Parameter optimization method and system for resonant converter of electric vertical take-off and landing aircraft

Abstract

The invention provides a resonant converter parameter optimization method and system of an electric vertical take-off and landing aircraft, and relates to the technical field of aviation power electronics. The method comprises the following steps: constructing an improved equivalent circuit model containing transformer secondary side leakage inductance; deriving a voltage gain function expression of the improved equivalent circuit model and an optimization calculation formula of the excitation inductance required for realizing the soft switching; parameter optimization is carried out based on the voltage gain function expression and the excitation inductance optimization calculation formula; and building an LLC resonant converter experimental prototype according to the optimized parameters, and carrying out system verification and performance evaluation. According to the invention, the problem of performance reduction caused by neglecting secondary side leakage inductance under a high-frequency working condition in a traditional design is solved, the efficiency, the voltage stabilization precision and the power density of the converter are remarkably improved, and the high requirement of eVTOL on an airborne power supply is met.

Description

Technical Field

[0001] This invention relates to the field of aviation power electronics technology, specifically to a method and system for optimizing the parameters of a resonant converter in an electric vertical takeoff and landing aircraft. Background Technology

[0002] Electric vertical take-off and landing (eVTOL) aircraft, as a key carrier of future urban air mobility, place extremely stringent requirements on the power density, efficiency, and reliability of their onboard propulsion systems. eVTOL propulsion systems typically utilize multi-voltage DC buses (such as 540V, 800V, or even higher) for power supply, necessitating high-efficiency DC / DC converters to provide a stable 28V low-voltage power supply to the flight control system, avionics, and auxiliary power unit. LLC resonant converters, due to their ability to achieve zero-voltage switching of the primary-side switches and zero-current switching of the secondary-side rectifiers, offer advantages such as high efficiency, high power density, and low electromagnetic interference, making them an ideal choice for such applications.

[0003] To maximize power density and reduce weight (crucial for the range and payload of eVTOLs), increasing the operating frequency of LLC resonant converters to the megahertz level to reduce the size of passive components (especially magnetic components) has become an inevitable trend. However, with the significant increase in frequency, the parasitic parameters of the transformer, especially the secondary leakage inductance, become significant. Traditional LLC resonant converter design and parameter calculations are typically based on an ideal transformer model, neglecting the secondary leakage inductance. Under the high-frequency, high-power conditions of eVTOL applications, the secondary leakage inductance significantly alters the equivalent parameters of the resonant cavity, leading to: 1) The actual voltage gain curve deviates from the design expectation, affecting the voltage regulation accuracy over a wide input voltage range (such as in response to battery voltage fluctuations) or during startup. 2) The soft switching condition is disrupted, leading to a sharp increase in switching losses, a decrease in efficiency, and serious heat dissipation problems at high power, threatening flight safety; 3) The introduction of additional circulating losses further reduces system efficiency and shortens the battery life.

[0004] Therefore, to address the problems of inaccurate models, performance degradation, and insufficient reliability caused by neglecting the leakage inductance of the transformer secondary side when applying existing LLC resonant converter design methods to high-demand scenarios such as eVTOL, this paper provides an LLC resonant converter parameter design method and system that can accurately model and optimize the influence of transformer secondary side leakage inductance, so as to meet the high power requirements of eVTOL energy and power systems for airborne power. Summary of the Invention

[0005] To address the technical problems of inaccurate models, degraded performance, and insufficient reliability caused by neglecting the leakage inductance of the transformer secondary side in the design of existing LLC resonant converters for electric vertical takeoff and landing (eVTOL) aircraft, this invention proposes a method and system for optimizing LLC resonant converter parameters considering the leakage inductance of the transformer secondary side in the eVTOL power system, thereby meeting the stringent requirements of the eVTOL power system for airborne power.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for optimizing the parameters of a resonant converter in an electric vertical takeoff and landing (EVTOL) aircraft, the method comprising: Construct an improved equivalent circuit model containing the leakage inductance of the transformer secondary side; The voltage gain amplitude function expression and the high-frequency and low-frequency resonant point expressions of the improved equivalent circuit model are derived. Based on the voltage gain amplitude function expression and the high-frequency resonant point expression, the magnetizing inductance required for soft switching is derived. L m,lks The optimized calculation formula; Based on the voltage gain amplitude function expression and the magnetizing inductance L m,lks The parameters are optimized using the optimized calculation formula; An experimental prototype of the LLC resonant converter was built based on the optimized parameters for system verification and performance evaluation.

