A DC transformer transient performance verification method, device, equipment and medium

Abstract

The present invention proposes a method, device, equipment and medium for checking the transient performance of a DC transformer, which belongs to the technical field of power equipment measurement and calibration. First, the output signals of a standard DC transformer and a DC transformer under test are obtained, and multi-layer wavelet transform preprocessing is performed; then, the wavelet coefficients of any level are divided into several amplitude segments from the minimum value to the maximum value according to equal amplitude intervals, and the amplitude upper limit value of the amplitude segment that meets the preset conditions is taken as the steady-state judgment threshold; then, the step characteristic value is screened from the modulus maximum value of each sub-interval through the wavelet change modulus maximum singularity detection algorithm; then, the starting point and end point of the step interval are searched using the steady-state judgment threshold and the step characteristic value; finally, based on the divided step interval and steady-state interval, transient parameter calculation and transient performance verification are performed. In this way, the steady-state interval and step interval of the step waveform can be automatically divided, thereby effectively improving the accuracy of the DC transformer transient performance verification.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric power equipment measurement and calibration, and more specifically, relates to a method, device, equipment and medium for calibrating transient performance of a direct current transformer. Background Art

[0002] Flexible DC transmission technology is widely used in island power supply, multi-terminal interconnection, urban distribution network transformation, etc. Since a DC side fault in a flexible DC transmission system may instantly generate a huge fault current, in order to ensure the stability of the power system, the protection control signal should have a high sampling speed and a wide bandwidth, which puts forward high requirements on the transient characteristics of the DC electronic transformer in the flexible DC transmission system.

[0003] According to the requirements of GB / T 20840.15, the transient performance of DC transformers is generally verified by measuring step response, and its indicators mainly include overshoot, rise / fall time, dead time, response time, settling time and other parameters. At present, a variety of verification schemes have been proposed: measure the DC transient step current waveform through an oscilloscope, manually calibrate the step interval according to the waveform after recording; convert the transient current into a specific format signal and send it to a commercial calibrator, whose background system calculates the rise time, overshoot and response time after waveform interpolation; build a transient verification platform with NI high-speed acquisition card as the core, use the average method and majority method to divide the high and low reference levels, and calculate various transient performance parameters after linear interpolation between adjacent sampling points; increase the sampling rate of the step segment signal through resampling and then interpolate to calculate the rise time, response time, etc.

[0004] However, the existing verification method does not automatically divide the steady-state interval and step interval of the step waveform according to a reasonable algorithm and perform subsequent transient performance parameter calculations based on this, resulting in low accuracy of subsequent transient performance verification. Summary of the invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides a method, device, equipment and medium for verifying the transient performance of a DC transformer to solve the problems of low time accuracy, insufficient adaptability and low calculation accuracy in the existing method for verifying the transient performance of a DC transformer.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for verifying transient performance of a DC transformer, comprising:

[0007] Perform the following operations on the standard DC transformer and the DC transformer under test respectively:

[0008] S1, obtaining the output signal within a preset time length;

[0009] S2, performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients;

[0010] S3, dividing the wavelet coefficients of any level from the minimum value to the maximum value into a number of amplitude segments according to equal amplitude intervals, if the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds a preset proportion threshold, taking the amplitude upper limit value of the certain amplitude segment as the steady-state judgment threshold, and executing S4; otherwise, obtaining the output signal within the next preset time length, and jumping to S2;

[0011] S4, dividing the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to the sampling time, and then filtering the modulus maxima of each sub-interval to obtain a step eigenvalue by using a wavelet change modulus maximum singularity detection algorithm;

[0012] S5, for any level of wavelet coefficients, search forward and backward from the step eigenvalue on the time axis to find M and N consecutive wavelet coefficients that are smaller than the steady-state determination threshold, respectively, and take the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals;

[0013] S6, based on the divided step interval and steady-state interval, transient parameter calculation is performed;

[0014] The transient performance of the DC transformer under test is verified by combining the transient parameters of the standard DC transformer and the DC transformer under test.

[0015] Furthermore, before obtaining the output signals of the standard DC transformer and the DC transformer under test within a preset time period, it also includes: synchronizing the sampling clocks of the standard DC transformer and the DC transformer under test by using a clock synchronization module.

[0016] Furthermore, any one of the levels is the highest level.

