A Single-End Impedance Detection Method for Conductive Cables Based on Current Source Excitation

Abstract

This invention provides a single-ended impedance detection method for conductive cables based on current source excitation, applicable to detecting the resistance and self-inductance of conductive cables of any material, length, and diameter. The method divides the conductive cable into two bundles (e.g., in twisted-pair applications). By injecting a current source excitation signal near the cable end, the voltage and current at the near end are detected, yielding the cable's resistance and self-inductance parameters. This invention eliminates the need for auxiliary components at the load end, accurately obtains cable resistance and self-inductance values, has simple logic, is easy to implement, and can be applied to any power supply system.

Description

Technical Field

[0001] This invention relates to impedance detection technology, and more particularly to a method for single-end impedance detection of conductive cables based on current source excitation. Background Technology

[0002] Cables used for long-distance power transmission have significant resistance and inductance, resulting in a lower input voltage to the load system at the far end of the power supply compared to its actual output voltage. This is especially true in low-voltage, high-current applications, where the voltage drop caused by cable resistance is substantial, and the resistance value can fluctuate with environmental factors, affecting the normal operation of the load system. When disturbances occur in the load system, voltage fluctuations may occur at the cable end. Due to the high inductance of long-distance cables, the power supply may not respond promptly, potentially causing load system malfunctions or triggering protection mechanisms.

[0003] Existing methods for detecting the impedance of long cables mainly involve connecting a sufficiently large capacitor in parallel at the end of the cable to achieve a low AC impedance at the load end. For example, the inventor's prior patent application (Chinese Patent Publication No. CN114113794A) measures the voltage change caused by line resistance by continuously modulating the current to the load system, calculating the cable resistance value, and thus compensating for cable voltage drop. However, this method fails to detect the cable's self-inductance, resulting in an incomplete cable impedance model, which is detrimental to the dynamic analysis and normal operation of the power supply system. Summary of the Invention

[0004] To address the problems in existing technologies, this invention provides a single-end impedance detection method for conductive cables based on current source excitation. This method divides the conductive cable into two bundles, injects a current source excitation signal near the cable end, and detects the voltage and current at the near end to obtain the cable's resistance and self-inductance parameters.

[0005] This invention is specifically achieved through the following technical solution:

[0006] A method for single-end impedance detection of conductive cables based on current source excitation, the method dividing the conductive cable into two bundles, the method comprising:

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

[0008] S2: Near-end voltage of sampling cable v o and cable current i o i o1 i o2 The value is calculated, and the periodic average value is calculated to obtain equations (1) to (3):

[0009]

[0010] v L=R L ×i o (3) Among them, This represents the average value of the total current in the cable. This represents the average current of the two cable bundles. R is the average value of the near-end voltage of the cable. total To detect the total resistance of the circuit loop;

[0011] S3: At any transient time t1 of the current source excitation signal, sample the transient quantities of the current in the two cable bundles and their rates of change:

[0012]

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

[0014]

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

[0016] S5: At any transient time t2 of the current source excitation signal, sample the transient quantities of the current in the two cable bundles and their rate of change, and obtain equation (6):

[0017]

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

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

[0020]

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

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

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

[0024] The beneficial effects of this invention are as follows: The method of this invention does not require adding any auxiliary components at the load end. It accurately obtains the cable resistance and self-inductance simply by dividing the conductive cable into two bundles and monitoring their respective response currents. The logic is simple and easy to implement. This method can be used in power systems to achieve single-end impedance detection of long cables. Furthermore, based on the detection results, cable voltage drop compensation can be performed to solve the problem of undervoltage in the load system caused by resistance voltage drop in long-distance cables, achieving precise control of the voltage at the cable end. This method can help solve the impact of long-distance cable inductance on system dynamics, address the problem of cable voltage delay response, and prevent load system failures. This method can be applied to any power system, is not limited by the structure of the front-end power supply, and has universality. Attached Figure Description

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

[0026] Figure 2(a) is a waveform diagram of the total current response of the cable under the current source excitation signal;

[0027] Figure 2(b) is a waveform diagram of the near-end voltage response of the cable under the current source excitation signal;

[0028] Figure 2(c) is a waveform diagram of the voltage response at the end of the cable under the current source excitation signal;

