TMR electronic current transformer with temperature and linearity compensation and compensation method

Abstract

The invention discloses a TMR electronic current transformer with temperature and linearity compensation. The TMR electronic current transformer comprises a TMR sensing head and an acquisition device, the TMR sensing head comprises a TMR chip, a temperature chip, a corresponding power supply and a peripheral circuit; the acquisition device comprises an analog-to-digital converter, a processor, a memory, a corresponding power supply and a peripheral circuit; the TMR chip is used for sensing a measured current value and converting the measured current value into a voltage signal VTMR in an equal proportion mode, the temperature chip is used for sensing an environment temperature value and converting the environment temperature value into a voltage signal VTEMP in an equal proportion mode, and the voltage signal VTMR and the voltage signal VTEMP are both transmitted to the analog-digital converter. The analog-to-digital converter is used for converting the voltage signals VTMR and VTEMP into digital signals TMRAD and TEMPAD respectively; compensation parameters are pre-stored in the memory; and the processor is used for performing compensation calibration according to the digital signal TMRAD, the digital signal TEMPAD and the compensation parameter, and outputting data TMROUT after compensation calibration. On the other hand, the invention provides a compensation method of the TMR electronic current transformer, and the TMR electronic current transformer with temperature and linearity compensation is adopted.

Description

Technical Field

[0001] The present invention relates to the technical field of current transformers, and particularly to a TMR electronic current transformer with temperature and linearity compensation and a compensation method. Background Art

[0002] Current transformers are important devices for power metering and protection in power systems, and are divided into two categories: non-isolated and isolated. Among them, non-isolated current transformers generally adopt the shunt principle, which can measure AC and DC and broadband signals, but they are invasive measurements and will damage the original power system, so their use has certain limitations. Isolated current transformers are generally based on Rogowski coils and iron-core coils, which have disadvantages such as inability to measure DC quantities, easy saturation of the iron core under large currents, and large volume, and it is difficult to meet the measurement requirements of the new generation of intelligent power systems.

[0003] With the maturity and popularization of tunnel magnetoresistance (TMR) technology, electronic current transformers using TMR sensors have a series of advantages such as non-contact measurement, simultaneous AC and DC measurement, frequency up to the MHz level, small delay, large dynamic measurement range, low cost, high insulation level, and small volume, which have made TMR electronic current transformers widely promoted and applied in recent years. However, the accuracy of TMR electronic current transformers is limited by the characteristics of the TMR chip (11) itself. Currently, the existing TMR chips (11) have a nonlinearity of about 3% and a zero offset and sensitivity temperature coefficient of about 500 ppm / °C, and it is difficult to meet the high-precision measurement requirements of the power grid at 0.5 level or even 0.2 level over the full temperature range of -40°C to +70°C. Summary of the Invention

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A TMR electronic current transformer with temperature and linearity compensation, comprising a TMR sensing head and an acquisition device;

[0006] The TMR sensing head includes a TMR chip, a temperature chip, and corresponding power supplies and peripheral circuits;

[0007] The acquisition device includes an analog-to-digital converter, a processor, a memory, and corresponding power supplies and peripheral circuits;

[0008] The TMR chip is used to sense the value of the measured current and convert it into a voltage signal V_TMR in proportion, and the temperature chip is used to sense the ambient temperature value and convert it into a voltage signal V_TEMP in proportion. The voltage signals V_TMR and V_TEMP are both transmitted to the analog-to-digital converter;

[0009] The analog-to-digital converter is used to convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD respectively;

[0010] Compensation parameters are pre-stored in the memory;

[0011] The processor is configured to perform compensation calibration based on the digital signals TMR_AD, TEMP_AD and the compensation parameters, and output the compensated and calibrated data TMR_OUT.

[0012] Furthermore, the compensation parameters pre-stored in the memory include zero-point temperature compensation parameters, sensitivity temperature compensation parameters and linearity compensation parameters.

