Full-temperature automatic calibration and compensation method for electric energy meter

Abstract

The invention provides a full-temperature automatic calibration and compensation method for an electric energy meter, which belongs to the technical field of electric energy meter embedding, and is characterized in that a multi-segment and non-uniform temperature segment point method is adopted, an instruction is sent to the electric energy meter through an upper computer, and the electric energy meter can be automatically calibrated and compensated. And then the target temperature of the high-low temperature box is set, and full-temperature calibration is carried out. By adopting the design of multi-section and non-uniform temperature segmentation points, the method can adapt to various temperature-error curves. The method is simple to operate, only an instruction needs to be sent to the electric energy meter through the upper computer, then the target temperature of the high-temperature and low-temperature box is set, full-temperature calibration can be automatically completed, and frequent command interaction with the electric energy meter or frequent manual adjustment of the temperature of the high-temperature and low-temperature box is not needed.

Description

Technical Field

[0001] The invention relates to the technical field of embedded electric energy meters, and in particular provides a full-temperature automatic calibration and compensation method for electric energy meters. Background Art

[0002] Temperature drift is an inherent characteristic of electronic devices. When the electric energy meter composed of electronic devices is at different temperatures, the measurement accuracy will change. The electric energy meter will be calibrated before leaving the factory, but the error correction is often only performed at the ambient temperature at that time. After being installed on site, when the ambient temperature changes greatly, it may introduce a large measurement error.

[0003] The temperature drift of electronic devices is a hardware characteristic, and it is difficult to eliminate it in the hardware circuit. If devices with low temperature drift are used, the cost will also increase. Therefore, at the software level, it is a common practice to eliminate the measurement error caused by temperature through full temperature calibration and compensation.

[0004] Patent No.: CN201510593377.7 A method for improving the measurement accuracy of smart meters provides a method of dividing the range from -40 degrees to 70 degrees into sections of 5 degrees and then linearly processing each section to compensate for the voltage and current values; "A method and device for compensating for temperature-affected errors in electric energy meters" (Patent No.: CN201810311996.6) provides a method for temperature compensation by fitting a cubic curve based on the error data of each temperature point of an existing electric energy meter;

[0005] Patent number: CN201810510171.7 The method for optimizing the measurement accuracy of electric energy meters based on temperature compensation provides a method for temperature compensation by first constructing the relationship between the heat generation and error of each component in the electric energy meter, and then applying it to the actual operating electric energy meter.

[0006] All of the above are achieved by fitting a fixed curve first and then placing it in the electricity meter program for temperature compensation. However, even if the electricity meters with the same hardware structure have the same error change trend with temperature, the error values ​​at different temperatures are different.

[0007] Patent No.: CN201510220506.8 A temperature segmented calibration and metering method for an electric energy metering device provides a method for temperature calibration on an electric energy meter, but it only contains two temperature calibration points. The curve of the electric energy meter error changing with temperature is mostly not linear, so it is difficult to ensure the calibration accuracy;

[0008] Patent No.: CN201510248778.9 The temperature compensation method for single-phase electric energy meters provides an error correction at a temperature interval of 5 degrees at 1.0 power factor and 0.5L power factor. This fixed-interval temperature segmentation method may lead to a large measurement error at the inflection point of the temperature-error curve, while the non-uniform temperature segmentation calibration can better adapt to various types of temperature error curves and more effectively reduce the measurement error caused by temperature changes. Summary of the invention

[0009] The measured value of the energy meter comes from the real-time power value of the energy meter, and the power value is calculated by the metering chip through the input voltage and current signals. When calculating power, the metering chip will introduce the information of the calibration register to correct the calculation result. There are two main registers that affect power in the calibration register: one is the power phase gain register RegP-phase, and the other is the power effective value gain register RegP-value. During normal temperature calibration, RegP-phase is generally adjusted to calibrate the power value. During full temperature calibration and compensation, it is necessary to change the value of the RegP-value register in real time based on the normal temperature calibration and the current temperature to eliminate the metering error introduced by temperature changes.

