Conductive cable impedance single-end detection method based on current source excitation

Abstract

The invention provides a conductive cable impedance single-end detection method based on current source excitation. The conductive cable impedance single-end detection method is suitable for detecting resistance and self-inductance of conductive cables of any material, length and diameter. According to the method, a conductive cable is divided into two bundles (such as a twisted pair application scene), a current source type excitation signal is injected into the near end of the cable, the voltage of the near end of the cable and the magnitude of current of the cable are detected, and the resistance and self-inductance parameters of the cable can be obtained. The method can accurately obtain the cable resistance and the self-inductance value without adding an auxiliary element at the load end, is simple in logic and easy to implement, and can be applied to any power supply system.

Description

Technical Field

[0001] The present invention relates to impedance detection technology, and in particular to a conductive cable impedance single-end detection method based on current source excitation. Background Art

[0002] Cables used for long-distance power transmission have large resistance and self-inductance, so the input voltage of the remote load system of the power supply will be lower than the actual output voltage of the power supply. Especially in low-voltage and high-current applications, the voltage drop caused by cable resistance is large, and the resistance value will change with environmental factors, thus affecting the normal operation of the load system. When the load system is disturbed, it may cause the voltage at the end of the cable to fluctuate. Due to the large inductance of the long-distance cable, the power supply may not be able to respond in time, which may cause the load system to fail or enter a protection state.

[0003] The existing long cable impedance detection method is mainly to achieve a lower AC impedance at the load end by connecting a sufficiently large capacitor in parallel at the end of the cable, such as the patent previously applied by the inventor (China Patent Publication No. CN114113794A), which continuously modulates the current to the load system to measure the voltage change caused by the line resistance, calculates the cable resistance value, and then performs cable voltage drop compensation. However, this method fails to detect the self-inductance of the cable, making the cable impedance model incomplete, which is not conducive to the dynamic analysis and normal operation of the power supply system. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a single-ended detection method for conductive cable impedance based on current source excitation. The method divides the conductive cable into two bundles, injects a current source type excitation signal at the proximal end of the cable, detects the voltage at the proximal end of the cable and the amount of cable current, and obtains the resistance and self-inductance parameters of the cable.

[0005] The present invention is specifically implemented through the following technical solutions:

[0006] A single-ended detection method for conductive cable impedance based on current source excitation, wherein the conductive cable is divided into two bundles, and the method comprises:

[0007] S1: The power system injects a current source excitation signal into the near end of the cable;

[0008] S2: Sample the voltage near the cable v o and the cable current i o 、i o1 、i o2 value, and calculate the period average value to obtain equations (1) to (3):

[0009]

[0010] v L=R L ×i o (3) Among them, is the average value of the total cable current, is the average value of the current in the two cables, is the average voltage near the cable end, R total is the total resistance value of the detection circuit loop;

[0011] S3: At any instant t1 of the current source excitation signal, sample the instantaneous value of the current of the two cables and their current change rate:

[0012]

[0013] S4: By combining equations (1) and (4), the impedance relationship between the two cables can be obtained as follows:

[0014]

[0015] Wherein, m and n are constants obtained by solving equations (1) and (4);

[0016] S5: At any instant t2 of the current source excitation signal, sample the instantaneous current of the two cables and their current change rate to obtain equation (6):

[0017]

[0018] S6: Combine equations (2), (3), (5), and (6) to obtain the equivalent resistance R of the cable c1 , R c2 And the cable equivalent self-inductance L c1 , L c2 The value of

[0019] S7: Calculate the equivalent total impedance of the power supply cable, where R c is the equivalent total resistance, L c is the equivalent total self-inductance:

[0020]

[0021] As a further improvement of the present invention, the current source excitation signal includes but is not limited to a trapezoidal wave, a pseudo-trapezoidal wave, a square wave, a triangular wave, and a sawtooth wave.

[0022] As a further improvement of the present invention, the method does not require any auxiliary components to be added at the load end.

[0023] The present invention also provides a single-ended detection system for conductive cable impedance, which is used to implement the detection method of the present invention. The system includes a power supply system, a conductive cable and a load resistor. The conductive cable is divided into two bundles, one end of each bundle is connected to the power supply system, and the other end is connected to the load circuit.

[0024] The beneficial effects of the present invention are as follows: the method of the present invention does not require the addition of any auxiliary components at the load end, and the cable resistance and self-inductance values ​​can be accurately obtained by only dividing the conductive cable into two bundles and monitoring their response currents respectively. The logic is simple and easy to implement. The method can be used in a power supply system to realize single-ended detection of the impedance of a long cable, and further perform cable voltage drop compensation based on the detection results to solve the problem of undervoltage in the load system caused by the resistance voltage drop of the long-distance cable, and realize precise control of the voltage at the end of the cable. The method can assist in solving the impact of the inductance of the long-distance cable on the system dynamics, solve the problem of delayed response of the cable voltage, and avoid failures in the load system. The method can be applied to any power supply system, is not restricted by the structure of the front-end power supply, and has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a principle block diagram of a detection system according to an embodiment of the present invention;

[0026] FIG2(a) is a waveform diagram of the total current response of the cable under the current source excitation signal;

[0027] FIG2( b ) is a waveform diagram of the voltage response at the near end of the cable under the current source excitation signal;

[0028] FIG2(c) is a waveform diagram of the voltage response at the cable end under the current source excitation signal;

[0029] FIG2( d ) is a waveform diagram of the current response of the first bundle of cables under the current source excitation signal;

[0030] FIG2( e ) is a waveform diagram of the current response of the second bundle of cables under the current source excitation signal. DETAILED DESCRIPTION

[0031] Figure 1 is a block diagram of a detection system provided by an embodiment of the present invention. The entire detection system consists of a power supply system, two bundles of conductive cables and a load resistor, wherein the equivalent resistance of each bundle of cables is R c1 and R c2 , the equivalent self-inductance is L c1 and L c2 , v o is the voltage near the cable end, i o is the total cable current, i o1 and i o2 are the currents of each cable bundle, v LThe detection method of the present invention can measure twisted pair cables, bare wires and bare conductor products (such as copper-aluminum single wires, hard copper stranded wires, hard aluminum stranded wires, etc.), power cables, overhead insulated cables, coaxial cables, etc.

