Temperature drift correction method and model building method for current transformer

Abstract

The present invention provides a method for correcting the temperature drift of a current transformer and a method for building a model, by presetting n primary currents and measuring multiple sampling signals at sampling points and the temperature of the reference component corresponding to each sampling signal during the period when the temperature of the reference component rises from the initial temperature to the stable temperature under each primary current. i =f i (t‑T), and then all the sampled signals X i When t=T is corrected, the corrected sampling signal Y is obtained. i Among them, t is the temperature of the reference component, and T is the preset temperature of the reference component. Finally, according to the corrected sampling signal Y i And the transfer function of the measurement circuit calculates the corrected secondary current value Q. Therefore, the present invention obtains the corrected secondary current by establishing a mathematical model of the temperature of the reference component and the corrected sampling signal, which can reduce the influence of temperature drift on secondary current detection, improve accuracy, and enhance product performance.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring instruments, and in particular to a temperature drift correction method and a model building method for a current transformer. Background Art

[0002] At present, current transformers in automotive battery management systems are widely used due to their large measurement range and high measurement accuracy. However, temperature drift has a great impact on their accuracy. Therefore, how to obtain a measurement accuracy of 1% or even 0.5% within the full range and temperature has always been a difficult point in current transformer measurement.

[0003] The current transformer has a secondary coil. Usually, its primary current is relatively large (for example, more than 500A), but its secondary current is relatively small. It is necessary to amplify its secondary current for accurate measurement. Therefore, when measuring the secondary current, a measurement circuit is connected to the secondary coil end of the current transformer. However, some components such as sampling resistors in the measurement circuit have the characteristics of drifting with temperature, which will cause more serious measurement value deviation. At present, the more common practice is to lower the accuracy standard of the current transformer at high and low temperatures, so the existing secondary current detection scheme cannot obtain high measurement accuracy at high and low temperatures.

[0004] Therefore, it is necessary to establish a temperature drift correction model for a current transformer to solve the problem of low measurement accuracy caused by the temperature drift of various components in the measurement circuit when detecting the secondary current of the current transformer. Summary of the invention

[0005] The object of the present invention is to provide a temperature drift correction method and a model building method for a current transformer, so as to solve the problem of low measurement accuracy of the current transformer caused by the influence of temperature drift.

[0006] In order to solve the above technical problems, the present invention provides a method for constructing a temperature drift correction model of a current transformer, comprising:

[0007] Step 1: Connect the secondary coil terminal of the current transformer to a measurement circuit, and select a reference component and a sampling point in the measurement circuit;

[0008] Step 2: Fix the ambient temperature and set the primary currents I1, I2, I3, ..., I of the current transformer n , n is a positive integer;

[0009] Step 3: measuring, under each of the primary currents, a plurality of sampling signals at the sampling points and the temperature of the reference component corresponding to each of the sampling signals during a period in which the temperature of the reference component rises from an initial temperature to a stable temperature;

[0010] Step 4: Calculate the temperature when the primary current is I according to all the sampling signals and the temperature of the reference components obtained in step 3. i When X i =f i (tT) is the fitting parameter; where X i is the sampling signal, f i (tT) is the fitted sampling signal, t is the temperature of the reference component, T is the preset temperature of the reference component, 1≤i≤n, i is a positive integer;

[0011] Step 5: According to X i =f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i .

[0012] Optionally, in the method for constructing a temperature drift correction model of a current transformer, in step 4,

[0013]

[0014] Among them, a ij , a′ ij 、b i and b′ i is the proportionality coefficient, 1≤j≤m, and m and j are both positive integers.

[0015] Optionally, in the method for constructing a temperature drift correction model of a current transformer, it is characterized in that: but:

[0016]

[0017] Among them, K j and K′ j are the fitting parameters.

[0018] Optionally, in the method for constructing a temperature drift correction model for a current transformer, it is characterized in that when T=0°C, t=T=0, Y i =f i (0) = b i ; When T≠0℃, t=T, Y i =f i (0) = b′ i .

[0019] Optionally, in the method for constructing a temperature drift correction model of a current transformer, in step three, during the period when the temperature of the reference component rises from an initial temperature to a stable value, the sampling signal changes as the temperature of the reference component increases.

[0020] Optionally, in the method for constructing a temperature drift correction model of the current transformer, the measurement circuit includes a sampling resistor and an amplifier circuit; the secondary current flowing out of the secondary coil terminal of the current transformer passes through the sampling resistor, flows through the amplifier circuit, and is amplified by the amplifier circuit and then output; wherein the reference element is arranged in the amplifier circuit.

