CN112415457A - Method and system for realizing alternating current acquisition and calibration of electric power comprehensive tester - Google Patents
Method and system for realizing alternating current acquisition and calibration of electric power comprehensive tester Download PDFInfo
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Abstract
The invention discloses a method and a system for realizing AC acquisition and calibration of an electric power comprehensive tester, belonging to the technical field of electric power instruments and meters, comprising the following steps: acquiring an external voltage and current input signal, and preprocessing the external voltage and current input signal to obtain a small voltage signal which is used as an input signal of an AD sampling module; carrying out continuous cycle sampling on an input signal of the AD sampling module according to a set sampling frequency, and carrying out DFT calculation on a sampling point to obtain the amplitude and the phase angle of three-phase voltage and current; in the calibration mode, the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears are calculated to obtain a calibration coefficient in each gear; and calculating a current voltage and current acquisition actual value according to the calibration coefficient and the actual input value of the current gear, and automatically adjusting the gear. Compared with the traditional test instrument, the invention overcomes the defect that the acquisition precision cannot be improved in a wide range.
Description
Technical Field
The invention relates to the technical field of electric power instruments and meters, in particular to a method and a system for realizing alternating current acquisition and calibration of an electric power comprehensive tester.
Background
With the rapid development of the power industry, a smart grid is gradually applied to a power system to solve a plurality of problems of electric energy use. As a monitoring unit at the tail end of the intelligent power grid, the intelligent power meter is mainly used for collecting power basic information such as voltage, current, frequency, phase, power, electric energy and the like so as to improve the utilization rate of power resources. The extensive application of current large-scale integrated circuit for electric power instrument has developed from simple spare part to the integrated component type of collecting multiple functions in an organic whole, and the electric power industry has also given more functions to electric power instrument to its abundant functional requirement, and the requirement to electric power instrument collection precision is also higher and higher simultaneously.
Disclosure of Invention
The invention aims to overcome the defects in the background technology and overcome the defect that the acquisition precision cannot be improved in a wide range in the prior art.
In order to realize the purpose, the method for realizing the acquisition and calibration of the alternating current of the electric power comprehensive tester comprises the following steps:
acquiring an external voltage and current input signal, and preprocessing the external voltage and current input signal to obtain a small voltage signal which is used as an input signal of an AD sampling module;
carrying out continuous cycle sampling on an input signal of the AD sampling module according to a set sampling frequency, and carrying out DFT calculation on a sampling point to obtain the amplitude and the phase angle of three-phase voltage and current;
in the calibration mode, calculating the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears to obtain a calibration coefficient in each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
under the acquisition mode, calculating an actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value under the current gear;
and adjusting the input gear of the AD sampling module according to the actual acquisition value of the current voltage and current.
Further, the acquiring an external voltage and current input signal and preprocessing the external voltage and current input signal to obtain a small voltage signal as an input signal of the AD sampling module includes:
carrying out PT and CT transformation ratio processing on the external voltage and current input signal to obtain a small voltage and current signal;
processing the small voltage and current signals by using a divider resistor and a sampling resistor respectively to obtain processed voltage and current signals;
processing the processed voltage and current signals by using conditioning circuits and program-controlled amplifiers of different gears, and converting the processed voltage signals into small voltage signals in a corresponding interval range;
and taking the small voltage signal of the corresponding interval range as an input signal of the AD sampling module.
Further, the relationship between the conditioning circuits of different gears and the amplification factors of the programmable amplifier is as follows:
under the measuring range of 0V < U < 3V, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 3/101 multiplied by 200 and approximately equals to 6V;
under the measuring range of 3V < U < 30V, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 30/101 multiplied by 20 and approximately equals to 6V;
under the measuring range of 0V < U < 3V, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 450/101 multiplied by 2 and approximately equal to 9V;
under the measuring range of 0A < I < 1A, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 1/4000 multiplied by 120 multiplied by 200 and approximately equals to 6V;
under the measuring range that 1A < I is less than or equal to 10A, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 10/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V;
under the measuring range that I is less than or equal to 10A and less than or equal to 100A, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 100/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V.
