Correction method for online calculation of zero crossing point time of short-circuit current based on least square method

Abstract

The invention discloses a correction method for online calculation of short-circuit current zero-crossing time based on a least square method, and the method comprises the steps: changing a DC attenuation component according to a preset proportion requirement of a low-frequency power system, and carrying out the simulation calculation of a short-circuit fault, and obtaining a first relation between a zero-crossing time prediction error and a DC attenuation component proportion; changing the fault initial phase according to a preset phase adjustment requirement of the low-frequency power system, and carrying out short-circuit fault simulation calculation to obtain a second relation between the short-circuit zero crossing point time prediction error and the fault initial phase; obtaining an error compensation formula for predicting the current zero crossing point time according to the first relation and the second relation; calculating the predicted short-circuit current zero-crossing time and the short-circuit fault current parameter of the short-circuit fault by adopting a least square method, recording the calculation time, and calculating the compensation current zero-crossing time; and compensating the predicted short-circuit current zero-crossing time according to the compensation current zero-crossing time to obtain corrected short-circuit current zero-crossing time.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit breaker breaking, and more specifically, to a correction method for online calculating short-circuit current zero-crossing time based on a least squares method. Background Art

[0002] With the development of smart grids, short-circuit fault phase-controlled breaking technology has become an increasingly hot topic. Short-circuit fault phase-controlled breaking requires accurate prediction of the zero-crossing point of the fault current, which requires accurate calculation of the fault current parameters. The current short-circuit fault phase-controlled breaking algorithm has poor calculation accuracy and stability and is difficult to meet the needs of actual operation. At the same time, for low-frequency transmission systems, the frequency is relatively low, and the current short-circuit current parameter identification algorithm has large errors and requires a long calculation time, which urgently needs to be improved and enhanced. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a correction method for online calculating the zero-crossing time of a short-circuit current based on the least squares method.

[0004] According to one aspect of the present invention, a correction method for online calculating the short-circuit current zero-crossing time based on the least squares method is provided, comprising: According to the preset ratio requirement of the low-frequency power system, the DC attenuation component is changed to perform short-circuit fault simulation calculations respectively, and a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio is obtained; According to the preset phase adjustment requirements of the low-frequency power system, the initial fault phase is changed to perform short-circuit fault simulation calculations respectively, and a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase is obtained; Obtain an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; The predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault are calculated using the least square method, and the calculation time is recorded; Calculate the compensation current zero-crossing time according to the short-circuit fault current parameters, calculation time and error compensation formula; The predicted short-circuit current zero-crossing time is compensated according to the compensation current zero-crossing time to obtain the corrected short-circuit current zero-crossing time.

[0005] Optionally, the DC attenuation component is changed according to a preset ratio requirement in the low-frequency power system to perform short-circuit fault simulation calculations respectively, and a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio is obtained, including: Determine the variation range of the DC attenuation component of the low-frequency power system; Setting multiple DC attenuation component ratios within a variation range and determining preset ratio requirements; According to the preset ratio requirement, the DC attenuation component is changed to perform simulation calculations respectively, and the first short-circuit current zero-crossing time is calculated by using the least square method at multiple preset first calculation time points; Determine multiple groups of first short-circuit current zero-crossing time prediction errors according to multiple groups of calculated first short-circuit current zero-crossing time and multiple first calculation time points; A plurality of groups of first short-circuit zero-crossing time prediction errors and a plurality of corresponding groups of direct current attenuation component ratios are fitted to obtain a first relationship between the zero-crossing time prediction errors and the direct current attenuation component ratios.

[0006] Optionally, the fault initial phase is changed according to the preset phase adjustment requirement in the low-frequency power system to perform short-circuit fault simulation calculations respectively, and a second relationship between the short-circuit zero-crossing time prediction error and the fault initial phase is obtained, including: Determine the fault initial phase change interval of the low-frequency power system; Setting multiple fault initial phases within the variation interval and determining preset phase adjustment requirements; According to the preset phase adjustment requirement, the initial phase of the fault is changed to perform simulation calculation, and the second short-circuit current zero-crossing time is calculated by using the least square method at multiple preset second calculation time points; Determine multiple groups of second short-circuit current zero-crossing time prediction errors according to the calculated multiple groups of second short-circuit current zero-crossing time and multiple second calculation time points; A plurality of groups of second short-circuit zero-crossing time prediction errors and a plurality of corresponding groups of fault initial phases are fitted to obtain a second relationship between the short-circuit zero-crossing time prediction errors and the fault initial phases.

