CN114039494B - Bidirectional cll resonant converter and control method thereof - Google Patents

Bidirectional cll resonant converter and control method thereof Download PDF

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CN114039494B
CN114039494B CN202111445417.5A CN202111445417A CN114039494B CN 114039494 B CN114039494 B CN 114039494B CN 202111445417 A CN202111445417 A CN 202111445417A CN 114039494 B CN114039494 B CN 114039494B
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resonant
current
time
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bidirectional
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CN114039494A (en
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禹金标
白洪超
赵迎辉
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Shandong Ainuo Instrument Co Ltd
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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
    • H02M3/33569—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 several active switching elements
    • H02M3/33576—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 several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33584—Bidirectional converters
    • 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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  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a bidirectional cll resonant converter and a control method thereof, wherein the bidirectional cll resonant converter structurally comprises a first bus capacitor C9, a first H bridge, a resonant capacitor Cr, a high-frequency transformer T0, a resonant inductor Lr, a second H bridge and a second bus capacitor C10, wherein the resonant capacitor Cr, the high-frequency transformer T0 and the resonant inductor Lr form a resonant cavity. Compared with the prior art, the invention only adopts three power devices of the resonant capacitor Cr, the high-frequency transformer T0 and the resonant inductor Lr to form a resonant cavity, two groups of PWM waves with fixed duty ratio of 50% are used for driving, zero voltage switching-on of an inverter side switching tube and zero current switching-off of a rectifier side diode are realized by fewer power devices and a simple control method when the bidirectional CLL resonant converter operates bidirectionally, and the invention has the advantages of bidirectional operation, simple topology and control method, light weight, small volume, high power density and high efficiency.

Description

Bidirectional cll resonant converter and control method thereof
Technical Field
The invention relates to the technical field of power electronic soft switches, in particular to a high-frequency isolation resonance soft switch technology, and particularly provides a bidirectional cll resonance converter and a control method thereof.
Background
With the progress of science and technology, the high frequency, miniaturization, high efficiency and low noise of electronic products become important indexes. Although the current switching tube, such as a power MOSFET or an IGBT, develops rapidly and its performance and loss are gradually reduced, the hard switching loss is still a bottleneck of increasing the frequency and efficiency of the system.
Hard switching techniques can cause the switching devices to generate large switching losses, limiting the switching frequency of the switching devices, and also reducing the efficiency of the converter.
At present, the bidirectional isolation DC-DC converter is widely used in the test environments of micro-grid, battery charge and discharge test, energy storage and the like which relate to bidirectional flow of energy. The bidirectional high-frequency isolation DC-DC mostly uses a resonance conversion technology at present, but has the main problems that a plurality of resonance power devices exist, and the power density of a converter is limited; or the control method is complicated, the design difficulty is increased, and the reliability is reduced.
Disclosure of Invention
Aiming at the problems, the bidirectional high-frequency isolation resonant soft switching DC-DC converter and the control method thereof which have few resonant power devices and simple control method have higher research and application values.
The technical task of the present invention is to provide a bidirectional cll resonant converter and a control method thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
a bidirectional cll resonant converter structurally comprises a first bus capacitor C9, a first H bridge, a resonant capacitor Cr, a high-frequency transformer T0, a resonant inductor Lr, a second H bridge and a second bus capacitor C10, wherein the resonant capacitor Cr, the high-frequency transformer T0 and the resonant inductor Lr form a resonant cavity.
The first bus capacitor C9 is connected to the dc sides V1+ and V1 "of the first H-bridge,
the midpoint A of the left bridge arm of the first H bridge is connected with the resonance capacitor Cr,
the resonance capacitor Cr and the midpoint B of the right bridge arm of the first H bridge are connected with the primary side of the high-frequency transformer T0,
the secondary side of the high-frequency transformer T0 is connected with the middle point C of the right arm of the second H bridge and the resonant inductor Lr,
the resonance inductor Lr is connected with the middle point D of the left bridge arm of the second H bridge,
the direct current sides V2+ and V2-of the second H bridge are connected with the second bus capacitor C10.
