CN114037104B - Method and system for monitoring errors of direct current measuring device - Google Patents
Method and system for monitoring errors of direct current measuring device Download PDFInfo
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Abstract
The invention discloses a method and a system for monitoring errors of a direct current measuring device, wherein the method comprises the steps of analyzing the structure of the direct current measuring device and the arrangement mode of measuring points; setting error monitoring indexes in a hierarchical manner and making a monitoring strategy; acquiring the measurement data of the direct current measurement device at each measurement point; carrying out error monitoring calculation on the direct current measuring device according to a formulated monitoring strategy; evaluating an error evaluation of the direct current measuring device; and estimating the error of the direct current measuring device. The invention does not change the current direct current measuring device, only adds a small amount of additional equipment, can realize the real-time monitoring and quantitative evaluation of the accuracy of the direct current measuring device which operates on line, finds out, senses and warns the deterioration of the accuracy in advance in time, and greatly improves the reliability and the operation and maintenance efficiency of the equipment.
Description
Technical Field
The invention relates to the technical field of on-line operation and maintenance of a direct current transmission system, in particular to an error monitoring method of a direct current measuring device.
Background
In a direct current transmission system, a direct current converter station is provided with a large number of direct current measuring devices with different principles and different voltage levels, and the direct current measuring devices are used for transmitting real-time current values of a primary system for systems such as direct current protection and control. The accuracy of the measuring devices is directly related to the correctness of a protection system, a control system and a monitoring system of the converter station, and once the measurement is not accurate enough, the out-of-tolerance occurs, and the interlocking abnormality and the potential safety hazard brought by the out-of-tolerance are huge.
In the ultrahigh voltage direct current transmission project put into operation in China, the accuracy grade of the direct current measuring device is 0.2 grade, most of the accuracy grade is 0.5 grade, and the small amount of the accuracy grade is 0.2 grade. When the converter station is put into operation after joint adjustment and strict detection, the errors of all direct current measuring devices are consistent with the requirements and the out-of-tolerance phenomenon is avoided. However, from the current engineering operation experience, in the process of long-term online operation, with the changes of various external environments and certain links of the direct current measuring device, the error of the direct current measuring device may change, and the out-of-tolerance phenomenon may occur slowly. Although the number of direct current measuring devices with out-of-tolerance is generally less than that of direct current measuring devices with out-of-tolerance seen from the whole converter station, when the measuring error exceeds the technical index requirement, the measuring devices themselves and other external systems are not known because the measuring devices are still in the normal operation process and no self-checking abnormal information is given. That is, the measurement device will still operate with a fault even if an error overrun condition occurs.
At present, the operation and maintenance mode of the direct current measuring device is still regularly checked, the period is usually at least 1 year, or the device is overhauled after a fault occurs, the discovery and the solution of the operation and maintenance mode to the error of the measuring device are seriously delayed, the timely discovery and the maintenance cannot be realized, and the precaution cannot be realized in the bud.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide an error monitoring method and system for a direct current measuring device, which can realize real-time monitoring and quantitative evaluation on the accuracy of the direct current measuring device running on line by only adding a small amount of additional equipment without changing the conventional direct current measuring device, and timely find, sense and early warn the accuracy deterioration of the direct current measuring device, thereby greatly improving the equipment reliability and operation and maintenance efficiency of the direct current measuring device.
The invention adopts the following technical scheme:
a method for monitoring errors of a direct current measuring device comprises the following steps:
step 1: analyzing the structure of the direct current measuring device and the measuring point arrangement mode;
step 2: setting error monitoring indexes in a hierarchical manner and making a monitoring strategy according to the analysis result in the step 1;
and step 3: acquiring the measurement data of the direct current measurement device at each measurement point;
and 4, step 4: carrying out error monitoring calculation on the direct current measuring device according to a formulated monitoring strategy;
and 5: performing error evaluation of the direct current measuring device according to the calculation result of the step 4;
step 6: and (5) estimating the error of the direct current measuring device according to the error estimation calculation data in the step 5.
Preferably, in step 1, a direct current measuring device is arranged at each measuring point;
each direct current measuring device comprises a remote end module and a plurality of MUs connected with the remote end module;
and the remote module adopts double AD for sampling and outputs a double AD sampling value of the remote module through the MU connected with the remote module.
Preferably, in step 2, according to different monitoring ranges, the following error monitoring indexes are hierarchically set:
1) self dual AD difference of the remote module;
2) the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point;
3) the total content of non-characteristic subharmonic of a direct current measuring device of each measuring point in the multiple measuring points;
and (4) establishing a monitoring strategy according to the error monitoring index, and evaluating the current error state of the direct current measuring device.
Preferably, step 3 obtains the remote module double AD sampling values and the MU current value of the direct current measuring device at each measuring point.
Preferably, in step 3, after the dual AD sampling values are acquired, the acquired sampling values are calibrated at the current time based on an internal unified clock of the direct current measuring device.
Preferably, the error monitoring calculation of step 4 comprises:
calculating self double AD difference degrees of the remote module based on the double AD sampling values;
calculating the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point based on the instantaneous sampling value of the MU current value;
and calculating the total content of non-characteristic subharmonics of the direct current measuring device at each measuring point in the multi-measuring point based on the instantaneous sampling value of the MU current value.
Preferably, in step 4, it is assumed that the dual ADs of the remote modules are AD1 and AD2, respectively;
the instantaneous sample value at a certain moment of AD1 is is_ad1(n), the instantaneous sample value of AD2 at the same time is is_ad2(n), the dual AD disparity calculation method is:
Δis(n) = |is_ad2(n) - is_ad1(n）|
where n represents the sequence number of the discrete instantaneous sample value.
Preferably, in step 4, the calculation formula of the instantaneous sampled value of the MU current value is:
iMU(n) = [ is_ad2(n) + is_ad1(n）] / 2
wherein is_ad1(n) is the instantaneous sample value at a certain time of AD 1; i.e. is_ad2And (n) is an instantaneous sampling value of the AD2 at the same time.
