Shielded cable crosstalk suppression performance prediction method and system

Abstract

The invention discloses a method and a system for predicting crosstalk suppression performance of a shielded cable, and belongs to the field of power electronic electromagnetic interference. The method comprises the following steps: acquiring a common-mode interference source and common-mode source impedance of the inverter power supply, establishing a common-mode electromagnetic interference equivalent circuit of the inverter power supply, and combining a cable bundle equivalent circuit to construct a common-mode crosstalk model of a shielding cable in the inverter power supply system; equivalently replacing the distribution parameters between the cables with common coupling impedance, and updating the common-mode crosstalk model based on the common coupling impedance to obtain a shielding cable crosstalk suppression performance prediction model based on the shielding structure and the electromagnetic parameters; and acquiring the common-mode interference current ip on the current power cable of the equivalent circuit, predicting the common-mode crosstalk current of the shielded cable through the prediction model in combination with a preset shielding structure and electromagnetic parameters, and evaluating the crosstalk suppression performance of the shielded cable. The influence of different parameters of the shielded cable on common-mode crosstalk is quantified, and the crosstalk suppression performance of the shielded cable is accurately predicted.

Description

Technical Field

[0001] The present invention belongs to the field of power electronic electromagnetic interference, and more specifically, relates to a method and system for predicting the crosstalk suppression performance of a shielded cable. Background Art

[0002] With the continuous development of transportation electrification, motor drive systems composed of inverters have been widely used in the transportation sector. Inverter power supplies operate based on the pulse-width modulation (PWM) principle, which generates large voltage (dv / dt) and current (di / dt) transitions. The resulting power electronics electromagnetic interference (EMI), rich in high-frequency components, can further aggravate the electromagnetic environment within transportation equipment. Common-mode electromagnetic interference (CM EMI) is the primary component of inverter EMI. Due to confined spaces, power cables and signal cables are often bundled together. This allows CMEMI on the power cables to propagate to the signal cables through near-field coupling between the cables, causing CM cable crosstalk. CM cable crosstalk can hinder the effective transmission of communication signals and threaten the normal operation of sensitive equipment. To ensure the proper operation of the system, measures must be taken to suppress CM cable crosstalk.

[0003] Currently, there are two common methods for suppressing cable crosstalk. The first is to reduce the interference source, such as optimizing the modulation method and adding buffer circuits, or constructing a crosstalk-cancelling signal source using the linear combination of configuration fields (LCCF) method to achieve crosstalk suppression. The second method is to change the crosstalk coupling path, such as increasing the distance between cables to reduce coupling, or using shielded cables to direct the interference to a lower-impedance loop. Shielded cables are widely used as signal cables due to their ease of use. Since the ability of shielded cables to suppress CM cable crosstalk is related to the material and structure of the shielding layer, effective CM cable crosstalk suppression can only be achieved by selecting and even designing shielded cables with appropriate structure and parameters.

[0004] To evaluate the crosstalk suppression performance of shielded cables, transfer impedance, shield attenuation, and shielding effectiveness are commonly used. Shield transfer impedance is the most widely studied and comprehensive. It is defined as the ratio of the induced voltage to the current generated between the outer shield and the inner core when current flows through the shield. The greater the transfer impedance, the poorer the shield's effectiveness. Shield attenuation, defined as the ratio of the power before the shield is applied to the power after the shield is applied, characterizes the shield's crosstalk suppression performance at higher frequencies. The greater the shield attenuation, the better the shield's crosstalk suppression performance. Shielding effectiveness, on the other hand, is the ratio of the electric (magnetic) field strength before the shield is applied to the electric (magnetic) field strength after the shield is applied. The greater the shield attenuation, the better the shield's crosstalk suppression performance. These methods only indirectly assess the magnitude of crosstalk after the shield is applied, based on impedance or field magnitude. This hinders a quantitative description of the relationship between shielding structure and electromagnetic parameters and CM cable crosstalk, making precise suppression difficult.

