A method for modeling transient conducted electromagnetic interference of a high-power electromagnetic system based on multi-port equivalent circuit cascading

Abstract

The application discloses a strong electromagnetic system transient conducted electromagnetic interference modeling method based on multi-port equivalent circuit cascade, comprising the following steps: 1) establishing a super capacitor multi-port transient conducted EMI model; 2) establishing a multi-phase motor multi-port transient conducted EMI model containing parasitic effects; 3) calculating multi-phase motor equivalent circuit parameters; 4) based on the multi-phase motor equivalent circuit parameters, establishing a multi-port transient conducted EMI model of the multi-phase motor; 5) establishing a multi-port equivalent circuit cascade-based strong electromagnetic system transient conducted electromagnetic interference system level model, which is used for calculating common mode electromagnetic interference and differential mode electromagnetic interference characteristics of a direct current side of the strong electromagnetic system. The application can be used for predicting transient conducted electromagnetic interference characteristics of a high-power strong electromagnetic system, laying a foundation for conducted electromagnetic interference analysis of a high-power strong electromagnetic system working transiently on a ship platform and conducted electromagnetic interference suppression.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility, specifically a method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading. Background Technology

[0002] To ensure the stable operation of high-power transient electromagnetic systems, pulsed power supplies are typically used as the DC source, high-capacity, high-switching-frequency multiphase DC-AC inverters are used as energy conversion devices, and high-thrust-density linear motors are used as loads. Among these, the multiphase DC-AC inverters operating at high switching frequencies are one of the main sources of electromagnetic interference in marine platform electromagnetic systems. Furthermore, considering the extremely short operating time of these systems, how to perform system-level modeling of transient conducted electromagnetic interference has always been a challenging problem in the field of electromagnetic compatibility.

[0003] Modern ship platforms, due to the extensive use of power electronic devices, exhibit a more complex electromagnetic environment compared to traditional ships. The resulting electromagnetic interference (EMI) is becoming a significant factor affecting the reliability and safety of power systems. With the increasing voltage levels and faster switching speeds of high-power switching devices, more and more high-power electromagnetic systems can operate effectively in short-time states. In these systems, the power conversion devices generate large dv / dt and di / dt values ​​during high-frequency switching, acting as strong electromagnetic interference sources over a wide frequency range. This causes severe transient conducted electromagnetic interference within the entire high-power electromagnetic system and its interfaced power systems, affecting the normal and safe operation of other equipment on the platform.

[0004] A typical high-power electromagnetic system on a ship platform mainly consists of a supercapacitor energy storage unit, a multiphase DC-AC inverter, and a multiphase motor. Supercapacitors, due to their advantages of large discharge current, short discharge time, and high energy density, can perform instantaneous high-current discharge when used as energy storage devices. Therefore, they are commonly used in high-power electromagnetic systems (such as electromagnetic launch systems and high-thrust-density linear motors) as pulse power sources to provide energy for the system's instantaneous operation. Multiphase DC-AC inverters, with their high power, high efficiency, and fast energy conversion speed, can convert the instantaneous DC energy generated by the supercapacitor pulse power source into instantaneous AC energy to power the high-thrust-density motor during the instantaneous operation of a high-power electromagnetic system. Multiphase motors, with neutral point isolation and no zero-sequence current component, are more suitable for high-voltage, high-power instantaneous operation. Their high thrust density can also accelerate the load to a specified speed instantaneously, thus they are widely used in typical high-power electromagnetic systems. However, the overall operating time of high-power electromagnetic systems is extremely short, and the instantaneous conducted electromagnetic interference generated by them is different from the traditional periodic conducted electromagnetic interference. It is highly time-varying. Therefore, by establishing a multi-port instantaneous conducted electromagnetic interference model for each module, and then cascading the equivalent circuits to construct a system-level instantaneous conducted electromagnetic interference model, we can carry out transient conducted electromagnetic interference analysis of high-power electromagnetic systems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for modeling instantaneous conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading, comprising the following steps:

[0006] 1) Establish a multi-port transient conducted EMI model of a supercapacitor with a pulse power supply;

[0007] 2) Determine the circuit topology of the multiphase DC-AC inverter and establish a multiphase motor multi-port transient conducted EMI model that includes parasitic effects;

[0008] 3) The transient conducted EMI model of the multiphase motor is processed using differential-mode and common-mode impedance measurement methods, and the equivalent circuit parameters of the multiphase motor are calculated.

[0009] 4) Based on the equivalent circuit parameters of the multiphase motor, a multi-port transient conducted EMI model of the multiphase motor is established;

[0010] 5) Establish a system-level model of transient conducted electromagnetic interference for a strong electromagnetic system based on data flow-based multi-port equivalent circuit cascade, including a supercapacitor multi-port transient conducted EMI model, a multi-phase motor multi-port transient conducted EMI model, and a multi-phase motor multi-port transient conducted EMI model.

[0011] Among them, the supercapacitor multi-port transient conducted EMI model provides power, and the multiphase DC-AC inverter multi-port transient conducted EMI model transmits power to the multiphase motor multi-port transient conducted EMI model.

[0012] The transient conducted electromagnetic interference system-level model is used to calculate the common-mode and differential-mode electromagnetic interference characteristics of a strong electromagnetic system on the DC side of a motor.

[0013] Furthermore, the circuit topology of the supercapacitor multi-port transient conducted EMI model is shown below:

[0014] Let A be the positive terminal of DC power supply U and B be the negative terminal.

[0015] Terminal A is connected in series with switch K1 and supercapacitor C, and then connected to terminal B; terminal B is grounded.

[0016] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, supercapacitor stray inductor L2, and supercapacitor stray inductor L2, and then connected to the cathode of diode D; the anode of diode D is grounded.

[0017] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, inductor L3, and resistor R3, and then grounded.

[0018] Wherein, inductor L3 is the inductance of the pulse reactor, and resistor R3 is the sum of the pulse reactor resistance and the simulated load resistance.

[0019] Furthermore, in step 2), the control method for the multi-port transient conducted EMI model of the multiphase DC-AC inverter, which includes parasitic effects, is as follows:

[0020] The three-phase bridge arms of the lagging phases A2-B2-C2 of the multiphase DC-AC inverter use SPWM control, and their modulation wave signals are sequentially 120° electrical degrees out of phase.

