Parameter design method, device and system for hybrid electromagnetic interference filter

Abstract

The invention discloses a parameter design method, device and system for a hybrid electromagnetic interference filter, and belongs to the technical field of power electronic control. The target passive device parameter corresponding to the minimum common mode inductance meeting the preset condition is found; the preset condition is that under the control of the target passive device parameter and the corresponding target active control parameter, the corresponding attenuation degree difference value of the hybrid electromagnetic interference filter in the concerned frequency band is smaller than a threshold value; and outputting the target passive device parameter and the corresponding target active control parameter. According to the invention, with the attention frequency band attenuation degree as a target, the attenuation degree of the HEF can approach to the difference between the actual interference and the standard limit value to the maximum extent, and unnecessary redundancy design is effectively avoided. The self-adaption process of the attenuation degree can fully develop the interference attenuation performance of the AEF, and the performance requirement for the PEF is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic control, and more specifically, relates to a parameter design method, device and system for a hybrid electromagnetic interference filter. Background Art

[0002] The operation of power electronic devices is based on the principle of pulse width modulation, and the power switches operate in a high-speed on-off state. This inherent switching mode will produce large voltage jumps (dv / dt) and current jumps (di / dt), forming an electromagnetic interference (EMI) source containing rich high-frequency components. At the same time, the application of wide bandgap semiconductors further improves the switching speed of power switches and the levels of dv / dt and di / dt. In high power density scenarios, the narrow space and compact layout will lead to more serious coupling between EMI sources and paths, and between paths. In particular, the common-mode EMI of power electronic devices to the ground is further aggravated, resulting in problems such as leakage current, radiated interference emission, and abnormal operation of sensitive equipment, and electromagnetic compatibility standards are more difficult to meet.

[0003] In order to limit the common-mode EMI of high-power density power electronic devices, corresponding EMI filters must be added to their propagation paths. Passive EMI filters are the most intensively studied and widely used EMI filters, which use the frequency characteristics of inductors and capacitors to block and shunt EMI. However, relevant standards require that the ground leakage current cannot exceed a certain level to avoid electric shock, so the common-mode capacitance value in PEF is strictly limited, and its performance mainly depends on the common-mode inductor. When the core material is determined, the volume and weight of the common-mode inductor will increase as the cut-off frequency decreases, and may even be equivalent to the power conversion circuit part, which is contrary to the goal of high power density of power electronic devices. In order to increase the cut-off frequency of PEF, active EMI filters have begun to be used to suppress common-mode EMI. Based on the principle of detection-cancellation, active EMI filters AEF inject large reverse signals such as common-mode current into the interference loop, which can achieve good interference suppression effects in the medium and low frequency bands; however, limited by the characteristics of the signal processing link, the suppression effect of AEF in the high frequency band is difficult to improve. The hybrid electromagnetic interference filter HEF has both active control circuit and passive EMI filter components. It combines the characteristics and advantages of AEF and PEF, which not only improves the cutoff frequency of PEF, but also makes up for the defect of insufficient suppression ability of AEF in the high frequency band. It is the main development direction of EMI filters at present.

[0004] However, the design of HEF is based on the maximum value of the required attenuation. However, in actual devices, common mode interference has multiple resonance peaks within the frequency band specified by the standard, which makes the design oriented towards maximum attenuation have a large attenuation redundancy in other frequency bands. This shows that the interference suppression capability of HEF has not been fully developed, and it is urgent to adopt a reasonable design method to make full use of limited filter resources. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a parameter design method for a hybrid electromagnetic interference filter, which aims to solve the technical problem that the existing hybrid electromagnetic interference filter focuses on a single resonance peak and is designed only for the maximum attenuation, resulting in a large amount of redundant attenuation at other resonance peaks.

[0006] To achieve the above object, according to one aspect of the present invention, a parameter design method for a hybrid electromagnetic interference filter is provided, comprising:

[0007] S1: Setting initial passive device parameters of the passive EMI filter in the hybrid electromagnetic interference filter;

[0008] S2: adjusting the common-mode inductance in the initial passive device parameters until the target passive device parameters corresponding to the minimum common-mode inductance that meets the preset conditions are found; during the adjustment process, obtaining the current active control parameters corresponding to the current passive device parameters, and the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters; the preset condition is: under the control of the target passive device parameters and their corresponding target active control parameters, the attenuation difference corresponding to the hybrid electromagnetic interference filter in the frequency band of interest is less than a threshold value;

[0009] S3: Using the target passive device parameters as the target design parameters of the passive EMI filter; using the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter in the hybrid electromagnetic interference filter.

