Methods for analyzing the interference sources of conducted electromagnetic interference interactions in multi-electric aircraft systems

Abstract

This invention discloses a method for analyzing the interference sources of conducted electromagnetic interference (EMI) interactions in multi-electric aircraft systems, belonging to the field of EMI technology for multi-electric aircraft systems. This invention addresses the problem that existing multi-electric aircraft systems require EMI noise analysis of interference sources under physical conditions, and struggle to effectively suppress excessive EMI noise. The multi-electric aircraft system includes a DC / DC converter branch, a motor and driver branch, and a DC / AC inverter branch. The method considers the IGBTs in the DC / DC converter, motor driver, and DC / AC inverter as interference sources generating high-frequency interference. Equivalent high-frequency inductance, parasitic inductance, and parasitic capacitance of the components are applied to obtain high-frequency equivalent models for each branch. Operating conditions are then classified, and high-frequency equivalent circuits are obtained based on equivalent impedance. Finally, based on the current expression of the interference source, the interference path of the interference source through the DC bus to sensitive equipment in the multi-electric aircraft system is determined. This invention is used for the analysis and determination of interference sources.

Description

Technical Field

[0001] This invention relates to a method for analyzing interference sources in the interaction of conducted electromagnetic interference in multi-electric aircraft systems, and belongs to the field of electromagnetic interference technology for multi-electric aircraft systems. Background Technology

[0002] More-electric aircraft systems primarily employ power electronic conversion devices, such as rectifiers, inverters, and choppers, to achieve voltage level conversion. With continuous breakthroughs in power electronics technology, higher switching frequencies and power densities, as well as lower power consumption, are the main research goals for future power electronic conversion devices.

[0003] While power electronics technology has developed rapidly, its electromagnetic interference (EMI) problem has become increasingly prominent. On the one hand, the switching frequency, components, PCB design, and routing of high-power-density power electronic converters differ significantly from traditional power supplies. On the other hand, with the rapid development and widespread application of power electronic converters, their miniaturization and high-frequency trends have exacerbated EMI problems. Therefore, the lack of targeted EMI strategies has become a major bottleneck restricting the development of power electronic converters. The urgency and inevitability of this problem make EMI characteristic modeling of power electronic converters a highly significant task.

[0004] Airborne equipment is typically weight-sensitive, and power electronic converters are small in size, making it difficult to use traditional bulky EMI filters. Therefore, conducted EMI noise can easily be transmitted through cables, affecting sensitive equipment in the system. Currently, EMI noise in more-electric aircraft systems can only be tested after product finalization or prototype manufacturing. If the EMI noise exceeds the standard, noise suppression solutions can only be designed without changing the existing product topology, often proving inefficient and sometimes requiring a complete redesign of the product topology. Therefore, studying the EMI interaction mechanism of power electronic converters in more-electric aircraft systems has significant engineering implications.

[0005] For multi-electric and all-electric aircraft, the number of onboard electrical devices has increased significantly. Under conditions of multi-level power grid interconnection and dynamic loading of diverse electrical equipment, electromagnetic interference exhibits characteristics of multiple interference sources and multiple coupling paths, posing higher requirements for aircraft electromagnetic compatibility analysis. Currently, multi-electric system-level electromagnetic compatibility analysis methods still face significant challenges under conditions of multiple interference sources superimposed and multiple coupling paths mixed. For example, conducted emissions from power electronic devices and integrated motor systems based on circuit methods face difficulties in extracting parasitic parameters, and the models are complex and not very accurate. Summary of the Invention

[0006] To address the problem that existing multi-electric aircraft systems require EMI noise analysis of interference sources under physical conditions, and that it is difficult to effectively suppress excessive EMI noise, this invention provides an interference source analysis method for conducted electromagnetic interference interaction in multi-electric aircraft systems.

[0007] The present invention provides a method for analyzing the interference sources of conducted electromagnetic interference interactions in multi-electric aircraft systems, comprising:

[0008] The multi-electric aircraft system includes a DC / DC converter branch, a motor and driver branch, and a DC / AC inverter branch.

[0009] In the DC / DC converter branch, the input terminal of the DC / DC converter is connected to the 270V DC bus through circuit breaker one, and the output terminal of the DC / DC converter is connected to the DC load.

[0010] In the motor and driver branch, the input terminal of the motor driver is connected to the 270V DC bus through circuit breaker two, and the output terminal of the motor driver is connected to the permanent magnet synchronous motor.

[0011] In the DC / AC inverter branch, the input terminal of the DC / AC inverter is connected to the 270V DC bus through circuit breaker three, and the output terminal of the DC / AC inverter is connected to the AC load.

[0012] The IGBTs in the DC / DC converter, motor driver, and DC / AC inverter are respectively taken as interference sources that generate high-frequency interference. The components of the three branches are equivalent to high-frequency inductance, parasitic inductance, and parasitic capacitance, respectively, to obtain high-frequency equivalent models of the DC / DC converter branch, the motor and driver branch, and the DC / AC inverter branch.

[0013] After classifying the DC / DC converter branch, motor and driver branch, and DC / AC inverter branch according to grid-connected operation and grid-connected shutdown, the corresponding high-frequency equivalent model is used to obtain the high-frequency equivalent circuit through equivalent impedance transformation. Based on the high-frequency equivalent circuit, the current expression for the interference source is obtained, and the interference path of the interference source to the sensitive equipment in the multi-electric aircraft system through the DC bus is determined.

[0014] According to the interference source analysis method for conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, the DC / DC converter branch includes a half-bridge circuit, a transformer, a rectifier, and a filter.

[0015] The equivalent interference source voltage V generated by the IGBT in the half-bridge circuit CM1 Inductance L of the input wires of the DC / DC converter DCcab1 and parasitic capacitance C DCcab1 Inductance L of the output wire of the DC / DC converterDCcab11 The high-frequency parasitic capacitance C of the emitter of the IGBT in the half-bridge circuit. E1 and collector high-frequency parasitic capacitance C C1 The capacitance C at the midpoint of the half-bridge arm to ground in the half-bridge circuit O1 Parasitic capacitance between turns and between windings of transformer 1; capacitance C of rectifier diodes to ground in the rectifier. D1 The parasitic capacitance of the inductor and the parasitic inductance of the capacitor in the filter are used to construct a high-frequency equivalent model of the DC / DC converter branch.

[0016] According to the interference source analysis method of conducted electromagnetic interference interaction of the multi-electric aircraft system of the present invention, the motor and driver branch includes a permanent magnet synchronous motor and a motor driver, and the motor driver is implemented by a three-phase half-bridge circuit.

[0017] The equivalent interference source voltage V generated by the IGBT in the three-phase half-bridge circuit CM2 Inductance L of the motor driver input wire DCcab2 and parasitic capacitance C DCcab2 The high-frequency equivalent impedance Z of a permanent magnet synchronous motor PMSM In a three-phase half-bridge circuit, the high-frequency parasitic capacitance C of the emitter of the IGBT E2 and collector high-frequency parasitic capacitance C C2 The capacitance to ground at the midpoint of the three-phase half-bridge circuit arm is C. O2 The inductance L of the wire between the motor driver and the permanent magnet synchronous motor ACcab2 Construct a high-frequency equivalent model of the motor and driver branches.

