CN114499206A - Method for designing bidirectional asymmetric operation parameters of CLLC resonant converter - Google Patents

Method for designing bidirectional asymmetric operation parameters of CLLC resonant converter Download PDF

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CN114499206A
CN114499206A CN202210034991.XA CN202210034991A CN114499206A CN 114499206 A CN114499206 A CN 114499206A CN 202210034991 A CN202210034991 A CN 202210034991A CN 114499206 A CN114499206 A CN 114499206A
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cllc
gain
representing
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reverse
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黄金伟
李小强
马永超
吴富强
徐荣姬
王心潭
叶继铭
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China University of Mining and Technology CUMT
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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Abstract

The invention discloses a method for designing bidirectional asymmetric operation parameters of a CLLC (CLLC) resonant converter, which comprises the steps of establishing a quantity relation between forward and reverse circuit factors, and unifying the forward and reverse circuit factors into an inductance ratio k, a capacitance ratio b and a quality factor Q; respectively expressing the input impedance and the voltage gain expression of the CLLC resonant converter in a bidirectional unified manner by using k, b, Q and the normalized frequency omega to obtain the selection principle and range of k, b and Q; and finally, according to different bidirectional gain ranges of battery charging and discharging application occasions, the bidirectional gain curves are related to design specific values of k, b and Q, and resonance parameters of the CLLC resonance converter are calculated. According to the scheme, the CLLC resonant converter parameters are designed by linking the two-way gain curves, so that a large amount of calculation and repeated iteration in the traditional design process are avoided, and the design difficulty of the CLLC resonant converter parameters is reduced; the bidirectional gain can reach a higher range, and the range of the bidirectional switching frequency can be reduced.

Description

Method for designing bidirectional asymmetric operation parameters of CLLC resonant converter
Technical Field
The invention belongs to the field of DC/DC converters, relates to a bidirectional CLLC resonant converter, and particularly relates to a method for designing bidirectional asymmetric operation parameters of the CLLC resonant converter.
Background
With the rapid development of energy storage systems and the popularization of electric vehicles, battery charging equipment is becoming a hotspot in the research field of current power electronic converters. Conventional one-way battery charging devices have failed to meet the challenge of feeding energy back to the grid, and new two-way charging devices are receiving increasing attention. As a core component of the bidirectional charging equipment, the isolated bidirectional DC-DC converter has the characteristics of electrical isolation, bidirectional transmission, grade conversion and the like.
In the isolated bidirectional DC-DC converter, the CLLC resonant converter adopts a resonant mode to realize soft switching, not only has the characteristic of high switching frequency, but also has the advantages of forward and reverse full-range soft switching, can realize zero voltage conduction and zero current turn-off at the same time, has small switching stress, obviously reduces the circulating energy and reduces the switching loss. The frequency modulation control is adopted, so that high frequency, high efficiency and high power density are easy to realize. However, in the current research, most of the parameter design methods of the CLLC resonant converter are to design the forward and reverse voltage gain curves to be the same curve, that is, the LC resonant element on the secondary side is designed to be equivalent to the LC element on the primary side and then is equal to the LC element on the secondary side (L)r1＝n2Lr2，Cr1＝Cr2/n2) For example, as disclosed in patent document 202011585866.5, the method for designing parameters of a bidirectional resonant CLLC converter is mainly applied to a dc transformer with uniform bidirectional gain and a narrow range, and is not suitable for a battery charging device with non-uniform bidirectional gain and a wide range.
