A Modeling Method Based on High-Voltage-Ratio Coupled Inductor DC-DC

Abstract

The present invention claims protection for a modeling method based on a high turns ratio coupled inductor DC-DC. This method includes considerations of the influence of leakage inductance and right half-plane zeros in the precise analysis of high turns ratio coupled inductor DC-DC circuits. The coupled inductor boost converter can achieve high gain, or small input current ripple, and a high recovery rate of the energy of the leakage magnetic inductance. Three states of the circuit are selected for analysis under the dual criteria of accuracy and complexity. In the dynamic analysis of the mutual inductance coupled high turns ratio circuit, a model considering the leakage inductance in the primary of the high turns ratio coupled inductor circuit is used for modeling, and the analytical expressions of the DC turns ratio and the small-signal transfer function are obtained to simplify the design of the control part.

Description

Technical Field

[0001] The present invention belongs to the technical field of switching power supply DC boost converters, and relates to a modeling method based on a high turns ratio coupled inductor DC-DC. Background Art

[0002] Due to the impact of conventional fossil fuels on the environment, the development of renewable energy that can be reused has been put on the agenda. Whether it is a photovoltaic system or a wind energy system, their output DC voltages are relatively low, and a DC-DC system with a high turns ratio is required to meet the needs of the subsequent stage. There are many types of boost converters that achieve a high turns ratio. Among them, although the traditional boost converter has advantages such as simple structure and high efficiency, when a high-gain converter is required in practical applications, the traditional boost converter can only achieve high gain through an extreme duty cycle, which will bring out many other problems at this time, such as the lower the efficiency as the duty cycle increases. And the traditional Boost DC converter belongs to a non-linear system and exhibits a non-minimum phase phenomenon. The state variables in the system affect each other, and it becomes extremely difficult to design the control circuit to maintain a stable output in the face of input interference. Therefore, in order to meet the growing demand for high gain of converters, many different boost technologies have been derived based on the traditional boost converter. Among them, the mutual inductance coupled high turns ratio circuit has received attention from researchers because of its few components, high turns ratio, adjustable turns ratio through coil windings, small switching tube stress after adding an active or passive absorption circuit, and the leakage inductance can be used to provide soft switching and high efficiency.

[0003] The research on the mutual inductance coupled high turns ratio circuit is relatively extensive. However, due to the complexity brought by the introduction of leakage inductance analysis, either the leakage inductance is ignored or only one side of the leakage inductance is considered during steady-state analysis, such as considering the primary leakage inductance or the secondary leakage inductance, while ignoring the current on the ideal transformer, so as to obtain an approximate turns ratio expression from control to output; although some circuit analyses consider the leakage inductance of both the primary and secondary sides and the current on the ideal transformer, only implicit equations are obtained and can only be solved numerically. For the dynamic analysis of the mutual inductance coupled high turns ratio circuit, like the steady-state analysis, in order not to be too complex to analyze, it is usually assumed to be fully coupled and analyzed without leakage inductance; although many circuits consider the leakage inductance, the simplified working state makes the influence of the leakage inductance invisible, and the leakage inductance will indeed reduce the turns ratio in the high turns ratio circuit; then some circuits consider all working states of the circuit and obtain a very accurate model, but it is difficult to write the expression of the transfer function and can only be used for digital analysis. The influence of the leakage inductance is replaced by a resistor, and the resistor is estimated using the DC turns ratio. However, when the turns ratio is small, the difference between this turns ratio and the actual situation is relatively large. By using a model that considers the leakage inductance in the primary of the high turns ratio coupled inductor circuit for modeling analysis, the influence and analysis expression of the leakage inductance can be obtained, and it will not be too simplified so that the influence of the leakage inductance cannot be seen. Summary of the Invention

[0004] The present invention aims to solve the problems of the above prior art, and proposes a modeling method based on a high turns-ratio coupled inductor DC-DC. The technical solution of the present invention is as follows:

[0005] A modeling method based on a high turns-ratio coupled inductor DC-DC includes the following steps:

