Common-mode leakage current suppression method based on non-contact annular induction coil and passive damping equipment

Abstract

The invention discloses a common-mode leakage current suppression method based on a non-contact annular induction coil and passive damping equipment, relates to the technical field of electric power and the field of electric power driving, and mainly aims to solve the problem of low accuracy of existing common-mode leakage current suppression. The method mainly comprises the following steps of: after an annular induction coil in the passive damping equipment is coaxially arranged on the periphery of a common-mode through-flow conductor to be detected of a target electric drive system in a non-contact surrounding manner, inducing an alternating magnetic field generated by high-frequency common-mode leakage current flowing through the common-mode through-flow conductor to be detected through the annular induction coil; the induced alternating magnetic field is converted into induced voltage applied to the two ends of the damping loop; induced current flowing through the circuit is consumed through a damping loop so as to restrain high-frequency common-mode leakage current, and configuration parameters of the passive damping device are obtained according to transfer function optimization of a target electric drive system. The method is mainly used for suppressing common-mode leakage current.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology and can be applied to the field of electric drive, in particular to a common-mode leakage current suppression method based on a non-contact annular induction coil and a passive damping device. Background Art

[0002] Common-mode leakage current is a significant issue in electric drive system operation. It can not only flow back through motor bearings, shielded cables, or ground wires, leading to reliability issues such as bearing corrosion and insulation degradation, but can also cause electromagnetic interference (EMI) to nearby communications equipment, reducing the system's electromagnetic compatibility. Therefore, appropriate measures must be taken to suppress common-mode leakage current.

[0003] Currently, passive filters, consisting of passive components such as common-mode chokes and capacitors, are primarily used to suppress common-mode leakage current. Compared to traditional active filters, passive filters offer the advantages of simpler structure and lower cost, effectively suppressing common-mode interference within a specific frequency band. However, passive filters often need to be integrated into the main circuit of the electric drive system, resulting in large size and weight. Furthermore, their fixed device parameters make them difficult to accurately adapt to the characteristics of the electric drive system, leading to low accuracy in suppressing common-mode leakage current. Summary of the Invention

[0004] In view of this, the present invention provides a common-mode leakage current suppression method and a passive damping device based on a non-contact annular induction coil, the main purpose of which is to solve the problem of low accuracy of existing common-mode leakage current suppression.

[0005] According to one aspect of the present invention, a method for suppressing common-mode leakage current based on a non-contact annular induction coil is provided, comprising:

[0006] The method suppresses common-mode leakage current based on a passive damping device of a non-contact annular induction coil, wherein the passive damping device includes an annular induction coil and a damping loop, and two ends of the annular induction coil are connected to two ends of the damping loop. The method includes:

[0007] Constructing a transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system, and optimizing the transfer function based on the structural parameters of the preselected induction coil to obtain configuration parameters of the passive damping device, wherein the transfer function is used to characterize the effect of the damping ratio of the target electric drive system on suppressing the common-mode leakage current;

[0008] Constructing a passive damping device according to the number of turns of the induction coil and the damping loop configuration parameters in the configuration parameters;

[0009] After the annular induction coil in the passive damping device is coaxially and non-contactly mounted around the periphery of the common-mode current conductor to be measured of the target electric drive system, the annular induction coil is used to induce an alternating magnetic field generated by a high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop;

[0010] The damping loop consumes the inductive current flowing through the circuit to suppress the high-frequency common-mode leakage current.

[0011] Furthermore, the common-mode electrical parameters include common-mode voltage and common-mode current, and constructing the transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system includes:

[0012] Taking a single-turn induction coil as an assumption, a common-mode equivalent circuit model is constructed according to Ampere's loop law and the principle of induced magnetic flux.

[0013] The common-mode equivalent circuit model is decoupled, and a transfer function is constructed with the common-mode voltage of the target electric drive system as input and the common-mode current as output.

[0014] Furthermore, the common-mode equivalent circuit model is constructed based on the Ampere loop law and the principle of induced magnetic flux, assuming a single-turn induction coil as the object, including:

[0015] According to the differential form of Ampere's loop law, assuming a single-turn induction coil, the mutual conversion relationship between common-mode leakage current and magnetic field is constructed;

[0016] Approximating the cross section of the single-turn induction coil to a rectangular cross section, and deducing the total magnetic flux passing through the single-turn induction coil based on the mutual conversion relationship between the common-mode leakage current and the magnetic field;

[0017] determining the induced electromotive force of the single-turn induction coil, the mutual inductance between the coil and the conductor, and the self-inductance of the coil according to the total magnetic flux;

[0018] A common-mode equivalent circuit model is constructed according to the induced electromotive force, the mutual inductance between the coil and the conductor, and the self-inductance of the coil.