[0013] On the other hand, the present invention provides a compensation method for a TMR electronic current transformer, which uses the above-mentioned TMR electronic current transformer with temperature and linearity compensation, and includes the following steps:

[0014] S1. Collect the voltage signal V_TMR output by the TMR chip and the voltage signal V_TEMP output by the temperature chip;

[0015] S2. Respectively convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD through an analog-to-digital converter;

[0016] S3. Based on the digital signals TMR_AD and TEMP_AD, and the compensation parameters pre-stored in the memory, perform compensation calibration, and the process of compensation calibration specifically includes:

[0017] S3a. Adopt a zero-point temperature compensation algorithm to compensate for the zero-point offset of the TMR chip;

[0018] S3b. Adopt a sensitivity temperature compensation algorithm to compensate for the temperature offset of the ratio of the TMR chip sensing the measured current;

[0019] S3c. Adopt a linearity compensation algorithm to compensate for the non-linearity of the TMR chip;

[0020] S4. Output the compensated and calibrated data TMR_OUT.

[0021] Furthermore, in step S3a, compensation is performed according to the digital signals TMR_AD and TEMP_AD and the zero-point temperature compensation parameters pre-stored in the memory to reduce the zero-point offset of the TMR chip with temperature change. The TMR data after zero-point temperature compensation is represented by TMR_1.

[0022] Furthermore, in step S3a, when performing zero-point temperature compensation, subtract the TMR zero-point offset caused by temperature from TMR_AD, as shown in the following formula:

[0023] TMR_1 = TMR_AD - (a0 + a1 * TEMP_AD + a2 * TEMP_AD2 +a3*TEMP_AD 3 +a4*TEMP_AD 4 )

[0024] Among them, a0, a1, a2, a3, and a4 are zero-point temperature compensation parameters.

[0025] Furthermore, in step S3b, compensation is performed according to TEMP_AD, the TMR data TMR_1 after zero-point temperature compensation, and the sensitivity temperature compensation parameters pre-stored in the memory, so as to reduce the sensitivity offset of the TMR chip with temperature change. The TMR data after sensitivity temperature compensation is represented by TMR_2.

[0026] Furthermore, in step S3b, when performing sensitivity temperature compensation, multiply TMR_1 by the TMR sensitivity offset caused by temperature, as shown in the following formula:

[0027] TMR_2 = TMR_1 * (b0 + b1 * TEMP_AD + b2 * TEMP_AD 2 +b3 * TEMP_AD 3 +b4 * TEMP_AD 4 )

[0028] Among them, b0, b1, b2, b3, and b4 are sensitivity temperature compensation parameters.

[0029] Furthermore, in step S3c, compensation is performed according to the TMR data TMR_2 after sensitivity temperature compensation and the linearity compensation parameters pre-stored in the memory, so as to reduce the non-linearity of the TMR chip.

[0030] Furthermore, in step S3c, when performing linearity compensation, perform non-linearity fitting on TMR_2, as shown in the following formula:

[0031] TMR_OUT = c0 + c1 * TMR_2 + c2 * TMR_2 2

[0032] Among them, c0, c1, and c2 are linearity compensation parameters.

[0033] Furthermore, before step S1, there is also step S0: perform high-order fitting on the output value of the TMR chip and the standard value of the measured current to determine the compensation parameters stored in the memory.

[0034] Compared with the prior art, the TMR electronic current transformer with temperature and linearity compensation and the compensation method provided by the present invention perform non-contact measurement on the bus current of the power system based on a tunnel magnetoresistance (TMR) chip, realizing the conversion from analog quantity to digital quantity and software compensation calibration; the present invention retains the advantages of the TMR sensor itself such as non-contact, AC and DC co-measurement, wide frequency band, low delay, and wide dynamic measurement range, and improves the accuracy of the TMR chip itself through temperature and linearity compensation algorithms, realizing non-contact, AC and DC, wide frequency band, low delay, and high-precision measurement of the bus current of the power system. Brief Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the TMR electronic current transformer with temperature and linearity compensation provided by the present invention;

[0036] Figure 2 It is a schematic flow diagram of the TMR electronic current transformer and the compensation method provided by the present invention. Detailed Embodiments

[0037] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following further elaborates how the present invention is implemented in combination with specific embodiments.