In another aspect, the present invention provides a bidirectional cll resonant converter control method, where the method is implemented by:
when the bidirectional CLL resonant converter works in the forward direction, the first H bridge works in an inversion state, the second H bridge works in a rectification state, and energy flows from V1 to V2;
when the bidirectional CLL resonant converter works reversely, the first H bridge works in a rectification state, the second H bridge works in an inversion state, and energy flows from V2 to V1.
The driving mode of the bidirectional cll resonant converter is two groups of PWM waves with fixed frequency and 50% duty ratio, the structure of the first H bridge comprises left arm switching tubes T1 and T2 and right arm switching tubes T3 and T4, the structure of the second H bridge comprises left arm switching tubes T5 and T6 and right arm switching tubes T7 and T8, wherein the driving signals of T1, T4, T6 and T7 are the same, the driving signals of T2, T3, T5 and T8 are the same, and the two groups of drives are in complementary conduction, as shown in FIG. 2.
When the bidirectional CLL resonant converter works in the forward direction, the equivalent model is a Type-11 model, as shown in FIG. 3, and the equivalent model comprises the following components: the high-frequency transformer primary side excitation inductance equivalent alternating current power supply comprises a resonant capacitor Cr, a high-frequency transformer primary side excitation inductance Lm _ P, an equivalent resonant inductance Lr _ eq _ P and an equivalent alternating current impedance Rac _ eq _ P, wherein Lr _ eq _ P is the equivalent resonant inductance equivalent to the primary side of the transformer when the resonant inductance Lr works in the forward direction, and Rac _ eq _ P is the equivalent alternating current impedance equivalent to the inverter side of a secondary side circuit when the secondary side circuit works in the forward direction.
The structure after equivalent transformation according to the equivalent model when the bidirectional CLL resonant converter works in the forward direction comprises the following steps:
l2 is Lr _ eq _ P, and the resonant inductor Lr is equivalent to the equivalent resonant inductor on the primary side of the transformer when the transformer works in the forward direction;
l1 ═ Lm _ P, primary side excitation inductance of the high frequency transformer;
the current through the resonant capacitor Cr is ic,
the current flowing through the primary side excitation inductor L1 of the high-frequency transformer is i1,
the current flowing through L2 is i2, the current flowing through diode D5 is i5, and the current flowing through diode D7 is i 7.
The modes of the bidirectional CLL resonant converter in the forward operation are shown in FIGS. 4a to 4 h:
analyzing the working state when i1 is positive, the forward working mode of the bidirectional CLL resonant converter is as follows:
stage t3-t4, FIG. 4 b: t1, T4, T6 and T7 are turned on, ic is decreased in the positive direction after passing a peak value, and at the time T4, ic is equal to i 1; i1 increases in positive direction after zero crossing, ic is i1+ i2, t4 is i1 is ic, i2 is 0;
time t4, FIG. 4 c: i1 ═ ic, i2 ═ 0, D6, D7 zero current turn off, T6T7 is always on, V2 and C10 start discharging, the secondary winding of the transformer starts excitation, and current is generated;
stage t4-t5, FIG. 4 d: the reverse excitation of the transformer causes the negative increase of i2 after zero crossing, the secondary side temporarily feeds back energy to the inversion side, the magnitude of the reverse current is, ic continuously decreases, i1 is ic + i 2;
at time t5, ic is 0, i1 is i 2;
stage t5-t6, as in FIG. 4 e: i1 continues to increase, is increases due to negative increase after ic zero crossing, i2, i7 increase negatively;
at the time T6, T1, T4, T6 and T7 are turned off, ic and i2, i7 reach a negative transient peak, and T6T7 is turned off hard;
stage t6-t8, FIG. 4 f: (the change rule of ic is that firstly the negative direction is reduced to zero, then the positive direction is increased, and finally the positive direction is reduced to zero.) the dead zone T1T4 is entered, the is converted to D5D8 after T6T7 is turned off, and the reduction is started; i2 decreases negatively therewith; meanwhile, ic decreases negatively, decreasing to zero at time t7, and then increasing positively (due to L1> > L2, at this time i1> > i2, so i1 will be charged by C1C4 and C2C3 will be discharged, causing ic to increase positively);
stage t8-t9, FIG. 4 g: after the charging and discharging of the C1-C4 capacitor are finished (D2D 3 follow current can be realized only when the dead time is larger than the charging and discharging time), ic starts to follow current through the D2D3, and preparation is made for T2T3 to be switched on to realize zero voltage;
stage t9-t10, FIG. 4 h: and zero voltage is switched on at the time T2T3 and T5T8 at T9, so that ZVS is realized.
