Evaluation method for primary equivalent parallel distributed capacitance of common-magnetic-core multi-winding coupling transformer

Abstract

The invention relates to a transformer winding equivalent distributed capacitance evaluation method, in particular to a common-magnetic-core multi-winding coupling transformer primary equivalent parallel distributed capacitance evaluation method, and solves the problem that the common-magnetic-core multi-winding coupling transformer primary equivalent parallel distributed capacitance in an existing high-voltage high-frequency LCC charging power supply is difficult to accurately evaluate. And the parameters of the parallel resonant capacitor of the power supply cannot be accurately designed. The method comprises the following steps: 1) establishing a common-magnetic-core multi-winding coupling transformer test circuit, and establishing an equivalent circuit model; 2) testing a change curve of the inductance of the single-turn winding of the magnetic core along with the test frequency to obtain the inductance of the single-turn winding; 3) testing the characteristic impedance curve of the primary winding to obtain a resonant frequency point; (4) primary sub-winding inductance under the working frequency is calculated; and 5) calculating the equivalent parallel distributed capacitance of the primary winding under the working frequency, and completing the evaluation of the primary equivalent parallel distributed capacitance of the common-magnetic-core multi-winding coupling transformer.

Description

Technical Field

[0001] The invention relates to a transformer winding equivalent distributed capacitance evaluation method, and in particular to a common magnetic core multi-winding coupling transformer primary equivalent parallel distributed capacitance evaluation method. Background Art

[0002] As the core device for power supply voltage conversion, high-frequency / pulse transformers are widely used in power systems, electronic science, household appliances, new energy vehicles, high-speed rail, ships and submarines, aerospace, weapons and equipment, etc. In order to improve the efficiency of voltage conversion and power transmission, transformers are usually composed of magnetic cores, primary windings and secondary windings. In the field of high-voltage and high-frequency series-parallel resonant (LCC) charging power supplies, high-frequency transformers are usually used for boosting. The primary winding is composed of multiple windings in parallel, and the secondary winding is composed of multiple windings in series. Such a layout can realize the parallel feeding input of the primary multi-channel power modules of the power transformer, the synchronous transformation and series boosting of the secondary multi-channel power modules of the transformer, and finally realize the high-voltage and high-power output of the power supply, while also conveniently solving the problem of modular integration and expansion of the power supply.

[0003] In the high-voltage and high-frequency LCC charging power supply, the use of a high-frequency transformer with a common core multi-way primary winding in parallel and a common core multi-way secondary winding in series can significantly reduce the weight and volume of the transformer and the power supply, but the power supply output characteristic parameters (such as output voltage, output power, etc.) will be significantly affected by the transformer winding distributed capacitance; especially under high-frequency conditions of ≥100kHz, the unexpected distributed capacitance effect is significantly enhanced, and the problem of large winding distributed capacitance caused by the common core multi-winding coupling structure of the high-frequency transformer will seriously affect the design and adjustment of the parallel resonant capacitor in the charging circuit of the high-voltage and high-frequency LCC charging power supply, and seriously reduce the power supply output voltage, power and energy efficiency level. Therefore, clarifying the coupling distribution law of the common core multi-winding distributed capacitance, establishing an equivalent circuit model of the common core multi-winding distributed capacitance, and exploring a set of common core multi-winding distributed capacitance accurate evaluation methods are the basis for solving the problem that the parameters of the high-voltage and high-frequency LCC charging power supply cannot be accurately designed.