[0007] On the other hand, the present invention also provides a resonant converter parameter optimization system for an electric vertical takeoff and landing aircraft. The system includes a memory for storing computer program instructions and a processor for executing the program instructions. When the computer program instructions are executed by the processor, the system is triggered to execute the above-described resonant converter parameter optimization method for an electric vertical takeoff and landing aircraft.

[0008] Compared with the prior art, the beneficial effects of the present invention are: 1. Improved efficiency: By accurately considering the influence of leakage inductance on the secondary side of the transformer, the parameter design of the LLC resonant converter was optimized, enabling the converter to maintain high-efficiency energy conversion under high-frequency and high-power conditions. Experimental verification shows that the overall efficiency can reach more than 95%, significantly reducing switching losses and heat dissipation.

[0009] 2. Enhanced voltage regulation accuracy: A voltage gain expression including secondary leakage inductance parameters was derived, enabling the resonant converter to maintain a stable voltage output under different input voltage ranges and load variations, thereby improving the system's voltage regulation accuracy.

[0010] 3. Improved power density: By optimizing key parameters of the resonant cavity, the size of passive components (especially magnetic components) has been reduced, thereby improving power density while maintaining high efficiency, which is crucial for the range and payload of eVTOL.

[0011] 4. Enhanced reliability: The impact of secondary leakage inductance on soft-switching conditions was considered, and the calculation of the magnetizing inductance for achieving zero-voltage switching (ZVS) was optimized. This avoids the loss of soft-switching characteristics caused by secondary leakage inductance under high-frequency operating conditions, thereby reducing switching losses, enhancing system reliability, and ensuring flight safety.

[0012] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0013] Figure 1 This is a flowchart of the resonant converter parameter optimization method for an electric vertical takeoff and landing aircraft according to the present invention; Figure 2 This is a diagram of an LLC circuit topology considering the leakage inductance of the transformer secondary side according to the present invention; Figure 3 This is the LLC equivalent circuit diagram of introducing leakage inductance on the secondary side of the transformer according to the present invention. Detailed Implementation

[0014] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings, so as to more clearly understand the purpose, features and advantages of this invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of this invention, but are only for illustrating the essential spirit of the technical solutions of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0015] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0016] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0017] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0018] In the following description, in order to clearly demonstrate the structure and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0019] The implementation details of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following content is only for the convenience of understanding the implementation details and is not necessary for implementing this solution.

[0020] With the rapid development of avionics technology, electric vertical takeoff and landing (eVTOL) aircraft, with their unique takeoff and landing methods and broad application prospects, are gradually becoming a key and highly anticipated vehicle in the future urban air mobility field. However, eVTOL places extremely stringent requirements on the airborne power system, especially in terms of power density, efficiency, and reliability. In the architecture of multi-voltage DC bus power supply for the propulsion system, the LLC resonant converter is an ideal choice for providing a stable low-voltage power supply for the flight control system, avionics, and auxiliary power unit, and its performance is crucial. However, in high-frequency, high-power eVTOL applications, the traditional LLC resonant converter design method, by neglecting the leakage inductance of the transformer secondary side, has led to a series of problems such as model inaccuracies, performance degradation, and insufficient reliability.

[0021] Against this backdrop, the present invention proposes a method and system for optimizing the parameters of the resonant converter of an electric vertical takeoff and landing (EVTOL) aircraft, aiming to effectively solve the aforementioned technical problems. The flowchart of the EVTOL resonant converter parameter optimization method is shown below. Figure 1 As shown, the specific content will be explained in detail below: S1. Establish an improved equivalent circuit model that considers the leakage inductance of the transformer secondary side.

[0022] like Figure 2 The diagram shows the circuit topology of an LLC resonant converter considering the leakage inductance of the transformer secondary side. It illustrates the overall circuit topology of the LLC resonant converter including the leakage inductance of the transformer secondary side, including the input power supply, primary-side switching network, resonant network, transformer, secondary-side rectifier network, and output load.