For the application occasions of battery charging equipment with bidirectional asymmetric operation and wide gain range, the asymmetric operation parameters of the converter are mainly determined by a large amount of calculation and forward and reverse repeated iteration, and the iteration process needs to judge whether the gain curve meets the design requirements of the forward and reverse directions and also needs to judge whether the gain curve is monotonically decreased within the working frequency range. Although the method can obtain the asymmetric operation parameters of the converter, the calculation amount is large, forward and reverse repeated iteration is needed, forward and reverse voltage gains cannot be designed simultaneously, bidirectional wide gain is difficult to realize, and the range of bidirectional switching frequency cannot be reduced.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a method for designing bidirectional asymmetric operation parameters of a CLLC resonant converter, which has the advantages that the parameters of the CLLC resonant converter can be designed by linking bidirectional gain curves, so that a large amount of calculation and repeated iteration in the traditional design process are avoided, and the design difficulty of the parameters of the CLLC resonant converter is reduced; the bidirectional gain can reach a higher range, and the range of the bidirectional switching frequency can be reduced.
The technical scheme is as follows: the invention discloses a method for designing bidirectional asymmetric operation parameters of a CLLC resonant converter, which comprises the following steps:
(1) establishing a corresponding quantity relation of forward and reverse circuit factors, and expressing the quantity relation by using a uniform circuit factor inductance ratio k, a uniform circuit factor capacitance ratio b and a uniform quality factor Q;
(2) expressing a bidirectional unified input impedance and voltage gain expression of the CLLC resonant converter by using k, b, Q and normalized frequency omega according to a forward and reverse fundamental wave equivalent model of the CLLC resonant converter;
(3) analyzing the influence of k, b and Q on the bidirectional unified input impedance angle and voltage gain of the CLLC resonant converter, and obtaining the selection principle and range of k, b and Q;
(4) determining the input voltage V according to the design requirementinOutput voltage range Vomin～VomaxForward resonant frequency omegarfOutput voltage V at resonant frequencyoPower P, primary and secondary side turn ratio n of transformer as Vin/VoForward gain range nVomin/Vin～nVomax/VinReverse gain range Vin/nVomax～Vin/nVomin；
(5) Combining the forward and reverse input impedance angles, and designing specific values of k, b and Q meeting the requirements of a bidirectional gain range and a soft switch by linking forward and reverse gain curves;
(6) according to specific values of k, b and Q and forward resonant frequency omega rf1, justTo an equivalent resistance RefAnd calculating to obtain the resonance parameters of the CLLC resonance converter.
In the step (1), the same forward and reverse resonant frequencies are set, and the corresponding relation of forward and reverse circuit factors is obtained as follows:
Figure BDA0003467992530000021
in the formula, kf、bf、QfDenotes the forward circuit factor, where kfRepresenting the ratio of excitation inductance to primary resonance inductance, bfRepresenting the ratio, Q, of the resonant capacitance coupled to the primary side resonant capacitancefRepresenting a forward quality factor; a isfRepresenting the ratio of the resonant inductance coupled to the primary side resonant inductance; k is a radical ofr、br、QrDenotes the inverse circuit factor, where krRepresenting the ratio of the excitation inductance coupled to the secondary resonance inductance, brRepresenting the ratio of the resonant capacitance coupled to the secondary side resonant capacitance, QrRepresenting an inverse quality factor; a isrRepresenting the ratio of the resonant inductance coupled to the secondary side resonant inductance.
In the step (1), expressions of the factors of the forward and reverse circuits are as follows:
Figure BDA0003467992530000031
in the formula, ωrfRepresents a forward resonant frequency; omegasRepresents the switching frequency; ω represents the normalized frequency; l isr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n represents the turn ratio of the primary side and the secondary side of the transformer of the CLLC resonant converter; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; voRepresents a forward rated output voltage; p represents the output power; omegarrTo express contraryToward the resonant frequency; rerAn equivalent resistance representing the coupling of the inverting output resistance to the secondary side of the transformer; vinRepresenting a nominal input voltage in the forward direction.
In the step (2), according to a forward and reverse fundamental wave equivalent model of the CLLC resonant converter, expressions of a bidirectional uniform input impedance angle and a voltage gain of the CLLC resonant converter are represented by k, b, Q and ω as follows:
Figure BDA0003467992530000032
Figure BDA0003467992530000033
in the formula, ZinuRepresenting the input impedance which is uniform in forward and reverse directions; muRepresenting a uniform voltage gain in forward and reverse directions; reRepresenting the forward and reverse equivalent resistance.
