Common-mode current prediction method, detection system, computing device and medium
Through the two-port equivalent model and external impedance settings, the common mode current equivalent noise source of the electric drive system is quickly calculated, which solves the problems of complex and long periods of the common mode current prediction model of the electric drive system and improves the prediction efficiency.
Patent Information
- Application Number
- CN202411350936.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2025-01-17
AI Technical Summary
In the prior art, the common mode current prediction model of electric drive systems is complex, and the modeling and prediction periods are long, which leads to time-consuming and labor-intensive.
The two-port equivalent model is adopted to equivalent the electrical control of the electric drive system into a two-port model. By setting extremely large and extremely small external impedances, the equivalent noise source is quickly calculated, which simplifies the modeling process and shortens the prediction time.
The common mode current prediction process of the electric drive system is simplified, the problem of model layout complexity and long periods is reduced, and the prediction efficiency is improved.
Smart Images
Figure CN119322194A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of automobile technology, and in particular to a common-mode current prediction method, a detection system, a computing device and a medium. Background Art
[0002] As an important power device in new energy vehicles, the electric drive system generates a lot of interference due to its high voltage and high frequency of the internal insulated gate bipolar transistor (IGBT). Common mode current is the main source of radiated interference, so it is very important to predict the common mode current of the electric drive system.
[0003] At present, predicting the common-mode current of the electric drive system requires the establishment of a precise model, and the establishment of a precise model often requires the extraction of a large number of parameters. An inaccurate parameter will affect the entire prediction result, which is very time-consuming and labor-intensive. Therefore, the existing technology still has problems such as complex modeling and long modeling and prediction cycles. Summary of the invention
[0004] Based on this, the present application provides a common-mode current prediction method, detection system, computing device and medium, which can improve the problems of complex modeling and long modeling and prediction cycle existing in the prior art.
[0005] In a first aspect, the present application provides a common-mode current prediction method, which includes: after putting a magnetic ring on the DC end and three-phase end of the electric control of the electric drive system to obtain the maximum external impedance, obtaining the equivalent common-mode current of the electric drive system when the maximum external impedance is set; the electric control is equivalent to a two-port model to calculate the first equivalent noise source based on the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set; when the magnetic ring has been removed and the electric drive system is set with any external filter, predicting the common-mode current when any external filter is set according to the first equivalent noise source.
[0006] In combination with the first aspect, in a first possible implementation mode of the first aspect, before the magnetic ring is put on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance, the aforementioned common-mode current prediction method also includes: connecting the two ends of the electric control respectively through a network analyzer to obtain the S parameters of the electric control; the electric control is equivalent to a two-port model, and the Z parameters are calculated based on the S parameters; the magnetic ring is selected based on the Z parameters so that the impedance of the magnetic ring is much larger than the Z parameters.
[0007] In combination with the first aspect, in a second possible implementation of the first aspect, the electric control is equivalent to a two-port model, so as to calculate a mathematical expression of the first equivalent noise source according to the maximum external impedance and the equivalent common mode current of the electric control when the maximum external impedance is set, including: V Ni =-icmi *Z in , V No =-i cmo *Z out ; Among them, V Ni It is the first equivalent noise source of the DC end of the electronic control. cmi is the common mode current at the DC end of the electronic control, Z in is the external impedance of the DC terminal of the electronic control, V No It is the first equivalent noise source of the three-phase terminal of the electric control. cmo is the common mode current of the three-phase terminal of the electronic control and Z out is the external impedance of the three-phase terminal of the electronic control, Z in and Z out Much larger than the Z parameter.
[0008] In combination with the first aspect, in a third possible implementation manner of the first aspect, before predicting the common-mode current when any external filter is set based on the first equivalent noise source, the common-mode current prediction method further includes: after setting the capacitor at the DC end and the three-phase end of the electric control of the electric drive system to obtain the minimum external impedance, obtaining the equivalent common-mode current of the electric drive system when the minimum external impedance is set; the electric control is equivalent to a two-port model to calculate the second equivalent noise source based on the Z parameter of the electric control of the electric drive system and the equivalent common-mode current when the minimum external impedance is set; and the first equivalent noise source is corrected using the second equivalent noise source, so that the common-mode current when any external filter is set is predicted based on the corrected first equivalent noise source.
[0009] In combination with the third possible implementation of the first aspect, in a fourth possible implementation of the first aspect, the electric control is equivalent to a two-port model, and a mathematical expression of the second equivalent noise source is calculated according to the Z parameter of the electric control of the electric drive system and the equivalent common mode current when the minimum external impedance is set, including: V Ni =-i cmi *(Z 11 +Z 12 ), V No =-i cmo *(Z 21 +Z 22 ), where V Ni is the equivalent noise source at the DC end of the electronic control, i cmi is the common mode current at the DC end of the electronic control, Z 11 is the input impedance of the DC terminal of the electronic control, Z 12 is the transfer impedance from the DC end to the three-phase end of the electronic control, V No is the equivalent noise source of the three-phase terminal of the electronic control, i cmo is the common mode current of the three-phase terminal of the electronic control, Z 21 is the transfer impedance from the three-phase end to the DC end of the electronic control and Z22 is the input impedance of the three-phase terminal of the electronic control, Z in and Z out Much smaller than the Z parameter.
