CN114814704A - Error compensation method for standard voltage transformer - Google Patents

Abstract

The invention provides an error compensation method for a standard voltage transformer in the technical field of standard voltage transformers, which comprises the following steps: step S10, storing the error value into an error table; step S20, separating an in-phase component signal and a quadrature component signal from the input voltage through a phase shift circuit; step S30, inputting current into a dual-channel AD signal acquisition module; s40, the single chip microcomputer obtains a voltage value and a current value through a dual-channel AD signal acquisition module, and further obtains an error coefficient to generate a digital control quantity of a digital-to-analog conversion chip; step S50, the addition circuit synthesizes the in-phase component and the quadrature component of the error signal into an error voltage signal; and step S60, outputting the error voltage signal through a second double-stage isolation voltage transformer to generate a floating ground error compensation signal. The invention has the advantages that: the floating signal corresponding to the voltage transformer error can be generated according to the voltage transformer error, the floating signal can be used for compensating the output of the voltage transformer, and the accuracy grade of the voltage transformer is greatly improved.

Description

A Standard Voltage Transformer Error Compensation Method

technical field

The invention relates to the technical field of standard voltage transformers, in particular to an error compensation method for standard voltage transformers.

Background technique

A voltage transformer is similar to a transformer and is used to transform the voltage on the line. But the purpose of the transformer to transform the voltage is to transmit electrical energy, and the purpose of the voltage transformer to transform the voltage is to measure the voltage of the line.

Because the electromagnetic voltage transformer has excitation current, and the primary winding has resistance and leakage reactance, the excitation current produces a voltage drop on the impedance, which inevitably leads to no-load error in the voltage transformer; and because when the secondary winding has a no-load error When a load is connected, a load current is generated in the secondary winding. In order to keep the magnetic flux unchanged, a load current component will also be added to the primary winding, and since the secondary winding also has resistance and leakage reactance, the load current is the same as , A voltage drop is generated on the internal impedance of the secondary winding, thus forming the load error of the voltage transformer.

Voltage transformer error, also known as voltage transformer proportional error, includes ratio difference and phase difference, of which the ratio difference is also called ratio difference, which is caused by the fact that the actual voltage ratio is not equal to the rated voltage ratio, generally used as a percentage (%) The phase difference, also known as the angular difference, refers to the phase difference between the primary voltage and the secondary voltage phasor, generally expressed in minutes (') or centi arcs (crad). The error of the voltage transformer can be represented by a complex number ε=f+jδ, where f is called the ratio difference, and δ is called the angular difference.

Due to the nonlinear excitation current of the iron core of the electromagnetic voltage transformer, the error of a single-stage voltage transformer above 10kV is usually difficult to break through 0.01 to 0.02. Traditionally, the two-stage structural compensation method can be used to further reduce the non-linearity of the voltage transformer. Linearity error, but in transformers with high voltage levels, insulation, shielding structures, etc. all bring challenges. Moreover, for the transformer of the same voltage level, the volume and weight will inevitably increase, and the economic cost will be increased at the same time.

Therefore, if a standard voltage transformer error compensation method can be provided to effectively improve the accuracy level of the voltage transformer without changing the original voltage transformer structure, it will greatly satisfy the user's requirements for standard voltage transformers. accuracy requirements.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a standard voltage transformer error compensation method, so as to improve the accuracy level of the voltage transformer.

The invention provides a standard voltage transformer error compensation method, comprising the following steps:

Step S10, input the error value of the standard voltage transformer under different working voltages and different load currents to the single-chip microcomputer through the RS232 interface or the display screen, and the single-chip computer stores the received error value in the error table in the storage module;

Step S20, after the input voltage passes through the first two-stage isolation voltage transformer and the filter amplifying circuit, it is input to the two-channel AD signal acquisition module, and at the same time, the in-phase component signal and the quadrature component signal are separated by the phase-shift circuit as the in-phase component of the error signal. reference reference signals for the component and quadrature components;

Step S30, the input current is input to the dual-channel AD signal acquisition module after passing through the sampling resistor and the filter circuit;

Step S40, the single-chip microcomputer obtains the voltage value and the current value through the dual-channel AD signal acquisition module, obtains the error coefficient based on the voltage value and the current value, and generates the digital control quantities of the first digital-to-analog conversion chip and the second digital-to-analog conversion chip, Used to control the magnitude of the in-phase component and the quadrature component of the error signal;

Step S50, the summing circuit synthesizes the in-phase component of the error signal output by the first digital-to-analog conversion chip and the quadrature component of the error signal output by the second digital-to-analog conversion chip into an error voltage signal;

Step S60: After the error voltage signal output by the adding circuit is output by the filter circuit, the amplifier circuit and the second two-stage isolation voltage transformer, a floating error compensation signal corresponding to the input voltage and input current is generated.

