Deviation detection circuit, deviation self-calibration method, and novel intelligent electric energy meter

Abstract

The present invention belongs to the technical field of error calibration of electric energy meters, and specifically relates to a deviation detection circuit, a deviation self-calibration method, and a new type of intelligent electric energy meter. It includes a voltage-stabilized power supply VCC and a resistor string R5 and R6 for online calibration of the input voltage or input current of the intelligent electric energy meter; the first end of the resistor string R5 is connected to the voltage-stabilized power supply VCC, the second end of the resistor string R5 is connected to the first end of the resistor string R6, the second end of the resistor string R5 and the first end of the resistor string R6 are both connected to the ADC sampling channel of the single-chip microcomputer, and the deviation detection circuit is connected to the circuit of the intelligent electric energy meter through the ADC sampling channel of the single-chip microcomputer. According to the above circuit, when the resistance value of the sampling resistor drifts due to environmental changes, thereby changing the accuracy of the electric energy meter, the electric energy meter recalibrates the electric energy meter online by correcting the resistance ratio, and converts the requirements for the accuracy of the sampling resistor into the accuracy requirements for the voltage-stabilized power supply, the ADC sampling channel of the single-chip microcomputer, and the standard resistor, thereby improving the stability of the error accuracy and reducing the maintenance cost.

Description

Technical Field

[0001] The invention belongs to the technical field of error calibration of electric energy meters, and in particular relates to a deviation detection circuit, a deviation self-calibration method, and a novel intelligent electric energy meter. Background Art

[0002] In the metering circuit of smart energy meters, resistors, as basic sampling components, play a vital role in the metering accuracy of smart energy meters. Generally speaking, the metering accuracy of energy meters is calibrated when the meters leave the factory, and the accuracy will basically not change when the wiring is good and the metering environment is stable. However, the resistance value will change with external environmental changes such as temperature and humidity. When the energy meter is running in a high temperature or high humidity environment, it will cause the resistance value of the sampling circuit to drift, resulting in a synchronous change in the metering accuracy of the energy meter.

[0003] The sampling circuit of the smart energy meter includes voltage sampling and current sampling. The voltage sampling circuit is as follows: Figure 1 As shown, the current sampling circuit is as follows Figure 2 As shown. According to the accuracy requirements of the energy meter, resistors with appropriate accuracy and temperature drift must be selected during design. The relationship between the voltage sampling signal and the voltage input signal, and the relationship between the current sampling signal and the current input signal of the smart energy meter are:

[0004] V P =UA*RA8 / (RA1+RA2+RA3+RA4+RA5+RA6+RA7+RA8),

[0005] I P -I N =IA / N*(R1+R2),

[0006] Where V P is the voltage sampling signal of the energy meter, that is, the voltage value detected by the internal sampling circuit of the energy meter. UA is the voltage input signal of the energy meter, that is, the voltage value of the external input of the energy meter. RA1~RA7 use the same resistor, R1 and R2 use the same resistor, I P -I N is the current sampling signal of the electric energy meter, IA is the current input signal of the electric energy meter, that is, the current value of the external input of the electric energy meter, and N is the transformer ratio.

[0007] When designing the energy meter program, the nominal values ​​of the above resistors will be substituted into the formula to calculate the input voltage and current values. However, since each resistor is not absolutely equal to the nominal value, the above formula will introduce some errors. By applying a standard voltage source and current source to the energy meter and comparing them with the voltage and current values ​​calculated by the energy meter, the metering value of the energy meter can be calibrated, thereby eliminating the metering error caused by the resistance deviation.

[0008] The above calibration can ensure that the error of the energy meter under normal conditions can meet the requirements. However, when the environment changes drastically, the error of the energy meter will also change due to the drift of the resistance value, and even exceed the most basic accuracy requirements of the energy meter. For the energy meter that has been installed on site, there is no opportunity to recalibrate the measurement accuracy after the error drift occurs. Summary of the invention

[0009] The resistance values ​​of resistors RA1 to RA7 are the same, and the resistance values ​​of resistors R1 and R2 are the same. From the relationship between the sampling signal and the input signal of the electric energy meter, it can be seen that the accuracy of voltage sampling depends on the change in the ratio between the two resistance values ​​of RA1 to RA7 and RA8, and the accuracy of current sampling depends on the change in one resistance value of R1 and R2. For sampling resistors, resistors of the same specification and model and the same batch are almost completely consistent in their production materials, production processes, and production environments. When their working environment changes, the resistance drift law generated by the resistor itself is basically the same. Therefore, as long as the change law of the two resistance ratios of voltage sampling and the current sampling resistor is known, the error change of the electric energy meter caused by the resistance drift can be further corrected.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a deviation detection circuit, comprising a voltage regulated power supply VCC and a resistor string R5, R6 for online calibration of an input voltage or input current of a smart electric energy meter;