[0010] In combination with the third possible implementation method of the first aspect, in a fifth possible implementation method of the first aspect, the step of correcting the first equivalent noise source using the second equivalent noise source includes: determining whether the difference between the first equivalent noise source and the second equivalent noise source is greater than a threshold value; if the difference is greater than the threshold value, taking the equivalent noise source close to the resonance point between the first equivalent noise source and the second equivalent noise source as the corrected first equivalent noise source; if the difference is less than or equal to the threshold value, calculating the average value of the first equivalent noise source and the second equivalent noise source to obtain the corrected first equivalent noise source.
[0011] In the second aspect, the present application also provides a detection system, which includes: a first fixing tool for fixing the magnetic ring to the DC end and the three-phase end of the electric control of the electric drive system; an EMI receiver for detecting the equivalent common-mode current of the electric drive system when the maximum external impedance is set; a computing device is connected to the EMI receiver, and the computing device is used to execute the common-mode current prediction method of any of the aforementioned embodiments or implementation methods.
[0012] In the third aspect, the present application also provides a computer device, which includes an acquisition unit for obtaining the equivalent common-mode current of the electric drive system when the maximum external impedance is set after the magnetic ring is put on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance; a detection unit for equating the electric control to a two-port model to calculate a first equivalent noise source based on the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set; a prediction unit for predicting the common-mode current when any external filter is set based on the first equivalent noise source when the magnetic ring has been removed and any external filter is set in the electric drive system.
[0013] In a fourth aspect, the present application also provides a computing device, which includes a processor and a memory, wherein the processor and the memory are connected via a bus; the processor is used to execute multiple instructions; the memory is used to store multiple instructions, and the instructions are suitable for being loaded by the processor and a common-mode current prediction method such as the first aspect or any one embodiment of the first aspect.
[0014] In a fifth aspect, the present application further provides a computer-readable storage medium, in which a plurality of instructions are stored, and the instructions are suitable for being loaded by a processor and executed by a common-mode current prediction method such as the first aspect or any one embodiment of the first aspect.
[0015] In summary, the present application provides a common-mode current prediction method, detection system, computing device and medium, wherein the present application puts a magnetic ring on the DC end and three-phase end of the electric control of the electric drive system, which will not damage the original structure of the wiring harness, and obtains a maximum external impedance. The maximum external impedance is much larger than the Z parameter when the electric control is equivalent to a two-port model. Therefore, when calculating the first equivalent noise source of the electric control, there is no need to consider the Z parameter, and the first equivalent noise source can be directly calculated quickly based on the maximum external impedance, so that when the electric drive system is subsequently set up with any external filter, the computing device can quickly predict the common-mode current when setting any external filter based on the first equivalent noise source, thereby simplifying the modeling process and shortening the prediction time, and improving the problems of complex modeling and long modeling and prediction cycles in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a schematic diagram of the structure of a two-port model in an embodiment of the present application;
[0017] Figure 2 This is a structural diagram of a two-port simplified model in an embodiment of the present application;
[0018] Figure 3 A schematic diagram of a common mode current prediction method in an embodiment of the present application;
[0019] Figure 4 This is a schematic diagram of a structure in which a large external impedance is set in an embodiment of the present application;
[0020] Figure 5 A schematic diagram of a structure for calculating a first equivalent noise source in an embodiment of the present application;
[0021] Figure 6 This is a schematic structural diagram of a first fixing tool in an embodiment of the present application;
[0022] Figure 7 A schematic diagram of the structure of the test S parameter in an embodiment of the present application;
[0023] Figure 8 This is a schematic structural diagram of a DC terminal clamp in an embodiment of the present application;
[0024] Fig. 9 This is a schematic structural diagram of a three-phase end clamp in an embodiment of the present application;
[0025] Fig.10 A schematic diagram of a common mode current prediction method in an embodiment of the present application;
[0026] Fig.11 This is a schematic structural diagram of a second fixing tool in an embodiment of the present application;
[0027] Fig.12 This is a schematic diagram of a structure in which extremely small external impedance is set in one embodiment of the present application;
[0028] Fig.13 It is a schematic diagram of a structure for calculating a second equivalent noise source in an embodiment of the present application. DETAILED DESCRIPTION
[0029] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application 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 application and are not used to limit the present application.