[0018] According to the interference source analysis method of conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, the DC / AC inverter branch includes a single-phase full-bridge circuit, transformer II, and an output filter.

[0019] The equivalent interference source voltage V generated by the IGBT in a single-phase full-bridge circuit CM3 Inductance L of the input wires of the DC / AC inverter DCcab3 and parasitic capacitance C DCcab3 Inductance L of the output wire ACcab3 In a single-phase full-bridge circuit, the high-frequency parasitic capacitance C of the IGBT's emitter is... E3 and collector high-frequency parasitic capacitance C C3 The capacitance to ground at the midpoint of the single-phase full-bridge circuit arm is C. O3 A high-frequency equivalent model of the DC / AC inverter branch is constructed by considering the inter-turn parasitic capacitance and inter-winding parasitic capacitance of transformer 2, the parasitic capacitance of the inductor in the output filter, and the parasitic inductance of the capacitor.

[0020] According to the interference source analysis method of conducted electromagnetic interference interaction of the multi-electric aircraft system of the present invention, the high-frequency parameters in the high-frequency equivalent model of each branch are determined by measurement and fitting method.

[0021] Based on the high-frequency equivalent circuit, the superposition theorem is used to analyze the interactive electromagnetic interference of the aircraft system. The high-frequency parameters in the calculated high-frequency equivalent model are used to predict the interference path of interactive electromagnetic interference to sensitive equipment in the multi-electric aircraft system.

[0022] According to the interference source analysis method for conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, the specific calculation method for high-frequency parameters in the high-frequency equivalent model of each branch is as follows:

[0023] The impedance parameters of the high-frequency equivalent model are derived to obtain the impedance relationship containing unknown high-frequency parameters. The actual impedance characteristic curve of the test equipment is obtained by using an impedance analyzer to obtain the actual impedance characteristic data. Then, the actual impedance characteristic curve is fitted with the impedance relationship containing unknown high-frequency parameters to calculate the value of the corresponding high-frequency parameter in each high-frequency equivalent model.

[0024] According to the interference source analysis method for conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, if operating condition 1 is selected as the DC / DC converter branch being connected to the grid and the motor and driver branch and the DC / AC inverter branch being connected to the grid and shut down, then the IGBT bridge arms in the motor driver and DC / AC inverter form a new interference current conduction path to the DC / DC converter, including the IGBT bridge arm upper transistor to ground capacitance 3C of the three-phase half-bridge circuit and the single-phase full-bridge circuit. C2 and 2C C3 3C IGBT bridge arm lower transistor to ground capacitance E2 and 2C E3 Inductance of the conductor L DCcab2 / 2 and L DCcab3 / 2; then the impedance Z of the new interference current conduction path DC2 ,3 is:

[0025]

[0026] In the formula Z DCLcab3 For inductor L DCcab3 The equivalent impedance, Z DCLcab2 For inductor L DCcab2 Equivalent impedance; Z BUS2 and Z BUS3 As an intermediate variable:

[0027] Z BUS2 =3Z C2 +3Z E2 +2Z DCCcab2 ,

[0028] ZBUS3 =2Z C3 +2Z E3 +2Z DCCcab3 ,

[0029] In the formula Z C2 For collector high-frequency parasitic capacitance C C2 The equivalent impedance, Z E2 For the ultra-high frequency parasitic capacitance C E2 The equivalent impedance, Z DCCcab2 Parasitic capacitance C DCcab2 Equivalent impedance; Z C3 For collector high-frequency parasitic capacitance C C3 The equivalent impedance, Z E3 For the ultra-high frequency parasitic capacitance C E3 The equivalent impedance, Z DCCcab3 parasitic capacitance C DCcab3 The equivalent impedance;

[0030] Then the common-mode current I under operating condition 1 CM工况1 for:

[0031]

[0032] In the formula Z DCload Z is the DC load impedance to ground. DCcab11 For inductor L DCcab11 The equivalent impedance, Z DCfilt1 For the filter inductor L in the DC / DC converter DCfilt1 The equivalent impedance, Z D1 Z represents the impedance of the rectifier diode to ground in a DC / DC converter. c1 Z is the equivalent impedance of the inter-turn parasitic capacitance of transformer one. T1 Z is the equivalent impedance of the parasitic inter-winding capacitance of transformer one. O1 C is the capacitance to ground at the midpoint of the IGBT bridge arm in a half-bridge circuit. O1 The equivalent impedance, Z GRID Z is the common-mode impedance of the LISN. DCLcab1 For the inductance L of the wire DCLcab1 The equivalent impedance, Z DCCcab1 parasitic capacitance C DCcab1 The equivalent impedance;

[0033] Z IGBT1 The equivalent impedance of the IGBT in the half-bridge circuit:

[0034] Z IGBT1 =Z C1 +Z E1 ,

[0035] In the formula Z C1 For collector high-frequency parasitic capacitance CC1 The equivalent impedance, Z E1 For the ultra-high frequency parasitic capacitance C E1 The equivalent impedance.

[0036] According to the interference source analysis method of conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, based on the common-mode current I under operating condition 1 CM工况1 Analysis of the interference path yielded the following results:

[0037] In the low-frequency range, the frequency f is small, and due to L DCcab2 / 2、L DCcab3 / 2、C E2 C E3 C C2 and C C3 The values ​​are in the μH and pF ranges, Z DC2,3 Performance is greater than Z GRID Large inductive impedance; due to Z DC2,3 With Z GRID Because they are connected in parallel, the new interference current conduction path will not have a significant impact on the conducted electromagnetic interference of the DC / DC converter;

[0038] As the frequency increases, when Z DC2,3 When the current approaches 25Ω, the new interference current conduction path will have a significant impact on the conducted electromagnetic interference of the DC / DC converter;

[0039] Affected by transformer one, Z c1 +Z T1 For Z DCload Large values ​​indicate that the DC / DC converter is affected by the DC load's impedance to ground, Z. DCload The impact is relatively small.

[0040] According to the interference source analysis method of conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, operating condition 2 is selected as the DC / DC converter branch, motor and driver branch, and DC / AC inverter branch all connected to the grid; the common-mode current generated on the DC side of the DC / DC converter in the three branches is calculated respectively, and the total common-mode current I” in operating condition 2 is obtained by applying the superposition theorem. CM :

[0041] I” CM =I” CM1 +I” CM2 +I” CM3 (3)

[0042] In the formula I” CM1 I” represents the common-mode current generated on the DC side of the DC / DC converter branch. CM2 I” represents the common-mode current generated by the motor and driver branches on the DC side of the DC / DC converter. CM3This refers to the common-mode current generated by the DC / AC inverter branch on the DC side of the DC / DC converter.