[0010] In one embodiment, the S2 includes:

[0011] S21: reducing the common mode inductance in the initial passive device parameters to obtain current passive device parameters;

[0012] S22: Obtain current active control parameters corresponding to current passive device parameters;

[0013] S23: Calculating the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters;

[0014] S24: If the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters are both less than a threshold value, then continue to reduce the common-mode inductance; otherwise, increase the common-mode inductance. If the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters corresponding to the common-mode inductance after the increase are both less than the threshold value, then continue to increase the common-mode inductance until the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters corresponding to the common-mode inductance after the increase are not all less than the threshold value;

[0015] S25: using the common mode inductance in the penultimate iteration as the target passive component parameter; and using the current active control parameter corresponding to the target passive component parameter as the target active control parameter.

[0016] In one embodiment, the obtaining of current active control parameters corresponding to current passive device parameters includes:

[0017] The common mode inductance in the current passive device parameters is used as the initial value of the optimization model. is the objective function of the optimization model, the current active control parameter is the decision variable of the optimization model, and the circuit requirement of the active EMI filter is the penalty function of the optimization model;

[0018] Iterating the optimization model until finding the current active control parameter corresponding to which the attenuation difference in the frequency band of interest is less than the threshold;

[0019] Among them, f1 and f n Represents the first and last frequency points in the standard frequency band, ΔIL represents the value corresponding to the attenuation difference of the current frequency point, C is the threshold, ΔIL AEF is the attenuation difference.

[0020] In one embodiment, the S23 includes:

[0021] S231: Obtaining the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF and the actual attenuation IL of the hybrid electromagnetic interference filter under the control of the current passive device parameters and the current active control parametersAEF ;

[0022] S232: Using the formula ATT AEF =N CM -Std-IL PEF Calculate the required minimum attenuation ATT of the active EMI filter AEF , N CM is the current common mode interference; Std is the electromagnetic compatibility standard limit, IL PEF is the actual attenuation of the passive EMI filter;

[0023] S233: Using the formula ΔIL AEF =(ATT AEF +C)-IL AEF Calculate the attenuation difference ΔIL of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters AEF ; C is the threshold value.

[0024] In one embodiment, the S231 includes:

[0025] Using the formula Calculate the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF ;

[0026] Using the formula Calculate the actual attenuation IL of the hybrid electromagnetic interference filter under the control of the current passive device parameters and the current active control parameters AEF ;

[0027] Among them, I q1 is the common mode current in the hybrid electromagnetic interference filter without an EMI filter, I q2 is the common mode current in the hybrid electromagnetic interference filter when only the passive EMI filter is present, I q It is the common mode current in the scenario where the passive EMI filter and the active EMI filter exist in the hybrid electromagnetic interference filter.

[0028] In one embodiment, the sampling link parameters include: a primary-to-secondary coil turns ratio of a sampling link in the active EMI filter.

[0029] In one of the embodiments, the signal amplification link parameters include: a sampling resistance value and an inverting amplification gain of the signal amplification link in the active EMI filter.

[0030] In one of the embodiments, the interference compensation link parameters include: an equivalent circuit and an equivalent capacitance of the interference compensation link in the active EMI filter.

[0031] According to another aspect of the present invention, there is provided a parameter design device for a hybrid electromagnetic interference filter, comprising:

[0032] An initial setting module, used for setting initial passive device parameters of a passive EMI filter in a hybrid electromagnetic interference filter;

[0033] An adjustment and optimization module is used to adjust the common-mode inductance in the initial passive device parameters until the target passive device parameters corresponding to the minimum common-mode inductance that meets the preset conditions are found; during the adjustment process, the current active control parameters corresponding to the current passive device parameters are obtained, as well as the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters; the preset condition is: under the control of the target passive device parameters and their corresponding target active control parameters, the attenuation difference corresponding to the hybrid electromagnetic interference filter in the frequency band of interest is less than a threshold value;

[0034] A parameter design module is used to use the target passive component parameters as the target design parameters of the passive EMI filter; and use the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter.

[0035] According to another aspect of the present invention, a parameter design system for a hybrid electromagnetic interference filter is provided, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method when executing the computer program.

[0036] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are implemented.

[0037] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0038] (1) The present invention provides a parameter design method for a hybrid electromagnetic interference filter, by adjusting the common-mode inductance in the initial passive device parameters until the target passive device parameters corresponding to the minimum common-mode inductance that meets the preset conditions are found; during the adjustment process, the current active control parameters corresponding to the current passive device parameters are obtained, as well as the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters; the present invention takes the attenuation of the frequency band of interest as the target, so that the attenuation of the HEF can be as close to the difference between the actual interference and the standard limit as possible, effectively avoiding unnecessary redundant design. The adaptive process of the attenuation in the process of obtaining the current active control parameters corresponding to the current passive device parameters can fully develop the interference attenuation performance of the AEF, reduce the performance requirements for the PEF, thereby reducing the volume and weight of the passive device, and realizing the improvement of the power density of the power electronic device. In addition, the proposed design method also has the advantages of low software and hardware costs and strong portability.