[0007] Optionally, the error compensation formula is: In the formula, t c To calculate the time, is the fault initial phase, I dc / I m is the DC attenuation component ratio, k 1. k 2. k 3. k 4 and k 5 is the fitting parameter in the second relationship, k 6 and k 7 is the fitting parameter in the first relationship.

[0008] Optionally, the compensation current zero-crossing time is calculated according to the short-circuit fault current parameter, the calculation time and the error compensation formula, including: Calculate the fault initial phase value and the fault DC attenuation component ratio according to the short-circuit fault current parameters; The error compensation formula is used to calculate the compensation current zero-crossing time according to the initial fault phase value, the fault DC attenuation component ratio and the calculation time.

[0009] Optionally, the fault initial phase value And the proportion of the fault DC attenuation component I dc / I m The calculation formula is: in, X 1. X 2. X 3 and X 4 is the short-circuit fault current parameter.

[0010] According to another aspect of the present invention, there is provided a correction device for online calculating the short-circuit current zero-crossing time based on the least squares method, comprising: A first simulation calculation module is used to change the DC attenuation component according to the preset ratio requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio; The second simulation calculation module is used to change the initial fault phase according to the preset phase adjustment requirements of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase; An obtaining module is used to obtain an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; A first calculation module is used to calculate the predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault by using the least square method, and record the calculation time; A second calculation module is used to calculate the compensation current zero-crossing time according to the short-circuit fault current parameter, the calculation time and the error compensation formula; The compensation module is used to compensate the predicted short-circuit current zero-crossing time according to the compensation current zero-crossing time to obtain the corrected short-circuit current zero-crossing time.

[0011] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and the computer program is used to execute the method described in any one of the above aspects of the present invention.

[0012] According to another aspect of the present invention, an electronic device is provided, comprising: a processor; 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 described in any one of the above aspects of the present invention.

[0013] Therefore, the present invention uses simulation to obtain the corresponding relationship between the DC attenuation component amplitude ratio and the fault voltage phase angle of the zero-crossing prediction error, and fits it into a mathematical equation, thereby obtaining a compensation formula for the zero-crossing prediction error, compensating for the short-circuit fault current zero-crossing prediction error, and improving the short-circuit fault current zero-crossing prediction accuracy and the convergence speed of the algorithm. This solves the problem that the prior art has low prediction accuracy for the short-circuit fault current zero-crossing, long calculation time, and cannot meet the requirements of phase selection and breaking. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings: Figure 1 It is a flow chart of a correction method for online calculation of short-circuit current zero-crossing time based on the least squares method provided by an exemplary embodiment of the present invention; Figure 2 is a schematic diagram of a low-frequency single-phase short-circuit fault model provided by an exemplary embodiment of the present invention; Figure 3 is a schematic diagram comparing the predicted zero-crossing point error with the initial phase of the fault provided by an exemplary embodiment of the present invention; Figure 4 is a schematic diagram comparing the predicted zero-crossing error with the attenuated DC component provided by an exemplary embodiment of the present invention; Figure 5 It is a schematic diagram of the change of the zero-crossing error predicted by the algorithm of the present invention with the initial phase of the fault provided by an exemplary embodiment of the present invention; Figure 6 is a schematic diagram showing changes in the predicted zero-crossing error with calculation time after an improved algorithm provided by an exemplary embodiment of the present invention; Figure 7 is a schematic diagram of algorithm error boundaries at different frequencies after the algorithm of the present invention is improved, provided by an exemplary embodiment of the present invention; Figure 8 It is a structural schematic diagram of a correction device for online calculation of short-circuit current zero-crossing time based on the least squares method provided by an exemplary embodiment of the present invention; Fig. 9 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0015] Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described here.

[0016] It should be noted that the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.

[0017] Those skilled in the art can understand that the terms "first" and "second" in the embodiments of the present invention are only used to distinguish different steps, devices or modules, etc., and neither represent any specific technical meaning nor indicate the necessary logical order between them.

[0018] It should also be understood that, in the embodiments of the present invention, “plurality” may refer to two or more than two, and “at least one” may refer to one, two or more than two.

[0019] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more, unless explicitly limited or otherwise indicated in the context.

[0020] In addition, the term "and / or" in the present invention is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0021] It should also be understood that the description of the various embodiments of the present invention focuses on the differences between the various embodiments, and the same or similar aspects thereof can be referenced to each other, and for the sake of brevity, they will not be described one by one.

[0022] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0023] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0024] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0025] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0026] Embodiments of the present invention can be applied to electronic devices such as terminal devices, computer systems, servers, etc., which can operate with many other general or special computing system environments or configurations. Examples of well-known terminal devices, computing systems, environments and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, servers, etc. include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, small computer systems, large computer systems, and distributed cloud computing technology environments including any of the above systems, etc.