[0006] Obtain four states of the coupled inductor dual-boost converter. The four states are respectively: Figure 1 (b) For state 1, switch S is closed, diode D1 is reverse-biased, diode D2 is forward-biased, the inductor current decreases, and the inductor current increases until it decreases to 0; Figure 1 (c) For state 2, at this time switch S is still closed, but both diode D1 and diode D2 are reverse-biased, the input voltage charges the magnetizing inductor, and capacitor C2 discharges to the load Ro; Figure 1 (d) For state 3, switch S is now open, both diode D1 and diode D2 are forward-biased, the inductor current decreases, and the inductor current increases until it decreases to 0; Figure 1 (e) For state 4, the switch is still open, but at this time diode D1 is reverse-biased and diode D2 is forward-biased. At this time, part of the energy stored in inductor Ls charges C2, and part of it charges the load Ro. The discharge forms a closed-loop circuit. Select states 2, 3, and 4 for analysis;

[0007] Conduct steady-state analysis and small-signal analysis on the coupled inductor dual-boost converter circuit;

[0008] Adopt the topology of the coupled inductor boost DC converter to eliminate the influence of the negative regulation phenomenon caused by the right-half plane zero point of the boost topology;

[0009] In the dynamic analysis of the mutual inductance-coupled high turns-ratio circuit, a model considering the leakage inductance in the primary of the high turns-ratio coupled inductor circuit is used for modeling, and the analytical expressions of the DC turns-ratio and the small-signal transfer function are obtained.

[0010] Further, for the step of obtaining the four states of the coupled inductor dual-boost converter and selecting states 2, 3, and 4 for analysis, it specifically includes:

[0011] Conduct steady-state analysis on the high turns-ratio coupled inductor DC converter. Assume that the time of state 1 is very short. When conducting circuit steady-state analysis, only consider states 2, 3, and 4. It is analyzed that the current of the leakage inductance is zero for a period of time. Therefore, the small ripple approximation is not applicable to the analysis of the leakage inductance. Assume that the ripple of the magnetizing inductor is very small, and take the average value of the state equation of the expression containing the leakage inductance current to obtain the average model as follows:

[0012]

[0013] T S and τ(1) represent the circuit switching period and the time constant respectively

[0014] Taking the average value of the capacitor current and inductor voltage over three periods, we get

[0015]

[0016] represents the derivative of voltage, c 1 represents the primary capacitor, c 2 represents the output capacitor, i Lk represents the leakage inductance current, i Lm represents the magnetizing inductance current, n represents the equivalent transformer turns ratio, d represents the duty cycle, V 0 represents the output voltage, R 0 represents the output resistance. L k represents the leakage inductance, k represents the inductance coefficient, V i represents the input voltage, V 1 represents the primary capacitor voltage.

[0017] Where Let the right - hand sides of equations (2) and (3) be zero, and we get the steady - state values:

[0018]

[0019] When k = 1: The DC transformation ratio expression (8) from input to output under steady - state analysis in the high - turns - ratio coupled - inductor boost converter circuit can be obtained.

[0020]

[0021] Furthermore, after establishing the large - signal model of the coupled - inductor dual - boost converter; introducing circuit losses into the established average circuit, we get the transfer function expression from control to output under small - signal analysis:

[0022] Simplify the expression and substitute into the small - signal model; Lm is the magnetizing inductance, Lk is the leakage inductance, and thus the transfer function can be obtained

[0023]

[0024] Where:

[0025] a 0 =(k - 1)R o (n + 1)(1 - d) 2 [2nk+(d + n - dn)(k - 1)]Vi

[0026] a 1 = 2(1 - d) 2 I Lm R o L k (n + 1)n

[0027] a 2 = nk(k - 1)L k R 0 c 1 (n + 1)(2n - 2nd + d)

[0028]

[0029] b 3 = L k 2 c 1 kn 2 (n + 1)

[0030] b 2 = c 1 [k + d 2 (n + 1)(1 - k) + (1 - 2d)(1 + n - k n )] + c 2 {1 + (1 + n)[d 2 (1 - k) + k(1 + 2n - 2nd) - 2d]}

[0031] b 1 = L k (n + 1)[d 2 (1 - k) + (1 - 2d) + k(n + 2) - 2dk]

[0032] b 0 = 2R 0 (1 - k)[1 - 3d + d 2 (3 - d)](15).