[0019] Furthermore, the parameter optimization of the transfer function is performed based on the structural parameters of the preselected induction coil to obtain the configuration parameters of the passive damping device, including:

[0020] Initializing the transfer function with structural parameters of the preselected annular induction coil to obtain an initialized transfer function, wherein the structural parameters include coil inner diameter, coil outer diameter, coil cross-sectional thickness, and coil cross-sectional height;

[0021] The number of coil turns and the damping resistance of the preselected annular induction coil are used as variables, and the maximum damping ratio is used as the optimization target. The initialized transfer function is iteratively optimized to obtain the damping loop configuration parameters and the number of coil turns.

[0022] Furthermore, the damping circuit configuration parameters include a damping resistor and a series capacitor, and the passive damping device is constructed according to the number of turns of the induction coil and the damping circuit configuration parameters in the configuration parameters, including:

[0023] Configuring the number of preselected induction coils according to the number of coil turns to obtain a ring-shaped induction coil;

[0024] Constructing a pure resistance damping network based on the damping resistor, and connecting the pure resistance damping network to the secondary side of the annular induction coil as a damping loop to obtain a pure resistance-based passive damping device; or,

[0025] A pure resistance damping network is constructed based on the damping resistor and the series capacitor, and the pure resistance damping network is connected to the secondary side of the annular induction coil as a damping loop to obtain a passive damping device based on a resistor and a capacitor in series.

[0026] Furthermore, consuming the induced current flowing through the circuit by the damping circuit includes:

[0027] In the case where the damping circuit is a damping network based on pure resistance, the energy induced by the induced voltage is dissipated by resistance;

[0028] In the case where the damping loop is a damping network based on a resistor and a capacitor connected in series, directional attenuation of the common mode frequency is performed through RC resonance.

[0029] Furthermore, the step of converting the induced alternating magnetic field into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop includes:

[0030] capturing the magnetic flux change of the alternating magnetic field by the annular induction coil;

[0031] generating an induced voltage at both ends of the coil according to the change in magnetic flux;

[0032] The damping loop is driven by the induced voltage to generate an induced current in the damping loop.

[0033] According to another aspect of the present invention, there is provided a passive damping device, comprising:

[0034] The passive damping device includes a ring-shaped induction coil and a damping loop, and two ends of the ring-shaped induction coil are connected to two ends of the damping loop;

[0035] The annular induction coil is used to surround the periphery of the common-mode current conductor to be measured installed in the target electric drive system in a coaxial and non-contact manner, so as to sense the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured when the high-frequency common-mode leakage current flows through the common-mode current conductor to be measured, and convert the induced alternating magnetic field into an induced voltage applied to both ends of the damping circuit, so as to generate an induced current in the damping circuit;

[0036] The damping circuit is used to consume the induced current flowing through the circuit during the process of applying the induced voltage to the annular induction coil, so as to suppress the high-frequency common-mode leakage current;

[0037] Among them, the construction process of the passive damping device includes: constructing the transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system, and optimizing the parameters of the transfer function based on the structural parameters of the preselected induction coil to obtain the configuration parameters of the passive damping device. The transfer function is used to characterize the damping ratio in the target electric drive system. The suppression effect on the common-mode leakage current; the passive damping device is constructed based on the number of induction coil turns and the damping loop configuration parameters in the configuration parameters.

[0038] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0039] The present invention provides a common-mode leakage current suppression method and a passive damping device based on a non-contact annular induction coil. In an embodiment of the present invention, a transfer function of a target electric drive system is constructed according to the common-mode electrical parameters of the target electric drive system, and the transfer function is optimized according to the structural parameters of a preselected induction coil to obtain configuration parameters of a passive damping device, wherein the transfer function is used to characterize the damping ratio suppressing effect on the common-mode leakage current in the target electric drive system; a passive damping device is constructed according to the number of induction coil turns and the damping loop configuration parameters in the configuration parameters; and the annular induction coil in the passive damping device is coaxially and non-contactly mounted around the common-mode current conductor to be measured in the target electric drive system. After the periphery, the annular induction coil is used to induce the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current-carrying conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop; the induced current flowing through the circuit is consumed by the damping loop to suppress the high-frequency common-mode leakage current, thereby avoiding the invasive installation of passive damping equipment. At the same time, the passive damping equipment is constructed through precise parameter optimization, which greatly reduces the error caused by inaccurate parameters in traditional common-mode leakage current suppression. At the same time, the common-mode leakage current characteristics can be accurately suppressed, which greatly reduces the suppression deviation and improves the common-mode leakage current suppression effect of the electric drive system.

