A single-ended impedance detection circuit and method for conductive cables based on switching transients.

Abstract

This invention discloses a circuit and method for single-ended impedance detection of conductive cables based on switching transients. The circuit includes: a power supply, a switch S, an auxiliary resistor Raux, an equivalent resistance Rc of the cable, an equivalent self-inductance Lc of the cable, a filter capacitor Caux, and a load or secondary power supply. One end of the switch S is connected to the power supply, and the other end is connected to one end of the auxiliary resistor Raux and one end of the equivalent resistance Rc of the cable. The other end of the auxiliary resistor Raux is connected to the power supply, the load or secondary power supply, and one end of the filter capacitor Caux. The other end of the equivalent resistance Rc of the cable is connected to one end of the equivalent self-inductance Lc of the cable. The other end of the equivalent self-inductance Lc of the cable is connected to the other end of the filter capacitor Caux and the load or secondary power supply. This invention enables accurate detection of the impedance of conductive cables at only one end of a long cable.

Description

Technical Field

[0001] This invention relates to the field of resistance and inductance detection technology for conductive cables, and particularly to a single-ended impedance detection circuit and method for conductive cables based on switching transients. Background Technology

[0002] Cables used for long-distance power transmission have significant resistance and inductance. Therefore, the input voltage to the load system at the far end of the power supply will be lower than the 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 change 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 large inductance of long-distance cables, the power supply may not respond promptly, potentially causing the load system to malfunction or enter a protection state.

[0003] Existing methods for detecting the impedance of long cables mainly involve connecting a sufficiently large capacitor in parallel at the cable end to achieve a low AC impedance at the load. The voltage change caused by the line resistance is measured by continuously modulating the current to the load system, and the cable resistance value is calculated for voltage drop compensation. 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 system. Summary of the Invention

[0004] The main objective of this invention is to propose a single-ended impedance detection circuit and method for conductive cables based on switching transients, which aims to realize the detection of cable input voltage and cable current at one end of the conductive cable, thereby obtaining the resistance and self-inductance parameters of the cable.

[0005] To achieve the above objectives, the present invention provides a single-ended impedance detection circuit for conductive cables based on switching transients, comprising: a power supply, a switch S, an auxiliary resistor Raux, an equivalent resistance Rc of the cable, an equivalent self-inductance Lc of the cable, a filter capacitor Caux, and a load or a secondary power supply.

[0006] Wherein, one end of the switch S is connected to the power supply, and the other end is connected to one end of the auxiliary resistor Raux and one end of the cable equivalent resistance Rc. The other end of the auxiliary resistor Raux is connected to one end of the power supply, the load or secondary power supply, and the filter capacitor Caux. The other end of the cable equivalent resistance Rc is connected to one end of the cable equivalent inductance Lc. The other end of the cable equivalent inductance Lc is connected to the other end of the filter capacitor Caux and the load or secondary power supply.

[0007] A further technical solution of the present invention is that, when the power supply is working normally and supplying power to the load or secondary power supply, the switch S is in a normally open state. During the 0-t1 stage, the loop formed by the auxiliary resistor Raux, the equivalent resistance Rc of the cable, the equivalent self-inductance Lc of the cable, and the filter capacitor Caux is in a steady state, and the following relationship exists:

[0008] (1)

[0009] When it is necessary to test the cable impedance parameter, the switch S is opened. At the moment of opening, the capacitor Caux discharges to the cable impedance and the auxiliary resistor Raux. Due to the effect of the filter capacitor Caux at the end of the cable, the voltage at the load or secondary power supply terminal decreases. V L No sudden changes will occur. Due to fluctuations in cable current, transient voltage spikes exist in the cable inductance. At time t2, a loop consisting of Raux, Rc, Lc, and Caux exists with the following relationship:

[0010] (2)

[0011] At time t3, the switch S is still in the open state, and the cable current gradually stabilizes. At this time, the rate of change of current is 0, so the cable inductor voltage is 0. When the capacitance of the filter capacitor Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the voltage at the load or secondary power supply terminal is... V L The change in can be considered as 0. At this point, the loop consisting of Raux, Rc, Lc, and Caux is in a steady state, and the following relationship exists:

[0012] (3)

[0013] in, v o1 , v o2 , v o3 The voltage at the source end of the cable at times t1, t2, and t3 are respectively. i cable1 , i cable2 , i cable3 The cable currents at times t1, t2, and t3 are respectively. di cable2 / dt Let t2 be the rate of change of cable current.