[0027] Electronic devices such as terminal devices, computer systems, servers, etc. can be described in the general context of computer system executable instructions (such as program modules) executed by computer systems. Generally, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in a distributed cloud computing environment, where tasks are performed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules can be located on local or remote computing system storage media including storage devices.

[0028] Exemplary Methods Figure 1 1 is a flow chart of a correction method for online calculation of short-circuit current zero-crossing time based on the least squares method provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as Figure 1 As shown, the correction method 100 for online calculation of the short-circuit current zero-crossing time based on the least squares method includes the following steps: Step 101, changing the DC attenuation component according to the preset ratio requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtaining a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio; Step 102, changing the initial fault phase according to the preset phase adjustment requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtaining a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase; Step 103, obtaining an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; Step 104, using the least square method to calculate the predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault, and recording the calculation time; Step 105, calculating the compensation current zero-crossing time according to the short-circuit fault current parameter, calculation time and error compensation formula; Step 106, compensating the predicted short-circuit current zero-crossing time according to the compensation current zero-crossing time to obtain a corrected short-circuit current zero-crossing time.

[0029] Specifically, this paper takes the 220kV flexible low-frequency transmission line as an example, adopts the connection method of direct grounding of the neutral point, and the circuit breaker is operated in phases. At the same time, the power supply is considered to be a low-frequency 20Hz infinite ideal voltage source with constant output voltage and frequency and zero internal resistance. First, a theoretical analysis is carried out based on the low-frequency single-phase short-circuit fault model.

[0030] like Figure 2 As shown, CB is a low-frequency circuit breaker. U ( t ) is the power supply voltage, , U pk is the peak value of the power supply voltage, I 1( t ) is the short-circuit fault current on the power supply side, I 2( t ) is the short-circuit fault current on the load side, I F ( t ) is the short-circuit fault current to ground, w is the power angular frequency, assuming the fault occurs at t =0 time, is the initial phase angle of the short-circuit fault. The model integrates the stray inductance and resistance to simplify the calculation. The line is divided into two parts at the fault point, and the impedance from the power supply end to the fault end is the source impedance L S + R S , the impedance from the fault end to the load end is L L + R L .

[0031] When a short circuit occurs, Kirchhoff's voltage law gives: (1) The fault current can be obtained by Laplace transformation and Laplace inverse transformation: (2) In the formula I pk is the short-circuit current peak value, is the voltage-current phase difference, that is, the impedance angle from the power supply to the fault point, is the time constant in the fault line, and equation (2.2) can also be written in the form of equation (2.3).

[0032] (3) in, (4) It can be seen from formula (4) that the fault current consists of three parts: I 1A ( t ) is the AC component of the short-circuit current, which depends on the power supply voltage and the source impedance at the short circuit L S + R S ; I 1B ( t ) is the DC component of the short-circuit current, I 1C ( t ) is the current attenuation component on the power supply side before the short-circuit fault, which decays according to the exponential law. Its initial value is the same as the initial phase angle when the short-circuit fault occurs. The decay rate depends on the time constant .

[0033] The low-frequency short-circuit phase-controlled breaking algorithm requires the realization of parameter estimation, zero-crossing prediction and other functions in a very short time. Too many parameters are not conducive to improving the calculation speed and will also affect the calculation accuracy. In order to shorten the calculation time, reduce the calculation error, and avoid the influence of unimportant parameters, only the resistance and inductance of the line can be retained in the short-circuit fault analysis calculation, reducing many unnecessary parameters such as phase-to-phase capacitance, phase-to-ground capacitance, etc., so formula (5) is generally used in the calculation.

[0034] (5) Since equation (5) contains nonlinear exponential components, it is necessary to perform Taylor expansion on it. For ease of calculation, only the first two terms are retained, and we can obtain: (6) The coefficients in the formula have the following relationship with the short-circuit fault current parameters: (7) After the low-frequency short-circuit fault model is established, the short-circuit current is sampled to obtain multiple sets of current data. Substituting these data into equation (6), the following matrix can be obtained: (8) in, n is the number of sampling points, T S is the sampling period.