Further, in the step S40, the error coefficient includes an amplitude coefficient and a phase coefficient.

Further, in the step S40, the obtaining of the error coefficient based on the voltage value and the current value is specifically:

The voltage value and the current value are respectively compared with a preset error table in the storage module, and a corresponding error value is searched based on the error table.

Further, in the step S40, the obtaining of the error coefficient based on the voltage value and the current value is specifically:

Input the voltage value and the current value into a preset error function analytical formula to calculate the error value.

Further, in the step S40, the obtaining of the error coefficient based on the voltage value and the current value is specifically:

After inputting the voltage value and the current value into the preset excitation current function analytical formula to calculate the error analytical formula, the corresponding error value is obtained.

The advantages of the present invention are:

Since the error curve of each standard voltage transformer when it leaves the factory is a basically determined parameter, and it is relatively stable, the error value is mainly related to the current working voltage and load current. Therefore, by setting the storage module to store the error table of the standard voltage transformer or the analytical formula of the error function, the single-chip microcomputer separately collects the secondary voltage signal of the voltage transformer in the voltage input channel and the load current signal of the voltage transformer in the current input channel in real time. The corresponding error coefficient can be obtained from the current working voltage and load current. Based on the error coefficient, the corresponding voltage transformer error signal is generated, and the corresponding floating error compensation voltage signal is output through the error voltage signal isolation module. The error value generates the corresponding voltage transformer error floating signal to compensate the output of the voltage transformer, which greatly improves the accuracy level of the voltage transformer without changing the original structure of the voltage transformer.

Description of drawings

The present invention will be further described below with reference to the accompanying drawings and embodiments.

FIG. 1 is a circuit principle block diagram of a standard voltage transformer error compensation device of the present invention.

FIG. 2 is a schematic circuit diagram of a standard voltage transformer error compensation device of the present invention.

FIG. 3 is a flow chart of a standard voltage transformer error compensation method of the present invention.

FIG. 4 is a schematic flowchart of the present invention for storing error coefficients.

FIG. 5 is a schematic flow chart of reading the error coefficient according to the present invention.

FIG. 6 is a schematic diagram of the wiring of the present invention in a use state.

Tag Description:

100-a standard voltage transformer error compensation device, 1-voltage input channel, 2-current input channel, 3-MCU control module, 4-phase shift circuit, 5-first digital-to-analog conversion chip, 6-second digital Analog conversion chip, 7-adding circuit, 8-error voltage signal isolation module, 9-display screen, 10-power supply module, 11-first dual-stage isolation voltage transformer, 12-filter amplifier circuit, 21-sampling resistor, 22 -The first filter circuit, 31-MCU, 32-Dual channel AD signal acquisition module, 33-Storage module, 34-RS232 interface, 81-The second filter circuit, 82-Amplification circuit, 83-The second two-stage isolation voltage mutual inductance device.

Detailed ways

The general idea of the technical solutions in the embodiments of the present application is as follows: the storage module 33 is set to store the error table of the standard single-stage voltage transformer, the error values of the voltage signal and the current signal collected in real time by the single-chip microcomputer 31 and the preset value are compared respectively, and the error value is used. Query the corresponding error coefficient from the value and error table, generate the corresponding voltage transformer error floating signal based on the error coefficient, and finally output the corresponding compensation error voltage signal based on the voltage transformer error floating signal, and then use the standard single-stage voltage transformer. The output of the voltage transformer is compensated, and the accuracy of the standard single-stage voltage transformer is improved without changing the original structure of the voltage transformer.

Please refer to FIG. 1 to FIG. 6 , the present invention needs to use the following standard voltage transformer error compensation device 100, including:

A voltage input channel 1, used to access the output voltage of the voltage transformer (not shown) to be compensated;

A current input channel 2, used to access the load current of the voltage transformer to be compensated;

An MCU control module 3, the input terminal is connected to the output terminals of the voltage input channel 1 and the current input channel 2, for collecting the voltage signal output by the voltage input channel 1 and the current signal output by the current input channel 2, and controlling The operation of the error compensation device 100;

a phase-shift circuit 4, the input terminal is connected to the output terminal of the voltage input channel 1, and is used for phase-shifting the input voltage signal;

