A DC sampling method for electric energy meters for ultra-high power DC application scenarios

Abstract

The invention relates to the technical field of electric energy meter sampling, and in particular to an electric energy meter DC sampling method for ultra-high power DC application scenarios; the method comprises the following steps: S1, collecting current values ​​and inputting them into a single chip microcomputer; S2, obtaining a heat dissipation temperature coefficient after encapsulation of the electric energy meter and a coefficient of change of resistance of a manganese copper shunt with temperature; S3, calculating a linear relationship between heat dissipation and temperature after encapsulation of the electric energy meter; S4, calculating a linear relationship between fitted resistance of the manganese copper shunt and temperature change; S5, calculating a temperature compensation value, correcting the current value collected by the manganese copper shunt, judging whether the temperature coefficient corresponding to the corrected current value is qualified, and performing step S6 when the corrected current value is unqualified, otherwise, not performing step S6; S6, iterating the corrected current value using the method in steps S1-S5 until the temperature coefficient corresponding to the corrected current value is judged to be qualified; the invention achieves the requirements of high efficiency and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy meter sampling, and in particular to an electric energy meter direct current sampling method for ultra-high power direct current application scenarios. Background Art

[0002] The electric energy meter is a key equipment in the field of electricity measurement and management. It has a series of diverse and vital functions and is deeply embedded in all aspects of modern power system operation and users' electricity consumption life. At present, there are the following problems in the design of electric energy meters for DC large current sampling: In the process of DC large current sampling, when a manganese copper shunt is used as a sampling element, the long-term operation of the large current will cause the manganese copper shunt to heat up, resulting in a large sampling resistance. At the same time, the resistance of the voltage sampling resistor also changes due to temperature rise, thus affecting the measurement accuracy.

[0003] Chinese patent CN117761386A discloses a method for maintaining high-accuracy measurement of a smart energy meter under a wide temperature range, which adopts a magnetic latching manganese copper relay with a temperature measurement function and a single-phase smart energy meter MCU; the change in the temperature value on the sampled manganese copper is detected by an NTC temperature sensor; the temperature drift curve of the manganese copper shunt of the magnetic latching relay of this type is pre-set to compensate for the current sampling value; finally, the sampling current value of the single-phase smart energy meter is not affected by the temperature drift of the current sampling manganese copper itself, and the NTC temperature sensor adopts a silver outer shell; the silver outer shell is installed on the copper foot bracket of the manganese copper of the manganese copper shunt welded to the magnetic latching manganese copper relay; however, the above method has a complicated manufacturing process, high design cost and difficulty, and is difficult to meet the requirements of high efficiency and reliability.

[0004] Therefore, there is an urgent need to provide a DC sampling method for electric energy meters for ultra-high power DC application scenarios, which can achieve high efficiency and reliability requirements compared with the existing technology. Summary of the invention

[0005] The present invention solves the technical problems existing in the prior art and provides a DC sampling method for an electric energy meter for ultra-high power DC application scenarios.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A DC sampling method for an electric energy meter for ultra-high power DC application scenarios comprises the following steps: S1. Use a manganese-copper shunt to collect current values, process the collected current values, and input them into a single-chip microcomputer; S2, obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter and the temperature variation coefficient of the resistance of the manganese copper shunt; S3. Calculate the linear relationship between heat dissipation and temperature after encapsulation of the electric energy meter according to the heat dissipation temperature coefficient after encapsulation of the electric energy meter; S4. Calculate the linear relationship between the resistance of the manganese copper shunt and the temperature according to the coefficient of resistance variation of the manganese copper shunt and the linear relationship between the heat dissipation and the temperature after the electric energy meter is packaged; S5. Calculate the temperature compensation value according to the calculated linear relationship between the resistance value of the manganese-copper shunt and the temperature change, and correct the current value collected by the manganese-copper shunt according to the temperature compensation value to obtain the corrected current value, and judge whether the temperature coefficient corresponding to the corrected current value is qualified. If it is unqualified, perform step S6, otherwise, do not perform step S6; S6. Iterate the corrected current value using the method in steps S1-S5 until the temperature coefficient corresponding to the corrected current value is determined to be qualified.