[0005] In practical applications, different types of shielded cables are used to meet varying crosstalk suppression requirements. However, existing research on crosstalk suppression performance modeling methods for shielded cables cannot directly quantify the relationship between CM cable crosstalk and the shielding structure and electromagnetic parameters of the shielded cable, making it impossible to directly predict and evaluate the crosstalk suppression performance of shielded cables. Currently, there is a lack of relevant theoretical guidance for optimizing the crosstalk suppression performance of shielded cables. There is an urgent need to improve the crosstalk suppression performance modeling methods for shielded cables that quantify the relationship between shielding structure and electromagnetic parameters and CM cable crosstalk. Summary of the Invention

[0006] In view of the shortcomings of the related art, the purpose of the present invention is to provide a method and system for predicting the crosstalk suppression performance of shielded cables, aiming to solve the problem that the existing model cannot directly quantify the relationship between shielding structure and electromagnetic parameters and CM cable crosstalk.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a method for predicting the crosstalk suppression performance of a shielded cable, comprising: S1. Obtaining the common-mode interference source and common-mode source impedance of the inverter power supply, establishing a common-mode electromagnetic interference equivalent circuit of the inverter power supply, and constructing a common-mode crosstalk model of the shielded cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit; S2. Using common coupling impedance to replace the distributed parameters between cables, and updating the common-mode crosstalk model of the shielded cable based on the common coupling impedance, and the crosstalk suppression performance prediction model of the shielded cable based on the shielding structure and electromagnetic parameters; S3, obtaining the common-mode interference current i on the current power cable of the equivalent circuit p, combined with the preset shielding structure and electromagnetic parameters of the shielded cable, the frequency spectrum of the common-mode crosstalk current of the shielded cable is predicted by the shielded cable crosstalk suppression performance prediction model, and the crosstalk suppression performance of the shielded cable is evaluated.

[0008] Optionally, the common mode interference source is a voltage source V CM ; The common-mode source impedance is composed of the ground capacitance of the inverter power supply and the parasitic parameters of the filter.

[0009] Optionally, before S2, also include: When the shielding layer in the cable bundle is grounded at both ends, the shielding layer's ability to suppress inductive coupling is related to its inflection point frequency f SH The relationship is: Among them, R SH is the resistance of the shielding layer, L SH is the self-inductance of the shield; When the predicted frequency of the crosstalk suppression performance of the shielded cable is greater than f SH When the ground loop is considered as an open circuit, the common-mode crosstalk model of the shielded cable is simplified.

[0010] Optionally, the shielded cable crosstalk suppression performance prediction model is: Among them, i p is the common mode interference current on the power cable, is the common mode interference current i on the power cable p Common mode crosstalk current i on the shielded cable core r The transfer function, is the common coupling impedance, is the equivalent common-mode impedance of the communication equipment.

[0011] Optionally, the shielded cable includes a braided shielding layer shielded cable and a tubular shielding layer shielded cable.

[0012] Optionally, the common coupling impedance of the braided shielded cable includes a scattering impedance Z d , Braided inductor M b and hole inductance M h , the expression is: Where j is the imaginary unit, is the angular frequency, Z d Related to shielding structure and electromagnetic parameters, M h and M b All are related to the shielding structure.

[0013] Optionally, the common coupling impedance of the tubular shielded cable is: Where a is the outer radius, T is the thickness of the shielding layer; δ c is the skin depth of the tubular shield, defined as , μ rc and σ c are the relative magnetic permeability and electrical conductivity of the tubular shielding material, respectively.

[0014] Optionally, after S3, also include: Analyze the effect of different parameters of the shielded cable on the crosstalk current i r The importance of determining the dominant influencing parameters in different frequency bands; According to the calculated common mode interference current i p And the corresponding common-mode crosstalk current threshold, calculate the optimized values ​​of the dominant influencing parameters of the shielded cable shielding layer in different frequency bands, and then optimize the design of the shielded cable.

[0015] In a second aspect, the present invention further provides a system for predicting the crosstalk suppression performance of a shielded cable, comprising: A crosstalk model building module is used to obtain the common-mode interference source and common-mode source impedance of the inverter power supply, establish the common-mode electromagnetic interference equivalent circuit of the inverter power supply, and build a common-mode crosstalk model of the shielded cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit; A suppression performance prediction model construction module is used to use common coupling impedance to replace the distributed parameters between cables, and update the common-mode crosstalk model of the shielded cable based on the common coupling impedance to obtain a shielded cable crosstalk suppression performance prediction model based on the shielding structure and electromagnetic parameters; The prediction and evaluation module is used to obtain the common mode interference current i on the current power cable of the equivalent circuit. p , combined with the preset shielding structure and electromagnetic parameters of the shielded cable, the common-mode crosstalk current of the shielded cable is predicted by the shielded cable crosstalk suppression performance prediction model, and the crosstalk suppression performance of the shielded cable is evaluated.