[0030] In view of the problems of high complexity and long cycle of model arrangement in the prior art, this application proposes a common mode current prediction method. First of all, it should be noted that this application adopts the idea of a two-port equivalent model, such as Figure 1 As shown, since the electric control is the main noise source of the electric drive system, this application equates the electric control of the electric drive system to a two-port model, that is, Figure 1 The unpredictable two-port in Z in and Z OUT To measure the external impedance of the offline impedance, further Figure 1 The two-port model is equivalent to Figure 2 The simplified prediction model of the electronic control system can be expressed as:
[0031] Formula 1:
[0032] Among them, V Ni It is the first equivalent noise source of the DC end of the electronic control. cmi is the common mode current at the DC end of the electronic control, Z in is the external impedance of the DC terminal of the electronic control, V No It is the first equivalent noise source of the three-phase terminal of the electric control. cmo is the common mode current of the three-phase terminal of the electronic control and Z out is the external impedance of the three-phase end of the electric control, and the Z parameter is the impedance parameter of the electric control. The Z parameter includes Z 11 , Z 12 , Z 21 and Z 22 , Z 11 is the input impedance of the DC terminal of the electronic control, Z 12 is the transfer impedance from the DC end to the three-phase end of the electronic control, Z 21 is the transfer impedance from the three-phase end of the electric control to the DC end, Z 22 It is the input impedance of the three-phase terminal of the electronic control.
[0033] Based on the above formula 1, it can be seen that after determining the equivalent noise source, when any external filter is replaced, the common-mode current of the electric drive system when any external filter is set can also be predicted based on the equivalent noise source and the change of external impedance. Formulas 2 and 3 for calculating the equivalent noise source can be converted from formula 1 to obtain:
[0034] Formula 2: V Ni =-i cmi *(Z in +Z 11 +Z 12 )
[0035] Formula 3: V No =-i cmo *(Z out +Z 21 +Z 22 )
[0036] Based on the above two-port model, this application proposes a method for predicting the maximum external impedance, which can quickly obtain an equivalent noise source. This application puts a magnetic ring on the DC end and three-phase end of the electric control of the electric drive system to obtain the maximum external impedance. The impedance Z of the maximum external impedance in and Z out Much larger than the Z parameter, specifically, Z in Adjust to be much larger than Z 11 With Z 12 , Z out Adjust to be much larger than Z 21 With Z 22 , so that there is no need to consider the Z parameter when calculating the equivalent noise source based on Formula 2 and Formula 3, and the first equivalent noise source can be quickly calculated based on the impedance of the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set. Moreover, the wiring harness between the electric control and other components is a shielded cable, which also makes it difficult to set the external impedance. If a common-mode inductor is to be added, the cable itself needs to be destroyed, so that other influencing factors are introduced into the prediction result. Therefore, when setting the magnetic ring, the present application only needs to pass the high-voltage wiring harness of the DC end and the three-phase end of the electric control through the magnetic ring, which will not damage the cable or the original internal structure of the electric control. Therefore, the present application reduces the complexity of the model layout, shortens the test cycle and efficiency, and improves the problems of high complexity and long cycle of the model layout in the prior art.
[0037] It should also be noted that the computing device proposed in this application can be a terminal device, a portable terminal, a computer, a server, etc., and this application does not limit this. In addition, the computing device can exchange data with other devices and execute the common-mode current prediction method proposed in this application.
[0038] In order to better understand the common-mode current prediction method proposed in this application, this application also provides an embodiment of the common-mode current prediction method, such as Figure 3 As shown, next, this application uses a computing device as an execution subject to illustrate the common mode current prediction method, specifically:
[0039] 311: After the magnetic ring is placed on the DC terminal and the three-phase terminal of the electric control of the electric drive system to obtain the maximum external impedance, the equivalent common mode current of the electric drive system when the maximum external impedance is set is obtained;
[0040] 321: Equivalently transforming the electric control into a two-port model, so as to calculate a first equivalent noise source according to the maximum external impedance and the equivalent common mode current of the electric control when the maximum external impedance is set;
[0041] 331: When the magnetic ring has been removed and any external filter is set in the electric drive system, predict the common mode current when any external filter is set according to the first equivalent noise source.
[0042] For step 311, if Figure 1 As shown, the electric drive system includes an electronic control and a motor. The electronic control includes a DC end and a three-phase end. The DC end of the electronic control is connected to a high-voltage DC power supply through a high-voltage DC line impedance stabilization network (LISN), and the three-phase end of the electronic control is connected to the motor. The electronic control converts the high-voltage DC power of the power supply into three-phase AC power for supply to the motor.