[0007] Furthermore, in step S3, the linear relationship between heat dissipation and temperature after encapsulation of the electric energy meter is calculated according to the following formula: ; In the above formula, It represents the linear relationship between the heat dissipation of the electric energy meter after packaging and the temperature, n represents the heat dissipation temperature coefficient of the electric energy meter after packaging, Indicates the measured temperature. Indicates the sampling frequency of the microcontroller.

[0008] Furthermore, in step S4, the linear relationship between the fitting resistance of the manganese-copper shunt and the change in temperature is calculated according to the following formula: ; ; In the above formula, Indicates the current value received by the microcontroller on the previous step. Indicates the resistance value of the manganese copper shunt corresponding to T, represents the specific heat capacity of the manganese bronze shunt, represents the volume of the manganese bronze shunt, represents the basic temperature, represents the initial resistance of the manganese copper shunt, k represents the coefficient of change of the resistance of the manganese copper shunt with temperature, It shows the linear relationship between the resistance of manganese-copper shunt and temperature.

[0009] Furthermore, in step S5, the temperature compensation value is calculated according to the following formula: ; In the above formula, Indicates the temperature compensation value, Represents the error temperature compensation coefficient.

[0010] Furthermore, in step S5, the specific method for correcting the current value collected by the manganese bronze shunt according to the temperature compensation value is: adding the temperature compensation value to the current value collected by the manganese bronze shunt to obtain a corrected current value.

[0011] Furthermore, in step S2, the method for obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter is as follows: in a constant temperature and humidity environment, multiple points are set within the working temperature range of the electric energy meter, and the resistance change after the electric energy meter is encapsulated is measured. During the measurement process, the resistance values ​​at the multiple points set are recorded to form multiple first sampling points, each of which includes a temperature and a first resistance value, and a linear fitting relationship between the temperature and the first resistance value is obtained, thereby obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter, which is specifically obtained by the following formula: ; In the above formula, represents the first resistance value, and x represents the temperature.

[0012] Furthermore, in step S2, the specific method for obtaining the coefficient of change of resistance of the manganese copper shunt with temperature is as follows: recording the resistance of the manganese copper shunt at multiple set points to form multiple second sampling points, each second sampling point includes temperature and second resistance, and obtaining a linear fitting relationship between temperature and second resistance, thereby obtaining the coefficient of change of resistance of the manganese copper shunt with temperature, which is specifically obtained by the following formula: ; In the above formula, Indicates the second resistance value.

[0013] Furthermore, in step S1, a manganese copper shunt is used to collect current values, and after the collected current values ​​are processed, the specific method for inputting them into the single-chip microcomputer is as follows: the current enters the manganese copper shunt from the middle of the manganese copper shunt, and after passing through the manganese copper shunt, the current will generate a voltage signal proportional to the input current at both ends of the manganese copper shunt. After the voltage signal passes through the MELF resistor, it is input into the operational amplifier, the voltage signal is differentially amplified, the voltage signal after differential amplification is added to the low-pass filter, and then input into the ADC channel of the single-chip microcomputer.

[0014] Furthermore, in step S1, a manganese copper shunt with a temperature drift coefficient of 40 ppm and a MELF resistor with a temperature drift coefficient of 25 ppm are selected.

[0015] Furthermore, in step S5, the method for judging whether the temperature coefficient corresponding to the corrected current value is qualified is: when the temperature coefficient corresponding to the corrected current value is less than 0.018% / °C, it is qualified, otherwise it is unqualified; The temperature coefficient is calculated by the following formula: ; In the above formula, represents the temperature coefficient, Indicates the upper limit temperature, Indicates the lower limit temperature, Indicates the current error value of the upper temperature limit, Indicates the current error value at the lower limit temperature.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a high-precision, low-temperature drift, low-resistance manganese-copper shunt and a high-precision, high-stability MELF resistor. Based on the temperature error value of transient current measurement, the input current of the manganese-copper shunt is compensated, and an iterative correction process is realized to ensure the accuracy of the sampling signal. At the same time, it also ensures that the measurement accuracy requirement of the entire electric energy meter reaches 0.5 level, which can meet the requirements of high efficiency and reliability.

