching method was used, resulting in consistent short-circuit current peaks and initial effective values ​​of the short-circuit current differing between -20% and 8%, with alternating positive and negative values. The calculation results were therefore acceptable. However, in the new model, because the overall decay time constant is large compared to the detailed distribution network model, the peak-matching method was used, resulting in consistent short-circuit current peaks and initial effective values ​​of the short-circuit current differing between 12% and 44%, a significant difference, all of which are positive. This lack of acceptance would lead to overestimation of the short-circuit current calculations, reducing the economic efficiency of the power system. The results of the two models using the peak-matching method are shown in Table 2.

[0126] Using the effective value matching method proposed in this invention, near 100% effective value matching can be achieved. Table 3 shows the matching results of the new and old models according to the method proposed in this patent. The maximum absolute improvement in matching accuracy for the old model is 20%, and the maximum absolute improvement in matching accuracy for the new model is 44%.

[0127] Table 3. Specific details of matching new and old models based on effective values.

[0128]

[0129]

[0130] Figure 6 An equivalent system structure diagram is provided for short-circuit current RMS value matching of an induction motor according to a preferred embodiment of the present invention.

[0131] like Figure 6 As shown, the present invention provides an equivalent system for providing effective short-circuit current matching for an induction motor, the system comprising:

[0132] The initial unit 601 is used to determine multiple scenarios involving different power grid loads in the target area;

[0133] Preferably, before establishing detailed models and equivalent models of induction motors under multiple scenarios, the initial unit 601 is further used for:

[0134] Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

[0135] Unit 602 is used to establish detailed models and equivalent models of induction motors under multiple scenarios; and to set fault points for the detailed models and equivalent models of induction motors.

[0136] Preferably, the establishment unit 602 is used to establish detailed models and equivalent models of induction motors under multiple scenarios, and is also used for:

[0137] When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

[0138] Preferably, the establishment unit 602 is used to set fault points in the detailed model and equivalent model of the induction motor, and is also used for:

[0139] The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

[0140] The acquisition unit 603 is used to acquire the standard AC component of the fault-generated short-circuit current under various scenarios through a detailed model of the induction motor; and to acquire the comparative AC component of the fault-generated short-circuit current under various scenarios through an equivalent model of the induction motor.

[0141] Execution unit 604 is used to match the initial valid values ​​of the standard AC component and the comparison AC component under each scenario until the absolute value of the percentage difference between the comparison AC component and the standard AC component is less than a preset threshold, and then record the proportion of the induction motor in the equivalent model of the induction motor under each scenario.

[0142] Preferably, wherein:

[0143] The instantaneous value of the short-circuit current is expressed as:

[0144]

[0145] In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant.

[0146] make

[0147] The instantaneous value of the short-circuit current can be simplified as follows:

[0148]

[0149] In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3):

[0150]

[0151] In equation (3), f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component.

[0152] The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 Given the AC component decay time constant τ1 and the DC component decay time constant τ2, determine the DC and AC components of the short-circuit current.

[0153] Result unit 605 is used to determine the equivalent proportion of induction motors in the target area based on the recorded proportions of induction motors in each scene.

[0154] The equivalent system for providing effective short-circuit current matching of an induction motor according to a preferred embodiment of the present invention corresponds to the equivalent method for providing effective short-circuit current matching of an induction motor according to another preferred embodiment of the present invention, and will not be described again here.

[0155] The present invention provides a computer-readable storage medium storing a computer program for executing an equivalent method for providing effective short-circuit current matching for an induction motor.

[0156] This invention provides an electronic device, characterized in that the electronic device includes: a processor and a memory; wherein,

[0157] Memory, used to store processor-executable instructions;

[0158] A processor for reading executable instructions from memory and executing the instructions to implement an equivalent method for providing effective short-circuit current matching for an induction motor.