[0040] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0042] Figure 1 A flow chart of a common-mode leakage current suppression method based on a non-contact annular induction coil provided by an embodiment of the present invention is shown;

[0043] Figure 2 A schematic diagram of the installation structure of a passive damping device provided by an embodiment of the present invention applied to an electric drive system is shown;

[0044] Figure 3 A structural diagram of a non-contact annular induction coil provided by an embodiment of the present invention is shown;

[0045] Figure 4 A cross-sectional view of a non-contact annular induction coil provided by an embodiment of the present invention is shown;

[0046] Figure 5 An equivalent circuit diagram of a contactless annular induction coil provided by an embodiment of the present invention is shown;

[0047] Figure 6 A simplified circuit diagram of a contactless annular induction coil provided by an embodiment of the present invention is shown;

[0048] Figure 7 A common-mode equivalent circuit diagram provided by an embodiment of the present invention is shown;

[0049] Figure 8 A comparison diagram of the simulation of the overall suppression effect of common-mode leakage current provided by an embodiment of the present invention is shown;

[0050] Figure 9 A comparison diagram of a common-mode leakage current detail suppression effect simulation provided by an embodiment of the present invention is shown;

[0051] Figure 10 shows a common-mode leakage current spectrum diagram provided by an embodiment of the present invention;

[0052] Figure 11A schematic diagram of the structural composition of a passive damping device provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0053] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0054] Aiming at the problem of low accuracy of existing common mode leakage current suppression, the embodiment of the present invention provides a common mode leakage current suppression method based on a non-contact annular induction coil, such as Figure 1 As shown, the method includes:

[0055] 101. Construct a transfer function of the target electric drive system according to the common-mode electrical parameters of the target electric drive system, and optimize the transfer function according to the structural parameters of the preselected induction coil to obtain configuration parameters of the passive damping device.

[0056] In an embodiment of the present invention, a passive damping device based on a non-contact annular induction coil suppresses common-mode leakage current. The passive damping device includes an annular induction coil and a damping loop, with the two ends of the annular induction coil connected to the two ends of the damping loop. By surrounding the non-contact annular induction coil around the conductor through which the common-mode leakage current flows in the target electric drive system, the induced alternating common-mode current generates a magnetic field, thereby inducing an induced current in the induction coil, and dissipating the current through an external damping network, thereby achieving passive absorption and high-frequency suppression of the common-mode leakage current in the electric drive system. Among them, the target electric drive system can be an electric drive system in power electronics, motor drive, inverter and other related power equipment. The target electric drive system can be an electric drive system sensitive to high-frequency noise, such as electric vehicles, electrified railways, smart grids, etc. Of course, it can also be any type of electric drive system in power electronics, motor drive, inverter and other related power equipment. By introducing a damping network (pure resistance or a series combination of resistance and capacitance) in the secondary loop of the non-contact annular induction coil. On the basis of ensuring that no external power supply is required, the damping is flexibly adjustable and the leakage current at the resonance point can be accurately suppressed.

[0057] To ensure accurate leakage current suppression, a transfer function is constructed based on the electrical characteristics of the target electric drive system (as reflected by the common-mode electrical parameters) in which the passive damping device is intended to be installed. This transfer function is then optimized based on the structural parameters of the preselected induction coil to determine the passive damping device configuration parameters that match the target electric drive system. The transfer function describes the circuit principle of the hypothetical coil and damping resistor and is used to characterize the damping ratio's effect on common-mode leakage current suppression in the target electric drive system.

[0058] 102. Construct a passive damping device according to the number of turns of the induction coil and the damping loop configuration parameters in the configuration parameters.

[0059] In an embodiment of the present invention, the number of turns of the annular induction coil constituting the passive damping device and the damping loop configuration parameters are determined based on the configuration parameters, thereby selecting electrical components that meet the damping loop configuration parameters to implement the passive damping device. Since the optimization process of the transfer function is the process of finding the number of turns of the induction coil and the damping loop configuration parameters that maximize the system damping ratio, and the maximum system damping ratio represents the best degree of common-mode leakage current suppression under the corresponding parameters. Therefore, the constructed passive damping device is the device with the best suppression effect on the common-mode leakage current of the current target electric drive system, thereby achieving accurate suppression of the common-mode leakage current.

[0060] 103. After the annular induction coil in the passive damping device is coaxially and contactlessly mounted around the periphery of the common-mode current conductor to be measured of the target electric drive system, the annular induction coil is used to induce the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop.

[0061] In the embodiment of the present invention, during the actual operation of the passive damping device, the annular induction coil needs to be installed in a coaxial and non-contact manner around the periphery of the common-mode current-carrying conductor to be tested of the target electric drive system. Figure 2 The figure shows the installation structure diagram of the passive damping device used in the electric drive system. The toroidal induction coil is installed in a "through-the-core" manner on the outside of the common-mode current conductor to be measured in the electric drive system. In the figure, ISN represents the line impedance stabilization network; Inverter represents the inverter; Reference ground represents the reference ground; Non-contact toroidal current sensing coil represents the non-contact toroidal current sensing coil; M represents the motor, P is the positive pole, and N is the negative pole; i a 、i b 、i cRepresents three-phase current (phase a, phase b, and phase c). The common-mode current conductor can be a power input cable or a motor PE line, for example. Since the passive damping device is not electrically connected to the main circuit conductor, it has good non-invasiveness. At the same time, when high-frequency common-mode leakage current exists in the target electric drive system, this current forms an alternating magnetic field around the conductor. The induction coil captures this magnetic flux change and generates an induced voltage across the coil. The induced voltage further drives the induced current in the damping circuit. This current releases energy in the damping element in the damping circuit, indirectly representing the original common-mode leakage current fluctuation.