[0039] (2) In this scheme, the initial HEF condition is given for optimization iteration, that is, the common mode inductance L CM If the current active control parameter KP meets the standard, the attenuation difference ΔIL in the frequency band of interest is satisfied. AEF <0, then reduce L CM The iteration continues; if the iteration result cannot meet the standard, the previous iteration result KP and L CM As the final output value. The above optimization method is simple to operate and has low calculation complexity, and can quickly find the optimal common-mode inductance L CM And its corresponding active control parameter KP.

[0040] (3) This solution uses the common-mode inductance in the current passive device parameters as the initial value of the optimization model. The objective function of the optimization model is taken as the decision variable of the optimization model, and the circuit requirements of the active EMI filter are taken as the penalty function of the optimization model. The above optimization model can quickly and accurately provide the direction of searching for the current active control parameter KP, but whether the convergence value meets the standard requirements needs to be combined with ΔIL AEF Make a judgment.

[0041] (4) This scheme uses the formula ATT AEF =N CM -Std-IL PEF Calculate the required minimum attenuation ATT of the active EMI filter AEF ,This method can accurately quantify its target attenuation and provide support for the objective function of the optimization algorithm, thereby achieving the optimization of the active control parameters at the beginning of the AEF design.

[0042] (5) This scheme uses the formula and Calculate the actual attenuation IL of passive EMI filters and active EMI filters PEF With IL AEF This approach can decouple the interference attenuation effects of AEF and PEF, so that the active control parameters and IL can be focused separately based on simulation and experiment. AEF The quantitative relationship between them, combined with the attenuation target, realizes the iterative optimization process of active control parameters.

[0043] (6) The sampling link parameters described in this scheme include: the primary-to-secondary coil turns ratio of the sampling link in the active EMI filter; the signal amplification link parameters include: the sampling resistance value and the inverting amplification gain of the signal amplification link in the active EMI filter; the interference compensation link parameters include: the equivalent circuit and equivalent capacitance of the interference compensation link in the active EMI filter; such a design can fully consider the control parameters in the circuit that are easy to adjust and have a significant impact on the attenuation, thereby improving the control freedom of the hybrid electromagnetic interference filter and realizing the flexibility and high controllability of the EMI filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of a parameter design method of a hybrid electromagnetic interference filter provided in Example 1 of the present invention;

[0045] Figure 2 A schematic diagram of a common-mode path of a bridge inverter provided in Embodiment 1 of the present invention;

[0046] Figure 3 An equivalent circuit diagram of a common-mode path after adopting HEF provided in Embodiment 1 of the present invention;

[0047] Figure 4 An equivalent circuit diagram of a CT circuit provided in Embodiment 1 of the present invention;

[0048] Figure 5 A comparison chart of the frequency response modeling results of the key links provided in Example 1 of the present invention and the actual measurement results of the network analyzer;

[0049] Figure 6 A comparison chart of the key impedance modeling results provided in Example 1 of the present invention and the impedance meter measured results;

[0050] Figure 7 A simplified equivalent circuit diagram before and after the EMI filter is used provided in Embodiment 1 of the present invention;

[0051] Figure 8 The open-loop gain and closed-loop gain effect diagram of the operational amplifier provided in Embodiment 1 of the present invention;

[0052] Fig. 9 A schematic diagram of the frequency response of a CT provided in Example 1 of the present invention;

[0053] Fig.10 A frequency response change diagram of CT and operational amplifier when parameters are changed provided in Example 1 of the present invention;

[0054] Fig.11 A schematic diagram of the objective function composition and iterative process of the optimization algorithm provided in Example 1 of the present invention;

[0055] Fig.12 A flow chart of a HEF design method with adaptive attenuation provided in Example 1 of the present invention;

[0056] Fig.13 A simulation diagram of the HEF design process provided in Example 1 of the present invention;

[0057] Fig.14 The measured spectrum diagram of iteratively optimizing AEF parameters when the PEF is unchanged provided in Example 1 of the present invention;

[0058] Fig.15 This is a measured spectrum diagram after optimizing PEF parameters provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can be combined with each other as long as they do not conflict with each other.