[0017] Further, the steady-state interval includes a low steady-state interval and a high steady-state interval;

[0018] Before calculating the transient parameters, the method further includes:

[0019] Calculating the variance of the sampling values ​​in the low steady-state interval, and when the variance of the sampling values ​​in the low steady-state interval is greater than a first preset variance threshold, reducing the length of the low steady-state interval for calculating the low reference level point by point until the variance of the sampling values ​​in the low steady-state interval is less than the first preset variance threshold;

[0020] Calculate the variance of the sampling values ​​in the high steady-state interval, and when the variance of the sampling values ​​in the high steady-state interval is greater than a second preset variance threshold, reduce the length of the high steady-state interval used to calculate the high reference level point by point until the variance of the sampling values ​​in the high steady-state interval is less than the second preset variance threshold.

[0021] Further, the difference between the high and low reference levels is recorded as the 100% step amplitude;

[0022] After interpolation processing is performed on the sampled value data in the step interval, the amplitude and time corresponding to the a% amplitude are searched in the interpolated data according to the preset detection point amplitude parameter a%, and the transient parameters are calculated.

[0023] In a second aspect, the present invention provides a DC transformer transient performance verification device, comprising:

[0024] A signal acquisition module, used to acquire an output signal within a preset time length;

[0025] A wavelet transform module, used for performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients;

[0026] A steady-state determination threshold detection module is used to divide the wavelet coefficients of any level from the minimum value to the maximum value into a number of amplitude segments according to equal amplitude intervals. If the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds a preset proportion threshold, the amplitude upper limit value of the certain amplitude segment is taken as the steady-state determination threshold, and the operation of the step eigenvalue detection module is performed; otherwise, the output signal within the next preset time length is obtained, and the operation of the wavelet transformation module is performed;

[0027] A step eigenvalue detection module is used to divide the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to the sampling time, and then filter the step eigenvalues ​​from the modulus maxima of each sub-interval through a wavelet change modulus maximum singularity detection algorithm;

[0028] An interval division module is used for searching forward and backward from the step characteristic value on the time axis for any level of wavelet coefficients to find M and N consecutive wavelet coefficients that are smaller than the steady-state determination threshold, respectively, and taking the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals;

[0029] A transient parameter calculation module is used to calculate transient parameters based on the divided step interval and steady-state interval;

[0030] The transient performance verification module is used to perform transient performance verification on the DC transformer under test by combining transient parameters of a standard DC transformer and the DC transformer under test.

[0031] In a third aspect, the present invention provides an electronic device comprising: a memory and at least one processor; the memory stores computer-executable instructions; the at least one processor executes the computer-executable instructions stored in the memory, so that the at least one processor executes the method described in the first aspect.

[0032] In a fourth aspect, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions. When a processor executes the computer-executable instructions, the method described in the first aspect is implemented.

[0033] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0034] (1) The present invention introduces wavelet transform, first determines the steady-state judgment threshold and step characteristic value, then uses the steady-state judgment threshold and step characteristic value to search for the starting point and end point of the step interval, thereby realizing the adaptive division of the steady-state interval and the step interval in the step waveform; finally, based on the divided step interval and steady-state interval, transient parameter calculation and transient performance verification are performed. In this way, the steady-state interval and step interval of the step waveform are automatically divided by a reasonable algorithm, and the present invention can effectively improve the accuracy of transient performance verification of the DC transformer.

[0035] (2) The present invention synchronizes time through a clock synchronization module to achieve accurate positioning of the sampling time, thereby improving the accuracy of transient parameter calculation.

[0036] (3) The present invention adjusts the length of the interval used to calculate the high and low reference levels by comparing the variance of the sampling values ​​in the steady-state interval, thereby further improving the accuracy of the transient performance verification of the DC transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a flow chart of a method for verifying transient performance of a DC transformer provided by the present invention;

[0038] Figure 2 A structural block diagram of a DC transformer transient performance verification transposition provided by the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Embodiment 1

[0041] See also Figure 1 The present invention provides a method for verifying transient performance of a DC transformer, comprising:

[0042] S1 to S6 are performed on the standard DC transformer and the DC transformer under test respectively to obtain transient parameters of the standard DC transformer and the DC transformer under test.

[0043] S1, obtaining the output signal within a preset time length.

[0044] It can be understood that the standard DC transformer and the DC transformer under test respond to the same excitation.