[0010] Therefore, the present invention provides a full-temperature automatic calibration and compensation method for electric energy meters, so that each electric energy meter has a temperature-error line graph suitable for itself after temperature calibration. During calibration, it can support the use of a flexible setting of temperature calibration segmentation points, and select multiple target temperature calibration points in a targeted manner within the full operating temperature range of the electric energy meter, focusing on setting more target temperature calibration points near the inflection point of the temperature-error curve and in places where the temperature changes faster, so that it can ensure the metering accuracy within the full operating temperature range of the electric energy meter. And realize full automatic operation, so that the electric energy meter can automatically perform full temperature calibration and compensation functions, so that the full temperature calibration and compensation of the electric energy meter can be carried out in batches.

[0011] The present invention provides a full-temperature automatic calibration and compensation method for an electric energy meter. The method adopts a multi-segment, non-uniform temperature segmentation point method to adapt to various temperature-error curves, sends a command to the electric energy meter through a host computer, and then sets the target temperature of a high and low temperature box to perform full-temperature calibration.

[0012] Furthermore, the method comprises the following steps:

[0013] Step 1: Place the energy meter that has been calibrated at room temperature into a high and low temperature box, place a standard power source outside the high and low temperature box to provide a stable voltage and current input for the energy meter, and lead the maintenance 485 serial port line of the energy meter to the host computer outside the box;

[0014] Step 2: Considering that the electric energy meter generates heat during operation, the initial temperature of the high and low temperature box is adjusted to the minimum temperature Tmin-N degrees that the electric energy meter needs to reach, where N needs to be determined in combination with the specific situation of the temperature rise of the electric energy meter, and then the power source outputs the rated voltage Un, the rated current Ib, and the power factor of 1.0;

[0015] Step 3: Use the host computer software to issue a command to the electric energy meter through the maintenance serial port line of the electric energy meter to start full temperature calibration. The command contains {T[1], T[2], T[3], ..., T[n]}, which is a set of all target temperature calibration points, where T[1] = Tmin, T[n] = Tmax, and Tmin and Tmax are the minimum and maximum operating temperatures that the electric energy meter needs to reach, respectively;

[0016] Step 4: After receiving the command, the electric energy meter starts to automatically perform full temperature calibration; then the high and low temperature box is manually set to start heating, and the target temperature is Tmax;

[0017] Step 5: After the full temperature calibration is started, the electric energy meter starts to periodically read the current temperature inside the meter and collect errors;

[0018] When the electric energy meter passes through each calibration temperature point, it is necessary to calculate and record the power error value Err = (Pcur-Pstd) / Pstd at that point.

[0019] Where Pcur is the power value of the electric energy meter at the current temperature;

[0020] And the error collection state of the temperature point is set from not collected to collected;

[0021] Finally, the error values ​​corresponding to all target temperature calibration points are obtained {Err[1], Err[2], Err[3], …, Err[n]};

[0022] Step 6: Due to the fact that the program has a detection cycle for the current temperature, the current temperature Tcur of the electric energy meter may never be exactly equal to a value in {T[1], T[2], T[3], ..., T[n]}, so an algorithm needs to be introduced to ensure the calculation of the power error at each temperature point;

[0023] Step 7: When the error values ​​corresponding to all the temperature points to be calibrated are collected and the current temperature value Tcur is greater than Tmax, the electric energy meter automatically stores the errors {Err[1], Err[2], Err[3], ..., Err[n]} corresponding to each temperature point into the Flash, completes the full temperature calibration, and automatically turns on the full temperature compensation function;

[0024] Step 8: The electric energy meter uses the error values ​​corresponding to each temperature point stored in the Flash in combination with the compensation algorithm to modify the value of the power effective value gain register RegP-value in the metering chip in real time, thereby achieving the purpose of dynamically adjusting the metering error as the temperature changes.