In summary, during the forward operation, the zero-voltage switching-on of the rectifier-side and inverter-side switching tubes T2, T3, T5 and T8 and the zero-current switching-off of the rectifier-side diodes D6 and D7 occur.
The equivalent model of the bidirectional CLL resonant converter in reverse operation is a Type-4 model, as shown in FIG. 5a and FIG. 5 b. The structure includes: the resonant inductor Lr, the secondary equivalent excitation inductor Lm _ N of the high-frequency transformer, the equivalent resonant capacitor Cr _ eq _ N and the equivalent alternating-current impedance Rac _ eq _ N, wherein: cr _ eq _ N is an equivalent resonant capacitor equivalent to the secondary side of the transformer by the resonant inductor Cr in reverse operation, and Rac _ eq _ N is an equivalent alternating current impedance equivalent to the inverter side by the primary side circuit of the transformer in reverse operation.
As shown in fig. 6a and fig. 6b, under the inverse equivalent model, the inverse operation equivalent topology is transformed into:
the resonant tank resonant elements are Cr _ eq _ N, Lr, Lm _ N when the excitation inductance is added to resonance, Cr _ eq _ N, Lr when the excitation inductance is clamped, the converter having two resonant frequencies:
first resonance frequency:
Figure BDA0003384742740000031
the second resonant frequency is:
Figure BDA0003384742740000032
the reverse working mode of the bidirectional CLL resonant converter is shown in fig. 7a to 7 f:
mode 1 is time T0-T1, as shown in fig. 7b, wherein at time T0, the driving voltages T1, T4, T6 and T7 become high level, and at this time, T6 and T7 start to be turned on; the resonant tank input voltage VCD leads the resonant current ic, the direction of the ic current is consistent with the previous mode, ic is negative, the resonant current ic is transferred from the body diode to the switch body and flows through the switch T6T7 in the reverse direction; the rectified side current is transferred from the body diode D1D4 to the switch body and flows in the reverse direction through the switch T1T 4;
t1 and T4 are conducted, an excitation inductor Lm _ N is clamped by the voltage of the secondary end of the transformer, the change rate of an excitation current iLM is positive, the resonance tank consists of Lr and Cr _ eq _ N, and the resonance frequency of the circuit is f 1;
mode 2 is time T1-T2, as shown in fig. 7c, wherein at time T1, the driving voltages T1, T4, T6 and T7 become high level, and at this time T6 and T7 start to conduct; resonant current ic decreases back to zero and begins to increase from zero forward, resonant current ic flowing through switch T6T7 in the forward direction; the transformer secondary end sides T1 and T4 are conducted, the excitation inductance Lm _ N is clamped by the transformer secondary end voltage, the change rate of the excitation current iLM is positive, the resonance tank consists of Lr and Cr _ eq _ N, and the circuit resonance frequency is f 1;
the mode 3 is from time t2 to time t3, as shown in fig. 7d, wherein at time t2, the direction of the exciting current iLM changes to the positive direction under the action of the primary voltage; the transformer secondary end side T1 and T4 are conducted, the excitation inductance Lm _ N is still clamped by the transformer secondary end voltage, the change rate of the excitation current iLM is positive, the resonance tank consists of Lr and Cr _ eq _ N, and the circuit resonance frequency is f 1; at the time T3, the resonant current ic changes to be consistent with the exciting current iLM in a sinusoidal mode, and the current ID1 or T1 flowing through T1 is reduced to zero;