[0023] Specifically, the input power supply includes DC input power supply V. inIt is directly connected to both ends of the primary-side switching network to provide high-voltage DC power (such as 540V or 800V) to power the entire LLC resonant converter.

[0024] Primary-side switching network: Primary-side switches Q1 and Q2 are two MOSFETs or IGBTs forming a half-bridge structure, transferring energy through alternating conduction. The drain of Q1 is connected to the positive terminal of the input power supply, and its source is connected to the drain of Q2. The source of Q2 is connected to the negative terminal of the input power supply (reference ground). The midpoint A of the switches (the connection point between the source of Q1 and the drain of Q2) is connected through the resonant inductor L. r It is connected to the primary winding of the transformer. The switching transistor drive circuit generates complementary PWM signals, which are connected to the gates of Q1 and Q2 to control the alternating conduction of Q1 and Q2.

[0025] The resonant network includes the resonant inductor L r Its relationship with the resonant capacitor C r The series connections form a series resonant network, which determines the resonant frequency and characteristics of the converter. The resonant inductor L... r One end is connected to the midpoint of the primary-side switching transistor, and the other end is connected to the primary winding of the transformer. Resonant capacitor C r With L r After being connected in series to the primary winding of the transformer, it participates in the resonance process, affecting voltage gain and efficiency. Parallel magnetizing inductor L m Connected in parallel with a series resonant network, it reflects the excitation characteristics of the transformer, through L r C r and L m The resonance enables soft switching (ZVS / ZCS), reducing switching losses.

[0026] The transformer includes a primary winding N1, which receives energy from the resonant network and transfers it to the secondary winding via electromagnetic induction. One end of the primary winding N1 is connected to the resonant inductor L. r and resonant capacitor C r The other end is connected to the negative terminal of the input power supply (reference ground). The transformer secondary winding N... 21 N 22 It transfers energy to the secondary-side rectifier network, and also includes the secondary-side leakage inductance L. lks Transformer secondary winding N 21 One end is through the secondary leakage inductor L lks1 The anode of the secondary rectifier diode D1 is connected, and the other end is connected to the filter capacitor C. o Connect the cathode of the secondary rectifier diode D1. Transformer secondary winding N 22 One end is through the secondary leakage inductor L lks2 The anode of the secondary rectifier diode D2 is connected, and the other end is connected to the filter capacitor C. o Connect the cathode of the secondary rectifier diode D1. Secondary leakage inductance L lksThese are parasitic parameters of the transformer secondary winding, which affect voltage gain and soft-switching conditions under high-frequency operating conditions, and are connected in series between the secondary winding and the rectifier diode.

[0027] The secondary-side rectifier network and output load, including secondary-side rectifier diodes D1 and D2, form a full-wave rectifier circuit to convert AC voltage to DC voltage. The anode of D1 is connected to L... lks1 Secondary winding N 21 The cathode is connected to the output filter capacitor C. o Positive electrode. D2 anode passes through L lks2 Secondary winding N 22 The cathode is connected to the cathode of D1. Output filter capacitor C. o The positive terminal is connected to the cathode of D1, and the negative terminal is connected to the secondary winding N. 21 N 22 The midpoint is used to smooth the rectified DC voltage, providing a stable 28V low-voltage DC power supply to the load (such as powering a flight control system). Load resistance R L Parallel to the output filter capacitor C o Both ends can be actual loads such as flight control systems and avionics equipment.

[0028] In some embodiments, based on the fundamental frequency analysis method (a commonly used method in resonant converter analysis, whose core idea is to assume that only the fundamental frequency component can transmit power, ignoring the effects of other harmonics, and simplifying the circuit model by extracting and analyzing the fundamental frequency components of voltage and current, thereby deriving the gain expression and characteristics of the circuit), Figure 2 The actual circuit is constructed as an improved equivalent circuit model of an LLC resonant converter including the leakage inductance of the transformer secondary side, such as... Figure 3 As shown, the equivalent components are configured as follows: Series resonant network: consisting of resonant inductor L r and resonant capacitor C r The series connection determines the resonant frequency and characteristics of the converter.

[0029] Parallel magnetizing inductor: L m Connected in parallel with a series resonant network, it reflects the excitation characteristics of the transformer and is crucial for achieving zero-voltage switching (ZVS).

