Equivalent method and system for providing short-circuit current effective value matching by induction motor

Abstract

The invention discloses an equivalent method and system for providing short-circuit current effective value matching by an induction motor. The method comprises the following steps: determining a plurality of scenes formed by different power grid loads in a target area; establishing an induction motor detailed model and an induction motor equivalent model in a plurality of scenes; fault points are set for the induction motor detailed model and the induction motor equivalent model; obtaining a standard AC component of a short-circuit current generated by a fault in each scene through the detailed model of the induction motor; obtaining a comparison alternating current component of a short-circuit current generated by a fault in each scene through an equivalent model of the induction motor; matching the standard alternating current component and the comparison alternating current component in each scene until the absolute value of the difference percentage of the comparison alternating current component and the standard alternating current component is smaller than a preset threshold value, and recording the proportion of the induction motor in the induction motor equivalent model in each scene; and determining the equivalent proportion of the induction motor in the target area based on the recorded proportion of the induction motor in each scene.

Description

Technical Field

[0001] The present invention relates to the technical field of power system planning and operation, and more specifically, to an equivalent method and system for providing short-circuit current effective value matching for an induction motor. Background Art

[0002] In the planning, design and operation control of the power system, short-circuit current calculation is required for the selection of system equipment capacity parameters, setting of protection device settings and arrangement of operation modes. The results of short-circuit current calculation have a significant impact on the coordination of system safety and economy. If the calculated result is too large, it is necessary to select a larger capacity switchgear, which will increase investment; it may also cause the short-circuit level evaluation results of many sites to exceed the standard, and additional current limiting measures will be added. While increasing investment, the reliability of system operation may be reduced. If the calculated result is too small, although it will save equipment investment, the circuit breaker equipment may face insufficient interruption capacity, affecting the safety of the equipment and system.

[0003] With the development of the power grid, the short-circuit current of the power grid in each load center area is high and shows a global development trend. For a long time, there has been an inconsistency in the calculation boundary of short-circuit current between different decision-making departments, and the calculation results of different calculation boundary conditions are quite different, which makes decision-making difficult. Among them, how to consider the induction motor of the distribution network in the load is one of the main boundary conditions. The induction motor will feedback the short-circuit current when the system is short-circuited. The load proportion of induction motors in the distribution network in different regions is quite different. In addition, the induction motors are of different types and have different access voltage levels, and their contribution characteristics to the short-circuit current are significantly different. However, the number of nodes and branches in the distribution network is huge, and it is almost impossible to model the distribution network at all voltage levels. When the planning and operation departments of my country's power system perform calculations and analysis on the main power grid, they usually equate the load to the 110 kV bus. The calculation of the short-circuit current of the power grid is based on electromechanical transient simulation data and models, and directly considers the contribution of the induction motor according to the sum ratio of the induction motor, and the calculation result is too large.

[0004] In view of this situation, prior art 1, "An equivalent modeling method for short-circuit current contribution of induction motors in distribution networks", proposes a method for more accurately calculating the short-circuit current level of a region (provincial level) by changing the proportion of induction motors in the total load without changing the basic algorithm of short-circuit current and the basic data structure of electromechanical transients. Prior art 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] Prior art 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 plant.

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

[0007] In the prior art 1 and 2, the consistency matching method for the short-circuit current provided by the distribution network equivalent model and the detailed model induction motor is as follows: p Matching or full waveform matching method. The peak matching method does not require adjustment of the induction motor model parameters of the electromechanical transient simulation, and is easy to use. However, it is only suitable for matching when the attenuation of the detailed model of the induction motor in the distribution network and the equivalent model are basically the same. If the attenuation of the equivalent induction motor model of the two is significantly different from the detailed model, that is, κ is no longer close to 1.8 or 1.9, the peak matching method will result in I” in the matching result. k The huge difference leads to inaccurate short-circuit current calculation results. The full waveform matching method has accurate simulation results, but it needs to change the parameters of the equivalent induction motor in the electromechanical transient simulation model, and each station may use different parameters, which brings a huge workload to the simulation analysts and is not conducive to practical engineering applications.