[0016] The above technical solutions conceived by the present invention achieve the following beneficial effects compared to existing technologies: The present invention provides a method for predicting the crosstalk suppression performance of shielded cables. By using the common coupling impedance equivalent to the total impedance of the distributed parameters between cables, this method facilitates the subsequent direct characterization of the relationship between the shielding structure and electromagnetic parameters and CM cable crosstalk. Compared with indirect characterizations of shielded cable crosstalk suppression performance using transfer impedance or shield attenuation, the common coupling impedance representation simplifies the model complexity. Furthermore, based on the common coupling impedance, a circuit model for the crosstalk suppression performance of shielded cables that considers the shielding structure and electromagnetic parameters is proposed. This allows for the derivation of explicit expressions for the shielding structure and electromagnetic parameters and common-mode cable crosstalk, quantifying the impact of different shielded cable parameters on common-mode cable crosstalk. This method achieves accurate prediction of the crosstalk suppression performance of shielded cables and can also accurately and effectively guide the optimization design of the shielding structure and electromagnetic parameters of shielded cables. The proposed modeling method can be applied not only to inverter power systems but also to various power electronics systems, such as rectifier power systems and DC power systems, and has significant practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a method for predicting crosstalk suppression performance of a shielded cable provided in an embodiment of the present invention; Figure 2 This is the CM EMI equivalent circuit of the inverter power supply.

[0018] Figure 3 is the equivalent circuit model of the cable bundle including the shielding layer.

[0019] Figure 4 Simplified prediction model for common-mode cable crosstalk in inverter power systems.

[0020] Figure 5 is the common coupling impedance circuit model of common-mode cable crosstalk; where (a) is the simplified prediction model of common-mode cable crosstalk with the protective ground disconnected; (b) is the common coupling impedance circuit model obtained by replacing the distributed parameters with the common coupling impedance.

[0021] Figure 6 This is a characteristic structure diagram of the braided shielding layer.

[0022] Figure 7 : It is a characteristic structure diagram of the tubular shielding layer; among them, (a) is a side view of the tubular shielding layer; (b) is a front view of the tubular shielding layer.

[0023] Figure 8 Common coupling impedance circuit models using different shielding types; among them, (a) is the common coupling impedance circuit model using a braided shielding layer; (b) is the common coupling impedance circuit model using a braided shielding layer.

[0024] Figure 9 Comparison of model and measured CM cable crosstalk. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0026] Example 1 Due to near-field coupling caused by the interaction of distributed parameters between power and signal cables, EMI on the power cables can couple to the signal cables, resulting in common-mode (CM) cable crosstalk. This can affect signal integrity and even threaten the reliable operation of power electronics systems. Shielded cables are commonly used to suppress CM cable crosstalk. However, existing crosstalk suppression performance modeling methods for shielded cables cannot directly quantify the relationship between CM cable crosstalk and the shielding structure and electromagnetic parameters of the shielded cable, making it difficult to directly predict and evaluate the crosstalk suppression performance of shielded cables.

[0027] In order to solve this problem, a new modeling method for the crosstalk suppression performance of shielded cables considering shielding structure and electromagnetic parameters is proposed based on the common-mode cable crosstalk model of shielded cables in inverter power systems.

[0028] like Figure 1 As shown, an embodiment of the present invention provides a method for predicting the crosstalk suppression performance of a shielded cable, comprising: S1. Obtaining the common-mode interference source and common-mode source impedance of the inverter power supply, establishing a common-mode electromagnetic interference equivalent circuit of the inverter power supply, and constructing a common-mode crosstalk model of the shielded cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit; S2. Using common coupling impedance to replace the distributed parameters between cables, and updating the common-mode crosstalk model of the shielded cable based on the common coupling impedance to obtain a crosstalk suppression performance prediction model of the shielded cable based on the shielding structure and electromagnetic parameters; S3, obtaining the common-mode interference current i on the current power cable of the equivalent circuit p , combined with the preset shielding structure and electromagnetic parameters of the shielded cable, the frequency spectrum of the common-mode crosstalk current of the shielded cable is predicted by the shielded cable crosstalk suppression performance prediction model, and the crosstalk suppression performance of the shielded cable is evaluated.