[0021] In a multiphase DC-AC inverter, the leading phase A1-B1-C1 switching arms need to be 30° electrical angle ahead of the corresponding lagging phase arm for each phase. The multiphase DC-AC inverter as a whole achieves a dual SPWM control mode with a phase difference of 30° electrical angle.

[0022] Furthermore, the steps for processing the multi-port transient conducted EMI model of a multiphase motor using differential-mode and common-mode impedance measurement methods include:

[0023] 3.1) Measure the impedance between the leading and lagging windings and the third phase in a multiphase motor using the differential mode impedance measurement method;

[0024] 3.2) Measure the impedance between the leading and lagging windings and the grounding terminal of the motor casing in a multiphase motor using the common-mode impedance measurement method;

[0025] 3.3) Calculate the peak value f of the parallel resonance. p1 and series resonant frequency f d1 ,Right now:

[0026]

[0027]

[0028] Wherein, capacitor C D(n-1) and inductor L D(n-1) As shown below:

[0029]

[0030]

[0031] In the formula, C D This is the total differential-mode capacitance;

[0032] 3.4) Repeat step 3.3) to determine the parallel resonance peak value {f} at different frequency bands. p1 f p2 ... f pn} and series resonant frequency {f d1 f d2 ... f dn};

[0033] 3.5) Calculate the common-mode inductance and capacitance parameters, i.e.:

[0034]

[0035] In the formula, i is the frequency band number; L Ci C Ci Here are the common-mode inductance and capacitance parameters for frequency band i;

[0036] 3.6) Calculate the equivalent circuit parameters of the multiphase motor, i.e.:

[0037]

[0038]

[0039]

[0040] In the formula, L i C i R i For the inductance, capacitance, and resistance of the equivalent circuit of a multiphase motor; C Di L is the differential-mode capacitance at frequency band i;Di R is the differential mode inductance in frequency band i; Di Let be the differential mode resistance at frequency band i.

[0041] Furthermore, in the multi-port transient conducted EMI model of the multiphase motor, the three voltage sources E at the end of each phase are... a E b and E c This represents the reverse electromagnetic force of a dual three-phase motor at the base frequency; the voltage source is obtained through the voltage, base frequency current, and speed at the steady-state operating point.

[0042] Furthermore, in step 5), the transient conducted electromagnetic interference system-level model is built in the Simulink environment.

[0043] Furthermore, the energy E required by the transient conducted electromagnetic interference system-level model during instantaneous operation is shown below:

[0044] The energy required for the instantaneous operation of the strong electromagnetic system is obtained by integrating the product of the voltage and current on the output side of the supercapacitor as a pulse power source in the time domain, as shown in the following formula:

[0045]

[0046] Where t0 and t1 represent the start and stop times of the strong electromagnetic system, respectively; u(t) is the voltage on the output side of the pulse power supply; and i(t) is the current on the output side of the pulse power supply.

[0047] The technical effectiveness of this invention is undeniable. This patent proposes a modeling method for transient conducted electromagnetic interference (EMI) in high-power electromagnetic systems based on multi-port equivalent circuit cascading. This method can be used to predict the transient EMI characteristics of high-power electromagnetic systems, laying the foundation for the analysis of conducted EMI in high-power electromagnetic systems operating instantaneously on ship platforms and for suppressing conducted EMI.

[0048] This invention establishes a multi-port transient conducted EMI modeling method for supercapacitor energy storage cabinets as pulsed DC power supplies. The model can clearly represent the characteristics of large discharge current and high instantaneous output energy, and can be directly used in the conducted EMI modeling and simulation of instantaneous high-power electromagnetic systems, providing model support for subsequent instantaneous modeling of strong electromagnetic systems.

[0049] This invention establishes a modeling method for multi-port transient conducted EMI models of dual- and three-phase DC-AC inverters that uses conducted interference transient analysis and considers factors such as control mode and load motor topology. This modeling method has clear physical concepts, is easy to operate, and can be directly extended to transient conducted EMI modeling of other multi-phase DC-AC inverters.

[0050] This invention presents a modeling method for transient conducted EMI system-level models of strong electromagnetic systems based on data flow-based multi-port equivalent circuit cascades. The method features a concise and clear model, a clear modeling process, and accurate simulation results. It can provide model and simulation data support for subsequent quantitative analysis of transient conducted electromagnetic interference and can be extended to the modeling of other transient strong electromagnetic systems, thus having broad application value. Attached Figure Description

[0051] Figure 1 Flowchart for system-level modeling of transient conducted EMI in high-power electromagnetic equipment;

[0052] Figure 2 This is a schematic diagram of a supercapacitor pulse power supply circuit.

[0053] Figure 3 This is a simulation circuit diagram for a supercapacitor pulse power supply.

[0054] Figure 4 This refers to the terminal voltage during the discharge phase of the supercapacitor pulse power supply.

[0055] Figure 5 This refers to the magnitude of the discharge current of the supercapacitor pulse power supply.

[0056] Figure 6 This refers to the discharge energy of the supercapacitor pulse power supply.

[0057] Figure 7 A physical characteristic model of a multiphase motor;

[0058] Figure 8 This is the stator winding structure for a neutral-point isolated multiphase motor.

[0059] Figure 9 This is a topology diagram of a multiphase DC-AC inverter and a multiphase motor cascaded circuit.

[0060] Figure 10 A single-phase bridge arm model of the inverter considering parasitic parameters;

[0061] Figure 11 SPWM control diagram for a multiphase DC-AC inverter;

[0062] Figure 12 For multiphase motor common-mode impedance testing;

[0063] Figure 13 Differential mode impedance testing for multiphase motors;

[0064] Figure 14 (a) shows the single-phase equivalent circuit for DM impedance measurement. Figure 14 (b) is the single-phase equivalent circuit for CM impedance measurement;

[0065] Figure 15For the falling frequency f d1 and peak frequency f p2 Equivalent circuit model between;

[0066] Figure 16 An equivalent circuit model of a set of windings for a multiphase motor;

[0067] Figure 17 Simulation of dual SPWM control mode with a phase difference of 30° electrical angle;

[0068] Figure 18 This is a time-domain simulation circuit model for EMI in a multiphase motor.

[0069] Figure 19 A simulation model for transient conducted EMI in high-power electromagnetic equipment;

[0070] Figure 20 This is the terminal voltage on the DC side of the supercapacitor;

[0071] Figure 21 This refers to the discharge current on the DC side of the supercapacitor.