[0008] Therefore, it is still necessary to continue to study the engineering practical methods for accurately simulating the short-circuit current provided by induction motors in distribution networks. Summary of the invention

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

[0010] In order to solve the above problem, the present invention provides an equivalent method for providing short-circuit current effective value matching for an induction motor, the method comprising:

[0011] Determine multiple scenarios of different grid load compositions in the target area;

[0012] Establishing a detailed model of an induction motor and an equivalent model of an induction motor under multiple scenarios; and setting a fault point for the detailed model of the induction motor and the equivalent model of the induction motor;

[0013] The standard AC component of the short-circuit current generated by the fault in each scenario is obtained by using the induction motor detailed model; the comparative AC component of the short-circuit current generated by the fault in each scenario is obtained by using the induction motor equivalent model;

[0014] Matching the standard AC component with the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold, and recording the proportion of the induction motor in the induction motor equivalent model in each scenario;

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

[0016] Preferably, before establishing the detailed model of the induction motor and the equivalent model of the induction motor in multiple scenarios, the method further includes:

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

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

[0019] When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

[0020] Preferably, the setting of the fault point for the induction motor detailed model and the induction motor equivalent model comprises:

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

[0022] Preferably, wherein:

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

[0024]

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

[0026] make

[0027] The instantaneous value of short-circuit current is simplified as:

[0028]

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

[0030]

[0031] In formula (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 D0is the initial value of the DC component, τ1 is the decay time constant of the AC component, and τ2 is the decay time constant of the DC component;

[0032] By curve fitting, the initial effective value I" of the AC component of the short-circuit current is solved 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

[0033] According to another aspect of the present invention, the present invention provides an equivalent system for providing short-circuit current effective value matching for an induction motor, the system comprising:

[0034] An initial unit, used to determine multiple scenarios of different grid load compositions in the target area;

[0035] An establishing unit is used to establish a detailed model of the induction motor and an equivalent model of the induction motor under multiple scenarios; and to set a fault point for the detailed model of the induction motor and the equivalent model of the induction motor;

[0036] An acquisition unit, configured to acquire a standard AC component of a short-circuit current generated by a fault in each scenario through the induction motor detailed model; and acquire a comparative AC component of a short-circuit current generated by a fault in each scenario through the induction motor equivalent model;

[0037] an execution unit, configured to match the standard AC component with the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold, and record the proportion of the induction motor in the induction motor equivalent model in each scenario;

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

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

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

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

[0042] When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

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

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

[0045] Preferably, wherein:

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

[0047]

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

[0049]

[0050] The instantaneous value of short-circuit current is simplified as:

[0051]

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

[0053]

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

[0055] By curve fitting, the initial effective value I" of the AC component of the short-circuit current is solved 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

[0056] Based on 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, and the computer program is used to execute an equivalent method for providing short-circuit current effective value matching for an induction motor.

[0057] Based on 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 a memory for storing instructions executable by the processor;

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

[0060] The technical solution of the present invention provides an equivalent method and system for providing short-circuit current effective value matching for an induction motor, wherein the method comprises: determining multiple scenarios consisting of different power grid loads in a target area; establishing detailed models of induction motors and equivalent models of induction motors in multiple scenarios; and setting fault points for the detailed models of induction motors and the 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 standard AC component with the comparative AC component in each scenario until the absolute value of the difference percentage between the comparative AC component and the standard AC component is less than a preset threshold value, 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. The present invention proposes an equivalent method and system for providing short-circuit current effective value matching for an induction motor. In the technical solution of the present invention, the matching amount of short-circuit current provided by the induction motor equivalent model in the electromechanical transient calculation of a large power grid and the detailed model of the induction motor in the distribution network directly adopts the effective value of the short-circuit current periodic component, which is a direct characteristic quantity for short-circuit current calculation. The method has rigorous logic. From a principle point of view, the technical solution of the present invention is applicable to the situation where the attenuation of the DC component and AC component of the induction motor equivalent model in the electromechanical transient of a large power grid is consistent with the detailed model of the distribution network, and is also applicable to the situation where the attenuation difference between the two is large, and has strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

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

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

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

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

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

[0067] Figure 6 An equivalent system structure diagram for providing short-circuit current effective value matching for an induction motor according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0068] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0069] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

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

[0071] The present invention aims at the fact that the attenuation of the equivalent induction motor model in the electromechanical transient simulation is greatly different from the actual detailed model of the distribution network, resulting in the initial effective value I" of the short-circuit current periodic component when the short-circuit current peak matching method is adopted. k In the case of matching failure, inaccurate short-circuit current calculation results, or the complexity of engineering practical application of the full waveform matching method, the study proposes a method for matching the effective value of short-circuit current provided by the detailed model and equivalent model of the induction motor. The proposed method directly uses the short-circuit current to calculate the characteristic quantity I” k, which can ensure the accuracy of the short-circuit current calculation results provided by the induction motor, while not changing the model parameters of the induction motor in the electromechanical transient simulation model, which is convenient for practical application. The proposed method can be directly applied to the short-circuit current level verification of power grids in the planning and operation of power grids at all levels, and provide technical support and decision-making basis for the selection of electrical equipment capacity for power grid planning and design schemes, preliminary demonstration and scheme comparison of major engineering projects, scientifically carrying out power grid planning and design, and ensuring safe operation, and promoting the coordination of power grid safety and economy.