[0025] Furthermore, in step 2:

[0026] The electric energy meter does not obtain the real-time output power value from the power source, but relies on the stable output of the power source to keep the above output unchanged during the entire full temperature calibration period, and the output power is always the rated power value Pstd = Un*Ib*1.0;

[0027] Furthermore, in step 3, for temperature regions where the error changes rapidly with temperature, such as the inflection point of the curve, target temperature calibration points may be appropriately added to ensure that the final measurement accuracy after temperature compensation meets the standard.

[0028] Furthermore, in step 3,

[0029] Since the error trends of the electric energy meters of the same scheme are consistent with those of the temperature, the temperature region and inflection point where the error changes faster with temperature can be obtained from theoretical analysis and test data.

[0030] Furthermore, in step 6, the specific steps of the algorithm calculation are as follows:

[0031] (1) Determine whether the current temperature Tcur is within the range of ±1°C of any temperature point to be calibrated Ttarget. If not, no error collection is performed for Tcur.

[0032] (2) If it is between, determine whether the error value has been collected at the Ttarget point. If not, directly collect the error;

[0033] (3) If error collection has been performed at point Ttarget, then continue to determine whether Tcur is closer to Ttarget than the temperature Tlast at the last error calculation at point Ttarget. If so, error collection is performed; otherwise, error collection is not performed for Tcur.

[0034] (4) Each time the error is collected, the error value Err corresponding to the Ttarget temperature point is calculated again according to the current power value, and Tlast=Tcur is updated.

[0035] Furthermore, in step 8, the specific algorithm for dynamically adjusting the measurement error is as follows:

[0036] If the current temperature Tcur is between any two adjacent temperature points [TL, TH) in {T[1], T[2], T[3], …, T[n]}, use the error values ​​ErrL and ErrH corresponding to TL and TH to put them into the Y-axis of the plane rectangular coordinate system, and put TL and TH into the X-axis, draw a straight line between the two points (TL, ErrL) and (TH, ErrH), and obtain the equation: {ErrCur=a*(Tcur-TL)+b, a=(ErrH-ErrL) / (TH-TL), b=ErrL}, and the error value ErrCur corresponding to the current temperature can be solved according to the equation.

[0037] Furthermore, in step 8, the specific algorithm for dynamically adjusting the measurement error is as follows:

[0038] If Tcur is less than T[1], then TL=T[1], TH=T[2], ErrL=Err[1], ErrH=Err[2], use the equation {ErrCur=a*(Tcur-TL)+b, a=(ErrH-ErrL) / (TH-TL), b=ErrL} to solve for ErrCur;

[0039] Furthermore, in step 8, the specific algorithm for dynamically adjusting the measurement error is as follows:

[0040] If Tcur is greater than or equal to T[n], then TL = T[n-1], TH = T[n], ErrL = Err[n-1], ErrH = Err[n], and use the equation {ErrCur = a*(Tcur-TL)+b, a = (ErrH-ErrL) / (TH-TL), b = ErrL} to solve for ErrCur;

[0041] Furthermore, the algorithm also includes:

[0042] The gain value is calculated by ErrCur: Gain = -ErrCur / (1+ErrCur);

[0043] The gain value Gain is converted according to the requirements of the power effective value gain register of the metering chip, and then filled into the register RegP-value.

[0044] Compared with the prior art, the full-temperature automatic calibration and compensation method for electric energy meters of the present invention has the following outstanding beneficial effects:

[0045] By adopting the design of multi-segment and non-uniform temperature segmentation points, it can adapt to various temperature-error curves. This method is simple to operate. It only needs to send a command to the electric energy meter through the host computer, and then set the target temperature of the high and low temperature box, and the full temperature calibration can be completed automatically. There is no need to frequently interact with the electric energy meter for commands, or frequently manually adjust the temperature of the high and low temperature box. After the full temperature calibration is completed, the electric energy meter automatically turns on the full temperature compensation function, which is very convenient. And the use of non-uniform segmentation can adapt to various temperature-error curves, and can more accurately compensate for the errors caused by temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a connection diagram of the calibration device of the present invention;

