A parameter design method, device and system of a hybrid electromagnetic interference filter

Abstract

The application discloses a parameter design method, device and system of a hybrid electromagnetic interference filter, and belongs to the technical field of power electronic control. The parameter design method comprises the following steps: adjusting common-mode inductance in initial passive device parameters until target passive device parameters corresponding to minimum common-mode inductance satisfying a preset condition are found; the preset condition is that, under control of the target passive device parameters and corresponding target active control parameters, a difference between corresponding attenuation degrees of the hybrid electromagnetic interference filter in the concerned frequency band is less than a threshold value; and the target passive device parameters and the corresponding target active control parameters are output. The application takes the attenuation degree of the concerned frequency band as a target, so that the attenuation degree of the HEF can be maximally approximated to the difference between actual interference and standard limit value, and unnecessary redundant design is effectively avoided. The adaptive process of the attenuation degree can fully develop the interference attenuation performance of the AEF, and reduce the performance requirement on the PEF.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power electronic control, and more particularly, to a parameter design method, device and system of a hybrid electromagnetic interference filter. BACKGROUND

[0002] The operation of power electronic devices is based on the principle of pulse width modulation, and the power switch operates in a high-speed on-off state. This inherent switching mode generates a large voltage jump (dv / dt) and current jump (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, and in high-power density scenarios, the narrow space and compact layout will result in more serious coupling between EMI sources and paths, and between paths. In particular, the common-mode EMI of the power electronic device is further deteriorated, resulting in problems such as leakage current, radiation interference emission, and abnormal operation of sensitive equipment, and it is more difficult to meet electromagnetic compatibility standards.

[0003] To limit the common-mode EMI of high-power density power electronic devices, a corresponding EMI filter must be added to its propagation path. Passive EMI filters are the most thoroughly researched and widely used EMI filters, which use the frequency characteristics of inductors and capacitors to block and shunt EMI. However, related standards require that the ground leakage current not exceed a certain level to avoid electric shock, so the common-mode capacitance value in the PEF is strictly limited, and its performance mainly depends on the common-mode inductance. When the magnetic core material is determined, the volume and weight of the common-mode inductance will increase with the decrease of the cutoff frequency, even comparable to the power conversion circuit part, which is contrary to the goal of high power density of power electronic devices. To improve the cutoff frequency of the PEF, active EMI filters have been applied to the suppression of common-mode EMI. The active EMI filter (AEF) is based on the principle of detection and cancellation, injecting a signal equal and opposite to the common-mode current in the interference loop, which can achieve good interference suppression effect in the low and medium frequency band; however, due to 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, which combines the characteristics and advantages of AEF and PEF, improves the cutoff frequency of PEF, and makes up for the defects of insufficient suppression ability of AEF in high frequency band, and is the main development direction of EMI filter at present.

[0004] However, the design of HEF is based on the maximum value of the required attenuation degree, but in actual devices, the common mode interference has multiple resonance peaks in the standard specified frequency band, which makes the design oriented to the maximum attenuation degree have a large attenuation degree redundancy in other frequency bands, indicating that the interference suppression capability of HEF has not been fully developed, and it is urgent to use a reasonable design method to fully utilize the limited filter resources. SUMMARY

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

[0006] To achieve the above-mentioned purpose, according to one aspect of the present application, a parameter design method of a hybrid electromagnetic interference filter is provided, comprising:

[0007] S1: setting initial passive device parameters of a 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 satisfying the preset condition are found; in the adjustment process, the current active control parameters corresponding to the current passive device parameters are obtained, and the difference between the required minimum attenuation degree and the actual attenuation degree of the hybrid electromagnetic interference filter in the concerned frequency band under the control of the current passive device parameters and the current active control parameters is obtained; the preset condition is that the difference in the attenuation degree corresponding to the hybrid electromagnetic interference filter in the concerned frequency band under the control of the target passive device parameters and the target active control parameters corresponding thereto is less than a threshold value;

[0009] S3: taking the target passive device parameters as the target design parameters of the passive EMI filter; taking 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 comprises:

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

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

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

[0014] S24: if the difference between the corresponding attenuation degrees of the hybrid electromagnetic interference filter in the frequency band of interest under the current active control parameter and the current passive device parameter control are both less than a threshold value, continue to decrease the common mode inductance; otherwise, increase the common mode inductance, and if the difference between the corresponding attenuation degrees of the hybrid electromagnetic interference filter in the frequency band of interest under the current active control parameter and the current passive device parameter control after increasing the common mode inductance are both less than the threshold value, continue to increase the common mode inductance until the difference between the corresponding attenuation degrees of the hybrid electromagnetic interference filter in the frequency band of interest under the current active control parameter and the current passive device parameter control after increasing the common mode inductance are not both less than the threshold value;

[0015] S25: taking the common mode inductance in the second last iteration as the target passive device parameter, and taking the current active control parameter corresponding to the target passive device parameter as the target active control parameter.