[0035] After obtaining the fault current sampling data, the equation needs to be solved to predict the fault current and calculate the zero-crossing point. The least squares method is used to obtain [ X ]=[X 1, X 2, X 3, X 4] is an estimate. If [ Y ] represents the current sampling value on the left, and [ H ] represents the right-hand coefficient matrix, [ X ] represents the unknown matrix, then equation (8) can be expressed in the following matrix form: (9) In the formula, [ H ] + yes[ H ] is the pseudo-inverse matrix, and [ H ] + ={[ H ] T [ H ]} -1 [ H ] T The calculation accuracy of the least squares method and the number of sampling points n The more sampling points, the higher the algorithm accuracy. In actual engineering, the phase selection control device needs to monitor the line for a long time. When the line is operating normally, a large amount of current data has been stored. Each new set of current data collected needs to calculate a new set of [ H ] + , which will greatly affect the sampling efficiency, and too much old data will also cause data saturation, which will interfere with the current data collection after the short-circuit fault, and the algorithm will lose its correction ability and fail to converge to the true value. In order to overcome data saturation and reduce the impact of old data, the Forgetting Factor Recursive Least Square (FFRLS) can be used to correct the original calculation results, that is, according to the order of data collection, the forgetting factor is set to change the weight of the data, so that the weight of the real-time data is the largest, which can greatly improve the current prediction accuracy.

[0036] Set the attenuation factor to , i ( n +1) is the latest sampled current value, h ( n +1) for [ H ] in the last line, X ( n +1) is the corrected parameter estimate, , , we can get the recursive least squares parameter estimation formula containing the forgetting factor: (10) set up , is the forgetting factor, and is generally chosen After estimating the short-circuit current parameters using the least squares method, the short-circuit current waveforms for the next few cycles can be predicted and the zero-crossing point can be calculated. If the algorithm stops calculating at t Ne , the circuit breaker opening time is t CBO , the minimum arcing time is t arc , the algorithm margin is t mg , then search for the zero-crossing start time t dkc for: (11) Take the search for the single-phase zero-crossing point as an example. t dkc Start calculating at the moment and set a search step length T srch , if any I ( t i ) I ( t i +1)≤0, then the target zero-crossing moment t xz ∈[ t i , t i +1] and take its minimum value, that is, t xz = t i ,in t i For the i The moment of searching, t i+1 = t i + T srch .

[0037] The exponential component is expanded using Taylor series, which simplifies the calculation model of short-circuit fault current. Combined with the least squares method, the amount of calculation is greatly reduced. However, after the Taylor series expansion, this technology only retains its first-order part, resulting in a large truncation error. When the least squares method is used for calculation, there is always an error between its objective function and the simplified mathematical model, and it cannot converge to the true current parameter value, thus causing a zero-crossing prediction error. At the same time, in the short-circuit current calculation of low-frequency systems, due to the influence of its inherent error, the calculation time required to converge to sufficient accuracy is long, and it is difficult to meet the requirements of phase selection and disconnection. Based on the above technology, the present invention calculates the short-circuit zero-crossing point t xz The calculation error is compensated to reduce the zero-crossing prediction error.

[0038] The present invention aims at the best performing algorithm for calculating short-circuit current parameters using the least squares method, and corrects its calculation results, which can effectively improve its calculation accuracy and shorten the calculation time. The present invention proposes a correction method for online calculation of short-circuit current zero-crossing time based on the least squares method, which specifically includes the following steps: Step S101: When using the least square method to calculate the short-circuit fault current parameters online, a simulation calculation is first performed, and the calculation time is changed to obtain a first relationship between the zero-crossing prediction error and the DC attenuation component ratio, wherein the DC attenuation component ratio is defined as the ratio of the amplitude of the short-circuit current DC attenuation component to the amplitude of the sinusoidal periodic component: T ee = k 6 I dc / I m + k 7 (12) For example, the least square method is used to calculate the short-circuit fault current parameters online. The simulation is performed when the calculation time is 8ms and 15ms respectively. The DC attenuation component changes from 0 to 70%, and the relevant error distribution is obtained. It is fitted into a curve of the positive proportional relationship between the proportion of the DC attenuation component and the zero-crossing prediction error. The relationship is as follows: T ee =0.3 I dc / I m +0.25 (13) in, T ee is the zero-crossing prediction error, I dc is the amplitude of the DC attenuation component, I m is the amplitude of the sinusoidal periodic component.

[0039] Step S102: changing the calculation time to obtain a second relationship between the zero-crossing prediction error and the initial fault phase, wherein the initial fault phase refers to the voltage phase angle at the time when the short-circuit fault occurs; T ee =- k 1sin[(- k 2 t c + k 3) α +( k 4 t c - k 5)π] (14) For example, the least square method is used to calculate the short-circuit fault current parameters online. The simulation is performed when the calculation time is 8ms and 15ms respectively. The initial phase of the fault changes from 0 to 360°, and the relevant error distribution is obtained. It is fitted into a sinusoidal function relationship curve between the initial phase angle and the zero-crossing prediction error. The relationship is as follows: T ee =-0.42sin( aα + b π) (15) a =-0.0064 t c +1.27 (16) b =0.014 t c -0.85 (17) in, T ee is the zero-crossing prediction error, t c is the algorithm calculation time, α is the initial phase value of the fault, a , b is the correlation coefficient.