In the step (3), the influences of k, b and Q on the positive and negative input impedance angles and the voltage gain are as follows: the smaller k is, the larger the obtained gain range is, the narrower the frequency regulation range is, two peak values cannot appear, but the soft switching range is narrowed, the lower the efficiency of the converter is, and since the positive and negative k is positive correlation, the k is maximized under the condition that the positive and negative voltage gain, the soft switching range and the single peak value are ensured; b is smaller, the obtained voltage gain is higher, the gain curve is steeper, the soft switch range is wider, but two peak values can appear; the smaller Q, the higher the voltage gain is obtained, the steeper the gain curve at ω <1, and the slower the gain curve at ω >1, the wider the soft switching range, and no two peaks occur.
In the step (3), the selection principles and ranges of k, b and Q are as follows: q ranges from 0 to 0.5; b ranges from 0.8 to 1.25, and when the forward maximum gain is smaller than the reverse maximum gain, b is greater than 1, and Q is obtained at the momentrLess than Qf(ii) a k ranges from 3 to 8.
In the step (5), a group of initial values in the ranges of k, b and Q are selected as specific values of the forward circuit factorCalculating to obtain a specific numerical value of the reverse circuit factor; substituting specific values of forward circuit factors into MuAnd ZinuDrawing the curve of forward gain, input impedance angle and normalized frequency omega, substituting the specific value of reverse circuit factor into MuAnd ZinuDrawing a curve of the reverse gain, the input impedance angle and the normalized frequency omega; when the forward and reverse gain ranges, soft switching and single peak requirements are simultaneously met, a specific set of values k, b and Q is obtained.
In the step (6), the formula of the resonance parameter of the CLLC resonant converter is as follows:
Figure BDA0003467992530000041
in the formula, Lr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n represents the turn ratio of the primary side and the secondary side of the transformer of the CLLC resonant converter; omegarfRepresents a forward resonant frequency; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; k represents the inductance ratio in the unity circuit factor; b represents the capacitance ratio in the unity circuit factor; q represents the quality factor in the unity circuit factor.
Has the advantages that: compared with the prior art, the invention has the beneficial effects that: (1) establishing a quantity relation of forward and reverse circuit factors of the CLLC resonant converter, and unifying forward and reverse input impedance and a voltage gain expression; (2) the forward and reverse voltage gain curves are linked to be designed, so that a large amount of calculation and forward and reverse repeated iteration are avoided; (3) the bidirectional gain can reach a higher range, and the range of the bidirectional switching frequency can be reduced.
Drawings
FIG. 1 is a topological diagram of a CLLC resonant converter of the present invention;
FIG. 2 is a flow chart of a method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to the present invention;
FIG. 3 is a forward and reverse equivalent circuit model of the CLLC resonant converter of the present invention;
FIG. 4 shows the gain M of the present inventionuAnd input impedance angle thetauA graph relating normalized frequency ω to inductance ratio k;
FIG. 5 shows the gain M of the present inventionuAnd input impedance angle thetauA graph relating normalized frequency ω to capacitance ratio b;
FIG. 6 shows the gain M of the present inventionuAnd input impedance angle thetauA graph relating normalized frequency ω to quality factor Q;
fig. 7 is a graph of forward and reverse gain and input impedance angle with normalized frequency ω of the present invention, where k is 3.6, b is 1.2, and Q is 0.375.
Detailed Description
The technical scheme of the invention is further described in detail by combining the drawings and the detailed description.
