Bandwidth adjustable self-integrating rogowski coil device and its building method

Abstract

The application discloses a bandwidth-adjustable self-integration Rogowski coil device, which comprises a Rogowski coil body, an integration inductor and a sampling resistor, and electrical parameters of the integration inductor and the sampling resistor are adjustable; the integration inductor is connected in series with an output end of the Rogowski coil body; and the sampling resistor is connected in series with an output end of the integration inductor. The self-integration circuit is formed by connecting the integration inductor and the sampling resistor in series in the Rogowski coil, the induced signal is directly integrated into a current signal output, and an external complex operational amplifier and other elements are not needed, so that the circuit design is obviously simplified, the stability and reliability of the system are improved, and meanwhile, the integration effect of the device is ensured by determining the value range of the integration inductor and the sampling resistor.

Description

Technical Field

[0001] This invention relates to the field of current sensing and measurement technology, and in particular to a bandwidth-adjustable self-integrating Rogowski coil device and its construction method. Background Technology

[0002] In narrow power supply enclosures where busbars form the main circuitry, traditional current sampling methods present installation difficulties, electromagnetic interference, and safety hazards in high-current, high-frequency applications.

[0003] A Rogowski coil is a coreless current sensor that operates based on Faraday's law of electromagnetic induction. When an alternating current changes in a conductor, the Rogowski coil wound in a closed loop induces a time-varying magnetic flux, thereby generating an induced voltage in the coil.

[0004]

[0005] Where M is the mutual inductance coefficient of the coil, i is the target current, and the induced voltage is proportional to the rate of change of the current. Since there is no iron core, magnetic saturation is avoided, resulting in excellent linearity. It is suitable for measuring both AC current and high-frequency pulse current, measuring current through inductive coupling of the windings without the need for a circuit connection. However, to obtain the target current i(t), a traditional Rogowski coil requires an external integrating circuit to integrate the induced voltage. The main drawbacks of external integrating circuits are as follows:

[0006] (1) External analog integrator circuits usually require the use of multiple components such as operational amplifiers, capacitors, and resistors. This not only increases the complexity of the circuit, but also requires precise parameter matching and debugging. It is easily affected by ambient temperature and device aging, leading to unstable measurements.

[0007] (2) Analog or digital integrating circuits typically require an independent power supply system. Especially when sampling signals in high-voltage circuits, a high-voltage power supply must be provided via isolation devices (such as transformers or optocouplers). This design is difficult to implement in space-constrained equipment and increases system complexity and cost.

[0008] (3) When signal processing and power supply are required, external integration circuits usually require additional space for arrangement, which is difficult to achieve in narrow chassis with busbars as the main line. Summary of the Invention

[0009] This invention aims to at least partially solve one of the technical problems in related art. To this end, one object of this invention is to provide a bandwidth-adjustable self-integrating Rogowski coil device, which significantly simplifies circuit design and improves system stability and reliability.

[0010] In a first aspect, the present invention proposes a bandwidth-adjustable self-integrating Rogowski coil device, comprising a Rogowski coil body and an integrating inductor and a sampling resistor whose electrical parameters are adjustable. The integrating inductor is connected in series with the output terminal of the Rogowski coil body, and the sampling resistor is connected in series with the output terminal of the integrating inductor.

[0011] Preferably, the Rogowski coil body, the integrating inductor, and the sampling resistor are all mounted on a single circuit board, with the Rogowski coil body printed on the circuit board in a spiral arrangement.

[0012] Preferably, a filter capacitor is included, one end of which is connected to the end of the integrating inductor furthest from the sampling resistor, and the other end of which is connected to the end of the sampling resistor furthest from the inductor.

[0013] Secondly, the present invention proposes a method for constructing a bandwidth-adjustable self-integrating Rogowski coil device, which includes any of the above-mentioned bandwidth-adjustable self-integrating Rogowski coil device schemes.