[0004] The high-frequency transformer of the high-voltage and high-frequency LCC charging power supply adopts a configuration of multiple primary windings in parallel with a common core and multiple secondary windings in series with a common core, forming multiple complex transformer coupling structures between many primary windings and secondary windings, making the series and parallel distributed capacitance and coupling equivalent relationship of each winding extremely complicated. Existing scholars use lumped parameter models to equivalently model the distributed capacitance of transformer windings, and then analyze the influence of the lumped capacitance parameters of the equivalent distributed capacitance on the performance of the transformer circuit, but these studies are mostly limited to the case of simple windings with a common core. At present, there is no public research report on the accurate evaluation method of equivalent distributed capacitance of multiple secondary windings to the primary of the transformer in the transformer configuration of multiple primary windings in parallel with a common core and multiple secondary windings in series with a common core. In addition, since the winding of the transformer is a section of wire, it is difficult to use general instruments or equipment to directly test the equivalent distributed capacitance at both ends of the winding wire; even if the equivalent distributed capacitance of the winding is tested by precision impedance analyzers and other equipment, when the test frequency changes and approaches the resonant frequency point formed by the winding inductance and the equivalent distributed capacitance, the measured equivalent distributed capacitance value varies greatly with the frequency, and it is difficult to reflect the true equivalent distributed capacitance level. Therefore, how to clarify the coupling equivalence law of the common core multi-channel series and parallel winding distributed capacitance, explore a set of common core multi-winding coupling secondary distributed capacitance equivalent to the primary accurate evaluation method, give the common core multi-winding coupling transformer primary equivalent parallel distributed capacitance accurate evaluation value, solve the problem of accurate design of the high-voltage and high-frequency LCC charging power supply parallel resonant capacitance parameters, for the design, application and promotion of small and light high-voltage and high-frequency LCC charging power, has important significance and practical value. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that it is difficult to accurately evaluate the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer in an existing high-voltage and high-frequency LCC charging power supply, which leads to the inability to accurately design the power supply parallel resonant capacitance parameters, and provides a method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer is special in that it comprises the following steps:

[0008] 1) Build a common core multi-winding coupled transformer test circuit and establish an equivalent circuit model of the distributed capacitance of the common core multi-winding coupled transformer windings;

[0009] 2) Test the curve of the core single-turn winding inductance of the common-core multi-winding coupling transformer changing with the test frequency to obtain the single-turn winding inductance;

[0010] 3) Test the primary winding characteristic impedance curve of the common core multi-winding coupling transformer to obtain the primary sub-winding resonant frequency point;

[0011] 4) Calculate the primary sub-winding inductance at the operating frequency based on the single-turn winding inductance obtained in step 2);

[0012] 5) According to the primary sub-winding resonant frequency point obtained in step 3) and the primary sub-winding inductance obtained in step 4), calculate the primary winding equivalent parallel distributed capacitance of the equivalent circuit model obtained in step 1) at the operating frequency, and complete the evaluation of the primary equivalent parallel distributed capacitance of the common core multi-winding coupled transformer.

[0013] Further, step 1) is specifically as follows:

[0014] 1.1. The primary winding of the common-core multi-winding coupling transformer is composed of m primary sub-windings, and the m primary sub-windings have a common magnetic core, where m ≥ 1, and m is an integer; the two ends of the i-th primary sub-winding are respectively used to connect to the two output ends of the full-bridge LCC resonant circuit module i, i = 1, ..., m;

[0015] 1.2. A secondary winding of a multi-winding coupling transformer with a common magnetic core is formed by n secondary sub-windings, and the n secondary sub-windings have a common magnetic core, wherein n ≥ 1, and n is an integer; two ends of the j-th secondary sub-winding are respectively used to connect to two input ends of a rectifier bridge j in the n rectifier bridges connected in series, j = 1, ..., n;

[0016] 1.3. Equivalent parallel distributed capacitance C at both ends of the primary sub-winding of the i-th path rpi , and the equivalent circuit model of the distributed capacitance of the common-core multi-winding coupled transformer windings is obtained.

[0017] Further, step 2) is specifically as follows:

[0018] 2.1. Use an insulated wire to wind one turn on the closed core of the common core multi-winding coupling transformer to form a single-turn winding;

[0019] 2.2. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the wound single-turn winding respectively, and perform a frequency sweep test to obtain the curve data of the change of the single-turn winding inductance L0 with the test frequency f L0(f)~f, 1Hz≤f≤10MHz;

[0020] 2.3. According to the curve data L0(f)~f, the single-turn winding inductance L0(f0) is obtained.