[0014] To achieve the above objectives, the present invention also proposes a method for single-ended impedance detection of conductive cables based on switching transients. This method is applied to the single-ended impedance detection circuit for conductive cables based on switching transients as described in the above embodiment. The method includes the following steps:

[0015] Step S10: Add the auxiliary switch S and the auxiliary resistor Raux to the output terminal of the power supply;

[0016] Step S20: At time t1, close the switch S and sample the voltage at the source end of the cable. v o1 and cable current i cable1 Relationship (1) is obtained:

[0017] (1);

[0018] In step S30, at time t2, the switch S is opened. At the instant of opening, capacitor Caux discharges to the cable impedance and resistance Raux. Due to the effect of the filter capacitor at the end of the cable, the load system terminal voltage... V L No sudden changes will occur. Due to fluctuations in cable current, transient voltage spikes will appear in the cable inductance. At this time, the source voltage of the sampled cable will be... v o2 and cable current i cable2 Obtain the cable current change rate di cable2 / dt Formula (2) is obtained:

[0019] (2)

[0020] In step S40, at time t3, switch S remains open, and the cable current gradually stabilizes. At this point, the rate of change of current is 0, therefore the cable inductance voltage is 0. When the capacitance value of Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the load system terminal voltage... V L The change can be considered as 0, at which point the voltage at the source end of the sampling cable is zero. v o3 and cable current i cable3 Thus, we obtain formula (3);

[0021] (3)

[0022] Step S50: Combine formulas (1) to (3) to solve for the equivalent resistance Rc and equivalent self-inductance Lc of the cable.

[0023] The beneficial effects of this invention, based on a single-ended impedance detection circuit and method for conductive cables under switching transients, are:

[0024] 1. This invention can accurately obtain the real-time resistance and self-inductance of a cable simply by adding an auxiliary switch and an auxiliary resistor. The logic is simple and easy to implement.

[0025] 2. This invention enables accurate detection of the impedance of a conductive cable at only one end of a long cable.

[0026] 3. This invention can solve the problem of undervoltage in the load system caused by resistance voltage drop of long-distance cables. It can achieve precise control of the voltage at the end of the cable, without the need for external long cables to detect the input voltage of the load system, and has no impact on the load system.

[0027] 4. This invention solves the problem of the influence of long-distance cable inductance on system dynamics, solves the problem of cable voltage delay response, and avoids load system failure.

[0028] 5. This invention can be applied to any power supply system, and is not limited by the type of front-end power supply or the circuit structure of the load system, thus having universality. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the circuit structure of the single-ended impedance detection circuit for conductive cables based on switching transients of the present invention.

[0031] Figure 2 This is the timing diagram of the single-ended impedance detection circuit for conductive cables based on switching transients of the present invention.

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Please refer to Figure 1 This invention proposes a single-ended impedance detection circuit for conductive cables based on switching transients. This invention is applicable to detecting the resistance and inductance of conductive cables of any material, length, and diameter. The technical solution employed in this invention mainly involves adding an auxiliary switch and a parallel resistor to detect the voltage at the cable input end and the cable current, thereby obtaining the cable's resistance and inductance parameters.

[0035] Specifically, such as Figure 1 As shown, a preferred embodiment of the single-ended impedance detection circuit for conductive cables based on switching transients of the present invention includes a power supply, a switch S, an auxiliary resistor Raux, an equivalent resistance Rc of the cable, an equivalent self-inductance Lc of the cable, a filter capacitor Caux, and a load or secondary power supply. Figure 1 middle, v o The voltage at the source end of the cable. v L This refers to the load terminal voltage or the secondary power supply input voltage (i.e., the voltage at the end of the cable). i cable This represents the current flowing through the cable.

[0036] Wherein, one end of the switch S is connected to the power supply, and the other end is connected to one end of the auxiliary resistor Raux and one end of the cable equivalent resistance Rc. The other end of the auxiliary resistor Raux is connected to one end of the power supply, the load or secondary power supply, and the filter capacitor Caux. The other end of the cable equivalent resistance Rc is connected to one end of the cable equivalent inductance Lc. The other end of the cable equivalent inductance Lc is connected to the other end of the filter capacitor Caux and the load or secondary power supply.

[0037] Please refer to Figure 2 , Figure 2 This is the timing diagram of the single-ended impedance detection circuit for conductive cables based on switching transients, which is the working principle of this invention.