Preferably, in step 4, based on the instantaneous sampled value of the MU current value, the current signal difference between multiple MUs of the dc current measuring device at the same measuring point is calculated, which specifically includes:
taking a sampling value sequence of a time window, performing discrete Fourier transform, and solving an effective value of a direct current signal;
respectively calculating effective values of direct current signals of multiple MUs at the same measuring point, and sequencing the effective values according to amplitude values to obtain a maximum value IMU_D_MAX(n) and a minimum value IMU_D_MIN(n)；
Then, the current signal difference between the multiple MUs of the dc current measuring device at the same measuring point is:
ΔIMU_D(n) = IMU_D_MAX(n) - IMU_D_MIN(n)。
preferably, in step 4, based on the instantaneous sampling value of the MU current value, the total content of non-characteristic subharmonics of the dc current measuring device at each measuring point in the multiple measuring points is calculated, specifically:
the result of discrete Fourier transform of the sample value sequence of MU comprisesFlow component IMU_DCharacteristic subharmonic component IMU_HxAnd a non-characteristic subharmonic component IMU_Hy；
Wherein, the value of x is N x K, N is the number of pulses of the rectifier bridge, and K is a natural number 1,2,3, … …; the value of y is the harmonic frequency left after removing direct current and x;
then, the total content of the non-characteristic subharmonics is:
AMU_H = 
wherein, the harmonic frequency of the molecule in the formula is non-characteristic harmonic frequency.
Preferably, step 5 specifically includes:
step 5.1: according to the self dual AD difference degree delta i of the same remote modules(n) calculating a current error state evaluation result P1;
step 5.2: according to the difference degree delta I of multiple MU current signals at the same measuring pointMU_D(n) calculating a current error state evaluation result P2;
step 5.3: according to the total content A of the non-characteristic subharmonic of each measuring pointMU_HCalculating a current error state evaluation result P3;
step 5.4: and taking the lowest value of P1, P2 and P3 as the final evaluation result Pn of the current error state of the direct current measuring device.
Preferably, in step 5.1, the larger i of the instantaneous sample values of the dual AD is first founds_max：
is_max = MAX( |is_ad2(n)|，|is_ad1(n）| )
Wherein is_ad1(n) is the instantaneous sample value at a certain time of AD 1; i.e. is_ad2(n) is the instantaneous sample value of AD2 at the same time;
and calculating the ratio K1 of the current instantaneous sampling value:
K1 = is_max / Ir
wherein Ir is the rated primary current value of the current direct current measuring device;
selecting values of an error coefficient K2 and a margin coefficient K3 according to the value of K1;
calculating an evaluation reference value V according to the error coefficient K2 and the margin coefficient K3L1：
VL1 = is_max * (2 *K2 ) * K3
According to the evaluation reference value VL1And double degree of difference Δ i in ADs(n), calculating an evaluation result P1:
P1 = 100 –( Δis(n)/ VL1 )*100。
preferably, in step 5.2, the effective value I of the current signal at the measuring point is first obtainedMU_D(n)：
IMU_D(n) = [ IMU1_D(n) + IMU2_D(n) + ……+ IMUT_D(n) ] / T
Wherein the measuring point has T MU, IMU1_D(n)、IMU2_D(n)、……、IMUT_D(n) the effective value of the direct current output by each MU is respectively;
then, the ratio K4 of the current effective values is calculated:
K4= IMU_D(n) / Ir
wherein Ir is the rated primary current value of the current direct current measuring device;
taking values of an error coefficient K5 and a margin coefficient K6 according to the value of K4;
calculating an evaluation reference value V according to the error coefficient K5 and the margin coefficient K6L2：
VL2 = IMU_D(n) *( 2* K5）* K6
According to the evaluation reference value VL2Degree of difference Δ I from current signalMU_D(n), calculating an evaluation result P2:
P2 = 100 –(ΔIMU_D(n)/ VL2 )*100。
preferably, first, a threshold value V for the total harmonic content is determinedL3；
Then, according to the threshold value VL3And total content of non-characteristic subharmonic AMU_HCalculating an evaluation result P3:
P3 = 100 –AMU_H *100 / VL3。
preferably, the evaluation results P1, P2 and P3 have the highest value of 100, which represents the optimal error state; the lower the value, the worse the representative error state; and when the value is 0 or negative, the error state is abnormal, and an alarm is required.
Preferably, in step 5.2, if an alarm occurs, the effective value I of the direct current output by the T sets of MUs at the same measuring point is usedMU1_D(n)，IMU2_D(n)……IMUT_D(n) are respectively related to the effective value IMU_D(n) comparison to give Δ IMU1(n)、ΔIMU2(n)、……ΔIMUT(n) sorting according to the compared amplitudes, wherein the larger the amplitude is, the higher the possibility of error out-of-tolerance is.
Preferably, step 6 is specifically:
recording and storing the error state evaluation results P1, P2 and P3 to form a history record;
carrying out data extraction on data points of the historical records for a period of time to obtain a data set P (n);
using the extracted data set P (N) as a dependent variable array, and using the corresponding time array [1,2,3 … … N ]]As an independent variable array, fitting discrete data to obtain a fitting functionf(x)Wherein, in the step (A),xis an independent variable, i.e. time;
by fitting out a functionf(x)Time of an independent variablexIncreasing t to obtain corresponding function resultf(x+t)I.e. the predicted time pointxError state results t times later.
Preferably, in step 6, a data set of the latest 1 month is extracted, and an error state from 1 day to 1 week in the future is predicted;
or extracting a data set of the last 1 year and predicting the error state of 1 week to 1 month in the future;
or extracting data sets of more than two years in the last time, and predicting the error state of 1 month to 3 months in the future.