[0021] Further, step 3) is specifically as follows:

[0022] 3.1. Disconnect both ends of the m-way primary sub-winding of the common-core multi-winding coupling transformer from the m-way full-bridge LCC resonant circuit module to form an open circuit;

[0023] 3.2. Disconnect both ends of the n-way secondary sub-windings of the common-core multi-winding coupling transformer from the n-way rectifier bridge modules to form an open circuit;

[0024] 3.3. Clamp the two test clips of the impedance analyzer with a bandwidth greater than 10MHz to the two ends of the primary sub-winding of the i-th path respectively, and obtain the characteristic impedance Z of the primary sub-winding of the i-th path by frequency sweep test. 0i Curve data Z changes with test frequency f 0i ~f, i=1,…,m;

[0025] 3.4. According to the curve data Z 0i ~f, get Z 0i The frequency corresponding to the maximum value point is taken as the resonant frequency point f of the primary sub-winding of the i-th path ri .

[0026] Further, step 4) is specifically as follows:

[0027] 4.1. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the primary sub-winding of the i-th path respectively, and measure the inductance L of the primary sub-winding of the i-th path. p0i , i=1,…,m;

[0028] 4.2. Define the transformer winding operating frequency as f0. According to the single-turn winding inductance L0(f0) obtained in step 2), calculate the primary sub-winding inductance L of the i-th path by the following formula: pi (f0):

[0029] L pi (f0) = L p0i ×L0(f0) / L0(f).

[0031] Further, in step 5), the equivalent parallel distributed capacitance C of the primary sub-winding at the operating frequency is calculated by the following formula: rpi (f0):

[0032]

[0033] Wherein, i=1,…,m, and f0 is the operating frequency.

[0034] Furthermore, in step 2.2), step 3.3) and step 4.1, the data sampling rate of the impedance analyzer is 1 Hz.

[0035] Furthermore, in step 2.1, the diameter of the wire is less than 1 mm.

[0036] Furthermore, in step 4.2, the value of the test frequency f is 1 kHz.

[0037] Beneficial effects of the present invention:

[0038] 1. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer of the present invention realizes accurate evaluation of the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer, thereby solving the problem that it is difficult to accurately evaluate the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer of a high-voltage and high-frequency LCC inverter power supply;

[0039] 2. The method for evaluating the primary equivalent parallel distributed capacitance of the common core multi-winding coupled transformer of the present invention has the characteristics of simple principle, convenient testing, accurate and reliable results, significantly improves the design accuracy of the parallel resonant capacitance parameters of the high-voltage and high-frequency LCC inverter power supply, greatly reduces the difficulty of debugging the parallel resonant capacitance parameters, and can expand the application scope of the high-voltage and high-frequency LCC inverter power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of establishing an equivalent circuit model of the distributed capacitance of the windings of a common-core multi-winding coupling transformer in step 1 in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupling transformer of the present invention comprises the following steps:

[0042] 1) Build a common core multi-winding coupled transformer test circuit and establish an equivalent circuit model of the common core multi-winding coupled transformer winding distributed capacitance, such as Figure 1 As shown;

[0043] 1.1. The primary winding of the multi-winding coupling transformer with a common core is composed of m primary sub-windings, and the m primary sub-windings have a common core, where m ≥ 1 and m is an integer; the number of turns of the i-th primary sub-winding is defined as Np i turns, i is an integer, and i=1, ..., m; the two ends of the i-th primary sub-winding are respectively used to connect to the two output ends of the full-bridge LCC resonant circuit module i; the common core multi-winding coupling transformer includes multiple primary windings, and each primary winding includes multiple primary sub-windings;