[0047] Figure 2 is a calibration flow chart of the method of the present invention;

[0048] Figure 3 is a schematic diagram of power error obtained after calibration of the present invention;

[0049] Figure 4 It is the compensation flow chart of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] A convenient full-temperature calibration and compensation method for electric energy meters. Taking the RN7326 cross-collection metering chip of Renergy Micro as an example, the operating temperature range of the electric energy meter is [-35℃, 80℃], the rated voltage is 220V, the rated current is 1.5A, and the three-phase power effective value gain registers are named RegPa-value, RegPb-value, and RegPc-value. The following are the specific implementation steps:

[0052] Step 1: Place the energy meter that has been calibrated at room temperature into a high and low temperature box, place a standard power source outside the high and low temperature box to provide a stable three-phase voltage and current input for the energy meter, and connect the maintenance 485 serial port line of the energy meter to the host computer outside the box. Figure 1 shown.

[0053] Step 2: Considering that the electric energy meter generates heat during operation, adjust the initial temperature of the high and low temperature box to Tmin-5 degrees, and then make the power source output 220V, 1.5A, 1.0 power factor and keep the above output unchanged during the entire full temperature calibration period.

[0054] Step 3: Use the host computer software to issue a command to the meter to start full temperature calibration through the meter's maintenance serial port line. The command contains all target temperature calibration points {-35℃, -20℃, 0℃, 20℃, 30℃, 40℃, 60℃, 70℃, 80℃}. In this example, the inflection point of the temperature-error curve of the meter appears near 30℃, so a 30℃ calibration point is added between 20℃ and 40℃. When the temperature is high, the error changes faster with temperature, so a 70℃ calibration point is added.

[0055] Step 4: After receiving the command, the energy meter automatically starts full temperature calibration. The flow chart of full temperature calibration is as follows: Figure 2 The high and low temperature boxes are manually set to start heating up, with the target temperature being 80°C.

[0056] Step 5: After the full temperature calibration is turned on, the electric energy meter starts to periodically read the current temperature inside the meter and collect errors. When the electric energy meter passes through each calibration temperature point, it is necessary to calculate and record the three-phase power error value ErrPa=(Pacur-330) / 330, ErrPb=(Pbcur-330) / 330, ErrPc=(Pccur-330) / 330, where Pacur, Pbcur, and Pccur are the ABC three-phase power values ​​at the current temperature, and 330W=220V*1.5A*1.0. And set the error collection status of the temperature point from not collected to collected.

[0057] Step 6: Due to the detection cycle of the current temperature in the program, the current temperature Tcur of the energy meter may never be exactly equal to a value in {-35℃, -20℃, 0℃, 20℃, 30℃, 40℃, 60℃, 70℃, 80℃}, so an algorithm needs to be introduced to ensure the calculation of the power error at each temperature point. Take the 0℃ target calibration point as an example:

[0058] (1) If the current temperature read in this acquisition cycle is -0.5°C and the current 0°C target calibration point is in the unacquired state, error acquisition is performed;

[0059] (2) In the next cycle, the current temperature is read as 0.1°C. The absolute value of the difference between 0.1°C and 0°C is 0.1. The absolute value of the difference between -0.5°C and 0°C in the last error collection is 0.5. Then, error collection is performed again, overwriting the error value obtained last time, and the temperature of the last error collection is updated to 0.1°C.

[0060] (3) In the next cycle, the current temperature is read as 0.7°C. Since it is farther from 0°C than the last temperature collected, which is 0.1°C, no error collection is performed.

[0061] (4) Therefore, the error at the final 0°C target calibration point is obtained at 0.1°C.

[0062] Step 7: After all the error values ​​corresponding to the temperature points to be calibrated are collected and the current temperature value Tcur is greater than 80°C, the energy meter automatically stores the errors corresponding to each temperature point in the Flash, completes the full temperature calibration, and automatically turns on the full temperature compensation function. The error of the three-phase power collected after the full temperature calibration changes with the temperature is as follows: Figure 3 shown.