[0030] Leakage inductance and equivalent load: Leakage inductance on the secondary side of the transformer L lks When reduced to the original edge, its equivalent sense value is L' lks = n 2 L lks ,in nThe transformer turns ratio reflects the impact of secondary leakage inductance on the primary circuit; the leakage inductance is calculated. L' lks With equivalent load resistance R eq Series, equivalent load resistance R eq This reflects the actual load resistance. R L Its performance in the equivalent circuit, among which .

[0031] S2. Derive the voltage gain amplitude function and the expressions for high-frequency and low-frequency resonant points of the improved equivalent circuit model.

[0032] Based on the improved equivalent circuit model, the voltage gain amplitude function of the system is derived. M lks ( f n This function explicitly includes the secondary leakage inductance parameter. Simultaneously, it determines the high-frequency and low-frequency resonant points under the improved equivalent circuit model.

[0033] From input voltage V in (Fundamental RMS value) to reflected output voltage V po The gain function G(s) of the fundamental effective value is: in: For parallel branch impedance; Input impedance; s = jw , w =2 πf s , f s The switching frequency; Let the normalized frequency ,in It is the series resonant frequency.

[0034] Define parameter: Inductance ratio Quality factor Normalized secondary side leakage .

[0035] By substitution and simplification, the voltage gain amplitude function is obtained. M lks ( f n )=| G ( jw The display expression for )|: The LLC resonant converter has two resonant frequencies corresponding to high and low frequencies. f lr and f lh Furthermore, multiple operating regions can be divided according to frequency, allowing for the analysis of the ideal operating region and state of the LLC resonant converter. The corresponding expressions for the high-frequency and low-frequency resonant points are: , in, f lr This is the low-frequency resonant point. f lh This is the high-frequency resonant point.

[0036] in M lks ( f n The first term is the voltage gain expression for a traditional LLC resonant converter, reflecting the resonant cavity. L r C r L m The interaction with the load; the second term is the correction term introduced by the secondary leakage inductance, which manifests as the characteristics of a first-order low-pass filter. The gain decreases as the frequency increases, and the larger the secondary leakage inductance, the more obvious the high-frequency attenuation.

[0037] Using the voltage gain function, the influence of different secondary leakage inductance values ​​on the system voltage gain curve is analyzed to ensure sufficient voltage regulation capability under eVTOL operating conditions (such as input voltage range and load changes).

[0038] S3. Considering the leakage inductance of the transformer secondary side, derive the magnetizing inductance required to achieve ZVS. L m,lks The optimized calculation formula.

[0039] This paper analyzes the minimum magnetizing current required to achieve zero-voltage switching (ZVS) of the primary-side switching transistor of the transformer, and derives the magnetizing inductance required to achieve ZVS considering the secondary-side leakage inductance. L m,lks The optimized calculation formula ensures high efficiency and low heat dissipation even at high frequencies and high power. The minimum excitation current is crucial to ensure that the primary-side switch can completely draw away its junction capacitance (e.g., C) within the dead time. eqThe magnetizing current is used to charge the junction capacitance, thus achieving the critical condition for zero-voltage switching (ZVS). If the magnetizing current is insufficient, the switching transistor will not be able to complete the charging and discharging of the junction capacitance within the dead time, leading to hard switching, which causes increased switching losses and decreased efficiency. The derived L... m,lks The optimized calculation formula, based on secondary leakage inductance parameters, dead time, and switching transistor junction capacitance, calculates the excitation inductance value L that satisfies both the minimum excitation current requirement and the minimum loss. m,lks The optimized calculation formula is as follows: in t dlk This indicates the dead time considering secondary side leakage inductance; C eq This is the equivalent junction capacitance of the primary-side switching transistor.

[0040] The derivation process is as follows: After considering the secondary leakage inductance, the resonant cavity current is related to the voltage gain: ZVS conditional rewriting: Simplified, we get: To reduce the dead time required for soft-switching ZVS, select As L m,lks The optimized calculation formula.

[0041] S4. Voltage gain function based on improved equivalent circuit model and magnetizing inductance required to achieve ZVS L m,lks The optimized calculation formula is used for parameter optimization design.