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

[0073] Step 101: Determine multiple scenarios consisting of different power grid loads in a target area;

[0074] The present invention investigates and studies the typical power supply structure of the regional distribution network, including transformer capacity, parameters, lines, average load rate of transformers, average power supply radius of lines, etc.

[0075] Step 102: establishing a detailed model of the induction motor and an equivalent model of the induction motor under multiple scenarios; and setting a fault point for the detailed model of the induction motor and the equivalent model of the induction motor;

[0076] Preferably, before establishing the detailed model of the induction motor and the equivalent model of the induction motor in multiple scenarios, the method further includes:

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

[0078] Preferably, a detailed model of the induction motor and an equivalent model of the induction motor are established under multiple scenarios, including:

[0079] When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

[0080] Preferably, setting a fault point for the induction motor detailed model and the induction motor equivalent model includes:

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

[0082] The present invention analyzes an induction motor equivalent model used for electromechanical transient calculation of a large power grid in a studied area, a load structure of a typical plant and a practical model of an induction motor.

[0083] The present invention proposes n actual scenarios of regional distribution network load composition.

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

[0085] The present invention solves the short-circuit currents provided by the load side of n scenarios respectively and outputs n short-circuit current curves by setting the fault point.

[0086] In the present invention, the actual model of induction motor in the research area may include multiple models. In engineering, the most typical models can be selected. In addition, it is appropriate to consider merging models with similar parameters. The typical load model of 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 and the industrial small motor are close. Consider using the industrial small motor to replace the irrigation motor in subsequent modeling.

[0087] Table 1 Main parameters of induction motors in a regional distribution network

[0088]

[0089]

[0090] The present invention builds the basic framework of the distribution network according to the power supply structure of the distribution network in the study area and the parameters of transformers and lines at all levels, and establishes the detailed electromagnetic transient simulation model and equivalent model in each scenario according to the typical scenarios proposed in the above steps. It should be noted that the large power grid induction motor model is a single cage model or a winding model, and the model in the electromagnetic transient simulation also needs to adopt this type of model, and ensure that the load rate is consistent with the equivalent model of the large power grid induction motor. Taking the 220 / 110 / 10kV distribution network structure as an example, a detailed distribution network structure is established under a certain scenario (as shown below Figure 2 as shown) and the equivalent grid structure (as shown below Figure 3 shown).

[0091] Step 103: 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;

[0092] Preferably, wherein:

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

[0094]

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

[0096] make

[0097] The instantaneous value of short-circuit current is simplified as:

[0098]

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

[0100]

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

[0102] By curve fitting, the initial effective value I" of the AC component of the short-circuit current is solved 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

[0103] The present invention extracts the AC component and the DC component of the short-circuit current curve.

[0104] The fault point selection, fault start time and end time of the equivalent model of the present invention are consistent with those of the detailed distribution network simulation model. The fault point setting location can be the high-voltage side of the transformer (220kV bus) or the medium-voltage side of the transformer (110kV bus). The short-circuit current provided by the load side of the detailed model in n scenarios is first solved separately 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 of the short-circuit current is expressed as formula (1):

[0106]

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

[0108] make

[0109] The instantaneous value of short-circuit current can be simplified as formula (2):

[0110]

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

[0112]

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

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

[0115] Figure 1 The fitting of a simulation curve of a certain scene. The fitting order is 5, and the values ​​of the variables are:

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

[0117] Step 104: Matching the standard AC component and the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold, and recording the proportion of the induction motor in the induction motor equivalent model in each scenario;

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

[0119] In the present invention, an equivalent model is required to match the AC components of the short-circuit current of the n scenarios extracted in the above steps, that is, by adjusting the proportion of induction motors in the equivalent model, the short-circuit current simulation curve provided by the induction motors in the equivalent model is obtained, and according to the method in the above steps, the initial effective value of the AC component in the short-circuit current simulation curve is extracted to make it respectively match the AC component I" in each scenario in each detailed model. kCompare until the equivalent model and the detailed model are |I” k |<1%, the proportion of induction motors in an equivalent model is recorded for each scenario.