[0033] Furthermore, it also includes controlling the following specific transfer functions to the output:

[0034]

[0035] Further, it also includes the steps of establishing a transformer model, specifically including: analyzing an ideal transformer, magnetizing inductance, leakage inductance of the transformer model, adding winding resistance and parasitic capacitance; the mutual inductance between two coupled inductors of the transformer; assuming that part of the current flowing through the primary winding also flows through the secondary winding; this will generate: the magnetic flux linkage in the primary winding conductor, generating internal self-inductance; the magnetic flux linkage only linking with the primary winding, generating external self-inductance; the magnetic flux linkage linking with the secondary winding, generating mutual inductance; the coupling coefficient is a measure of the magnetic coupling degree between two sets of coils, with a range of 0 ≤ k ≤ 1; when k = 1, it is an ideal situation where the magnetic flux does not link with another winding, so when the coupling coefficient k < 1; the leakage magnetic flux stores energy, and its characteristics are similar to those of an inductor, and this effect can be modeled by a leakage inductance connected in series with the winding; when the magnetizing inductance approaches infinity, the transformer can be regarded as an ideal transformer.

[0036] Further, it also includes the steps of modeling the converter using the state-space averaging method: calculating the small-signal model of the circuit and solving the transfer function formula (15) of the circuit output voltage with respect to the duty cycle; according to theoretical analysis, the parameters of the converter are designed as: D = 0.5, Lk = 5 μH, Lm = 100 μH, C1 = C2 = 5 μF, Vi = 30 V, Ro = 400 Ω. Where D is the duty cycle, Lk is the leakage inductance, Lm is the magnetizing inductance, C1 is the primary capacitor, C2 is the output capacitor, Vi is the input voltage, and Ro is the load resistance.

[0037] The advantages and beneficial effects of the present invention are as follows:

[0038] 1. The innovation of the present invention is mainly the cooperation of the steps in claims 2 and 5, which can achieve the reliability of higher gain of the circuit. Among them, the steps in claim 5 are not easy to think of, and its advantages include that it can more accurately equivalent the influence of the magnetizing inductance. The ingenuity of claim 5 in establishing an equivalent model for the circuit lies in using an ideal transformer to simplify the analysis of the leakage inductance. The modeling and analysis method for the primary leakage inductance of the circuit and the main states 2, 3, and 4 can more flexibly achieve high voltage gain, and more clearly show the interaction between various components of the circuit. Through the modeling and analysis of the non-isolated coupled inductor boost circuit, the reliability of the circuit to achieve high gain can be increased.

[0039] 2. The innovation of the present invention is mainly the cooperation of the steps in claims 1 and 3. The modeling method can achieve accurate analysis without redundant parts. Among them, it is not easy to think of judging whether there is a right-half plane zero according to the analysis result in claim 1, and its advantages include that it can more accurately judge the system stability, judge the phase shift situation, and determine the design parameters of the next part of the circuit compensator. The ingenuity of claim 3 lies in obtaining the specific small-signal transfer functions of states 2, 3, and 4.

[0040] 3. The innovation of the present invention mainly lies in the cooperation of claim 4 and claim 6. The software Matlab is used to simulate the small-signal transfer function model of the circuit. In claim 6, the state-space averaging method is used to model the converter circuit, and its advantages include being able to obtain the average value in a fluctuating circuit, which is convenient for circuit analysis. Among them, by analyzing the influence of the leakage inductance of the coupled inductor in circuit states 2, 3, and 4, after establishing a relatively accurate model, the transfer function from control to output can be obtained through the Matlab software according to the model. Compared with the analysis method that can only obtain an implicit equation for digital solution after establishing an accurate model. The research method considering the high-ratio coupled inductor DC-DC modeling in states 2, 3, and 4 can write a specific and accurate expression of the transfer function from control to output. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. is the circuit topology structure diagram of the high-ratio coupled inductor DC-DC modeling analysis circuit provided by the preferred embodiment of the present invention;

[0042] Figure 2 FIG. is the input-output DC transformation ratio diagram when the primary leakage inductance is small;

[0043] Figure 3 FIG. is the input-output DC transformation ratio diagram when the primary leakage inductance is large;

[0044] Figure 4 FIG. is the Bode diagram of the transfer function from control to output in the AC small-signal analysis when the primary leakage inductance is small.