[0014] The transfer functions of the output voltage and input current of the self-integrating Rogowski coil device are as follows:

[0015]

[0016] Where U(s) is the output voltage, I(s) is the input current, M is the mutual inductance coefficient of the coil, s is the variable of the transfer function, and L... c R c and C c These represent the self-inductance, resistance, and distributed capacitance of the coil, respectively, L. s R is the parasitic inductance of the sampling resistor, L1 is the inductance of the external integrating inductor, and R is the inductance of the sampling resistor. s The resistance value of the sampling resistor;

[0017] Select ωL c ≥40(R s +R c );

[0018] Due to the presence of the external integrating inductor, neglecting the distributed capacitance C of the coil... c Under the given conditions, we obtain:

[0019]

[0020] Where i is the target current and i2 is the current generated by the induced electromotive force in the lumped circuit.

[0021] Therefore, the lower cutoff frequency of the self-integrating Rogowski coil device is

[0022] The inductance value of the integrating inductor must satisfy the following conditions: Where f L This is the next cutoff frequency.

[0023] Preferably, the upper cutoff frequency of the self-integrating Rogowski coil device is

[0024] Select ωL s ≤R s ;

[0025] The resistance value of the sampling resistor must satisfy R s ≥2πL s f H .

[0026] Preferably, the sampling resistor is a non-inductive resistor.

[0027] Thirdly, the present invention proposes a power supply chassis with a busbar as the main circuit, which includes any of the above-mentioned bandwidth-adjustable self-integrating Rogowski coil devices.

[0028] Preferably, the self-integrating Rogowski coil device is snapped into the IGBT pin inside the power supply chassis.

[0029] Preferably, the integrating inductor is a shielded inductor.

[0030] The beneficial effects of this invention are:

[0031] (1) By using an integrating inductor and a sampling resistor connected in series in the Rogowski coil to form a self-integrating circuit, the induced signal is directly integrated into the current signal output. This eliminates the need for external complex operational amplifiers and other components, significantly simplifying the circuit design and improving the stability and reliability of the system.

[0032] (2) Through the passive design of the self-integrating circuit, it is driven entirely by the signal induced by the Rogowski coil without the need for an external power supply, which greatly reduces the space occupation and design complexity, making it very suitable for integrated applications in small chassis.

[0033] (3) The range of values ​​for the integrating inductor and the sampling resistor was determined, ensuring the integration effect of the device;

[0034] (4) The structure is compact, and the integration function is directly integrated into the sensor level without the need for additional modular design. It is suitable for installation requirements in small spaces and greatly improves the integrability of the system.

[0035] (5) It has significant advantages in high-voltage environments, high-frequency signal measurement, and integrated applications in narrow spaces, providing a reliable, simple and efficient current measurement solution for high-power power supply systems in complex electromagnetic environments. Attached Figure Description

[0036] In the attached diagram:

[0037] Figure 1 This is a lumped parameter model diagram of the measurement circuit of a bandwidth-adjustable self-integrating Rogowski coil device proposed in this invention;

[0038] Figure 2 This is a lumped parameter model diagram of the measurement circuit after adding a filter capacitor as proposed in this invention;

[0039] Figure 3 The diagram shows the lumped parameter model of the measurement circuit for the existing self-integrating Rogowski coil proposed in this invention.

[0040] Figure 4 The Bode plot of the transfer function obtained by simulating the integral inductance proposed in this invention when it is outside the preset range;

[0041] Figure 5 The diagram shows the coil feedback signal obtained from simulating an integral inductance outside the preset range, as proposed in this invention.

[0042] Figure 6 The Bode plot of the transfer function obtained by simulation of the integral inductor at a preset critical value proposed in this invention;

[0043] Figure 7 The diagram shows the coil feedback signal obtained from the simulation of the integral inductor at a preset critical value, as proposed in this invention.