[0120] Step 105: Determine the equivalent ratio of the induction motor in the target area based on the recorded ratios of the induction motors in each scene.

[0121] The present invention can fit the equivalent ratios of various scenes, obtain the equivalent ratios of induction motors in the region, and form short-circuit current calculation data.

[0122] The present 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 in the electromechanical transient calculation of the large power grid and the detailed model of the induction motor in the distribution network directly adopts the effective value of the periodic component of the short-circuit current. This value is a direct characteristic quantity for the short-circuit current calculation. The method has rigorous logic. In principle, the method is applicable to the situation where the attenuation of the DC component and AC component of the equivalent model of the induction motor in the electromechanical transient of the large power grid is consistent with the detailed model of the distribution network, and is also applicable to the situation where the attenuation difference between the two is large, and has strong robustness.

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

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

[0125] The present invention takes the actual power grid of a certain province as an example. The province replaced the equivalent model of electromechanical transient induction motor in 2023. The model before replacement is referred to as "old model", and the model after replacement is referred to as "new model". The old model has a slightly smaller difference in the overall decay time constant of the DC component and the AC component than the overall decay time constant of the detailed model of the distribution network. The peak matching method is adopted, the short-circuit current peak is consistent, the initial effective value difference of the short-circuit current is between -20% and 8%, and the positive and negative are alternating, and the calculation results can be trusted. However, the new model has a large overall decay time constant and the overall decay time constant of the detailed model of the distribution network. The peak matching method is adopted, the short-circuit current peak is consistent, and the initial effective value difference of the short-circuit current is between 12% and 44%, which is a huge difference, and they are all positive differences. It does not have a basis for trust. If you insist on trusting, it will lead to a large calculation result of the short-circuit current, which will reduce the economy of the power system. The results of the peak matching method for the two models are shown in Table 2.

[0126] By using the effective value matching method proposed in the present invention, an effective value matching close to 100% can be achieved. Table 3 shows the matching results of the new and old models according to the method proposed in this patent. The absolute value of the matching accuracy of the old model is improved by 20% at most, and the absolute value of the matching accuracy of the new model is improved by 44% at most.

[0127] Table 3 Specific situations of matching the new and old models by effective value

[0128]

[0129]

[0130] Figure 6 An equivalent system structure diagram for providing short-circuit current effective value matching for 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 short-circuit current effective value matching for an induction motor, the system comprising:

[0132] Initial unit 601, used to determine multiple scenarios composed of different power grid loads in the target area;

[0133] Preferably, before establishing the detailed model of the induction motor and the equivalent model of the induction motor in multiple scenarios, the initialization unit 601 is further used to:

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

[0135] Establishing unit 602, used to establish detailed models of induction motors and equivalent models of induction motors in multiple scenarios; and set fault points for the detailed models of induction motors and equivalent models of induction motors;

[0136] Preferably, the establishing unit 602 is used to establish a detailed model of the induction motor and an equivalent model of the induction motor in multiple scenarios, and is also used to:

[0137] When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

[0138] Preferably, the establishing unit 602 is used to set the fault point for the induction motor detailed model and the induction motor equivalent model, and is also used to:

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

[0140] An acquisition unit 603 is used to acquire a standard AC component of a short-circuit current generated by a fault in each scenario through a detailed model of the induction motor; and to acquire a comparative AC component of a short-circuit current generated by a fault in each scenario through an equivalent model of the induction motor;

[0141] The execution unit 604 is used to match the standard AC component with the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold value, and record the proportion of the induction motor in the induction motor equivalent model in each scenario.

[0142] Preferably, wherein:

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

[0144]

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

[0146] make

[0147] The instantaneous value of short-circuit current is simplified as:

[0148]

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

[0150]

[0151] In formula (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 is the initial value of the DC component, τ1 is the decay time constant of the AC component, and τ2 is the decay time constant of the DC component;

[0152] By curve fitting, the initial effective value I" of the AC component of the short-circuit current is solved 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

[0153] The result unit 605 is used to determine the equivalent ratio of the induction motor in the target area based on the recorded ratio of the induction motor in each scene.

[0154] An equivalent system for providing short-circuit current effective value matching for an induction motor in a preferred embodiment of the present invention corresponds to an equivalent method for providing short-circuit current effective value matching for an induction motor in another preferred embodiment of the present invention, which will not be described in detail here.

[0155] The present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program is used to execute an equivalent method for providing short-circuit current effective value matching for an induction motor.

