Method and compensation circuit for crosstalk compensation

Abstract

The invention relates to a method for crosstalk compensation of output signals (SL1 (t), SL2 (t)) of at least one small signal converter for measuring electrical quantities on at least two conductors (L1, L2), at least one of which causes crosstalk,-wherein when a sinusoidal electrical quantity is fed into one of the conductors (L1, L2), the output signals (SL1 (t), SL2 (t)) of the small signal converter are compensated for the crosstalk of the output signals (SL1 (t), SL2 (t)). A crosstalk amplitude and a crosstalk phase angle of the small signal converter on the other conductor (L1, L2) are determined,-wherein for each small signal converter the crosstalk (CrCap) at a phase angle of 90 DEG (or-90 DEG) is determined from the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle,-wherein for each small signal converter the crosstalk (CrCap) at a phase angle of 90 DEG (or-90 DEG) is determined from the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle,-wherein the crosstalk (CrCap) at a phase angle of 90 DEG (or-90 DEG) is determined from the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle. The crosstalk (Cind) at a phase angle of 0 DEG (or 180 DEG) is determined from the product of the measured crosstalk amplitude and the cosine of the measured crosstalk phase angle,-wherein, in order to form the compensated output signal (SL1 comp (t), SL2 comp (t)) of each small signal converter considered, the crosstalk (Cind) is determined at a phase angle of 0 DEG (or 180 DEG). From the uncompensated output signal (SL1 (t), SL2 (t)) of the small signal converter, the product of the electrical quantity on the respective other conductor (L1, L2) and the crosstalk (Cind) at a phase angle of 0 or 180 DEG and the product of the electrical quantity on the respective other conductor (L1, L2) phase shifted by 90 DEG and the crosstalk (CrCap) at a phase angle of + 90 DEG or-90 DEG are subtracted.

Description

[0001] This invention relates to a method and compensation circuit for crosstalk compensation, particularly in small-signal converters.

[0002] In measurement transducers according to IEC 61869, especially small-signal measurement transducers such as Rogowski coils and capacitive voltage sensors, crosstalk typically occurs between adjacent conductors. That is, for example, a Rogowski coil that should measure the current in one of the three phases may also measure the current in the other two phases to some extent. This is undesirable.

[0003] To prevent this, one could try designing and shielding the sensor to minimize crosstalk. Another possibility is to subsequently correct the measured signal through calculation.

[0004] The technical problem to be solved by the present invention is to provide a novel method and a novel compensation circuit for crosstalk compensation of the output signals of at least two small-signal converters.

[0005] The technical problem described herein is solved by a method for crosstalk compensation of the output signals of at least two small-signal converters having the features of claim 1 and a compensation circuit for crosstalk compensation of the output signals of at least two small-signal converters having the features of claim 6.

[0006] The advantageous design of the present invention is the one described in the dependent claims.

[0007] A method is proposed for crosstalk compensation of the output signal of at least one small-signal converter used to measure electrical quantities on at least two conductors, where at least one conductor causes crosstalk. Here, when a sinusoidal electrical quantity is fed into the conductor, the crosstalk amplitude and crosstalk phase angle of the small-signal converter on the other conductor are determined. Furthermore, for each small-signal converter, the crosstalk at a phase angle of +90° (or -90°) is determined by the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle. Additionally, for each small-signal converter, the crosstalk at a phase angle of 0° (or 180°) is determined by the product of the measured crosstalk amplitude and the cosine of the measured crosstalk phase angle. According to the present invention, in order to form the compensated output signal of each considered small-signal converter, the product of the electrical quantity on the corresponding other conductor and the crosstalk at a phase angle of 0° (or 180°) and the product of the electrical quantity on the corresponding other conductor that has been phase-shifted by 90° and the crosstalk at a phase angle of +90° (or -90°) are subtracted from the uncompensated output signal of the small-signal converter.

[0008] This method completely eliminates crosstalk.

[0009] Multiple couplings can be considered using corresponding mathematical matrix calculation methods.

[0010] In one implementation, the method is applied to multiple small-signal converters on a single conductor.

[0011] In one implementation, the crosstalk amplitude and crosstalk phase angle of each small-signal converter are determined once, especially during individual testing.