Further, the continuous cycle sampling is performed on the input signal of the AD sampling module according to the set sampling frequency, and DFT calculation is performed on the sampling points to obtain the amplitude and the phase angle of the three-phase voltage and current, including:
carrying out continuous cycle sampling on the input signal of the AD sampling module according to the set sampling frequency and the number of sampling points per cycle;
fourier transform is carried out on the collected signals by each cycle, and the fundamental wave effective value and the phase angle of the voltage and current signals are calculated according to the result of the Fourier transform;
and averaging the effective values and the phase angles of the fundamental waves obtained by calculating the N cycles to obtain the amplitude and the phase angles of the three-phase voltage and current.
Further, in the calibration mode, the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears are calculated to obtain a calibration coefficient in each gear, the calibration coefficient includes an amplitude calibration coefficient and an angle calibration coefficient, and the standard values of the non-three-phase voltage and current include the standard values of three-phase voltage, current, active power and reactive power, including:
the calculation formula of the amplitude calibration coefficient of each acquisition channel is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under n gears, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yni is a standard addition value of the current acquisition channel;
and setting the angle of the acquisition channel Ua to be 0 degree all the time, setting the phase angle values of other acquisition channels to be included angles with the Ua, outputting a three-phase voltage standard value according to a fixed phase sequence in the calibration mode, and calculating the angle calibration coefficient of the voltage channel.
Further, the calculation process of the angle calibration coefficient of the voltage channel comprises the following steps:
KθnUa＝0，
KθUnb＝240-(XθnUb-XθnUa)，
KθUnc＝120-(XθnUc-XθnUa)，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of three channel angles of Ua, Ub and Uc under the n gear respectively, and X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels;
and then according to the active and reactive standard values, calculating an included angle between the voltage and the current:
Ang_Ia＝atan(Qa/Pa)，
Ang_Ib＝atan(Qb/Pb)，
Ang_Ic＝atan(Qc/Pc)，
KθnIa＝0-Ang_Ia-XθnIa+XθnUa，
KθnIb＝240-Ang_Ib-XθnIb+XθnUa，
KθnIc＝120-Ang_Ic-XθnIc+XθnUa，
wherein: k theta nIa, K theta nIb and K theta nIc are calibration coefficients of the angles of three channels Ia, Ib and Ic in the n gear, and X theta nIa, X theta nIb and X theta nIc are calculated values of the DFT angles of the current channels.
Further, in the acquisition mode, calculating an actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value in the current gear, including:
under the collection mode, calculating the amplitude and the phase angle of a voltage and current collection calculation value according to the calibration coefficient under the current gear, wherein:
yn i Kni × Xni (i 0,1,2 … stands for Ua, Ub, Uc, Ia, Ib, Ic, respectively),
wherein: kni is an amplitude calibration coefficient of the ith channel under the n-gear, Xni is a fundamental wave effective amplitude calculated by the current channel, and Yn i is a voltage or current acquisition calculation value of the current acquisition channel;
YθnUa＝0，
YθnUb＝XθnUb+KθUnb–XθnUa-KθUna，
YθnUc＝XθnUc+KθUnc–XθnUa-KθUna，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of angles of three channels of Ua, Ub and Uc under the n gear, X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels, and Y theta nUa, Y theta nUb and Y theta nUc are calculated values of voltage or current angles of current acquisition channels.
On the other hand, adopt an electric power integrated tester alternating current volume collection and calibration implementation system, include: preprocessing module, AD sampling module and core control module, wherein:
the preprocessing module is used for acquiring an external voltage and current input signal, preprocessing the external voltage and current input signal, acquiring a small voltage signal and using the small voltage signal as an input signal of the AD sampling module;
the core control module carries out continuous cycle sampling on the input signal of the AD sampling module according to a set sampling frequency, and carries out DFT calculation on a sampling point to obtain the amplitude and the phase angle of the three-phase voltage and current;
the core control module calculates the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears in a calibration mode to obtain a calibration coefficient in each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
and the core control module calculates the actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value under the current gear in the acquisition mode, and adjusts the input gear of the AD sampling module according to the actual acquisition value of the current voltage and current.