[0072] Figure 22 This refers to the discharge energy on the DC side of the supercapacitor.

[0073] Figure 23 This refers to the three-phase current on the output side of a multiphase DC-AC inverter.

[0074] Figure 24 This refers to the output line voltage of a multiphase DC-AC inverter.

[0075] Figure 25 Comparison of A-phase currents of the leading and lagging bridges on the output side of a multiphase inverter;

[0076] Figure 26 The differential mode current spectrum of conducted EMI on the DC side of high-power electromagnetic equipment;

[0077] Figure 27 The common-mode current spectrum of conducted EMI on the DC side of high-power electromagnetic equipment;

[0078] Figure 28 The differential mode voltage spectrum of conducted EMI on the DC side of high-power electromagnetic equipment;

[0079] Figure 29 This refers to the common-mode voltage spectrum of conducted EMI on the DC side of high-power electromagnetic equipment. Detailed Implementation

[0080] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0081] Example 1:

[0082] See Figures 1 to 29 A method for modeling instantaneous conducted electromagnetic interference in a strong electromagnetic system based on cascaded multi-port equivalent circuits includes the following steps:

[0083] 1) Establish a multi-port transient conducted EMI model of a supercapacitor with a pulse power supply;

[0084] 2) Determine the circuit topology of the multiphase DC-AC inverter and establish a multiphase motor multi-port transient conducted EMI model that includes parasitic effects;

[0085] 3) The transient conducted EMI model of the multiphase motor is processed using differential-mode and common-mode impedance measurement methods, and the equivalent circuit parameters of the multiphase motor are calculated.

[0086] 4) Based on the equivalent circuit parameters of the multiphase motor, a multi-port transient conducted EMI model of the multiphase motor is established;

[0087] 5) Establish a system-level model of transient conducted electromagnetic interference for electromagnetic systems based on data flow multi-port equivalent circuit cascade, including a supercapacitor multi-port transient conducted EMI model, a multi-phase motor multi-port transient conducted EMI model, and a multi-phase motor multi-port transient conducted EMI model.

[0088] Among them, the supercapacitor multi-port transient conducted EMI model provides power, and the multiphase DC-AC inverter multi-port transient conducted EMI model transmits power to the multiphase motor multi-port transient conducted EMI model.

[0089] The transient conducted electromagnetic interference system-level model is used to calculate the common-mode and differential-mode electromagnetic interference characteristics of a strong electromagnetic system on the DC side of a motor.

[0090] The circuit topology of the supercapacitor multi-port transient conducted EMI model is shown below:

[0091] Let A be the positive terminal of DC power supply U and B be the negative terminal.

[0092] Terminal A is connected in series with switch K1 and supercapacitor C, and then connected to terminal B; terminal B is grounded.

[0093] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, supercapacitor stray inductor L2, and supercapacitor stray inductor L2, and then connected to the cathode of diode D; the anode of diode D is grounded.

[0094] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, inductor L3, and resistor R3, and then grounded.

[0095] Wherein, inductor L3 is the inductance of the pulse reactor, and resistor R3 is the sum of the pulse reactor resistance and the simulated load resistance.

[0096] In step 2), the control method for the multi-port transient conducted EMI model of the multiphase DC-AC inverter, which includes parasitic effects, is as follows:

[0097] The three-phase bridge arms of the lagging phases A2-B2-C2 of the multiphase DC-AC inverter use SPWM control, and their modulation wave signals are sequentially 120° electrical degrees out of phase.

[0098] In a multiphase DC-AC inverter, the leading phase A1-B1-C1 switching arms need to be 30° electrical angle ahead of the corresponding lagging phase arm for each phase. The multiphase DC-AC inverter as a whole achieves a dual SPWM control mode with a phase difference of 30° electrical angle.

[0099] The steps for processing the multi-port transient conducted EMI model of a multiphase motor using differential-mode and common-mode impedance measurement methods include:

[0100] 3.1) Measure the impedance between the leading and lagging windings and the third phase in a multiphase motor using the differential mode impedance measurement method;

[0101] 3.2) Measure the impedance between the leading and lagging windings and the grounding terminal of the motor casing in a multiphase motor using the common-mode impedance measurement method;

[0102] 3.3) Calculate the peak value f of the parallel resonance. p1 and series resonant frequency f d1 ,Right now:

[0103]

[0104]

[0105] Wherein, capacitor C D(n-1) and inductor L D(n-1) As shown below:

[0106]

[0107]

[0108] In the formula, C D This is the total differential-mode capacitance;

[0109] 3.4) Repeat step 3.3) to determine the parallel resonance peak value {f} at different frequency bands. p1 fp2 ... f pn} and series resonant frequency {f d1 f d2 ... f dn};

[0110] 3.5) Calculate the common-mode inductance and capacitance parameters, i.e.:

[0111]

[0112] In the formula, i is the frequency band number; L Ci C Ci Here are the common-mode inductance and capacitance parameters for frequency band i;

[0113] 3.6) Calculate the equivalent circuit parameters of the multiphase motor, i.e.:

[0114]

[0115]

[0116]

[0117] In the formula, L i C i R i For the inductance, capacitance, and resistance of the equivalent circuit of a multiphase motor; C Di L is the differential-mode capacitance at frequency band i; Di R is the differential mode inductance in frequency band i; Di Let be the differential mode resistance at frequency band i.

[0118] The multi-port transient conducted EMI model of the multiphase motor has three voltage sources E at the end of each phase. a E b and E c This represents the reverse electromagnetic force of a dual three-phase motor at the base frequency; the voltage source is obtained through the voltage, base frequency current, and speed at the steady-state operating point.

[0119] In step 5), the transient conducted electromagnetic interference system-level model is built in the Simulink environment.

[0120] The energy E required by the transient conducted electromagnetic interference system-level model during instantaneous operation is shown below:

[0121] The energy required for the instantaneous operation of the strong electromagnetic system is obtained by integrating the product of the voltage and current on the output side of the supercapacitor as a pulse power source in the time domain, as shown in the following formula:

[0122]

[0123] Where t0 and t1 represent the start and stop times of the strong electromagnetic system, respectively; u(t) is the voltage on the output side of the pulse power supply; and i(t) is the current on the output side of the pulse power supply.