[0060] Example 1

[0061] like Figure 1As shown, this embodiment provides a parameter design method for a hybrid electromagnetic interference filter, wherein the hybrid electromagnetic interference (EMI) filter includes: a passive electromagnetic interference (EMI) filter and an active electromagnetic interference (EMI) filter. The invention discloses a hybrid electromagnetic interference (EMI) filter; the parameter design method comprises the following steps: S1: setting initial passive device parameters of a passive EMI filter in a hybrid electromagnetic interference filter; S2: adjusting the common mode inductance in the initial passive device parameters until finding the target passive device parameters corresponding to the minimum common mode inductance that meets the preset conditions; in the adjustment process, obtaining the current active control parameters corresponding to the current passive device parameters, and the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in a frequency band of interest under the control of the current passive device parameters and the current active control parameters; the preset condition is that under the control of the target passive device parameters and their corresponding target active control parameters, the corresponding attenuation difference of the hybrid electromagnetic interference filter in the frequency band of interest is less than a threshold value; S3: taking the target passive device parameters as the target design parameters of the passive EMI filter; using the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter in the hybrid electromagnetic interference filter.

[0062] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0063] The common mode interference path of a typical bridge inverter is as follows: Figure 2 As shown in the figure, the high-speed on-off of the power switch causes a large voltage jump dv / dt at the midpoint of the bridge arm, and the parasitic capacitance C between the power module and the load to the heat sink p The induced common mode current i CM , as shown in formula (1).

[0064]

[0065] Considering the nature of the common-mode interference source, it can usually be equivalent to a voltage source in circuit analysis. At the same time, the capacitance C p And parasitic parameters such as lead inductance together constitute the common mode source impedance Z CM . Subsequently, the common-mode current i CM It returns to the line impedance stabilization network (LISN) through the device protection ground and finally returns to the DC bus. The function of LISN is to isolate the interference introduced by the DC power supply and simulate the impedance of the grid side to provide a reference for the measurement of common mode interference of the target device.

[0066] Then, an active EMI filter (AEF) is designed according to the common-mode interference path. AEF has three links inside: sampling link, signal amplification link and compensation link. Among them, the current transformer (CT) can collect the common-mode current in the loop and convert it into a voltage signal; the signal amplification link is usually composed of an operational amplifier and a push-pull amplifier, which can reverse and amplify the signal collected by CT; the compensation link is an RC branch, which can isolate the internal analog circuit of AEF from the DC power circuit, and inject the amplified compensation signal into the interference circuit. The equivalent common-mode interference circuit after inserting AEF is as follows Figure 3 shown. Figure 4 The equivalent circuit diagram of CT shows that CT converts the common mode current i CM Converted into the input voltage U of the signal amplification link in , where C pp With C sp are the parasitic capacitance of the original and secondary sides, L m is the magnetizing inductance, R c L is the equivalent resistance that represents the loss. l With R p are the lead inductance and resistance. The transfer function can be expressed as formula (2).

[0067]

[0068] Similarly, formula (3) represents the transfer function of the signal amplification link, where -R f / R1 is the gain of the inverting amplifier, G op is the open-loop gain of the operational amplifier, which can be found in the technical manual, Z in is the input impedance of the push-pull amplifier, Z o is the operational amplifier output impedance, usually Z in Much larger than Z o , so the third term on the right side of formula (3) can be regarded as 1. Figure 5The modeling results of the frequency response of the CT and signal amplification link are compared with the actual measurement results of the network analyzer. Figure 6 is the common mode source impedance Z CM and LISN impedance Z LISN Comparing the modeling results with the measured results of the impedance analyzer, it can be seen that the modeling results are highly consistent with the actual results in the frequency band of interest 10kHz-10MHz.

[0069] As an optional implementation, S2 includes: S21: reducing the common-mode inductance in the initial passive device parameters to obtain the current passive device parameters; S22: obtaining the current active control parameters corresponding to the current passive device parameters; S23: calculating the difference between the minimum attenuation required for the hybrid electromagnetic interference filter in the frequency band of interest and the actual attenuation under the control of the current active control parameters and the current passive device parameters; S24: if the difference between the attenuation corresponding to the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters is less than the threshold, then continue to reduce the common-mode inductance; otherwise, increase Add common-mode inductance. If the difference between the current passive device parameters corresponding to the addition of the common-mode inductance and the attenuation degree of the hybrid electromagnetic interference filter under the control of the current active control parameters in the frequency band of interest is less than the threshold, continue to increase the common-mode inductance until the difference between the current passive device parameters corresponding to the addition of the common-mode inductance and the attenuation degree of the hybrid electromagnetic interference filter under the control of the current active control parameters in the frequency band of interest is not less than the threshold; S25: use the common-mode inductance in the penultimate iteration as the target passive device parameter; use the current active control parameter corresponding to the target passive device parameter as the target active control parameter.