[0016] In one of the embodiments, the obtaining of the current active control parameter corresponding to the current passive device parameter comprises:

[0017] taking the common mode inductance in the current passive device parameter as an initial value of an optimization model, taking a target function of the optimization model, taking the current active control parameter as a decision variable of the optimization model, and taking a circuit requirement of the active EMI filter as a penalty function of the optimization model;

[0018] iterating the optimization model until the current active control parameter corresponding to the difference between the attenuation degrees in the frequency band of interest being less than the threshold value is found;

[0019] wherein f1 and f n represent a first frequency point and a last frequency point in a standard frequency band, ΔIL represents an assignment value corresponding to the difference between the attenuation degrees of the current frequency point, C is the threshold value, and ΔIL AEF is the difference between the attenuation degrees.

[0020] In one of the embodiments, the S23 comprises:

[0021] S231: obtaining an actual attenuation degree IL PEF of the passive EMI filter under the current passive device parameter control and an actual attenuation degree ILAEF ;

[0022] S232: Using 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 embodiment, 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 parameter comprises 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 application, there is provided a parameter design device for a hybrid EMI filter, comprising:

[0032] An initial setting module is configured to set initial passive device parameters of a passive EMI filter in the hybrid EMI filter.

[0033] An adjustment and optimization module is configured to adjust common mode inductance in the initial passive device parameters until a target passive device parameter corresponding to a minimum common mode inductance satisfying a preset condition is found; during the adjustment process, a current active control parameter corresponding to a current passive device parameter is obtained, and a difference between a required minimum attenuation degree and an actual attenuation degree of the hybrid EMI filter in a frequency band of interest under control of the current passive device parameter and the current active control parameter is obtained; the preset condition is that corresponding attenuation degree differences of the hybrid EMI filter in the frequency band of interest under control of the target passive device parameter and a target active control parameter corresponding to the target passive device parameter are all less than a threshold value.

[0034] A parameter design module is configured to take the target passive device parameter as a target design parameter of the passive EMI filter, and take a sampling link parameter, a signal amplification link parameter and an interference compensation link parameter in the target active control parameter as target design parameters of the active EMI filter.

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

[0036] According to another aspect of the present application, there is provided a computer readable storage medium, which stores a computer program, and the computer program implements steps of the method when executed by a processor.

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

[0038] (1)The application provides a parameter design method of a hybrid electromagnetic interference filter, wherein a common mode inductance in initial passive device parameters is adjusted until a target passive device parameter corresponding to a minimum common mode inductance meeting a preset condition is found; in the adjustment process, a current active control parameter corresponding to the current passive device parameter is obtained, and a difference between a required minimum attenuation degree and an actual attenuation degree of the hybrid electromagnetic interference filter in a frequency band of interest under the current active control parameter and the current passive device parameter control is obtained; the application takes the attenuation degree in the frequency band of interest as a target, so that the attenuation degree of the HEF can be maximally approximated to the difference between the actual interference and the standard limit value, and unnecessary redundant design is effectively avoided. The self-adaptive process of the attenuation degree in the process of obtaining the current active control parameter corresponding to the current passive device parameter can fully develop the interference attenuation performance of the AEF, reduce the performance requirement on 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 cost and strong migration.

[0039] (2)In the scheme, initial HEF conditions are given for optimization iteration, that is, the common mode inductance L CM and the current active control parameter KP, if the standard is met at this time, that is, the attenuation degree difference ΔIL AEF <0, L CM is reduced and the iteration continues; if the iteration result cannot meet the standard, the last iteration result KP and L CM are taken as the final output value. The above optimization method is simple in operation and low in calculation complexity, and can quickly find the optimal common mode inductance L CM and the corresponding active control parameter KP.