[0062] 104. Consume the inductive current flowing through the circuit through the damping loop to suppress the high-frequency common-mode leakage current.

[0063] In an embodiment of the present invention, by connecting a damping circuit to the secondary side of the induction coil, the changing common-mode current in the common-mode current conductor to be measured generates an alternating magnetic field, generates an induced electromotive force around the output end of the induction coil, and generates current. The direction of the magnetic flux generated by this current is opposite to the direction of the magnetic flux generated by the primary winding, that is, the common-mode current conductor to be measured, and plays a certain offsetting role, which can effectively reduce the peak value and effective value of the motor leakage current to achieve the dissipation and attenuation of the energy caused by the induced voltage. Since the coil does not require external power supply, it essentially constitutes a passive current-energy converter. When detecting a high-frequency common-mode disturbance signal, its energy can be attenuated in the form of heat dissipation. No additional controller or feedback loop is required, thus achieving structural-functional integration.

[0064] In one embodiment of the present invention, for further explanation and limitation, constructing a transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system includes:

[0065] Taking a single-turn induction coil as an assumption, a common-mode equivalent circuit model is constructed according to Ampere's loop law and the principle of induced magnetic flux.

[0066] The common-mode equivalent circuit model is decoupled, and a transfer function is constructed with the common-mode voltage of the target electric drive system as input and the common-mode current as output.

[0067] In this embodiment of the present invention, it is assumed that the conductor passing through the annular induction coil in the passive damping device is one turn, and that the magnetic field strength within the coil is uniform everywhere. A common-mode equivalent circuit model is then constructed based on Ampere's loop law and the principle of induced magnetic flux. After the common-mode equivalent circuit model is constructed, the model is decoupled, and a transfer function is constructed using the common-mode voltage in the common-mode electrical parameters as input and the common-mode current in the common-mode electrical parameters as output.

[0068] It should be noted that by constructing an equivalent circuit model and converting the magnetic coupling relationship into circuit parameters such as self-inductance, mutual inductance, coil internal resistance, and equivalent distributed capacitance, the complex electromagnetic coupling system can be converted into a circuit parameter form that is easy to analyze and design, thereby clarifying the coupling relationship between the various components and the impact of damping on common-mode leakage current suppression performance. In addition, through modeling derivation, a calculation basis for the system's frequency response characteristics, damping conditions, and bandwidth range can be obtained. By adjusting and analyzing different parameters (such as the mutual inductance equivalent loop impedance), the impact of the damping network on the common-mode current absorption capacity and energy consumption characteristics can be better evaluated, thus providing a theoretical basis for the subsequent component parameter selection.

[0069] In one embodiment of the present invention, for further explanation and limitation, the common-mode equivalent circuit model is constructed based on the Ampere loop law and the principle of induced magnetic flux, assuming a single-turn induction coil as the object, including:

[0070] According to the differential form of Ampere's loop law, assuming a single-turn induction coil, the mutual conversion relationship between common-mode leakage current and magnetic field is constructed;

[0071] Approximating the cross section of the single-turn induction coil to a rectangular cross section, and deducing the total magnetic flux passing through the single-turn induction coil based on the mutual conversion relationship between the common-mode leakage current and the magnetic field;

[0072] determining the induced electromotive force of the single-turn induction coil, the mutual inductance between the coil and the conductor, and the self-inductance of the coil according to the total magnetic flux;

[0073] A common-mode equivalent circuit model is constructed according to the induced electromotive force, the mutual inductance between the coil and the conductor, and the self-inductance of the coil.

[0074] In the embodiment of the present invention, it is assumed that the wire passing through the Rogowski coil is one turn and the magnetic field strength in the coil is equal everywhere. According to the differential form of Ampere's loop law, the following calculation formula is obtained:

[0075]

[0076] Where H represents the magnetic field strength, represents the line integral of the magnetic field intensity along any closed path, i cm (t) represents the algebraic sum of the currents passing through the area enclosed by the path (where the current varies with time); R represents the distance from the center of the conductor; B represents the magnetic induction intensity, and μ0 represents the magnetic permeability of vacuum.