Further, the preprocessing module comprises a voltage transformer, a current transformer, a divider resistor, a sampling resistor, a conditioning circuit and a programmable amplifier, wherein:
the voltage transformer and the current transformer respectively carry out PT and CT transformation ratio processing on the external voltage and current input signals to obtain small voltage and current signals;
the voltage dividing resistor and the sampling resistor respectively process the small voltage and current signals to obtain processed voltage and current signals;
and the conditioning circuits and the program-controlled amplifiers in different gears process the processed voltage and current signals, and convert the processed voltage signals into small voltage signals in corresponding interval ranges to be used as input signals of the AD sampling module.
Further, the core control module comprises a calibration coefficient calculation module comprising an amplitude calibration coefficient calculation unit and an angle calibration coefficient calculation unit, wherein:
the amplitude calibration coefficient calculation unit is used for calculating an amplitude calibration coefficient of each acquisition channel, and the calculation formula is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under n gears, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yni is a standard addition value of the current acquisition channel;
the angle calibration coefficient calculation unit is used for setting the angle of the acquisition channel Ua to be 0 degree all the time, the phase angle values of other acquisition channels are included angles with the Ua, and under the calibration mode, the three-phase voltage standard values are output in a fixed phase sequence to calculate the angle calibration coefficient of the voltage channel.
Compared with the prior art, the invention has the following technical effects: according to the invention, the program-controlled amplifier is automatically switched to different gears according to the range of the voltage and current input value, the sampling precision of AD is ensured, the acquisition precision is further improved by calibrating the amplitude and the phase angle under different gears, and the acquisition precision can also be improved even under a wide range.
Drawings
The following detailed description of embodiments of the invention refers to the accompanying drawings in which:
FIG. 1 is a flow chart of a method for implementing AC acquisition and calibration of an integrated power tester;
fig. 2 is a structural diagram of an ac acquisition and calibration implementation system of an integrated power tester.
Detailed Description
To further illustrate the features of the present invention, refer to the following detailed description of the invention and the accompanying drawings. The drawings are for reference and illustration purposes only and are not intended to limit the scope of the present disclosure.
As shown in fig. 1, the embodiment discloses a method for acquiring and calibrating alternating current of an electric power comprehensive tester, which includes the following steps:
s1, acquiring an external voltage and current input signal, and preprocessing the external voltage and current input signal to obtain a small voltage signal which is used as an input signal of the AD sampling module;
s2, carrying out continuous cycle sampling on the input signal of the AD sampling module according to the set sampling frequency, and carrying out DFT calculation on the sampling point to obtain the amplitude and phase angle of the three-phase voltage and current;
s3, in a calibration mode, calculating the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears to obtain a calibration coefficient in each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
s4, calculating the actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value in the current gear in the acquisition mode;
and S5, adjusting the input gear of the AD sampling module according to the actual acquisition value of the current voltage and current.
It should be noted that, in the normal acquisition mode, the present embodiment obtains the actual value of the voltage and the current acquired in real time according to the calculated calibration coefficient, and switches the amplification coefficient of the corresponding gear according to gear division, so that the input voltage of the AD sampling is in the full-scale range as much as possible, thereby ensuring the sampling accuracy.
More preferably, in step S1: acquiring an external voltage and current input signal, preprocessing the external voltage and current input signal to obtain a small voltage signal, and using the small voltage signal as an input signal of an AD sampling module, wherein the method comprises the following subdivision steps of S11 to S14:
s11, carrying out PT and CT transformation ratio processing on the external voltage and current input signal to obtain a small voltage and current signal;
in addition, the present embodiment adopts high precision PT and CT with precision reaching 0.01 level, and the transformation ratio of the external input voltage current signal is a small voltage current signal after the high precision PT and CT.
S12, processing the small voltage and current signals by using a divider resistor and a sampling resistor respectively to obtain processed voltage and current signals;
s13, processing the processed voltage and current signals by using the conditioning circuits and the program control amplifiers of different gears, and converting the processed voltage signals into small voltage signals in a corresponding interval range;
and S14, taking the small voltage signal of the corresponding interval range as the input signal of the AD sampling module.