[0017] (2) The current operation error change of the manganese copper shunt with a temperature drift coefficient of 40ppm used in the present invention is reduced by 0.1% compared with the manganese copper shunt with a temperature drift coefficient of 60ppm; the current operation error change of the MELF resistor with a temperature drift coefficient of 25ppm used in the present invention is reduced by 0.375% compared with the MELF resistor with a temperature drift coefficient of 100ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are not all embodiments of the present invention, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the protection scope of the present invention.

[0020] like Figure 1 As shown, the present invention provides a DC sampling method for an electric energy meter for ultra-high power DC application scenarios, comprising the following steps: S1. Use manganese copper shunt and MELF resistor to collect current, convert it into voltage signal and input it into ADC channel of single chip microcomputer; specifically: use manganese copper shunt with temperature drift coefficient of 40ppm, large current enters manganese copper shunt from the middle of the manganese copper shunt, after passing through the manganese copper shunt, large current will generate tiny voltage signal proportional to the input large current at both ends of the manganese copper shunt, the voltage signal passes through MELF resistor with temperature drift coefficient of 25ppm, and then input into high-precision operational amplifier, differentially amplifies the tiny voltage signal, adds the voltage signal after differential amplification into low-pass filter to suppress noise, and inputs the voltage signal into ADC channel of single chip microcomputer after conditioning.

[0021] S2. Obtain the heat dissipation temperature coefficient after encapsulation of the electric energy meter and the temperature variation coefficient of the resistance of the manganese copper shunt; the specific method is: (1) The specific method for obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter is as follows: in a constant temperature and humidity environment, multiple points are set within the working temperature range of the electric energy meter, and the difference between the multiple points is selected between 20°C and 50°C. The resistance change of the encapsulated electric energy meter is measured. During the measurement process, the resistance values ​​at the multiple points are recorded to form multiple first sampling points. Each first sampling point includes temperature and first resistance. The linear fitting relationship between temperature and first resistance is obtained, thereby obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter. The expression of the linear fitting relationship between temperature and first resistance is as follows: ; In the above formula, represents the first resistance value, x represents the temperature, and n represents the heat dissipation temperature coefficient after the electric energy meter is packaged.

[0022] (2) The specific method for obtaining the coefficient of variation of the resistance of the manganese copper shunt with temperature is as follows: record the resistance of the manganese copper shunt at multiple set points to form multiple second sampling points, each of which includes temperature and second resistance, obtain the linear fitting relationship between temperature and second resistance, and thus obtain the coefficient of variation of the resistance of the manganese copper shunt with temperature. The expression of the linear fitting relationship between temperature and second resistance is as follows: ; In the above formula, represents the second resistance value, and k represents the coefficient of change of the resistance value of the manganese-copper shunt with temperature.

[0023] S3. According to the heat dissipation temperature coefficient after the electric energy meter is packaged, the linear relationship between the heat dissipation and temperature after the electric energy meter is packaged is calculated. The calculation relationship is as follows: ; In the above formula, It indicates the linear relationship between heat dissipation and temperature after encapsulation of the energy meter. Indicates the measured temperature. Indicates the sampling frequency of the microcontroller.

[0024] S4. According to the coefficient of change of resistance of manganese copper shunt with temperature and the linear relationship between heat dissipation and temperature after encapsulation of electric energy meter, the linear relationship between the fitted resistance of manganese copper shunt and temperature is calculated. The calculation relationship is as follows: ; ; In the above formula, Indicates the current value received by the microcontroller on the previous step. Indicates the resistance value of the manganese copper shunt corresponding to T, represents the specific heat capacity of the manganese bronze shunt, represents the volume of the manganese bronze shunt, represents the basic temperature, Indicates the initial resistance of the manganese bronze shunt, It shows the linear relationship between the resistance of manganese-copper shunt and temperature.