[0043] like Figure 4 As shown, the present application passes the high-voltage wire harness of the DC end and the three-phase end of the electric control through the magnetic ring, so that the magnetic ring, LISN and the motor form a large external impedance, which is much larger than the Z parameter. Specifically, Z in >>Z 11 +Z 12 , Z out >>Z 21 +Z 22 ;
[0044] After the magnetic ring is placed on the DC end and three-phase end of the electric control of the electric drive system to obtain a maximum external impedance, for example, based on Figure 5The detection system shown includes an electromagnetic interference (EMI) receiver, a computer and a first fixed tooling, the computer is a computing device, the computing device can be connected to the EMI receiver through the instrument control bus standard bus (GPIB, General Purpose Interface Bus), the computing device obtains the equivalent common mode current of the electric drive system when the maximum external impedance is set through the EMI receiver, and the current probe of the EMI receiver is respectively connected to the DC terminal and the three-phase terminal of the electric control;
[0045] For example Figure 6 As shown, the first fixing fixture is used to fix the magnetic ring and the current probe, and the first fixing fixture includes a current probe groove for fixing the current probe and a magnetic ring groove for fixing the magnetic ring.
[0046] Due to the cylindrical shape of the magnetic ring and the current probe, and their heavy mass, the clamp on the line can easily deform the cable and shake it, which may cause a slight change in the measurement result. The first fixing fixture uses insulating foam as the base and is hollowed out into a groove that is consistent with the lower quarter of the magnetic ring and the current probe. On the one hand, the first fixing fixture fixes the magnetic ring and the current probe, and on the other hand, isolates them at a certain distance so that the magnetic ring will not affect the measurement result.
[0047] It should be noted that the impedance of the magnetic ring, LISN, motor and any external filter can be easily measured using an impedance analyzer. Therefore, the external impedance Z of the DC end of the electronic control can be determined by measuring with an impedance analyzer. in And the external impedance Z at the three-phase end out , Z in =Equal to the impedance of the magnetic ring at the DC end plus the impedance of the LISN, Z out It is equal to the impedance of the magnetic ring at the three-phase end plus the impedance of the motor. Since the electronic control is a two-port device, its Z parameter cannot be measured directly.
[0048] For the Z parameter of the electric control, the present application also provides a specific calculation method: connect the two ends of the electric control respectively through a network analyzer to obtain the S parameter of the electric control; the electric control is equivalent to a two-port model, and the Z parameter is calculated according to the S parameter;
[0049] Z Parameters It can be calculated from the S parameters using the following formula:
[0050] Among them, S parameters (Scattering Parameters) are called scattering parameters, which are important parameters for describing the frequency domain characteristics of the transmission channel. They describe the relationship between the incident wave and the reflected wave and the transmission wave at the network port. For a two-port network, S parameters specifically include four parameters: S11, S21, S12 and S22, each of which has a specific meaning: S11 represents the reflection coefficient of port 1 (DC end of the electrical control) when port 2 (three-phase end of the electrical control) is matched, that is, when there is no reflection at port 2; S21 represents the forward transmission coefficient from port 1 to port 2 when port 2 is matched, that is, the gain; S12 represents the reverse transmission coefficient from port 2 to port 1 when port 1 is matched, also known as isolation; S22 represents the reflection coefficient of port 2 when port 1 is matched.
[0051] In one practicable manner, a network analyzer is connected to both ends of the electronic control, such as Figure 7 As shown, the present application also provides a fixture, through which the network analyzer is connected to the DC end and the three-phase end of the electric control respectively. More specifically, the aforementioned fixture includes a DC end fixture and a three-phase end fixture:
[0052] like Figure 8 As shown, the DC end fixture includes an L-shaped copper plate, the L-shaped copper plate includes a first straight side and a second straight side, the first straight side is welded with an N-type female flange, the N-type female flange is used to connect one end of the network analyzer, the second straight side includes two holes, the spacing between the two holes is consistent with the spacing of the busbars at the DC end of the electric control, and the two holes on the second straight side are used to connect two DC high-voltage wire harnesses at the DC end of the electric control;
[0053] like Fig. 9 As shown, the three-phase end fixture includes an I-shaped copper plate, to which an N-type female flange and three holes are welded. The N-type female flange is used to connect the other end of the network analyzer. The spacing of the three holes is consistent with the spacing of the busbars at the three-phase end of the electronic control. The three holes are used to connect the three AC high-voltage wire harnesses at the three-phase end of the electronic control.
[0054] In one feasible manner, in order to select a magnetic ring with a sufficiently large impedance, before the computing device puts the magnetic ring on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance, the computing device connects the two ends of the electric control respectively through a network analyzer to obtain the S parameters of the electric control; the electric control is equivalent to a two-port model, and the Z parameters are calculated based on the S parameters; the magnetic ring is selected based on the Z parameters, for example, a magnetic ring with an impedance at least two orders of magnitude larger than the Z impedance is selected, so that the impedance of the magnetic ring is much larger than the Z parameter, and there is no need to consider the Z parameter when calculating the first equivalent noise source, thereby achieving fast calculation and improving the problems of high complexity of model layout and long modeling and prediction cycle in the prior art.