[0043] Calculate the equivalent impedance of each of the three branches:

[0044]

[0045] In the formula, Z1 is the equivalent impedance of the DC / DC converter branch;

[0046] Z2 is the equivalent impedance of the motor and driver branch, Z ACcab2 For the inductance L of the wire ACcab2 The equivalent impedance, Z O2 C is the capacitance to ground at the midpoint of the IGBT bridge arm in a three-phase half-bridge circuit. O2 The equivalent impedance, Z DCLcab2 For inductor L DCLcab2 The equivalent impedance, Z DCCcab2 parasitic capacitance C DCcab2 The equivalent impedance;

[0047] Z IGBT2 The equivalent impedance of the IGBT in a three-phase half-bridge circuit:

[0048] Z IGBT2 =Z C2 +Z E2 ,

[0049] In the formula Z C2 For collector high-frequency parasitic capacitance C C2 The equivalent impedance, Z E2 For the ultra-high frequency parasitic capacitance C E2 The equivalent impedance;

[0050] Z3 is the equivalent impedance of the DC / AC inverter branch, Z AC3 Z is the AC load impedance to ground. ACcab3 For inductor L ACcab3 The equivalent impedance, Z ACfilt3 Z is the output filter impedance to ground. c3 Z is the equivalent impedance of the inter-turn parasitic capacitance of transformer two. T3 Z is the equivalent impedance of the parasitic inter-winding capacitance of transformer two. O3 The capacitance to ground at the midpoint of the IGBT bridge arm in a single-phase full-bridge circuit is C. O3 The equivalent impedance, Z DCLcab3 For inductor L DCcab3 The equivalent impedance, Z DCCcab3 parasitic capacitance C DCcab3 The equivalent impedance;

[0051] Z IGBT3 The equivalent impedance of the IGBT in a single-phase full-bridge circuit:

[0052] Z IGBT3 =Z C3 +Z E3 ,

[0053] In the formula Z C3 For collector high-frequency parasitic capacitance C C3 The equivalent impedance, Z E3 For the ultra-high frequency parasitic capacitance C E3 The equivalent impedance;

[0054] but:

[0055]

[0056]

[0057]

[0058] According to the interference source analysis method of conducted electromagnetic interference interaction in multi-electric aircraft systems of the present invention, based on the common-mode current I” in operating condition 2 CM1 、I” CM2 and I" CM3 Analysis of interference paths in DC / DC converters:

[0059] 1) Analyze the equivalent interference source voltage V of the DC / DC converter. CM1 The resulting impact caused V CM2 and V CM3 The value is 0; the motor and drive branch and the DC / AC inverter branch introduce an additional C during grid-connected operation. O2 C O3 Equivalent impedance Z c3 +Z T3 and Z PMSM Z GRID The impedance is 25Ω. In the low-frequency range, the impedance of Z2 and Z3 is much greater than 25Ω. GRID The interference generated by the path is the main interference; as the frequency increases, when the parallel impedance of Z2 and Z3 approaches or falls below 25Ω, the interference from Z2 and Z3 to I... c " m It has a significant impact;

[0060] 2) Analyze the equivalent interference source voltage V CM2 The resulting impact caused V CM1 and V CM3 =0; Interference source V CM2 Generate a value of I on the DC side of the DC / DC converter. CM2 Interference from the source V can affect the DC / DC converter; similarly, interference from the source V... CM3Generate a value of I on the DC side of the DC / DC converter. CM3 Interference;

[0061] I” CM2 and I" CM3 The impact on the DC / DC converter will be determined by its magnitude:

[0062] If I" CM1 >I” CM2 >I” CM3 Or I” CM1 >I” CM3 >I” CM2 The interference generated by the DC / DC converter itself is the main interference.

[0063] If I" CM2 >I” CM3 >I” CM1 Or I” CM3 >I” CM2 >I” CM1 Then the interference source V CM2 and V CM3 The interference generated is greater than the interference generated by the DC / DC converter itself.

[0064] If I" CM2 >I” CM1 >I” CM3 Or I” CM3 >I” CM1 >I” CM2 Then the interference source V CM2 and V CM3 At least one of the generated interferences is greater than the interference generated by the DC / DC converter itself.

[0065] The beneficial effects of this invention are as follows: By analyzing and modeling the interaction mechanism of conducted electromagnetic interference in multi-electric aircraft systems, this invention identifies the main interference sources that cause interference to sensitive equipment, thereby enabling targeted technical means to suppress interference and achieve electromagnetic interference protection.

[0066] The modeling objects selected by the method of this invention are common equipment in multi-electric aircraft. The analysis process and modeling method are universal and easy to promote and use. The high-frequency equivalent model established by the method of this invention fully considers the influence of parasitic parameters such as input and output cables on the circuit, and the model is closer to the real system. The method of this invention is based on accurate high-frequency equivalent circuits, and the high-frequency parameters obtained by fitting are highly accurate. The analysis of electromagnetic interference interaction between equipment fully considers various common operating conditions of each device, adopts an analysis method based on the superposition principle, has a clear approach, and clarifies the mechanism of electromagnetic interference interaction between equipment.

[0067] The method of this invention can be applied to the field of conducted electromagnetic interference interaction analysis and suppression in multi-electric aircraft systems, and has broad application prospects and great promotional value. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the structure of the multi-electric aircraft system described in this invention; K1 to K3 in the diagram are three circuit breakers;

[0069] Figure 2 It is the high-frequency equivalent model of the DC / DC converter branch;

[0070] Figure 3 It corresponds Figure 2 High-frequency equivalent circuit; I in the figure CM1 This refers to the common-mode current of the DC / DC converter.

[0071] Figure 4 It is a high-frequency equivalent model of the motor and driver branch;

[0072] Figure 5 It corresponds Figure 4 High-frequency equivalent circuit; I in the figure CM2 This refers to the common-mode current of the motor and driver branch.

[0073] Figure 6 It is the high-frequency equivalent model of the DC / AC inverter branch;

[0074] Figure 7 It corresponds Figure 6 High-frequency equivalent circuit; I in the figure CM3 This refers to the common-mode current of the DC / AC inverter.

[0075] Figure 8 This is a simplified model of the multi-electric aircraft system described in this invention;

[0076] Figure 9 This is a simplified model of a multi-electric aircraft system under operating condition 1;

[0077] Figure 10 It corresponds Figure 9 The high-frequency equivalent circuit;

[0078] Figure 11 This is a simplified model of the multi-electric aircraft system in operating condition 2;

[0079] Figure 12 It corresponds Figure 11 Considering only the interference source V of the DC / DC converter CM1 The high-frequency equivalent circuit;

[0080] Figure 13 It corresponds Figure 11 Considering only the interference source V of the motor and motor driver CM2The high-frequency equivalent circuit;

[0081] Figure 14 It corresponds Figure 11 Considering only the interference source V of the DC / AC inverter CM3 The high-frequency equivalent circuit. Detailed Implementation

[0082] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0083] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0084] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0085] Specific Implementation Method 1: Combination Figure 1 As shown, this invention provides a method for analyzing the interference sources of conducted electromagnetic interference interactions in multi-electric aircraft systems, including:

[0086] The multi-electric aircraft system includes a DC / DC converter branch, a motor and driver branch, and a DC / AC inverter branch.

[0087] In the DC / DC converter branch, the input terminal of the DC / DC converter is connected to the 270V DC bus through circuit breaker one, and the output terminal of the DC / DC converter is connected to the DC load.