[0021] Optionally, in the method for constructing a temperature drift correction model of a current transformer, in step three, the sampling signal is a voltage value at the sampling resistor end.

[0022] Optionally, in the method for constructing a temperature drift correction model of a current transformer, the method for constructing a temperature drift correction model of a current transformer further includes: selecting multiple ambient temperatures, and executing steps two to three respectively at each ambient temperature.

[0023] Based on the same inventive concept, the present invention also includes a temperature drift correction method for a current transformer, comprising:

[0024] Get X i =f i Fitting parameters in (tT);

[0025] According to X i =f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i ; Wherein, 1≤i≤n, i and n are positive integers;

[0026] According to the modified sampling signal Y i And the transfer function of the measurement circuit calculates the corrected secondary current value Q.

[0027] Optionally, in the temperature drift correction method of the current transformer, when the primary current is I i hour,

[0028]

[0029] Then, when T = 0 ° C, t = T = 0, Y i =f i (0) = b i ;

[0030] When T≠0℃, t=T, Y i =f i (0) = b′ i ;

[0031] Among them, K j and K′ jis the fitting parameter; b i and b′ i is the proportionality coefficient, 1≤j≤m, and m and j are both positive integers.

[0032] In summary, the present invention provides a method for correcting the temperature drift of a current transformer and a method for constructing a model, wherein the method for constructing the temperature drift correction model of the current transformer presets n primary currents, and measures the temperature of the reference component corresponding to each sampling signal and the multiple sampling signals of the sampling points during the period when the temperature of the reference component rises from the initial temperature to the stable temperature under each primary current. Thus, the fitting sampling signal X i =f i (tT), and then all the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i =f i (tT). Wherein, t is the temperature of the reference component, and T is the preset temperature of the reference component. Finally, according to the corrected sampling signal Y i And the transfer function of the measurement circuit calculates the corrected secondary current value Q. Therefore, the present invention obtains the corrected secondary current by establishing a mathematical model of the temperature of the reference component and the corrected sampling signal, which can reduce the influence of temperature drift on secondary current detection, improve accuracy, and enhance product performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of a method for constructing a temperature drift correction model of a current transformer in this embodiment;

[0034] Figure 2 is a curve diagram showing the relationship between the sampling signal and the temperature change of the microcontroller unit when the primary current is 550A in this embodiment;

[0035] Figure 3 is a fourth-order fitting curve diagram of the sampling signal and the temperature of the microcontroller unit when the primary current is 550A in this embodiment;

[0036] Figure 4 is a fourth-order fitting curve diagram of the sampling signal and the temperature of the microcontroller unit when the primary current is -550A in this embodiment;

[0037] Figure 5 is a first-order fitting curve diagram of the sampling signal and the temperature of the microcontroller unit when the primary current is 550A in this embodiment;

[0038] Figure 6 is a first-order fitting curve diagram of the sampling signal and the temperature of the microcontroller unit when the primary current is -550A in this embodiment;

[0039] Figure 7 is a graph showing the relationship between the sampling signal before and after correction and the temperature of the microcontroller unit when the primary current is 550A in this embodiment;

[0040] Figure 8 It is a curve diagram of the relationship between the sampling signal before and after correction and the temperature of the microcontroller unit when the primary current is -550A in this embodiment. DETAILED DESCRIPTION

[0041] The following is a further detailed description of a temperature drift correction method and a model construction method for a current transformer proposed by the present invention in combination with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the accompanying drawings is often a part of the actual structure. In particular, the emphasis that each drawing needs to show is different, and sometimes different proportions are used.

[0042] In order to solve the above technical problems, this embodiment provides a method for constructing a temperature drift correction model of a current transformer, please refer to Figure 1 , the method for constructing a temperature drift correction model of a current transformer includes:

[0043] Step 1 S10: Connect the secondary coil terminal of the current transformer to a measurement circuit, and select a reference component and a sampling point in the measurement circuit.

[0044] Step 2 S20: Fix the ambient temperature and set the primary currents I1, I2, I3, ..., I of the current transformer. n , n is a positive integer.

[0045] Step three S30: measuring the temperature of the reference component corresponding to each sampling signal and the plurality of sampling signals at the sampling points during a period when the temperature of the reference component rises from an initial temperature to a stable temperature under each primary current.