[0055] Regarding step 321, since the present application uses a magnetic ring to set a large external impedance for the electric control, Z in >>Z 11 +Z 12 , Z out >>Z 21 +Z 22 , so Z in Formula 2 can be 11 +Z 12 Approximately zero, Z in Formula 3 21 +Z 22 Approximately zero, specifically, the mathematical expression of the aforementioned step 302 includes Formula 4: V Ni =-i cmi *Z in , and Formula 5: V No =-i cmo *Z out ; Among them, V Ni It is the first equivalent noise source of the DC end of the electronic control. cmi is the common mode current at the DC end of the electronic control, Z in is the external impedance of the DC terminal of the electronic control, V No It is the first equivalent noise source of the three-phase terminal of the electric control. cmo is the common mode current of the three-phase terminal of the electronic control and Z out is the external impedance of the three-phase terminal of the electronic control, Z in and Z out Much larger than the Z parameter.
[0056] It can be seen that the aforementioned Formula 4 and Formula 5 can be simplified based on the aforementioned Formula 2 and Formula 3. It can be seen that there is no need to consider the Z parameter. The first equivalent noise source can be quickly calculated based on the maximum external impedance and the equivalent common-mode current of the electronic control when the maximum external impedance is set.
[0057] After calculating and obtaining the first equivalent noise source in step 321, the present application also provides another embodiment of the common mode current prediction method before executing step 331, such as Fig.10 As shown, in this embodiment, the present application sets a very small external impedance at the DC end and the three-phase end of the electric control, so that the prediction of the common mode current at the DC end and the three-phase end is more accurate. Next, the present application will be described in detail with the computing device as the execution subject:
[0058] 322: After setting capacitors at the DC terminal and the three-phase terminal of the electric control of the electric drive system to obtain a minimum external impedance, obtain an equivalent common mode current of the electric drive system when the minimum external impedance is set;
[0059] 323: The electric control is equivalent to a two-port model to calculate the second equivalent noise source according to the Z parameter of the electric control of the electric drive system and the equivalent common mode current when the minimum external impedance is set;
[0060] 324: Correcting the first equivalent noise source using the second equivalent noise source, so that the common mode current when any external filter is set is predicted based on the corrected first equivalent noise source.
[0061] For step 322, the present application uses a second fixing fixture to set capacitors at the DC end and the three-phase end of the electric control of the electric drive system. The number of the second fixing fixtures is consistent with the number of cables at the DC end and the three-phase end of the electric control. That is to say, the two cables at the DC end of the electric control are each provided with a capacitor through two second fixing fixtures, and the three cables at the three-phase end of the electric control are each provided with a capacitor through three second fixing fixtures.
[0062] In one possible implementation, a 5uF capacitor can be selected, which can greatly reduce the impedance to ground between the cable and the ground in the 150kHz to 30MHz frequency band. For the electric drive system, the 150kHz to 30MHz frequency band involves electromagnetic compatibility (EMC) issues. The electric drive system generates electromagnetic radiation during operation. If these radiations exceed a certain limit, they may interfere with other radio equipment outside the vehicle (such as radio receivers, radars, etc.). The 150kHz to 30MHz frequency band includes several important radio communication frequency bands, such as shortwave communication, amateur radio, and some broadcast frequency bands. Electromagnetic radiation may also interfere with electronic equipment inside the car, affecting the normal operation and safety performance of the vehicle. For example, excessive electromagnetic radiation may interfere with the normal operation of key components such as on-board sensors and control systems. Therefore, the electromagnetic radiation characteristics of the automotive electric drive system in this frequency band need to be strictly controlled to reduce the adverse effects on external radio equipment and key components such as sensors, thereby improving the reliability and safety of the product.
[0063] For example, the second fixing tool is Fig.11 As shown, the second fixed fixture includes a plastic back plate as a base, an I-shaped copper plate is fixed to the upper end of the plastic back plate by screws, the thickness of the copper plate can be set to 1mm, the copper plate includes a hole with a diameter matching the cable diameter, so that the cable of the electric control can pass through the hole to connect with other devices; an L-shaped copper plate is fixed to the lower end of the plastic back plate by screws, so that the second fixed fixture can be placed upright; the capacitor is connected between the upper and lower copper plates by welding or drilling and welding. Further, the electric drive system of the second fixed fixture is installed as shown in FIG. Fig.12 shown.
[0064] For step 322, after setting the capacitor at the DC end and the three-phase end of the electric control of the electric drive system to obtain a minimum external impedance, for example Fig.13The computer (computing device) in the apparatus obtains the equivalent common-mode current of the electric drive system when the minimum external impedance is set through the EMI receiver, and the current probe of the EMI receiver is respectively connected to the DC terminal and the three-phase terminal of the electric control.