[0029] The common-mode interference source and source impedance of the inverter power supply are obtained by means of impedance analyzer and oscilloscope, so as to establish the common-mode electromagnetic interference equivalent circuit of the inverter power supply. A cable bundle simulation model is built by using CST cable studio, which includes two single-core power cables (non-shielded cables), one double-core signal cable (shielded cable) and a reference conductor, so as to obtain the distribution parameters between the cables. Firstly, an initial model of CM cable crosstalk prediction of the shielded cable in the inverter power supply system is established, and then a circuit model of the shielded cable crosstalk suppression performance based on the shielding structure and electromagnetic parameters is derived, and the common coupling impedance of different types of shielded cables is obtained by mathematical expression calculation or actual measurement, and finally the explicit expression of the shielding structure and electromagnetic parameters and the CM cable crosstalk is obtained, that is, the final shielded cable crosstalk suppression performance prediction model.

[0030] The above scheme specifically includes the following steps: (1) Establishing a common-mode crosstalk model of shielded cable in inverter power supply The common-mode electromagnetic interference equivalent circuit of the inverter power supply is shown in Figure 2 , the high-speed switching action of the power switch causes a large voltage jump dv / dt at the midpoint of the bridge arm, and a common-mode interference current i p is induced through the parasitic capacitance of the power module. Part of the current flows to the AC meter through the AC cable and the filter, and flows back to the ground plane through the parasitic capacitance of the load; the other part flows to the line impedance stabilization network (LISN) through the DC cable, and finally flows back to the ground loop. The function of LISN is to isolate the interference introduced by the DC power supply, and to simulate the impedance of the power grid side as a reference for the measurement of common-mode interference of the target device.

[0031] Based on the substitution theorem, the common-mode interference source is a voltage source V CM , as shown in equation (1), wherein U a , U b and U c are the voltages across the lower tubes of phase A, phase B and phase C respectively. The common-mode source impedance Z CM is composed of the ground capacitance of the inverter power supply and the parasitic parameters of the filter, as shown in equation (2), wherein Z BUS is the total impedance of the upper bridge arm switch tube 3C C and the lower bridge arm switch tube 3C E of the three-phase upper bridge arm, Z O is the total impedance of 3C O , Z ACind is the total impedance of the AC filter inductance and its parasitic parameters, and Z load is the total impedance of the AC load impedance and its ground capacitance.

[0032] (1) (2) Based on the multi-conductor transmission line (MTL) theory, the positive and negative wires of the shielded cable, the shielding layer, and the positive and negative wires of the power cable are numbered from 1 to 5 (i, j∈[1,5]). Using CST cablestudio to obtain the distribution parameters between the cables, the corresponding cable bundle equivalent circuit model can be established, as shown in the following example: Figure 3 As shown. Among them, L ii and C ii is the self-inductance and self-capacitance of each conductor, M ij(i≠j) and C ij(i≠j) are the mutual inductance and mutual capacitance between the conductors respectively. In addition, Z pe is the impedance of the ground plane.

[0033] Since CM cable crosstalk mainly occurs between power cables and signal cables, and the CM EMI on the positive and negative lines of the power cable are the same, the CM cable crosstalk on the positive and negative lines of the signal cable is also the same, so the positive and negative lines of the power cable can be combined and equivalent to one conductor, and the same is true for the positive and negative lines of the signal cable. Therefore, based on the inverter power supply common mode electromagnetic interference equivalent circuit and the cable bundle equivalent circuit, a simplified model of CM cable crosstalk in the inverter power supply system can be obtained, as shown in the figure below: Figure 4 As shown. Among them, Z LISN / 2 is half of the LISN impedance, Z com_device L is the equivalent common mode impedance of the communication equipment. 1,1 、L 2,1 、L 3,1 are the equivalent self-inductance of the power cable core, shielded cable core and shielding layer, respectively, C 12,2 and M 12,2 are the mutual capacitance and mutual inductance between the power cable and the shield layer, respectively, which are equal to the parallel value of the relevant parameters. 23,2 Is the equivalent mutual inductance between the shielding layer and the shielded cable core, equal to M 13 and M 23 The parallel value of is shown in formula (3).