[0040] (3)The scheme takes the common mode inductance in the current passive device parameter as an initial value of an optimization model, takes ΔIL as a target function of the optimization model, takes the current active control parameter as a decision variable of the optimization model, and takes the circuit requirement of the active EMI filter as a penalty function of the optimization model; the above optimization model can quickly and accurately provide a search direction of the current active control parameter KP, but whether the convergence value meets the standard requirement still needs to be judged in combination with ΔIL AEF .

[0041] (4)The scheme calculates the required minimum attenuation degree ATT AEF of the active EMI filter by using the formula ATT CM =N PEF -Std-IL AEF , which can accurately quantify the target attenuation degree and provide support for the target function of the optimization algorithm, so that the optimization of the active control parameter is realized at the beginning of the AEF design.

[0042] (5) The present scheme uses the formula and to calculate the actual attenuation degree IL of the passive EMI filter and the active EMI filter PEF and IL AEF , which can decouple the interference attenuation effect of the AEF and the PEF, so that the quantitative relationship between the active control parameter and IL AEF can be separately concerned based on simulation and experiment, and the iteration optimization process of the active control parameter is realized in combination with the target of the attenuation degree.

[0043] (6) The sampling link parameters include the primary and secondary coil turn 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; and the interference compensation link parameters include the equivalent circuit and the equivalent capacitance of the interference compensation link in the active EMI filter; in this way, the control parameters that are easy to adjust and have a significant influence on the attenuation degree in the circuit can be fully considered, the control freedom degree of the hybrid electromagnetic interference filter is improved, and the flexibility and high controllability of the EMI filter are realized. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a flowchart of the parameter design method of the hybrid electromagnetic interference filter provided in Embodiment 1 of the present application;

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

[0046] Figure 3 is an equivalent circuit diagram of the common-mode path after the HEF is adopted, provided in Embodiment 1 of the present application;

[0047] Figure 4 is an equivalent circuit diagram of the CT circuit provided in Embodiment 1 of the present application;

[0048] Figure 5 is a comparison diagram of the key link frequency response modeling result and the network analyzer measurement result, provided in Embodiment 1 of the present application;

[0049] Figure 6 is a comparison diagram of the key impedance modeling result and the impedance meter measurement result, provided in Embodiment 1 of the present application;

[0050] Figure 7 is a simplified equivalent circuit diagram before and after the EMI filter is adopted, provided in Embodiment 1 of the present application;

[0051] Figure 8 is an open-loop gain and closed-loop gain effect diagram of the operational amplifier, provided in Embodiment 1 of the present application;

[0052] Figure 9 Frequency response diagram of CT provided for embodiment 1 of the present application;

[0053] Figure 10 Variation diagram of frequency response of CT and operational amplifier when changing parameters provided for embodiment 1 of the present application;

[0054] Figure 11 Target function composition and iteration process diagram of optimization algorithm provided for embodiment 1 of the present application;

[0055] Figure 12 Flow chart of HEF design method with adaptive attenuation degree provided for embodiment 1 of the present application;

[0056] Figure 13 Simulation diagram of HEF design flow provided for embodiment 1 of the present application;

[0057] Figure 14 Measured frequency spectrum diagram of iteration optimization AEF parameters when PEF is constant provided for embodiment 1 of the present application;

[0058] Figure 15 Measured frequency spectrum diagram after optimization of PEF parameters provided for embodiment 1 of the present application. DETAILED DESCRIPTION

[0059] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0060] Embodiment 1

[0061] As Figure 1As shown, the embodiment provides a parameter design method of a hybrid electromagnetic interference filter, the hybrid electromagnetic interference filter comprising a passive electromagnetic interference filter and an active electromagnetic interference filter; the parameter design method comprising: S1: setting initial passive device parameters of the passive electromagnetic interference filter in the hybrid electromagnetic interference filter; S2: adjusting common-mode inductance in the initial passive device parameters until finding target passive device parameters corresponding to minimum common-mode inductance satisfying a preset condition; in the adjusting process, obtaining current active control parameters corresponding to current passive device parameters, and a difference between a required minimum attenuation degree and an actual attenuation degree of the hybrid electromagnetic interference filter in a concerned frequency band under control of the current passive device parameters and the current active control parameters; the preset condition being that corresponding attenuation degree differences of the hybrid electromagnetic interference filter in the concerned frequency band under control of the target passive device parameters and target active control parameters corresponding to the target passive device parameters are all less than a threshold; S3: taking the target passive device parameters as target design parameters of the passive electromagnetic interference filter; and taking sampling link parameters, signal amplification link parameters and interference compensation link parameters in the target active control parameters as target design parameters of the active electromagnetic interference filter in the hybrid electromagnetic interference filter.