[0044] Figure 8 The L proposed in this invention s A line graph of amplitude versus time obtained from simulation within a preset range;

[0045] Figure 9 The L proposed in this invention s The Bode plot of the transfer function obtained from simulation within a preset range;

[0046] Figure 10 The L proposed in this invention s A line graph of amplitude versus time obtained from simulations outside the preset range;

[0047] Figure 11 The L proposed in this invention s Bode plot of transfer function obtained from simulation outside the preset range;

[0048] Figure 12The Bode plot of the transfer function obtained from simulation without adding a filter capacitor, as proposed in this invention;

[0049] Figure 13 The Bode plot of the transfer function obtained from simulation with the addition of a filter capacitor as proposed in this invention;

[0050] Figure 14 The diagram shows the coil feedback signal obtained from simulation using the method of adding a filter capacitor as proposed in this invention.

[0051] Figure 15 This is the top-level PCB layout proposed in this invention;

[0052] Figure 16 This is the underlying PCB layout proposed in this invention. Detailed Implementation

[0053] A bandwidth-adjustable self-integrating Rogowski coil device includes a Rogowski coil body, an integrating inductor and a sampling resistor whose electrical parameters are adjustable. The integrating inductor is connected in series with the output terminal of the Rogowski coil body, and the sampling resistor is connected in series with the output terminal of the integrating inductor.

[0054] Clearly, based on the above, by expanding the overall equivalent inductance value through the integrating inductor, the signal bandwidth is optimized. At the same time, by adjusting the network impedance characteristics through the sampling resistor, the integrating inductor and the sampling resistor form an integrating network, which significantly simplifies the circuit design.

[0055] In this embodiment, the Rogowski coil body, integrating inductor, and sampling resistor are all mounted on a single circuit board. The Rogowski coil body is printed on the circuit board in a spiral arrangement, specifically, as shown below. Figure 15 and Figure 16 As shown, Figure 15 and Figure 16 These are the top and bottom layers of the circuit board layout. The upper half of the top and bottom layers are coils, and the lower half are integrating inductors and sampling resistors. The coils form a spiral coil through the wiring of the top and bottom layers and the through holes connecting the top and bottom layers.

[0056] Clearly, based on the above, this device is characterized by its small size and flexible installation.

[0057] In this embodiment, the bandwidth-adjustable self-integrating Rogowski coil device further includes a filter capacitor. One end of the filter capacitor is connected to the end of the integrating inductor furthest from the sampling resistor, and the other end of the filter capacitor is connected to the end of the sampling resistor furthest from the inductor.

[0058] Obviously, based on the above, the interference of high-frequency signals on the device can be effectively suppressed by setting the filter capacitor.

[0059] As another embodiment of this application, this embodiment proposes a method for constructing a bandwidth-adjustable self-integrating Rogowski coil device, which includes any of the above-mentioned bandwidth-adjustable self-integrating Rogowski coil device schemes.

[0060] Reference Figure 3 By equating the self-integrating Rogowski coil to a circuit composed of ideal components, the lumped parameter model of the Rogowski coil measurement circuit can be obtained.

[0061] Where M is the mutual inductance coefficient of the coil, i(t) is the transient large current, and the induced electromotive force e(t) is the dependent variable, which is proportional to the derivative of i(t), with a proportionality constant of M. It is easy to obtain:

[0062]

[0063] Among them, L c R c and C c These represent the self-inductance, resistance, and distributed capacitance of the coil, R. s Let t be the resistance value of the sampling resistor, and u(t) be the voltage induced in the coil.

[0064] In the lumped parameter model of the Rogowski coil, if the value of the terminal sampling resistor is sufficiently small, due to the distributed capacitance C... c Typically very small (pF level), then there is Where ω is the signal frequency, and the capacitor branch is almost open-circuited, when measuring a voltage with a sufficiently fast changing frequency, we have ωL c >>R s +R c At this point, the above formula can be simplified to:

[0065]

[0066] at this time, It can perform self-integration.