[0034] (3) (2) Prediction model of crosstalk suppression performance of shielded cables based on shielding structure and electromagnetic parameters Before building a predictive model, it also includes: When the shielding layer in the cable bundle is grounded at both ends, the shielding layer's ability to suppress inductive coupling is related to its inflection point frequency f SH The inflection point frequency f SH Expression As shown in formula (4): (4) Among them, R SH is the resistance of the shielding layer, L SH is the self-inductance of the shield; When the predicted frequency of the crosstalk suppression performance of the shielded cable is greater than f SH When the shielding layer provides an interference flow path with an impedance smaller than the ground loop impedance, the common-mode interference current i p The current mainly returns through the shielding layer. At this time, the common-mode crosstalk current on the core wire of the shielded cable also returns through the shielding layer, thereby simplifying the common-mode crosstalk model of the shielded cable by considering the ground loop as a break.

[0035] The power line conducted emission test item CE102 of the "Requirements and Measurements for Electromagnetic Emissions and Susceptibility of Military Equipment and Subsystems" specifies the electromagnetic standards for power lines in the frequency band of 10kHz to 10MHz. The CM cable crosstalk focuses on the frequency band greater than 10kHz, and the typical value of the inflection point frequency of the shielded cable is around 3kHz. Therefore, the crosstalk frequency band to be analyzed is mainly concentrated in the frequency band greater than f SH frequency band. When the frequency is greater than f SH When the shielding layer can provide an interference flow path with a smaller impedance than the ground loop, the common mode interference current i p The return current mainly flows through the shield layer, not the ground loop. The same is true for the CM cable crosstalk current on the signal cable. Therefore, the current on the ground loop is almost zero, and the ground loop can be regarded as an open circuit. At this time, the simplified CM cable crosstalk prediction model is as follows: Figure 5 In order to more conveniently describe the characteristics of CM cable crosstalk, establish the relationship between shielding structure and electromagnetic parameters and CM cable crosstalk, and propose common coupling impedance to replace the distributed parameters between cables. The distributed parameters between cables refer to the distributed parameters between the power cable core wire, shielded cable core wire and shielding layer, which can be expressed as Figure 5 L in (a) 1,1 、L 2,1 、L 3,1 、M 12,1 、M 23,2 and C 12,2 The total impedance is thus established as Figure 5 Figure (b) shows the CM cable crosstalk common coupling impedance prediction model. This model is identical to the equivalent circuit model used to measure shield impedance, so the common coupling impedance is equal to the shield impedance, which in turn is related to the shield structure and electromagnetic parameters.

[0036] Furthermore, the common coupling impedance can be mathematically expressed through the shielding structure and electromagnetic parameters. Based on the common coupling impedance, the common-mode crosstalk model of the shielded cable is updated, and circuit deduction is performed to obtain a shielded cable crosstalk suppression performance prediction model related to the shielding structure and electromagnetic parameters.

[0037] The crosstalk suppression performance prediction model of the shielded cable is: Among them, i p is the common mode interference current on the power cable, is the common mode interference current i on the power cable p Common mode crosstalk current i on the shielded cable core r The transfer function, is the common coupling impedance, is the equivalent common-mode impedance of the communication equipment.

[0038] Furthermore, the shielding structure and electromagnetic parameters are both characteristic parameters of the shielding layer of the shielded cable and are independent of each other, but the common coupling impedance can be mathematically expressed through the shielding structure and electromagnetic parameters. Therefore, the constructed shielded cable crosstalk suppression performance prediction model can intuitively express the relationship between the shielding structure and electromagnetic parameters and the common-mode crosstalk.

[0039] (3) Calculation of common coupling impedance for different types of shielded cables The shielded cables include shielded cables with braided shielding layers and shielded cables with tubular shielding layers, wherein the tubular shielding layers can be divided into two categories: shielded steel tubes and shielded cables.