[0063] Step 8: When the electric energy meter is performing full temperature compensation, the error values ​​corresponding to each temperature point stored in the Flash are used to modify the values ​​of the three-phase power effective value registers RegPa-value, RegPb-value, and RegPc-value in real time. The flow chart is as follows: Figure 4 As shown below, combined Figure 3 The data in the figure uses phase A power alone to illustrate the method of full temperature compensation:

[0064] (1) If the current temperature is 35.5°C, since it is between the target calibration points of 30°C and 40°C, the equation {ErrCur = a*(35.5-30)+b, a = (-0.000433-(-0.0000909)) / (40-30), b = -0.0000909} is listed, and ErrCur = -0.000279 is obtained;

[0065] (2) If the current temperature is -37°C, since it is lower than the minimum target calibration point -35°C, it is necessary to use the line segment of -35°C and -20°C as an extension line, and then calculate the error corresponding to -37°C. The equation {ErrCur = a*(-37--35)+b, a = (-0.001864--0.001992) / (-20--35), b = -0.001992} is listed, and ErrCur = -0.002 is obtained;

[0066] (3) If the current temperature is 85°C, since it is greater than the maximum target calibration point of 80°C, it is necessary to use the line segment of 70°C and 80°C as an extension line, and then calculate the error corresponding to 85°C. The equation {ErrCur = a*(85-70)+b, a = (-0.004207--0.002898) / (80-70), b = -0.002898} is listed, and ErrCur = -0.0048615 is obtained;

[0067] (4) Calculate the gain value through ErrCur: Gain = -ErrCur / (1+ErrCur). Taking 35.5°C as an example, Gain = 0.000279;

[0068] (5) The gain value Gain is converted according to the requirements of the chip power effective value gain register, and then filled into the register RegPa-value.

[0069] The conversion method corresponding to the RN7326 metering chip is:

[0070] If Gain is greater than or equal to 0, RegP-value = Gain*(2^15);

[0071] If Gain is less than 0, RegP-value = Gain*(2^15)+(2^16).

[0072] At this time, Gain is greater than 0, and RegPa-value=0.00186*(2^15), and the final register value is 0x9.

[0073] The embodiments described above are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A full-temperature automatic calibration and compensation method for an electric energy meter, characterized in that: The method adopts a multi-stage, non-uniform temperature segmentation point method, sends a command to the electric energy meter through the host computer, and then sets the target temperature of the high and low temperature box to perform full temperature calibration.

2. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 1, characterized in that: The method comprises the following steps: Step 1: Place the energy meter that has been calibrated at room temperature into a high and low temperature box, place a standard power source outside the high and low temperature box to provide a stable voltage and current input for the energy meter, and lead the maintenance 485 serial port line of the energy meter to the host computer outside the box; Step 2: Adjust the initial temperature of the high and low temperature box to the minimum temperature Tmin-N degrees that the electric energy meter needs to reach, and then make the power source output rated voltage Un, rated current Ib, and 1.0 power factor; Step 3: Use the host computer software to issue a command to the electric energy meter through the maintenance serial port line of the electric energy meter to start full temperature calibration. The command contains {T[1], T[2], T[3], ..., T[n]}, which is a set of all target temperature calibration points, where T[1] = Tmin, T[n] = Tmax, and Tmin and Tmax are the minimum and maximum operating temperatures that the electric energy meter needs to reach, respectively; Step 4: After receiving the command, the electric energy meter starts to automatically perform full temperature calibration; then the high and low temperature box is manually set to start heating, and the target temperature is Tmax; Step 5: After the full temperature calibration is started, the electric energy meter starts to periodically read the current temperature inside the meter and collect errors; When the energy meter passes through each calibration temperature point, the power error value at that point needs to be calculated and recorded: Err=(Pcur-Pstd) / Pstd, Where Pcur is the power value of the electric energy meter at the current temperature; And the error collection state of the temperature point is set from not collected to collected; Finally, the error values ​​corresponding to all target temperature calibration points are obtained {Err[1], Err[2], Err[3], …, Err[n]}; Step 6: Introduce an algorithm to ensure the calculation of the power error at each temperature point; Step 7: When the error values ​​corresponding to all the temperature points to be calibrated are collected and the current temperature value Tcur is greater than Tmax, the electric energy meter automatically stores the errors {Err[1], Err[2], Err[3], ..., Err[n]} corresponding to each temperature point into the Flash, completes the full temperature calibration, and automatically turns on the full temperature compensation function; Step 8: The electric energy meter uses the error values ​​corresponding to each temperature point stored in the Flash in combination with the compensation algorithm to modify the value of the power effective value gain register RegP-value in the metering chip in real time, thereby achieving the purpose of dynamically adjusting the metering error as the temperature changes.

3. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 2, characterized in that: In step 2: The electric energy meter relies on the stable output of the power source to keep the above output unchanged during the entire full temperature calibration period, and the output power is always the rated power value Pstd=Un*Ib*1.

0.

4. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 2, characterized in that: In step 3, for the temperature region where the error changes rapidly with temperature, target temperature calibration points are added to ensure that the final measurement accuracy after temperature compensation meets the standard.

5. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 2, characterized in that: In step 3, for the electric energy meters of the same solution, the trends of their errors changing with temperature are consistent, and the temperature region and inflection point where the error changes faster with temperature can be obtained from theoretical analysis and test data.

6. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 3, characterized in that: In step 6, the specific steps of the algorithm calculation are as follows: (1) Determine whether the current temperature Tcur is within the range of ±1°C of any temperature point to be calibrated Ttarget. If not, no error collection is performed for Tcur. (2) If it is between, determine whether the error value has been collected at the Ttarget point. If not, directly collect the error; (3) If error collection has been performed at point Ttarget, then continue to determine whether Tcur is closer to Ttarget than the temperature Tlast at the last error calculation at point Ttarget. If so, error collection is performed; otherwise, error collection is not performed for Tcur. (4) Each time the error is collected, the error value Err corresponding to the Ttarget temperature point is calculated again according to the current power value, and Tlast=Tcur is updated.

7. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 6, characterized in that: In step 8, the specific algorithm for dynamically adjusting the measurement error is as follows: If the current temperature Tcur is between any two adjacent temperature points [TL, TH) in {T[1], T[2], T[3], …, T[n]}, use the error values ​​ErrL and ErrH corresponding to TL and TH to put them into the Y-axis of the plane rectangular coordinate system, and put TL and TH into the X-axis, draw a straight line between the two points (TL, ErrL) and (TH, ErrH), and obtain the equation: {ErrCur=a*(Tcur-TL)+b, a=(ErrH-ErrL) / (TH-TL), b=ErrL}, and the error value ErrCur corresponding to the current temperature can be solved according to the equation.

8. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 6, characterized in that: In step 8, the specific algorithm for dynamically adjusting the measurement error is as follows: If Tcur is less than T[1], then TL=T[1], TH=T[2], ErrL=Err[1], ErrH=Err[2], and use the equation {ErrCur=a*(Tcur-TL)+b, a=(ErrH-ErrL) / (TH-TL), b=ErrL} to solve for ErrCur.

9. A full-temperature automatic calibration and compensation method for an electric energy meter according to claim 6, characterized in that: In step 8, the specific algorithm for dynamically adjusting the measurement error is as follows: If Tcur is greater than or equal to T[n], then TL=T[n-1], TH=T[n], ErrL=Err[n-1], ErrH=Err[n], and use the equation {ErrCur=a*(Tcur-TL)+b, a=(ErrH-ErrL) / (TH-TL), b=ErrL} to solve ErrCur.

10. A full-temperature automatic calibration and compensation method for an electric energy meter according to any one of claims 7 to 9, characterized in that: The algorithm also includes: The gain value is calculated by ErrCur: Gain = -ErrCur / (1+ErrCur); The gain value Gain is converted according to the requirements of the power effective value gain register of the metering chip, and then filled into the register RegP-value.

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