[0042] When performing parameter optimization design based on the improved equivalent circuit model, the stringent requirements of the eVTOL airborne power system for high efficiency, high power density, and high reliability must be comprehensively considered. First, based on the voltage gain amplitude function derived in S2 that explicitly includes the secondary leakage inductance parameter, and the analysis results of the influence of the secondary leakage inductance on the soft-switching condition in S3, the optimization range of the key parameters of the resonant cavity is determined.

[0043] Specifically, by adjusting the resonant inductance L r Resonant capacitor C r And excitation inductance L mThe values ​​are precisely calculated to ensure that the resonant converter maintains efficient energy conversion and stable voltage output under the wide input voltage range of eVTOL (such as to cope with battery voltage fluctuations) and large load variations. Simultaneously, the minimum excitation current required to achieve zero-voltage switching (ZVS) is accurately calculated using optimized formulas, avoiding the loss of soft-switching characteristics due to secondary-side leakage inductance under high-frequency operating conditions, thereby reducing switching losses and heat dissipation and improving overall system efficiency. Finally, through a multi-objective optimization algorithm, the optimal combination of key resonant cavity parameters is determined while meeting system efficiency, power density, and reliability requirements.

[0044] S5. Based on the optimized parameters, build an LLC resonant converter prototype for system verification and performance evaluation.

[0045] An LLC resonant converter prototype was built based on the optimized parameters, and its performance under actual eVTOL conditions was verified through comprehensive testing. The tests included steady-state waveform analysis, voltage gain characteristic measurement, dynamic response evaluation, and overall efficiency testing.

[0046] Specifically, the output waveforms of the resonant converter under input voltage fluctuations and load surges were captured using an oscilloscope to verify its steady-state and dynamic voltage regulation capabilities. A network analyzer was used to measure the voltage gain curve, comparing the agreement between the theoretical model and experimental results to evaluate the accuracy of the improved model. Simultaneously, a power analyzer was used to test the overall efficiency, ensuring that it still meets design specifications (e.g., ≥95% efficiency) under high-frequency, high-power conditions. Furthermore, long-term continuous operation tests were conducted to monitor the temperature rise and heat dissipation performance of the resonant converter, verifying its reliability under extreme conditions. Finally, by comprehensively evaluating the experimental data, it was confirmed whether the optimized LLC resonant converter meets all design requirements of the eVTOL airborne power system, providing a reliable basis for subsequent engineering applications.

[0047] The present invention also provides a resonant converter parameter optimization system for an electric vertical takeoff and landing (EVTOL) aircraft. The system includes a memory for storing computer program instructions and a processor for executing the program instructions. When the computer program instructions are executed by the processor, the system is triggered to execute the aforementioned resonant converter parameter optimization method for EVTOL aircraft.

[0048] This invention proposes a method and system for optimizing the parameters of a resonant converter in an electric vertical takeoff and landing (eVTOL) aircraft. By constructing an improved equivalent circuit model including the secondary leakage inductance of the transformer, deriving an explicit voltage gain expression incorporating the secondary leakage inductance parameter, optimizing the calculation formula for the excitation inductance to achieve zero-voltage switching, and integrating the model and formulas for key parameter optimization design, as well as building an experimental prototype to verify actual performance, this invention solves the problems of efficiency degradation and insufficient reliability caused by neglecting the secondary leakage inductance in traditional LLC resonant converters in high-frequency, high-power eVTOL applications. It significantly improves the converter's efficiency, voltage regulation accuracy, and power density, meeting the high requirements of eVTOL for airborne power supplies.

[0049] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention. Such modifications or substitutions should all fall within the scope of the invention, or any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. A method for optimizing the parameters of a resonant converter in an electric vertical takeoff and landing (EVTOL) aircraft, characterized in that, The method includes: Construct an improved equivalent circuit model containing the leakage inductance of the transformer secondary side; The voltage gain amplitude function expression and the high-frequency and low-frequency resonant point expressions of the improved equivalent circuit model are derived. Based on the voltage gain amplitude function expression and the high-frequency resonant point expression, the magnetizing inductance required for soft switching is derived. L m,lks The optimized calculation formula; Based on the voltage gain amplitude function expression and the magnetizing inductance L m,lks The parameters are optimized using the optimized calculation formula; An experimental prototype of the LLC resonant converter was built based on the optimized parameters for system verification and performance evaluation.