[0040] Step S103: obtaining a prediction error compensation formula based on the DC attenuation component ratio and the initial fault phase according to the above relationship; T ee =- k 1sin[(- k 2 t c + k 3) α +( k 4 t c -k 5)π]+ k 6 I dc / I m + k 7 (18) For example, combining equation (13) and equation (15) yields the zero-crossing prediction error: T ee =-0.42sin[(-0.0064 t c +1.27) α +(0.014 t c -0.85)π]+0.3 I dc / I m +0.25 (19) Step S104: When the algorithm is running online, the short-circuit fault current parameters calculated by the least squares method are X 1, X 2, X 3, X 4 Estimated values ​​and calculation time t c , calculate the initial phase value of the fault α and the fault DC attenuation component ratio I dc / I m , as shown in formula (9): (20) Predict the current zero crossing point t z0 , the method is: if the algorithm calculation stops at t Ne , the circuit breaker opening time is t CBO , the minimum arcing time is t arc , the algorithm margin is t mg , then search for the zero-crossing start time t dkc for: (twenty one) from t dkc At time t, the fault current value is calculated according to formula (6): I ( t ), set a search step size T srch, if any I ( t i ) I ( t i +1)≤0, then the target zero-crossing moment t z0 ∈[ t i , t i +1] and take its minimum value, that is, t z0 = t i ,in t i For the i The moment of searching, t i+1 = t i + T srch .

[0041] Step S105: Correct the predicted current zero-crossing point according to the obtained prediction error compensation formula.

[0042] In this embodiment, the zero-crossing time after correction is t z for: t z = t z0 - T ee (twenty two) Through the above steps, the short-circuit fault current zero-crossing point is accurately predicted, the calculation method is simple and reliable, no additional circuit breaker accessories are required, and the modification cost is low.

[0043] In one embodiment of the present invention, a simulation is performed using the algorithm of the present invention, and an error analysis is performed on the simulation results to verify the accuracy and effectiveness of the present invention relative to the prior art.

[0044] (1) A white noise with a signal-to-noise ratio of 60 dB was added to the current model, and two simulation studies were performed when the algorithm calculation time was 15 ms. The initial fault phase was increased from 0° to 360°, and the proportion of the attenuated DC component was increased from no DC component to 70% attenuated DC component. The simulation results are shown in Figure 2. Figure 3 and Figure 4 shown.

[0045] Depend on Figure 3It can be seen that the error range of the zero-crossing point predicted by the prior art is [-0.25ms, 0.23ms], while after compensation by the algorithm of the present invention, the error of the zero-crossing point prediction can be reduced to ±0.1ms, with a maximum error of 0.094ms. The accuracy of the algorithm in predicting the zero-crossing point is improved by 62%; Figure 4 After compensation, the predicted zero-crossing error of the algorithm changes obviously with the DC component. The maximum error of the prior art can reach 0.152ms. After compensation by the algorithm of the present invention, the maximum error is reduced to 0.086ms, and the accuracy is improved by 43.4%. The larger the proportion of the DC component, the more obvious the compensation effect.

[0046] (2) For the initial phase of the fault, the calculation time was set to 20 ms, and three groups of simulations were performed under the conditions of 30%, 50%, and 70% DC component proportions to demonstrate the effectiveness of the algorithm of the present invention.

[0047] The simulation results are as follows Figure 5 As shown in Figure 2, when the DC component ratio is different, the error on each error curve can be maintained within ±0.1ms. Figure 4 Take for example, the error trends after compensation are basically the same, so no additional comparative simulation is done here.

[0048] (3) The error characteristics of the improved low-frequency short-circuit phase-controlled breaking algorithm are simulated again under different calculation times to verify the overall improvement effect of the algorithm.

[0049] In order to explore the algorithm's anti-noise performance, white noise with a signal-to-noise ratio of 30dB was added to the simulation, and the algorithm calculation time was increased from 3ms to 26ms. The simulation results are as follows: Figure 6 and Figure 7 shown.

[0050] The error of the low-frequency short-circuit phase-controlled breaking algorithm predicted by the improved algorithm of the present invention with the change of the calculation time is significantly reduced compared with that before the improvement. According to the principle (99.7% probability), the calculation time required for the error to converge to ±1ms is 6ms, that is, only about 1 / 8 of the low-frequency cycle needs to be sampled and calculated, which is 18ms shorter than before the improvement; as the calculation time increases, the minimum value of the error is finally approached to ±0.06 ms, which is much better than the ±0.3ms before the improvement.