[0044] 1.2. The secondary winding of the multi-winding coupling transformer with a common core is composed of n secondary sub-windings, and the n secondary sub-windings have a common core, where n ≥ 1 and n is an integer; the number of turns of the j-th secondary sub-winding is defined as Ns j turns, where j is an integer, and j=1, ..., n; the two ends of the j-th secondary sub-winding are respectively used to connect to the two input ends of the rectifier bridge j in the series-connected n-way rectifier bridge; the common magnetic core multi-winding coupling transformer includes a plurality of secondary windings, and each secondary winding includes a plurality of secondary sub-windings;

[0045] 1.3. Equivalent parallel distributed capacitance C at both ends of the primary sub-winding of the i-th path rpi , the equivalent circuit model of the distributed capacitance of the common core multi-winding coupled transformer winding is obtained; the equivalent parallel distributed capacitance C of the two ends of the j-th secondary winding can also be calculated. rsj .

[0046] 2) Test the curve of the core single-turn winding inductance of the common-core multi-winding coupling transformer changing with the test frequency to obtain the single-turn winding inductance;

[0047] 2.1. Use an insulated wire (the diameter of the wire is less than 1mm) to wind one turn on the closed core of the common core multi-winding coupling transformer to form a single-turn winding;

[0048] 2.2. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the wound single-turn winding respectively, and perform a frequency sweep test to obtain the curve data L0(f)~f of the change of the single-turn winding inductance L0 with the test frequency f, 1Hz≤f≤10MHz; the data sampling rate of the impedance analyzer is 1Hz;

[0049] 2.3. According to the curve data L0(f)~f, the single-turn winding inductance L0(f0) is obtained.

[0050] 3) Test the primary winding characteristic impedance curve of the common core multi-winding coupling transformer to obtain the resonant frequency point;

[0051] 3.1. Disconnect both ends of the m-way primary sub-winding of the common-core multi-winding coupling transformer from the m-way full-bridge LCC resonant circuit module to form an open circuit;

[0052] 3.2. Disconnect both ends of the n-way secondary sub-windings of the common-core multi-winding coupling transformer from the n-way rectifier bridge modules to form an open circuit;

[0053] 3.3. Clamp the two test clips of the impedance analyzer with a bandwidth greater than 10MHz to the two ends of the primary sub-winding of the i-th path respectively, and obtain the characteristic impedance Z of the primary sub-winding of the i-th path by frequency sweep test. 0i Curve data Z changes with test frequency f 0i ~f, i=1,…,m;

[0054] 3.4. According to the curve data Z 0i ~f, get Z 0i The frequency corresponding to the maximum value point is taken as the resonant frequency point f of the primary sub-winding of the i-th path ri ;

[0055] 4) Calculate the primary sub-winding inductance at the operating frequency based on the single-turn winding inductance obtained in step 2);

[0056] 4.1. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the primary sub-winding of the i-th path respectively, and measure the inductance L of the primary sub-winding of the i-th path. p0i , i=1,…,m;

[0057] 4.2. Define the transformer winding operating frequency as f0. According to the single-turn winding inductance L0(f0) obtained in step 2), calculate the primary sub-winding inductance L of the i-th path by the following formula: pi (f0):

[0058] L pi (f0) = L p0i ×L0(f0) / L0(f)

[0059] In the formula, the test frequency f is 1kHz;

[0060] 5) According to step 3) and step 4), calculate the equivalent parallel distributed capacitance C of the primary sub-winding at both ends of the i-th path at the operating frequency f0 by the following formula: rpi (f0), complete the evaluation of the primary equivalent parallel distributed capacitance of the common core multi-winding coupled transformer:

[0061]

[0062] In other embodiments, according to the equivalent parallel distributed capacitance C at both ends of the i-th primary sub-winding rpi , the equivalent parallel distributed capacitance C at both ends of the corresponding j-th secondary winding can be calculated rsj .