[0070] As an optional implementation, S23 includes: S231: Obtaining the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF The actual attenuation IL of the hybrid EMI filter under the control of the current passive device parameters and the current active control parameters AEF ; S232: Using formula ATT AEF =N CM -Std-IL PEF Calculate the minimum required attenuation ATT of active EMI filters AEF , N CM is the current common mode interference; Std is the electromagnetic compatibility standard limit, IL PEF is the actual attenuation of the passive EMI filter; S233: using the formula ΔIL AEF =(ATT AEF +C)-IL AEF Calculate the attenuation difference ΔIL of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters AEF ; C is the threshold.

[0071] In order to effectively exert the interference compensation effect of AEF, a mathematical model to characterize the attenuation degree needs to be established. Since the ultimate goal is to pass the EMC standard, the requirements for the AEF attenuation degree are first stated. The requirements that the AEF attenuation degree should meet are shown in formula (4).

[0072] IL AEF >N CM -Std-IL PEF =ATT AEF (4)

[0073] Among them, IL AEF is the actual attenuation provided by AEF, N CM is the common mode interference amplitude, Std is the EMC standard limit, IL PEF The actual attenuation provided, ATT AEF is the minimum attenuation required by AEF. To meet EMC standards, formula (4) must be satisfied at every frequency point within its specified frequency band. For ease of mathematical expression, define ΔIL AEF As shown in formula (5).

[0074] ΔIL AEF =(ATT AEF +6)-IL AEF (5)

[0075] It represents the difference between the attenuation provided by AEF and the required attenuation, ΔIL AEF The attenuation provided by AEF is not enough to meet the EMC standard. AEF +6 means adding a 6dB limit to the EMC limit.

[0076] As an optional implementation, S231 includes: using the formula Calculate the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF ; Using the formula Calculate the actual attenuation IL of the hybrid EMI filter under the control of the current passive device parameters and the current active control parameters AEF ; Among them, I q1 is the common mode current in the hybrid electromagnetic interference filter without EMI filter, I q2 is the common mode current in the hybrid electromagnetic interference filter when there is only a passive EMI filter, I q It is the common mode current in the scenario where there are passive EMI filters and active EMI filters in the hybrid electromagnetic interference filter.

[0077] Based on the common mode interference path, Figure 7The equivalent circuits of three cases, without EMI filter, with PEF and with HEF, are compared. out is the output impedance of the push-pull amplifier, Z comp To compensate for the equivalent impedance of the circuit, Z L is the impedance of the common mode inductor, V AEF is the voltage at the output point of the push-pull amplifier. Based on this, the attenuation of PEF, AEF and HEF can be calculated using Kirchhoff's law, as shown in formula (6), formula (7) and formula (8) respectively.

[0078]

[0079] IL HEF =IL PEF +IL AEF (8)

[0080] It can be seen that the attenuation of AEF is directly related to the frequency response of CT and signal amplification.

[0081] As an optional implementation, the sampling link parameters include: the primary-to-secondary coil turns ratio of the sampling link in the active EMI filter; the signal amplification link parameters include: the sampling resistance value and the inverting amplification gain of the signal amplification link in the active EMI filter. The interference compensation link parameters include: the equivalent circuit and equivalent capacitance of the interference compensation link in the active EMI filter.

[0082] Figure 8 is the comparison between the open-loop gain and closed-loop gain of the operational amplifier, G a1 With G a2 Represents two different closed-loop gains. The gain-bandwidth product (GBW) is the intersection of the open-loop gain and the horizontal axis. The larger the GBW, the better the high-frequency response performance of the op amp, which is related to the internal process of the op amp. At the same time, GBW represents the product of the closed-loop gain and its corresponding bandwidth, which means that the two are inversely proportional when the op amp is determined. a1 With G a2 , G a1 It has a larger gain, but the frequency band A1 in which it can maintain a constant gain is smaller than G a2 Corresponding to B1, and due to the influence of phase shift in the Δ interval, G a1 The effective gain will be weakened. Therefore, starting from the attenuation of AEF, the increase of op amp gain will lead to the opposite change of attenuation in different frequency bands. Fig. 9 The frequency response diagram of CT is shown in Figure 2. When the gain of CT is increased, the constant gain frequency band will also be reduced. Therefore, in the Δ range, the larger the gain G c1 After phase shift, the actual effective value is only G1eff , but smaller than G c2 , resulting in the final AEF attenuation to change in opposite directions in different frequency bands. Fig.10 The frequency responses of the op amp and CT are combined, and the effects of different parameter changes are compared; for example, when the sampling resistor R sense When it increases, its gain is increased by about 6dB at most, but the phase shifts more after 1MHz and before 200kHz compared with the control group. The above analysis shows that when the response of a single link inside the AEF changes, it will have different effects on the AEF attenuation in different frequency bands; and the key parameter affecting the response of these links is defined as KP, as shown in formula (9). Obviously, considering that the frequency band of interest is wide, the impact of parameter changes on attenuation is difficult to directly calculate through formulas (6), (7) and (8), and a simpler and more feasible method needs to be designed, that is, formula (9) can be used to characterize the current active control parameters.