[0077] The structure of the ring induction coil is as follows Figure 3 As shown, D represents the outer diameter of the coil, d represents the inner diameter of the coil, c represents the cross-sectional thickness of the coil, h represents the cross-sectional height of the coil, and Z secIn order to derive the total magnetic flux through the single-turn induction coil, the cross section of the single-turn induction coil is approximated as a rectangular cross section, as shown in Figure 4 As shown, a rectangular coordinate system is established for it. Here, the equivalent radius R of the toroidal coil is taken as the arithmetic average of D and d, and the cross-sectional area element dS is taken. The magnetic flux passing through dS is double-integrated to obtain the total magnetic flux of the single-turn coil hinge. The total magnetic flux dΦ is expressed by the formula:

[0078]

[0079] After determining the total magnetic flux, the induced electromotive force, the mutual inductance between the coil and the conductor, and the self-inductance of the coil are calculated based on the total magnetic flux. The calculation formula for the induced electromotive force e(t) is expressed as:

[0080]

[0081] Mutual inductance M between coil and conductor coil The calculation formula is expressed as:

[0082]

[0083] Coil self-inductance L coil The calculation formula is expressed as:

[0084]

[0085] Where dΦ represents the total magnetic flux, N represents the number of coil turns, μ r Indicates the relative magnetic permeability of the core.

[0086] After determining the induced electromotive force, the mutual inductance between the coil and the conductor, and the self-inductance of the coil, an equivalent circuit model of the toroidal induction coil is constructed. Figure 5 As shown, where L1 is the conductor self-inductance, M coi1 is the mutual inductance between the coil and the current-carrying wire to be measured, L coil is the coil self-inductance, L total is the total stray inductance, R coil with C coil are the internal resistance and equivalent capacitance of the Rogowski coil respectively. coil with C coil The resistances of the induction coil are in the milliohm and pF levels respectively, which hardly affect the current passing through the coil. Therefore, ignoring the influence of the internal resistance and equivalent capacitance of the induction coil on the current passing through the coil, the equivalent circuit model of the toroidal induction coil is simplified as follows: Figure 6 As shown. coil It is much larger than L1, so the total stray inductance L of the system can be measured totalL1 is replaced as the primary self-inductor. Considering the low coupling coefficient and small mutual inductance of traditional induction coils, which limit energy transfer, a magnetic core material with a relative permeability of 3000 across the 1 kHz to 1 MHz frequency band is used to construct the induction coil bobbin. Furthermore, a common-mode equivalent circuit model is constructed based on the simplified toroidal induction coil equivalent circuit model as part of the common-mode equivalent circuit.

[0087] In one embodiment of the present invention, for further explanation and limitation, the step of optimizing the transfer function based on the structural parameters of the preselected induction coil to obtain the configuration parameters of the passive damping device includes:

[0088] Initializing the transfer function with the structural parameters of the preselected annular induction coil to obtain an initialized transfer function;

[0089] The number of coil turns and the damping resistance of the preselected annular induction coil are used as variables, and the maximum damping ratio is used as the optimization target. The initialized transfer function is iteratively optimized to obtain the damping loop configuration parameters and the number of coil turns.

[0090] In the embodiment of the present invention, in the PWM inverter, the common-mode voltage is defined as the potential difference between the inverter output midpoint and the reference ground. For a three-phase inverter electric drive system, that is, the output voltages of each phase of the inverter are VA, VB, and VC respectively, the common-mode voltage Vcm is (VA+VB+VC) / 3, so we get Figure 7 The common-mode equivalent circuit of the electric drive system is shown in Figure 2. The transfer function is expressed as:

[0091]

[0092] Among them, L total 、C total 、R total are the system stray parameters respectively, and s is the complex variable in Laplace transform.

[0093] Structural parameters include the coil's inner diameter, outer diameter, cross-sectional thickness, and height. These are determined based on the selection of an appropriate coil, specifically the preselected induction coil. Since the system characteristics are determined by the transfer function's damping ratio, to effectively attenuate the RMS value and oscillations of the common-mode leakage current, the damping added to the toroidal coil must gradually increase the system's damping ratio. Therefore, the number of coil turns N and the damping resistor (pure resistance) are set as variables, and the number of coil turns and damping resistance that maximize the system's damping ratio are iteratively determined.

[0094] In one embodiment of the present invention, for further explanation and limitation, the passive damping device is constructed according to the number of turns of the induction coil and the damping circuit configuration parameters in the configuration parameters, including:

[0095] Configuring the number of preselected induction coils according to the number of coil turns to obtain a ring-shaped induction coil;

[0096] Constructing a pure resistance damping network based on the damping resistor, and connecting the pure resistance damping network to the secondary side of the annular induction coil as a damping loop to obtain a pure resistance-based passive damping device; or,

[0097] A pure resistance damping network is constructed based on the damping resistor and the series capacitor, and the pure resistance damping network is connected to the secondary side of the annular induction coil as a damping loop to obtain a passive damping device based on a resistor and a capacitor in series.