[0045] Figure 5 FIG. is the Bode diagram of the transfer function from control to output in the AC small-signal analysis when the primary leakage inductance is large. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and detailedly described in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention.

[0047] The technical solution of the present invention to solve the above technical problems is:

[0048] A research method based on high-ratio coupled inductor DC-DC modeling, which includes the following steps:

[0049] This method analyzes four states of the coupled-inductor dual-boost converter, selects three of them for analysis, conducts specific steady-state analysis or small-signal analysis on the circuit, outlines the assumptions applied in the circuit analysis of the coupled-inductor boost converter circuit, and uses the topology of the coupled-inductor boost DC converter to eliminate the influence of the negative regulation phenomenon caused by the right-half-plane zero in the boost topology; obtains the analytical expressions of the DC voltage gain and the small-signal transfer function, and simplifies the design of the control part.

[0050] Preferably, the analysis of the DC voltage gain and the small-signal transfer function of the mutual-inductance coupled dual-boost converter specifically includes the following steps:

[0051] Step 1: Conduct steady-state analysis on the high-voltage-gain coupled-inductor DC converter. Assuming that the time of State 1 is very short, when we conduct circuit steady-state analysis, we only consider State 2, State 3, and State 4. It is analyzed that the current of the leakage inductance is zero for a period of time. Therefore, the small-ripple approximation is not applicable to the analysis of the leakage inductance. Assuming that the ripple of the magnetizing inductance is very small, the average model is obtained by taking the average value of the state equations of the expressions containing the leakage inductance current as follows:

[0052]

[0053] Taking the average value of the capacitor current and the inductor voltage for the three periods, we get

[0054]

[0055] where Let the right-hand sides of equations (2) and (3) be zero to obtain the steady-state values:

[0056]

[0057] When k = 1: The DC voltage gain expression (8) from the input to the output under steady-state analysis in the high-voltage-gain coupled-inductor boost converter circuit can be obtained.

[0058]

[0059] Step 2: Conduct small-signal analysis on the high turns-ratio coupled-inductor DC-DC converter. Considering the complexity and accuracy of the analysis, when it is possible to obtain the specific transfer function, a more accurate analysis of the circuit is selected. At the same time, analyzing the four states of the converter will lead to overly complex analysis and it is difficult to obtain an intuitive transfer function expression. Considering the influence of the primary leakage inductance of the circuit in the case of three states, the equivalent circuit of the coupled-inductor dual-boost converter is obtained through the ideal transformer, the magnetizing inductance, and the leakage inductance. When analyzing the leakage inductance, the average value of the state equation of the leakage inductance current is obtained to get the average model, thus avoiding the inaccuracy of the small-ripple approximation analysis due to the leakage inductance current being zero for a period of time. At the same time, the specific transfer function from control to output can be obtained as follows:

[0060]

[0061] A research method based on high turns-ratio coupled-inductor DC-DC modeling, which includes the following steps:

[0062] Before modeling the circuit, first analyze the role of components in the circuit topology. When the magnetic coupling boost technology is applied, the output voltage provides energy when the switch is closed. In the circuit topology, the coupled inductor is used as the boost inductor. In the forward path of energy transfer, the coupled inductor is not only charged but also provides energy to the load. The energy provided by the coupled inductor to the load in the forward path increases the voltage gain. This enables the DC converter circuit not to use a large duty cycle to obtain a higher output voltage in applications with large voltage and high frequency conversion ratios. The method of eliminating the right-half plane zero by the coupled inductor does not complicate the circuit topology of the DC converter. When adjusting the value of the output voltage, the relatively traditional voltage control method can also be used to analyze the state-space average model of the DC converter.