[0067] Due to the limitations of its self-integrating operating principle, the operating bandwidth of a Rogowski coil is inherently limited. If different signals need to be measured, the number of turns and area of ​​the coil must be designed to control its self-inductance and resistance. Furthermore, the sampling resistor is not a pure resistor, and its inductance has a significant impact on the coil's performance, severely reducing the measurable bandwidth.

[0068] In the application of this application, due to the limited space of the chassis, the coil needs to be designed to be small enough, and therefore the self-inductance of the coil will also be very small. In this case, it is difficult to design the number of coil turns, area, etc. to control the self-inductance and resistance of the coil. The bandwidth-adjustable self-integrating Rogowski coil device of this application can solve the above problems by using an external integrating inductor.

[0069] The lumped parameter model of the measurement circuit of the self-integrating Rogowski coil device with adjustable bandwidth of the added integrating inductor in this application is as follows: Figure 1 As shown;

[0070] The transfer functions of output voltage and input current can be obtained analytically:

[0071]

[0072] Where U(s) is the output voltage, I(s) is the input current, M is the mutual inductance coefficient of the coil, s is the variable of the transfer function, and L... s L1 is the parasitic inductance of the sampling resistor, and L2 is the inductance of the external integrating inductor.

[0073] For a Rogowski coil to achieve self-integration, it needs to satisfy ωL. c >>R s +R c conditions.

[0074] This application selects ωL c ≥40(R s +R c A good integration result can be obtained, therefore This determines the lower cutoff frequency of the coil. For traditional self-integrating Rogowski coils, measuring current signals with excessively low frequencies (such as square wave signals with excessively wide pulse widths) requires a redesign of the coil structure to increase the coil's self-inductance L. c (Because the resistance value R of the sampling resistor) s and the resistance value R of the coil c None of these can be reduced indefinitely; this not only reduces the versatility of the same Rogowski coil under different measurement conditions, but more seriously, it also increases the coil's self-inductance L. c The self-inductance L of the coil is positively correlated with the coil size. Under the operating conditions required in this paper—where the Rogowski coil needs to be snapped into place within the confined space of a power supply chassis housing containing components such as IGBTs—the coil's self-inductance L... c It has also become a parameter for limiting the cutoff frequency of the coil;

[0075] Therefore, this paper introduces an integrating inductor L1, and then, with the distributed capacitance C also ignored... cIn this case, formula (2) will become:

[0076]

[0077] Where i is the target current and i2 is the current generated by the induced electromotive force in the lumped circuit.

[0078] The cutoff frequency of the self-integrating Rogowski coil device with adjustable inductance bandwidth in this application is therefore changed to... The lower cutoff frequency of the coil can be reduced by increasing the inductance value of the integrating inductor. For a given measurement, the required lower cutoff frequency f... L The inductance value of the integral inductor must meet the following requirements. It should be noted that the sensitivity of the device in this application is... Therefore, the inductance value L1 of the added integrating inductor should not be too large to prevent the sensitivity from being too low.

[0079] In addition, to prevent EMI interference from high current to the inductor, the integrating inductor should be a shielded inductor or installed in a location far away from the busbar or IGBT.

[0080] Specifically, regarding the selection of ωL c ≥40(R s +R c );

[0081] In the simulation experiment:

[0082] When the integrating inductance is too small, it does not conform to ωL c ≥40(R s +R c ):

[0083] The parameters of the coil and circuit are as follows:

[0084] L c =0.1628uH, R c =0.4Ω, L1=1uH, C c =1pF,R s =5Ω, L s =0.05uH

[0085] The Bode plot of the transfer function obtained from the simulation is as follows: Figure 4 As shown, the signal diagram of the coil feedback is as follows: Figure 5 As shown (yellow is the reference signal, green is the coil output signal), it can be seen that there is no integration effect for pulse signals with a width of about 4µs;

[0086] When the magnitude of the integrating inductor reaches the critical value required by this application:

[0087] The parameters of the coil and circuit are as follows:

[0088] L c =0.1628uH, R c =0.4Ω, L1=50uH, C c =1pF,R s =5Ω, L s =0.05uH

[0089] The Bode plot of the transfer function obtained from the simulation is as follows: Figure 6 As shown, the signal diagram of the coil feedback is as follows: Figure 7 As shown (yellow is the reference signal, green is the coil output signal), it can be seen that there is an integration effect for pulse signals with a width of about 4µs.