[0065] Regarding step 323, since the present application uses a magnetic ring to set a large external impedance for the electric control, Z in Z 21 +Z 22 , Z out Z 21 +Z 22 , so Z in Formula 2 can be in Approximately zero, Z in Formula 3 out Approximately zero, specifically, the mathematical expression of the aforementioned step 323 includes Formula 6: V Ni =-i cmi *(Z 11 +Z 12 ), and Formula 7: V No =-i cmo *(Z 21 +Z 22 ), where V Ni is the equivalent noise source at the DC end of the electronic control, i cmi is the common mode current at the DC end of the electronic control, Z 11 is the input impedance of the DC terminal of the electronic control, Z 12 is the transfer impedance from the DC end to the three-phase end of the electronic control, V No is the equivalent noise source of the three-phase terminal of the electronic control, i cmo is the common mode current of the three-phase terminal of the electronic control, Z 21 is the transfer impedance from the three-phase end to the DC end of the electronic control and Z 22 is the input impedance of the three-phase terminal of the electronic control, Z in and Z out It is much smaller than the Z parameter. It can be seen that the above formulas 6 and 7 can be simplified based on the above formulas 2 and 3. It can be seen that there is no need to consider the external impedance. The second equivalent noise source can be quickly calculated based on the Z parameter and the equivalent common-mode current of the electronic control when the external impedance is set to a very small value.
[0066] With respect to step 324, after calculating the second equivalent noise source, the computing device uses the second equivalent noise source to correct the first equivalent noise source, so that in step 331, the corrected first equivalent noise source is used to predict the common-mode current when any external filter is set, and the correction method includes averaging and weighted summing.
[0067] It should be noted that the settings of maximum and minimum external impedance can play a role in complementing each other's predictions. When one setting has a large deviation in the prediction of certain narrow frequency bands, another method can be used. When the deviation between the two settings is not large, the two predicted equivalent noise sources can be averaged, which is often closer to the true value. Based on this, the present application also provides a specific implementable method, and the aforementioned step of correcting the first equivalent noise source using the second equivalent noise source includes: determining whether the difference between the first equivalent noise source and the second equivalent noise source is greater than a threshold; if the difference is greater than the threshold, the equivalent noise source close to the resonance point in the first equivalent noise source and the second equivalent noise source is used as the corrected first equivalent noise source; if the difference is less than or equal to the threshold, the average value of the first equivalent noise source and the second equivalent noise source is calculated to obtain the corrected first equivalent noise source.
[0068] In addition, the present application also provides a detection system, which includes: a first fixing tool for fixing the magnetic ring to the DC end and the three-phase end of the electric control of the electric drive system; an EMI receiver for detecting the equivalent common-mode current of the electric drive system when the maximum external impedance is set; a computing device is connected to the EMI receiver, and the computing device is used to execute the common-mode current prediction method of any of the aforementioned embodiments or implementation methods.
[0069] In one possible implementation, the aforementioned detection system also includes a fixture and a network analyzer, the fixture is used to connect the network analyzer to the DC end and the three-phase end of the electric control respectively, the network analyzer is used to obtain the S parameters of the electric control, the computing device is connected to the network analyzer, and the computing device is also used to: connect the two ends of the electric control respectively through the network analyzer to obtain the S parameters of the electric control; equate the electric control to a two-port model, and calculate the Z parameters based on the S parameters; select the magnetic ring according to the Z parameters so that the impedance of the magnetic ring is much larger than the Z parameters.
[0070] In one embodiment, the prediction system also includes a second fixed tool, which is used to set capacitors at the DC end and three-phase end of the electric control of the electric drive system to obtain a minimum external impedance. The computing device is also used to: after setting the capacitors at the DC end and three-phase end of the electric control of the electric drive system to obtain the minimum external impedance, obtain the equivalent common-mode current of the electric drive system when the minimum external impedance is set; equate the electric control to a two-port model to calculate the second equivalent noise source based on the Z parameter of the electric control of the electric drive system and the equivalent common-mode current when the minimum external impedance is set; use the second equivalent noise source to correct the first equivalent noise source, and predict the common-mode current when any external filter is set based on the corrected first equivalent noise source.
[0071] The present application also provides a computer device. The embodiment of the present application can divide the functional modules of the device according to the above method example. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic, which is only a logical function division, and there may be other division methods in actual implementation. Specifically, the computer device includes: an acquisition unit, which is used to obtain the equivalent common-mode current of the electric drive system when the maximum external impedance is set after the magnetic ring is placed on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance; a detection unit, which is used to equalize the electric control to a two-port model, so as to calculate the first equivalent noise source according to the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set; a prediction unit, which is used to predict the common-mode current when any external filter is set according to the first equivalent noise source when the magnetic ring has been removed and any external filter is set in the electric drive system.
[0072] In one possible implementation, the detection unit is also used for: before putting the magnetic ring on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance, connecting the two ends of the electric control respectively through a network analyzer to obtain the S parameters of the electric control; equating the electric control to a two-port model, and calculating the Z parameters based on the S parameters; selecting the magnetic ring based on the Z parameters so that the impedance of the magnetic ring is much larger than the Z parameters.