2. The method according to claim 1, characterized in that, The construction of the improved equivalent circuit model including the leakage inductance of the transformer secondary side specifically includes: Based on the actual circuit of an LLC resonant converter with transformer secondary leakage inductance, an improved equivalent circuit model of the LLC resonant converter with transformer secondary leakage inductance is constructed based on the fundamental wave analysis method. The actual circuit of the LLC resonant converter with transformer secondary leakage inductance includes: input power supply, primary-side switching network, resonant network, transformer, secondary-side rectifier network and output load. The input power supply includes a DC input power supply V. in It is directly connected to both ends of the primary-side switching network to provide high-voltage DC power to power the entire LLC resonant converter; The primary-side switching network consists of two MOSFETs or IGBTs forming a half-bridge structure, with energy transfer achieved through alternating conduction. The drain of Q1 is connected to the positive terminal of the input power supply, and its source is connected to the drain of Q2. The source of Q2 is connected to the negative terminal of the input power supply. The midpoint A of the primary-side switching transistors is connected to the resonant inductor L. r Connected to the primary winding of the transformer; the switching transistor drive circuit generates complementary PWM signals, which are connected to the gates of Q1 and Q2 to control the alternating conduction of Q1 and Q2; The resonant network includes a resonant inductor L. r and the resonant capacitor C connected in series with it r Resonant inductor L r One end is connected to the midpoint of the primary-side switching transistor, and the other end is connected to the primary winding of the transformer; resonant capacitor C r With L r Connected in series to the primary winding of the transformer; connected in parallel to the magnetizing inductor L m With series resonant inductor L r Resonant capacitor C r in parallel; The transformer includes a primary winding N1, one end of which is connected to a resonant inductor L. r and resonant capacitor C r The other end is connected to the negative terminal of the input power supply at the series node; the secondary winding N of the transformer 21 N 22 It transfers energy to the secondary-side rectifier network, and also includes the secondary-side leakage inductance L. lks ; Transformer secondary winding N 21 One end is through the secondary leakage inductor L lks1 The anode of the secondary rectifier diode D1 is connected, and the other end is connected to the filter capacitor C. o The cathode of the secondary rectifier diode D1 is connected; the secondary winding N of the transformer... 22 One end is through the secondary leakage inductor L lks2 The anode of the secondary rectifier diode D2 is connected, and the other end is connected to the filter capacitor C. o The cathode of the secondary rectifier diode D1 is connected; the secondary leakage inductance L lks These are parasitic parameters of the transformer secondary winding, affecting voltage gain and soft-switching conditions, and are connected in series between the secondary winding and the rectifier diode. The secondary-side rectifier network and output load, including secondary-side rectifier diodes D1 and D2, form a full-wave rectifier circuit that converts AC voltage to DC voltage; the anode of D1 is connected to L... lks1 Secondary winding N 21 The cathode is connected to the output filter capacitor C. o Positive electrode; D2 anode through L lks2 Secondary winding N 22 Cathode connected to cathode D1; output filter capacitor C o The positive terminal is connected to the cathode of D1, and the negative terminal is connected to the secondary winding N. 21 N 22 Midpoint; Load resistance R L Parallel to the output filter capacitor C o Both ends.

3. The method according to claim 2, characterized in that, The improved equivalent circuit model of the LLC resonant converter, which includes the leakage inductance on the secondary side of the transformer, has the following equivalent component configuration: Series resonant network: consisting of resonant inductor L r and resonant capacitor C r The series connection determines the resonant frequency and characteristics of the converter; Parallel magnetizing inductor: L m Connected in parallel with a series resonant network, it reflects the excitation characteristics of the transformer and is used to achieve zero-voltage switching; Leakage inductance and equivalent load: Leakage inductance on the secondary side of the transformer L lks Returning to the original side, leakage inductance on the secondary side L lks The equivalent perceived value is L' lks = n 2 L lks ,in n Transformer turns ratio; leakage inductance calculation L' lks With equivalent load resistance R eq Series, equivalent load resistance R eq This reflects the actual load resistance. R L Its performance in the equivalent circuit, among which .