[0012] The first end of the resistor string R5 is connected to the voltage-stabilized power supply VCC, the second end of the resistor string R5 is connected to the first end of the resistor string R6, the second end of the resistor string R5 and the first end of the resistor string R6 are both connected to the ADC sampling channel Detect of the microcontroller, and the deviation detection circuit is connected to the circuit of the smart electric energy meter through the ADC sampling channel Detect of the microcontroller.

[0013] As a preferred solution, the second end of the resistor string R6 is grounded.

[0014] As a preferred solution, the number of resistors constituting the resistor string R5 and R6 and the connection method of the resistors are determined according to whether the deviation detection circuit is used to detect voltage deviation or current deviation and the voltage sampling range of the single chip microcomputer.

[0015] As a preferred solution, when the deviation detection circuit is used for voltage deviation detection, the resistor string R5 is composed of multiple resistors with the same resistance value connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R5 are the same as RA1~RA7; the resistor string R6 is composed of multiple resistors with the same resistance value connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R6 are the same as RA8.

[0016] As a preferred solution, when the deviation detection circuit is used for current deviation detection, the resistor string R5 is composed of multiple resistors connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R5 are the same as those of R1 and R2; the resistor string R6 is a single resistor.

[0017] As a preferred solution, the accuracy and stability of the resistor string R6 are higher than the resistors constituting the resistor string R5.

[0018] In a second aspect, the present invention provides a deviation self-calibration method, based on the sampling circuit inside the smart energy meter and the above-mentioned deviation detection circuit, after the first calibration, the single-chip microcomputer detects the voltage value of the sampling channel at a certain interval, and calculates the resistance ratio of the resistors constituting the resistor string R5 and R6 after each detection;

[0019] When the sampling signal detected by the single-chip microcomputer changes, the input voltage and input current of the calibrated smart energy meter are automatically recalculated according to the resistance ratio corresponding to the sampling signal detected by the current deviation detection circuit, the relationship between the voltage sampling signal and the voltage input signal of the smart energy meter, and the relationship between the current sampling signal and the current input signal of the smart energy meter, so as to realize online calibration of the accuracy of the smart energy meter.

[0020] In a third aspect, the present invention provides a novel smart energy meter capable of online calibrating input voltage and input current sampled by the smart energy meter, wherein the novel smart energy meter comprises a deviation detection circuit as described above.

[0021] The beneficial effects of the present invention are:

[0022] 1. When the sampling resistor drifts due to environmental changes, causing the accuracy of the electric energy meter to change, the smart electric energy meter can recalibrate the accuracy of the electric energy meter online by correcting the resistance ratio or resistance value, without having to remove the meter from the site and return it to the factory for recalibration, effectively improving the error accuracy stability and reducing maintenance costs.

[0023] 2. Through the self-calibration method of voltage deviation and current deviation, the requirements for sampling resistor accuracy can be effectively transformed into the accuracy requirements for voltage regulator, ADC sampling channel of microcontroller, and standard resistor, effectively improving the error accuracy stability and reducing the cost of calibration and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is the voltage sampling circuit diagram of the smart electric energy meter.

[0026] Figure 2 It is the current sampling circuit diagram of the smart electric energy meter.

[0027] Figure 3 is a circuit diagram of a deviation detection circuit.

[0028] Figure 4 It is a schematic diagram of the connection between the deviation detection circuit and the internal circuit of the smart energy meter through the microcontroller sampling channel. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] The sampling circuit of the smart energy meter includes voltage sampling and current sampling. The voltage sampling circuit is as follows: Figure 1 As shown, the current sampling circuit is as follows Figure 2 According to the accuracy requirements of the energy meter, resistors with appropriate accuracy and temperature drift must be selected during design. The relationship between the voltage sampling signal and the voltage input signal, and the relationship between the current sampling signal and the current input signal of the energy meter are as follows:

[0031] V P =UA*RA8 / (RA1+RA2+RA3+RA4+RA5+RA6+RA7+RA8)——Formula 1,

[0032] I P -I N =IA / N*(R1+R2)——Formula 2,

[0033] Where V Pis the voltage sampling signal of the energy meter, that is, the voltage value detected by the internal sampling circuit of the energy meter. UA is the voltage input signal of the energy meter, that is, the voltage value of the external input of the energy meter. RA1~RA7 use the same resistor, R1 and R2 use the same resistor, I P -I N is the current sampling signal of the electric energy meter, IA is the current input signal of the electric energy meter, that is, the current value of the external input of the electric energy meter, and N is the transformer ratio.