The invention also provides an error monitoring system of the direct current measuring device, which comprises:
the analysis module is used for analyzing the structure of the direct current measuring device and the measuring point arrangement mode;
the index setting and strategy making module is used for setting error monitoring indexes in a hierarchical mode and making a monitoring strategy according to the analysis result of the analysis module;
the data acquisition module is used for acquiring the measurement data of the direct current measurement device at each measurement point;
the error monitoring and calculating module is used for carrying out error monitoring and calculation on the direct current measuring device according to a formulated monitoring strategy;
the error evaluation module is used for carrying out error evaluation on the direct current measuring device according to the calculation result of the error monitoring calculation module;
and the error estimation module is used for estimating the error of the direct current measuring device according to the error estimation calculation data of the error estimation module.
Compared with the prior art, the invention has the beneficial effects that:
the invention utilizes the self double AD difference degree of the same remote module, the multi-MU current signal difference degree of the same measuring point and the core parameter calculation and processing of 3 aspects of the total content of non-characteristic subharmonic of each measuring point, is easy to realize, avoids synchronous processing and complex calculation algorithm, and is convenient for development and engineering popularization;
the method can not only find the undetected error abnormity in time, but also pre-judge the error abnormity which possibly occurs in the future, prevent the error abnormity in the future, and improve the reliability and the operation and maintenance level of the direct current measuring device;
the method can give out a final evaluation result, and give out a score', a full score of 100, and is visual and clear;
in the application process, parameters such as margin coefficients, threshold values and the like in the method can be adjusted by combining with feedback of actual operation and maintenance, and the reliability of error situation perception is gradually optimized;
the invention does not need to change the direct current measuring device, and only adds a set of equipment arranged in the screen cabinet in the control room, thereby having small construction amount.
Drawings
FIG. 1 is a flow chart of the steps of the error monitoring method of the DC current measuring device of the present invention;
FIG. 2 is a schematic view of typical wiring of a DC converter station and the site locations of current measuring devices;
FIG. 3 is a schematic diagram of an exemplary configuration of a DC current measuring device;
FIG. 4 is a schematic diagram of the present invention for calculating the difference between current signals of multiple MUs of a DC current measuring device at the same measuring point;
FIG. 5 is a schematic diagram of the present invention calculating the total content of non-characteristic subharmonics at each measurement point;
FIG. 6 is a diagram illustrating a final evaluation result of the current error status of the DC current measuring device according to the present invention;
fig. 7 is a schematic diagram of a composition framework of an error monitoring system of the dc current measuring device according to the present invention.
Detailed Description
The present application is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present application is not limited thereby.
As shown in fig. 1, the method for monitoring the error of the dc current measuring device of the present invention includes the following steps:
step 1: analyzing the structure of the direct current measuring device and the measuring point arrangement mode;
step 2: setting error monitoring indexes in a hierarchical manner and making a monitoring strategy according to the analysis result in the step 1;
in a dc transmission system, the connection of the dc converter stations and the location of the measuring points of the current measuring device are shown in fig. 2. In fig. 2, the positions of the connection line and the measurement point are illustrated by taking the positive line of the receiving end as an example, and the same design is adopted for the Song end of the positive line and the sending end and the receiving end of the negative line. In the context of figure 2, it is shown,
~
mark outThe current measuring devices at different measuring point positions are arranged at the receiving end of the positive line and the valve hall polar current measuring device and the valve hall neutral bus current measuring device, the direct current filter is provided with a filter high-voltage side current measuring device, a filter unbalanced current measuring device and a filter low-voltage side current measuring device, and the polar line, the direct current neutral bus and the grounding electrode are also respectively provided with a polar line direct current measuring device, a direct current neutral bus current measuring device and a grounding electrode line current measuring device. The measuring device comprises a valve hall polar current measuring device, a valve hall neutral bus current measuring device, a filter high-voltage side current measuring device, a filter unbalanced current measuring device, a filter low-voltage side current measuring device, a polar line direct current measuring device, a direct current neutral bus current measuring device and an earthing electrode line current measuring device.
For the current measuring devices in the dc converter station, a typical structure diagram of each dc current measuring device is shown in fig. 3. In China, the protection devices of the direct current converter station are in a triple design, and the control devices are in a double design, namely 3 sets of protection devices are needed, and 2 sets of control devices are needed. The measurement loop of each set of device needs to be independent, so each dc measurement includes at least 6 remote modules and 5 merging units. Each far-end module is used for receiving and processing an analog signal converted by a primary sensor (shunt), performing analog-to-digital conversion and outputting a serial digital optical fiber signal, 3 far-end modules are used for a protection device, 2 far-end modules are used for a control device, and 1 far-end module is used for standby. Each merging unit MU receives and processes data of the remote module, digital signals are output according to a specified protocol after packaging, 3 MUs are used for protecting devices, and 2 MUs are used for controlling devices.
In the dc current measuring apparatus, each remote module adopts a dual ADC (Analog-to-Digital Converter) hardware sampling loop design in an Analog-to-Digital conversion link, so as to further improve the reliability of the sampling link. In the design of a dual ADC hardware sampling loop, the analog-to-digital conversion is respectively carried out by adopting double AD, the double AD is positioned on a PCB circuit board, the double AD is completely consistent on hardware, and the double AD synchronously measures the same analog input signal under the control of the same set of clock, so that two paths of AD sampling values output by each far-end module are also consistent theoretically, and the difference of the double AD sampling values can reflect the accuracy of the direct current measuring device.
Furthermore, as shown in fig. 3, the MUs in each dc current measuring device are designed in multiple ways, and a plurality of MUs correspondingly measure the primary current at the same measuring point, so the current values output by the MUs in each dc current measuring device should theoretically be consistent, and the difference of the plurality of MU current signals can reflect the accuracy of the dc current measuring device.
Furthermore, for a direct-current power transmission system, the characteristic subharmonic on the direct-current side of the direct-current power transmission system is N x K, wherein N is the number of the pulses of the rectifier bridge, and the value of N can be 6 or 12 according to specific engineering, so that the current ultrahigh-voltage direct-current power transmission system in China mainly takes 12 pulses, and the early direct-current power transmission system has 6 pulses; k takes the natural number 1,2,3 … …. That is, a certain amount of characteristic subharmonics inevitably appear in the dc current, and there is a large fluctuation in the content in the engineering practice, while the amount of non-characteristic subharmonics is relatively much smaller and stable. Therefore, the total content of the non-characteristic subharmonics can represent whether the current measuring device has measurement abnormality or not, and can reflect the accuracy of the direct current measuring device.