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

[0157] Memory, a memory for storing processor executable instructions;

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

[0159] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may 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 codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0160] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0161] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate 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 A function specified in one or more boxes.

[0162] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions 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.

[0163] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0164] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0165] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0166] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / said / the [means, components, etc.]" are to be openly interpreted as at least one instance of the means, components, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. An equivalent method for providing short-circuit current effective value matching for an induction motor, the method comprising: Determine multiple scenarios of different grid load compositions in the target area; Establish detailed models of induction motors and equivalent models of induction motors under multiple scenarios; and setting fault points for the induction motor detailed model and the induction motor equivalent model; The standard AC component of the short-circuit current generated by the fault in each scenario is obtained by using the induction motor detailed model; the comparative AC component of the short-circuit current generated by the fault in each scenario is obtained by using the induction motor equivalent model; Matching the standard AC component with the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold, and recording the proportion of the induction motor in the induction motor equivalent model in each scenario; Based on the recorded ratios of the induction motors in each scene, the equivalent ratio of the induction motors in the target area is determined.

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

3. The method according to claim 1, wherein establishing detailed models of induction motors and equivalent models of induction motors under multiple scenarios comprises: When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

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

5. The method according to claim 1, wherein: The instantaneous value expression of the short-circuit current is: In the formula, is the AC component of the short-circuit current, is the DC component of the short-circuit current; ω is the angular velocity, I″ k is the initial effective value of the AC component of the short-circuit current, t is the time after the fault, is the initial phase angle of short-circuit current voltage, γ0 is the impedance angle, τ1 is the decay time constant of AC component, and τ2 is the decay time constant of DC component; make The instantaneous value of short-circuit current is simplified as: In formula (2), ω is the angular velocity. Substituting ω = 2πf into formula (2), we get formula (3): In formula (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 is the initial value of the DC component, τ1 is the decay time constant of the AC component, and τ2 is the decay time constant of the DC component; By curve fitting, the initial effective value I″ of the AC component of the short-circuit current is calculated 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

6. An equivalent system for providing short-circuit current effective value matching for an induction motor, the system comprising: An initial unit, used to determine multiple scenarios of different grid load compositions in the target area; An establishing unit is used to establish a detailed model of the induction motor and an equivalent model of the induction motor under multiple scenarios; and to set a fault point for the detailed model of the induction motor and the equivalent model of the induction motor; An acquisition unit, configured to acquire a standard AC component of a short-circuit current generated by a fault in each scenario through the induction motor detailed model; and acquire a comparative AC component of a short-circuit current generated by a fault in each scenario through the induction motor equivalent model; an execution unit, configured to match the standard AC component with the comparison AC component in each scenario until the absolute value of the difference percentage between the comparison AC component and the standard AC component is less than a preset threshold, and record the proportion of the induction motor in the induction motor equivalent model in each scenario; The result unit is used to determine the equivalent ratio of the induction motor in the target area based on the recorded ratio of the induction motor in each scene.

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

8. The system according to claim 6, wherein the establishing unit is used to establish detailed models of induction motors and equivalent models of induction motors in multiple scenarios, and is also used to: When the detailed model of the distribution network scenario is a single cage model or a winding model, it is determined that the equivalent induction motor model is a single cage model or a winding model.

9. The system according to claim 6, wherein the establishing unit is used to set a fault point for the induction motor detailed model and the induction motor equivalent model, and is also used to: The fault point selection, fault start time and fault end time in the induction motor detailed model and the induction motor equivalent model are consistent.

10. The method according to claim 6, wherein: The instantaneous value expression of the short-circuit current is: In the formula, is the AC component of the short-circuit current, is the DC component of the short-circuit current; ω is the angular velocity, I″ k is the initial effective value of the AC component of the short-circuit current, t is the time after the fault, is the initial phase angle of short-circuit current voltage, γ0 is the impedance angle, τ1 is the decay time constant of AC component, and τ2 is the decay time constant of DC component; make The instantaneous value of short-circuit current is simplified as: In formula (2), ω is the angular velocity. Substituting ω = 2πf into formula (2), we get formula (3): In formula (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 is the initial value of the DC component, τ1 is the decay time constant of the AC component, and τ2 is the decay time constant of the DC component; By curve fitting, the initial effective value I″ of the AC component of the short-circuit current is calculated 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 AC component decay time constant τ1, the DC component decay time constant τ2, determine the DC component and AC component of the short-circuit current.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 5.

12. An electronic device, characterized in that: The electronic device comprises: a processor and a memory; wherein, The memory is a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 5.

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