[0159] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0160] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0161] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0162] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0163] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0164] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0165] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0166] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. An equivalent method for providing short-circuit current RMS matching for an induction motor, the method comprising: Identify multiple scenarios involving different power grid loads in the target area; Detailed models and equivalent models of induction motors were established for multiple scenarios. Fault points are set for the detailed model and equivalent model of the induction motor. The standard AC component of the short-circuit current generated by the fault in each scenario is obtained through the detailed model of the induction motor; the comparative AC component of the short-circuit current generated by the fault in each scenario is obtained through the equivalent model of the induction motor; the instantaneous value expression of the short-circuit current is: In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant. make The instantaneous value of the short-circuit current can be simplified as follows: In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3): In equation (3), f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component. The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 The attenuation time constant τ1 of the AC component and the attenuation time constant τ2 of the DC component are used to determine the DC and AC components of the short-circuit current. The initial effective values ​​of the standard AC component and the initial effective values ​​of the comparison AC component are matched in each scenario until the absolute value of the percentage difference between the initial effective value of the comparison AC component and the initial effective value of the standard AC component is less than a preset threshold. Then, the proportion of the induction motor in the equivalent model of the induction motor in each scenario is recorded. Based on the recorded proportions of induction motors in each scene, the equivalent proportion of induction motors in the target area is determined.

2. The method according to claim 1, further comprising, before establishing the detailed model and equivalent model of the induction motor under multiple scenarios: Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

3. The method according to claim 1, wherein establishing detailed models and equivalent models of induction motors under multiple scenarios includes: When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

4. The method according to claim 1, wherein setting fault points in the detailed model and equivalent model of the induction motor includes: The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

5. An equivalent system for providing short-circuit current RMS matching for an induction motor, the system comprising: The initial unit is used to determine multiple scenarios based on different power grid loads in the target area; A model building unit is used to build detailed models and equivalent models of induction motors under multiple scenarios; and to set fault points for the detailed models and equivalent models of induction motors. The acquisition unit is used to acquire the standard AC component of the fault-generated short-circuit current under various scenarios through the detailed model of the induction motor; and to acquire the comparative AC component of the fault-generated short-circuit current under various scenarios through the equivalent model of the induction motor; the instantaneous value expression of the short-circuit current is: In the formula, This is the AC component of the short-circuit current. I″ represents the DC component of the short-circuit current; ω represents the angular velocity. k Here, t represents the initial effective value of the AC component of the short-circuit current, and t is the time after the fault. τ1 is the initial phase angle of the short-circuit current and voltage, γ0 is the impedance angle, τ1 is the AC component decay time constant, and τ2 is the DC component decay time constant. make The instantaneous value of the short-circuit current can be simplified as follows: In equation (2), ω is the angular velocity. Substituting ω = 2πf into equation (2) yields equation (3): In equation (3), f is the frequency of the AC component of the short-circuit current; φ is the initial phase angle of the AC component; I D0 τ1 is the initial value of the DC component, τ2 is the decay time constant of the AC component, and τ3 is the decay time constant of the DC component. The initial effective value I” of the AC component of the short-circuit current is obtained by curve fitting. k The frequency f of the AC component of the short-circuit current, the initial phase angle φ of the AC component, and the initial value I of the DC component. D0 The attenuation time constant τ1 of the AC component and the attenuation time constant τ2 of the DC component are used to determine the DC and AC components of the short-circuit current. The execution unit is used to match the initial effective value of the standard AC component with the initial effective value of the comparison AC component in each scenario until the absolute value of the percentage difference between the initial effective value of the comparison AC component and the initial effective value of the standard AC component is less than a preset threshold, and then record the proportion of the induction motor in the equivalent model of the induction motor in each scenario. The result unit is used to determine the equivalent proportion of induction motors in the target area based on the recorded proportions of induction motors in each scene.

6. The system according to claim 5, wherein before establishing the detailed model and equivalent model of the induction motor under multiple scenarios, the initial unit is further configured to: Based on the parameter values ​​of the load model, the type of detailed model of the induction motor is determined.

7. The system according to claim 5, wherein the establishing unit is configured to establish detailed models and equivalent models of induction motors under multiple scenarios, and is further configured to: When the detailed model of the distribution network scenario is a single-cage model or a wound-rotor model, the equivalent induction motor model is determined to be a single-cage model or a wound-rotor model.

8. The system according to claim 5, wherein the establishing unit is configured to set fault points for the detailed model and equivalent model of the induction motor, and is further configured to: The fault point selection, fault start time, and fault end time are consistent in the detailed model and the equivalent model of the induction motor.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that is executed by a processor to implement the method of any one of claims 1-4.

10. An electronic device, characterized in that, The electronic device includes: a processor and a memory; wherein, The memory is used to store the processor-executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method of any one of claims 1-4.

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