[0083]

[0084] As an optional implementation, obtaining the current active control parameters corresponding to the current passive device parameters includes: using the common mode inductance in the current passive device parameters as the initial value of the optimization model, and using is the objective function of the optimization model, the current active control parameters are used as the decision variables of the optimization model, and the circuit requirements of the active EMI filter are used as the penalty function of the optimization model; the optimization model is iterated until the current active control parameters corresponding to the attenuation difference in the frequency band of interest are found to be less than the threshold; where f1 and f n represents the first and last frequency points in the standard frequency band, ΔIL represents the value corresponding to the attenuation difference of the current frequency point, C is the threshold, ΔIL AEF is the attenuation difference.

[0085] Considering KP and IL AEF The above problem can be expressed as: Find a KP such that IL AEF Satisfies formula (4). Furthermore, due to IL AEF ΔIL can be uniquely determined AEF , so the problem can be further transformed into: Find a KP such that ΔIL AEFare all less than zero in the frequency band of interest. An optimization algorithm can be used to implement the search for KP. The optimization algorithm has three elements: decision variables, objective functions and penalty functions; among which: the objective function is the object of the algorithm's iterative optimization, and in single-objective optimization it is usually the search for the minimum value; the decision variable is the independent variable corresponding to the objective function; the penalty function is a function that constrains the range of variation of the decision variable. In this design, the decision variable is KP, and the penalty function is limited by the circuit requirements, such as the size of the ground leakage current, the op amp voltage cannot be saturated, and the stability of the control loop. Formula (10) defines the objective function formula (objective function, OF), where f1 and f n represents the first and last frequency points in the standard frequency band, and ΔIL is defined by formula (11). ΔIL is based on the ΔIL of a certain frequency point. AEF To assign a value, if ΔIL AEF If ΔIL is greater than zero, the square form will be used to increase ΔIL significantly, because this means that the EMC standard cannot be met at this frequency. AEF If ΔIL is less than -6dB, let ΔIL be equal to zero, because this means that the standard is met at this frequency point and there is a 6dB margin; if ΔIL AEF Between -6dB and 0, a smaller weight is given to ΔIL as a transition interval.

[0086]

[0087] Fig.11 This shows the advantage of OF: the interference exceeding the standard in the frequency band of interest is quantified as the area enclosed by ΔIL and the horizontal axis. Before iteration, Fig.11 As shown in the figure, due to the existence of intervals that do not meet the standard, the area enclosed by ΔIL and the horizontal axis, that is, the OF value, is large; after iterative optimization of OF, as shown in the figure, Fig.11 As shown in Figure 2, OF is greatly reduced at this time, and the corresponding attenuation also meets the requirements. It is worth mentioning that although the optimization algorithm can search for the minimum value of OF, and the reduction of OF is related to ΔIL AEF The OF is strongly correlated with the reduction of the frequency band of interest, but it cannot guarantee that the standard requirements will be met when the OF reaches the minimum value. This is because OF depends on the attenuation of AEF, and from formula (7), it can be seen that the attenuation of AEF is also related to PEF. Therefore, when the PEF value is too small or the design is unreasonable, the optimization of AEF alone cannot meet the EMC standard. Therefore, the algorithm can provide a direction for searching the AEF parameter KP, but whether the convergence value meets the standard requirements still needs to be combined with ΔIL AEF This design uses the genetic algorithm (GA), which has excellent performance in single-objective optimization processing and has been widely used.