[0088] In the motor and driver branch, the input terminal of the motor driver is connected to the 270V DC bus through circuit breaker two, and the output terminal of the motor driver is connected to the permanent magnet synchronous motor.

[0089] In the DC / AC inverter branch, the input terminal of the DC / AC inverter is connected to the 270V DC bus through circuit breaker three, and the output terminal of the DC / AC inverter is connected to the AC load.

[0090] The IGBTs in the DC / DC converter, motor driver, and DC / AC inverter are respectively taken as interference sources that generate high-frequency interference. The components of the three branches are equivalent to high-frequency inductance, parasitic inductance, and parasitic capacitance, respectively, to obtain high-frequency equivalent models of the DC / DC converter branch, the motor and driver branch, and the DC / AC inverter branch.

[0091] After classifying the DC / DC converter branch, motor and driver branch, and DC / AC inverter branch according to grid-connected operation and grid-connected shutdown, the corresponding high-frequency equivalent model is used to obtain the high-frequency equivalent circuit through equivalent impedance transformation. Based on the high-frequency equivalent circuit, the current expression for the interference source is obtained, and the interference path of the interference source to the sensitive equipment in the multi-electric aircraft system through the DC bus is determined.

[0092] This embodiment analyzes and models the interaction mechanism of conducted electromagnetic interference in a multi-electric aircraft system. The inter-device electromagnetic interference mentioned in this embodiment refers to the electromagnetic interference that devices in the system exert on other sensitive devices through the DC bus under different operating conditions. Through in-depth analysis of the causes of interactive interference in multi-electric aircraft systems, electromagnetic interference protection methods for sensitive devices can be quickly designed.

[0093] In this embodiment, the high-frequency equivalent models of each device fully consider the impact of high-frequency parasitic effects on components based on the basic circuit, establishing a relatively accurate multi-device model of the multi-electric aircraft system and elucidating the mechanism of electromagnetic interaction interference between devices in the multi-electric aircraft system. First, the coupling path and coupling mechanism of conducted interference in the multi-electric system under the high-low voltage hybrid system are analyzed; the influence mechanism of parasitic parameters between the system ground loop and the equipment structure and interconnection system on conducted interference is analyzed; second, modeling methods are studied for system interference sources such as inverters, choppers and other power electronic conversion devices, integrated motor devices such as fuel pumps, and system interconnection cables, and conducted emission models of the above typical components are established respectively; finally, the above interference source and interconnection system models are integrated, and the system-level conducted interference simulation method is studied to obtain the distribution of conducted interference and electromagnetic radiation environment inside the system when typical devices are working.

[0094] Combination Figure 2 and Figure 3 As shown, the DC / DC converter branch includes a half-bridge circuit, transformer one, rectifier, and filter; transformer one not only transmits energy but also increases the common-mode impedance of the circuit and reduces electromagnetic interference.

[0095] The equivalent interference source voltage V generated by the IGBT in the half-bridge circuit CM1 Inductance L of the input wires of the DC / DC converter DCcab1 and parasitic capacitance C DCcab1 Inductance L of the output wire of the DC / DC converter DCcab11 The high-frequency parasitic capacitance C of the emitter of the IGBT in the half-bridge circuit. E1 and collector high-frequency parasitic capacitance C C1 The capacitance C at the midpoint of the half-bridge arm to ground in the half-bridge circuit O1 Parasitic capacitance between turns and between windings of transformer 1; capacitance C of rectifier diodes to ground in the rectifier. D1The parasitic capacitance of the inductor and the parasitic inductance of the capacitor in the filter are used to construct a high-frequency equivalent model of the DC / DC converter branch.

[0096] A DC / DC converter transforms the high-voltage DC power from the 270V DC bus into a low-voltage DC power of 28V for use in navigation lights, instrument panels, etc. Figure 2 As shown; due to the common-ground design of the multi-electric aircraft system, the converter needs to be designed in an isolated form to ensure equipment and personal safety. To prevent transformer bias and DC magnetic saturation, a half-bridge circuit topology is adopted. The secondary side of transformer one uses a center-tapped winding, which, after diode rectification, becomes a DC current with large ripples. After passing through an RC filter circuit, it becomes a smoother DC current to supply the load. To facilitate the analysis of interference current conduction paths and simplify the analysis process, [the following is omitted as it is not part of the diagram] Figure 2 The circuit shown is simplified; the IGBT is the main source of interference voltage, which is equivalent to V. CM1 Then you will get Figure 3 The high-frequency simplified equivalent circuit is shown.

[0097] Combination Figure 4 and Figure 5 As shown, the motor and driver branch includes a permanent magnet synchronous motor and a motor driver, with the motor driver implemented using a three-phase half-bridge circuit;

[0098] The equivalent interference source voltage V generated by the IGBT in the three-phase half-bridge circuit CM2 Inductance L of the motor driver input wire DCcab2 and parasitic capacitance C DCcab2 The high-frequency equivalent impedance Z of a permanent magnet synchronous motor PMSM In a three-phase half-bridge circuit, the high-frequency parasitic capacitance C of the emitter of the IGBT E2 and collector high-frequency parasitic capacitance C C2 The capacitance to ground at the midpoint of the three-phase half-bridge circuit arm is C. O2 The inductance L of the wire between the motor driver and the permanent magnet synchronous motor ACcab2 Construct a high-frequency equivalent model of the motor and driver branches.

[0099] Motors and drives convert the high-voltage DC power from the 270V DC bus into mechanical energy to power various mechanical loads, such as... Figure 4 As shown. The motor driver includes a bus capacitor, a three-phase inverter bridge, and a control circuit; the output side of the motor driver is connected to a permanent magnet synchronous motor, and information such as the motor speed is input to the driver to form a closed-loop control. Figure 4The high-frequency equivalent model of the motor and driver branch shown fully considers the impact of high-frequency parasitic parameters of key components on the circuit, such as the parasitic parameters of input and output cables, the parasitic capacitance of the IGBT collector and transmitter to the heat sink, the parasitic capacitance of the bridge arm midpoint to ground, and the parasitic capacitance and inductance of the permanent magnet synchronous motor. The model can accurately describe the actual circuit. To facilitate the analysis of interference current conduction paths and simplify the analysis process, [the following is omitted]. Figure 4 The circuit shown is simplified; the IGBT is the main source of interference voltage, which is equivalent to V. CM2 Then you will get Figure 5 The high-frequency equivalent circuit shown is shown.

[0100] Combination Figure 6 and Figure 7 As shown, the DC / AC inverter branch includes a single-phase full-bridge circuit, transformer II, and an output filter; transformer II not only transmits energy but also increases the common-mode impedance of the circuit and reduces electromagnetic interference.

[0101] The equivalent interference source voltage V generated by the IGBT in a single-phase full-bridge circuit CM3 Inductance L of the input wires of the DC / AC inverter DCcab3 and parasitic capacitance C DCcab3 Inductance L of the output wire ACcab3 In a single-phase full-bridge circuit, the high-frequency parasitic capacitance C of the IGBT's emitter is... E3 and collector high-frequency parasitic capacitance C C3 The capacitance to ground at the midpoint of the single-phase full-bridge circuit arm is C. O3 A high-frequency equivalent model of the DC / AC inverter branch is constructed by considering the inter-turn parasitic capacitance and inter-winding parasitic capacitance of transformer 2, the parasitic capacitance of the inductor in the output filter, and the parasitic inductance of the capacitor.