[0012] In one implementation, an output signal with a 90° phase shift is generated by establishing a time derivative on the corresponding output signal.

[0013] In one embodiment, an integrator is provided for each conductor, wherein the signal measured at the output of the integrator is used as the output signal of the corresponding conductor, and the signal measured at the input of the integrator is used as the derivative.

[0014] In one implementation, a differentiator can be used to generate the derivative.

[0015] According to one aspect of the invention, a compensation circuit is proposed for crosstalk compensation of the output signals of at least two measurement converters, particularly small-signal converters, which are used to measure electrical quantities on a conductor respectively. Here, especially with proper consideration of multiple crosstalk, the crosstalk amplitude and crosstalk phase angle of each measurement converter or small-signal converter are known, for example, by determining them at once. The crosstalk is decomposed into 0° (or 180°) portions and 90° (or -90°) portions as described above.

[0016] For each measurement converter or small-signal converter, the crosstalk at a phase angle of 0° or 180° is determined by the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle, and is therefore known.

[0017] For each measurement converter or small-signal converter, the crosstalk at a phase angle of 0° or 180° is determined by the product of the measured crosstalk amplitude and the cosine of the measured crosstalk phase angle, and is therefore known.

[0018] According to the present invention, the compensation circuit is designed as an analog and / or digital electronic circuit for forming a compensated output signal of each considered measurement converter or small-signal converter. This electronic circuit is designed to subtract from the uncompensated output signal of the measurement converter or small-signal converter the product of the electrical quantity of the corresponding other measurement converter or small-signal converter and the crosstalk determined at a phase angle of 0° (or 180°), and the product of the electrical quantity of the corresponding other measurement converter or small-signal converter phase-shifted by 90° and the crosstalk at a phase angle of +90° (or -90°).

[0019] This compensation circuit completely eliminates crosstalk.

[0020] In one embodiment, the compensation circuit includes elements for generating an output signal with a 90° phase shift by establishing a time derivative with respect to the corresponding output signal.

[0021] In one implementation, the element is designed as an integrator or a differentiator.

[0022] According to one aspect of the invention, a measurement circuit is proposed, comprising at least two small-signal converters for measuring electrical quantities on a respective conductor, and a compensation circuit as described above, wherein the small-signal converters are configured to use the time derivative of the signal under test.

[0023] For example, a small-signal converter can use a Rogowski coil with an integrator. In small-signal converters that use the time derivative of the output signal to be measured (e.g., a Rogowski coil), the time derivative is already present, making implementation particularly simple.

[0024] The above-described features, characteristics, and advantages of the present invention, as well as the ways in which they are implemented, will become clearer and more readily understood in conjunction with the following description of embodiments, which are described in detail with reference to the accompanying drawings.

[0025] In the attached diagram:

[0026] Figure 1 A schematic diagram of a compensation circuit for the output signals of two small-signal converters used to measure electrical quantities is shown.

[0027] The only Figure 1 This is a schematic diagram of a compensation circuit 1 for measuring the output signals of two small-signal converters, specifically current or voltage, on conductors L1 and L2 respectively. The compensation circuit 1 is used to calculate and compensate for crosstalk between the two channels or conductors L1 and L2.

[0028] Here, according to the invention, crosstalk (also known as crosstalk coupling or crosstone) is compensated at phase angles of 0° (or 180°) and +90° (or -90°).

[0029] In calculations, the following is generally applicable:

[0030] S L1 (t) = e iωt

[0031] Cr(t) = S L1 (t)(Cr ind +iCr cap )

[0032] S L1(t) is the current or voltage in a particular conductor, such as conductor L1.

[0033] Cr(t) is the crosstalk measured in another conductor, such as conductor L2.

[0034] Cr ind It is crosstalk with a phase angle of 0° (or 180°).

[0035] Cr cap It is crosstalk with a phase angle of +90° (or -90°).

[0036] Crosstalk Cr cap One possible reason is capacitive crosstalk of the voltage in the Rogowski coil, which is proportional to the current. (The last part, "made by Cr," appears to be a fragment and doesn't translate directly.) ind The induced voltage causes a current to flow, which in turn induces a voltage through the self-inductance of the coil. Adjacent conductors induce eddy currents in the metal mesh cage of the sensor ring. These eddy currents generate a radial magnetic field that couples a voltage into the non-precise radial winding of the Rogowski coil.