The parameters of the invention are defined as follows: vin-an input voltage; cin-an input side filter capacitance; vo-an output voltage; co-an output side filter capacitance; i iso-an output current; i.e. i1、i2Primary and secondary side resonance currents; l isr1、Lr2-primary and secondary side resonant inductances of the CLLC resonant converter; l ism-CLLC resonant converter transformer excitation inductance; cr1、Cr2-primary and secondary side resonance capacitors of the CLLC resonance converter; n-CLLC resonance converter transformer primary and secondary side turn ratio; vinf-a forward input voltage; vof-a forward output voltage; ref-an equivalent resistance coupled to the primary side of the transformer; vinr-an inverted input voltage; vor-a reverse output voltage; rerAn equivalent resistance coupled back to the secondary side of the transformer; k is the inductance ratio; b-capacitance ratio; q is the quality factor; ω — normalized frequency; mu-a voltage gain; thetau-input impedance angle.
As shown in fig. 1, the circuit of the CLLC resonant converter is mainly composed of three parts: the primary side full bridge circuit, the secondary side full bridge circuit and the CLLC resonant cavity. When the converter is operating in the forward direction, the primary sideFull bridge S1～S4Is a main switch tube (synchronous rectification of a secondary side full bridge is temporarily ignored), S1、S4Signal synchronization, S2、S3The signals are synchronous, the switch tubes of the same bridge arm work complementarily and symmetrically by the driving signals with 50 percent (neglecting dead time) duty ratio, and the voltage v of the two points AB isAB(t) is a high frequency square wave with a frequency equal to the switching frequency omegasAmplitude equal to input voltage VinAnd then the output is obtained after the rectification by the resonant cavity and the secondary side full bridge circuit. When the converter is operated in reverse, the secondary side is full-bridge S5～S8Two-point voltage v of CD as main switch tubeCD(t) is a high frequency square wave with a frequency equal to the switching frequency omegasAmplitude equal to the reverse input voltage VoAnd the output is output after being rectified by the resonant cavity and the primary side full bridge circuit.
As shown in fig. 2, the method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter specifically includes the following steps:
step 1, establishing a corresponding relation of forward and reverse circuit factors, and expressing the corresponding relation by using uniform circuit factors k, b and Q, wherein the method specifically comprises the following steps:
setting the same forward and reverse resonant frequency to obtain the corresponding relationship of forward and reverse circuit factors as follows:
Figure BDA0003467992530000061
in the formula, kf、bf、QfDenotes the forward circuit factor, where kfRepresenting the ratio of excitation inductance to primary resonance inductance, bf(af) Representing the ratio of the resonant capacitance (inductance) coupled to the primary side to the resonant capacitance (inductance) of the primary side, QfRepresenting a forward quality factor; k is a radical ofr、br、QrDenotes the inverse circuit factor, where krRepresenting the ratio of the excitation inductance coupled to the secondary resonance inductance, br(ar) Representing the ratio of the resonant capacitance (inductance) coupled to the secondary side to the resonant capacitance (inductance) of the secondary side, QrRepresenting an inverse quality factor; expression of forward and reverse circuit factorsThe formula is as follows:
Figure BDA0003467992530000062
in the formula, ωrfRepresents a forward resonant frequency; omegasRepresents the switching frequency; ω represents the normalized frequency; l isr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n represents the turn ratio of the primary side and the secondary side of the transformer of the CLLC resonant converter; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; voRepresents a forward rated output voltage; p represents the output power; omegarrRepresents the inverse resonance frequency; rerAn equivalent resistance representing the coupling of the inverting output resistance to the secondary side of the transformer; vinRepresents a forward rated input voltage;
inverse circuit factor (k)r，br，Qr) The forward circuit factor (k) can be fully usedf，bf，Qf) The forward and reverse circuit factors can be represented in a unified form by unified circuit factors (inductance ratio k, capacitance ratio b, quality factor Q).