[0032] The following is an introduction to the conductive cable impedance single-ended detection method based on current source excitation of the present invention.

[0033] Assume that the power system injects a trapezoidal wave current source type excitation signal to the near end of the cable, as shown in Figure 2(a). o As shown in the waveform. It is known that the cable near-end voltage and its average value, cable current and its average value, and cable current transient change rate in the following relationship can all be obtained by sampling the voltage and current at the near-end of the cable and calculating them. As shown in Figure 2(b), the voltage response waveform at the near-end of the cable, Figure 2(c) is the voltage response waveform at the end of the cable, Figure 2(d) is the current response waveform of the first bundle of cables, and Figure 2(e) is the current response waveform of the second bundle of cables.

[0034] The loop formed by the cable impedance and the load has a steady-state relationship:

[0035]

[0036] v L =R L ×i o (3) Among them, is the average value of the total cable current, is the average value of the current in the two cables, is the average voltage near the cable end, R total is the total resistance of the loop, R c1 / / indicates R c2 The value of two resistors connected in parallel.

[0037] At any transient t1 moment of the current source excitation signal, there is a relationship:

[0038]

[0039] By combining formula (1) and formula (4), the impedance relationship of the two cables can be obtained as follows:

[0040]

[0041] Wherein, m and n are constants obtained by solving equation (1) and equation (4).

[0042] According to Kirchhoff's voltage law, there is a relationship at any transient t2 of the current source excitation signal:

[0043]

[0044] Therefore, the combined equations (2), (3), (5), and (6) can be used to obtain the cable equivalent resistance R c1 , R c2 And the cable equivalent self-inductance L c1 , L c2 That is, the equivalent total impedance of the power supply cable is:

[0045]

[0046] It should be noted that the current source excitation signal injected into the near end of the cable in this method can be any waveform, including but not limited to trapezoidal wave, pseudo-trapezoidal wave, square wave, triangle wave, sawtooth wave, etc.

[0047] Therefore, the specific steps of the present invention to realize single-ended detection of conductive cable impedance are as follows:

[0048] Step 1: The power system injects a current source excitation signal into the near end of the cable;

[0049] Step 2: Sample the voltage v near the cable o and the cable current i o 、i o1 、i o2 Value, and calculate the period average value, we can get formulas (1) to (3);

[0050] Step 3: At any instant t1 of the current source excitation signal, sample the instantaneous value of the current of the two cables and their current change rate, and we can get formula (4);

[0051] Step 4: Combining formulas (1) and (4), we can get formula (5);

[0052] Step 5: At any instant t2 of the current source excitation signal, sample the instantaneous value of the current of the two cables and their current change rate, and you can get formula (6);

[0053] Step 6: Combine equations (2), (3), (5), and (6) to obtain the equivalent resistance R of the cable. c1 , R c2 And the cable equivalent self-inductance L c1 , L c2 The value of .

[0054] Step 7: Calculate the equivalent total impedance of the power supply cable according to formula (7).

[0055] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0056] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A single-ended detection method for conductive cable impedance based on current source excitation, characterized in that: The method divides the conductive cables into two bundles, and the method comprises: S1: The power system injects a current source excitation signal into the near end of the cable; S2: Sample the voltage near the cable v o and the cable current i o 、i o1 、i o2 value, and calculate the period average value to obtain equations (1) to (3): v L =R L ×i o (3) Among them, is the average value of the total cable current, is the average value of the current in the two cables, is the average voltage near the cable end, R total is the total resistance value of the detection circuit loop; S3: At any instant t1 of the current source excitation signal, sample the instantaneous value of the current of the two cables and their current change rate: S4: By combining equations (1) and (4), the impedance relationship between the two cables can be obtained as follows: Wherein, m and n are constants obtained by solving equations (1) and (4); S5: At any instant t2 of the current source excitation signal, sample the instantaneous current of the two cables and their current change rate to obtain equation (6): S6: Combine equations (2), (3), (5), and (6) to obtain the equivalent resistance R of the cable c1 , R c2 And the cable equivalent self-inductance L c1 , L c2 The value of S7: Calculate the equivalent total impedance of the power supply cable, where R c is the equivalent total resistance, L c is the equivalent total self-inductance:

2. The detection method according to claim 1, characterized in that: The current source excitation signal includes but is not limited to a trapezoidal wave, a pseudo-trapezoidal wave, a square wave, a triangle wave, and a sawtooth wave.

3. The detection method according to claim 1, characterized in that: The method does not require any auxiliary components to be added at the load end.

4. A conductive cable impedance single-ended detection system based on current source excitation, characterized in that: The system is used to implement the detection method according to any one of claims 1 to 3, and the system includes a power supply system, a conductive cable and a load resistor, wherein the conductive cable is divided into two bundles, one end of each bundle is connected to the power supply system, and the other end is connected to the load circuit.

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