[0046] Step 4 S40: Calculate the temperature when the primary current is I according to all the sampling signals and the temperature of the reference components obtained in step 3. i When X i =f i (tT) is the fitting parameter; where X i is the sampling signal, f i (tT) is the fitted sampling signal, t is the temperature of the reference component, T is the preset temperature of the reference component, 1≤i≤n, and i is a positive integer.

[0047] Step 5 S50: According to X i=f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i .

[0048] The following is combined with Figure 2-8 , the method for constructing the temperature drift correction model of the current transformer is described in detail:

[0049] Step 1 S10: Connect the secondary coil terminal of the current transformer to a measurement circuit, and select a reference component and a sampling point in the measurement circuit.

[0050] In the automotive battery management system, the secondary current of the current transformer is relatively small due to the influence of the measurement range, so a measurement circuit is connected to the secondary coil terminal to assist in the measurement. The measurement circuit includes a sampling resistor and an amplifier circuit. After the secondary current passes through the sampling resistor, it flows through the amplifier circuit and is amplified by the amplifier circuit before being output, so that a more accurate secondary current can be obtained.

[0051] However, the measurement circuit includes many kinds of electronic components. Each of the electronic components has the characteristic of drifting with temperature. The influence of temperature drift will cause a large error in measuring the secondary current. Therefore, in order to obtain the characteristics of each electronic component changing with temperature, the present embodiment selects multiple electronic components for thermocouple testing, and obtains the temperature relationship of each electronic component under various working conditions, and finds that the temperature of each electronic component remains basically consistent after stabilization. Therefore, in order to reduce costs and simplify the temperature drift correction model, the present embodiment selects a reference component for measurement to characterize other electronic components in the measurement circuit. Preferably, the reference component can be selected as a microcontroller unit, and a temperature sensor is integrated inside the microcontroller unit. Selecting the microcontroller unit as a feature point can also save the cost of a temperature sensor. At the same time, the sampling point is selected as the connection between the sampling resistor and the amplifier circuit, and the voltage value at the end of the sampling resistor is used as the sampling signal.

[0052] Step 2 S20: Fix the ambient temperature and set the primary currents I1, I2, I3, ..., I of the current transformer. n , n is a positive integer.

[0053] It is found through experiments that the temperature of the microcontroller unit changes with the change of the primary current and the working time, and when the primary current is constant, the temperature of the microcontroller unit tends to a stable value as the working time increases, and the sampling signal changes as the temperature of the microcontroller unit increases. Figure 2 As shown, Figure 2 This is the relationship curve between the sampling signal and the temperature change of the microcontroller unit when the primary current is 550A. Figure 2In the process, as the working time increases, the temperature of the microcontroller unit tends to its stable value of 120 degrees Celsius. In addition, the ambient temperature is also a variable in the test process, but because the time for controlling the ambient temperature is longer and the time for controlling the current is shorter, this embodiment adopts the method of first selecting multiple primary currents I1, I2, I3...I under the condition of fixed ambient temperature. n The ambient temperature may be selected from the conventional working environment of the automotive battery management system, such as -40°C, -15°C, 10°C, 35°C, 60°C and 85°C.

[0054] Step 3 S30: Measure the multiple sampling signals of the sampling points and the temperature of the reference component corresponding to each sampling signal during the period when the temperature of the reference component rises from the initial temperature to the stable temperature under each primary current. For example, when the primary current connected is I1, as the working time increases, the temperature of the microcontroller unit gradually rises. During the period when it rises to its stable state, obtain multiple sampling signals X1, X2, X3... and obtain the temperature t1 of the reference component corresponding to the sampling signal X1; the temperature t2 of the reference component corresponding to the sampling signal X2; the temperature t3 of the reference component corresponding to the sampling signal X3... until the following is obtained. Figure 2 The relationship diagram shown is the temperature t of the microcontroller unit and the sampling signal X when the primary current is I1. i relationship diagram.

[0055] Step 4 S40: All the sampled signals X obtained in step 3 are i and the temperature t of the reference component, calculate the value when the primary current is I i When X i =f i (tT) is the fitting parameter; where X i is the sampling signal, f i (tT) is the fitted sampling signal, t is the temperature of the reference component, 1≤i≤n, and i is a positive integer.

[0056] in,

[0057]

[0058] And a ij , a′ ij 、b i and b′ i is the proportionality coefficient, 1≤j≤m, and m and j are both positive integers.