As a further preferable scheme, the voltage input range of the AD sampling module is-10 to 10V, and the corresponding relationship between the amplification factors of the conditioning circuits at different gears and the programmable amplifier is as follows:
the voltage acquisition range is 0-450V, the PT resistor voltage division ratio is 100:1, and the sampling resistors adopt 3 200K serial connections and 6K voltage division:
under the measuring range of 0V < U < 3V, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 3/101 multiplied by 200 and approximately equals to 6V;
under the measuring range of 3V < U < 30V, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 30/101 multiplied by 20 and approximately equals to 6V;
under the measuring range of 0V < U < 3V, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 450/101 x 2 and approximately equals to 9V;
the current collection range is 0-100A, the number of turns of the CT coil is 4000T, and the sampling resistance is 120 omega:
under the measuring range of 0A < I < 1A, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 1/4000 multiplied by 120 multiplied by 200 and approximately equals to 6V;
under the measuring range that 1A < I is less than or equal to 10A, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 10/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V;
under the measuring range that I is less than or equal to 10A and less than or equal to 100A, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 100/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V.
More preferably, in step S2: the method comprises the following steps of carrying out continuous cycle sampling on an input signal of an AD sampling module according to a set sampling frequency, carrying out DFT calculation on sampling points to obtain the amplitude and the phase angle of three-phase voltage and current, and subdividing steps S21 to S23:
s21, carrying out continuous cycle sampling on the input signal of the AD sampling module according to the set sampling frequency and the sampling point number of each cycle;
s22, carrying out Fourier transform on the collected signals by each cycle, and calculating the fundamental wave effective value and the phase angle of the voltage and current signals according to the result of the Fourier transform;
s23, averaging the effective values and the phase angles of the fundamental waves obtained by calculating the N cycles to obtain the amplitude and the phase angles of the three-phase voltage current.
It should be noted that, in this embodiment, the device collects external voltage and current signals in real time at a sampling frequency of 50HZ and a sampling point number of 1024 per cycle, performs discrete fourier transform DFT computation on the collected signals once per cycle, obtains a fundamental effective value and a phase angle of the voltage and current signals according to a result of the discrete fourier transform DFT, and then averages the computed values of N cycles to obtain an amplitude and a phase angle of the voltage and current.
More preferably, in step S3: under the calibration mode, calculate three-phase voltage and current's amplitude and phase angle and the standard value of three-phase voltage and current under the different gears, obtain the calibration coefficient under every gear, this calibration coefficient includes amplitude calibration coefficient and angle calibration coefficient, and wherein, three-phase voltage and current's standard value includes three-phase voltage, electric current, active and idle standard value, includes:
the calculation formula of the amplitude calibration coefficient of each acquisition channel is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under the n gear, Xni is a fundamental wave effective amplitude value calculated by the current channel, Yni is a standard applied value of the current acquisition channel and is issued by an upper computer;
and setting the angle of the acquisition channel Ua to be 0 degree all the time, setting the phase angle values of other acquisition channels to be included angles with the Ua, outputting a three-phase voltage standard value according to a fixed phase sequence in the calibration mode, and calculating the angle calibration coefficient of the voltage channel.
Specifically, due to crystal oscillator errors and timer errors, the absolute angle calculated by DFT after each cycle sampling of each channel is changed, but the relative angle difference of each channel is not changed, so that the angle of the channel Ua is always set to be 0 degree, and the phase angle values of other channels are the included angles with Ua. During calibration, three-phase voltages are applied and output in a fixed phase sequence (0 degrees, 240 degrees and 120 degrees), and the angle calibration coefficients of the voltage channels are obtained as follows:
KθnUa＝0，
KθUnb＝240-(XθnUb-XθnUa)，
KθUnc＝120-(XθnUc-XθnUa)，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of three channel angles of Ua, Ub and Uc under the n gear respectively, and X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels;
and then according to the active and reactive standard values, calculating an included angle between the voltage and the current:
Ang_Ia＝atan(Qa/Pa)，
Ang_Ib＝atan(Qb/Pb)，
Ang_Ic＝atan(Qc/Pc)，
KθnIa＝0-Ang_Ia-XθnIa+XθnUa，
KθnIb＝240-Ang_Ib-XθnIb+XθnUa，
KθnIc＝120-Ang_Ic-XθnIc+XθnUa，
wherein: k theta nIa, K theta nIb and K theta nIc are calibration coefficients of the angles of three channels Ia, Ib and Ic in the n gear, and X theta nIa, X theta nIb and X theta nIc are calculated values of the DFT angles of the current channels.