[0124] Example 2:

[0125] A method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading includes the following:

[0126] First, a multi-port transient conducted EMI model of a supercapacitor as a pulse power source is established based on its instantaneous discharge characteristics. Then, based on the physical characteristics analysis of the multiphase motor, the circuit topology of the multiphase DC-AC inverter is determined, and a multi-port transient conducted EMI model of the multiphase DC-AC inverter, including parasitic effects, is constructed. Next, a multi-segment linear RLC circuit is established to fit the behavioral characteristics of the multiphase motor through differential-mode (DM) and common-mode (CM) impedance measurements, and a multi-port transient conducted EMI model of the multiphase motor is established through series and parallel connections. Finally, a system-level model of transient conducted electromagnetic interference for a strong electromagnetic system based on cascaded multi-port equivalent circuits is established. A system-level simulation circuit is built in Matlab / Simulink to analyze the time-domain waveform under instantaneous operating conditions. The time-domain simulation results under instantaneous operating conditions are compared with actual operating conditions from the perspectives of voltage, current, and energy, verifying the correctness of the system-level modeling method for transient conducted electromagnetic interference. Thus, a modeling method for transient conducted electromagnetic interference of a strong electromagnetic system based on cascaded multi-port equivalent circuits is formed.

[0127] The specific implementation technical solution is as follows:

[0128] (1) Based on the working characteristics of instantaneous discharge of supercapacitor, a multi-port transient conducted EMI model of supercapacitor as a pulse power source is established.

[0129] Considering the unique operating characteristics of high-power electromagnetic systems, which require instantaneous high-current, high-power energy devices as DC power sources, supercapacitors, with their advantages of large discharge current, short discharge time, and high energy density, can serve as pulse power sources when used as energy storage devices. Therefore, when modeling multi-port transient conducted EMI for supercapacitors as pulse power sources, the main considerations are the voltage changes at the supercapacitor terminals during discharge and the stray parameters generated during the discharge process. The multi-port transient conducted EMI model is as follows: Figure 2As shown in the diagram. U represents the DC power supply, C represents the supercapacitor, K1 and K2 represent two switches respectively, R1, R2, L1, and L2 are stray parameters within the supercapacitor, D represents the freewheeling silicon stack, inductance L3 is the sum of the pulse reactor inductance and the load inductance, and resistance R3 is the sum of the pulse reactor resistance and the simulated load resistance. The discharge process of the multi-port transient conducted EMI model using the supercapacitor as a pulse power supply is shown below:

[0130] ① After the supercapacitor C is fully charged, the discharge switch K2 is turned on, connecting the supercapacitor, reactor, and simulated load in series to form a circuit. The supercapacitor C releases energy to the load through the reactor L. In strong electromagnetic equipment, the load resistance is typically tens of milliohms. At this time, The circuit operates in an underdamped state, the current decays oscillatingly, and the reactor stores energy.

[0131] ② Once the supercapacitor C has released all its energy, the main discharge switch no longer bears the positive voltage. As the current rapidly decreases, the main discharge switch quickly turns off. Simultaneously, the high-power silicon stack turns on, and the discharge circuit gradually switches from an RLC series circuit to an RL circuit. This switching process is extremely brief.

[0132] ③ The freewheeling silicon stack D turns on. The reactor L releases the energy stored in stage ① to the load. At this time, the main discharge switch turns off, the freewheeling silicon stack turns on, providing a discharge circuit for the reactor. The discharge circuit changes to the RL circuit.

[0133] (2) Based on the analysis of the physical characteristics of multiphase motors, the circuit topology of multiphase DC-AC inverters is determined, a multi-port transient conducted EMI model of multiphase DC-AC inverters including parasitic effects is constructed, and a new dual SPWM control method is determined.

[0134] The physical model of a multiphase motor is as follows Figure 7 As shown, the stator winding structure of a neutral-point isolated multiphase motor is as follows: Figure 8 As shown. Because the neutral point of the two sets of windings in a dual three-phase motor is not connected, there is no zero-sequence current component, and effective electrical isolation is achieved, it is more suitable for high-voltage, instantaneous high-power operation. Therefore, this patent uses the neutral-point isolated dual three-phase motor as a representative research object of multiphase motors.

[0135] Meanwhile, considering factors such as the 30° electrical angle difference between the phases, the neutral point isolation of the multiphase motor's physical structure, and the parasitic effects of the switching transistors themselves, a multi-port transient conducted EMI model is studied using a multiphase DC-AC inverter as the research object. The circuit model is as follows: Figure 9 As shown in the diagram, in the equivalent modeling, the multiphase DC-AC inverter is treated as two sets of three-phase DC-AC inverters connected in parallel to drive the multiphase motor. From Figure 9As can be seen, the multiphase DC-AC inverter module consists of six bridge arms, with a total of twelve semiconductor IGBT elements, and is accompanied by parasitic elements. The transient electromagnetic interference (EMI) generated by multi-switch circuits is essentially the same as that generated by single-phase bridge arms, both due to the dv / dt generated during switching. Therefore, to simply and accurately describe the generation and propagation of EMI, an EMI model for single-phase bridge arms incorporating parasitic effects is established, as shown below. Figure 10 As shown. Where C e C c and C p These are the parasitic capacitances from the emitter to the housing, from the collector to the housing, and from the midpoint of the bridge arm (emitter / collector node) to the housing; C j It is the junction capacitance of the IGBT switching transistor; L T This is the loop inductance generated by the terminals of the IGBT module. All of the above parasitic parameters can be extracted using simple impedance measurement methods, and will not be elaborated further.

[0136] Considering the unique physical structure of multiphase motors—neutral point isolation and a 30° electrical angle difference between phases—and the direct connection between the multiphase DC-AC inverter circuit and the multiphase motor, a novel dual SPWM control method with a 30° electrical angle difference is used for its control. Figure 11 As shown, the three-phase bridge arms of the lagging phases A2-B2-C2 in the multiphase DC-AC inverter use SPWM control, with their modulation wave signals differing by 120° electrical angles sequentially. In addition, the switching bridge arms of the leading phases A1-B1-C1 in the multiphase DC-AC inverter need to lead the corresponding lagging phase bridge arm by 30° electrical angle for each phase. This ultimately achieves a novel dual SPWM control method with a 30° electrical angle difference, which eliminates circulating current influences within the multiphase DC-AC inverter, reduces harmonics, and enables the multiphase motor to operate safely and at high speed under high-quality sinusoidal signals with low torque ripple.