In order to sense the error situation of the direct current measuring devices and carry out real-time monitoring and quantitative evaluation on the accuracy of the direct current measuring devices running on line, the invention adopts the self double AD sampling value difference degree, the multi-MU current signal difference degree and/or the total content of the non-characteristic subharmonic of the same remote module of each direct current measuring device to represent and estimate the error state. Preferably, the self double AD sampling value difference degree, the multi-MU current signal difference degree and/or the total content of the non-characteristic subharmonic of the same remote module of each direct current measuring device are/is adopted for representing and pre-estimating.
It should be noted that the specific principle of the error situation sensing method and system of the dc current measuring device of the present invention is not limited to the current divider principle shown in fig. 3, and other principles of measuring devices, such as electrical or optical principles, are also applicable to the present method.
In summary, in step 1, each measuring point is provided with a direct current measuring device;
each direct current measuring device comprises a remote end module and a plurality of MUs connected with the remote end module;
and the remote module adopts double AD for sampling and outputs a double AD sampling value of the remote module through the MU connected with the remote module.
In the step 2, according to different monitoring ranges, the following error monitoring indexes are hierarchically set:
1) self dual AD difference of the remote module;
2) the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point;
3) the total content of non-characteristic subharmonic of a direct current measuring device of each measuring point in the multiple measuring points;
and (4) establishing a monitoring strategy according to the error monitoring index, and evaluating the current error state of the direct current measuring device.
And step 3: acquiring measurement data of the direct current measuring device at each measuring point, wherein the measurement data comprises a remote module double AD sampling value and an MU current value of the direct current measuring device at each measuring point;
1. the method comprises the steps of obtaining double AD sampling values of a far-end module of a direct current measuring device, and calibrating the obtained sampling values at the current moment based on an internal unified clock of the direct current measuring device after the double AD sampling values are obtained.
Specifically, the data acquisition is obtained by receiving a fiber-optic digital signal of a direct current measuring device to be subjected to error situation perception, and more specifically, by receiving an FT3 sampling data frame output by the MU. The remote module is an internal module of the direct current measuring device, and the transmission between the remote module and the MU adopts a private self-defined frame format. The MU is an external interface (a control device, a protection device, etc.) of the direct current measurement device, and the output frame format of the MU is required by standards (Q/GDW 441-. The MU functions to receive data inputs from multiple remote modules, complete synchronization, complete access, complete synchronization signal reception, send sampling values according to standard protocols, etc.
After photoelectric conversion is carried out on the multi-path optical fiber digital signals, the multi-path optical fiber digital signals are processed by a processor FPGA (or replaced by other processors capable of realizing the function), the FT3 data frame is decoded according to a standardized frame format, and double AD sampling values of all remote modules connected with the MU are extracted. And calibrating the currently extracted sampling value at the current moment based on an internal unified clock of a data receiving module of the direct current measuring device. And finally, caching the sampling value and the corresponding moment, and triggering the processor ARM (or replacing the sampling value by other processors capable of realizing the function) to read in time in an interrupt mode. In one embodiment of the invention, two processors, namely an FPGA and an ARM, are provided, wherein the former processor is responsible for frame receiving and analysis, and the latter processor is responsible for data calculation; the former is at the data receiving module and the latter is at the data processing module.
And 4, step 4: the error monitoring calculation of the direct current measuring device is carried out according to the established monitoring strategy, which comprises the following steps:
1) calculating self double AD difference degrees of the remote module based on the double AD sampling values;
the analog-to-digital conversion of the far-end module of each direct current measuring device is in a double-AD design, the double AD is on the same circuit board PCB, the hardware is in a completely consistent design, and the same analog input signal is synchronously measured under the control of the same set of clock, so that two AD sampling values output by the far-end module are consistent forever.
Suppose the instantaneous sample value at some time of AD1 of the remote module is is_ad1(n), the instantaneous sample value of AD2 at the same time is is_ad2(n), the degree of difference of the dual AD is:
Δis(n) = |is_ad2(n) - is_ad1(n）|
where n represents the sequence number of the discrete instantaneous sample value.
2) Calculating the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point based on the instantaneous sampling value of the MU current value;
as shown in fig. 3, the MU of a dc current measuring device is also designed in multiple ways. Since a plurality of sets of MUs measure primary currents at the same measuring point, the current values output by the MUs should be consistent theoretically.
For a certain MU, an instantaneous sampling value of the current value is calculated:
iMU(n) = [ is_ad2(n) + is_ad1(n）] / 2
wherein is_ad1(n) is the instantaneous sample value at a certain time of AD 1; i.e. is_ad2(n) is the instantaneous sample value of AD2 at the same time;
unlike synchronous sampling employed by the dual AD of the remote modules, sampling between sets of MUs is asynchronous sampling. In order to avoid the calculation burden and additional errors brought by synchronous processing, the current signal difference degree calculation of multiple MUs does not perform difference degree calculation based on instantaneous sampling values any more, but a sampling value sequence of a time window is used for calculating the effective value of a direct current signal. Fig. 4 is a schematic diagram illustrating a method for calculating a difference degree of current signals between multiple MUs of a dc current measuring device at the same measuring point in the error situation awareness method for the dc current measuring device of the present invention.
In one embodiment of the invention, the time window length is 0.1 s. By discrete Fourier transform, DFT, on i within a time windowMU(n) processing the sampling value sequence to obtain the effective value I of the direct current signalMU_D(n) of (a). For a plurality of sets of MUs at the same measuring point, assuming that T sets of MUs are provided, the effective values of the output direct current are respectively as follows: i isMU1_D(n)，IMU2_D(n)，……，IMUT_D(n) of (a). Sorting the values according to the amplitude value to obtain the maximum value IMU_D_MAX(n) and a minimum value IMU_D_MIN(n)。
Then, the MU current signal difference at the same measurement point is:
ΔIMU_D(n) = IMU_D_MAX(n) - IMU_D_MIN(n)
3) and calculating the total content of non-characteristic subharmonics of the direct current measuring device at each measuring point in the multi-measuring point based on the instantaneous sampling value of the MU current value.