[0059] From the above, we can know that when T=0℃:

[0060] When the primary current is I1, X1 = f1(t) = a11 t+a 12 t 2 +a 13 t 3 +……+a 1m t m +b1;

[0061] When the primary current is I2, X2 = f2(t) = a 21 t+a 22 t 2 +a 23 t 3 +……+a 2m t m +b2;

[0062] …

[0063] When the primary current is I n When X n =f n (t) = a n1 t+a n2 t 2 +a n3 t 3 +……+a nm t m +b n .

[0064] When T≠0℃:

[0065] When the primary current is I1, X1 = f1 (tT) = a' 11 (tT)+a′ 12 (tT) 2 +a′ 13 (tT) 3 +……+a′ 1m (tT) m +b′1;

[0066] When the primary current is I2, X2 = f2 (tT) = a' 21 (tT)+a′ 22 (tT) 2 +a′ 23 (tT) 3 +……+a′ 2m (tT) m +b′2;

[0067] …

[0068] When the primary current is I n When X n =f2(tT)=a′ n1 (tT)+a′n2 (tT) 2 +a′ n3 (tT) 3 +……+a′ nm (tT) m +b′ n .

[0069] Further, take but:

[0070]

[0071] Among them, K j and K′ j are the fitting parameters.

[0072] Therefore, when T = 0°C: When T≠0℃:

[0073] K1, K2, K3, ..., K m and K′1, K′2, K′3, ..., K′ m are the fitting parameters.

[0074] In summary, X i =f i (tT) is an m-order equation, which can be a first-order equation, a second-order equation, a third-order equation, a fourth-order equation or a fifth-order equation, etc.

[0075] For example, when X i =f i When (tT) is a fourth-order equation, m = 4, then: when the primary current is I i hour,

[0076]

[0077] like Figure 3 and 4 As shown, Figure 3 It is the fourth-order fitting curve of the sampling signal and the temperature of the microcontroller unit when the primary current is 550A. Figure 4 It is the fourth-order fitting curve of the sampling signal and the temperature of the microcontroller unit when the primary current is -550A.

[0078] In order to reduce the complexity of the model, this embodiment also provides a first-order equation model. When the primary current is I i hour,

[0079]

[0080] like Figure 5 and 6 As shown, Figure 5 It is the first-order fitting curve of the sampling signal and the temperature of the microcontroller unit when the primary current is 550A. Figure 6 This is the first-order fitting curve of the sampling signal and the temperature of the microcontroller unit when the primary current is -550A. It can be seen that compared with the fourth-order equation model, the fitting accuracy has a large deviation at high and low temperatures, but the fitting effect in the middle larger temperature range is good, and the error is not large. In the actual product, high and low temperatures rarely occur during the application process, which has little impact on the actual application and reduces the complexity a lot.

[0081] Step 5 S50: According to X i =f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i .

[0082] Furthermore, when T = 0 °C, t = T = 0, Y i =f i (0)=bi; when T≠0℃, t=T, Y i =f i (0) = b′ i .

[0083] like Figure 7 and 8 As shown, Figure 7 This is the relationship curve between the sampling signal before and after correction and the temperature of the micro control unit when the primary current is 550A. Figure 8 This is the relationship curve between the sampling signal before and after correction and the temperature of the micro control unit when the primary current is -550A.

[0084] Among them, in order to obtain more accurate fitting parameters, the method for constructing the temperature drift correction model of the current transformer can also include: selecting multiple ambient temperatures, such as -40°C, -15°C, 10°C, 35°C, 60°C and 85°C, changing the ambient temperature, and executing steps two to three.

[0085] Based on the same inventive concept, this embodiment also provides a method for correcting a temperature drift of a current transformer, comprising:

[0086] Obtain the temperature t of the reference component, that is, obtain the temperature value of the microcontroller unit. i =f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i =f i (tT); wherein 1≤i≤n, i and n are positive integers. Finally, according to the modified sampling signal Y iThe transfer function of the measuring circuit is used to calculate the corrected secondary current value Q(Y i ). Among them, Q(Y i ) is affected by the design of the current transformer and the design of the measuring circuit. It can usually be derived from a specific design schematic, but when it cannot be derived or the accuracy is not up to standard, it can be obtained through calibration.