More preferably, in step S4: under the collection mode, according to calibration coefficient and actual input value under the present gear, calculate the actual collection value of present voltage electric current, include:
under the collection mode, calculating the amplitude and the phase angle of a voltage and current collection calculation value according to the calibration coefficient under the current gear, wherein:
yn i Kni × Xni (i 0,1,2 … stands for Ua, Ub, Uc, Ia, Ib, Ic, respectively),
wherein: kni is an amplitude calibration coefficient of the ith channel under the n-gear, Xni is a fundamental wave effective amplitude calculated by the current channel, and Yn i is a voltage or current acquisition calculation value of the current acquisition channel;
YθnUa＝0，
YθnUb＝XθnUb+KθUnb–XθnUa-KθUna，
YθnUc＝XθnUc+KθUnc–XθnUa-KθUna，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of angles of three channels of Ua, Ub and Uc under the n gear, X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels, and Y theta nUa, Y theta nUb and Y theta nUc are calculated values of voltage or current angles of current acquisition channels.
More preferably, in step S5: the input gear of the AD sampling module is adjusted according to the actual collection value of the current voltage and current, and the method comprises the following steps:
under a normal acquisition mode, the actual value of the voltage and the current acquired in real time is obtained according to the calculated calibration coefficient, and the program control amplifier is switched to the amplification coefficient of the corresponding gear according to gear division, so that the input voltage of AD sampling is in a full-scale range as much as possible, and the sampling precision is ensured.
As shown in fig. 2, the present embodiment discloses an ac acquisition and calibration implementation system for an integrated power tester, including: preprocessing module 10, AD sampling module 20 and core control module 30, wherein:
the preprocessing module 10 is configured to obtain an external voltage and current input signal, and preprocess the external voltage and current input signal to obtain a small voltage signal, which is used as an input signal of the AD sampling module;
the core control module 30 performs continuous cycle sampling on the input signal of the AD sampling module according to a set sampling frequency, and performs DFT calculation on a sampling point to obtain the amplitude and phase angle of the three-phase voltage and current;
the core control module 30 calculates the amplitude and phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current at different gears in the calibration mode to obtain a calibration coefficient at each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
in the acquisition mode, the core control module 30 calculates an actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value in the current gear, and adjusts the input gear of the AD sampling module 20 according to the actual acquisition value of the current voltage and current.
As a further preferred scheme, the preprocessing module 10 includes a voltage transformer, a current transformer, a voltage dividing resistor, a sampling resistor, a conditioning circuit, and a programmable amplifier, wherein:
the voltage transformer and the current transformer respectively carry out PT and CT transformation ratio processing on the external voltage and current input signals to obtain small voltage and current signals;
the voltage dividing resistor and the sampling resistor respectively process the small voltage and current signals to obtain processed voltage and current signals;
the conditioning circuits and the programmable amplifiers in different gears process the processed voltage and current signals, and convert the processed voltage signals into small voltage signals in corresponding interval ranges, which are used as input signals of the AD sampling module 20.
The corresponding relationship of the conditioning circuits of different gears and the amplification factors of the program control amplifier is as follows:
under the measuring range of 0V < U < 3V, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 3/101 multiplied by 200 and approximately equals to 6V;
under the measuring range of 3V < U < 30V, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 30/101 multiplied by 20 and approximately equals to 6V;
under the measuring range of 0V < U < 3V, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 450/101 multiplied by 2 and approximately equal to 9V;
under the measuring range of 0A < I < 1A, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 1/4000 multiplied by 120 multiplied by 200 and approximately equals to 6V;
under the measuring range that 1A < I is less than or equal to 10A, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 10/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V;
under the measuring range that I is less than or equal to 10A and less than or equal to 100A, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 100/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V.