Step 2, expressing the input impedance and the voltage gain expression of the CLLC resonant converter with uniform forward and reverse directions by using k, b and Q, and specifically comprising the following steps:
according to the forward and reverse fundamental wave equivalent model of the CLLC resonant converter, the input impedance and gain expression of the CLLC resonant converter with uniform forward and reverse directions is expressed by k, b, Q and omega as follows:
Figure BDA0003467992530000071
Figure BDA0003467992530000072
in the formula, ZinuRepresenting the input impedance which is uniform in forward and reverse directions; muRepresenting a uniform voltage gain in forward and reverse directions; reRepresenting the forward and reverse equivalent resistance.
Step 3, analyzing the influence of k, b and Q on the input impedance angle and the voltage gain, and obtaining the selection principle and the range of k, b and Q, wherein the selection principle specifically comprises the following steps:
k. b, the influence of Q on the positive and negative input impedance and the voltage gain is as follows: the smaller k is, the larger gain range is obtained, the narrower frequency adjustment range is, and two peaks do not appear, but the soft switching range is narrowed, the lower the efficiency of the converter is, and since the forward and reverse k is positive correlation, the k should be as large as possible under the condition of ensuring the forward and reverse voltage gain, the soft switching range and the single peak. b is smaller, the obtained voltage gain is higher, the gain curve is steeper, the soft switch range is wider, but two peak values can appear, because b is reciprocal from front to back, b is smaller in one direction, and 1/b in the other direction is larger, therefore, both the front and the back need to be considered when selecting, and b is better to be close to 1. The smaller Q, the higher the voltage gain is obtained, the steeper the gain curve at ω <1, and the slower the gain curve at ω >1, the wider the soft switching range, and no two peaks occur.
The selection principle and the range of k, b and Q are as follows: the reduction in Q has a significant effect on gain and a small effect on the input impedance angle relative to the reduction in k and b, so it was first determined that Q ranges from 0 to 0.5. Since b in forward and backward directions are reciprocal, the maximum gain in forward direction is smaller than the maximum gain in backward direction, and b should be greater than 1, so that Q isrThe value will be greater than QfSmall, making the reverse maximum voltage gain larger, generally b ranges from 0.8 to 1.25. Although a reduction in k also contributes to an improvement in voltage gain, k cannot be too small, and the range of k is 3 to 8.
Step 4, determining converter parameter indexes, transformer turn ratio and forward and reverse gain ranges according to design requirements;
determining the input voltage V according to the design requirementinOutput voltage range Vomin～VomaxResonant frequency omegarOutput voltage V at resonant frequencyoPrimary and secondary of power P, transformerThe side turn ratio n is Vin/VoForward gain range nVomin/Vin～nVomax/VinReverse gain range Vin/nVomax～Vin/nVomin。
Step 5, combining the forward and reverse input impedance angles, and linking the forward and reverse gain curves to design specific values of k, b and Q meeting the requirements of a bidirectional gain range and a soft switch, wherein the specific values comprise the following values;
in the range of k, b, Q, a set of initial values is selected as the specific values of the forward circuit factor and calculated to obtain the specific values of the reverse circuit factor. Substituting specific values of forward circuit factors into MuAnd ZinuDrawing the curve of forward gain, input impedance angle and normalized frequency omega, substituting the specific value of reverse circuit factor into MuAnd ZinuThe curve of the inverse gain, the input impedance angle and the normalized frequency ω is plotted. When the forward and reverse gain ranges, soft switching and single peak requirements can be simultaneously met, a specific set of values k, b and Q is obtained.
Step 6, according to the specific values of k, b and Q and the forward resonant frequency omegarfForward equivalent resistance RefCalculating to obtain resonance parameters of the CLLC resonance converter, which specifically comprises the following steps:
the formula of the resonance parameter of the CLLC resonant converter is:
Figure BDA0003467992530000081
in the formula, Lr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n represents the turn ratio of the primary side and the secondary side of the transformer of the CLLC resonant converter; omegarfRepresents a forward resonant frequency; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; k represents the inductance ratio in the unity circuit factor; b represents the capacitance ratio in the unity circuit factor; q represents a unity circuit factorMedium quality factor.