[0045] Specifically, the output signal within a preset time length is obtained through the data acquisition and synchronization unit. For example, the preset time length may be 1 ms. The data acquisition and synchronization unit includes a clock synchronization module, an analog quantity acquisition control module, a digital message analysis module and an interaction module.

[0046] In this embodiment, the data acquisition and synchronization unit has an optical ST data receiving port, an optical ST synchronization input port, an optical ST synchronization output port, an RJ45 Ethernet communication port and an analog input port.

[0047] The clock synchronization module receives the first synchronization signal through the optical ST synchronization input port, automatically identifies the type of the first synchronization signal and parses it to obtain the synchronization time information, adjusts the crystal oscillator division coefficient of the FPGA according to the synchronization time information to generate a system clock with high time accuracy, and generates time information based on the synchronization time information and the system clock, and generates a second synchronization signal to output through the optical ST synchronization output port.

[0048] The analog quantity acquisition control module is configured with a sampling rate of 4kHz to collect the standard DC transformer analog quantity, and obtains time information from the clock synchronization module during sampling, and marks each sampled value with a time stamp.

[0049] The digital message parsing module receives the digital quantity of the DC transformer under test through the optical ST data receiving port, automatically identifies the encoding type of the FT3 protocol and automatically adapts the data baud rate, parses the message to obtain the sampled value data, and obtains the time information from the clock synchronization module when parsing the message, and timestamps each sampled value.

[0050] The interactive module collects a certain number of analog sampling point data and a certain number of digital sampling point data, frames them into UDP messages in a custom format, and sends them out through the RJ45 Ethernet port.

[0051] S2, performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients.

[0052] Specifically, after receiving the sampling values ​​within a preset time length, a multi-level wavelet transform is performed on the sampling values ​​to obtain the highest level wavelet coefficients and other level wavelet coefficients.

[0053] S3, divide the wavelet coefficients of any level into several amplitude segments from the minimum value to the maximum value according to equal amplitude intervals. If the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds the preset proportion threshold, take the amplitude upper limit value of the certain amplitude segment as the steady-state judgment threshold, and execute S4; otherwise, obtain the output signal within the next preset time length, and jump to S2.

[0054] Exemplarily, taking the highest level as an example, the total number of data at the highest level is Nt, and the wavelet coefficients of the highest level are divided into 2000 amplitude segments from the minimum value to the maximum value, and the number of data Ni of the wavelet coefficients in different amplitude segments is counted. If the proportion of Ni in a certain amplitude segment to Nt exceeds the preset proportion threshold, the amplitude upper limit value of the amplitude segment is taken as the steady-state judgment threshold; otherwise, the output signal within the next preset time length is obtained, and jump to S2.

[0055] It is understandable that we hope that the output signal obtained within the preset time length includes a step interval, so in this embodiment, the preset ratio threshold is greater than 50%, preferably 90%.

[0056] It should be noted that it is theoretically feasible to select wavelet coefficients at any level, but the highest level wavelet coefficients are preferred.

[0057] S4, dividing the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to sampling time, and then filtering the modulus maxima of each sub-interval to obtain the step eigenvalue through the wavelet change modulus maximum singularity detection algorithm.

[0058] Exemplarily, in the highest level wavelet coefficients, 10 consecutive wavelet coefficients are taken as a sub-interval to obtain the local wavelet coefficient modulus maximum of each sub-interval; in the wavelet coefficients of other levels, when the wavelet coefficient corresponding to the local wavelet coefficient modulus maximum of a sub-interval is also a local modulus maximum, and the positive and negative polarities are consistent, and the modulus value is positively correlated with the level, the local wavelet coefficient modulus maximum of the sub-interval is regarded as a step eigenvalue.

[0059] S5, for any level of wavelet coefficients, search forward and backward from the step eigenvalue on the time axis to find M and N consecutive wavelet coefficients that are smaller than the steady-state judgment threshold, respectively, and take the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals.

[0060] Exemplarily, for the highest level wavelet coefficient, when searching forward from the step eigenvalue on the time axis, when the wavelet coefficients of 10 consecutive points are all less than the steady-state judgment threshold, the latest sampling time corresponding to the 10 points is set as the starting point of the step interval; when searching backward from the step eigenvalue, considering that step waveforms often have overshoot and ringing, when the wavelet coefficients of 60 consecutive points are all less than the steady-state judgment threshold, the earliest sampling time corresponding to the 60 points is set as the end point of the step interval. The interval between the step interval start point and the step interval end point is regarded as the step interval, and the remaining intervals are regarded as the steady-state interval.