[0137] (3) The impedance behavior characteristics of a multiphase motor based on the fitting of a multi-segment linear RLC circuit are established by measuring differential mode (DM) and common mode (CM) impedance, and then a transient conducted EMI model of a multiphase motor based on a multi-port circuit is established.

[0138] Considering the difficulty in accurately grasping the electromagnetic structural details such as dimensions and windings of multiphase motors in electromagnetic compatibility modeling, this patent proposes a multi-port transient conducted EMI modeling method for dual three-phase motors based on time-domain simulation. Specifically, it establishes a method for fitting the behavioral characteristics of a multiphase motor by measuring differential-mode (DM) and common-mode (CM) impedances through corresponding multi-segment linear RLC circuits. Impedance measurements are mainly divided into common-mode impedance (Z... CM Measurement (e.g.) Figure 12 (as shown) and differential mode impedance (Z) DM ) Measurement (such as Figure 13 (As shown). Differential mode measurement involves shorting two phase terminals of the leading and lagging windings in the multiphase motor together and measuring their impedance to the third phase. Common mode impedance measurement involves shorting the terminals of the leading and lagging windings in the multiphase motor together and measuring their impedance to the grounding terminal of the motor casing. Subsequently, circuit parameters are extracted using the parallel and series resonant frequencies from the impedance measurement curves. To simplify the calculation of model parameters, only a few frequency points with significant impedance amplitude changes are considered. The equivalent circuits for single-phase DM and CM are shown below. Figure 14 As shown in (a) and (b), it is assumed that the inductance levels of each stage in the circuit differ significantly, i.e.

[0139]

[0140] ① The DM parameters are determined by the peak and fall frequency of the DM impedance. Without loss of generality, assume that the peak frequency of the parallel resonance (peak) and the trough frequency of the series resonance are {f...} p1 f p2 ... f pn} and {f d1 f d2 ... f dn According to formula (1), L D1 L D2 ..., L D(n-1) At frequency f p1 The following can be considered a short circuit, therefore it can start from below f p1 The impedance measurement curve determines the parameter L. Dn At the same time, f p1 It can be considered as an inductor L Dn And total DM capacitance C D =C D0 +C D1 +…+C D(n-1) The resonant frequency, i.e.

[0141]

[0142] In addition, f p1 The actual impedance magnitude at that point is the parallel resistance R. Dn The magnitude of. At frequency f. d1 and f p2 Between L Dn and R Dn It can be considered an open path, and L D1 L D2 ..., L D(n-2) Both can be considered short circuits, therefore they can be... Figure 14 The DM equivalent circuit in (a) is simplified to: Figure 15 The equivalent circuit shown has

[0143]

[0144]

[0145] Where C D(n-1) and L D(n-1) It can be obtained using the following formula:

[0146]

[0147]

[0148] By repeating formulas (3)-(6) above, the RLC equivalent circuit parameters in other frequency bands can be determined. Simultaneously, the parallel resistor R... D(n-1) From f p2 impedance value at Obtained from.

[0149] ② Regarding the CM parameters, the CM impedance at the first series resonant (trough) frequency f d1 The following circuit is capacitive, and all inductors can be considered short-circuited. Therefore, the low-frequency impedance curve can be used to determine the total capacitance C. C =C C0 +C C1 +…+C Cn Similar to the DM impedance curve, the first peak is formed by L. Cn and C Cn The parallel resonance caused by connecting it in series with all other capacitors is as follows:

[0150]

[0151] By repeating the above process, all CM inductance and capacitance parameters can be solved:

[0152]

[0153] Due to the resistance R of the CM equivalent circuit Ci With the resistor R of the DM circuit Di Therefore, it is not necessary to calculate R based on the CM impedance measurement value. Ci By solving for the parameters of the single-phase DM and CM circuits mentioned above, we can then obtain... Figure 16 The equivalent circuit parameters of the multiphase motor shown are as follows:

[0154]

[0155]

[0156]

[0157] Finally, the equivalent circuit model of a set of windings for a multiphase motor is as follows: Figure 16 As shown, this model can be used for time-domain simulation of conducted EMI in strong electromagnetic systems. It includes three voltage sources E at the end of each phase. a E b and E c The reverse electromagnetic force (EMF) of a dual three-phase motor at the base frequency can be obtained from the steady-state operating point (voltage, base frequency current, and speed).

[0158] (4) Establish a transient conducted EMI system-level model of a strong electromagnetic system based on a multi-port equivalent circuit cascaded with data flow, build the circuit in Simulink and simulate and calculate the time-domain waveforms of the output voltage, current and discharge energy of the multiphase inverter and the transient conducted electromagnetic interference characteristics on the DC side.

[0159] A system-level conducted electromagnetic interference (EMI) simulation circuit model of a strong electromagnetic device under transient operating mode was built in Matlab / Simulink. The energy supply module used the supercapacitor as the pulse power source in (1) to build a multi-port transient conducted EMI model. Based on the analysis in (2) and (3), a multi-port transient conducted EMI model of a multiphase DC-AC inverter and a high-frequency EMI model of a multiphase motor were built. The control method adopted was the novel dual SPWM control method with a phase difference of 30° electrical angle in (2) to ensure energy release and stable operation of the multiphase motor under transient operating conditions. At the same time, the ode23tb low-order rigid algorithm (trapezoidal rule and backward differential method) was used to calculate the AC side voltage and current of the multiphase DC-AC inverter. Simultaneously, the common-mode EMI and differential-mode EMI characteristics of the strong electromagnetic device on the DC side under transient operating mode were obtained through simulation calculation.

[0160] The energy required for the instantaneous operation of the strong electromagnetic system is obtained by integrating the product of the voltage and current on the output side of the supercapacitor as a pulse power source in the time domain, as shown in the following formula:

[0161]

[0162] Where t0 and t1 represent the start and stop times of the strong electromagnetic system, respectively. The instantaneous energy level is obtained through simulation calculation, and the correctness of the system-level modeling method is verified again from an energy perspective.

[0163] Example 3:

[0164] A method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading includes the following:

[0165] The EMI model of the multi-port equivalent circuit cascaded for transient conducted electromagnetic interference in the strong electromagnetic system in this case is as follows: Figure 19As shown, the initial voltage of the supercapacitor energy storage cabinet is V. pulse =660V, the supercapacitor has a capacitance of 32F, the multiphase DC-AC inverter adopts a dual SPWM control method with a phase difference of 30° electrical angle, its carrier signal frequency is 6kHz, the multiphase motor operating frequency is 117Hz, and the power supply time is set to 2s and the circuit simulation time is set to 3s according to actual working conditions. The research method of this invention for modeling transient conducted electromagnetic interference in high-power strong electromagnetic systems includes the following steps:

[0166] (1) Establish a multi-port transient conducted EMI model of the supercapacitor energy storage cabinet as a pulse power source.