[0038] In a specific embodiment, with reference to Figure 1 As shown, the present invention provides a TMR electronic current transformer with temperature and linearity compensation, including a TMR sensing head 1 and an acquisition device 2; the TMR sensing head 1 includes a TMR chip 11, a temperature chip 12, and corresponding power supplies and peripheral circuits; the acquisition device 2 includes an analog-to-digital converter 21, a processor 22, a memory 23, and corresponding power supplies and peripheral circuits; the TMR chip 11 is used to sense the measured current value and convert it into a voltage signal V_TMR in proportion, the temperature chip 12 is used to sense the ambient temperature value and convert it into a voltage signal V_TEMP in proportion, and both the voltage signals V_TMR and V_TEMP are transmitted to the analog-to-digital converter 21; the analog-to-digital converter 21 is used to convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD respectively; compensation parameters are pre-stored in the memory 23; the processor 22 is used to perform compensation calibration according to the digital signals TMR_AD, TEMP_AD and the compensation parameters, and output the compensated and calibrated data TMR_OUT.

[0039] Furthermore, the compensation parameters pre-stored in the memory 23 include zero-point temperature compensation parameters, sensitivity temperature compensation parameters, and linearity compensation parameters.

[0040] In this embodiment, the inside of the TMR chip 11 is designed with a push-pull Wheatstone full-bridge structure, including four non-shielded high-sensitivity TMR sensor elements, which can sense the magnitude of the external magnetic field. When the external magnetic field changes, its output voltage changes proportionally; the temperature chip 12 is arranged near the TMR chip 11 to sense the ambient temperature and provide a compensation basis for subsequent compensation algorithms.

[0041] Further referring to Figure 2 As shown, in another embodiment, the present invention provides a compensation method for a TMR electronic current transformer, using the aforementioned TMR electronic current transformer with temperature and linearity compensation, and including the following steps:

[0042] S1. Collect the voltage signal V_TMR output by the TMR chip 11 and the voltage signal V_TEMP output by the temperature chip 12;

[0043] S2. Through the analog-to-digital converter 21, convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD respectively;

[0044] S3. Based on the digital signals TMR_AD and TEMP_AD, and the compensation parameters pre-stored in the memory 23, perform compensation calibration, and the process of compensation calibration specifically includes:

[0045] S3a. Adopt the zero-point temperature compensation algorithm to compensate for the zero-point offset of the TMR chip 11;

[0046] S3b. Adopt the sensitivity temperature compensation algorithm to compensate for the temperature offset of the ratio of the TMR chip 11 sensing the measured current;

[0047] S3c. Adopt the linearity compensation algorithm to compensate for the non-linearity of the TMR chip 11;

[0048] S4. Output the compensated and calibrated data TMR_OUT.

[0049] Preferably, in step S3a, compensation is performed according to the digital signals TMR_AD and TEMP_AD and the zero-point temperature compensation parameters pre-stored in the memory 23 to reduce the zero-point offset of the TMR chip 11 with temperature change. The TMR data after zero-point temperature compensation is represented by TMR_1.

[0050] In this embodiment, when performing zero-point temperature compensation, subtract the TMR zero-point offset caused by temperature from TMR_AD, as shown in the following formula:

[0051] TMR_1 = TMR_AD - a0 + a1 * TEMP_AD + a2 * TEMP_AD 2 + a3 * TEMP_AD 3+a4*TEMP_AD 4

[0052] Among them, a0, a1, a2, a3, and a4 are zero-point temperature compensation parameters.

[0053] Preferably, in step S3b, compensation is performed according to TEMP_AD, the TMR data TMR_1 after zero-point temperature compensation, and the sensitivity temperature compensation parameters pre-stored in the memory 23, so as to reduce the sensitivity offset of the TMR chip 11 with temperature change. The TMR data after sensitivity temperature compensation is represented by TMR_2.