4. The method according to claim 3, characterized in that, The derivation of the voltage gain amplitude function expression for the improved equivalent circuit model specifically includes: Based on the improved equivalent circuit model, the voltage gain amplitude function of the system is derived. M lks ( f n This function explicitly includes the secondary leakage inductance parameter; from the input voltage V in To the reflected output voltage V po The gain function G(s) is: in: , is the impedance of the parallel branch; , where is the input impedance; s = jw , w =2 πf s , f s The switching frequency; Let the normalized frequency ,in It is the series resonant frequency; Define parameter: Inductance ratio Quality factor Normalized secondary side leakage ; By substitution and simplification, the voltage gain amplitude function is obtained. M lks ( f n )=| G ( jw The display expression for )|: 。 5. The method according to claim 4, characterized in that, The derivation of the high-frequency and low-frequency resonant point expressions for the improved equivalent circuit model specifically includes: the LLC resonant converter has two resonant frequencies corresponding to high and low frequencies. f lr and f lh Furthermore, multiple operating regions can be divided according to frequency, allowing for the analysis of the ideal operating region and state of the LLC resonant converter; the expressions for the high-frequency and low-frequency resonant points are as follows: ， In the formula, f lr This is the low-frequency resonant point. f lh This is the high-frequency resonant point.

6. The method according to claim 5, characterized in that, The derivation of the magnetizing inductor required for soft switching is based on the voltage gain amplitude function expression and the high-frequency resonant point expression. L m,lks The optimized calculation formula specifically includes: Based on the voltage gain amplitude function, high-frequency resonant point, dead time, and switching junction capacitance, L is derived. m,lks The optimized calculation formula satisfies both the minimum excitation current requirement and the minimum loss excitation inductance value, L. m,lks The optimized calculation formula is as follows: in t dlk This indicates the dead time considering secondary side leakage inductance; C eq This is the equivalent junction capacitance of the primary-side switching transistor.

7. The method according to claim 6, characterized in that, The L m,lks The derivation process of the optimization calculation formula is as follows: After considering the leakage inductance of the transformer secondary side, the resonant cavity current is related to the voltage gain: Soft-switching ZVS condition rewriting: After simplification, we get: To reduce the dead time required for soft-switching ZVS, select As L m,lks The optimized calculation formula.

8. The method according to claim 7, characterized in that, The expression based on voltage gain amplitude function and magnetizing inductance L m,lks The optimization calculation formula is used to optimize parameters, specifically including: Based on the voltage gain amplitude function explicitly including the transformer secondary leakage inductance parameters, and using the optimized calculation formula to calculate the minimum excitation current required to achieve zero-voltage switching, the resonant inductor L is adjusted. r Resonant capacitor C r And excitation inductance L m The values ​​ensure that the resonant converter can maintain efficient energy conversion and stable voltage output under the wide input voltage range and large load variation conditions of electric vertical take-off and landing aircraft.

9. The method according to claim 8, characterized in that, The process of building an LLC resonant converter prototype based on the optimized parameters and conducting system verification and performance evaluation specifically includes: The output waveforms of the LLC resonant converter under input voltage fluctuations and load surges were captured using an oscilloscope to verify its steady-state and dynamic voltage regulation capabilities. A network analyzer was used to measure the voltage gain curve, comparing the agreement between the theoretical model and experimental results to evaluate the accuracy of the improved model. Simultaneously, a power analyzer was used to test the overall efficiency, ensuring that it still meets design specifications under high-frequency, high-power conditions. Furthermore, long-term continuous operation tests were conducted to monitor the temperature rise and heat dissipation performance of the LLC resonant converter, verifying its reliability under extreme conditions. Finally, a comprehensive evaluation of the experimental data confirmed whether the optimized LLC resonant converter meets all design requirements of the electric vertical takeoff and landing (EVTOL) aircraft's onboard power system.

10. A resonant converter parameter optimization system for an electric vertical takeoff and landing (EVTOL) aircraft, the system comprising a memory for storing computer program instructions and a processor for executing the program instructions, wherein, When the computer program instructions are executed by the processor, the system is triggered to execute the resonant converter parameter optimization method for the electric vertical take-off and landing aircraft as described in any one of claims 1 to 9.

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