As a further preferable scheme, the core control module 30 includes a calibration coefficient calculation module, which includes an amplitude calibration coefficient calculation unit and an angle calibration coefficient calculation unit, wherein:
the amplitude calibration coefficient calculation unit is used for calculating an amplitude calibration coefficient of each acquisition channel, and the calculation formula is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under n gears, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yni is a standard addition value of the current acquisition channel;
the angle calibration coefficient calculation unit is used for setting the angle of the acquisition channel Ua to be 0 degree all the time, the phase angle values of other acquisition channels are included angles with the Ua, and under the calibration mode, the three-phase voltage standard values are output in a fixed phase sequence to calculate the angle calibration coefficient of the voltage channel.
As a further preferred scheme, the angle calibration coefficient calculating unit is specifically configured to:
KθnUa＝0，
KθUnb＝240-(XθnUb-XθnUa)，
KθUnc＝120-(XθnUc-XθnUa)，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of three channel angles of Ua, Ub and Uc under the n gear respectively, and X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels;
and then according to the active and reactive standard values, calculating an included angle between the voltage and the current:
Ang_Ia＝atan(Qa/Pa)，
Ang_Ib＝atan(Qb/Pb)，
Ang_Ic＝atan(Qc/Pc)，
KθnIa＝0-Ang_Ia-XθnIa+XθnUa，
KθnIb＝240-Ang_Ib-XθnIb+XθnUa，
KθnIc＝120-Ang_Ic-XθnIc+XθnUa，
wherein: k theta nIa, K theta nIb and K theta nIc are calibration coefficients of the angles of three channels Ia, Ib and Ic in the n gear, and X theta nIa, X theta nIb and X theta nIc are calculated values of the DFT angles of the current channels.
As a further preferred scheme, the core control module 30 is specifically configured to calculate, in the acquisition mode, an amplitude and a phase angle of the voltage and current acquisition calculation value according to the calibration coefficient in the current gear, where:
yn i Kni × Xni (i 0,1,2 … stands for Ua, Ub, Uc, Ia, Ib, Ic, respectively),
wherein: kni is a calibration coefficient of the ith channel under the n-gear, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yn i is a voltage or current acquisition calculation value of the current acquisition channel;
YθnUa＝0，
YθnUb＝XθnUb+KθUnb–XθnUa-KθUna，
YθnUc＝XθnUc+KθUnc–XθnUa-KθUna，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of angles of three channels of Ua, Ub and Uc under the n gear, X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels, and Y theta nUa, Y theta nUb and Y theta nUc are calculated values of voltage or current angles of current acquisition channels.
It should be noted that, after the acquisition value is calculated by the above formula, the core control module 30 automatically switches the AD input gear according to the size of the acquisition value. For example, at the current gear with the amplification factor of 2 times, the acquired and calculated voltage is 20V, and according to the division condition of the gear, the amplification factor of the programmable control amplifier is controlled to be switched from 2 times to 20 times of gear, so that the sampling precision of the AD is ensured.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for realizing the collection and calibration of the alternating current of an electric power comprehensive tester is characterized by comprising the following steps:
acquiring an external voltage and current input signal, and preprocessing the external voltage and current input signal to obtain a small voltage signal which is used as an input signal of an AD sampling module;
carrying out continuous cycle sampling on an input signal of the AD sampling module according to a set sampling frequency, and carrying out DFT calculation on a sampling point to obtain the amplitude and the phase angle of three-phase voltage and current;
in the calibration mode, calculating the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears to obtain a calibration coefficient in each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
under the acquisition mode, calculating an actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value under the current gear;
and adjusting the input gear of the AD sampling module according to the actual acquisition value of the current voltage and current.