[0061] S6, based on the divided step interval and steady-state interval, transient parameter calculation is performed;

[0062] Specifically, the steady-state interval includes a low steady-state interval and a high steady-state interval. Taking the low steady-state interval as an example, the midpoint of the low steady-state interval is used as the center of the reference interval, and half of the length of the low steady-state interval is used as the radius of the reference interval. The variance in the reference interval is calculated. If the variance is greater than the preset variance threshold, the reference interval radius is reduced point by point and the variance is calculated and judged again until the reference interval variance is less than the preset variance threshold. The high steady-state interval is processed in the same way and will not be repeated here.

[0063] After adjusting the length of the interval used to calculate the high and low reference levels, the reference levels in the steady-state interval are calculated using the average value or density distribution mode method to obtain the high and low reference levels.

[0064] Further, the step interval sampling value data is processed by cubic Hermite interpolation to obtain the step interval interpolation waveform, and the waveforms between adjacent points in the step interval interpolation waveform are filled by linear interpolation, and the difference between the high and low reference levels of the adjacent steady-state intervals is regarded as 100% step amplitude. The preset tolerance is 5%, then the detection point amplitude parameter a% is: 0%, 10%, 50%, 90%, 97.5%, 102.5%, and the amplitude and time corresponding to the detection point amplitude parameter a% are calculated. The transient parameters are calculated as follows: overshoot is the ratio of the difference between the maximum value of the step waveform and the high reference level to the step amplitude; rise / fall time is the difference between the 90% amplitude point and the 10% amplitude point of the step waveform; dead time is the difference between the 50% amplitude point of the step waveform of the tested DC transformer and the amplitude point of the step waveform of the standard DC transformer; response time is the difference between the 97.5% amplitude point and the 0% amplitude point of the step waveform; establishment time is the difference between the maximum value of the 97.5% amplitude point and the 102.5% amplitude point and the 0% amplitude point.

[0065] After the transient parameters of the standard DC transformer and the DC transformer under test are obtained by calculation, the transient performance of the DC transformer under test is verified by combining the transient parameters of the standard DC transformer and the DC transformer under test.

[0066] Specifically, the overshoot, rise / fall time, response time, and setup time of the standard DC transformer are compared with those of the DC transformer under test, and the deviation is calculated, which is combined with the dead time as the transient characteristics of the DC transformer under test. The transient characteristics of the DC transformer under test are checked according to the required transient characteristics verification requirements to achieve the transient characteristics verification of the DC transformer under test. For example, when the overshoot error between the DC transformer under test and the standard DC transformer is within 20%, the rise / fall time error is within 10%, the response time error is within 10%, the setup time error is within 10%, and the dead time is within 250 microseconds, the transient characteristics of the DC transformer under test are considered qualified.

[0067] Embodiment 2

[0068] Figure 2 A structural block diagram of a DC transformer transient performance verification transposition provided by the present invention includes:

[0069] A signal acquisition module, used to acquire an output signal within a preset time length;

[0070] A wavelet transform module, used for performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients;

[0071] A steady-state determination threshold detection module is used to divide the wavelet coefficients of any level from the minimum value to the maximum value into a number of amplitude segments according to equal amplitude intervals. If the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds a preset proportion threshold, the amplitude upper limit value of the certain amplitude segment is taken as the steady-state determination threshold, and the operation of the step eigenvalue detection module is performed; otherwise, the output signal within the next preset time length is obtained, and the operation of the wavelet transformation module is performed;

[0072] A step eigenvalue detection module is used to divide the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to the sampling time, and then filter the step eigenvalues ​​from the modulus maxima of each sub-interval through a wavelet change modulus maximum singularity detection algorithm;

[0073] An interval division module is used for searching forward and backward from the step characteristic value on the time axis for any level of wavelet coefficients to find M and N consecutive wavelet coefficients that are smaller than the steady-state determination threshold, respectively, and taking the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals;

[0074] A transient parameter calculation module is used to calculate transient parameters based on the divided step interval and steady-state interval;

[0075] The transient performance verification module is used to perform transient performance verification on the DC transformer under test by combining transient parameters of a standard DC transformer and the DC transformer under test.

[0076] In this embodiment, for the specific implementation of each module, please refer to the description in the first embodiment, which will not be repeated here.