[0062] It should be understood that although Figure 1 the steps in the flowcharts are shown in sequential order, such that one step necessarily precedes another step, the steps do not necessarily have to be performed in the order shown. Unless explicitly stated, the steps can be performed in any order, and the steps can be performed in other sequences than the order shown. Moreover, Figure 1 At least some of the steps in the flowcharts can include multiple sub-steps or multiple stages, which do not necessarily have to be performed at the same time, but can be performed at different times, and the order of the sub-steps or stages does not necessarily have to be sequential, but can be performed in rotation or alternation with at least some of the other steps or sub-steps or stages of other steps.

[0063] A common-mode interference path of a typical bridge inverter is shown in Figure 2 As shown, the high-speed on-off of the power switch causes a large voltage jump dv / dt at the midpoint of the bridge arm, and through the parasitic capacitance C p induces a common-mode current i CM As shown in formula (1).

[0064]

[0065] Considering the nature of the common-mode interference source, it can be equivalent to a voltage source in circuit analysis, while the ground capacitance C p and other parasitic parameters such as lead inductance together form the common-mode source impedance Z CM . Subsequently, the common-mode current i CM is protected by the device and returns to the line impedance stabilization network (LISN) and ultimately to the DC bus. The role 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.

[0066] Subsequently, an active EMI filter (AEF) is designed according to the common-mode interference path. The AEF has three components inside: a sampling component, a signal amplification component, and a compensation component. 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 component is usually composed of operational amplifiers and push-pull amplifiers, which can reverse and power amplify the signal collected by the CT; the compensation component is an RC branch, which can isolate the AEF internal analog circuit from the DC power loop, while injecting the amplified compensation signal into the interference loop. The equivalent common-mode interference loop after inserting the AEF is shown in Figure 3 . Figure 4 The equivalent circuit diagram of CT can be seen that CT converts the common-mode current i CM into the input voltage U in of the signal amplification component, where C pp and C sp are the parasitic capacitances of the primary and secondary sides, L m is the excitation inductance, R c is the equivalent resistance representing the loss, L l and R p are the lead inductance and resistance. The transfer function can be expressed as equation (2).

[0067]

[0068] Similarly, equation (3) represents the transfer function of the signal amplification component, 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 queried in the technical manual, Z in is the input impedance of the push-pull amplifier, Z o is the output impedance of the operational amplifier, and usually Z in is much larger than Z o , so the third term on the right side of equation (3) can be considered 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 within the frequency band of interest of 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 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 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 Adding common-mode inductance, if the difference between the current passive device parameters corresponding to the addition of the common-mode inductance and the attenuation of the hybrid electromagnetic interference filter under the control of the current active control parameters in the frequency band of interest is both less than a threshold, then 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 of the hybrid electromagnetic interference filter under the control of the current active control parameters in the frequency band of interest is not both less than the threshold; S25: using the common-mode inductance in the penultimate iteration as the target passive device parameter; using 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 electromagnetic interference 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] To effectively play the interference compensation effect of AEF, a mathematical model representing the attenuation degree needs to be established. Since the ultimate goal is to pass the EMC standard, the requirements of AEF attenuation degree are first expressed. The requirements that the attenuation degree of AEF should meet are shown in equation (4).

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

[0073] Wherein, IL AEF is the actual attenuation degree provided by AEF, N CM is the common-mode interference amplitude, Std is the EMC standard limit value, IL PEF is the actual attenuation degree provided, and ATT AEF is the required minimum attenuation degree that AEF should provide. To meet the EMC standard, equation (4) needs to be met at each frequency point in the frequency band specified by it. For ease of mathematical expression, ΔIL AEF is defined as shown in equation (5).

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

[0075] It represents the difference between the attenuation degree provided by AEF and the required attenuation degree, and ΔIL AEF is positive, indicating that the attenuation degree provided by AEF is insufficient to meet the EMC standard. Wherein ATT AEF +6 represents adding a limit of 6dB on the basis of the EMC limit value.