[0090] In this embodiment, Figure 2 In formula (3), the actual equivalent model of the integrating resistor is L. s and R s The series connection is used because the parasitic parallel capacitance is negligible at the frequency considered in this application. There are two principles limiting the selection of the integrating resistor:

[0091] Firstly, in the design, the lower cutoff frequency of the coil is a relatively fixed value, so The size is also relatively fixed. The sensitivity of the coil depends on... Therefore R s The value relative to R c It should not be too small, otherwise the sensitivity will be too low. Therefore, in selecting the sampling resistor, R needs to be... s >R c；

[0092] Secondly, the parasitic series inductance of the sampling resistor affects the current sampling effect; the higher the frequency, the greater the impact on sampling performance. Therefore, the sampling resistor limits the upper cutoff frequency of the coil. This application selects ωL... s ≤R s A good integration effect can be obtained, so the upper cutoff frequency of the coil in this application can be considered as Therefore, a non-inductive resistor needs to be selected to ensure a high upper cutoff frequency. Generally, a certain series of non-inductive resistors has a maximum inductance value that can be guaranteed by a certain process, while the resistance value is selectable; for a certain measurement, the required upper cutoff frequency f... H The resistance value of the selected sampling resistor must satisfy R s ≥2πL s f H .

[0093] Specifically, regarding the selection of ωL s ≤R s ;

[0094] In the simulation experiment:

[0095] When the parasitic inductance of the sampling resistor is too large, it does not conform to ωL. s ≤R s ;

[0096] The parameters of the coil and circuit are as follows:

[0097] L c =0.1628uH, R c =0.4Ω, L1=50uH, C c =1100pF, R s =5Ω, L s =1uH

[0098] The amplitude versus time graph obtained from the simulation is as follows: Figure 10 As shown (black represents u(t), blue represents i(t)), the Bode plot of the transfer function is as follows. Figure 11 As shown;

[0099] When the parasitic inductance of the sampling resistor is sufficiently small, it conforms to ωL s ≤R s ;

[0100] The parameters of the coil and circuit are as follows:

[0101] L c =0.1628uH, R c =0.4Ω, L1=50uH, C c =1100pF, R s =5Ω, L s =0.05uH

[0102] The amplitude versus time graph obtained from the simulation is as follows: Figure 8 As shown (black represents u(t), blue represents i(t)), the Bode plot of the transfer function is as follows. Figure 9 As shown;

[0103] refer to Figure 8 , Figure 9 , Figure 10 and Figure 11 As can be seen from the Bode plot, when the parasitic inductance of the sampling resistor is too high, the system does not have the characteristic of proportionally amplifying the signal at the target frequency, and the output signal has significant distortion. Only by using a sufficiently small parasitic inductance value for the sampling resistor and significantly reducing Ls can better simulation results be obtained.

[0104] The transfer function and formula (3) of the device with an applied integrating inductor are plotted using a Bode plot, as follows: Figure 12 As shown, the results are as follows:

[0105] It can be observed that once the signal frequency exceeds the upper cutoff frequency determined by the sampling inductance, the amplitude of the transfer function suddenly increases until it reaches the upper cutoff frequency determined by the stray capacitance, at which point it decreases. This is highly detrimental to measurement systems with high-frequency interference signals. Increasing the stray capacitance could cause the amplitude to decrease earlier; however, the stray capacitance of the Rogowski coil is very low and extremely difficult to control during the design process.