[0034] According to formula 1, let the resistance of RA1~RA7 be r1, and the resistance of RA8 be r2, then formula 1 can be simplified to formula 3:

[0035]

[0036] According to Formula 2, let R1=R2=r3, Formula 2 can be simplified to Formula 4:

[0037]

[0038] Resistors of the same specification and model and the same batch are almost completely identical in production materials, production processes, and production environments. When their working environment changes, the resistance drift patterns produced by the resistors themselves are also basically the same. Therefore, as long as the change patterns of r1 / r2 and r3 are known, the error changes of the electric energy meter caused by the resistance drift can be further corrected by measuring the calibration value.

[0039] Therefore, refer to Figure 3 , This specification provides a deviation detection circuit, including a voltage-stabilized power supply VCC and a resistor string R5, R6 for online calibration of the input voltage or input current of a smart energy meter;

[0040] The first end of the resistor string R5 is connected to the voltage-stabilized power supply VCC, the second end of the resistor string R5 is connected to the first end of the resistor string R6, the second end of the resistor string R6 is grounded, the second end of the resistor string R5 and the first end of the resistor string R6 are both connected to the ADC sampling channel Detect of the single-chip microcomputer, and the deviation detection circuit is connected to the circuit of the smart electric energy meter through the ADC sampling channel Detect of the single-chip microcomputer.

[0041] Furthermore, the number of resistors constituting the resistor strings R5 and R6 and the connection method of the resistors are determined according to whether the deviation detection circuit is used to detect voltage deviation or current deviation and the voltage sampling range of the single chip microcomputer.

[0042] Specific:

[0043] When the deviation detection circuit is used for voltage deviation detection, the resistor string R5 is composed of multiple resistors with the same resistance value connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R5 are the same as RA1~RA7; the resistor string R6 is composed of multiple resistors with the same resistance value connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R6 are the same as RA8.

[0044] When the deviation detection circuit is used for current deviation detection, the resistor string R5 is composed of multiple resistors connected in series or in parallel, and the specifications and models of the resistors constituting the resistor string R5 are the same as those of R1 and R2; the resistor string R6 is a standard resistor, and the accuracy and stability of the resistor string R6 are higher than those of the resistors constituting the resistor string R5.

[0045] The circuit for detecting voltage deviation and the circuit for detecting current deviation have the same structure. The new intelligent electric energy meter encapsulates both the voltage deviation detection circuit and the current deviation detection circuit to realize the detection of voltage and current deviation.

[0046] The present specification also provides a new type of smart energy meter, which can online calibrate the input voltage and input current sampled by the smart energy meter. The new type of smart energy meter includes a deviation detection circuit as described above. The circuit for detecting voltage deviation and the circuit for detecting current deviation have the same structure. The new type of smart energy meter simultaneously encapsulates the voltage deviation detection circuit and the current deviation detection circuit to realize the detection of voltage and current deviations.

[0047] This specification also provides a deviation self-calibration method, based on the sampling circuit inside the smart energy meter and the above-mentioned deviation detection circuit. After the first meter calibration, the single-chip microcomputer detects the voltage value of the sampling channel at a certain interval, and calculates the resistance ratio of the resistor string R5 and R6 after each detection;

[0048] When the sampling signal detected by the single-chip microcomputer changes, the input voltage and input current of the calibrated smart energy meter are automatically recalculated according to the resistance ratio corresponding to the sampling signal detected by the current deviation detection circuit, the relationship between the voltage sampling signal and the voltage input signal of the smart energy meter, and the relationship between the current sampling signal and the current input signal of the smart energy meter, so as to realize online calibration of the accuracy of the smart energy meter.