[0063] The method for evaluating the primary equivalent parallel distributed capacitance of the common core multi-winding coupled transformer of the present invention is used to evaluate the equivalent parallel distributed capacitance at both ends of each primary sub-winding in the multi-common core multi-winding coupled transformer in the existing DC100kV high-voltage and high-frequency LCC inverter power supply, as follows:

[0064] (1) Establish an equivalent circuit model of the distributed capacitance of the windings of a common-core multi-winding coupled transformer;

[0065] The primary winding of the common-core multi-winding coupling transformer in the DC100kV high-voltage and high-frequency LCC inverter power supply consists of 4 primary sub-windings, and the 4 primary sub-windings have a common core; the number of turns of the i-th primary sub-winding is Np i , where i is an integer and 1≤i≤4, Np i =1; both ends of the i-th primary sub-winding are respectively connected to the two output ends of the full-bridge LCC resonant circuit module i in the high-voltage and high-frequency LCC inverter power supply.

[0066] The secondary winding of the common core multi-winding coupling transformer in the high-voltage and high-frequency LCC inverter power supply consists of 4 secondary sub-windings, and the 4 secondary sub-windings have a common core; the number of turns of the j-th secondary sub-winding is Ns j , where j is an integer and 1≤j≤4, Ns j =66; the two ends of the j-th secondary sub-winding are respectively connected to the two input ends of the rectifier bridge j in the high-voltage and high-frequency LCC inverter power supply; the secondary n-way rectifier bridges are connected in series in sequence to boost the voltage.

[0067] The equivalent parallel distributed capacitance C at both ends of the primary sub-winding of the i-th circuit is rpi , the equivalent parallel distributed capacitance C at both ends of the j-th secondary winding rsj ; In this embodiment, the equivalent parallel distributed capacitance C rpi Comprehensively consider the equivalent parallel distributed capacitance C at both ends of the secondary sub-winding rsj equivalent effect.

[0068] (2) Test the curve of the change of the inductance of the single-turn winding of the common-core multi-winding coupled transformer core with the test frequency;

[0069] Before the transformer is wound, a thin wire with insulation (less than 1 mm in diameter) is wound on its closed magnetic core to form a single-turn winding; there is no other winding on the magnetic core;

[0070] The two test clips of the impedance analyzer with a bandwidth of 30MHz are clamped to the two ends of the wound single-turn winding respectively, and the single-turn winding inductance L0 is tested with a sweep frequency to obtain the curve data L0(f)~f of the change of the test frequency f, where 1Hz≤f≤10MHz, and the data sampling rate of the impedance analyzer is 1Hz;

[0071] (3) Test the resonant frequency point of the primary winding characteristic impedance curve;

[0072] Disconnect both ends of the four primary sub-windings of the common-core multi-winding coupling transformer of the high-voltage and high-frequency LCC charging power supply from the four-way full-bridge LCC resonant circuit modules to form an open circuit; disconnect both ends of the four secondary sub-windings of the common-core multi-winding coupling transformer of the high-voltage and high-frequency LCC charging power supply from the four-way rectifier bridge modules to form an open circuit.

[0073] The two test clips of the impedance analyzer with a bandwidth of 30MHz are clamped to the two ends of the primary sub-winding of the transformer that has been opened. The characteristic impedance Z of the primary sub-winding of the i-th path is obtained by frequency sweep test. 0i Curve data with test frequency f, where 1Hz≤f≤10MHz, and the data sampling rate of the impedance analyzer is 1Hz; from the measured Z 0i From the ~f curve data, we can obtain Z 0i The maximum value point, the frequency corresponding to the maximum value point is the resonant frequency point f of the primary sub-winding of the i-th pathri ; The 4-way primary sub-winding Z of the common-core multi-winding coupling transformer in the existing DC100kV high-voltage and high-frequency LCC inverter power supply 0i ~f curve resonance frequency point f ri The test data is summarized in Table 1:

[0074] Table 1

[0075] i＝1 i＝2 i＝3 i＝4 <![CDATA[f r1 =166kHz]]> <![CDATA[f r2 =160kHz]]> <![CDATA[f r3 =168kHz]]> <![CDATA[f r4 =165kHz]]>