[0087] The present embodiment provides a method for correcting the temperature drift of a current transformer and a method for building a model, by presetting n primary currents and measuring the temperature of the reference component corresponding to each sampling signal and the multiple sampling signals of the sampling point during the period when the temperature of the reference component rises from the initial temperature to the stable temperature under each primary current. Thus, the fitting sampling signal X is obtained. i =f i (tT), and then all the sampled signals X i When t=T is corrected, the corrected sampling signal Y is obtained. i =f i (tT). Wherein, t is the temperature of the reference component, and T is the preset temperature of the reference component. Finally, according to the corrected sampling signal Y i And the transfer function of the measurement circuit calculates the corrected secondary current value Q. Therefore, the present invention obtains the corrected secondary current by establishing a mathematical model of the temperature of the reference component and the corrected sampling signal, which can reduce the influence of temperature drift on secondary current detection, improve accuracy, and enhance product performance.

[0088] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for constructing a temperature drift correction model for a current transformer, characterized in that: The method for constructing a temperature drift correction model of a current transformer comprises: Step 1: Connect the secondary coil terminal of the current transformer to a measurement circuit, and select a reference component and a sampling point in the measurement circuit; Step 2: Fix the ambient temperature and set the primary currents I1, I2, I3, ..., I of the current transformer n , n is a positive integer; Step 3: measuring, under each of the primary currents, a plurality of sampling signals at the sampling points and the temperature of the reference component corresponding to each of the sampling signals during a period in which the temperature of the reference component rises from an initial temperature to a stable temperature; Step 4: Calculate the temperature when the primary current is I according to all the sampling signals and the temperature of the reference components obtained in step 3. i When X i =f i Fitting parameters in (tT); Among them, X i is the sampling signal, f i (tT) is the fitted sampling signal, t is the temperature of the reference component, T is the preset temperature of the reference component, 1≤i≤n, i is a positive integer; Step 5: According to X i =f i (tT) All the sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i .

2. The method for constructing a temperature drift correction model of a current transformer according to claim 1, characterized in that: In the step 4, Among them, a ij , a′ ij 、b i and b′ i is the proportionality coefficient, 1≤j≤m, and m and j are both positive integers.

3. The method for constructing a temperature drift correction model of a current transformer according to claim 2, characterized in that: but: Among them, K j and K′ j are the fitting parameters.

4. The method for constructing a temperature drift correction model of a current transformer according to claim 3, characterized in that: When T=0℃, t=T=0, Y i =f i (0) = b i ; When T≠0℃, t=T, Y i =f i (0) = b′ i .

5. The method for constructing a temperature drift correction model of a current transformer according to claim 1, characterized in that: In the step three, during the period when the temperature of the reference component rises from an initial temperature to a stable value, the sampling signal changes as the temperature of the reference component increases.

6. The method for constructing a temperature drift correction model of a current transformer according to claim 1, characterized in that: The measuring circuit comprises a sampling resistor and an amplifier circuit; the secondary current flowing out of the secondary coil terminal of the current mutual inductance passes through the sampling resistor, flows through the amplifier circuit, and is amplified by the amplifier circuit before being output; wherein the reference component is arranged in the amplifier circuit.

7. The method for constructing a temperature drift correction model for a current transformer according to claim 6, characterized in that: In the step three, the sampling signal is the voltage value at the end of the sampling resistor.

8. The method for constructing a temperature drift correction model of a current transformer according to claim 1, characterized in that: The method for constructing a temperature drift correction model for a current transformer also includes: selecting multiple ambient temperatures, and performing steps 2 to 3 respectively at each ambient temperature.

9. A method for correcting temperature drift of a current transformer, characterized in that: The temperature drift correction model of the current transformer is established using the method for constructing the temperature drift correction model of the current transformer as claimed in any one of claims 1 to 8, and the temperature drift correction method of the current transformer comprises: Get X i =f i Fitting parameters in (tT); All sampled signals X i Correct to t = T to obtain the corrected sampling signal Y i ; Wherein, 1≤i≤n, i and n are positive integers; According to the modified sampling signal Y i And the transfer function of the measurement circuit calculates the corrected secondary current value Q.

10. The temperature drift correction method of the current transformer according to claim 9, characterized in that: When the primary current is I i hour, Then, when T = 0 ° C, t = T = 0, Y i =f i (0) = b i ; When T≠0℃, t=T, Y i =f i (0) = b′ i ; Among them, K j and K′ j is the fitting parameter; b i and b′ i is the proportionality coefficient, 1≤j≤m, and m and j are both positive integers.

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