[0102] The equivalent interference source is obtained by equivalent processing of the switching devices that generate high-frequency interference in the equipment; all high-frequency equivalent models are established based on the high-frequency parameters of the connecting cables, capacitors, inductors and switching devices involved in each device.

[0103] A DC / AC inverter converts the high-voltage DC power on the 270V DC bus into 400Hz, 115V AC power, such as... Figure 6 As shown; due to the special design of the common ground of the multi-electric aircraft system, in order to ensure the safety of equipment and personnel, the converter needs to be designed in an isolated form. The transformer output is connected to an RC filter. After the high frequency components are filtered out by the RC filter circuit, it becomes a smoother 400Hz, 115V AC power to supply the load. Figure 6 The circuit fully considers the impact of high-frequency parasitic parameters of key components on the circuit, and can accurately describe the actual circuit. To facilitate the analysis of interference current conduction paths and simplify the analysis process, [the following is omitted]. Figure 6The circuit shown is simplified; the IGBT is the main source of interference voltage, which is equivalent to V. CM3 Then you will get Figure 7 The high-frequency equivalent circuit shown is shown.

[0104] Furthermore, the high-frequency parameters in the high-frequency equivalent model of each branch are determined by a method of measurement plus least squares fitting;

[0105] Based on the high-frequency equivalent circuit, the superposition theorem is used to analyze the interactive electromagnetic interference of the aircraft system. The high-frequency parameters in the calculated high-frequency equivalent model are used to predict the interference path of interactive electromagnetic interference to sensitive equipment in the multi-electric aircraft system.

[0106] The specific calculation methods for high-frequency parameters in the high-frequency equivalent model of each branch are as follows:

[0107] The impedance parameters of the high-frequency equivalent model are derived to obtain the impedance relationship containing unknown high-frequency parameters. The actual impedance characteristic curve of the test equipment is obtained by using an impedance analyzer to obtain the actual impedance characteristic data. Then, the actual impedance characteristic curve is fitted with the impedance relationship containing unknown high-frequency parameters to calculate the value of the corresponding high-frequency parameter in each high-frequency equivalent model.

[0108] A multi-electric aircraft system is a high-voltage DC power supply system containing multiple devices, and its structure is relatively complex. Therefore, it is necessary to select typical devices for electromagnetic interference interaction analysis. Figure 1 The diagram shows the equipment structure of a multi-electric aircraft system. Each piece of equipment in the diagram is then represented using a high-frequency equivalent circuit model, resulting in... Figure 8 The figure shows a simplified high-frequency model of a multi-electromechanical system, clearly depicting the connection relationships between various devices via high-frequency conducted interference paths. Figure 8 The high-frequency equivalent parameters contained in the interference path shown need to be obtained by means of actual measurement and fitting. Specifically, the impedance characteristic curve of the device is measured using an impedance analyzer, and then the high-frequency parasitic parameters in the model are fitted by the least squares method in combination with the established high-frequency equivalent model of the device.

[0109] Specific Implementation Examples: The operating conditions of multi-electric aircraft systems are complex, making it impossible to comprehensively list and study all conditions. To elucidate the mechanism, several typical operating conditions are selected to illustrate the electromagnetic interference interaction analysis method. Operating condition 1 involves the DC / DC converter operating with the grid connected, and the DC / AC inverter, motor, and its driver shut down with the grid connected. Operating condition 2 involves the three devices operating with the grid connected. The simplified high-frequency models are as follows: Figure 9 and Figure 10 As shown.

[0110] Specific Implementation Example 1: Combining Figures 8 to 10As shown, operating condition 1 is selected, with the DC / DC converter branch connected to the grid and the motor and driver branch and the DC / AC inverter branch connected to the grid and shut down. The influence of parasitic parameters on the electromagnetic interference conduction path under this condition is analyzed, and the following results can be obtained: Figure 9 The equivalent circuit shown; when the motor and driver branch and the DC / AC inverter are stopped, they will not cause interference to the outside world. However, since the equipment is connected to the 270V DC bus, the IGBT bridge arm contained in the equipment will form a new conduction path for the DC / DC converter.

[0111] The IGBT bridge arms in motor drivers and DC / AC inverters create new interference current conduction paths for the DC / DC converter, including the capacitance to ground of the upper IGBT bridge arm in three-phase half-bridge circuits and single-phase full-bridge circuits. C2 and 2C C3 3C IGBT bridge arm lower transistor to ground capacitance E2 and 2C E3 Inductance of the conductor L DCcab2 / 2 and L DCcab3 / 2; For ease of study, the newly added conduction paths are merged, and the impedance Z of the new interference current conduction path is... DC2,3 for:

[0112]

[0113] In the formula Z DCLcab3 For inductor L DCcab3 The equivalent impedance, Z DCLcab2 For inductor L DCcab2 Equivalent impedance; Z BUS2 and Z BUS3 As an intermediate variable:

[0114] Z BUS2 =3Z C2 +3Z E2 +2Z DCCcab2 ,

[0115] Z BUS3 =2Z C3 +2Z E3 +2Z DCCcab3 ,

[0116] In the formula Z C2 For collector high-frequency parasitic capacitance C C2 The equivalent impedance, Z E2 For the ultra-high frequency parasitic capacitance C E2 The equivalent impedance, Z DCCcab2 parasitic capacitance C DCcab2 Equivalent impedance; Z C3 For collector high-frequency parasitic capacitance C C3 The equivalent impedance, Z E3For the ultra-high frequency parasitic capacitance C E3 The equivalent impedance, Z DCCcab3 parasitic capacitance C DCcab3 The equivalent impedance;

[0117] Then the common-mode current I under operating condition 1 CM工况1 for:

[0118]

[0119] In the formula Z DCload Z is the DC load impedance to ground. DCcab11 For inductor L DCcab11 The equivalent impedance, Z DCfilt1 For the filter inductor L in the DC / DC converter DCfilt1 The equivalent impedance, Z D1 Z represents the impedance of the rectifier diode to ground in a DC / DC converter. c1 Z is the equivalent impedance of the inter-turn parasitic capacitance of transformer one. T1 Z is the equivalent impedance of the parasitic inter-winding capacitance of transformer one. O1 C is the capacitance to ground at the midpoint of the IGBT bridge arm in a half-bridge circuit. O1 The equivalent impedance, Z GRID Z is the common-mode impedance of the LISN. DCLcab1 For the inductance L of the wire DCLcab1 The equivalent impedance, Z DCCcab1 parasitic capacitance C DCcab1 The equivalent impedance;

[0120] Z IGBT1 The equivalent impedance of the IGBT in the half-bridge circuit:

[0121] Z IGBT1 =Z C1 +Z E1 ,

[0122] In the formula Z C1 For collector high-frequency parasitic capacitance C C1 The equivalent impedance, Z E1 For the ultra-high frequency parasitic capacitance C E1 The equivalent impedance.