[0049] Specific:

[0050] When the deviation detection circuit is used for voltage deviation detection, the resistor string R5 is formed by a plurality of resistors with a resistance value of r1 connected in series or in parallel, and the resistance value of the resistor R5 is recorded as m*r1, and the resistor string R6 is formed by a plurality of resistors with a resistance value of r2 connected in series or in parallel, and the resistance value of the resistor string R6 is recorded as n*r2. The values ​​of m and n are adjusted according to the range of the sampling voltage of the single-chip computer, the combination form of the resistors with a resistance value of r1, and the combination form of the resistors with a resistance value of r2.

[0051] The resistor string R5 is composed of m resistors with a resistance value of r1. If the resistance value of resistor r1 is large, it is connected in parallel to make the voltage value V detect Within the detection range of the single chip microcomputer, the total resistance value of the resistor string R5 is r1 / m; if the resistance value of the resistor r1 is very small, a series connection is used to make the voltage value V detect Within the detection range of the single chip microcomputer, the total resistance value of the resistor string R5 is m*r1 at this time; the design rule of the resistor string R6 is the same as the design rule of the resistor string R5.

[0052] According to the deviation detection circuit, the relationship between resistors r1 and r2 is (Formula 5):

[0053]

[0054] When performing voltage deviation self-calibration, after the first calibration, the microcontroller detects the voltage value V of the sampling channel at a certain interval. detect , and calculate the value of r1 / r2 according to formula 5 after each detection;

[0055] When the sampling signal detected by the single chip microcomputer changes, the input voltage of the smart energy meter is calibrated according to the value of r1 / r2 currently calculated, the relationship between the voltage sampling signal of the smart energy meter and the voltage input signal (Formula 3).

[0056] When the deviation detection circuit is used for current deviation detection, the resistor string R5 is formed by a plurality of resistors with a resistance value of r3 connected in series or in parallel, and the resistance value of the resistor string R5 is recorded as k*r3, and the resistor string R6 is a resistor with a resistance value of R, and the accuracy and stability of the resistor string R6 are higher than the resistor with a resistance value of r3. Among them, the value of k is adjusted according to the range of the sampling voltage of the single chip computer and the combination form of the resistor with a resistance value of r3.

[0057] The resistor string R5 is composed of k resistors with a resistance value of r3. If the resistance value of resistor r3 is large, it is connected in parallel to make the voltage value V detect Within the detection range of the single chip microcomputer, the total resistance value of the resistor string R5 is r1 / k; if the resistance value of the resistor r1 is very small, the series connection is adopted to make the voltage value V detectWithin the detection range of the single chip microcomputer, the total resistance value of the resistor string R5 is k*r1.

[0058] According to the deviation detection circuit, the relationship between resistors r3 and R is (Formula 6):

[0059]

[0060] When performing current deviation self-calibration, after the first calibration, the microcontroller detects the voltage value V of the sampling channel at a certain interval. detect , and calculate the value of r3 after each detection;

[0061] When the current sampling signal detected by the single chip microcomputer changes, the input current of the smart energy meter is calibrated according to the relationship between the value of r3 calculated currently, the current sampling signal of the smart energy meter and the current input signal (Formula 4).

[0062] When the sampling resistor drifts due to environmental changes, causing the accuracy of the electricity meter to deteriorate, the smart electricity meter can recalibrate the accuracy of the electricity meter online by correcting the resistance ratio or resistance value, without the need to remove the meter from the site and return it to the factory for recalibration, effectively improving the error accuracy stability and reducing maintenance costs.

[0063] When the above method is used for calibration, the accuracy of the recalibrated input voltage and input current mainly depends on the accuracy of the voltage regulator VCC, the accuracy of the ADC sampling channel Detect of the microcontroller, the design of resistors R5 and R6 in different situations, and the accuracy of the standard resistor. Therefore, the above voltage deviation and current deviation self-calibration method is used to effectively transform the requirements for the accuracy of the sampling resistor into the accuracy requirements for the voltage regulator VCC, the ADC sampling channel of the microcontroller, and the standard resistor, effectively improving the error accuracy stability and reducing the cost of calibration maintenance.