A first digital-to-analog conversion chip 5, the input terminal is connected to the output terminal of the voltage input channel 1, and the digital control terminal is connected to the MCU control module 3, for performing analog-to-digital conversion on the input voltage signal;

A second digital-to-analog conversion chip 6, the input terminal is connected to the phase shift circuit 4, and the digital control terminal is connected to the MCU control module 3, for performing analog-to-digital conversion on the input voltage signal;

An adding circuit 7 , the input terminal of which is connected to the output terminal of the first digital-to-analog conversion chip 5 and the output terminal of the second digital-to-analog conversion chip 6 for superimposing the first digital-to-analog conversion chip 5 and the second digital-to-analog conversion chip 6 output voltage signal;

an error voltage signal isolation module 8, the input end is connected to the output end of the adding circuit 7, and is used for isolating the error voltage signal to produce a floating error voltage signal;

A display screen 9, connected to the MCU control module 3, for operating the error compensation device 100 and setting the error coefficient;

A power supply module 10 is connected to the MCU control module 3 , the error voltage signal isolation module 8 and the display screen 9 respectively, and is used for supplying power to the error compensation device 100 .

The voltage input channel 1 includes:

a first two-stage isolation voltage transformer 11, the input signal is the output voltage of the voltage transformer to be compensated;

A filter amplifying circuit 12 , the input terminal is connected to the secondary output voltage terminal of the first two-stage isolation voltage transformer 11 , and the output terminal is connected to the MCU control module 3 , the phase shift circuit 4 and the first digital-to-analog conversion chip 5 . Connection for filtering and amplifying the incoming voltage signal.

The current input channel 2 includes:

a sampling resistor 21;

A first filter circuit 22, the input end is connected to both ends of the sampling resistor 21, and the output end is connected to the MCU control module 3, for filtering the input current signal.

The MCU control module 3 includes:

A single chip 31 is connected to the first digital-to-analog conversion chip 5, the second digital-to-analog conversion chip 6, the display screen 9 and the power supply module 10, respectively, and is used to control the operation of the error compensation device 100. In specific implementation, As long as the single-chip microcomputer that can realize this function is selected from the existing technology, it is not limited to what type, such as the single-chip microcomputer of the STM32F103 series of ST company, and the control program is well known to those skilled in the art, which is a Can be obtained without creative labor;

A dual-channel AD signal acquisition module 32, one end is connected to the single-chip microcomputer 31, the other end is connected to the voltage input channel 1 and the current input channel 2, and the sampling time interval is set to 1 second;

a storage module 33, connected to the single-chip microcomputer 31, for storing the error table;

An RS232 interface 34 is connected to the single-chip microcomputer 31 for the error compensation device 100 to communicate with the outside world.

The error voltage signal isolation module 8 includes:

a second filter circuit 81, the input end is connected to the output end of the adding circuit 7;

an amplifying circuit 82, the input end of which is connected to the output end of the second filter circuit 81 for compensating the output voltage signal;

A second double-stage isolation voltage transformer 83, the high end of the primary side is connected to the output end of the amplifying circuit 82 and the input end of the second filter circuit 81, and the low end of the primary side is grounded; the second double-stage isolation voltage The output voltage of the transformer 83 is the ratio of the input voltage of the first double-stage isolation voltage transformer 11. When the input voltage and input current remain unchanged, the output voltage of the second double-stage isolation voltage transformer 83 is constant. , when different phases and amplitudes are required, the in-phase and quadrature component values can be adjusted.

A preferred embodiment of a standard voltage transformer error compensation method of the present invention includes the following steps:

Step S10, input the error value (including ratio difference and angle difference) of the standard voltage transformer under different working voltages and different load currents to the single-chip microcomputer through the RS232 interface or the display screen, and the single-chip computer stores the received error value in the storage module. in the error table;

Step S20, after the input voltage passes through the first two-stage isolation voltage transformer and the filter amplifying circuit, it is input to the two-channel AD signal acquisition module, and at the same time, the in-phase component signal and the quadrature component signal are separated by the phase-shift circuit as the in-phase component of the error signal. reference reference signals for the component and quadrature components;

Step S30, the input current is input to the dual-channel AD signal acquisition module after passing through the sampling resistor and the filter circuit;

Step S40, the single-chip microcomputer obtains the voltage value and the current value through the dual-channel AD signal acquisition module, obtains the error coefficient based on the voltage value and the current value, and generates the digital control quantities of the first digital-to-analog conversion chip and the second digital-to-analog conversion chip, It is used to control the size of the in-phase component and the quadrature component of the error signal; the error coefficient is the amplitude coefficient and phase coefficient of the output signal relative to the input signal;

The error coefficient is subdivided into 500 sets of data according to different input voltages and input currents; the input voltage range is 10% to 130% of 100V or 100/√3V, and a voltage data is saved every 5 (±2.5) percentage points, and the maximum Save 25 packets of data; the input current range is 0 ~ 100mA, save a group of current data every 5 (± 2.5) mA, save up to 20 packets of data, voltage and current horizontal and vertical corresponding to a total of 500 sets of data.