[0123] In this embodiment, based on the common-mode current I of operating condition 1 CM工况1 Analysis of the interference path yielded the following results:

[0124] In the low-frequency range, the frequency f is small, combined with... Figure 2 , Figure 3 and Figure 9 Analysis revealed that L in the new conduction pathway DCcab2 / 2、L DCcab3 / 2、C E2 CE3 C C2 and C C3 The values ​​are in the μH and pF ranges, Z DC2,3 Performance is greater than Z GRID Large inductive impedance; due to Z DC2,3 With Z GRID Parallel connection, considering Z GRID With an impedance of only 25Ω, the new interference current conduction path will not have a significant impact on the conducted electromagnetic interference of the DC / DC converter.

[0125] As the frequency increases, when Z DC2,3 When the current approaches 25Ω, the new interference current conduction path will have a significant impact on the conducted electromagnetic interference of the DC / DC converter;

[0126] As the frequency continues to increase, at higher frequencies, due to the influence of transformer one, Z c1 +Z T1 For Z DCload Large values ​​indicate that the DC / DC converter is affected by the DC load's impedance to ground, Z. DCload The impact is relatively small.

[0127] By comparing and analyzing the relationship between the interference current in operating condition 1 and the interference current when the DC / DC converter is running independently, the effectiveness of the analysis of the electromagnetic interference interaction mechanism between devices can be verified.

[0128] Specific Implementation Example 2: Combining Figure 8 , Figures 11 to 14 As shown, operating condition 2 is selected where the DC / DC converter branch, motor and driver branch, and DC / AC inverter branch are all connected to the grid. The common-mode current generated on the DC side of the DC / DC converter for each of the three branches is calculated, and the total common-mode current I” for operating condition 2 is obtained by applying the superposition theorem. CM :

[0129] I” CM =I” CM1 +I” CM2 +I” CM3 (3)

[0130] In the formula I” CM1 I” represents the common-mode current generated on the DC side of the DC / DC converter branch. CM2 I” represents the common-mode current generated by the motor and driver branches on the DC side of the DC / DC converter. CM3 This refers to the common-mode current generated by the DC / AC inverter branch on the DC side of the DC / DC converter.

[0131] The equivalent circuit for operating condition 2 is more complex. We can simplify it for equipment without interference sources to obtain the total impedance of that equipment. We then calculate the equivalent impedance of each of the three branches:

[0132]

[0133] In the formula, Z1 is the equivalent impedance of the DC / DC converter branch;

[0134] Z2 is the equivalent impedance of the motor and driver branch, Z ACcab2 For the inductance L of the wire ACcab2 The equivalent impedance, Z O2 C is the capacitance to ground at the midpoint of the IGBT bridge arm in a three-phase half-bridge circuit. O2 The equivalent impedance, Z DCLcab2 For inductor L DCLcab2 The equivalent impedance, Z DCCcab2 parasitic capacitance C DCcab2 The equivalent impedance;

[0135] Z IGBT2 The equivalent impedance of the IGBT in a three-phase half-bridge circuit:

[0136] Z IGBT2 =Z C2 +Z E2 ,

[0137] In the formula Z C2 For collector high-frequency parasitic capacitance C C2 The equivalent impedance, Z E2 For the ultra-high frequency parasitic capacitance C E2 The equivalent impedance;

[0138] Z3 is the equivalent impedance of the DC / AC inverter branch, Z AC3 Z is the AC load impedance to ground. ACcab3 For inductor L ACcab3 The equivalent impedance, Z ACfilt3 Z is the output filter impedance to ground. c3 Z is the equivalent impedance of the inter-turn parasitic capacitance of transformer two. T3 Z is the equivalent impedance of the parasitic inter-winding capacitance of transformer two. O3 The capacitance to ground at the midpoint of the IGBT bridge arm in a single-phase full-bridge circuit is C. O3 The equivalent impedance, Z DCLcab3 For inductor L DCcab3 The equivalent impedance, Z DCCcab3 parasitic capacitance C DCcab3 The equivalent impedance;

[0139] Z IGBT3 The equivalent impedance of the IGBT in a single-phase full-bridge circuit:

[0140] Z IGBT3 =Z C3 +Z E3 ,

[0141] In the formula Z C3 For collector high-frequency parasitic capacitance C C3 The equivalent impedance, Z E3 For the ultra-high frequency parasitic capacitance C E3 The equivalent impedance;

[0142] but:

[0143]

[0144]

[0145]

[0146] In this embodiment, based on the common-mode current I” of operating condition 2 CM1 、I” CM2 and I" CM3 An analysis of the interference path of the DC / DC converter reveals that the impact of the DC / AC converter, motor, and driver operating in Condition 2 on the DC / DC converter is mainly reflected in the following two aspects:

[0147] 1) The conduction path of interference current in the DC / DC converter becomes more complex. Analysis of the equivalent interference source voltage V of the DC / DC converter... CM1 The resulting impact caused V CM2 and V CM3 =0, get Figure 12 The equivalent circuit shown; compare it with the circuit in operating condition 1. Figure 10 During operation, the motor and driver branch and the DC / AC inverter branch will introduce additional C during grid-connected operation. O2 C O3 Equivalent impedance Z c3 +Z T3 and Z PMSM Because of Z GRID The impedance is 25Ω. In the low-frequency range, the impedance of Z2 and Z3 is much greater than 25Ω. GRID The interference generated by the path itself is the main interference, while the influence of Z2 and Z3 is relatively small; as the frequency increases, when the parallel impedance of Z2 and Z3 approaches or falls below 25Ω, the influence of Z2 and Z3 on I... c " m It has a significant impact; because Z2 contains the equivalent impedance Z of the permanent magnet synchronous motor. PMSM Permanent magnet synchronous motors are complex interference systems, and therefore the interference situation is complex at high frequencies.

[0148] 2) Interference source V CM2 and V CM3 Interference current will be generated on the DC side of the DC / DC converter. Analyze the equivalent interference source voltage V. CM2The resulting impact caused V CM1 and V CM3 =0, get Figure 13 The equivalent circuit shown; by Figure 13 It can be seen that the equivalent interference source voltage V CM2 The affected area includes DC / DC converters and interference sources V. CM2 Generate a value of I on the DC side of the DC / DC converter. CM2 Interference from the source V can affect the DC / DC converter; similarly, interference from the source V... CM3 Generate a value of I on the DC side of the DC / DC converter. CM3 Interference;

[0149] I” CM2 and I" CM3 The impact on the DC / DC converter will be determined by its magnitude:

[0150] If I" CM1 >I” CM2 >I” CM3 Or I” CM1 >I” CM3 >I” CM2 The interference generated by the DC / DC converter itself is the main interference, and the interference source V CM2 and V CM3 The resulting interference will not significantly affect the DC / DC converter;

[0151] If I" CM2 >I” CM3 >I” CM1 Or I” CM3 >I” CM2 >I” CM1 Then the interference source V CM2 and V CM3 If the generated interference is greater than the interference generated by the DC / DC converter itself, then the interference source V CM2 and V CM3 The resulting interference will severely affect the DC / DC converter; the degree of impact depends on I". CM2 and I" CM3 Depends on size;

[0152] If I" CM2 >I” CM1 >I” CM3 Or I” CM3 >I” CM1 >I” CM2 Then the interference source V CM2 and V CM3 If at least one of the generated interferences is greater than the interference generated by the DC / DC converter itself, then the interference source V CM2 and VCM3 The resulting interference will affect the DC / DC converter, and the extent of the impact depends on I”. CM2 and I" CM3 Depends on size.