[0051] exist Figure 7On the basis of the error boundary of the low-frequency short-circuit phase-controlled breaking algorithm after the algorithm of the present invention is improved, and compared with the error boundary curves of 50Hz and before the algorithm is improved. It can be seen that under the noise level of 30dB, the error boundary curve of the improved algorithm of the present invention is significantly different from that before the improvement, and is very close to the performance under the power frequency. The error of the improved algorithm of the present invention is still relatively large when the calculation time is short, but the convergence speed is extremely fast. When the calculation time is only 14ms, the predicted zero-crossing error can be converged to ±0.1ms, which is faster than 17ms at the power frequency. According to the relay protection response requirements of the existing power system, in a limited sampling window, the improved low-frequency short-circuit phase-controlled breaking algorithm of the present invention can keep the predicted zero-crossing error within ±0.1ms, meeting the actual engineering requirements. The shorter the calculation time, the more target zero-crossing points can be selected by the circuit breaker, and the short-circuit fault clearing time will be shorter, reducing the impact of the short-circuit fault on the system, which is conducive to the stable operation of the power system.

[0052] Therefore, the present invention uses simulation to obtain the corresponding relationship between the DC attenuation component amplitude ratio and the fault voltage phase angle of the zero-crossing prediction error, and fits it into a mathematical equation, thereby obtaining a compensation formula for the zero-crossing prediction error, compensating for the short-circuit fault current zero-crossing prediction error, and improving the short-circuit fault current zero-crossing prediction accuracy and the convergence speed of the algorithm. This solves the problem that the prior art has low prediction accuracy for the short-circuit fault current zero-crossing, long calculation time, and cannot meet the requirements of phase selection and breaking.

[0053] Exemplary Devices Figure 8 FIG. 1 is a schematic diagram of a correction device for online calculation of short-circuit current zero-crossing time based on the least squares method provided by an exemplary embodiment of the present invention. Figure 8 As shown, the device 800 includes: A first simulation calculation module 810 is used to change the DC attenuation component according to the preset ratio requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio; The second simulation calculation module 820 is used to change the initial fault phase according to the preset phase adjustment requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase; An obtaining module 830 is used to obtain an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; A first calculation module 840 is used to calculate the predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault by using the least square method, and record the calculation time; A second calculation module 850, used to calculate the compensation current zero-crossing time according to the short-circuit fault current parameter, the calculation time and the error compensation formula; The compensation module 860 is used to compensate the predicted short-circuit current zero-crossing time according to the compensation current zero-crossing time to obtain the corrected short-circuit current zero-crossing time.

[0054] Optionally, the first simulation calculation module 810 includes: The first determination submodule is used to determine the variation range of the DC attenuation component of the low-frequency power system; The second determination submodule is used to set multiple DC attenuation component ratios within a variation range and determine a preset ratio requirement; A first simulation calculation submodule, used to change the DC attenuation component according to a preset ratio requirement to perform simulation calculations respectively, and calculate the first short-circuit current zero-crossing time using the least square method at a plurality of preset first calculation time points; A third determination submodule is used to determine multiple groups of first short-circuit current zero-crossing time prediction errors according to the calculated multiple groups of first short-circuit current zero-crossing time and multiple first calculation time points; The first fitting submodule is used to fit multiple groups of first short-circuit zero-crossing time prediction errors and corresponding multiple groups of DC attenuation component ratios to obtain a first relationship between the zero-crossing time prediction errors and the DC attenuation component ratios.

[0055] Optionally, the second simulation calculation module 820 includes: A fourth determination submodule is used to determine a fault initial phase change interval of the low-frequency power system; A fifth determination submodule, used to set a plurality of fault initial phases within the variation interval and determine a preset phase adjustment requirement; A second simulation calculation submodule, used to change the initial phase of the fault according to the preset phase adjustment requirement to perform simulation calculation, and calculate the second short-circuit current zero-crossing time using the least square method at multiple preset second calculation time points; A sixth determination submodule, configured to determine a plurality of groups of second short-circuit current zero-crossing time prediction errors according to the calculated plurality of groups of second short-circuit current zero-crossing time and a plurality of second calculation time points; The second fitting submodule is used to fit multiple groups of second short-circuit zero-crossing time prediction errors and corresponding multiple groups of fault initial phases to obtain a second relationship between the short-circuit zero-crossing time prediction errors and the fault initial phases.

[0056] Optionally, the error compensation formula is: In the formula, t c To calculate the time, is the fault initial phase, I dc / I m is the DC attenuation component ratio, k 1. k 2. k 3. k 4 and k 5 is the fitting parameter in the second relationship, k 6 and k 7 is the fitting parameter in the first relationship.