[0037] When measuring (single-item testing) a small-signal converter, the crosstalk amplitude (CTA) and crosstalk phase angle (CTW) are determined and provided to the user.

[0038] Here, during measurement, before compensation applies:

[0039]

[0040] [2]

[0041] [3]

[0042] The compensation device can be configured as an analog or digital electronic circuit to eliminate crosstalk in the output signal S(t). In a typical, simple method, the following applies:

[0043]

[0044] In other words, in order to form the compensated output signal S of conductor L2 L2comp (t), the uncompensated output signal S from conductor L2 L2 The uncompensated output signal S of the other conductor L1 is subtracted from (t). L1 (t) is the product of the measured crosstalk amplitude CTA.

[0045] Here, the compensation applies afterward:

[0046] [5]

[0047] in, That is, amplitude Cr cap Phase = 90°

[0048] In a method improved according to the present invention, the following applies:

[0049]

[0050]

[0051] Among them, Cr cap = CTA × Sin(CTW), Cr ind = CTA × Cos(CTW)

[0052] In other words, in order to form the compensated output signal S of conductor L2 L2comp (t), the uncompensated output signal S from conductor L2 L2 Subtract the electrical quantity S on another conductor L1 from (t) L1 (t) and crosstalk Cr at a phase angle of 0° (or 180°) ind The product of and the electrical quantity iS on another conductor L1 that has been phase-shifted by 90° L1 (t) and crosstalk Cr at a phase angle of +90° (or -90°) Cap The product of . Crosstalk Cr at phase angles of 0° or 180°. Cap The crosstalk amplitude (CTA) is determined by the product of the measured crosstalk amplitude (CTA) and the sine of the measured crosstalk phase angle. The crosstalk amplitude (CTA) at phase angles of 0° or 180° is... ind It is determined by the product of the measured crosstalk amplitude CTA and the cosine of the measured crosstalk phase angle CTW.

[0053] Here, the compensation applies afterward:

[0054]

[0055] This method completely eliminates crosstalk. However, this requires an output signal iS from another conductor L1 that has been phase-shifted by 90°. L1 (t). This can be achieved, for example, by adjusting the output signal S. L1 (t) Establish the time derivative S L1 It is generated by '(t).

[0056] In small-signal converters that utilize the time derivative of the signal under test (such as Rogowski coils and integrators), this time derivative already exists, making implementation particularly simple.

[0057] For example, an integrating element 2.1, 2.2 can be set for each channel or conductor L1, L2, wherein the output signal S of the corresponding conductor L1, L2L1 (t), S L2 (t) is measured after the integrators 2.1 and 2.2, while the derivative iS L1 (t), iS L2 (t) is measured before the integrating elements 2.1 and 2.2.

[0058] Significantly improved interference suppression is achieved using the method according to the present invention.

[0059] Multiple couplings can be considered using the mathematical matrix computation method described below.

[0060] Three measurement transducers, such as three small-signal transducers, measure the following output signal I on three phases A, B, C or conductors, for example. meas These output signals are derived from the real current taking crosstalk Cr into account, according to the following equation [9]:

[0061] [9]

[0062] To determine the true current from the measured current, an inverse matrix is ​​used:

[0063]

[10]

[0064] For example, when there is 3.6% crosstalk in all three phases, the inverse matrix is:

[0065]

[11]

[0066] Although the invention has been further illustrated and described in detail through preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A method for processing the output signal (S) of at least one small-signal converter L1 (t), S L2 (t)) A method for crosstalk compensation, wherein the small-signal converter is used to measure electrical quantities on at least two conductors (L1, L2), wherein at least one conductor causes crosstalk. - Among them, When a sinusoidal electrical quantity is fed into one of the conductors (L1, L2), the crosstalk amplitude and crosstalk phase angle of the small-signal converter on the other conductor (L1, L2) are determined. - Wherein, for each small-signal converter, the crosstalk (Cr) at a phase angle of 90° (or -90°) is determined by the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle. Cap ), - Wherein, for each small-signal converter, the crosstalk (Cr) at a phase angle of 0° (or 180°) is determined by the product of the measured crosstalk amplitude and the cosine of the measured crosstalk phase angle. ind ), - Wherein, in order to form the compensated output signal (S) of each considered small-signal converter L1comp (t), S L2comp (t)), from the uncompensated output signal (S) of the small-signal converter L1 (t), S L2 Subtract the electrical quantities on the corresponding other conductor (L1, L2) and the crosstalk (Cr) at a phase angle of 0° or 180° from (t)). ind The product of ) and the electrical quantities on the corresponding other conductors (L1, L2) that have been phase-shifted by 90°, and the crosstalk (Cr) at a phase angle of +90° or -90°. Cap The product of ).