[0098] In an embodiment of the present invention, the damping circuit configuration parameters include a damping resistor and / or a series capacitor. The damping circuit can be a pure resistive circuit, that is, a pure resistive damping network. However, when the resistor is converted to the system side, the overall impedance of the system is limited. In order to further weaken the resonance peak and enhance the suppression effect, a capacitor can be connected in series on the basis of the resistor to form a resonant circuit through the capacitor and the annular induction coil, that is, a pure resistive damping network. The resonance point of the resonant circuit should be consistent with the original resonance point of the system, so as to weaken the common-mode leakage current at the resonance point. The capacitance can be calculated based on the following formula:

[0099]

[0100] Among them, C sec Represents a series capacitor.

[0101] In an application example, when the inner diameter of the ring induction coil is 1.5 cm, the outer diameter is 3.1 cm, and the coil thickness is 4 cm, the number of coil turns is 5, and the damping resistance is 818 Ω, the system damping ratio is the largest, 0.187, and the common-mode leakage current suppression is the best. A passive filter circuit based on a contactless ring induction coil was built in LTspice, with a DC voltage source of 100 V and a switching frequency of 10 kHz. The time domain waveforms of the leakage current before and after suppression are shown in the figure below. Figure 8 、 9 , as shown in 10. Figure 8 Shows the comparison of the suppression degree of common mode leakage current under different conditions, original is the original (the horizontal axis is time, the vertical axis is current i cm (t)). When the damping is pure resistance, the searched parameter condition 3 (pure resistance = 818) has the best suppression compared to condition 1 (case 1) (pure resistance = 500) and condition 2 (case 2) (pure resistance = 1000). Condition 4 (case 4) is based on condition 3 and adds a suitable C sec , the suppression is further improved, such as Figure 9 As shown in the figure (the horizontal axis is time, the vertical axis is current icm Under condition 4, the peak value of the common-mode leakage current decreased by 0.44% and the effective value decreased by 23.65%. Figure 10 The common-mode leakage current spectrum before and after suppression is shown (the horizontal axis is frequency, the vertical axis is spectrum magnitude, and dBμA is the relative unit obtained by expressing the current unit of microampere (μA) in decibels (dB) based on a logarithmic scale). Under condition 4, the common-mode leakage current at the resonance point is attenuated by approximately 9dB, verifying the effectiveness of the designed non-contact toroidal induction coil detection-damping structure.

[0102] In one embodiment of the present invention, for further explanation and limitation, consuming the induced current flowing through the circuit by the damping circuit includes:

[0103] In the case where the damping circuit is a damping network based on pure resistance, the energy induced by the induced voltage is dissipated by resistance;

[0104] In the case where the damping loop is a damping network based on a resistor and a capacitor connected in series, directional attenuation of the common mode frequency is performed through RC resonance.

[0105] In an embodiment of the present invention, the damping circuit consumes the induced current flowing through the circuit in two different ways, corresponding to two different damping circuit structures: a damping network based on pure resistance and a damping network based on resistance in series with capacitance. When the induction coil senses the alternating magnetic field generated by the high-frequency common-mode leakage current in the common-mode current-carrying conductor to be measured, and then generates an induced voltage at both ends of the damping circuit, the damping network based on pure resistance mainly relies on the pure resistance of the resistance element therein to consume energy. This way of energy consumption by resistance can effectively suppress high-frequency common-mode leakage current, because the energy of the induced current is consumed by the resistance in the form of heat, so that the amplitude of the common-mode leakage current gradually decreases, reducing its adverse effects on the electric drive system.

[0106] In an AC circuit, the combination of resistors and capacitors forms an RC circuit, which resonates when certain conditions are met. For specific common-mode frequencies, the RC circuit exhibits specific impedance characteristics. Near the resonant frequency, the circuit's impedance changes significantly, resulting in a directional attenuation of the common-mode signal. The directional attenuation of the common-mode frequency by RC resonance enables more targeted suppression of high-frequency common-mode leakage currents at specific frequencies. Compared to simple resistive energy dissipation, RC resonance achieves more efficient suppression at specific frequencies, improving the overall passive damping circuit's ability to suppress common-mode leakage currents and further reducing the potential harm common-mode leakage currents can cause to the electric drive system.

[0107] In one embodiment of the present invention, for further explanation and limitation, converting the induced alternating magnetic field into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop includes:

[0108] capturing the magnetic flux change of the alternating magnetic field by the annular induction coil;

[0109] generating an induced voltage at both ends of the coil according to the change in magnetic flux;

[0110] The damping loop is driven by the induced voltage to generate an induced current in the damping loop.