[0167] The equivalent circuit model of the supercapacitor energy storage cabinet as a pulse power source, as proposed above, has the following circuit topology: Figure 2 As shown, the simulation circuit built in Matlab / Simulink is as follows. Figure 3 As shown, the simulation results of the supercapacitor energy storage cabinet as a pulse power source during the discharge phase, including terminal voltage, discharge current, and discharge energy, are as follows: Figure 4 — Figure 6 As shown. When switch K1 is closed, the supercapacitor C is charged; after the supercapacitor voltage stabilizes, K1 opens and K2 closes, discharging through diode D2. Diode D1 primarily serves to freewheel current at the end of the supercapacitor's discharge. Switch K1 is set to close within a time period of 0–0.001s, and then discharges the simulated load of the strong electromagnetic system within a time period of 0.001–2s. Figure 4 — Figure 6 Simulation results of the supercapacitor pulse power supply show that the terminal voltage of the supercapacitor energy storage cabinet can be stabilized at 660V in the initial stage. During the discharge process, its terminal voltage gradually decreases with the discharge time, and its instantaneous discharge current can reach a maximum of 43kA, with a discharge energy of 7MJ. Therefore, using the supercapacitor energy storage cabinet as a pulse power supply to power a high thrust density multiphase motor through a multiphase DC-AC inverter can meet its voltage, current, and energy requirements.

[0168] (2) Establish a multi-port transient conducted EMI model for a multiphase DC-AC inverter under a novel dual SPWM control mode with a phase difference of 30° electrical angle.

[0169] Based on the cascading of multiphase motors and multiphase DC-AC inverters, a multiphase DC-AC inverter model considering parasitic parameters and suitable for transient conducted electromagnetic interference is constructed. Its main circuit topology is as follows: Figure 9As shown, the main circuit structure consists of two sets of three-phase inverters connected in parallel. Since the switching devices exhibit certain parasitic effects during packaging and storage, providing a path for electromagnetic interference transmission, an electromagnetic interference model for a single-phase bridge arm considering parasitic effects is established as follows: Figure 10 As shown. The parasitic parameters can be solved using impedance analysis, yielding: C Link =925μF, L Link =9nH,C e =370pF, C c =88pF, C p =370pF, C j =12nF, L IGBT =24nH.

[0170] A multiphase motor stator structure with a star connection and a spatial phase difference of 30° electrical angle is used. A dual SPWM control method with a phase difference of 30° electrical angle is employed when controlling the multiphase DC-AC inverter. Its simulation circuit is as follows: Figure 17 As shown, in a multiphase DC-AC inverter, the leading phase SPWM control method and the lagging phase SPWM control method differ by 30° electrical angle, and their switching frequency can be changed by controlling the carrier frequency.

[0171] (3) Establish a multi-port transient conducted EMI model of a multiphase motor by measuring differential mode (DM) and common mode (CM) impedance.

[0172] The differential-mode and common-mode impedances of a static motor were measured using an impedance analyzer (Agilent 4294A). The wiring for the impedance measurement was as follows: Figure 12 and Figure 13 As shown. The measured impedances are the total differential-mode and common-mode impedances. Based on the relationship between the impedance of each phase and the total impedance of the multiphase motor, impedance transformation between each measured value and the corresponding part of the RLC linear circuit is achieved by extracting single-phase parameters. During parameterization, only series and parallel resonant points that significantly affect electromagnetic interference need to be considered. Each selected pair of peak and trough frequencies is fully separated and fitted using an RLC linear circuit. Finally, a multi-port transient time-domain EMI simulation circuit model of the multiphase motor is built in Matlab / Simulink, as shown below. Figure 18 As shown, the parameter of a single phase in a multiphase motor is L. a0 =353.24nH, L a1 =14.46μH, L a2 =94.19μH, R a1 =225.43Ω, R a2 =235.53Ω, C ag0 =1.11nF, C ag1 =6.98nF, Cag = 4.47nF. Due to the symmetry of the motor circuit, the corresponding parameter values ​​are the same for each phase. Furthermore, based on the multiphase motor nameplate parameters, the voltage source parameters in the equivalent circuit can be set to 114V and the frequency to 117Hz.

[0173] (4) Establish a transient conducted EMI system-level model of a strong electromagnetic system based on a multi-port equivalent circuit cascaded with data flow, and simulate and calculate the time-domain characteristics and transient conducted EMI characteristics on the DC side in Matlab / Simulink.

[0174] A system-level simulation circuit model of conducted electromagnetic interference from a transiently operating strong electromagnetic system was built in Matlab / Simulink. The simulation circuit diagram is shown below. Figure 19 As shown, the front end is a 32F supercapacitor energy storage cabinet as a pulse power supply multi-port transient conducted EMI model, the DC side is a LISN module, and the back end is a multiphase DC-AC inverter and a multiphase linear motor cascaded together. The multiphase DC-AC inverter is built using the equivalent circuit method of (2), and the parasitic parameter values ​​extracted by impedance analysis are imported into the equivalent circuit model. The operating voltage and current of the multiphase motor, as well as the conducted electromagnetic interference voltage and interference current on the DC side, are calculated by using the ode23tb low-order rigid algorithm (trapezoidal rule and backward differential method).

[0175] After a supercapacitor energy storage cabinet is used as a multi-port transient conducted EMI model for pulse power supply and connected to a strong electromagnetic system, its terminal voltage is as follows: Figure 20 As shown, the voltage amplitude gradually decreases from 660V, and the voltage variation range is within 60V, which meets the voltage fluctuation requirements of the energy storage element under single-operation conditions; the instantaneous discharge current can reach 7kA, as follows: Figure 21 As shown; the change of discharge energy with discharge time is as follows Figure 22 As shown, its discharge energy can reach 10MJ within 2 seconds, which is consistent with actual working conditions. Secondly, the three-phase current on the output side of the multiphase DC-AC inverter is as follows... Figure 23 As shown, the discharge period of 1 to 1.2 seconds is partially magnified, and the phase current waveform exhibits a sinusoidal waveform with a peak current reaching 8kA; the output line voltage is as follows. Figure 24 As shown, the trend is the same as that of the current change. Subsequently, a comparison is made between the leading and lagging phase currents of phase A on the output side of the dual three-phase DC-AC inverter. Figure 25 As shown, the phase current waveforms reveal similarities between the leading and lagging phase currents, exhibiting both leading and lagging phenomena. Overall, the time-domain simulation results of the system-level modeling of conducted electromagnetic interference in a strong electromagnetic system operating instantaneously conform to its actual operating conditions, thus verifying the correctness of the simulation model. This demonstrates that a modeling method for instantaneous conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading has been ultimately realized.