[0063] Furthermore, find a suitable derivation method to purposefully design the performance of the converter: Inductors, capacitors, diodes, and coupled inductors are essential basic elements for forming a high-gain converter. By separately analyzing the essential role of each basic power electronic component in the boost converter, these components can be utilized reasonably and effectively. Summarize and generalize the existing boost technologies. Based on the existing high-gain topologies and integrating various boost technologies, propose some new high-gain DC converters. Combine the role of each device in the high-gain DC converter circuit and propose a new type of high-gain DC converter with coupled inductors according to the desired performance.

[0064] Furthermore, a transformer model is established, which consists of an ideal transformer, magnetizing inductance, leakage inductance, etc. The winding resistance and parasitic capacitance are added for analysis as appropriate. The mutual inductance between the two coupled inductors of the transformer. Assume that part of the current flowing through the primary winding also flows through the secondary winding. This will generate: the magnetic flux linkage in the primary winding conductor, generating internal self-inductance; the magnetic flux linkage only linked to the primary winding, generating external self-inductance; the magnetic flux linkage linked to the secondary winding, generating mutual inductance. The coupling coefficient is a measure of the magnetic coupling degree between two sets of coils, and its range is 0 ≤ k ≤ 1. When k = 1, it is an ideal situation. The magnetic flux does not link to another winding, so when the coupling coefficient k < 1. The leakage magnetic flux stores energy, and its characteristics are similar to those of an inductor. This effect can be modeled by a leakage inductance connected in series with the winding. When the magnetizing inductance approaches infinity, the transformer can be regarded as an ideal transformer.

[0065] Furthermore, a steady-state analysis is carried out on the novel coupled-inductor high-gain DC converter. Through analysis and calculation, the device stress relationship of the converter under steady state is obtained, the conditions for the converter to operate in the critical conduction state are analyzed, the changes in the performance of the converter under parasitic parameters are analyzed, and the parameters that have a greater impact on the voltage gain and efficiency of the converter are summarized, providing a theoretical basis for subsequent control-simulation and experiments.

[0066] Furthermore, the converter is modeled using the state-space averaging method. The small-signal model of the circuit is analyzed and calculated through mathematical software, and the transfer function of the circuit output voltage with respect to the duty cycle is solved. According to the theoretical analysis, the parameters of the converter are designed, and other auxiliary circuits used in the experiment are also designed. The open-loop experimental results verify the correctness of the steady-state theoretical analysis, and the closed-loop experimental results verify the effectiveness of the control of the high-gain DC converter.

[0067] 1. As shown in Figure 2 and Figure 3, to further illustrate that the method of the present invention has a relatively significant improvement in the accuracy performance to a certain extent, first, a steady-state analysis is carried out on the high-ratio coupled-inductor DC-DC, and then simulation experiments are carried out assuming different leakage inductance values.

[0068] A. Assume that the time of the first interval is very short, and only three circuit states are considered when performing the steady-state analysis of the circuit. It is analyzed that the current of the leakage inductance is zero for a period of time, so the small-ripple approximation is not applicable to the analysis of the leakage inductance. In this paper, it is assumed that the ripple of the magnetizing inductance is very small, and the average model is obtained by averaging the state equation of the expression containing the leakage inductance current as follows:

[0069]

[0070] Let the differential of the above formula be zero, and the following can be obtained at steady state:

[0071]

[0072] B. According to the equations written in columns, the corresponding output voltage values are obtained for different leakage inductance values. In the experiment, a comparison diagram of the DC turns ratio is obtained when the leakage inductance is 0.5 uH and 10 uH. Compared with the method of the present invention is the method of analyzing the four states of the circuit and the method of equivalent resistance influence of the leakage inductance. It can be seen from Figure 2 and Figure 3 that the modeling of the method of the present invention represented by the circles is more accurate in the case of small leakage inductance.

[0073] 2. Combine Figure 4 and Figure 5 to illustrate that in order to further illustrate the superiority of the method of the present invention in small-signal analysis.