[0064] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A deviation self-calibration method, the method is implemented based on a deviation detection circuit, characterized in that: The deviation detection circuit includes a voltage-stabilized power supply VCC and a resistor string R5 and a resistor string R6 for online calibration of an input voltage or an input current of an intelligent electric energy meter; a first end of the resistor string R5 is connected to the voltage-stabilized power supply VCC, a second end of the resistor string R5 is connected to a first end of the resistor string R6, the second end of the resistor string R5 and the first end of the resistor string R6 are both connected to an ADC sampling channel of a single-chip microcomputer, the deviation detection circuit is connected to a circuit of the intelligent electric energy meter through the ADC sampling channel of the single-chip microcomputer, and the sampling circuit of the electric energy meter includes a voltage sampling circuit and a current sampling circuit; the relationship between the voltage sampling signal of the electric energy meter and the voltage input signal is: V P =UA*RA8 / (RA1+RA2+RA3+RA4+RA5+RA6+RA7+RA8), the relationship between the current sampling signal and the current input signal of the energy meter is: IP-I N =IA / N*(R1+R2); where V P is the voltage value detected by the internal sampling circuit of the energy meter, UA is the voltage value of the external input of the energy meter, RA1~RA7 use the same resistor, R1 and R2 use the same resistor, I P -I N is the current sampling signal of the electric energy meter, IA is the current value of the external input of the electric energy meter, and N is the transformer ratio; the method includes: After the first calibration, the single chip microcomputer detects the voltage value of the sampling channel at a certain interval, and calculates the resistance ratio of the resistors constituting the resistor string R5 and R6 after each detection; When the sampling signal detected by the single chip microcomputer changes, the input voltage and input current of the calibrated smart energy meter are automatically recalculated according to the resistance ratio corresponding to the sampling signal detected by the current deviation detection circuit, the relationship between the voltage sampling signal and the voltage input signal of the smart energy meter, and the relationship between the current sampling signal and the current input signal of the smart energy meter, so as to realize the online calibration of the accuracy of the smart energy meter; When the deviation detection circuit is used for voltage deviation detection, the resistor string R5 is formed by connecting a plurality of resistors with the same resistance value of r1 in series or in parallel, and the resistance value of the resistor R5 is recorded as m*r1, and the specifications and models of the resistors constituting the resistor string R5 are the same as those of RA1 to RA7, and the resistor string R6 is formed by connecting a plurality of resistors with the same resistance value of r2 in series or in parallel, and the resistance value of the resistor string R6 is recorded as n*r2, and the specifications and models of the resistors constituting the resistor string R6 are the same as those of RA8; When performing voltage deviation self-calibration, after the first calibration, the microcontroller detects the voltage value Vdetect of the sampling channel at a certain interval and calculates the voltage value Vdetect after each detection. Calculate the value of r1 / r2; when the sampling signal detected by the single chip microcomputer changes, calibrate the input voltage of the electric energy meter according to the currently calculated value of r1 / r2, the relationship between the voltage sampling signal of the electric energy meter and the voltage input signal; wherein the values ​​of m and n are adjusted according to the range of the sampling voltage of the single chip microcomputer, the combination form of the resistor with the resistance value of r1, and the combination form of the resistor with the resistance value of r2; When the deviation detection circuit is used for current deviation detection, the resistor string R5 is formed by a plurality of resistors with the same resistance value of r3 connected in series or in parallel, and the resistance value of the resistor string R5 is recorded as k*r3, the resistor specification model of the resistor string R5 is the same as R1 and R2, the resistor string R6 is formed by a single resistor, the resistance value of R6 is R, and the accuracy and stability of the resistor string R6 are higher than the resistance of the resistor string R5; wherein, the value of k is adjusted according to the range of the sampling voltage of the single chip computer and the combination form of the resistor with the resistance value of r3; When performing current deviation self-calibration, after the first calibration, the microcontroller detects the voltage value Vdetect of the sampling channel at a certain interval and calculates the voltage value Vdetect according to the current deviation after each detection. Calculate the value of r3; when the current sampling signal detected by the single chip microcomputer changes, calibrate the input current of the electric energy meter according to the relationship between the currently calculated value of r3, the current sampling signal of the electric energy meter and the current input signal.

2. The method according to claim 1, characterized in that A second end of the resistor string R6 is grounded.

3. The method according to claim 1, characterized in that The number of resistors constituting the resistor string R5 and R6 and the connection method of the resistors are determined according to whether the deviation detection circuit is used to detect voltage deviation or current deviation and the voltage sampling range of the single chip microcomputer.

4. A new type of smart energy meter, which can calibrate the input voltage and input current sampled by the smart energy meter online, is characterized in that: The novel intelligent electric energy meter implements the steps of a deviation self-calibration method as described in any one of claims 1-3.

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