The purpose of this calculation is to monitor the harmonic content of the dc transmission system.
For a direct current transmission system, the characteristic subharmonic on the direct current side is N × K, where N is the number of pulses of a rectifier bridge, and K is a natural number 1,2,3, … …. Certain content of characteristic subharmonics inevitably appears in direct current, and the content can fluctuate greatly in engineering practice, while the content of non-characteristic subharmonics is relatively much smaller and stable. Therefore, the total content of the non-characteristic subharmonics can represent whether the current measuring device has measurement abnormality or not.
In 2), the sequence i of MU instantaneous sample values has been sampledMU(n) DFT conversion is carried out, and the total content of the non-characteristic subharmonic of each measuring point is calculated on the basis of the DFT conversion. FIG. 5 is a schematic diagram illustrating the calculation of the total content of non-characteristic subharmonics at each measuring point in the error situation sensing method of the DC measuring device according to the present invention.
MU instantaneous sample value sequence iMUThe DFT result (n) includes a DC component IMU_DCharacteristic subharmonic component IMU_HxAnd a non-characteristic subharmonic component IMU_Hy. Wherein, the value of x is N x K, and the value of y is the harmonic frequency left after removing direct current and x. In an embodiment of the present invention, in a 12-pulse converter valve project, the harmonic frequencies obtained after DFT are sequentially 0, 1,2,3, … …, and 99. Wherein, 0 order corresponds to the direct current component, the characteristic subharmonic is 12, 24, 36, 48, 60, 72, 84 and 96 orders, and the non-characteristic subharmonic is 1 to 11, 13 to 23, 25 to 35, 37 to 47, 49 to 59, 61 to 71, 73 to 83 and 85 to 95 orders.
Then, the total content of the non-characteristic subharmonics is:
AMU_H = 
wherein, the harmonic frequency of the molecule in the formula is non-characteristic harmonic frequency.
And 5: and (4) carrying out error evaluation on the direct current measuring device according to the calculation result in the step (4), wherein the error evaluation specifically comprises the following steps:
step 5.1, according to the self dual AD difference degree delta i of the same remote modules(n), calculating the current error state evaluation result P1.
Firstly, the larger i of the double AD instantaneous sampling values is obtaineds_max：
is_max = MAX( |is_ad2(n)|，|is_ad1(n）| )
And calculating the ratio K1 of the current instantaneous sampling value:
K1 = is_max / Ir；
and Ir is the rated primary current value of the current direct current measuring device.
And selecting the values of the error coefficient K2 and the margin coefficient K3 according to the value of K1. The value taking method of K2 can be determined according to the requirement of the accuracy level of a current measuring device in GB/T26216.1-2019 DC current measuring device of a high-voltage DC power transmission system. The value of K3 is considered that the instantaneous sampling value is easily affected by noise and environmental interference, and has large fluctuation. In one embodiment of the present invention, the values of K1, K2, and K3 are shown in table 1.
K2 is a coefficient defined from the accuracy dimension. The standard GB26216.1 has placed accuracy requirements, i.e. maximum allowable error requirements, on dc current measuring devices. The accuracy requirement is defined in segments according to the magnitude of the current measured current, which is the basis for the determination of column 1, K1, and column 2, K2 of table 1.
K3 is a coefficient defined from the adaptability of a particular application scenario. Considering that the accuracy requirement in the standard GB26216.1 is proposed for a dc component within a certain time window (it can be understood that the dc component is extracted from all samples within a batch of samples, for example, 100 ms), while the application is here for an instantaneous sample, the instantaneous sample necessarily contains instantaneous errors introduced by various types of noise, and the proposed K3 is to avoid noise that is present in engineering and is allowable within a certain range, which is called a margin coefficient. The specific value of the coefficient essentially depends on expert experience and engineering application experience, and is a parameter which needs to be adjusted and optimized in application.
TABLE 1 value-taking tables for K1, K2 and K3
Calculating an evaluation reference value V according to the error coefficient K2 and the margin coefficient K3L1：
VL1 = is_max * (2 *K2 ) * K3
Here, the operation of multiplying K2 by 2 is performed in consideration of the requirement for error limitation to allow for both positive and negative values.
According to the evaluation reference value VL1And double degree of difference Δ i in ADs(n), calculating an evaluation result P1:
P1 = 100 –( Δis(n)/ VL1 )*100
the evaluation result P1 has the highest value of 100, and represents the optimal error state; the lower the value, the worse the representative error state; and when the value is 0 or negative, the error state is abnormal, and an alarm is required.
Step 5.2, according to the difference degree delta I of the multiple MU current signals at the same measuring pointMU_D(n), calculating the current error state evaluation result P2.
Firstly, the effective value I of the current signal of the measuring point is obtainedMU_D(n)：
IMU_D(n) = [ IMU1_D(n) + IMU2_D(n) + ……+ IMUT_D(n) ] / T
Wherein the measuring point has T sets of MU, IMU1_D(n)，IMU2_D(n)，……，IMUT_DAnd (n) are effective values of the output direct current respectively.
The ratio K4 of the current effective values is then calculated:
K4= IMU_D(n) / Ir
and Ir is the rated primary current value of the current direct current measuring device.
And taking values of the error coefficient K5 and the margin coefficient K6 according to the value of K4. The value of K5 is the same as the coefficient K2; the value of K6 is based on the stability of the effective value of the direct current component, and then the difference of hardware, the influence of asynchronous sampling, the error of the algorithm and the like are comprehensively considered. In one embodiment of the present invention, the values of K4, K5, and K6 are shown in table 2.