[0074] A. After establishing the large-signal model of the coupled-inductor dual-boost converter; introducing circuit losses into the established average circuit, simulation and experimental measurements verify the accuracy of its large-signal model in studying the voltage conversion ratio, transient response, and frequency-domain response of the converter. Sort out the transfer function expression from control to output under small-signal analysis obtained by Matlab:

[0075] Simplify the expression and substitute into the small-signal model; thus, the transfer function

[0076]

[0077] where:

[0078] a 0 =(k - 1)R o (n + 1)(1 - d) 2 [2nk+(d + n - dn)(k - 1)]V i

[0079] a 1 =2(1 - d) 2 I Lm R o L k (n + 1)n

[0080] a 2 =nk(k - 1)L k R 0 c 1 (n + 1)(2n - 2nd + d)

[0081]

[0082] b 3 =L k 2 c 1 kn 2 (n + 1)

[0083] b 2 =c 1[k + d 2 (n + 1)(1 - k)+(1 - 2d)(1 + n - k n )]+c 2 {1+(1 + n)[d 2 (1 - k)+k(1 + 2n - 2nd)-2d]}

[0084] b 1 = L k (n + 1)[d 2 (1 - k)+(1 - 2d)+k(n + 2)-2dk]

[0085] b 0 = 2R 0 (1 - k)[1 - 3d + d 2 (3 - d)] (15)

[0087] B. Now, the small - signal model obtained by analyzing the method of the present invention is compared with the small - signal models for analyzing four circuit states and the small - signal model that models the energy loss of the leakage inductance with a variable resistor through Matlab simulation software. It can be seen from the circles in Figure 4 and Figure 5 representing the method of the present invention that the method of the present invention has better accuracy.

[0088] The systems, devices, modules or units illustrated in the above embodiments can be specifically implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, the computer can be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0089] A computer-readable medium includes both permanent and non-permanent, removable and non-removable media and can implement information storage by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer-readable medium does not include transitory computer-readable media such as modulated data signals and carrier waves.

[0090] It should also be noted that the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the element.

[0091] The above embodiments should be understood as being only for illustrative purposes of the present invention and not for limiting the protection scope of the present invention. After reading the content described in the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A modeling method for a high-ratio coupled inductor DC-DC, characterized in that, it includes the following steps: Obtain four states of the coupled inductor dual-boost converter. The four states are as follows: State 1: The switch S is closed, the diode D1 is reverse-biased, the diode D2 is forward-biased, the inductor current decreases, the inductor current increases until it decreases to 0; State 2: At this time, the switch S is still closed, but both the diode D1 and the diode D2 are reverse-biased, the input voltage charges the excitation inductor, and the capacitor C2 discharges to the load Ro; State 3: The switch S is now open, both the diode D1 and the diode D2 are forward-biased, the inductor current decreases, the inductor current increases until it decreases to 0; State 4: The switch is still open, but at this time the diode D1 is reverse-biased and the diode D2 is forward-biased. At this time, part of the energy stored in the inductor Ls charges C2 and part charges the load Ro, and the discharge forms a closed-loop circuit. Select States 2, 3, and 4 for analysis; Conduct steady-state analysis and small-signal analysis on the coupled inductor dual-boost converter circuit; Adopt the topological structure of the coupled inductor boost DC converter to eliminate the influence of the negative regulation phenomenon caused by the right-half plane zero point of the boost topology; In the dynamic analysis of the mutual inductance coupled high-ratio circuit, a model considering the leakage inductance in the primary of the high-ratio coupled inductor circuit is used for modeling, and the analytical expressions of the DC ratio and the small-signal transfer function are obtained.