[0038] This invention adds the auxiliary switch S and the auxiliary resistor Raux in parallel to the output side of the power supply. When the power supply is working normally and supplying power to the load or secondary power supply, the switch S is in the normally open state. Figure 2 In the 0-t1 stage shown, the loop consisting of the auxiliary resistor Raux, the equivalent cable resistance Rc, the equivalent cable inductance Lc, and the filter capacitor Caux is in a steady state, and the following relationship exists:

[0039] (1)

[0040] When it is necessary to test the cable impedance parameter, the switch S is opened. At the moment of opening, the capacitor Caux discharges to the cable impedance and the auxiliary resistor Raux. Due to the effect of the filter capacitor Caux at the end of the cable, the voltage at the load or secondary power supply terminal decreases. V L There will be no sudden changes; however, due to fluctuations in cable current, transient voltage spikes may occur in the cable inductance, such as... Figure 2 As shown at time point t2, the loop consisting of Raux, Rc, Lc, and Caux has the following relationship:

[0041] (2)

[0042] At time t3, the switch S is still in the open state, and the cable current gradually stabilizes. At this time, the rate of change of current is 0, so the cable inductor voltage is 0. When the capacitance of the filter capacitor Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the voltage at the load or secondary power supply terminal is... V L The change in can be considered as 0. At this point, the loop consisting of Raux, Rc, Lc, and Caux is in a steady state, and the following relationship exists:

[0043] (3)

[0044] in, v o1 , v o2 , v o3 The voltage at the source end of the cable at times t1, t2, and t3 are respectively. i cable1 , i cable2 , i cable3 The cable currents at times t1, t2, and t3 are respectively. di cable2 / dt The current change rate at time t2 is given. These parameters can be obtained by sampling the voltage and current at the cable source.

[0045] In summary, by combining equations (1) to (3), the values ​​of the equivalent resistance Rc and the equivalent self-inductance Lc of the cable can be obtained.

[0046] The beneficial effects of this invention, based on a single-ended impedance detection circuit for conductive cables during switching transients, are:

[0047] 1. This invention can accurately obtain the real-time resistance and self-inductance of a cable simply by adding an auxiliary switch and an auxiliary resistor. The logic is simple and easy to implement.

[0048] 2. This invention enables accurate detection of the impedance of a conductive cable at only one end of a long cable.

[0049] 3. This invention can solve the problem of undervoltage in the load system caused by resistance voltage drop of long-distance cables. It can achieve precise control of the voltage at the end of the cable, without the need for external long cables to detect the input voltage of the load system, and has no impact on the load system.

[0050] 4. This invention solves the problem of the influence of long-distance cable inductance on system dynamics, solves the problem of cable voltage delay response, and avoids load system failure.

[0051] 5. This invention can be applied to any power supply system, and is not limited by the type of front-end power supply or the circuit structure of the load system, thus having universality.

[0052] To achieve the above objectives, the present invention also proposes a method for single-ended impedance detection of conductive cables based on switching transients. This method is applied to the single-ended impedance detection circuit for conductive cables based on switching transients as described in the above embodiment. The method includes the following steps:

[0053] Step S10: Add the auxiliary switch S and the auxiliary resistor Raux to the output terminal of the power supply;

[0054] Step S20: At time t1, close the switch S and sample the voltage at the source end of the cable. v o1 and cable current i cable1 Relationship (1) is obtained:

[0055] (1);

[0056] In step S30, at time t2, the switch S is opened. At the instant of opening, capacitor Caux discharges to the cable impedance and resistance Raux. Due to the effect of the filter capacitor at the end of the cable, the load system terminal voltage... V L No sudden changes will occur. Due to fluctuations in cable current, transient voltage spikes will appear in the cable inductance. At this time, the source voltage of the sampled cable will be... v o2 and cable current i cable2 Obtain the cable current change rate di cable2 / dt Formula (2) is obtained:

[0057] (2)

[0058] In step S40, at time t3, switch S remains open, and the cable current gradually stabilizes. At this point, the rate of change of current is 0, therefore the cable inductance voltage is 0. When the capacitance value of Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the load system terminal voltage... V L The change can be considered as 0, at which point the voltage at the source end of the sampling cable is zero. v o3 and cable current i cable3 Thus, we obtain formula (3);

[0059] (3)

[0060] Step S50: Combine formulas (1) to (3) to solve for the equivalent resistance Rc and equivalent self-inductance Lc of the cable.

[0061] The beneficial effects of this invention, which uses a single-ended impedance detection method for conductive cables based on switching transients, are:

[0062] 1. This invention can accurately obtain the real-time resistance and self-inductance of a cable simply by adding an auxiliary switch and an auxiliary resistor. The logic is simple and easy to implement.

[0063] 2. This invention enables accurate detection of the impedance of a conductive cable at only one end of a long cable.

[0064] 3. This invention can solve the problem of undervoltage in the load system caused by resistance voltage drop of long-distance cables. It can achieve precise control of the voltage at the end of the cable, without the need for external long cables to detect the input voltage of the load system, and has no impact on the load system.