2. The method for realizing the alternating current collection and calibration of the electric power comprehensive tester as claimed in claim 1, wherein the step of obtaining the external voltage and current input signal and preprocessing the external voltage and current input signal to obtain a small voltage signal as the input signal of the AD sampling module comprises the steps of:
carrying out PT and CT transformation ratio processing on the external voltage and current input signal to obtain a small voltage and current signal;
processing the small voltage and current signals by using a divider resistor and a sampling resistor respectively to obtain processed voltage and current signals;
processing the processed voltage and current signals by using conditioning circuits and program-controlled amplifiers of different gears, and converting the processed voltage signals into small voltage signals in a corresponding interval range;
and taking the small voltage signal of the corresponding interval range as an input signal of the AD sampling module.
3. The method for realizing the alternating current collection and calibration of the power comprehensive tester as claimed in claim 2, wherein the corresponding relationship of the amplification factors of the conditioning circuits and the programmable amplifiers in different gears is as follows:
under the measuring range of 0V < U < 3V, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 3/101 multiplied by 200 and approximately equals to 6V;
under the measuring range of 3V < U < 30V, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 30/101 multiplied by 20 and approximately equals to 6V;
under the measuring range of 0V < U < 3V, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 450/101 multiplied by 2 and approximately equal to 9V;
under the measuring range of 0A < I < 1A, sampling is carried out by 200 times, and the upper limit value of the AD input voltage is 1/4000 multiplied by 120 multiplied by 200 and approximately equals to 6V;
under the measuring range that 1A < I is less than or equal to 10A, 20 times of sampling is adopted, and the upper limit value of the AD input voltage is 10/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V;
under the measuring range that I is less than or equal to 10A and less than or equal to 100A, 2 times of sampling is adopted, and the upper limit value of the AD input voltage is 100/4000 multiplied by 120 multiplied by 20 and approximately equals to 6V.
4. The method for realizing the alternating current collection and calibration of the electric power comprehensive tester as claimed in claim 1, wherein the step of performing continuous cycle sampling on the input signal of the AD sampling module according to the set sampling frequency and performing DFT calculation on the sampling points to obtain the amplitude and the phase angle of the three-phase voltage and current comprises the steps of:
carrying out continuous cycle sampling on the input signal of the AD sampling module according to the set sampling frequency and the number of sampling points per cycle;
fourier transform is carried out on the collected signals by each cycle, and the fundamental wave effective value and the phase angle of the voltage and current signals are calculated according to the result of the Fourier transform;
and averaging the effective values and the phase angles of the fundamental waves obtained by calculating the N cycles to obtain the amplitude and the phase angles of the three-phase voltage and current.
5. The method for realizing the collection and calibration of the alternating current of the electric power comprehensive tester as claimed in claim 1, wherein in the calibration mode, the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears are calculated to obtain the calibration coefficient in each gear, the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient, and the standard values of the three-phase voltage and current comprise the standard values of the three-phase voltage, current, active power and reactive power, and the method comprises the following steps:
the calculation formula of the amplitude calibration coefficient of each acquisition channel is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under n gears, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yni is a standard addition value of the current acquisition channel;
and setting the angle of the acquisition channel Ua to be 0 degree all the time, setting the phase angle values of other acquisition channels to be included angles with the Ua, outputting a three-phase voltage standard value according to a fixed phase sequence in the calibration mode, and calculating the angle calibration coefficient of the voltage channel.
6. The method for realizing the alternating current collection and calibration of the power comprehensive tester as claimed in claim 5, wherein the calculation process of the angle calibration coefficient of the voltage channel comprises the following steps:
KθnUa＝0，
KθUnb＝240-(XθnUb-XθnUa)，
KθUnc＝120-(XθnUc-XθnUa)，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of three channel angles of Ua, Ub and Uc under the n gear respectively, and X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels;
and then according to the active and reactive standard values, calculating an included angle between the voltage and the current:
Ang_Ia＝atan(Qa/Pa)，
Ang_Ib＝atan(Qb/Pb)，
Ang_Ic＝atan(Qc/Pc)，
KθnIa＝0-Ang_Ia-XθnIa+XθnUa，
KθnIb＝240-Ang_Ib-XθnIb+XθnUa，
KθnIc＝120-Ang_Ic-XθnIc+XθnUa，
wherein: k theta nIa, K theta nIb and K theta nIc are calibration coefficients of the angles of three channels Ia, Ib and Ic in the n gear, and X theta nIa, X theta nIb and X theta nIc are calculated values of the DFT angles of the current channels.