TABLE 2 value-taking tables for K4, K5 and K6
Calculating an evaluation reference value V according to the error coefficient K5 and the margin coefficient K6L2：
VL2 = IMU_D(n) *( 2* K5）* K6
Here, the operation of multiplying K5 by 2 is performed in consideration of the requirement for error limitation to allow for both positive and negative values.
According to the evaluation reference value VL2Degree of difference Δ I from current signalMU_D(n), calculating an evaluation result P2:
P2 = 100 –(ΔIMU_D(n)/ VL2 )*100
the evaluation result P2 has the highest value of 100, and represents the optimal error state; the lower the value, the worse the representative error state; and when the value is 0 or negative, the error state is abnormal, and an alarm is required.
If an alarm occurs, the effective value I of the direct current output by the T sets of MUs at the same measuring point is compared with the effective value I of the direct current output by the T sets of MUs at the same measuring pointMU1_D(n)，IMU2_D(n)……IMUT_D(n) are each independently of the mean value IMU_D(n) comparison:
ΔIMU1(n) = | IMU1_D(n) - IMU_D(n) |
ΔIMU2(n) = | IMU2_D(n) - IMU_D(n) |
……
then convert Delta IMU1(n)、ΔIMU2(n), … … are sorted by magnitude, the larger the magnitude, the greater the probability of error out-of-tolerance.
Step 5.3, according to the total content A of the non-characteristic subharmonic of each measuring pointMU_HThe current error state estimation result P3 is calculated.
First of all, the first step is to,threshold value V for determining total harmonic contentL3。
Threshold value V of total harmonic contentL3The determination is based on theory and engineering experience, wherein the theory refers to theoretical calculation according to professional simulation systems such as pscad and rtds, and the engineering experience refers to a statistical value obtained from operating data in the established engineering. The threshold is a parameter that needs to be optimized in the application. In one embodiment of the invention, threshold values V of different pointsL3The settings of (2) are shown in table 3.
TABLE 3 threshold values VL3Value-taking meter
Then, according to the threshold value VL3And total content of non-characteristic subharmonic AMU_HCalculating an evaluation result P3:
P3 = 100 –AMU_H *100 / VL3
the evaluation result P3 has the highest value of 100, and represents the optimal error state; the lower the value, the worse the representative error state; and when the value is 0 or negative, the error state is abnormal, and an alarm is required.
And 5.4, taking the lowest value of the current error state evaluation results P1, P2 and P3 obtained by calculation in the steps 5.1-5.3 as the final evaluation result Pn of the current error state of the direct current measuring device.
The calculation of step 5 is schematically shown in fig. 6.
Step 6: and (5) estimating the error of the direct current measuring device according to the error estimation calculation data in the step 5.
And 6, estimating the future error state of the direct current measuring device based on the estimation result of the current error state of the direct current measuring device.
And forming a history record according to the current error state evaluation result P1, P2 and P3 values calculated in the step 5. In one embodiment of the present invention, the current error state evaluation results P1, P2, and P3 values are averaged over 1 hour, with the average being stored every hour to form a history. The total duration of the history record can be the time of commissioning the error perception system, which is several days in short and years in many cases.
And then carrying out data extraction on the historical data points (p 1, p2 and p 3) for a period of time, wherein the historical data points are respectively and independently recorded, stored, extracted and calculated to obtain a data set P (n). In one embodiment of the present invention, the extraction is performed for the last 1 month, the last 1 year and all time since commissioning, respectively, and the formed data sets p (n) include the data sets pm (n) for the last 1 month, py (n) for the last 1 year and pa (n) for all time since commissioning, respectively. And if the total time length does not meet the requirement of a certain extraction time length, abandoning the extraction of the time length.
Using the extracted data set P (N) as a dependent variable array, and using the corresponding time array [1,2,3 … … N ]]As an array of arguments. Wherein, the time unit can be hour, and N is the number of elements of the data set p (N). And fitting the discrete data to the independent variable array and the dependent variable array. In one embodiment of the invention, the power function of the minimum absolute residue method is adopted for curve fitting to obtain a fitting functionf(x) = ax b + cWherein a, b and c are coefficients obtained by curve fitting and respectively represent amplitude, power and offset; xis an independent variable, i.e. time.
By fitting out a functionf(x)Time of an independent variablexIncreasing t to obtain corresponding function resultf(x+t)I.e. the predicted time pointxError state results t times later.
Preferably, the error state can be predicted from the data set of the last 1 month in the future from 1 day to 1 week; from the data set of the last 1 year, the error state of 1 week to 1 month in the future can be predicted; from the data set of recent years, error states of 1 month to 3 months in the future can be predicted. Based on the consideration of reliability and actual operation and maintenance work, the error state beyond 3 months is not generally predicted.
The method for sensing the error situation of the direct current measuring device is introduced above. In addition, the invention also discloses an error situation sensing system of the direct current measuring device.
As shown in fig. 7, the error monitoring system of the dc current measuring device of the present invention includes:
the analysis module is used for analyzing the structure of the direct current measuring device and the measuring point arrangement mode;
the index setting and strategy making module is used for setting error monitoring indexes in a hierarchical mode and making a monitoring strategy according to the analysis result of the analysis module;
the data acquisition module is used for acquiring the measurement data of the direct current measurement device at each measurement point;
the error monitoring and calculating module is used for carrying out error monitoring and calculation on the direct current measuring device according to a formulated monitoring strategy;
the error evaluation module is used for carrying out error evaluation on the direct current measuring device according to the calculation result of the error monitoring calculation module;
and the error estimation module is used for estimating the error of the direct current measuring device according to the error estimation calculation data of the error estimation module.