[0076] (4) Calculate the primary sub-winding inductance at the operating frequency;

[0077] The two test clips of the impedance analyzer with a bandwidth of 30MHz are clamped to the two ends of the primary sub-winding of the transformer with the i-th path already open, and the inductance L of the primary sub-winding of the i-th path at 1kHz is measured. p0i ; Impedance analyzer measures the inductance L of the primary winding of the i-th path p0i The data are summarized in Table 2:

[0078] Table 2

[0079] i＝1 i＝2 i＝3 i＝4 <![CDATA[L p01 =6.23μH]]> <![CDATA[L p02 =6.25μH]]> <![CDATA[L p03 =6.21μH]]> <![CDATA[L p04 =6.26μH]]>

[0080] In this embodiment, the common core multi-winding coupling transformer adopts a high permeability closed core, and the actual operating frequency of its winding is f0 = 200kHz; in the measured curve data L0(f)~f, L0(f0) = 6.75μH, L0(1kHz) = 6.23μH. The leakage inductance of each primary sub-winding is two orders of magnitude smaller than the inductance of each primary sub-winding, so the inductance of the primary sub-winding of the i-th path L pi It is approximately proportional to the relative magnetic permeability of the magnetic core. The inductance L of the primary sub-winding of the i-th circuit at the operating frequency f0 is calculated by the following formula: pi (f0):

[0081] L pi (f0) = L p0i ×L0(f0) / L0(1kHz)

[0082] From the above formula, we can get the inductance L of the primary winding of the i-th circuit at the operating frequency f0: pi (f0) data see Table 3:

[0083] Table 3

[0084] i＝1 i＝2 i＝3 i＝4 <![CDATA[L p1 (f0)=6.75μH]]> <![CDATA[L p2 (f0)=6.77μH]]> <h2 style=";text-align:left;direction:ltr"><![CDATA[L <h2 style=";text-align:left;direction:ltr"> p3 <h2 style=";text-align:left;direction:ltr"> (f0) = 6.73μH<h2 style=";text-align:left;direction:ltr"> <![CDATA[L p4 (f0)=6.78μH]]>

[0085] (5) Calculate the equivalent parallel distributed capacitance of the primary winding at the operating frequency;

[0086] At the operating frequency f0 = 200kHz, the equivalent parallel distributed capacitance C at both ends of the primary sub-winding of the i-th path is rpi(f0), calculated by the following formula, see Table 4:

[0087]

[0088] Table 4

[0089]

[0090]

[0091] The calculated equivalent parallel distributed capacitance C rpi (f0) is the only parallel resonant capacitor of the full-bridge LCC resonant circuit module i in the existing DC100kV high-voltage and high-frequency LCC inverter power supply; the resonant current frequency and amplitude output by the full-bridge LCC resonant circuit module i are measured, which are respectively related to the equivalent parallel distributed capacitance C rpi The resonant current frequency and amplitude of the full-bridge LCC resonant circuit module i obtained by theoretical design of (f0) value are consistent, indicating that the equivalent parallel distributed capacitance C rpi (f0) The evaluation results are accurate and reliable. The test results prove that the method of the present invention solves the problem of accurate evaluation of the primary equivalent parallel distributed capacitance of the common core multi-winding coupling transformer.

Claims

1. A method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer, characterized in that: The following steps are involved: 1) Build a common core multi-winding coupled transformer test circuit and establish an equivalent circuit model of the distributed capacitance of the common core multi-winding coupled transformer windings; 2) Test the curve of the core single-turn winding inductance of the common-core multi-winding coupling transformer changing with the test frequency to obtain the single-turn winding inductance; 3) Test the primary winding characteristic impedance curve of the common core multi-winding coupling transformer to obtain the primary sub-winding resonant frequency point; 4) Calculate the primary sub-winding inductance at the operating frequency based on the single-turn winding inductance obtained in step 2); 5) According to the primary sub-winding resonant frequency point obtained in step 3) and the primary sub-winding inductance obtained in step 4), calculate the primary winding equivalent parallel distributed capacitance of the equivalent circuit model obtained in step 1) at the operating frequency, and complete the evaluation of the primary equivalent parallel distributed capacitance of the common core multi-winding coupled transformer.

2. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 1 is characterized in that: Step 1) is specifically as follows: 1.

1. The primary winding of the common-core multi-winding coupling transformer is composed of m primary sub-windings, and the m primary sub-windings have a common magnetic core, where m ≥ 1, and m is an integer; the two ends of the i-th primary sub-winding are respectively used to connect to the two output ends of the full-bridge LCC resonant circuit module i, i = 1, ..., m; 1.

2. A secondary winding of a multi-winding coupling transformer with a common magnetic core is formed by n secondary sub-windings, and the n secondary sub-windings have a common magnetic core, wherein n ≥ 1, and n is an integer; two ends of the j-th secondary sub-winding are respectively used to connect to two input ends of a rectifier bridge j in the n rectifier bridges connected in series, j = 1, ..., n; 1.

3. Equivalent parallel distributed capacitance C at both ends of the primary sub-winding of the i-th path rpi , and the equivalent circuit model of the distributed capacitance of the common-core multi-winding coupled transformer windings is obtained.

3. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 2 is characterized in that: Step 2) is specifically as follows: 2.

1. Use an insulated wire to wind one turn on the closed core of the common core multi-winding coupling transformer to form a single-turn winding; 2.

2. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the wound single-turn winding respectively, and perform a frequency sweep test to obtain the curve data of the change of the single-turn winding inductance L0 with the test frequency f L0(f)~f, 1Hz≤f≤10MHz; 2.

3. According to the curve data L0(f)~f, the single-turn winding inductance L0(f0) is obtained.

4. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 3 is characterized in that: Step 3) is specifically: 3.

1. Disconnect both ends of the m-way primary sub-winding of the common-core multi-winding coupling transformer from the m-way full-bridge LCC resonant circuit module to form an open circuit; 3.

2. Disconnect both ends of the n-way secondary sub-windings of the common-core multi-winding coupling transformer from the n-way rectifier bridge modules to form an open circuit; 3.

3. Clamp the two test clips of the impedance analyzer with a bandwidth greater than 10MHz to the two ends of the primary sub-winding of the i-th path respectively, and obtain the characteristic impedance Z of the primary sub-winding of the i-th path by frequency sweep test. 0i Curve data Z changes with test frequency f 0i ~f, i = 1, ..., m; 3.

4. According to the curve data Z 0i ~f, get Z 0i The frequency corresponding to the maximum value point is taken as the resonant frequency point f of the primary sub-winding of the i-th path ri .

5. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 4 is characterized in that: Step 4) is specifically as follows: 4.

1. Use two test clips of an impedance analyzer with a bandwidth greater than 10MHz to clamp the two ends of the primary sub-winding of the i-th path respectively, and measure the inductance L of the primary sub-winding of the i-th path. p0i , i=1,…,m; 4.

2. Define the transformer winding operating frequency as f0. According to the single-turn winding inductance L0(f0) obtained in step 2), calculate the primary sub-winding inductance L of the i-th path by the following formula: pi (f0): L pi (f0)=L p0i ×L0(f0) / L0(f).

6. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 5, characterized in that: In step 5), the equivalent parallel distributed capacitance C of the primary sub-winding at the operating frequency is calculated by the following formula: rpi (f0): Wherein, i=1,…,m, and f0 is the operating frequency.

7. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 6, characterized in that: In step 2.2), step 3.3) and step 4.1, the data sampling rate of the impedance analyzer is 1 Hz.

8. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 7, characterized in that: In step 2.1, the diameter of the wire is less than 1 mm.

9. The method for evaluating the primary equivalent parallel distributed capacitance of a common core multi-winding coupled transformer according to claim 8, characterized in that: In step 4.2, the test frequency f is set to 1kHz.

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