[0054] In this embodiment, when performing sensitivity temperature compensation, TMR_1 is multiplied by the TMR sensitivity offset caused by temperature, as shown in the following formula:

[0055] TMR_2 = TMR_1*b0 + b1*TEMP_AD + b2*TEMP_AD 2 +b3*TEMP_AD 3 +b4*TEMP_AD 4

[0056] Among them, b0, b1, b2, b3, and b4 are sensitivity temperature compensation parameters.

[0057] Preferably, in step S3c, compensation is performed according to the TMR data TMR_2 after sensitivity temperature compensation and the linearity compensation parameters pre-stored in the memory 23, so as to reduce the non-linearity of the TMR chip 11.

[0058] In this embodiment, when performing linearity compensation, non-linearity fitting is performed on TMR_2, as shown in the following formula:

[0059] TMR_OUT = c0 + c1*TMR_2 + c2*TMR_2 2

[0060] Among them, c0, c1, and c2 are linearity compensation parameters.

[0061] In addition, before step S1, there is also step S0: performing high-order fitting on the output value of the TMR chip 11 and the standard value of the measured current to determine the compensation parameters stored in the memory 23. The order of the compensation parameters is determined according to the fitting error and accuracy requirements; in this embodiment, the zero-point temperature compensation parameters are 4th-order compensation, the sensitivity temperature compensation parameters are 4th-order compensation, and the linearity compensation parameters are 2nd-order compensation; it can be understood that according to the actual situation, different compensation orders can also be adopted in other embodiments.

[0062] In this embodiment, zero-temperature compensation is used to compensate for the zero-offset caused by the resistance offset of the TMR bridge resistor. Before compensation, the zero-temperature coefficient of the TMR chip is approximately 500 ppm / °C. After compensation, the zero-offset has an error of no more than 0.2% in the temperature range of -40°C to 70°C; sensitivity-temperature compensation is used to compensate for the temperature offset of the TMR chip with respect to the measured current ratio. Before compensation, the sensitivity-temperature coefficient of the TMR chip is approximately 500 ppm / °C, and the maximum error caused in the temperature range of -40°C to 70°C is 5.5%. After compensation, the error is no more than 0.2%; linearity compensation is used to compensate for the non-linearity of the TMR. Before compensation, the non-linearity of the TMR is 3% or even 5%. After compensation, the error can be no more than 0.2%.

[0063] In summary, the TMR electronic current transformer and compensation method with temperature and linearity compensation provided by the present invention perform non-contact measurement of the bus current in the power system based on the tunnel magnetoresistance (TMR) chip, realizing the conversion from analog to digital and software compensation calibration; the present invention retains the advantages of the TMR sensor itself, such as non-contact, AC / DC co-measurement, wide frequency band, low delay, and wide dynamic measurement range, and improves the accuracy of the TMR chip itself through temperature and linearity compensation algorithms, realizing non-contact, AC / DC, wide frequency band, low delay, and high-precision measurement of the bus current in the power system.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A TMR electronic current transformer with temperature and linearity compensation, characterized in that, It includes a TMR sensing head (1) and a collection device (2); The TMR sensing head (1) includes a TMR chip (11), a temperature chip (12), and corresponding power supplies and peripheral circuits; The collection device (2) includes an analog-to-digital converter (21), a processor (22), a memory (23), and corresponding power supplies and peripheral circuits; The TMR chip (11) is used to sense the measured current value and convert it proportionally into a voltage signal V_TMR, and the temperature chip (12) is used to sense the ambient temperature value and convert it proportionally into a voltage signal V_TEMP. Both the voltage signals V_TMR and V_TEMP are transmitted to the analog-to-digital converter (21); The analog-to-digital converter (21) is used to convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD respectively; Compensation parameters are pre-stored in the memory (23); The processor (22) is used to perform compensation calibration based on the digital signals TMR_AD, TEMP_AD, and the compensation parameters, and output the compensated and calibrated data TMR_OUT.