[0153] In summary, the electromagnetic interference interaction mechanism of operating condition 2 was analyzed from two aspects: interference conduction path and interference source. Compared with operating condition 1, the equipment operating in operating condition 2, in addition to still introducing new cable high-frequency parasitic parameters and IGBT high-frequency parasitic parameters forming the conduction path, will also introduce new interference sources. The impact of the newly introduced interference sources on the DC / DC converter will be different from that of I”. CM3 、I” CM1 and I" CM2 Size determined.

[0154] Therefore, it can be seen that the conduction path formed by the parasitic capacitance of the heat sink and the cable of the IGBT plays an important role in the electromagnetic interference interaction process. Based on this, methods such as floating the heat sink and using shielded cables can be adopted to reduce the degree of electromagnetic interference interaction.

[0155] When using the method of this invention for interference source analysis, each device can first be classified according to its off-grid, on-grid, running, and shutdown conditions. Based on the characteristics of different operating conditions, the high-frequency equivalent model of the multi-electric aircraft system is transformed to obtain the corresponding high-frequency equivalent circuit. Then, the superposition theorem is applied to analyze the interactive electromagnetic interference of the system. The calculated high-frequency parameter values ​​can be used to predict the impact of interactive interference on sensitive equipment.

[0156] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method of interference source analysis for multi-electric aircraft system conducted electromagnetic interference interaction, characterized by Comprising, The multi-electric aircraft system comprises a DC / DC converter branch, a motor and driver branch and a DC / AC inverter branch; In the DC / DC converter branch, the input end of the DC / DC converter is connected to the 270V DC bus through a circuit breaker one, and the output end of the DC / DC converter is connected to a DC load; In the motor and driver branch, the input end of the motor driver is connected to the 270V DC bus through a circuit breaker two, and the output end of the motor driver is connected to a permanent magnet synchronous motor; In the DC / AC inverter branch, the input end of the DC / AC inverter is connected to the 270V DC bus through a circuit breaker three, and the output end of the DC / AC inverter is connected to an AC load; IGBTs in the DC / DC converter, the motor driver and the DC / AC inverter are respectively taken as interference sources generating high-frequency interference, high-frequency inductance, parasitic inductance and parasitic capacitance of the components of the three branches are equivalent, and a DC / DC converter branch high-frequency equivalent model, a motor and driver branch high-frequency equivalent model and a DC / AC inverter branch high-frequency equivalent model are respectively obtained; After the DC / DC converter branch, the motor and driver branch and the DC / AC inverter branch are classified according to the running and shutdown of the network, the corresponding high-frequency equivalent model is used to obtain a high-frequency equivalent circuit through equivalent impedance transformation, a current expression for the interference source is obtained according to the high-frequency equivalent circuit, and an interference path of the interference source through the DC bus to sensitive equipment in the multi-electric aircraft system is determined; The DC / DC converter branch comprises a half-bridge circuit, a transformer one, a rectifier and a filter; Equivalent interference source voltage V formed by IGBT in half-bridge circuit CM1 , inductance L of DC / DC converter input lead DCcab1 and parasitic capacitance C DCcab1 , inductance L of DC / DC converter output lead DCcab11 , emitter high-frequency parasitic capacitance C of IGBT in half-bridge circuit E1 and collector high-frequency parasitic capacitance C C1 , half-bridge circuit bridge arm midpoint capacitance C O1 , transformer one turn-to-turn parasitic capacitance and winding-to-winding parasitic capacitance, rectifier diode-to-ground capacitance C in rectifier D1 , parasitic capacitance of inductance and parasitic inductance of capacitance in filter The motor and driver branch comprises a permanent magnet synchronous motor and a motor driver, and the motor driver adopts a three-phase half-bridge circuit; Equivalent interference source voltage V formed by IGBT in three-phase half-bridge circuit CM2 , inductance L of motor driver input wire DCcab2 and parasitic capacitance C DCcab2 , high-frequency equivalent impedance Z of permanent magnet synchronous motor PMSM , emitter high-frequency parasitic capacitance C of IGBT in three-phase half-bridge circuit E2 and collector high-frequency parasitic capacitance C C2 , three-phase half-bridge circuit bridge arm midpoint to ground capacitance C O2 and inductance L of wire between motor driver and permanent magnet synchronous motor ACcab2 Build high-frequency equivalent model of motor and driver branch; The DC / AC inverter branch comprises a single-phase full-bridge circuit, a transformer two and an output filter; Equivalent interference source voltage V formed by IGBT in single-phase full-bridge circuit CM3 , inductance L of DC / AC inverter input lead DCcab3 and parasitic capacitance C DCcab3 , inductance L of output lead ACcab3 , emitter high-frequency parasitic capacitance C of IGBT in single-phase full-bridge circuit E3 and collector high-frequency parasitic capacitance C C3 , single-phase full-bridge circuit bridge arm midpoint-to-ground capacitance C O3 , turns parasitic capacitance and inter-winding parasitic capacitance of transformer two, parasitic capacitance of inductance and parasitic inductance of capacitance in output filter to build high-frequency equivalent model of DC / AC inverter branch; Selecting the working condition 1 as the DC / DC converter branch is running on the network, the motor and driver branch and the DC / AC inverter branch are shut down, then the IGBT bridge arm in the motor driver and the DC / AC inverter forms a new interference current conduction path to the DC / DC converter, including the IGBT bridge arm upper tube to ground capacitance 3C C2 and 2C C3 , the IGBT bridge arm lower tube to ground capacitance 3C E2 and 2C E3 , wire inductance L DCcab2 / 2 and L DCcab3 / 2; then the impedance of the new interference current conduction path is: （1）， wherein is the equivalent impedance of the inductance L DCcab3 DCcab2 is the equivalent impedance of the inductance L is the equivalent impedance of the inductance L and are intermediate variables:​ Z BUS2 =3Z C2 +3Z E2 +2Z DCCcab2 , Z BUS3 =2Z C3 +2Z E3 +2Z DCCcab3 , where Z C2 is the equivalent impedance of the collector high frequency parasitic capacitance C C2 , Z E2 is the equivalent impedance of the emitter high frequency parasitic capacitance C E2 , Z DCCcab2 is the equivalent impedance of the parasitic capacitance C DCcab2 ; Z C3 is the equivalent impedance of the collector high frequency parasitic capacitance C C3 , Z E3 is the equivalent impedance of the emitter high frequency parasitic capacitance C E3 , Z DCCcab3 is the equivalent impedance of the parasitic capacitance C DCcab3 ; If the common-mode current of the working condition 1 is is: （2）， where Z DCload is the DC load impedance to ground, Z DCcab11 is the inductance L DCcab11 equivalent impedance, Z DCfilt1 is the equivalent impedance of the filter inductance L DCfilt1 in the DC / DC converter, Z D1 is the rectifier diode impedance to ground in the DC / DC converter, Z c1 is the equivalent impedance of the transformer one turn-to-turn parasitic capacitance, Z T1 is the equivalent impedance of the transformer one winding-to- winding parasitic capacitance, Z O1 is the equivalent impedance of the half-bridge circuit IGBT bridge arm midpoint capacitance C O1 to ground, Z GRID is the common mode impedance of the LISN, Z DCLcab1 is the equivalent impedance of the wire inductance L DCLcab1 ; Z DCCcab1 is the equivalent impedance of the parasitic capacitance C DCcab1 ; Z IGBT1 Equivalent impedance for IGBT in half-bridge circuit: ， where Z C1 is the equivalent impedance of the collector high-frequency parasitic capacitance C C1 Z E1 is the equivalent impedance of the emitter high-frequency parasitic capacitance C E1 .