[0088] Fig.12 The process of HEF adaptive attenuation design based on the above optimization algorithm is shown. First, given the initial HEF condition, optimization iteration is performed, i.e., L CM If the standard is met at this time, the frequency band of interest ΔIL is satisfied. AEF <0, then reduce L CM The iteration continues; if the iteration result cannot meet the standard, the previous iteration result KP and L CM as the final output value. Fig.13 The above process is simulated by simulation. First, IL is calculated according to the initial parameters. PEF With IL AEF , combining the simulated interference source with the standard limit to calculate ΔIL AEF , at this time ΔIL AEF If it is greater than zero in the low frequency band, it means that the standard is not met in this frequency band. Then, the optimized KP is calculated using the optimization algorithm. At this time, the corresponding ΔIL AEF In the target frequency band, the values ​​are all less than zero. However, there is a large attenuation redundancy in the mid- and high-frequency bands, which indicates that the filter parameters can be further optimized. Finally, reduce the common-mode inductance L CM And continue to iterate to achieve smaller attenuation redundancy until L CM The value is so small that KP cannot meet the standard no matter how it is iterated. Take the previous KP and its corresponding L CM To design HEF.

[0089] Fig.14 The experimental results of iterating KP using the optimization algorithm show that after the AEF parameter optimization, the common mode interference that was originally not allowed to exceed the standard can meet the standard. Note that the interference spectrum after optimization is reduced in the frequency band that exceeded the standard before optimization, but it is increased in the low frequency band. This further illustrates that the adjustability of AEF attenuation will cause the attenuation of different frequency bands to show different trends. The significance of the optimization algorithm is to iterate the attenuation in the direction of satisfying the interference standard, which transcends the limitation of traditional HEF that is only designed for the maximum attenuation.

[0090] Further, Fig.14 After optimization, the interference spectrum still has a large redundancy compared to the limit. Fig.15 The results of the optimization after reducing the PEF parameter are shown. The common mode inductance is now smaller than Fig.14The situation is reduced by 73%. It can be seen that the interference can still meet the standard and leave a 6dB margin. At the same time, the common-mode interference is closer to the standard limit in the concerned frequency band. Obviously, this process is to make the attenuation of AEF adaptively designed according to the actual interference, so as to maximize the ability of HEF and reduce unnecessary design redundancy of the filter; and, under the premise of meeting the standard, the minimum value of common-mode inductance is obtained, so that the volume and weight of PEF are minimized, and the power density of the device is improved.

[0091] Example 2

[0092] This embodiment provides a parameter design device for a hybrid electromagnetic interference filter. The hybrid electromagnetic interference filter includes: a passive EMI filter and an active EMI filter; the parameter design device includes: an initial setting module, an adjustment optimization module and a parameter design module.

[0093] An initial setting module, used for setting initial passive device parameters of a passive EMI filter in a hybrid electromagnetic interference filter;

[0094] The adjustment optimization module is used to adjust the common-mode inductance in the initial passive device parameters until the target passive device parameters corresponding to the minimum common-mode inductance that meets the preset conditions are found; during the adjustment process, the current active control parameters corresponding to the current passive device parameters are obtained, as well as the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters; the preset condition is: under the control of the target passive device parameters and their corresponding target active control parameters, the corresponding attenuation difference of the hybrid electromagnetic interference filter in the frequency band of interest is less than the threshold value;

[0095] The parameter design module is used to use the target passive device parameters as the target design parameters of the passive EMI filter; and use the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter.

[0096] The division of each module in the above-mentioned parameter design device of the hybrid electromagnetic interference filter is only for illustration. In other embodiments, the parameter design device of the hybrid electromagnetic interference filter can be divided into different modules as needed to complete all or part of the functions of the above-mentioned parameter design device of the hybrid electromagnetic interference filter.

[0097] The specific definition of the parameter design device of the hybrid electromagnetic interference filter can be found in the definition of the parameter design method of the hybrid electromagnetic interference filter in the above text, which will not be repeated here. Each module in the parameter design device of the hybrid electromagnetic interference filter can be implemented in whole or in part by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0098] Example 3

[0099] This embodiment provides a parameter design system for a hybrid electromagnetic interference filter, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method when executing the computer program.

[0100] Example 4

[0101] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method are implemented.

[0102] It will be easily understood by those skilled in the art that the above description is only 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 protection scope of the present invention.

Claims

1. A parameter design method for a hybrid electromagnetic interference filter, characterized in that: include: S1: Setting initial passive device parameters of the passive EMI filter in the hybrid electromagnetic interference filter; S2: adjusting the common-mode inductance in the initial passive device parameters until the target passive device parameters corresponding to the minimum common-mode inductance that meets the preset conditions are found; during the adjustment process, obtaining the current active control parameters corresponding to the current passive device parameters, and the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters; the preset condition is: under the control of the target passive device parameters and their corresponding target active control parameters, the attenuation difference corresponding to the hybrid electromagnetic interference filter in the frequency band of interest is less than a threshold value; S3: Using the target passive device parameters as the target design parameters of the passive EMI filter; using the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter in the hybrid electromagnetic interference filter.