Fig. 3 is a forward and reverse equivalent circuit model of the CLLC resonant converter of the invention. L isr1、Lr2Is primary and secondary side resonance inductance, L, of a CLLC resonance convertermExciting inductance, C for CLLC resonant converter transformerr1、Cr2Is the primary and secondary side resonance capacitance of the CLLC resonance converter, n is the primary and secondary side turn ratio of the transformer of the CLLC resonance converter, +/-Vinf、±nVofFor positive input and output of square-wave voltage, R, of CLLC resonant converterefIs an equivalent resistor with a forward output resistor coupled to the primary side of the transformer. The secondary side resonance inductor, the capacitor and the output resistor of the transformer are coupled to the primary side, so that a forward equivalent circuit model of the CLLC resonance converter can be obtained. V + Vinr、±nVorFor inverting input and output square wave voltage, R, of CLLC resonant convertererIs an equivalent resistance of the inverted output resistance coupled to the secondary side of the transformer. The primary side resonance inductor, the capacitor and the output resistor of the transformer are coupled to the secondary side, so that an inverse equivalent circuit model of the CLLC resonance converter can be obtained.
FIG. 4 shows the gain M of the present inventionuAnd input impedance angle thetauAnd (3) a relation graph with the normalized frequency omega and the inductance ratio k, wherein b is 1.2, Q is 0.4, the variation range of the normalized frequency omega is 0-2, and k is 2, 4, 5, 10 and 50 respectively. It can be seen that: the smaller k, the larger voltage gain range is obtained, the narrower the frequency adjustment range with the same output voltage range, and two peaks do not occur. However, the smaller k, the narrower the soft switching range may be, and the lower the efficiency of the converter. Since the forward and reverse k are positively correlated, k should be as large as possible while ensuring reverse voltage gain, soft switching range, and single peak.
FIG. 5 gain M in the present inventionuAnd input impedance angle thetauAnd a graph of normalized frequency ω and capacitance ratio b, wherein k is 4, Q is 0.4, the normalized frequency ω varies from 0 to 2, and b is 0.6, 0.8, 1.2, 3, and 5, respectively. It can be seen that: the smaller b is, the higher voltage gain can be obtained, the steeper the voltage gain curve is, and the wider soft switching range is realizedAnd (5) enclosing. However, the smaller b is, two peak values will occur, and since b is reciprocal downward, the smaller b in one direction is, the larger 1/b in the other direction is, so that both forward and reverse directions need to be considered in selecting, and b is preferably close to 1.
FIG. 6 shows the gain M of the present inventionuAnd input impedance angle thetauAnd a relation graph of the normalized frequency omega and the quality factor Q, wherein k is 4, b is 1.2, the normalized frequency omega is within a range of 0-2, and Q is 0.3, 0.35, 0.375, 0.4 and 0.5 respectively. It can be seen that: the smaller Q, the higher voltage gain can be achieved as well, at ω<At 1, the steeper the voltage gain curve, at ω>1, the slower the voltage gain curve, while having a wider soft switching range, and no two peaks. However, in the case of circuit parameter determination, the larger the load, the larger the Q, so that in designing parameters, it is ensured that the voltage gain range, the soft switching range and the single peak requirement are still met under the condition of maximum load.
Fig. 7 shows the forward and reverse gain and input impedance angle of 0.375 as a function of the normalized frequency ω, where k is 3.6, b is 1.2, and Q is 0.375. Using 3.6, 1.2, 0.375 as a specific value of a set of forward circuit factors, a specific value of a set of reverse circuit factors of 4.3, 0.83, 0.3125 can be calculated. Substituting 3.6, 1.2, 0.375 into MuAnd ZinuDrawing the curve of the positive gain, the input impedance angle and the normalized frequency omega, and substituting 4.3, 0.83 and 0.3125 into MuAnd ZinuThe curve of the inverse gain, the input impedance angle and the normalized frequency ω is plotted. It can be seen that: the forward and reverse gain curves have only single peak value. It should be noted that when the frequency ω is normalized>ω1And a reverse normalized frequency omega>ω2In time, both the forward and reverse directions meet the requirements of soft switching.