[0073] In combination with the first aspect, in a second possible implementation of the first aspect, the electric control is equivalent to a two-port model, so as to calculate a mathematical expression of the first equivalent noise source according to the maximum external impedance and the equivalent common mode current of the electric control when the maximum external impedance is set, including: V Ni =-i cmi *Z in , V No =-i cmo *Z out ; Among them, V Ni It is the first equivalent noise source of the DC end of the electronic control. cmi is the common mode current at the DC end of the electronic control, Z in is the external impedance of the DC terminal of the electronic control, V No It is the first equivalent noise source of the three-phase terminal of the electric control. cmo is the common mode current of the three-phase terminal of the electronic control and Z out is the external impedance of the three-phase terminal of the electronic control, Z in and Z out Much larger than the Z parameter.
[0074] In combination with the first aspect, in a third possible implementation manner of the first aspect, the detection unit is further used for: before predicting the common-mode current when setting any external filter based on the first equivalent noise source, after setting the capacitor at the DC end and the three-phase end of the electric control of the electric drive system to obtain the minimum external impedance, obtaining the equivalent common-mode current of the electric drive system when the minimum external impedance is set; equating the electric control to a two-port model to calculate the second equivalent noise source based on the Z parameter of the electric control of the electric drive system and the equivalent common-mode current when the minimum external impedance is set; and using the second equivalent noise source to correct the first equivalent noise source, so that the common-mode current when setting any external filter is then predicted based on the corrected first equivalent noise source.
[0075] In combination with the third possible implementation of the first aspect, in a fourth possible implementation of the first aspect, the electric control is equivalent to a two-port model, and a mathematical expression of the second equivalent noise source is calculated according to the Z parameter of the electric control of the electric drive system and the equivalent common mode current when the minimum external impedance is set, including: V Ni =-i cmi *(Z 11 +Z 12 ), V No =-i cmo *(Z 21 +Z 22 ), where V Ni is the equivalent noise source at the DC end of the electronic control, i cmi is the common mode current at the DC end of the electronic control, Z 11 is the input impedance of the DC terminal of the electronic control, Z 12 is the transfer impedance from the DC end to the three-phase end of the electronic control, V No is the equivalent noise source of the three-phase terminal of the electronic control, i cmo is the common mode current of the three-phase terminal of the electronic control, Z 21 is the transfer impedance from the three-phase end to the DC end of the electronic control and Z 22 is the input impedance of the three-phase terminal of the electronic control, Z in and Z out Much smaller than the Z parameter.
[0076] In combination with the third possible implementation method of the first aspect, in a fifth possible implementation method of the first aspect, the detection unit is specifically used to: determine whether the difference between the first equivalent noise source and the second equivalent noise source is greater than a threshold; if the difference is greater than the threshold, then use the equivalent noise source close to the resonance point between the first equivalent noise source and the second equivalent noise source as a corrected first equivalent noise source; if the difference is less than or equal to the threshold, then calculate the average value of the first equivalent noise source and the second equivalent noise source to obtain the corrected first equivalent noise source.
[0077] The present application also provides a computing device, which may include: a processor and a memory. The processor and the memory are connected via a bus. The processor is used to execute multiple instructions; the memory is used to store multiple instructions, which are suitable for the processor to load and execute the common-mode current prediction method in the above embodiment.
[0078] The processor may be an electronic control unit (ECU), a central processing unit (CPU), a general processor, a coprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of 5SP and a microprocessor, etc. In this embodiment, the processor may be a single-chip microcomputer, and various control functions may be implemented by programming the single-chip microcomputer. The processor has the advantages of powerful computing power and fast processing. Specifically, the processor is used to execute the function of the acquisition unit, which is used to obtain the equivalent common-mode current of the electric drive system when the maximum external impedance is set after the magnetic ring is put on the DC end and the three-phase end of the electric control of the electric drive system to obtain the maximum external impedance; it is also used to execute the function of the detection unit, which is used to equate the electric control to a two-port model to calculate the first equivalent noise source based on the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set; it is also used to execute the function of the prediction unit, which is used to predict the common-mode current when any external filter is set according to the first equivalent noise source when the magnetic ring has been removed and any external filter is set in the electric drive system.
[0079] In one embodiment, the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a plurality of instructions, which are suitable for being loaded by a processor and executing the method in any of the foregoing embodiments. The processor is used to execute the plurality of instructions; the memory is used to store the plurality of instructions, which are loaded by the processor and execute the common-mode current prediction method in the foregoing embodiments.
[0080] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0081] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.
Claims
1. A common mode current prediction method, characterized in that: include: After the magnetic ring is placed on the DC terminal and the three-phase terminal of the electric control of the electric drive system to obtain a maximum external impedance, an equivalent common mode current of the electric drive system when the maximum external impedance is set is obtained; The electric control is equivalent to a two-port model, so as to calculate a first equivalent noise source according to the maximum external impedance and an equivalent common mode current of the electric control when the maximum external impedance is set; When the magnetic ring has been removed and any external filter is provided in the electric drive system, the common mode current when any external filter is provided is predicted according to the first equivalent noise source.