[0076] As an optional implementation, S231 includes: calculating the actual attenuation degree IL PEF of the passive EMI filter under the control of the current passive device parameters by using equation ; calculating the actual attenuation degree IL AEF of the hybrid electromagnetic interference filter under the control of the current passive device parameters and the current active control parameters by using equation ; wherein, I q1 is the common-mode current in the hybrid electromagnetic interference filter under the scenario of no EMI filter, I q2 is the common-mode current in the hybrid electromagnetic interference filter under the scenario of only passive EMI filter, and I q is the common-mode current in the hybrid electromagnetic interference filter under the scenario of existing passive EMI filter and active EMI filter.

[0077] Based on the common-mode interference path, Figure 7The equivalent circuits of three cases, i.e. without EMI filter, with PEF and with HEF, are compared, where Z out is the output impedance of the push-pull amplifier, Z comp is the equivalent impedance of the compensation circuit, Z L is the impedance of the common-mode inductor, and V AEF is the voltage at the output of the push-pull amplifier. Based on this, the attenuation of PEF, AEF and HEF can be calculated by using Kirchhoff's law, as shown in equations (6), (7) and (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 CT and the frequency response of the signal amplification link.

[0081] As optional implementation, the sampling link parameters include the primary-to-secondary 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; and the interference compensation link parameters include the equivalent circuit and the equivalent capacitance of the interference compensation link in the active EMI filter.

[0082] Figure 8 is the comparison between the open-loop gain and the closed-loop gain of the operational amplifier, G a1 and G a2 represent two different closed-loop gains. The gain-bandwidth product (GBW) is the intersection of the open-loop gain and the abscissa, and the greater the GBW is, the better the high-frequency response performance of the operational amplifier is, which is related to the internal process of the operational amplifier; meanwhile, the GBW represents the product of the closed-loop gain and its corresponding bandwidth, meaning that the two are inversely proportional when the operational amplifier is determined. Comparing G a1 and G a2 , G a1 has greater gain, but the frequency band A1 in which it can maintain constant gain is smaller than B1 corresponding to G a2 , and due to the influence of phase shift in the Δ interval, the effective gain of G a1 will be weakened. Therefore, starting from the attenuation of AEF, the increase of the gain of the operational amplifier will cause the attenuation in different frequency bands to change in the opposite direction. Similarly, Figure 9 is the frequency response diagram of CT, and the increase of the gain of CT will also cause the constant gain frequency band to shrink, so in the Δ interval, the actual effective value of the greater gain G c1 after phase shift is only G1eff , instead of G c2 , resulting in opposite changes of the final AEF attenuation in different frequency bands. Figure 10 The frequency responses of the op-amp and the CT are integrated, and the effects of different parameter changes are compared; for example, when the sampling resistor R sense is increased, the gain is increased by about 6 dB at most, but the phase is more deviated after 1 MHz and before 200 kHz compared with the control group. The above analysis shows that when the response of a single link in the AEF changes, it will bring different effects on the attenuation of the AEF in different frequency bands; and the key parameter that affects the response of these links is defined as KP, as shown in formula (9). Obviously, considering the wide frequency band of interest, the effect of parameter changes on the attenuation is difficult to calculate directly by formula (6), formula (7) and formula (8), and a more simple and feasible method needs to be designed, that is, the current active control parameter can be represented by formula (9).

[0083]

[0084] As an optional implementation, the current active control parameter corresponding to the current passive device parameter is obtained, including: taking the common-mode inductance in the current passive device parameter as the initial value of the optimization model, taking as the objective function of the optimization model, taking the current active control parameter as the decision variable of the optimization model, and taking the circuit requirement of the active EMI filter as the penalty function of the optimization model; iteratively optimizing the optimization model until the current active control parameter corresponding to the attenuation difference value less than the threshold value in the frequency band of interest is found; wherein f n represent the first and last frequency points in the standard frequency band, ΔIL represents the attenuation difference value corresponding to the assignment, C is the threshold value, and ΔIL AEF is the attenuation difference value.