[0057] Optionally, the second calculation module 850 includes: The first calculation submodule is used to calculate the fault initial phase value and the fault DC attenuation component ratio according to the short-circuit fault current parameter; The second calculation submodule is used to calculate the compensation current zero-crossing time according to the initial phase value of the fault, the proportion of the fault DC attenuation component and the calculation time by using the error compensation formula.

[0058] Optionally, the fault initial phase value And the proportion of the fault DC attenuation component I dc / I m The calculation formula is: in, X 1. X 2. X 3 and X 4 is the short-circuit fault current parameter.

[0059] Exemplary Electronic Devices Fig. 9 This is a structure of an electronic device provided by an exemplary embodiment of the present invention. Fig. 9 As shown, the electronic device 90 includes one or more processors 91 and a memory 92 .

[0060] The processor 91 may be a central processing unit (CPU) or other forms of processing units having data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0061] The memory 92 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, a random access memory (RAM) and / or a cache memory (cache), etc. The non-volatile memory may include, for example, a read-only memory (ROM), a hard disk, a flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 91 may run the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above and / or other desired functions. In one example, the electronic device may also include: an input device 93 and an output device 94, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0062] In addition, the input device 93 may also include, for example, a keyboard, a mouse, and the like.

[0063] The output device 94 can output various information to the outside. The output device 94 can include, for example, a display, a speaker, a printer, a communication network and a remote output device connected thereto.

[0064] Of course, to simplify, Fig. 9 Only some of the components related to the present invention in the electronic device are shown, and components such as a bus, an input / output interface, etc. are omitted. In addition, the electronic device may further include any other appropriate components according to specific application conditions.

[0065] Exemplary computer program products and computer-readable storage media In addition to the above-mentioned methods and devices, an embodiment of the present invention may also be a computer program product, which includes computer program instructions, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above-mentioned "Exemplary Method" section of this specification.

[0066] The computer program product may be written in any combination of one or more programming languages ​​to write program code for performing the operations of the embodiments of the present invention, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0067] In addition, an embodiment of the present invention may also be a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, enable the processor to execute the steps of the method according to various embodiments of the present invention described in the above “Exemplary Method” section of this specification.

[0068] The computer readable storage medium can adopt any combination of one or more readable media. The readable medium can be a readable signal medium or a readable storage medium. The readable storage medium can include, for example, but is not limited to, a system, system or device of electricity, magnetism, light, electromagnetic, infrared, or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of readable storage media include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0069] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. must be possessed by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and facilitation of understanding, rather than limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0070] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0071] The block diagrams of the devices, systems, equipment, and systems involved in the present invention are only illustrative examples and are not intended to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagram. As will be appreciated by those skilled in the art, these devices, systems, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open words, referring to "including but not limited to", and can be used interchangeably with them. The words "or" and "and" used here refer to the words "and / or" and can be used interchangeably with them, unless the context clearly indicates otherwise. The word "such as" used here refers to the phrase "such as but not limited to", and can be used interchangeably with it.

[0072] The method and system of the present invention may be implemented in many ways. For example, the method and system of the present invention may be implemented by software, hardware, firmware or any combination of software, hardware, firmware. The above order of steps for the method is only for illustration, and the steps of the method of the present invention are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present invention may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.

[0073] It should also be noted that in the system, device and method of the present invention, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent schemes of the present invention. The above description of the disclosed aspects is provided to enable any technician in the field to make or use the present invention. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined here can be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not intended to be limited to the aspects shown here, but in accordance with the widest range consistent with the principles and novel features disclosed here.

[0074] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present invention to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A correction method for online calculation of short-circuit current zero-crossing time based on least squares method, characterized in that: include: According to the preset ratio requirement of the low-frequency power system, the DC attenuation component is changed to perform short-circuit fault simulation calculations respectively, and a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio is obtained; According to the preset phase adjustment requirements of the low-frequency power system, the initial fault phase is changed to perform short-circuit fault simulation calculations respectively, and a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase is obtained; Obtaining an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; The predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault are calculated using the least square method, and the calculation time is recorded; Calculating the compensation current zero-crossing time according to the short-circuit fault current parameter, the calculation time and the error compensation formula; The predicted short-circuit current zero-crossing time is compensated according to the compensation current zero-crossing time to obtain a corrected short-circuit current zero-crossing time.