[0040] 1. For braided shielded cable The characteristic structure of the braided shield is shown in the figure below: Figure 6 As shown in the figure, it can be seen that the braided shield is related to five structural parameters: 1) inner diameter D; 2) number of braids C; 3) number of braided wires N in a braid; 4) braided wire diameter d; 5) braiding angle α. The common coupling impedance of the braided shield consists of three parts: the first part is the scattering impedance Z d , which is used to characterize the diffusion capacity of the electromagnetic field in the shielding layer; the second part is the braided inductance M b , characterizing the ability of magnetic field coupling between the inner and outer braids; the third part is the hole inductance M h , characterizes the degree of direct leakage of electromagnetic field through the small hole. d Related to shielding structure and electromagnetic parameters, M h and M b All are related to the shielding structure. The expressions are as follows: (5) (6) (7) Where μ0 is the magnetic permeability in vacuum. E(e) and K(e) are the first and second complete elliptic integrals, and K is the braid coverage. b , e, b and h are the skin depth of the braided layer, the eccentricity of the diamond hole, the distance between two adjacent braids and the distance between two intersecting braids, respectively, and are defined as: (8) (9) (10) (11) μ in formula (8) rb and σ b are the relative magnetic permeability and electrical conductivity of the braided shielding material, respectively, and f is the operating frequency.

[0041] A, B, and D in formula (6) m They are defined as (12) (13) (14) Where v is the number of holes per unit length of the braid.

[0042] Optionally, the common coupling impedance of the braided shielded cable includes a scattering impedance Z d , Braided inductor M b and hole inductance M h , the expression is: (15) Where j is the imaginary unit, is the angular frequency.

[0043] 2. For tubular shielded cables The characteristic structure of the tubular shield is shown in the figure Figure 7 As shown. Figure 7 As shown in the figure, the tubular shielding layer structure is related to two parameters: 1) outer radius a; 2) shielding layer thickness T. Since the tubular shielding layer is a complete shielding layer without any holes, its public coupling impedance is only composed of a part, which is used to characterize the ability to prevent the external electromagnetic field from spreading to the inside.

[0044] The common coupling impedance of the tubular shielded cable is: (16) Among them, δ c is the skin depth of the tubular shielding layer, which is expressed as: (17) Among them, μ rc and σ c are the relative magnetic permeability and electrical conductivity of the tubular shielding material, respectively.

[0045] In this embodiment, the common coupling impedance of the shielding layer is obtained by a mathematical formula derivation method. In another embodiment, the common coupling impedance can also be obtained by actual measurement using an injection line method.

[0046] (4) Construct a crosstalk suppression performance prediction model for shielded cables based on shielding structure and electromagnetic parameters Based on the common coupling impedance circuit model of shielded cable common mode crosstalk and shielding layer common coupling impedance, the common coupling impedance circuit model of shielded cables with different shielding layers can be obtained, such as Figure 8 shown. Figure 8 (a) is a common coupling impedance circuit model using braided shielding, where i rb is the CM cable crosstalk current on the shielded cable core, i p is the common mode interference current on the power cable. p to i rb The transfer function is (18) Therefore, rb It can be calculated by formula (19).

[0047] (19) Figure 8 (b) is a common coupling impedance circuit model using tubular shielding, where i rc is the CM cable crosstalk current on the shielded cable core. Similarly, we can get p to i rc The transfer function is (20) Therefore, rc It can be calculated by formula (21).

[0048] (twenty one) Through equations (19) and (21), the crosstalk suppression performance of shielded cables with different types of shielding layers can be modeled considering the shielding structure and electromagnetic parameters.

[0049] (5) Predict, evaluate and optimize the crosstalk suppression performance of shielded cables The common mode interference current i is obtained through the common mode electromagnetic interference model of the inverter power supply p When the shielding layer structure and electromagnetic parameters of the shielded cable are known, the common-mode crosstalk current i of the shielded cable core wire after using this shielded cable can be obtained according to formula (19) or formula (21): r , to achieve accurate prediction and evaluation of the crosstalk suppression performance of shielded cables.

[0050] Exemplarily, the interference current i on the current power cable of the equivalent circuit is obtained. p According to formula (19) and formula (21), the prediction results of the common-mode crosstalk current of the braided shielded cable and the tubular shielded cable are calculated respectively. The crosstalk suppression performance of the shielded cables with different shielding structures is evaluated by comparing the values, and the shielded cable with the shielding structure with better crosstalk suppression performance is selected.