[0085] Considering the corresponding relationship between KP and IL AEF , the above problem can be expressed as: finding a KP, so that IL AEF satisfies formula (4). Further, since IL AEF can uniquely determine ΔIL AEF , the problem can be further transformed as: finding a KP, so that ΔIL AEFIn the concerned frequency band are less than zero. Can use optimization algorithm to realize the search of KP, optimization algorithm has three elements: decision variable, objective function and penalty function; Among them: the objective function is the object of iterative optimization algorithm, usually search minimum value in single objective optimization; Decision variable is the independent variable corresponding to the objective function; Penalty function is the function of restricting the change range of decision variable. In this design, the decision variable is KP, the penalty function is limited by the circuit requirements, such as the size of the ground leakage current, the voltage of the operational amplifier cannot be saturated, and the stability of the control loop. Formula (10) defines the objective function formula (OF), where f1 and f n represent the first and last frequency points in the standard frequency band, and ΔIL is defined by formula (11). ΔIL is assigned according to the ΔIL AEF of a certain frequency point, if ΔIL AEF is greater than zero, then the square form is used to greatly increase ΔIL, because at this time it represents that the EMC standard cannot be met at this frequency point; if ΔIL AEF is less than -6dB, then ΔIL is equal to zero, because at this time it represents that the standard is met at this frequency point and there is a 6dB margin; if ΔIL AEF is between -6dB and 0, then ΔIL is given a small weight as a transition interval.

[0086]

[0087] Figure 11 The OF has the advantage of quantifying the interference exceeding the standard in the concerned frequency band as the area surrounded by ΔIL and the horizontal axis. Before iteration, as shown in Figure 11 , because there is an interval that does not meet the standard, the area surrounded by ΔIL and the horizontal axis, that is, the OF value is large; after iteration optimization of OF, as shown in Figure 11 , at this time OF is greatly reduced, and the attenuation degree 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 AEF is strongly related to the reduction of the concerned frequency band, but it cannot be guaranteed that the minimum value of OF can meet the standard requirements. This is because OF depends on the attenuation degree of AEF, and from formula (7) it can be seen that the attenuation degree of AEF is also related to PEF, so when PEF is too small or the design is unreasonable, the optimization of AEF alone cannot meet the EMC standard. Therefore, this algorithm can provide the direction of searching for AEF parameters KP, but whether the convergence value meets the standard requirements still needs to be judged by ΔIL AEF . This design uses genetic algorithm formula (GA), which has excellent performance in single objective optimization processing and has been widely applied.

[0088] Figure 12 The flow of HEF adaptive attenuation degree design based on the above optimization algorithm is shown. First, given the initial HEF condition for optimization iteration, that is, L CM With KP, if the standard is met at this time, that is, the attention frequency band ΔIL AEF <0, reduce L CM The value continues to iterate; if the iteration result cannot meet the standard, then the last iteration result KP and L CM As the final output value. Figure 13 The above process is simulated by simulation. First, according to the initial parameters, calculate IL PEF And IL AEF , combined with the simulation of the interference source and the standard limit value, calculate ΔIL AEF At this time, ΔIL AEF In the low frequency band is greater than zero, which means that in this frequency band, the standard is not met; then, the optimized KP is calculated using the optimization algorithm, at this time, the corresponding ΔIL AEF In the target frequency band are less than zero, however, there is a large attenuation degree redundancy in the middle and high frequency band, which shows that the filter parameters can be further optimized at this time. Finally, reduce the common mode inductance L CM And continue to iterate to achieve smaller attenuation degree redundancy until L CM The value is small enough to make KP unable to meet the standard no matter how it is iterated, and the last KP and its corresponding L CM To design HEF.

[0089] Figure 14 For the experimental results of using the optimization algorithm to iterate KP, it can be seen that after the parameter optimization of AEF, the common mode interference that cannot pass the standard can meet the standard. It is noted that the optimized interference spectrum is reduced in the frequency band that exceeds the standard before optimization, but is increased in the low frequency band, which further shows that the AEF attenuation degree adjustability will lead to different trends of attenuation degree in different frequency bands, and the significance of the optimization algorithm is to make the attenuation degree iterate in the direction that the interference meets the standard, which crosses the limitation of traditional HEF design only for the maximum attenuation degree.