2. A modeling method for a high-ratio coupled inductor DC-DC according to claim 1, characterized in that, for the step of obtaining the four states of the coupled inductor dual-boost converter and selecting States 2, 3, and 4 for analysis, specifically includes: Conduct steady-state analysis on the high-ratio coupled inductor DC converter. Assume that the time of State 1 is very short. When conducting circuit steady-state analysis, only consider States 2, 3, and 4. It is analyzed that the current of the leakage inductance is zero for a period of time. Therefore, the small ripple approximation is not applicable to the analysis of the leakage inductance. Assume that the ripple of the excitation inductance is very small, and the average value of the state equation including the expression of the leakage inductance current is obtained as the average model as follows: where T s , τ(1) represent the circuit switching period and the time constant respectively; For the capacitor current and inductor voltage in the three periods, the average value is obtained, and, Denotes the derivative of voltage, c 1 Denotes the primary capacitor, c 2 Denotes the output capacitor, i Lk Denotes the leakage inductance current i Lm represents the derivative state value of the exciting inductance current, n represents the turns ratio of the equivalent transformer, d represents the duty cycle, V 0 represents the output voltage, R 0 represents the output resistance, L k represents the leakage inductance, k represents the inductance coefficient, V i represents the input voltage, V c1 represents the primary capacitor voltage; Among them Let the right-hand sides of equations (2) and (3) be zero to obtain the steady-state values: When k = 1: The DC ratio expression (8) from input to output under steady-state analysis in the high-ratio coupled inductor boost converter circuit can be obtained 3. A modeling method for a high-ratio coupled inductor DC-DC according to claim 2, characterized in that, After establishing the large-signal model of the coupled inductor dual-boost converter; introduce circuit losses into the established average circuit to obtain the transfer function expression from control to output under small-signal analysis: The simplified expression substitutes into the small-signal model; L m is the exciting inductance, and L k is the leakage inductance, from which the transfer function can be obtained Where: a 0 =(k - 1)R o (n + 1)(1 - d) 2 [2nk+(d + n - dn)(k - 1)]V i a 1 = 2(1 - d) 2 I Lm R o L k (n + 1)n a 2 = nk(k - 1)L k R 0 c 1 (n + 1)(2n - 2nd + d) b 3 = L k 2 c 1 kn 2 (n + 1) b 2 = c 1 [k + d 2 (n + 1)(1 - k)+(1 - 2d)(1 + n - k n )]+ c 2 {1+(1 + n)[d 2 (1 - k)+k(1 + 2n - 2nd)-2d]} b 1 = L k (n + 1)[d 2 (1 - k)+(1 - 2d)+k(n + 2)-2dk] b 0 = 2R 0 (1 - k)[1 - 3d + d 2 (3 - d)](15).

4. A modeling method for a high-ratio coupled inductor DC-DC according to claim 3, characterized in that, It also includes the specific transfer function from control to output as follows: D is the duty cycle.

5. A modeling method for a high-ratio coupled inductor DC-DC according to claim 2, characterized in that, It also includes the steps of establishing a transformer model, specifically including: the transformer model includes an ideal transformer, a magnetization inductance, and a leakage inductance, and the winding resistance and parasitic capacitance are added for analysis; the mutual inductance between the two coupled inductors of the transformer; assuming that part of the current flowing through the primary winding also flows through the secondary winding; this will generate: the magnetic flux linkage in the primary winding conductor, generating internal self-inductance; the magnetic flux linkage that only links with the primary winding, generating external self-inductance; the magnetic flux linkage that links with the secondary winding, generating mutual inductance; the coupling coefficient is a measure of the degree of magnetic coupling between two sets of coils, with a range of 0 ≤ k ≤ 1; when k = 1, it is an ideal situation where the magnetic flux does not link with the other winding, so when the coupling coefficient k < 1; the leakage magnetic flux stores energy, and its characteristics are similar to those of an inductor, and this effect can be modeled with a leakage inductance connected in series with the winding; when the magnetization inductance approaches infinity, the transformer can be regarded as an ideal transformer.

6. A modeling method based on a high turns ratio coupled inductor DC-DC according to claim 3, characterized in that It also includes the steps of modeling the converter using the state - space averaging method: calculating the small - signal model of the circuit and solving the transfer function formula (15) of the circuit output voltage with respect to the duty cycle; according to the theoretical analysis, the parameters of the converter are designed: D = 0.5, L k = 5 μH, L m = 100 μH, c 1 = c 2 = 5 μF, V i = 30 V, R o = 400 Ω, where D is the duty cycle, L k is the leakage inductance, L m is the magnetizing inductance, c 1 is the primary capacitor, c 2 is the output capacitor, V i is the input voltage, R o is the load resistance.

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