Step S50, the summing circuit synthesizes the in-phase component of the error signal output by the first digital-to-analog conversion chip and the quadrature component of the error signal output by the second digital-to-analog conversion chip into an error voltage signal;

Step S60: After the error voltage signal output by the adding circuit is output by the filter circuit, the amplifier circuit and the second two-stage isolation voltage transformer, a floating error compensation signal corresponding to the input voltage and input current is generated.

In the step S40, the error coefficient includes an amplitude coefficient and a phase coefficient.

The units of the amplitude coefficient and the phase coefficient are 1×10 ^-6 and 1 microradian respectively, and the resolution is 1×10 ^-6 ; the input voltage of the first double-stage isolation voltage transformer: 0～200V; the current-voltage conversion The input current of the module: 0～100mA; the output voltage of the second double-stage isolation voltage transformer: 0～0.1V, the maximum error is ±0.2%.

In the step S40, the obtaining of the error coefficient based on the voltage value and the current value is specifically:

The voltage value and the current value are respectively compared with a preset error table in the storage module, and a corresponding error value is searched based on the error table.

In the step S40, the obtaining of the error coefficient based on the voltage value and the current value is specifically:

Input the voltage value and the current value into a preset error function analytical formula to calculate the error value, and the formula of the error function analytical formula is ε(V, I). The storage module can store the error functions of multiple voltage transformers and correspond to voltage transformers with different numbers, that is, the same standard voltage transformer error compensation device can be used with multiple standard voltage transformers.

The experimental verification process of the present invention is as follows:

(1) The voltage is connected to the A and X terminals (voltage input channel);

(2) The current is connected to the I+ and I- terminals (current input channel);

(3) Adjust the voltage dial indicator, click the modify button, set any value between 0 and 1000PPM according to the size of the dial indicator and the size of the current, click save, wait for 2 seconds, the data will be saved to a fixed address, when the next time it arrives Under the same voltage and current, the saved corresponding data will be recalled;

(4) The dial indicator saves one data every 5 (±2.5) percentage points from 10% to 130%, and saves a maximum of 25 packets of data; the current saves from 0 to 100 mA at every 5 (±2.5) mA Save a set of data Save up to 20 packets of data, voltage and current horizontal and vertical corresponding to a total of 500 sets of data;

(5) The floating error voltage signal is output from the U+ and U- terminals;

(6) The output terminal of the voltage transformer after compensation is correspondingly converted into a' ₀ , x' ₀ .

The experimental transformers are two double-stage voltage transformers with a voltage level of 10kV (#1: model: HJS158, serial number: 1708051; #2: model: HJS, serial number: 8209), with an accuracy level of 0.01.

High-end differential mode, direct comparison measurements:

The two 10kV voltage transformers are directly compared and measured through the high-end difference measurement mode. The error measurement data is shown in the following table:

After the voltage transformer cascades the error signal generation module, the comparison measurement (high-end difference measurement):

The wiring diagram of the voltage transformer cascade error signal generation module, the secondary output of the transformer is connected to the voltage access A and X terminals of the module, and the current input is connected in series from the low end of the secondary output of the voltage transformer, as shown in Figure 6 shown. After cascading, the output of the transformer is converted to a' ₀ , x' ₀ .

Note: The unit of the quadrature component in the error reading of the transformer calibrator is minutes, while the unit of the quadrature component in the error module is urad, which should be converted once.

(1) Wiring method 1, #2 transformer proportional output cascade error module (linear correction relative to the proportional output)

The proportional output of the transformer #2 is connected to the voltage of the module and connected to the terminals A and X; the current terminals (I+, I-) are suspended; the error signal output U+ is connected to the high end of the proportional output of the #2 transformer, and the error signal output U- is connected to the calibration The difference measuring input terminal K of the calibrator; the power supply of the calibrator is connected to the excitation output of the #2 transformer; the difference measuring input end D of the calibrator is connected to the high end of the proportional output of the #1 transformer; 2 The proportional output of the transformer is short-circuited at the low end.