2. The method according to claim 1, characterized in that According to the preset ratio requirements in the low-frequency power system, the DC attenuation component is changed to perform short-circuit fault simulation calculations respectively, and the first relationship between the zero-crossing time prediction error and the DC attenuation component ratio is obtained, including: Determining a variation range of a DC attenuation component of the low-frequency power system; Setting multiple DC attenuation component ratios within the variation range to determine a preset ratio requirement; According to the preset ratio requirement, the DC attenuation component is changed to perform simulation calculations respectively, and the first short-circuit current zero-crossing time is calculated by using the least square method at multiple preset first calculation time points; Determine multiple groups of first short-circuit current zero-crossing time prediction errors according to multiple groups of calculated first short-circuit current zero-crossing time and multiple first calculation time points; A plurality of groups of first short-circuit zero-crossing time prediction errors and a plurality of corresponding groups of direct current attenuation component ratios are fitted to obtain a first relationship between the zero-crossing time prediction errors and the direct current attenuation component ratios.

3. The method according to claim 1, characterized in that According to the preset phase adjustment requirement in the low-frequency power system, the initial fault phase is changed to perform short-circuit fault simulation calculations respectively, and a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase is obtained, including: Determining a fault initial phase change interval of the low-frequency power system; Setting a plurality of fault initial phases within the variation interval and determining a preset phase adjustment requirement; According to the preset phase adjustment requirement, the initial phase of the fault is changed to perform simulation calculation, and the second short-circuit current zero-crossing time is calculated by using the least square method at multiple preset second calculation time points; Determine multiple groups of second short-circuit current zero-crossing time prediction errors according to the calculated multiple groups of second short-circuit current zero-crossing time and multiple second calculation time points; A plurality of groups of the second short-circuit zero-crossing time prediction errors and a plurality of corresponding groups of fault initial phases are fitted to obtain a second relationship between the short-circuit zero-crossing time prediction errors and the fault initial phases.

4. The method according to claim 1, characterized in that: The error compensation formula is: In the formula, t c To calculate the time, is the fault initial phase, I dc / I m is the DC attenuation component ratio, k 1. k 2. k 3. k 4 and k 5 is the fitting parameter in the second relationship, k 6 and k 7 is the fitting parameter in the first relationship.

5. The method according to claim 1, characterized in that Calculating the compensation current zero-crossing time according to the short-circuit fault current parameter, the calculation time and the error compensation formula includes: Calculate the fault initial phase value and the fault DC attenuation component ratio according to the short-circuit fault current parameter; The error compensation formula is used to calculate the compensation current zero-crossing time according to the fault initial phase value, the fault DC attenuation component ratio and the calculation time.

6. The method according to claim 5, characterized in that The fault initial phase value And the fault DC attenuation component ratio I dc / I m The calculation formula is: in, X 1. X 2. X 3 and X 4 is the short-circuit fault current parameter.

7. A correction device for online calculation of short-circuit current zero-crossing time based on the least squares method, characterized in that: include: A first simulation calculation module is used to change the DC attenuation component according to the preset ratio requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a first relationship between the zero-crossing time prediction error and the DC attenuation component ratio; A second simulation calculation module is used to change the initial fault phase according to the preset phase adjustment requirement of the low-frequency power system to perform short-circuit fault simulation calculations respectively, and obtain a second relationship between the short-circuit zero-crossing time prediction error and the initial fault phase; An obtaining module, used for obtaining an error compensation formula for predicting the current zero-crossing time according to the first relationship and the second relationship; A first calculation module is used to calculate the predicted short-circuit current zero-crossing time and short-circuit fault current parameters of the short-circuit fault by using the least square method, and record the calculation time; A second calculation module, used for calculating the compensation current zero-crossing time according to the short-circuit fault current parameter, the calculation time and the error compensation formula; The compensation module is used to compensate the predicted short-circuit current zero-crossing time according to the compensation current zero-crossing time to obtain the corrected short-circuit current zero-crossing time.

8. The device according to claim 7, characterized in that The first simulation calculation module includes: A first determination submodule is used to determine a variation range of a DC attenuation component of the low-frequency power system; A second determination submodule is used to set multiple DC attenuation component ratios within the variation range to determine a preset ratio requirement; A first simulation calculation submodule, used to change the DC attenuation component according to the preset ratio requirement to perform simulation calculations respectively, and calculate the first short-circuit current zero-crossing time using the least square method at multiple preset first calculation time points; A third determination submodule is used to determine multiple groups of first short-circuit current zero-crossing time prediction errors according to the calculated multiple groups of first short-circuit current zero-crossing time and multiple first calculation time points; The first fitting submodule is used to fit multiple groups of first short-circuit zero-crossing time prediction errors and corresponding multiple groups of DC attenuation component ratios to obtain a first relationship between the zero-crossing time prediction errors and the DC attenuation component ratios.

9. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 6.

10. An electronic device, characterized in that: The electronic device comprises: processor; a memory for storing instructions executable by the processor; The processor is used to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1 to 6.

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