[0090] Further, Figure 14 The optimized interference spectrum in the above Figure 15 The results of reducing the PEF parameters and then optimizing are shown, at this time, the common mode inductance is smaller than Figure 14The case of the interference is reduced by 73%. It can be seen that the interference still meets the standard and leaves a 6dB margin, while the common-mode interference is closer to the standard limit in the concerned frequency band. Obviously, this process is to adaptively design the attenuation degree of the AEF according to the actual interference, so as to maximize the ability of the HEF and reduce the unnecessary design redundancy of the filter; and, under the premise of meeting the standard, the minimum value of the common-mode inductance is obtained, so as to minimize the volume and weight of the PEF, and realize the improvement of the power density of the device.

[0091] Embodiment 2

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

[0093] The initial setting module is configured to set initial passive device parameters of the passive EMI filter in the hybrid electromagnetic interference filter.

[0094] The adjustment optimization module is configured to adjust the common-mode inductance in the initial passive device parameters until a target passive device parameter corresponding to a minimum common-mode inductance meeting a preset condition is found; in the adjustment process, a current active control parameter corresponding to the current passive device parameter is obtained, and a difference between a required minimum attenuation degree and an actual attenuation degree of the hybrid electromagnetic interference filter in the concerned frequency band under control of the current passive device parameter and the current active control parameter is obtained; the preset condition is that, under control of the target passive device parameter and a target active control parameter corresponding to the target passive device parameter, the difference between the attenuation degree and the actual attenuation degree of the hybrid electromagnetic interference filter in the concerned frequency band is less than a threshold value.

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

[0096] The division of each module in the parameter design device of the hybrid electromagnetic interference filter is only used for illustration, and 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 parameter design device of the hybrid electromagnetic interference filter.

[0097] The specific limitations of the parameter design device of the hybrid electromagnetic interference filter can refer to the limitations of the parameter design method of the hybrid electromagnetic interference filter described above, and will not be repeated here. Each module in the parameter design device of the hybrid electromagnetic interference filter described above can be realized by software, hardware and a combination thereof in whole or in part. The above-mentioned modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to each of the above modules.

[0098] Embodiment 3

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

[0100] Embodiment 4

[0101] The embodiment provides a computer readable storage medium, which stores a computer program, and the steps of the method are implemented when the computer program is executed by a processor.

[0102] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A parameter design method for a hybrid electromagnetic interference filter, characterized in that: include: S1: Set the 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 a target passive device parameter corresponding to a minimum common-mode inductance that satisfies a preset condition is found; during the adjustment process, obtaining a current active control parameter corresponding to the current passive device parameter, and a difference between a required minimum attenuation and an actual attenuation of the hybrid electromagnetic interference filter within a frequency band of interest under the control of the current passive device parameter and the current active control parameter; the preset condition being that, under the control of the target passive device parameter and its corresponding target active control parameter, the corresponding attenuation difference of the hybrid electromagnetic interference filter within the frequency band of interest is less than a threshold value; S3: Using the target passive device parameters as 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 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 component parameters to obtain current passive component parameters; S22: Obtain current active control parameters corresponding to current passive device parameters; S23: Calculating the difference between the minimum attenuation required by the hybrid electromagnetic interference filter and the actual attenuation within the frequency band of interest under the control of the current active control parameters and the current passive component parameters; S24: If the difference between the 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 component parameters is less than a threshold value, then continue to reduce the common-mode inductance; otherwise, increase the common-mode inductance. If the difference between the attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive component parameters and the current active control parameters after the common-mode inductance is increased is less than the threshold value, then continue to increase the common-mode inductance until the difference between the attenuation of the hybrid electromagnetic interference filter in the frequency band of interest under the control of the current passive component parameters and the current active control parameters after the common-mode inductance is not 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, and 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 a current active control parameter corresponding to which the attenuation difference within 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, and 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 according to 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 component 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 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 according to 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, wherein: 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 to set initial passive device parameters of the passive EMI filter in the hybrid electromagnetic interference filter; An adjustment and optimization module, configured to adjust the common-mode inductance in the initial passive component parameters until a target passive component parameter corresponding to a minimum common-mode inductance that meets a preset condition is found; During the adjustment process, current active control parameters corresponding to current passive device parameters, as well as a difference between a required minimum attenuation and an actual attenuation of the hybrid electromagnetic interference filter within a frequency band of interest under the control of the current passive device parameters and the current active control parameters, are obtained; the preset condition being that, under the control of the target passive device parameters and their corresponding target active control parameters, the corresponding attenuation differences of the hybrid electromagnetic interference filter within the frequency band of interest are all 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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