[0025] S5. Calculate the temperature compensation value based on the calculated linear relationship between the fitted resistance of the manganese copper shunt and the temperature change, and correct the current value collected by the manganese copper shunt based on the temperature compensation value. After obtaining the corrected current value, make a judgment to determine whether the temperature coefficient corresponding to the corrected current value is qualified. If it is unqualified, perform step S6 to prevent the sampling signal from being affected by the temperature change of the manganese copper shunt.

[0026] The temperature compensation value is calculated by the following formula: ; In the above formula, Indicates the temperature compensation value, Represents the error temperature compensation coefficient.

[0027] The specific method for correcting the current value collected by the manganese copper shunt according to the temperature compensation value is: adding the temperature compensation value to the current value collected by the manganese copper shunt to obtain the corrected current value.

[0028] The method for judging whether the temperature coefficient corresponding to the corrected current value is qualified is: when the temperature coefficient corresponding to the corrected current value is less than 0.018% / °C, it is qualified, otherwise it is unqualified.

[0029] The temperature coefficient is calculated by the following formula: ; In the above formula, represents the temperature coefficient, Indicates the upper limit temperature, Indicates the lower limit temperature, Indicates the current error value of the upper temperature limit, Indicates the current error value at the lower limit temperature.

[0030] S6. Iterate the corrected current value using the method in steps S1-S5 until the temperature coefficient corresponding to the corrected current value is qualified.

[0031] The present invention adopts a high-precision, low-temperature drift, low-resistance manganese-copper shunt and a high-precision, high-stability MELF resistor, and compensates the input current of the manganese-copper shunt based on the temperature error value of transient current measurement, thereby realizing an iterative correction process, ensuring the accuracy of the sampling signal, and also ensuring that the entire electric energy meter reaches the measurement accuracy requirement of level 0.5.

[0032] The error change of the manganese-copper shunt with a temperature drift coefficient of 40ppm used in the present invention when running at a large current for 2 hours is 0.2%, while the error change of the manganese-copper shunt with a temperature drift coefficient of 60ppm when running at a large current for 2 hours is 0.3%; therefore, the error change of the manganese-copper shunt with a temperature drift coefficient of 40ppm used in the present invention is reduced by 0.1% compared with the manganese-copper shunt with a temperature drift coefficient of 60ppm.

[0033] The error change of the MELF resistor with a temperature drift coefficient of 25ppm used in the present invention when running at a large current for 2 hours is 0.1215%, while the error change of the MELF resistor with a temperature drift coefficient of 100ppm when running at a large current for 2 hours is 0.5%; therefore, the error change of the MELF resistor with a temperature drift coefficient of 25ppm used in the present invention is reduced by 0.375% compared with the MELF resistor with a temperature drift coefficient of 100ppm.

[0034] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A DC sampling method for electric energy meters for ultra-high power DC application scenarios, characterized in that: The following steps are involved: S1. Use a manganese-copper shunt to collect current values, process the collected current values, and input them into a single-chip microcomputer; S2, obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter and the temperature variation coefficient of the resistance of the manganese copper shunt; S3. Calculate the linear relationship between heat dissipation and temperature after encapsulation of the electric energy meter according to the heat dissipation temperature coefficient after encapsulation of the electric energy meter; S4. Calculate the linear relationship between the resistance of the manganese copper shunt and the temperature according to the coefficient of resistance variation of the manganese copper shunt and the linear relationship between the heat dissipation of the electric energy meter after packaging and the temperature; S5. Calculate the temperature compensation value according to the calculated linear relationship between the resistance value of the manganese-copper shunt and the temperature change, and correct the current value collected by the manganese-copper shunt according to the temperature compensation value to obtain the corrected current value, and judge whether the temperature coefficient corresponding to the corrected current value is qualified. If it is unqualified, perform step S6, otherwise, do not perform step S6; S6. Iterate the corrected current value using the method in steps S1-S5 until the temperature coefficient corresponding to the corrected current value is determined to be qualified.

2. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 1 is characterized in that: In step S3, the linear relationship between heat dissipation and temperature after encapsulation of the electric energy meter is calculated according to the following formula: ； In the above formula, It represents the linear relationship between the heat dissipation of the electric energy meter after packaging and the temperature, n represents the heat dissipation temperature coefficient of the electric energy meter after packaging, Indicates the measured temperature. Indicates the sampling frequency of the microcontroller.

3. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 2 is characterized in that: In step S4, the linear relationship between the resistance value of the manganese-copper shunt and the temperature is calculated according to the following formula: ； ； In the above formula, Indicates the current value received by the microcontroller on the previous step. Indicates the resistance value of the manganese copper shunt corresponding to T, represents the specific heat capacity of the manganese bronze shunt, represents the volume of the manganese bronze shunt, represents the basic temperature, represents the initial resistance of the manganese copper shunt, k represents the coefficient of change of the resistance of the manganese copper shunt with temperature, It shows the linear relationship between the resistance of manganese-copper shunt and temperature.

4. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 3 is characterized in that: In step S5, the temperature compensation value is calculated according to the following formula: ； In the above formula, Indicates the temperature compensation value, Represents the error temperature compensation coefficient.

5. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 4, characterized in that: In step S5, the specific method for correcting the current value collected by the manganese bronze shunt according to the temperature compensation value is: adding the temperature compensation value to the current value collected by the manganese bronze shunt to obtain the corrected current value.

6. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 3 is characterized in that: In step S2, the method for obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter is as follows: in a constant temperature and humidity environment, multiple points are set within the working temperature range of the electric energy meter, and the resistance change after the electric energy meter is encapsulated is measured. During the measurement process, the resistance values ​​at the multiple points set are recorded to form multiple first sampling points, each of which includes a temperature and a first resistance value, and a linear fitting relationship between the temperature and the first resistance value is obtained, thereby obtaining the heat dissipation temperature coefficient of the encapsulated electric energy meter, which is specifically obtained by the following formula: ； In the above formula, represents the first resistance value, and x represents the temperature.

7. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 6, characterized in that: In step S2, the specific method for obtaining the coefficient of change of resistance of the manganese copper shunt with temperature is as follows: record the resistance of the manganese copper shunt at multiple set points to form multiple second sampling points, each of which includes temperature and second resistance, obtain the linear fitting relationship between temperature and second resistance, and thus obtain the coefficient of change of resistance of the manganese copper shunt with temperature, which is specifically obtained by the following formula: ； In the above formula, Indicates the second resistance value.

8. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 1, characterized in that: In step S1, a manganese copper shunt is used to collect current values. After the collected current values ​​are processed, the specific method for inputting them into the single-chip microcomputer is as follows: the current enters the manganese copper shunt from the middle of the manganese copper shunt. After passing through the manganese copper shunt, the current will generate a voltage signal proportional to the input current at both ends of the manganese copper shunt. After passing through the MELF resistor, the voltage signal is input into the operational amplifier, the voltage signal is differentially amplified, the voltage signal after differential amplification is added to the low-pass filter, and then input into the ADC channel of the single-chip microcomputer.

9. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 8, characterized in that: In step S1, a manganese copper shunt with a temperature drift coefficient of 40ppm and a MELF resistor with a temperature drift coefficient of 25ppm are selected.

10. The method for DC sampling of electric energy meters for ultra-high power DC application scenarios according to claim 1, characterized in that: In step S5, the method for judging whether the temperature coefficient corresponding to the corrected current value is qualified is: when the temperature coefficient corresponding to the corrected current value is less than 0.018% / °C, it is qualified, otherwise it is unqualified; The temperature coefficient is calculated by the following formula: ； In the above formula, represents the temperature coefficient, Indicates the upper temperature limit, Indicates the lower limit temperature, Indicates the current error value of the upper temperature limit, Indicates the current error value at the lower limit temperature.

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