[0077] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for checking transient performance of a DC transformer, characterized in that: include: Perform the following operations on the standard DC transformer and the DC transformer under test respectively: S1, obtaining the output signal within a preset time length; S2, performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients; S3, dividing the wavelet coefficients of any level from the minimum value to the maximum value into a number of amplitude segments according to equal amplitude intervals, if the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds a preset proportion threshold, taking the amplitude upper limit value of the certain amplitude segment as the steady-state judgment threshold, and executing S4; otherwise, obtaining the output signal within the next preset time length, and jumping to S2; S4, dividing the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to the sampling time, and then filtering the modulus maxima of each sub-interval to obtain a step eigenvalue by using a wavelet change modulus maximum singularity detection algorithm; S5, for any level of wavelet coefficients, search forward and backward from the step eigenvalue on the time axis to find M and N consecutive wavelet coefficients that are smaller than the steady-state determination threshold, respectively, and take the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals; S6, based on the divided step interval and steady-state interval, transient parameter calculation is performed; The transient performance of the DC transformer under test is verified by combining the transient parameters of the standard DC transformer and the DC transformer under test.

2. The method according to claim 1, characterized in that Before obtaining the output signals of the standard DC transformer and the DC transformer under test within a preset time period, the method also includes: synchronizing the sampling clocks of the standard DC transformer and the DC transformer under test by using a clock synchronization module.

3. The method according to claim 1 or 2, characterized in that: Any of the levels described is the highest level.

4. The method according to claim 1 or 2, characterized in that: The steady-state interval includes a low steady-state interval and a high steady-state interval; Before calculating the transient parameters, the method further includes: Calculating the variance of the sampling values ​​in the low steady-state interval, and when the variance of the sampling values ​​in the low steady-state interval is greater than a first preset variance threshold, reducing the length of the low steady-state interval for calculating the low reference level point by point until the variance of the sampling values ​​in the low steady-state interval is less than the first preset variance threshold; Calculate the variance of the sampling values ​​in the high steady-state interval, and when the variance of the sampling values ​​in the high steady-state interval is greater than a second preset variance threshold, reduce the length of the high steady-state interval used to calculate the high reference level point by point until the variance of the sampling values ​​in the high steady-state interval is less than the second preset variance threshold.

5. The method according to claim 4, characterized in that The difference between the high and low reference levels is recorded as the 100% step amplitude; After interpolation processing is performed on the sampled value data in the step interval, the amplitude and time corresponding to the a% amplitude are searched in the interpolated data according to the preset detection point amplitude parameter a%, and the transient parameters are calculated.

6. A DC transformer transient performance verification device, characterized in that: include: A signal acquisition module, used to acquire an output signal within a preset time length; A wavelet transform module, used for performing multi-layer wavelet transform on the output signal to obtain wavelet coefficients; A steady-state determination threshold detection module is used to divide the wavelet coefficients of any level from the minimum value to the maximum value into a number of amplitude segments according to equal amplitude intervals. If the proportion of the number of data in a certain amplitude segment to the total number of data at any level exceeds a preset proportion threshold, the amplitude upper limit value of the certain amplitude segment is taken as the steady-state determination threshold, and the operation of the step eigenvalue detection module is performed; otherwise, the output signal within the next preset time length is obtained, and the operation of the wavelet transformation module is performed; A step eigenvalue detection module is used to divide the wavelet coefficients of any level into a number of sub-intervals at equal intervals according to the sampling time, and then filter the step eigenvalues ​​from the modulus maxima of each sub-interval through a wavelet change modulus maximum singularity detection algorithm; An interval division module is used for searching forward and backward from the step characteristic value on the time axis for any level of wavelet coefficients to find M and N consecutive wavelet coefficients that are smaller than the steady-state determination threshold, respectively, and taking the interval between the latest sampling time corresponding to the M wavelet coefficients and the earliest sampling time corresponding to the N wavelet coefficients as the step interval, and the remaining intervals as the steady-state intervals; A transient parameter calculation module is used to calculate transient parameters based on the divided step interval and steady-state interval; The transient performance verification module is used to perform transient performance verification on the DC transformer under test by combining transient parameters of a standard DC transformer and the DC transformer under test.

7. An electronic device, characterized in that: include: memory and at least one processor: The memory stores computer-executable instructions; The at least one processor executes the computer-executable instructions stored in the memory, so that the at least one processor performs the method according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the processor executes the computer-executable instructions, the method according to any one of claims 1 to 5 is implemented.

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