Comparison of experimental data before and after correction:

Wiring method 1, #2 transformer excitation output cascade error module (relative to the linear correction of excitation output)

#2 Transformer The transformer excitation output is connected to the voltage of the module and connected to the A and X terminals; the current terminals (I+, I-) are suspended; the error signal output U+ is connected to the high end of the #2 transformer excitation output, and the error signal output U- Connect the differential input terminal K of the calibrator; the power supply of the calibrator is connected to the excitation output of the #2 mutual inductor; the differential measuring input terminal D of the calibrator is connected to the high end of the proportional output of the #1 mutual inductor; the low end of the proportional output of the #1 mutual inductor Short to the low side of the proportional output of the #2 transformer.

Comparison of experimental data before and after correction:

Note: Analysis of the reasons for the jumping reading after supplementation: (1) The grounding of the experimental environment is not very good, and the ground signal has interference; (2) The output signal of the error module should be shielded to reduce the interference; (3) There is a certain amount of interference in the high-voltage power supply , that is, the secondary signal output by the transformer is not a clean sinusoidal signal.

To sum up, the advantages of the present invention are:

Since the error curve of each standard voltage transformer when it leaves the factory is a basically determined parameter, and it is relatively stable, the error value is mainly related to the current working voltage and load current. Therefore, by setting the storage module to store the error table of the standard voltage transformer or the analytical formula of the error function, the single-chip microcomputer separately collects the secondary voltage signal of the voltage transformer in the voltage input channel and the load current signal of the voltage transformer in the current input channel in real time. The corresponding error coefficient can be obtained from the current working voltage and load current. Based on the error coefficient, the corresponding voltage transformer error signal is generated, and the corresponding floating error compensation voltage signal is output through the error voltage signal isolation module. The error value generates the corresponding voltage transformer error floating signal to compensate the output of the voltage transformer, which greatly improves the accuracy level of the voltage transformer without changing the original structure of the voltage transformer.

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments we describe are only illustrative, rather than used to limit the scope of the present invention. Equivalent modifications and changes made by a skilled person in accordance with the spirit of the present invention should be included within the scope of protection of the claims of the present invention.

Claims (5)

1. a standard voltage transformer error compensation method, is characterized in that: comprise the steps: Step S10, input the error value of the standard voltage transformer under different working voltages and different load currents to the single-chip microcomputer through the RS232 interface or the display screen, and the single-chip computer stores the received error value in the error table in the storage module; Step S20, after the input voltage passes through the first two-stage isolation voltage transformer and the filter amplifying circuit, it is input to the two-channel AD signal acquisition module, and at the same time, the in-phase component signal and the quadrature component signal are separated by the phase-shift circuit as the in-phase component of the error signal. reference reference signals for the component and quadrature components; Step S30, the input current is input to the dual-channel AD signal acquisition module after passing through the sampling resistor and the filter circuit; Step S40, the single-chip microcomputer obtains the voltage value and the current value through the dual-channel AD signal acquisition module, obtains the error coefficient based on the voltage value and the current value, and generates the digital control quantities of the first digital-to-analog conversion chip and the second digital-to-analog conversion chip, Used to control the magnitude of the in-phase component and the quadrature component of the error signal; Step S50, the summing circuit synthesizes the in-phase component of the error signal output by the first digital-to-analog conversion chip and the quadrature component of the error signal output by the second digital-to-analog conversion chip into an error voltage signal; Step S60: After the error voltage signal output by the adding circuit is output by the filter circuit, the amplifier circuit and the second two-stage isolation voltage transformer, a floating error compensation signal corresponding to the input voltage and input current is generated. 2 . The standard voltage transformer error compensation method according to claim 1 , wherein in the step S40 , the error coefficient includes an amplitude coefficient and a phase coefficient. 3 . 3 . The standard voltage transformer error compensation method according to claim 1 , wherein in the step S40 , the obtaining of the error coefficient based on the voltage value and the current value is specifically: respectively dividing the voltage The value and the current value are compared with a preset error table in the storage module, and a corresponding error value is searched based on the error table. 4 . The standard voltage transformer error compensation method according to claim 1 , wherein in the step S40 , the obtaining the error coefficient based on the voltage value and the current value is specifically: taking the voltage value The error value is calculated analytically by inputting the preset error function and current value. 5 . The standard voltage transformer error compensation method according to claim 1 , wherein in the step S40 , the obtaining the error coefficient based on the voltage value and the current value is specifically: the voltage value After inputting the preset excitation current function analytical formula and the current value to calculate the error analytical formula, the corresponding error value is obtained.

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