[0106] Therefore, this paper adds a filter capacitor to the integrator circuit to solve the above problems. The lumped parameter model of the measurement circuit with the added filter capacitor is as follows: Figure 2 As shown, the simulation experiment is as follows:

[0107] After adding a filter capacitor of appropriate size:

[0108] L c =0.1628uH, R c =0.4Ω, L1=50uH, C c =1100pF, R s =5Ω, L s =0.05uH

[0109] The Bode plot of the transfer function obtained from the simulation is as follows: Figure 13 As shown, the signal diagram of the coil feedback is as follows: Figure 10 As shown (yellow is the reference signal, green is the coil output signal), it can be seen that the addition of the filter capacitor can effectively suppress high-frequency signal interference and reduce glitches in the output waveform.

[0110] As another embodiment of this application, this embodiment proposes a power supply chassis with busbar as the main line body, including any of the above-mentioned bandwidth adjustable self-integrating Rogowski coil devices.

[0111] The self-integrating Rogowski coil device is connected to the IGBT pins inside the power supply chassis.

[0112] Obviously, based on the above, the self-integrating Rogowski coil device of this application is installed in a narrow power supply chassis with the busbar as the main line, which can realize current sampling of the power supply chassis and is not affected by the safety space.

[0113] In this embodiment, the integrating inductor is a shielded inductor, or the integrating inductor is installed in a location away from the busbar or IGBT.

[0114] Clearly, based on the above, this setup can prevent EMI interference from high current to the inductor.

Claims

1. A method for constructing a bandwidth-adjustable self-integrating Rogowski coil device, characterized in that: The device includes a Rogowski coil body, an integrating inductor with adjustable electrical parameters, and a sampling resistor. The integrating inductor is connected in series with the output terminal of the Rogowski coil body, and the sampling resistor is connected in series with the output terminal of the integrating inductor. The transfer function of the output voltage and input current of the self-integrating Rogowski coil device is: ； in, For output voltage, For input current, Let be the mutual inductance coefficient of the coil. For variables passed to the function, , and These are the coil's self-inductance, resistance, and distributed capacitance, respectively. The parasitic inductance value of the sampling resistor. The inductance value of the added integrating inductor. The resistance value of the sampling resistor; Select ; Due to the presence of the external integrating inductor, the distributed capacitance of the coil is neglected. Under the given conditions, we obtain: ； in, For the target current, The current generated by the induced electromotive force in the lumped circuit; Therefore, the lower cutoff frequency of the self-integrating Rogowski coil device is ; The inductance value of the integrating inductor must satisfy the following conditions: ,in This is the next cutoff frequency.

2. The method for constructing a bandwidth-adjustable self-integrating Rogowski coil device according to claim 1, characterized in that: The Rogowski coil body, integrating inductor, and sampling resistor are all mounted on a single circuit board, with the Rogowski coil body printed on the circuit board in a spiral arrangement.

3. The method for constructing a bandwidth-adjustable self-integrating Rogowski coil device according to claim 1, characterized in that: It includes a filter capacitor, one end of which is connected to the end of the integrating inductor furthest from the sampling resistor, and the other end of which is connected to the end of the sampling resistor furthest from the integrating inductor.

4. The method for constructing a bandwidth-adjustable self-integrating Rogowski coil device according to claim 1, characterized in that: The upper cutoff frequency of the self-integrating Rogowski coil device is ; Select ; The resistance value of the sampling resistor must satisfy the following conditions: .

5. The method for constructing a bandwidth-adjustable self-integrating Rogowski coil device according to claim 4, characterized in that: The sampling resistor is a non-inductive resistor.

6. A power supply chassis with busbars as the main circuit body, characterized in that: A method for constructing a bandwidth-adjustable self-integrating Rogowski coil device as described in any one of claims 1 to 3.

7. A power supply chassis with busbars as the main circuit body according to claim 6, characterized in that: The self-integrating Rogowski coil device is connected to the IGBT pin inside the power supply chassis.

8. A power supply chassis with busbars as the main circuit body according to claim 6, characterized in that: The integrating inductor is a shielded inductor.

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