2. The prediction method according to claim 1, characterized in that: Before putting the magnetic ring on the DC end and three-phase end of the electric control of the electric drive system to obtain the maximum external impedance, it also includes: Connecting two ends of the electric controller respectively through a network analyzer to obtain S parameters of the electric controller; Equivalently converting the electric control into a two-port model, and calculating the Z parameter according to the S parameter; A magnetic ring is selected according to the Z parameter so that the impedance of the magnetic ring is much greater than the Z parameter.
3. The prediction method according to claim 1, characterized in that: The step of converting the electric control into a two-port model to calculate a mathematical expression of a first equivalent noise source according to the maximum external impedance and the equivalent common-mode current of the electric control when the maximum external impedance is set includes: V Ni =-i cmi *Z in ,V No =-i cmo *Z out ; Among them, V Ni It is the first equivalent noise source of the DC end of the electronic control. cmi is the common mode current at the DC end of the electronic control, Z in is the external impedance of the DC terminal of the electronic control, V No It is the first equivalent noise source of the three-phase terminal of the electric control. cmo is the common mode current of the three-phase terminal of the electronic control and Z out is the external impedance of the three-phase terminal of the electronic control, Z in and Z out Much larger than the Z parameter.
4. The prediction method according to claim 1, characterized in that: Before predicting the common mode current when any external filter is set according to the first equivalent noise source, the method further includes: After setting capacitors at the DC end and the three-phase end of the electric control of the electric drive system to obtain a minimum external impedance, obtaining an equivalent common-mode current of the electric drive system when the minimum external impedance is set; The electric control is equivalent to a two-port model, so as to calculate a second equivalent noise source according to a Z parameter of the electric control of the electric drive system and an equivalent common mode current when the minimum external impedance is set; The first equivalent noise source is corrected by using the second equivalent noise source, so that the common mode current when any external filter is set can be predicted based on the corrected first equivalent noise source.
5. The prediction method according to claim 4, characterized in that: The step of converting the electric control into a two-port model to calculate a mathematical expression of a second equivalent noise source according to the Z parameter of the electric control of the electric drive system and the equivalent common mode current when the minimum external impedance is set includes: V Ni =-i cmi *(Z 11 +Z 12 ),V No =-i cmo *(Z 21 +Z 22 ); Among them, V Ni is the equivalent noise source at the DC end of the electronic control, i cmi is the common mode current at the DC end of the electronic control, Z 11 is the input impedance of the DC terminal of the electronic control, Z 12 is the transfer impedance from the DC end to the three-phase end of the electronic control, V No is the equivalent noise source of the three-phase terminal of the electronic control, i cmo is the common mode current of the three-phase terminal of the electronic control, Z 21 is the transfer impedance from the three-phase end to the DC end of the electronic control and Z 22 is the input impedance of the three-phase terminal of the electronic control, Z in and Z out Much smaller than the Z parameter.
6. The prediction method according to claim 4, characterized in that: The step of correcting the first equivalent noise source by using the second equivalent noise source comprises: Determining whether a difference between the first equivalent noise source and the second equivalent noise source is greater than a threshold; If the difference is greater than a threshold, the equivalent noise source between the first equivalent noise source and the second equivalent noise source that is close to the resonance point is used as a corrected first equivalent noise source; If the difference is less than or equal to a threshold, an average value of the first equivalent noise source and the second equivalent noise source is calculated to obtain a corrected first equivalent noise source.
7. A detection system, characterized in that: The detection system comprises: A first fixing fixture is used to fix the magnetic ring to the DC end and the three-phase end of the electric control of the electric drive system; An EMI receiver, used for detecting an equivalent common mode current of the electric drive system when the maximum external impedance is set; The computing device is connected to the EMI receiver, and the computing device is used to execute the common-mode current prediction method according to any one of claims 1 to 6.
8. A computing device, characterized in that The computing device comprises: An acquisition unit is used to obtain an equivalent common mode current of the electric drive system when the maximum external impedance is set after the magnetic ring is put on the DC terminal and the three-phase terminal of the electric control of the electric drive system to obtain the maximum external impedance; A detection unit, used for converting the electric control into a two-port model, so as to calculate a first equivalent noise source according to the maximum external impedance and an equivalent common mode current of the electric control when the maximum external impedance is set; A prediction unit is used to predict the common mode current when any external filter is set according to the first equivalent noise source when the magnetic ring has been removed and the electric drive system is provided with any external filter.
9. A computing device, characterized in that The computer device includes a processor and a memory, which are connected via a bus; the processor is used to execute multiple instructions; the memory is used to store the multiple instructions, and the instructions are suitable for being loaded by the processor and executing the common-mode current prediction method described in any one of claims 1 to 6.
10. A computer-readable storage medium, characterized in that a plurality of instructions are stored in the computer-readable storage medium, and the instructions are suitable for being loaded by a processor and executing the common-mode current prediction method according to any one of claims 1 to 6.