[0176] Furthermore, the differential-mode interference and common-mode interference current spectra of the DC side under the instantaneous operating state of the strong electromagnetic system, measured by the LISN module, are as follows: Figure 26 and Figure 27 As shown; the voltage spectrum diagrams of common-mode interference and differential-mode interference on the DC side are as follows. Figure 28 and Figure 29 As shown in the simulation results, the differential-mode interference and common-mode interference current generated during the instantaneous operation of a strong electromagnetic system have relatively high interference amplitudes at low frequencies, which gradually decrease as the frequency increases. The main interference frequencies are concentrated above even-order frequencies. The interference amplitude increases after 10MHz, which is due to the series resonance of parasitic parameters in the transmission path. The amplitudes of common-mode interference and differential-mode interference voltages also gradually decrease as the frequency increases. The main interference frequencies are concentrated above even-order harmonics, mainly at the low-frequency end and near the 10MHz band.

[0177] Example 4:

[0178] A method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascade, comprising the following steps:

[0179] 1) Establish a multi-port transient conducted EMI model of a supercapacitor with a pulse power supply;

[0180] 2) Determine the circuit topology of the multiphase DC-AC inverter and establish a multiphase motor multi-port transient conducted EMI model that includes parasitic effects;

[0181] 3) The transient conducted EMI model of the multiphase motor is processed using differential-mode and common-mode impedance measurement methods, and the equivalent circuit parameters of the multiphase motor are calculated.

[0182] 4) Based on the equivalent circuit parameters of the multiphase motor, a multi-port transient conducted EMI model of the multiphase motor is established;

[0183] 5) Establish a system-level model of transient conducted electromagnetic interference for a strong electromagnetic system based on data flow-based multi-port equivalent circuit cascade, including a supercapacitor multi-port transient conducted EMI model, a multi-phase motor multi-port transient conducted EMI model, and a multi-phase motor multi-port transient conducted EMI model.

[0184] Among them, the supercapacitor multi-port transient conducted EMI model provides power, and the multiphase DC-AC inverter multi-port transient conducted EMI model transmits power to the multiphase motor multi-port transient conducted EMI model.

[0185] The transient conducted electromagnetic interference system-level model is used to calculate the common-mode electromagnetic interference and differential-mode electromagnetic interference characteristics on the DC side of a strong electromagnetic system.

[0186] Example 5:

[0187] A method for modeling transient conducted electromagnetic interference (EMI) in a strong electromagnetic system based on multi-port equivalent circuit cascading is described in Example 4. The circuit topology of the supercapacitor multi-port transient conducted EMI model is shown below:

[0188] Let A be the positive terminal of DC power supply U and B be the negative terminal.

[0189] Terminal A is connected in series with switch K1 and supercapacitor C, and then connected to terminal B; terminal B is grounded.

[0190] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, supercapacitor stray inductor L2, and supercapacitor stray inductor L2, and then connected to the cathode of diode D; the anode of diode D is grounded.

[0191] Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, inductor L3, and resistor R3, and then grounded.

[0192] Wherein, inductor L3 is the inductance of the pulse reactor, and resistor R3 is the sum of the pulse reactor resistance and the simulated load resistance.

[0193] Example 6:

[0194] A method for modeling transient conducted electromagnetic interference (EMI) in a strong electromagnetic system based on cascaded multi-port equivalent circuits is described in Example 4. Specifically, in step 2), the control method for the multi-port transient conducted EMI model of a multiphase DC-AC inverter, which includes parasitic effects, is as follows:

[0195] The three-phase bridge arms of the lagging phases A2-B2-C2 of the multiphase DC-AC inverter use SPWM control, and their modulation wave signals are sequentially 120° electrical degrees out of phase.

[0196] In a multiphase DC-AC inverter, the leading phase A1-B1-C1 switching arms need to be 30° electrical angle ahead of the corresponding lagging phase arm for each phase. The multiphase DC-AC inverter as a whole achieves a dual SPWM control mode with a phase difference of 30° electrical angle.

[0197] Example 7:

[0198] A method for modeling transient conducted electromagnetic interference (EMI) in a strong electromagnetic system based on cascaded multi-port equivalent circuits is described in Example 4. The steps for processing the multi-port transient conducted EMI model of a multiphase motor using differential-mode and common-mode impedance measurement methods include:

[0199] 1) Measure the impedance between the leading and lagging windings and the third phase in a multiphase motor using the differential mode impedance measurement method;

[0200] 2) Measure the impedance between the leading and lagging windings and the grounding terminal of the motor casing in a multiphase motor using the common-mode impedance measurement method;

[0201] 3) Calculate the peak value f of the parallel resonance. p1 and series resonant frequency f d1 ,Right now:

[0202]

[0203]

[0204] Wherein, capacitor C D(n-1) and inductor L D(n-1) As shown below:

[0205]

[0206]

[0207] In the formula, C D This is the total differential-mode capacitance;

[0208] 4) Repeat step 3) to determine the parallel resonance peak value {f} in different frequency bands. p1 f p2 ... f pn} and series resonant frequency {f d1 f d2 ... f dn};

[0209] 5) Calculate the common-mode inductance and capacitance parameters, i.e.:

[0210]

[0211] In the formula, i is the frequency band number; L Ci C Ci Here are the common-mode inductance and capacitance parameters for frequency band i;

[0212] 6) Calculate the equivalent circuit parameters of the multiphase motor, i.e.:

[0213]

[0214]

[0215]

[0216] In the formula, L i C i R iFor the inductance, capacitance, and resistance of the equivalent circuit of a multiphase motor; C Di L is the differential-mode capacitance at frequency band i; Di R is the differential mode inductance in frequency band i; Di Let be the differential mode resistance at frequency band i.