2. The parameter design method of the hybrid electromagnetic interference filter according to claim 1, characterized in that: The S2 includes: S21: reducing the common mode inductance in the initial passive device parameters to obtain current passive device parameters; S22: Obtain current active control parameters corresponding to current passive device parameters; S23: Calculating the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters; S24: If the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current active control parameters and the current passive device parameters are both less than a threshold value, then continue to reduce the common-mode inductance; otherwise, increase the common-mode inductance. If the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters corresponding to the common-mode inductance after the increase are both less than the threshold value, then continue to increase the common-mode inductance until the attenuation difference values ​​of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters corresponding to the common-mode inductance after the increase are not all less than the threshold value; S25: using the common mode inductance in the penultimate iteration as the target passive component parameter; and using the current active control parameter corresponding to the target passive component parameter as the target active control parameter.

3. The parameter design method of the hybrid electromagnetic interference filter according to claim 1 or 2, characterized in that: The obtaining of current active control parameters corresponding to current passive device parameters includes: The common mode inductance in the current passive device parameters is used as the initial value of the optimization model. is the objective function of the optimization model, the current active control parameter is the decision variable of the optimization model, and the circuit requirement of the active EMI filter is the penalty function of the optimization model; Iterating the optimization model until finding the current active control parameter corresponding to which the attenuation difference in the frequency band of interest is less than the threshold; Among them, f1 and f n Represents the first and last frequency points in the standard frequency band, ΔIL represents the value corresponding to the attenuation difference of the current frequency point, C is the threshold, ΔIL AEF is the attenuation difference.

4. The parameter design method of the hybrid electromagnetic interference filter as claimed in claim 2, characterized in that: The S23 includes: S231: Obtaining the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF and the actual attenuation IL of the hybrid electromagnetic interference filter under the control of the current passive device parameters and the current active control parameters AEF ; S232: Using the formula ATT AEF =N CM -Std-IL PEF Calculate the required minimum attenuation ATT of the active EMI filter AEF , N CM is the current common mode interference; Std is the electromagnetic compatibility standard limit, IL PEF is the actual attenuation of the passive EMI filter; S233: Using the formula ΔIL AEF =(ATT AEF +C)-IL AEF Calculate the attenuation difference ΔIL of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters AEF ; C is the threshold value.

5. The parameter design method of the hybrid electromagnetic interference filter as claimed in claim 4, characterized in that: The S231 includes: Using the formula Calculate the actual attenuation IL of the passive EMI filter under the control of the current passive device parameters PEF ; Using the formula Calculate the actual attenuation IL of the hybrid electromagnetic interference filter under the control of the current passive device parameters and the current active control parameters AEF ; Among them, I q1 is the common mode current in the hybrid electromagnetic interference filter without an EMI filter, I q2 is the common mode current in the hybrid electromagnetic interference filter when only the passive EMI filter is present, I q2 It is the common mode current in the scenario where the passive EMI filter and the active EMI filter exist in the hybrid electromagnetic interference filter.

6. The parameter design method of the hybrid electromagnetic interference filter according to claim 1, characterized in that: The sampling link parameters include: the primary-to-secondary coil turns ratio of the sampling link in the active EMI filter.

7. The parameter design method of the hybrid electromagnetic interference filter according to claim 6, characterized in that: The signal amplification link parameters include: the sampling resistance value and the inverting amplification gain of the signal amplification link in the active EMI filter.

8. The parameter design method of the hybrid electromagnetic interference filter according to claim 6, characterized in that: The interference compensation link parameters include: an equivalent circuit and an equivalent capacitance of the interference compensation link in the active EMI filter.

9. A parameter design device for a hybrid electromagnetic interference filter, characterized in that: include: An initial setting module, used for setting initial passive device parameters of a passive EMI filter in a hybrid electromagnetic interference filter; An adjustment and optimization module, used for adjusting the common mode inductance in the initial passive device parameters until a target passive device parameter corresponding to a minimum common mode inductance that meets a preset condition is found; During the adjustment process, the current active control parameters corresponding to the current passive device parameters, and the difference between the minimum attenuation required and the actual attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive device parameters and the current active control parameters are obtained; the preset condition is: under the control of the target passive device parameters and their corresponding target active control parameters, the attenuation difference corresponding to the hybrid electromagnetic interference filter in the frequency band of interest is less than a threshold value; A parameter design module is used to use the target passive device parameters as the target design parameters of the passive EMI filter; and use the sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as the target design parameters of the active EMI filter in the hybrid electromagnetic interference filter.

10. A parameter design system for a hybrid electromagnetic interference filter, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

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