[0051] For example, for a determined shielding layer structure of a shielded cable, the crosstalk current spectrum of shielding materials with different electromagnetic parameters is predicted using a shielded cable crosstalk suppression performance prediction model, thereby evaluating the crosstalk suppression performance and selecting the optimal electromagnetic parameters.

[0052] Optionally, after S3, also include: Analyze the effect of different parameters of the shielded cable on the crosstalk current i r The importance of determining the dominant influencing parameters in different frequency bands; According to the calculated crosstalk interference current i p And the corresponding common-mode crosstalk current threshold, calculate the optimized values ​​of the dominant influencing parameters of the shielded cable shielding layer in different frequency bands, and then optimize the design of the shielded cable.

[0053] Specifically, based on equations (19) and (21), the effect of different parameters on the common-mode crosstalk current i r The dominant influencing parameters in different frequency bands are determined by considering the influence of the common-mode crosstalk current i. For braided shielded cables, the dominant factor in the low frequency band is the electromagnetic parameter, while the dominant factor in the high frequency band is the structural parameter. For tubular shielded cables, the structural and electromagnetic parameters are the dominant factors in the entire frequency band. r The current threshold and common mode interference current i p In the case of , the optimized parameter values ​​of the shielding layer of the shielded cable in different frequency bands are calculated according to formula (19) and formula (21), thereby realizing the optimized design of the shielded cable.

[0054] Based on the above examples, the model was verified. In an inverter power supply system, the key parameters of the inverter power supply are shown in Table 1. When a tubular shielded cable is used, the crosstalk suppression performance of the tubular shielded cable predicted by the model is compared with the measured results. Figure 9 As shown in the target frequency band, the prediction error is less than 6dB, and the precise modeling of the shielding cable crosstalk suppression performance is realized. In addition, through this model, the relationship between the shielding structure and the electromagnetic parameters and the CM cable crosstalk is quantified, thereby directly representing the influence of the shielding structure and the electromagnetic parameters on the shielding cable crosstalk suppression performance, providing theoretical and model guidance for subsequent precise optimization of the shielding cable crosstalk suppression performance, improving the design efficiency and reducing the number of iterative designs, and effectively reducing the loss of manpower and material resources.

[0055] In the embodiment of the present application, the total impedance of the common coupling impedance equivalent cable inter-distributed parameter is adopted, which creates conditions for subsequent direct representation of the relationship between the shielding structure and the electromagnetic parameters and the CM cable crosstalk. Compared with indirect representation of the shielding cable crosstalk suppression performance in the form of transfer impedance or shielding attenuation, the common coupling impedance simplifies the complexity of the model; further based on the common coupling impedance, a circuit model of the shielding cable crosstalk suppression performance considering the shielding structure and the electromagnetic parameters is proposed, thereby deducing the explicit expression of the shielding structure and the electromagnetic parameters and the CM cable crosstalk, and quantifying the influence of different parameters of the shielding cable on the CM cable crosstalk. The accurate prediction of the shielding cable crosstalk suppression performance is realized, and the optimization design of the shielding structure and the electromagnetic parameters of the shielding cable can also be accurately and effectively guided.

[0056] Embodiment two The present application also provides a shielding cable crosstalk suppression performance prediction system, comprising: A crosstalk model construction module is configured to obtain the common-mode interference source and the common-mode source impedance of the inverter power supply, establish an equivalent circuit of the common-mode electromagnetic interference of the inverter power supply, and construct a common-mode crosstalk model of the shielding cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit. An inhibition performance prediction model construction module is configured to replace the distributed parameters between the cables with the common coupling impedance, and update the common-mode crosstalk model of the shielding cable based on the common coupling impedance, to obtain a shielding cable crosstalk suppression performance prediction model based on the shielding structure and the electromagnetic parameters. A prediction and evaluation module is configured to obtain the common-mode interference current i p on the current power cable of the equivalent circuit, combine the preset shielding structure and electromagnetic parameters of the shielding cable, predict the common-mode crosstalk current of the shielding cable through the shielding cable crosstalk suppression performance prediction model, and evaluate the crosstalk suppression performance of the shielding cable.