[0111] In an embodiment of the present invention, when a high-frequency common-mode leakage current flows through a common-mode current-carrying conductor to be tested in a target electric drive system, an alternating magnetic field is generated around the conductor due to the magnetic effect of the current. The annular induction coil is designed to surround the conductor. When the alternating magnetic field passes through the area enclosed by the annular induction coil, the coil can capture the change in magnetic flux of the alternating magnetic field, according to the premonition of Faraday's law of electromagnetic induction (a change in magnetic flux is a prerequisite for generating an induced electromotive force). The change in magnetic flux here refers to the change in the number of magnetic flux lines passing through the area enclosed by the coil per unit time. Based on Faraday's law of electromagnetic induction, when the magnetic flux passing through a closed loop changes, an induced electromotive force is generated in the loop. The annular induction coil can be regarded as a closed loop. When it captures the change in magnetic flux of the alternating magnetic field, an induced electromotive force, or induced voltage, is generated at both ends of the coil. When an induced voltage is generated at both ends of the annular induction coil, the induced voltage is applied to both ends of the damping loop because the damping loop is connected to both ends of the annular induction coil. According to Ohm's law, when components such as resistors are present in a damping loop, induced voltage drives charge to move in a certain direction within the loop, forming an induced current. This induced current flows through the damping loop, dissipating energy through the damping components (such as resistors and capacitors) within the damping loop. This suppresses high-frequency common-mode leakage current, thereby improving the reliability and stability of the electric drive system.

[0112] The present invention provides a common-mode leakage current suppression method based on a non-contact annular induction coil. In an embodiment of the present invention, a transfer function of a target electric drive system is constructed according to the common-mode electrical parameters of the target electric drive system, and the transfer function is optimized according to the structural parameters of a preselected induction coil to obtain configuration parameters of a passive damping device, wherein the transfer function is used to characterize the damping ratio in the target electric drive system. The passive damping device is constructed according to the number of induction coil turns and the damping loop configuration parameters in the configuration parameters; after the annular induction coil in the passive damping device is coaxially and non-contactly mounted around the periphery of the common-mode current-carrying conductor to be measured in the target electric drive system, the passive damping device is constructed. Then, the annular induction coil is used to induce the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current-carrying conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop; the induced current flowing through the circuit is consumed by the damping loop to suppress the high-frequency common-mode leakage current, thereby avoiding the invasive installation of passive damping equipment. At the same time, the passive damping equipment is constructed through precise parameter optimization, which greatly reduces the error caused by inaccurate parameters in traditional common-mode leakage current suppression. At the same time, the common-mode leakage current characteristics can be accurately suppressed, which greatly reduces the suppression deviation and improves the common-mode leakage current suppression effect of the electric drive system.

[0113] Furthermore, as a response to the above Figure 1 The embodiment of the present invention provides a passive damping device, such as Figure 11 As shown, the device includes: a ring-shaped induction coil 31 and a damping circuit 32.

[0114] Furthermore, the damping loop is a damping network based on pure resistance or a damping network based on a resistance and a capacitance in series.

[0115] The present invention provides a passive damping device. In an embodiment of the present invention, a ring-shaped induction coil is coaxially and non-contactly installed around the periphery of the common-mode current conductor to be measured of the target electric drive system. The ring-shaped induction coil is used to induce the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop; the induced current flowing through the circuit is consumed by the damping loop to suppress the high-frequency common-mode leakage current, thereby avoiding the invasive installation of the passive damping device. At the same time, it has the advantages of simple structure, low cost and fast response speed.

[0116] Obviously, those skilled in the art will appreciate that the various modules or steps of the present invention described above can be implemented using a general-purpose computing device, centralized on a single computing device, or distributed across a network of multiple computing devices. Alternatively, they can be implemented using program code executable by a computing device, which can then be stored in a storage device and executed by the computing device. In some cases, the steps shown or described can be performed in a different order than that shown, or can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0117] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A common mode leakage current suppression method based on a non-contact annular induction coil, characterized in that: A passive damping device based on a non-contact annular induction coil suppresses common-mode leakage current, the passive damping device comprising an annular induction coil and a damping loop, wherein two ends of the annular induction coil are connected to two ends of the damping loop, and the method comprises: Constructing a transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system, and optimizing the transfer function based on the structural parameters of the preselected induction coil to obtain configuration parameters of the passive damping device, wherein the transfer function is used to characterize the effect of the damping ratio of the target electric drive system on suppressing the common-mode leakage current; Constructing a passive damping device according to the number of turns of the induction coil and the damping loop configuration parameters in the configuration parameters; After the annular induction coil in the passive damping device is coaxially and non-contactly mounted around the periphery of the common-mode current conductor to be measured of the target electric drive system, the annular induction coil is used to induce an alternating magnetic field generated by a high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured, and the induced alternating magnetic field is converted into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop; The damping loop consumes the inductive current flowing through the circuit to suppress the high-frequency common-mode leakage current.