[0065] 4. This invention solves the problem of the influence of long-distance cable inductance on system dynamics, solves the problem of cable voltage delay response, and avoids load system failure.

[0066] 5. This invention can be applied to any power supply system, and is not limited by the type of front-end power supply or the circuit structure of the load system, thus having universality.

[0067] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A single-ended impedance detection circuit for conductive cables based on switching transients, characterized in that, include: Power supply, auxiliary switch S, auxiliary resistor Raux, cable equivalent resistance Rc, cable equivalent self-inductance Lc, filter capacitor Caux, load or secondary power supply; Wherein, one end of the auxiliary switch S is connected to the power supply, and the other end is connected to one end of the auxiliary resistor Raux and one end of the cable equivalent resistance Rc. The other end of the auxiliary resistor Raux is connected to one end of the power supply, the load or secondary power supply, and the filter capacitor Caux. The other end of the cable equivalent resistance Rc is connected to one end of the cable equivalent inductance Lc. The other end of the cable equivalent inductance Lc is connected to the other end of the filter capacitor Caux and the load or secondary power supply. The auxiliary switch S remains normally open when the power supply is supplying the load or the secondary power supply is supplying power normally. It only performs a disconnection action once when it is necessary to detect the cable impedance, so as to trigger a transient discharge circuit composed of the auxiliary resistor Raux, the cable equivalent resistance Rc, the cable equivalent self-inductance Lc, and the filter capacitor Caux. The transient changes in voltage and current generated at the source end by the transient discharge circuit are combined with the steady-state sampling value to solve for the cable equivalent resistance Rc and the cable equivalent self-inductance Lc.

2. The single-ended impedance detection circuit for conductive cables based on switching transients according to claim 1, characterized in that, When the power supply is working normally and supplying power to the load or secondary power supply, the switch S is normally open. During the 0-t1 stage, the loop formed by the auxiliary resistor Raux, the equivalent resistance of the cable Rc, the equivalent self-inductance of the cable Lc, and the filter capacitor Caux is in a steady state, and the following relationship exists: （1） When it is necessary to test the cable impedance parameter, the switch S is opened. At the moment of opening, the capacitor Caux discharges to the cable impedance and the auxiliary resistor Raux. Due to the effect of the filter capacitor Caux at the end of the cable, the voltage at the load or secondary power supply terminal decreases. V L No sudden changes will occur. Due to fluctuations in cable current, transient voltage spikes exist in the cable inductance. At time t2, a loop consisting of Raux, Rc, Lc, and Caux exists with the following relationship: （2） At time t3, the switch S is still in the open state, and the cable current gradually stabilizes. At this time, the rate of change of current is 0, so the cable inductor voltage is 0. When the capacitance of the filter capacitor Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the voltage at the load or secondary power supply terminal is... V L The change in can be considered as 0. At this point, the loop consisting of Raux, Rc, Lc, and Caux is in a steady state, and the following relationship exists: （3） in, v o1 , v o2 , v o3 The voltage at the source end of the cable at times t1, t2, and t3 are respectively. i cable1 , i cable2 , i cable3 The cable currents at times t1, t2, and t3 are respectively. di cable2 / dt Let t2 be the rate of change of cable current.

3. A method for single-ended impedance detection of conductive cables based on switching transients, characterized in that, The method is applied to the single-ended impedance detection circuit of conductive cables based on switching transients as described in any one of claims 1 or 2, and the method includes the following steps: Step S10: Add the auxiliary switch S and the auxiliary resistor Raux to the output terminal of the power supply; Step S20: At time t1, close the switch S and sample the voltage at the source end of the cable. v o1 and cable current i cable1 Relationship (1) is obtained: （1）； Step S30: At time t2, the switch S is opened. At the instant of opening, capacitor Caux discharges to the cable impedance and resistance Raux. Due to the effect of the filter capacitor at the end of the cable, the load system terminal voltage... V L No sudden changes will occur. Due to fluctuations in cable current, transient voltage spikes will appear in the cable inductance. At this time, the source voltage of the sampled cable will be... v o2 and cable current i cable2 Obtain the cable current change rate di cable2 / dt Formula (2) is obtained: （2） In step S40, at time t3, switch S remains open, and the cable current gradually stabilizes. At this point, the rate of change of current is 0, therefore the cable inductance voltage is 0. When the capacitance value of Caux is large enough to decouple the load or secondary power supply from the front-end circuit, the load system terminal voltage... V L The change can be considered as 0, at which point the voltage at the source end of the sampling cable is zero. v o3 and cable current i cable3 Thus, we obtain formula (3); （3） Step S50: Combine formulas (1) to (3) to solve for the equivalent resistance Rc and equivalent self-inductance Lc of the cable.

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