[0057] The shielding cable crosstalk suppression performance prediction system provided in the embodiment of the present application is used to execute the shielding cable crosstalk suppression performance prediction method in embodiment one, and has the same or similar beneficial effects.

[0058] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting the crosstalk suppression performance of a shielded cable, characterized in that: include: S1. Obtaining the common-mode interference source and common-mode source impedance of the inverter power supply, establishing a common-mode electromagnetic interference equivalent circuit of the inverter power supply, and constructing a common-mode crosstalk model of the shielded cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit; S2. Using common coupling impedance to replace the distributed parameters between cables, and updating the common-mode crosstalk model of the shielded cable based on the common coupling impedance to obtain a crosstalk suppression performance prediction model of the shielded cable based on the shielding structure and electromagnetic parameters; S3. Obtaining the common-mode interference current on the current power cable of the equivalent circuit i p , combined with the preset shielding structure and electromagnetic parameters of the shielded cable, the crosstalk suppression performance prediction model of the shielded cable is used to predict the spectrum of the crosstalk current of the shielded cable, and the crosstalk suppression performance of the shielded cable is evaluated.

2. The method according to claim 1, wherein The common mode interference source is a voltage source V CM ; The common-mode source impedance is composed of the ground capacitance of the inverter power supply and the parasitic parameters of the filter.

3. The method according to claim 1, wherein Before S2, it also included: When the shield in a cable bundle is grounded at both ends, the shield's ability to suppress inductive coupling is related to its inflection point frequency. f SH The relationship is: in, R SH is the resistance of the shielding layer, L SH is the self-inductance of the shield; When the predicted frequency of the crosstalk suppression performance of the shielded cable is greater than f SH When the ground loop is considered as an open circuit, the common-mode crosstalk model of the shielded cable is simplified.

4. The method according to claim 1, wherein The crosstalk suppression performance prediction model of the shielded cable is: in, i p is the common mode interference current on the power cable, is the common mode interference current on the power cable i p Cable common mode crosstalk current to the shielded cable core i r The transfer function, is the common coupling impedance, is the equivalent common-mode impedance of the communication equipment.

5. The method according to claim 4, wherein The shielded cables include braided shielded cables and tubular shielded cables.

6. The method according to claim 5, wherein The common coupling impedance of the braided shielded cable includes the scattering impedance Z d , braided inductor M b and hole inductance M h , the expression is: in, j is the imaginary unit, is the angular frequency, Z d Related to shielding structure and electromagnetic parameters, M h and M b All are related to the shielding structure.

7. The method according to claim 5, wherein The common coupling impedance of the tubular shielded cable is: in, a is the outer radius, T is the thickness of the shielding layer; δ c is the skin depth of the tubular shield, defined as , μ rc and σ c are the relative magnetic permeability and electrical conductivity of the tubular shielding material, respectively.

8. The method according to claim 1, wherein After S3, it also includes: Analysis of the effects of different parameters of the shielded cable on the common-mode crosstalk current i r The importance of determining the dominant influencing parameters in different frequency bands; According to the calculated common mode interference current i p And the corresponding common-mode crosstalk current threshold, calculate the optimized values ​​of the dominant influencing parameters of the shielded cable shielding layer in different frequency bands, and then optimize the design of the shielded cable.

9. A system for predicting the crosstalk suppression performance of a shielded cable, characterized in that: include: A crosstalk model building module is used to obtain the common-mode interference source and common-mode source impedance of the inverter power supply, establish the common-mode electromagnetic interference equivalent circuit of the inverter power supply, and build a common-mode crosstalk model of the shielded cable in the inverter power supply system based on the equivalent circuit and the cable bundle equivalent circuit; A suppression performance prediction model construction module is used to use common coupling impedance to replace the distributed parameters between cables, and update the common-mode crosstalk model of the shielded cable based on the common coupling impedance to obtain a shielded cable crosstalk suppression performance prediction model based on the shielding structure and electromagnetic parameters; A prediction and evaluation module for obtaining the common-mode interference current on the current power cable of the equivalent circuit i p , combined with the preset shielding structure and electromagnetic parameters of the shielded cable, the common-mode crosstalk current of the shielded cable is predicted by the shielded cable crosstalk suppression performance prediction model, and the crosstalk suppression performance of the shielded cable is evaluated.

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