[0217] Example 8:

[0218] A method for modeling transient conducted electromagnetic interference (EMI) in a strong electromagnetic system based on cascaded multi-port equivalent circuits is described in Example 4. The method involves three voltage sources E at the end of each phase of the multi-port transient conducted EMI model of the multi-phase motor. a E b and E c This represents the reverse electromagnetic force of a dual three-phase motor at the base frequency; the voltage source is obtained through the voltage, base frequency current, and speed at the steady-state operating point.

[0219] Example 9:

[0220] A method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascading is described in Example 4. In step 5), the transient conducted electromagnetic interference system-level model is built in the Simulink environment.

[0221] Example 10:

[0222] A method for modeling transient conducted electromagnetic interference in a strong electromagnetic system based on multi-port equivalent circuit cascade is described in Example 4. The energy E required by the transient conducted electromagnetic interference system-level model during instantaneous operation is shown below:

[0223] The energy required for the instantaneous operation of the strong electromagnetic system is obtained by integrating the product of the voltage and current on the output side of the supercapacitor as a pulse power source in the time domain, as shown in the following formula:

[0224]

[0225] Where t0 and t1 represent the start and stop times of the strong electromagnetic system, respectively; u(t) is the voltage on the output side of the pulse power supply; and i(t) is the current on the output side of the pulse power supply.

Claims

1. A method for modeling transient conducted electromagnetic interference of a high-power electromagnetic system based on cascading of multi-port equivalent circuits, characterized in that, Includes the following steps: Step 1) Establish a supercapacitor multi-port transient conducted EMI model with the supercapacitor as the pulse power source; Step 2) Determine the circuit topology of the multiphase DC-AC inverter and establish a multiphase motor multi-port transient conducted EMI model that includes parasitic effects; Step 3) The multi-port transient conducted EMI model of the multiphase motor is processed using differential-mode and common-mode impedance measurement methods to calculate the equivalent circuit parameters of the multiphase motor; Step 4) Based on the equivalent circuit parameters of the multiphase motor, establish a multi-port transient conducted EMI model of the multiphase motor; Step 5) Establish a system-level model of transient conducted electromagnetic interference for a strong electromagnetic system based on a multi-port equivalent circuit cascaded with data flow, including a multi-port transient conducted EMI model for supercapacitors, a multi-port transient conducted EMI model for multiphase motors, and a multi-port transient conducted EMI model for multiphase motors. Among them, the supercapacitor multi-port transient conducted EMI model provides power, and the multiphase DC-AC inverter multi-port transient conducted EMI model transmits power to the multiphase motor multi-port transient conducted EMI model. The transient conducted electromagnetic interference system-level model is used to calculate the common-mode electromagnetic interference and differential-mode electromagnetic interference characteristics on the DC side of a strong electromagnetic system. The steps for processing the multi-port transient conducted EMI model of a multiphase motor using differential-mode and common-mode impedance measurement methods include: Step 3.1) Measure the impedance between the leading and lagging windings and the third phase in a multiphase motor using the differential mode impedance measurement method; Step 3.2) Measure the impedance between the leading and lagging windings of the multiphase motor and the grounding terminal of the motor casing using the common-mode impedance measurement method; Step 3.3) Calculate parallel resonance peak and series resonance frequency i.e.: （1） （2） wherein the capacitor and the inductor are as follows: （3） （4） In the formula, C D is the total differential mode capacitance; Step 3.4) Repeat step 3.3) to determine the parallel resonance peak value , , } and series resonance frequency , , } at different frequency bands; Step 3.5) Calculate the common-mode inductance and capacitance parameters, i.e.: （5） In the formula, i is the frequency band sequence number; L Ci , C Ci is the common-mode inductance and capacitance parameters under the frequency band i; Step 3.6) Calculate the equivalent circuit parameters of the multiphase motor, i.e.: （6） （7） （8） wherein L i , C i , and R i are the inductance, capacitance, and resistance of the equivalent circuit of the polyphase electric machine; C Di is the differential mode capacitance under the frequency band i; L Di is the differential mode inductance under the frequency band i; and R Di is the differential mode resistance under the frequency band i.

2. The method according to claim 1, wherein, The circuit topology of the supercapacitor multi-port transient conducted EMI model is shown below: Let A be the positive terminal of DC power supply U and B be the negative terminal. Terminal A is connected in series with switch K1 and supercapacitor C, and then connected to terminal B; terminal B is grounded. Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, supercapacitor stray inductor L2, and supercapacitor stray inductor L2, and then connected to the cathode of diode D; the anode of diode D is grounded. Terminal A is connected in series with switch K1, switch K2, supercapacitor stray inductor L1, supercapacitor stray resistor R1, inductor L3, and resistor R3, and then grounded. Wherein, inductor L3 is the inductance of the pulse reactor, and resistor R3 is the sum of the pulse reactor resistance and the simulated load resistance.

3. The method of claim 1, wherein, In step 2), the control method for the multi-port transient conducted EMI model of the multiphase DC-AC inverter, which includes parasitic effects, is as follows: The three-phase bridge arms of the lagging phases A2-B2-C2 of the multiphase DC-AC inverter use SPWM control, and their modulation wave signals are sequentially 120° electrical degrees out of phase. In a multiphase DC-AC inverter, the leading phase A1-B1-C1 switching arms need to be 30° electrical angle ahead of the corresponding lagging phase arm for each phase. The multiphase DC-AC inverter as a whole achieves a dual SPWM control mode with a phase difference of 30° electrical angle.

4. The method of claim 1, wherein, Three voltage sources per phase end of the multiphase motor's multi-port transient conduction EMI model , and represent the inverse electromagnetic force of a dual three-phase motor at the fundamental frequency; The voltage source is obtained by the voltage at the steady state operating point, the fundamental frequency current, and the speed.

5. The method of claim 1, wherein, In step 5), the transient conducted electromagnetic interference system level model is built in the Simulink environment.

6. The method of claim 1, wherein, The size E of the energy required by the transient conducted electromagnetic interference system level model in the transient working process is as follows: The size of the energy required by the strong electromagnetic system in the transient working process is obtained by time domain integration of the product of the output side voltage and current of the super capacitor as a pulse power supply, and is as follows: （9） wherein , respectively represent the starting and stopping time of the strong electromagnetic system; u(t) is the voltage on the output side of the pulse power supply; i(t) is the current on the output side of the pulse power supply.

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