The method provided by the invention can design the parameters of the CLLC resonant converter by linking the two-way gain curves, thereby avoiding a large amount of calculation and repeated iteration in the traditional design process and reducing the design difficulty of the parameters of the CLLC resonant converter. The bidirectional gain can reach a higher range, and the range of the bidirectional switching frequency can be reduced. When a high-performance switching device and a synchronous rectification equivalent ratio optimization scheme are combined, the CLLC resonant converter can obtain higher efficiency in bidirectional operation and has lower implementation cost.

Claims (8)

1. A method for designing bidirectional asymmetric operation parameters of a CLLC resonant converter is characterized by comprising the following steps:
(1) establishing a corresponding quantity relation of forward and reverse circuit factors, and expressing the quantity relation by using a uniform circuit factor inductance ratio k, a uniform circuit factor capacitance ratio b and a uniform quality factor Q;
(2) expressing a bidirectional unified input impedance and voltage gain expression of the CLLC resonant converter by using k, b, Q and normalized frequency omega according to a forward and reverse fundamental wave equivalent model of the CLLC resonant converter;
(3) analyzing the influence of k, b and Q on the bidirectional unified input impedance angle and voltage gain of the CLLC resonant converter, and obtaining the selection principle and range of k, b and Q;
(4) determining the input voltage V according to the design requirementinOutput voltage range Vomin～VomaxForward resonant frequency omegarfOutput voltage V at resonant frequencyoPower P, primary and secondary side turn ratio n of transformer as Vin/VoForward gain range nVomin/Vin～nVomax/VinReverse gain range Vin/nVomax～Vin/nVomin；
(5) Combining the forward and reverse input impedance angles, and designing specific values of k, b and Q meeting the requirements of a bidirectional gain range and soft switching by associating forward and reverse gain curves;
(6) according to specific values of k, b and Q and forward resonant frequency omegarfForward equivalent resistance RefAnd calculating to obtain the resonance parameters of the CLLC resonance converter.
2. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 1, wherein in the step (1), the forward and reverse resonant frequencies are set to be the same, and the corresponding relationship between the forward and reverse circuit factors is obtained as follows:
Figure FDA0003467992520000011
in the formula, kf、bf、QfDenotes the forward circuit factor, where kfRepresenting the ratio of excitation inductance to primary resonance inductance, bfRepresenting the ratio, Q, of the resonant capacitance coupled to the primary side resonant capacitancefRepresenting a forward quality factor; a isfRepresenting the ratio of the resonant inductance coupled to the primary side resonant inductance; k is a radical ofr、br、QrDenotes the inverse circuit factor, where krRepresenting the ratio of the excitation inductance coupled to the secondary resonance inductance, brRepresenting the ratio of the resonant capacitance coupled to the secondary side resonant capacitance, QrRepresenting an inverse quality factor; a isrRepresenting the ratio of the resonant inductance coupled to the secondary side resonant inductance.
3. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 2, wherein in the step (1), the expressions of the forward and reverse circuit factors are as follows:
Figure FDA0003467992520000021
in the formula, ωrfRepresents a forward resonant frequency; omegasRepresents the switching frequency; ω represents the normalized frequency; l isr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n represents the turn ratio of the primary side and the secondary side of the transformer of the CLLC resonant converter; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; voIndicates the forward directionA rated output voltage; p represents the output power; omegarrRepresents the inverse resonance frequency; rerAn equivalent resistance representing the coupling of the inverting output resistance to the secondary side of the transformer; vinRepresenting a nominal input voltage in the forward direction.
4. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 1, wherein in the step (2), the expressions of bidirectional uniform input impedance and voltage gain of the CLLC resonant converter are represented by k, b, Q and ω according to a forward and reverse fundamental wave equivalent model of the CLLC resonant converter as follows:
Figure FDA0003467992520000022
Figure FDA0003467992520000023
in the formula, ZinuRepresenting the input impedance which is uniform in forward and reverse directions; muRepresenting a uniform voltage gain in forward and reverse directions; reRepresenting the forward and reverse equivalent resistance.
5. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 1, wherein in step (3), the influence of k, b, Q on positive and negative input impedance angle and voltage gain is as follows:
the smaller k is, the larger the obtained gain range is, the narrower the frequency regulation range is, two peak values cannot appear, but the soft switching range is narrowed, the lower the efficiency of the converter is, and since the positive and negative k is positive correlation, the k is maximized under the condition that the positive and negative voltage gain, the soft switching range and the single peak value are ensured;
b is smaller, the obtained voltage gain is higher, the gain curve is steeper, the soft switch range is wider, but two peak values can appear;
the smaller Q, the higher the voltage gain is obtained, the steeper the gain curve at ω <1, and the slower the gain curve at ω >1, the wider the soft switching range, and no two peaks occur.
6. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 5, wherein in said step (3), the selection principles and ranges of k, b and Q are as follows: q ranges from 0 to 0.5; b ranges from 0.8 to 1.25, and when the forward maximum gain is smaller than the reverse maximum gain, b is greater than 1, and Q is obtained at the momentrLess than Qf(ii) a k ranges from 3 to 8.
7. The method according to claim 1, wherein in step (5), a set of initial values is selected as specific values of the forward circuit factor in the ranges of k, b and Q, and the specific values of the reverse circuit factor are calculated; substituting specific values of forward circuit factors into MuAnd ZinuDrawing the curve of forward gain, input impedance angle and normalized frequency omega, substituting the specific value of reverse circuit factor into MuAnd ZinuDrawing a curve of the reverse gain, the input impedance angle and the normalized frequency omega; when the forward and reverse gain ranges, soft switching and single peak requirements are simultaneously met, a specific set of values k, b and Q is obtained.
8. The method for designing bidirectional asymmetric operating parameters of a CLLC resonant converter according to claim 1, wherein in the step (6), the formula of the resonant parameters of the CLLC resonant converter is as follows:
Figure FDA0003467992520000031
in the formula, Lr1、Lr2Representing the primary and secondary side resonance inductances of the CLLC resonance converter; l ismRepresenting the excitation inductance of the CLLC resonance transformer; cr1、Cr2Representing the primary and secondary side resonance capacitances of the CLLC resonance converter; n denotes transformer of CLLC resonant converterPrimary and secondary turn ratios; omegarfRepresents a forward resonant frequency; refAn equivalent resistance representing a forward output resistance coupled to the primary side of the transformer; k represents the inductance ratio in the unity circuit factor; b represents the capacitance ratio in the unity circuit factor; q represents the quality factor in the unity circuit factor.
CN202210034991.XA 2022-01-13 2022-01-13 Method for designing bidirectional asymmetric operation parameters of CLLC resonant converter Pending CN114499206A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117614287A (en) * 2024-01-18 2024-02-27 浙江大学 CLLC circuit capable of realizing high gain utilization rate by adjusting parameter design
CN117937950A (en) * 2024-03-21 2024-04-26 国网浙江省电力有限公司杭州市钱塘区供电公司 Parameter optimization method based on three-phase CLLC resonant converter and converter

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117614287A (en) * 2024-01-18 2024-02-27 浙江大学 CLLC circuit capable of realizing high gain utilization rate by adjusting parameter design
CN117614287B (en) * 2024-01-18 2024-04-12 浙江大学 CLLC circuit capable of realizing high gain utilization rate by adjusting parameter design
CN117937950A (en) * 2024-03-21 2024-04-26 国网浙江省电力有限公司杭州市钱塘区供电公司 Parameter optimization method based on three-phase CLLC resonant converter and converter

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