2. The TMR electronic current transformer with temperature and linearity compensation according to claim 1, characterized in that, The compensation parameters pre-stored in the memory (23) include zero-point temperature compensation parameters, sensitivity temperature compensation parameters, and linearity compensation parameters.

3. A compensation method for a TMR electronic current transformer, characterized in that, The TMR electronic current transformer with temperature and linearity compensation described in claim 2 is adopted, and the following steps are included: S1. Collect the voltage signal V_TMR output by the TMR chip (11) and the voltage signal V_TEMP output by the temperature chip (12); S2. Through the analog-to-digital converter (21), convert the voltage signals V_TMR and V_TEMP into digital signals TMR_AD and TEMP_AD respectively; S3. Based on the digital signals TMR_AD and TEMP_AD, and the compensation parameters pre-stored in the memory (23), perform compensation calibration, and the process of compensation calibration specifically includes: S3a. Adopt a zero-point temperature compensation algorithm to compensate for the zero-point offset of the TMR chip (11); S3b. Adopt a sensitivity temperature compensation algorithm to compensate for the temperature offset of the proportion of the measured current sensed by the TMR chip (11); S3c. Adopt a linearity compensation algorithm to compensate for the non-linearity of the TMR chip (11); S4. Output the compensated and calibrated data TMR_OUT.

4. The compensation method of the TMR electronic current transformer according to claim 3, characterized in that In step S3a, compensation is performed according to the digital signals TMR_AD and TEMP_AD amounts and the zero-point temperature compensation parameters pre-stored in the memory (23) to reduce the zero-point offset of the TMR chip (11) with temperature change. The TMR data after zero-point temperature compensation is represented by TMR_1.

5. The compensation method of the TMR electronic current transformer according to claim 4, wherein, In step S3a, when performing zero-point temperature compensation, subtract the TMR zero-point offset caused by temperature from TMR_AD, as shown in the following formula: TMR_1 = TMR_AD - (a0 + a1*TEMP_AD + a2*TEMP_AD 2 + a3*TEMP_AD 3 + a4*TEMP_AD 4 ) where a0, a1, a2, a3, a4 are zero-point temperature compensation parameters.

6. The compensation method of the TMR electronic current transformer according to claim 3, characterized in that, In step S3b, compensation is performed according to TEMP_AD, the TMR data TMR_1 after zero-point temperature compensation, and the sensitivity temperature compensation parameters pre-stored in the memory (23) to reduce the sensitivity offset of the TMR chip (11) with temperature change. The TMR data after sensitivity temperature compensation is denoted as TMR_2.

7. The compensation method of the TMR electronic current transformer according to claim 6, characterized in that In step S3b, when performing sensitivity temperature compensation, TMR_1 is multiplied by the TMR sensitivity offset caused by temperature, as shown in the following formula: TMR_2 = TMR_1 * (b0 + b1 * TEMP_AD + b2 * TEMP_AD 2 + b3 * TEMP_AD 3 + b4 * TEMP_AD 4 ) where b0, b1, b2, b3, b4 are sensitivity temperature compensation parameters.

8. The compensation method of the TMR electronic current transformer according to claim 3, characterized in that In step S3c, compensation is performed according to the TMR data TMR_2 after sensitivity temperature compensation and the linearity compensation parameters pre-stored in the memory (23) to reduce the non-linearity of the TMR chip (11).

9. The compensation method of the TMR electronic current transformer according to claim 8, characterized in that, In step S3c, when performing linearity compensation, non-linearity fitting is performed on TMR_2, as shown in the following formula: TMR_OUT = c0 + c1 * TMR_2 + c2 * TMR_2 2 where c0, c1, c2 are linearity compensation parameters.

10. The compensation method of the TMR electronic current transformer according to claim 3, characterized in that, Before step S1, there is also step S0: performing high-order fitting on the output value of the TMR chip (11) and the standard value of the measured current to determine the compensation parameters stored in the memory (23).

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