[0029] Figure 2(d) is a waveform diagram of the current response of the first cable bundle under the current source excitation signal;

[0030] Figure 2(e) is a waveform diagram of the current response of the second bundle of cables under the current source excitation signal. Detailed Implementation

[0031] Figure 1 This is a block diagram of the detection system provided in 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-inductances are L and L respectively. c1 and L c2 v o For the near-end voltage of the cable, i o i represents the total current in the cable. o1 and i o2 The current divided into sections for each cable bundle, v LThis refers to the load-end voltage (i.e., the voltage at the end of the cable). The detection method of this 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 describes the single-ended impedance detection method for conductive cables based on current source excitation of the present invention.

[0033] Assume the power system injects a trapezoidal current source type excitation signal into the near end of the cable, as shown in Figure 2(a) i. o The waveforms are shown below. The cable near-end voltage and its average value, cable current and its average value, and the transient rate of change of cable current in the following relationships can all be obtained by sampling and calculating the voltage and current at the near end of the cable. Figure 2(b) shows the cable near-end voltage response waveform, Figure 2(c) shows the cable end voltage response waveform, Figure 2(d) shows the current response waveform of the first cable bundle, and Figure 2(e) shows the current response waveform of the second cable bundle.

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

[0035]

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

[0037] For any transient time t1 of a current source excitation signal, the following relationship exists:

[0038]

[0039] Combining equations (1) and (4), the impedance relationship between the two cables can be obtained as follows:

[0040]

[0041] Where m and n are constants obtained by solving equations (1) and (4).

[0042] According to Kirchhoff's voltage law, the following relationship exists for any transient time t2 of the current source excitation signal:

[0043]

[0044] Therefore, by combining equations (2), (3), (5), and (6), the equivalent resistance R of the cable can be obtained. c1 R c2 Equivalent self-inductance L of cable c1 L c2 The value of . That is, the equivalent total impedance of the power supply cable is:

[0045]

[0046] Note 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, triangular wave, sawtooth wave, etc.

[0047] Therefore, the specific steps of this invention to achieve single-end impedance detection of conductive cables are as follows:

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

[0049] Step 2: Sample the near-end voltage v of the cable o and cable current i o i o1 i o2 By calculating the value and the periodic average, we can obtain formulas (1) to (3);

[0050] Step 3: At any transient time t1 of the current source excitation signal, sample the transient quantities of the current in the two cables and their current change rate to obtain formula (4);

[0051] Step 4: By combining formulas (1) and (4), we can obtain formula (5);

[0052] Step 5: At any transient time t2 of the current source excitation signal, sample the transient quantities of the current in the two cables and their current change rate to obtain formula (6);

[0053] Step 6: By combining formulas (2), (3), (5), and (6), the equivalent resistance R of the cable can be obtained. c1 R c2 Equivalent self-inductance L of cable c1 L c2 The value of .

[0054] Step 7: Calculate the equivalent total impedance of the power supply cable as shown in formula (7).

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0056] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for single-end impedance detection of conductive cables based on current source excitation, characterized in that: The method divides the conductive cable into two bundles, the method comprising: S1: The power supply system injects a current source type excitation signal into the near end of the cable; S2: Sampling cable near-end voltage v o and cable current i o , i o1 , i o2 values and calculate the period average values, resulting in equations (1) - (3): v L =R L ×i o (3) Among them, This represents the average value of the total current in the cable. This represents the average current of the two cable bundles. R is the average value of the near-end voltage of the cable. total To detect the total resistance of the circuit loop; S3: At any transient time t1 of the current source excitation signal, sample the transient quantities of the current in the two cable bundles and their rates of change: S4: By combining equations (1) and (4), the impedance relationship between the two cables can be obtained as follows: Where m and n are constants obtained by solving equations (1) and (4); S5: At any transient time t2 of the current source excitation signal, sample the transient quantities of the current in the two cable bundles and their rate of change, and obtain equation (6): S6: Solve equations (2), (3), (5), and (6) simultaneously to obtain the equivalent resistance R of the cable. c1 R c2 Equivalent self-inductance L of cable c1 L c2 The value; S7: Calculate the equivalent total impedance of the power supply cable, where R c For the equivalent total resistance, L c For equivalent total self-induction:

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

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

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

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