7. The method for realizing the collection and calibration of the alternating current of the power integration tester as claimed in claim 1, wherein in the collection mode, calculating the actual collection value of the current voltage and current according to the calibration coefficient and the actual input value in the current gear comprises:
under the collection mode, calculating the amplitude and the phase angle of a voltage and current collection calculation value according to the calibration coefficient under the current gear, wherein:
yn i Kni × Xni (i 0,1,2 … stands for Ua, Ub, Uc, Ia, Ib, Ic, respectively),
wherein: kni is a calibration coefficient of the ith channel under the n-gear, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yn i is a voltage or current acquisition calculation value of the current acquisition channel;
YθnUa＝0，
YθnUb＝XθnUb+KθUnb–XθnUa-KθUna，
YθnUc＝XθnUc+KθUnc–XθnUa-KθUna，
wherein: k theta nUa, K theta nUb and K theta nUc are calibration coefficients of angles of three channels of Ua, Ub and Uc under the n gear, X theta nUa, X theta nUb and X theta nUc are calculated values of DFT angles of current channels, and Y theta nUa, Y theta nUb and Y theta nUc are calculated values of voltage or current angles of current acquisition channels.
8. The utility model provides a system is realized in collection of electric power integrated tester alternating current volume and calibration which characterized in that includes: preprocessing module, AD sampling module and core control module, wherein:
the preprocessing module is used for acquiring an external voltage and current input signal, preprocessing the external voltage and current input signal, acquiring a small voltage signal and using the small voltage signal as an input signal of the AD sampling module;
the core control module carries out continuous cycle sampling on the input signal of the AD sampling module according to a set sampling frequency, and carries out DFT calculation on a sampling point to obtain the amplitude and the phase angle of the three-phase voltage and current;
the core control module calculates the amplitude and the phase angle of the three-phase voltage and current and the standard values of the three-phase voltage and current in different gears in a calibration mode to obtain a calibration coefficient in each gear, wherein the calibration coefficient comprises an amplitude calibration coefficient and an angle calibration coefficient;
and the core control module calculates the actual acquisition value of the current voltage and current according to the calibration coefficient and the actual input value under the current gear in the acquisition mode, and adjusts the input gear of the AD sampling module according to the actual acquisition value of the current voltage and current.
9. The system of claim 8, wherein the pre-processing module comprises a voltage transformer, a current transformer, a voltage divider resistor, a sampling resistor, a conditioning circuit, and a programmable amplifier, wherein:
the voltage transformer and the current transformer respectively carry out PT and CT transformation ratio processing on the external voltage and current input signals to obtain small voltage and current signals;
the voltage dividing resistor and the sampling resistor respectively process the small voltage and current signals to obtain processed voltage and current signals;
and the conditioning circuits and the program-controlled amplifiers in different gears process the processed voltage and current signals, and convert the processed voltage signals into small voltage signals in corresponding interval ranges to be used as input signals of the AD sampling module.
10. The ac collection and calibration implementation system of an electrical power integration tester of claim 8, wherein the core control module comprises a calibration coefficient calculation module comprising an amplitude calibration coefficient calculation unit and an angle calibration coefficient calculation unit, wherein:
the amplitude calibration coefficient calculation unit is used for calculating an amplitude calibration coefficient of each acquisition channel, and the calculation formula is as follows:
kni Yni/Xni (i 0,1,2 … for Ua, Ub, Uc, Ia, Ib, Ic, respectively)
Wherein: kni is a calibration coefficient of the ith channel under n gears, Xni is a fundamental wave effective amplitude value calculated by the current channel, and Yni is a standard addition value of the current acquisition channel;
the angle calibration coefficient calculation unit is used for setting the angle of the acquisition channel Ua to be 0 degree all the time, the phase angle values of other acquisition channels are included angles with the Ua, and under the calibration mode, the three-phase voltage standard values are output in a fixed phase sequence to calculate the angle calibration coefficient of the voltage channel.
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