2. The method according to claim 1, wherein, The crosstalk amplitude and crosstalk phase angle of each small-signal converter are determined at once, especially in individual product testing.

3. The method according to claim 1 or 2, wherein, The output signal with a 90° phase shift (iS) L1 (t), iS L2 (t) is obtained by adjusting the corresponding output signal (S) L1 (t), S L2 (t) Establish the time derivative (S) L1 '(t),S L2 It is generated by '(t)).

4. The method according to claim 3, wherein, An integrator (2.1, 2.2) is provided for each conductor (L1, L2), wherein the signal measured at the output of the integrator (2.1, 2.2) is used as the output signal (S) of the corresponding conductor (L1, L2). L1 (t), S L2 (t)), where the signal measured at the input of the integrating elements (2.1, 2.2), especially the output signal (iS) phase-shifted by 90°. L1 (t), iS L2 (t) is used as the derivative (S) L1 '(t),S L2 '(t)).

5. The method according to claim 3, wherein, Differentiators are used to generate derivatives.

6. A method for processing the output signal (S) of at least one small-signal converter L1 (t), S L2 (t)) A compensation circuit (1) for crosstalk compensation, wherein the small-signal converter is used to measure electrical quantities on at least two conductors (L1, L2), wherein at least one conductor causes crosstalk. - in, The crosstalk amplitude and crosstalk phase angle of each small-signal converter are known. - Wherein, for each small-signal converter, the crosstalk (Cr) at a phase angle of 90° or -90° is determined by the product of the measured crosstalk amplitude and the sine of the measured crosstalk phase angle. Cap It is known that... - Wherein, for each small-signal converter, the crosstalk (Cr) at a phase angle of 0° or 180° is determined by the product of the measured crosstalk amplitude and the cosine of the measured crosstalk phase angle. ind It is known that... - Wherein, the compensation circuit (1) is designed to generate the compensated output signal (S) of each considered small-signal converter. L1comp (t), S L2comp (t)) analog or digital electronic circuitry, and configured for the uncompensated output signal (S) of the small-signal converter. L1 (t),S L2 Subtract the electrical quantities on the corresponding other conductor (L1, L2) and the crosstalk (Cr) at a phase angle of 0° or 180° from (t)). ind The product of ) and the electrical quantities on the corresponding other conductors (L1, L2) that have been phase-shifted by 90°, and the crosstalk (Cr) at a phase angle of +90° or -90°. Cap The product of ).

7. The compensation circuit (1) according to claim 6, wherein the compensation circuit comprises elements, the elements being used to respond to the corresponding output signal (S) L1 (t), S L2 (t) Establish the time derivative (S) L1 '(t),S L2 '(t)) to generate an output signal (iS) with a 90° phase shift. L1 (t), iS L2 (t)).

8. The compensation circuit (1) according to claim 7, wherein, The element is designed as an integrator (2.1, 2.2) or a differentiator.

9. A measurement circuit comprising at least two small-signal converters for measuring electrical quantities on a conductor (L1, L2) respectively, and a compensation circuit (1) according to any one of claims 6 to 8, wherein, The small-signal converter is configured to use the signal under test, especially the output signal (iS) phase-shifted by 90°. L1 (t), iS L2 The time derivative of (t) (S) L1 '(t),S L2 '(t)).

10. The measurement circuit according to claim 9, wherein, The small-signal converter is arranged to use a Rogowski coil with an integrator, or wherein the small-signal converter is designed as a capacitor with displacement current measurement, or as a C voltage divider or RC voltage divider.

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