Compared with the prior art, the invention has the beneficial effects that:
the invention grasps the problem essence of the measuring device, and utilizes the calculation and processing of 3 core parameters of the self double AD difference degree of the same remote module, the multi-MU current signal difference degree of the same measuring point and the total content of non-characteristic subharmonic of each measuring point, thereby being easy to realize, avoiding synchronous processing and complex calculation algorithm, and being convenient for development and engineering popularization;
the method can not only find the undetected error abnormity in time, but also pre-judge the error abnormity which possibly occurs in the future, prevent the error abnormity in the future, and improve the reliability and the operation and maintenance level of the direct current measuring device;
the method can give out a final evaluation result, and give out a score', a full score of 100, and is visual and clear;
in the application process, parameters such as margin coefficients, threshold values and the like in the method can be adjusted by combining with feedback of actual operation and maintenance, and the reliability of error situation perception is gradually optimized;
the invention does not need to change the direct current measuring device, and only adds a set of equipment arranged in the screen cabinet in the control room, thereby having small construction amount.
The present applicant has described and illustrated embodiments of the present invention in detail with reference to the accompanying drawings, but it should be understood by those skilled in the art that the above embodiments are merely preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.
Claims (16)
1. A method for monitoring errors of a direct current measuring device is characterized by comprising the following steps:
the method comprises the following steps:
step 1: analyzing the structure of the direct current measuring device and the measuring point arrangement mode; each measuring point is provided with a direct current measuring device, each direct current measuring device comprises a remote end module and a plurality of MUs (multi-user units) connected with the remote end module, the remote end module adopts double AD (analog-to-digital) for sampling, and double AD sampling values of the remote end module are output through the MUs connected with the remote end module;
step 2: setting error monitoring indexes in a hierarchical manner and making a monitoring strategy according to the analysis result in the step 1; the error monitoring indexes comprise the self double AD sampling value difference degree, the multi-MU current signal difference degree and the total content of non-characteristic subharmonic of the remote module;
and step 3: acquiring the measurement data of the direct current measurement device at each measurement point;
and 4, step 4: carrying out error monitoring calculation on the direct current measuring device according to a formulated monitoring strategy; the error monitoring calculation includes: calculating self double AD difference degrees of the remote module based on the double AD sampling values; calculating the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point based on the instantaneous sampling value of the MU current value; calculating the total content of non-characteristic subharmonics of the direct current measuring device of each measuring point in the multi-measuring point based on the instantaneous sampling value of the MU current value;
and 5: performing error evaluation of the direct current measuring device according to the calculation result of the step 4; the error evaluation comprises the following steps: step 5.1: calculating a current error state evaluation result P1 according to the self double AD difference degree of the same remote module; step 5.2: calculating a current error state evaluation result P2 according to the difference degree of the multiple MU current signals at the same measuring point; step 5.3: calculating a current error state evaluation result P3 according to the total content of the non-characteristic subharmonic of each measuring point; step 5.4: taking the lowest value of P1, P2 and P3 as the final evaluation result Pn of the current error state of the direct current measuring device;
step 6: and (5) estimating the error of the direct current measuring device according to the error estimation calculation data in the step 5.
2. The method for monitoring the error of the direct current measuring device according to claim 1, wherein:
in the step 2, according to different monitoring ranges, the following error monitoring indexes are hierarchically set:
1) self dual AD difference of the remote module;
2) the current signal difference degree among multiple MUs of the direct current measuring device at the same measuring point;
3) the total content of non-characteristic subharmonic of a direct current measuring device of each measuring point in the multiple measuring points;
and (4) establishing a monitoring strategy according to the error monitoring index, and evaluating the current error state of the direct current measuring device.
3. The method for monitoring the error of the direct current measuring device according to claim 1, wherein:
and 3, acquiring double AD sampling values and MU current values of a remote module of the direct current measuring device at each measuring point.
4. The method for monitoring the error of the direct current measuring device according to claim 3, wherein:
and 3, after the double AD sampling values are obtained, calibrating the obtained sampling values at the current moment based on an internal unified clock of the direct current measuring device.
5. The method for monitoring the error of the direct current measuring device according to claim 1, wherein:
in step 4, it is assumed that the dual ADs of the remote modules are AD1 and AD2, respectively;
the instantaneous sample value at a certain moment of AD1 is is_ad1(n), the instantaneous sample value of AD2 at the same time is is_ad2(n), the dual AD disparity calculation method is:
Δis(n) = |is_ad2(n) - is_ad1(n）|
where n represents the sequence number of the discrete instantaneous sample value.
6. The method for monitoring the error of the direct current measuring device according to claim 5, wherein:
in step 4, the calculation formula of the instantaneous sampling value of the MU current value is as follows:
iMU(n) = [ is_ad2(n) + is_ad1(n）] / 2
wherein is_ad1(n) is the instantaneous sample value at a certain time of AD 1; i.e. is_ad2And (n) is an instantaneous sampling value of the AD2 at the same time.
7. The method for monitoring the error of the direct current measuring device according to claim 6, wherein:
in step 4, calculating the current signal difference degree between multiple MUs of the direct current measuring device at the same measuring point based on the instantaneous sampling value of the MU current value, specifically comprising:
taking a sampling value sequence of a time window, performing discrete Fourier transform, and solving an effective value of a direct current signal;
respectively calculating effective values of direct current signals of multiple MUs at the same measuring point, and sequencing the effective values according to amplitude values to obtain a maximum value IMU_D_MAX(n) and a minimum value IMU_D_MIN(n)；
Then, the current signal difference between the multiple MUs of the dc current measuring device at the same measuring point is:
ΔIMU_D(n) = IMU_D_MAX(n) - IMU_D_MIN(n)。
8. the method for monitoring the error of the direct current measuring device according to claim 7, wherein:
in step 4, calculating the total content of non-characteristic subharmonics of the direct current measuring device of each measuring point in the multiple measuring points based on the instantaneous sampling value of the MU current value, specifically:
the discrete Fourier transform of the sample value sequence of MU contains DC component IMU_DCharacteristic subharmonic component IMU_HxAnd a non-characteristic subharmonic component IMU_Hy；
Wherein, the value of x is N x K, N is the number of pulses of the rectifier bridge, and K is a natural number 1,2,3, … …; the value of y is the harmonic frequency left after removing direct current and x;
then, the total content of the non-characteristic subharmonics is:
AMU_H = 
wherein, the harmonic frequency of the molecule in the formula is non-characteristic harmonic frequency.