2. The method according to claim 1, characterized in that The common-mode electrical parameters include common-mode voltage and common-mode current. Constructing the transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system includes: Taking a single-turn induction coil as an assumption, a common-mode equivalent circuit model is constructed according to Ampere's loop law and the principle of induced magnetic flux. The common-mode equivalent circuit model is decoupled, and a transfer function is constructed with the common-mode voltage of the target electric drive system as input and the common-mode current as output.

3. The method according to claim 2, characterized in that The common-mode equivalent circuit model is constructed based on the assumption that a single-turn induction coil is used and in accordance with Ampere's loop law and the principle of induced magnetic flux, including: According to the differential form of Ampere's loop law, assuming a single-turn induction coil, the mutual conversion relationship between common-mode leakage current and magnetic field is constructed; Approximating the cross section of the single-turn induction coil to a rectangular cross section, and deducing the total magnetic flux passing through the single-turn induction coil based on the mutual conversion relationship between the common-mode leakage current and the magnetic field; determining the induced electromotive force of the single-turn induction coil, the mutual inductance between the coil and the conductor, and the self-inductance of the coil according to the total magnetic flux; A common-mode equivalent circuit model is constructed according to the induced electromotive force, the mutual inductance between the coil and the conductor, and the self-inductance of the coil.

4. The method according to claim 3, characterized in that Optimizing the transfer function parameters based on the preselected structural parameters of the induction coil to obtain the configuration parameters of the passive damping device includes: Initializing the transfer function with structural parameters of the preselected annular induction coil to obtain an initialized transfer function, wherein the structural parameters include coil inner diameter, coil outer diameter, coil cross-sectional thickness, and coil cross-sectional height; The number of coil turns and the damping resistance of the preselected annular induction coil are used as variables, and the maximum damping ratio is used as the optimization target. The initialized transfer function is iteratively optimized to obtain the damping loop configuration parameters and the number of coil turns.

5. The method according to claim 1, wherein The damping circuit configuration parameters include a damping resistor and / or a series capacitor. The passive damping device is constructed according to the number of turns of the induction coil and the damping circuit configuration parameters in the configuration parameters, including: Configuring the number of preselected induction coils according to the number of coil turns to obtain a ring-shaped induction coil; Constructing a pure resistance damping network based on the damping resistor, and connecting the pure resistance damping network to the secondary side of the annular induction coil as a damping loop to obtain a pure resistance-based passive damping device; or, A pure resistance damping network is constructed based on the damping resistor and the series capacitor, and the pure resistance damping network is connected to the secondary side of the annular induction coil as a damping loop to obtain a passive damping device based on a resistor and a capacitor in series.

6. The method according to claim 5, characterized in that The consuming the induced current flowing through the circuit by the damping circuit includes: In the case where the damping circuit is a damping network based on pure resistance, the energy induced by the induced voltage is dissipated by resistance; In the case where the damping loop is a damping network based on a resistor and a capacitor connected in series, directional attenuation of the common mode frequency is performed through RC resonance.

7. The method according to claim 1, characterized in that The step of converting the induced alternating magnetic field into an induced voltage applied to both ends of the damping loop to generate an induced current in the damping loop includes: capturing the magnetic flux change of the alternating magnetic field by the annular induction coil; generating an induced voltage at both ends of the coil according to the change in magnetic flux; The damping loop is driven by the induced voltage to generate an induced current in the damping loop.

8. A passive damping device, characterized in that: The passive damping device includes a ring-shaped induction coil and a damping loop, and two ends of the ring-shaped induction coil are connected to two ends of the damping loop; The annular induction coil is used to surround the periphery of the common-mode current conductor to be measured installed in the target electric drive system in a coaxial and non-contact manner, so as to sense the alternating magnetic field generated by the high-frequency common-mode leakage current flowing through the common-mode current conductor to be measured when the high-frequency common-mode leakage current flows through the common-mode current conductor to be measured, and convert the induced alternating magnetic field into an induced voltage applied to both ends of the damping circuit, so as to generate an induced current in the damping circuit; The damping circuit is used to consume the induced current flowing through the circuit during the process of applying the induced voltage to the annular induction coil, so as to suppress the high-frequency common-mode leakage current; Among them, the construction process of the passive damping device includes: constructing the transfer function of the target electric drive system based on the common-mode electrical parameters of the target electric drive system, and optimizing the parameters of the transfer function based on the structural parameters of the preselected induction coil to obtain the configuration parameters of the passive damping device. The transfer function is used to characterize the damping ratio in the target electric drive system. The suppression effect on the common-mode leakage current; the passive damping device is constructed based on the number of induction coil turns and the damping loop configuration parameters in the configuration parameters.

9. The circuit according to claim 8, characterized in that The damping circuit is a damping network based on pure resistance or a damping network based on a resistor and a capacitor in series.

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