2. The method of interference source analysis for system conducted electromagnetic interference interactions of more electric aircraft as defined in claim 1, wherein, High-frequency parameters in the high-frequency equivalent model of each branch are determined by measurement and fitting; On the basis of the high-frequency equivalent circuit, the superposition theorem is used to analyze the interactive electromagnetic interference of the aircraft system, and the interference path of the interactive electromagnetic interference to sensitive equipment in the multi-electric aircraft system is predicted according to the calculated high-frequency parameters in the high-frequency equivalent model.

3. The method of analyzing sources of interference for system conducted electromagnetic interference interactions of a more electric aircraft of claim 2, wherein, The specific calculation method of the high-frequency parameters in the high-frequency equivalent model of each branch is as follows: Impedance parameters of the high-frequency equivalent model are derived to obtain an impedance relationship containing unknown high-frequency parameters, actual impedance characteristic curves of the equipment are tested by using an impedance analyzer to obtain actual impedance characteristic data, and the actual impedance characteristic curves are fitted by using the impedance relationship containing unknown high-frequency parameters to calculate the values of the corresponding high-frequency parameters in each high-frequency equivalent model.

4. The method of analyzing sources of interference for system conducted electromagnetic interference interactions of a more electric aircraft of claim 3, wherein, Common mode current according to operating condition 1 Analysis of the interference path gives: In the low frequency band, the frequency f is small, and because L DCcab2 / 2, L DCcab3 / 2, C E2 , C E3 , C C2 and C C3 have values of the order of μH and pF, Z DC2,3 represents an inductive impedance greater than Z GRID ; since Z DC2,3 is in parallel with Z GRID , the new interference current conduction path does not have a significant impact on the conducted electromagnetic interference of the DC / DC converter; As the frequency increases, when Z DC2,3 The new interference current conduction path has a significant impact on the conducted electromagnetic interference of the DC / DC converter when Z Z c1 + Z T1 is a value greater than Z DCload , the DC / DC converter is less affected by the DC load impedance to ground Z DCload .

5. The method of claim 4, wherein the system conducted electromagnetic interference interaction interference source analysis for more electric aircraft systems is characterized by, The working condition 2 is selected as the DC / DC converter branch, the motor and the driver branch and the DC / AC inverter branch are all connected to the network; the common-mode current generated at the DC side of the DC / DC converter is calculated respectively, and the superposition theorem is used to obtain the total common-mode current of the working condition 2 : （3）， wherein is the common mode current generated by the DC / DC converter branch at its DC side, is the common mode current generated by the motor and driver branch at the DC / DC converter DC side, is the common mode current generated by the DC / AC inverter branch at the DC / DC converter DC side; The branch equivalent impedance of each branch is calculated as follows: （4）， In the formula is the equivalent impedance of the DC / DC converter branch; Z is the equivalent impedance of the motor and driver branch ACcab2 Z is the equivalent impedance of the wire inductance L ACcab2 Z is the equivalent impedance of the wire inductance L O2 Z is the equivalent impedance of the three-phase half-bridge circuit IGBT bridge arm midpoint to ground capacitance C O2 Z is the equivalent impedance of the three-phase half-bridge circuit IGBT bridge arm midpoint to ground capacitance C DCLcab2 Z is the equivalent impedance of the inductance L DCLcab2 Z is the equivalent impedance of the inductance L DCCcab2 Z is the equivalent impedance of the parasitic capacitance C DCcab2 Z is the equivalent impedance of the parasitic capacitance C The equivalent impedance of the IGBT in the three-phase half-bridge circuit is: ， where Z C2 is the equivalent impedance of the collector high-frequency parasitic capacitance C C2 Z E2 is the equivalent impedance of the emitter high-frequency parasitic capacitance C E2 ; Z is the equivalent impedance of the DC / AC inverter branch. AC3 Z is the AC load impedance to ground. ACcab3 For inductor L ACcab3 The equivalent impedance, Z ACfilt3 Z is the output filter impedance to ground. c3 Z is the equivalent impedance of the inter-turn parasitic capacitance of transformer two. T3 Z is the equivalent impedance of the parasitic inter-winding capacitance of transformer two. O3 The capacitance to ground at the midpoint of the IGBT bridge arm in a single-phase full-bridge circuit is C. O3 The equivalent impedance, Z DCLcab3 For inductor L DCcab3 The equivalent impedance, Parasitic capacitance C DCcab3 The equivalent impedance; Equivalent impedance of IGBT in single-phase full-bridge circuit: ， where Z C3 is the equivalent impedance of the collector high-frequency parasitic capacitance C C3 Z E3 is the equivalent impedance of the emitter high-frequency parasitic capacitance C E3 ; Then: （5）， （6）， （7）。 6. The interference source analysis method for the interactive electromagnetic interference of the multi-electric aircraft system according to claim 5, characterized in that, Common mode current according to operating condition 2 、 and Analysis of the DC / DC converter disturbance path: 1) Analysis of the equivalent disturbance source voltage V CM1 The generated influence is V CM2 and V CM3 = 0; the motor and driver branch and the DC / AC inverter branch additionally introduce C O2 , C O3 , equivalent impedance Z c3 + Z T3 and Z PMSM when they are connected to the grid; Z GRID = 25 Ω, at low frequencies, the impedance of Z2 and Z3 is much greater than 25 Ω, the disturbance generated by the path of Z GRID is the main disturbance; as the frequency increases, when the parallel impedance of Z2 and Z3 approaches or is less than 25 Ω, Z2 and Z3 have a significant impact on ; 2) analyze equivalent interference source voltage V CM2 The generated influence is V CM1 and V CM3 = 0; the interference source V CM2 produces an interference of size on the DC side of the DC / DC converter, thereby affecting the DC / DC converter; similarly, the interference source V CM3 produces an interference of size on the DC side of the DC / DC converter; and The impact on the DC / DC converter will be determined by its size: If or then the disturbance generated by the DC / DC converter itself is the main disturbance; If or then the interference source V CM2 and V CM3 produces an interference greater than the interference produced by the DC / DC converter itself; If or then the interference source V CM2 and V CM3 produces at least one greater than the interference produced by the DC / DC converter itself.

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