9. The method for monitoring the error of the direct current measuring device according to claim 1, wherein:
in step 5.1, the larger i of the double AD instantaneous sampling values is first obtaineds_max：
is_max = MAX( |is_ad2(n)|，|is_ad1(n）| )
Wherein is_ad1(n) is the instantaneous sample value at a certain time of AD 1; i.e. is_ad2(n) is the instantaneous sample value of AD2 at the same time;
and calculating the ratio K1 of the current instantaneous sampling value:
K1 = is_max / Ir
wherein Ir is the rated primary current value of the current direct current measuring device;
selecting values of an error coefficient K2 and a margin coefficient K3 according to the value of K1;
calculating an evaluation reference value V according to the error coefficient K2 and the margin coefficient K3L1：
VL1 = is_max * (2 *K2 ) * K3
According to the evaluation reference value VL1And double degree of difference Δ i in ADs(n), calculating an evaluation result P1:
P1 = 100 –( Δis(n)/ VL1 )*100。
10. the method for monitoring the error of the direct current measuring device according to claim 9, wherein:
in step 5.2, firstly, the effective value I of the current signal of the measuring point is obtainedMU_D(n)：
IMU_D(n) = [ IMU1_D(n) + IMU2_D(n) + ……+ IMUT_D(n) ] / T
Wherein the measuring point has T MU, IMU1_D(n)、IMU2_D(n)、……、IMUT_D(n) the effective value of the direct current output by each MU is respectively;
then, the ratio K4 of the current effective values is calculated:
K4= IMU_D(n) / Ir
wherein Ir is the rated primary current value of the current direct current measuring device;
taking values of an error coefficient K5 and a margin coefficient K6 according to the value of K4;
calculating an evaluation reference value V according to the error coefficient K5 and the margin coefficient K6L2：
VL2 = IMU_D(n) *( 2* K5）* K6
According to the evaluation reference value VL2Degree of difference Δ I from current signalMU_D(n), calculating an evaluation result P2:
P2 = 100 –(ΔIMU_D(n)/ VL2 )*100。
11. the method for monitoring the error of the direct current measuring device according to claim 10, wherein:
firstly, a threshold value V of the total harmonic content is determinedL3；
Then, according to the threshold value VL3And total content of non-characteristic subharmonic AMU_HCalculating an evaluation result P3:
P3 = 100 –AMU_H *100 / VL3。
12. the method for monitoring the error of the direct current measuring device according to claim 11, wherein:
the evaluation results P1, P2 and P3 have the highest value of 100, and represent the optimal error state; the lower the value, the worse the representative error state; and when the value is 0 or negative, the error state is abnormal, and an alarm is required.
13. The method for monitoring the error of the direct current measuring device according to claim 12, wherein:
in step 5.2, if an alarm occurs, the effective value I of the direct current output by the T sets of MUs at the same measuring point is judgedMU1_D(n)，IMU2_D(n)……IMUT_D(n) are respectively related to the effective value IMU_D(n) comparison to give Δ IMU1(n)、ΔIMU2(n)、……ΔIMUT(n) sorting according to the compared amplitudes, wherein the larger the amplitude is, the higher the possibility of error out-of-tolerance is.
14. The method for monitoring the error of the direct current measuring device according to claim 2, wherein:
the step 6 specifically comprises the following steps:
recording and storing the error state evaluation results P1, P2 and P3 to form a history record;
carrying out data extraction on data points of the historical records for a period of time to obtain a data set P (n);
using the extracted data set P (n) as a dependent variable array, and corresponding to the dependent variable arrayTime array [1,2,3 … … N]As an independent variable array, fitting discrete data to obtain a fitting functionf(x)Wherein, in the step (A),xis an independent variable, i.e. time;
by fitting out a functionf(x)Time of an independent variablexIncreasing t to obtain corresponding function resultf(x+t)I.e. the predicted time pointxError state results t times later.
15. The method for monitoring the error of the direct current measuring device according to claim 14, wherein:
step 6, extracting a data set of the latest 1 month, and predicting the error state from 1 day to 1 week in the future;
or extracting a data set of the last 1 year and predicting the error state of 1 week to 1 month in the future;
or extracting data sets of more than two years in the last time, and predicting the error state of 1 month to 3 months in the future.
16. A dc current measuring device error monitoring system that implements the dc current measuring device error monitoring method according to any one of claims 1 to 15, characterized in that: the system comprises:
the analysis module is used for analyzing the structure of the direct current measuring device and the measuring point arrangement mode;
the index setting and strategy making module is used for setting error monitoring indexes in a hierarchical mode and making a monitoring strategy according to the analysis result of the analysis module;
the data acquisition module is used for acquiring the measurement data of the direct current measurement device at each measurement point;
the error monitoring and calculating module is used for carrying out error monitoring and calculation on the direct current measuring device according to a formulated monitoring strategy;
the error evaluation module is used for carrying out error evaluation on the direct current measuring device according to the calculation result of the error monitoring calculation module;
and the error estimation module is used for estimating the error of the direct current measuring device according to the error estimation calculation data of the error estimation module.
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| CN103543431B (en) * | 2013-10-22 | 2017-01-18 | 江苏靖江互感器厂有限公司 | Method and system for measuring errors of electromagnetic type mutual inductor based on digital signal processing |
| CN109738695A (en) * | 2019-02-19 | 2019-05-10 | 扬州市职业大学(扬州市广播电视大学) | Based on data acquisition can automatic identification alternating current-direct current signal electric power measurement device |
| CN110456298A (en) * | 2019-07-19 | 2019-11-15 | 中国电力科学研究院有限公司 | A kind of adaptive alternately measuring device and the method for measurement direct-current voltage proportion magnitude error |
| CN113625216B (en) * | 2021-10-12 | 2022-03-11 | 国网江西省电力有限公司电力科学研究院 | Direct current transformer flying spot closed loop testing device and method |
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