the mode 4 is the time from T3 to T4, as shown in fig. 7e, in this mode, the resonant current ic and the exciting inductor current iLM are kept equal, the primary end current of the transformer drops to 0, the body diodes of the rectifier side T1 and T4 stop conducting, the rectifier switch realizes zero current turn-off, and the load energy is provided by the voltage stabilizing capacitor; the switching tube at the side of the secondary end stops conducting, the clamping effect of the reflected voltage of the output voltage on the excitation inductor disappears, Lm _ N starts to add resonance, the resonance groove consists of Lm _ N, Lr and Cr _ eq _ N, the resonance frequency of the circuit is f2, and meanwhile, the second resonance period is much larger than the first resonance period, so that the resonance current changes little in the mode;
the mode 5 is a time T4-T5, as shown in fig. 7f, at the time T4, T1, T4, T6 and T7 are turned off, the process is hard turn off, the circuit enters a dead time, the resonant current ic charges the body capacitors C6 and C7, C5 and C8 are discharged, after the charging and discharging of the body capacitors are finished, D5 and D8 freewheel, at the time T5, T2, T3, T5 and T8 are turned on, and the inverter sides T5 and T8 realize zero-voltage turn-on;
after the time T4, ic is reduced faster than iLM, the current is on the rectifying side is reversely increased, the bulk capacitors C1 and C4 are charged, C2 and C3 are discharged, after the capacitors are charged and discharged, D2 and D3 follow currents, T2, T3, T5 and T8 are switched on at the time T5, and zero-voltage switching on the rectifying sides T2 and T3 is achieved; lm _ N exits the resonant cavity after D2 and D3 freewheel, and the change rate of the exciting current iLM becomes negative.
In summary, during reverse operation, the inverter sides T5 and T8 achieve zero voltage turn-on, and the rectifier sides T2 and T3 achieve zero voltage turn-on. The rectifier side diode achieves zero current turn-off.
The bidirectional CLL resonant converter can realize zero-voltage switching-on of switching tubes on an inversion side and a rectification side in forward operation and reverse operation. The rectifier side diode achieves zero current turn-off.
Compared with the prior art, the bidirectional cll resonant converter and the control method thereof have the following outstanding beneficial effects:
the invention is mainly used for designing the high-frequency isolation DC-DC converter, in particular to the design of a bidirectional high-frequency isolation resonance soft switching converter, realizes high-frequency, bidirectional operation and soft switching, and improves the efficiency, power density and reliability of the converter. Compared with the prior art, the invention only adopts three power devices of the resonant capacitor Cr, the high-frequency transformer T1 and the resonant inductor Lr to form a resonant cavity, two groups of PWM waves with fixed duty ratio of 50% are used for driving, zero voltage switching-on of an inverter side switching tube and zero current switching-off of a rectifier side diode are realized by fewer power devices and a simple control method when the bidirectional CLL resonant converter operates bidirectionally, and the invention has the advantages of bidirectional operation, simple topology and control method, light weight, small volume, high power density and high efficiency.
Drawings
FIG. 1 is a topology diagram of a bidirectional CLL resonant converter of the present invention;
FIG. 2 is a driving scheme of the bidirectional CLL resonant converter of the present invention;
FIG. 3 is a forward working equivalent model of the bidirectional CLL resonant converter of the present invention;
FIGS. 4a-h are diagrams of forward operating modes of the bidirectional CLL resonant converter of the present invention;
5a-b are equivalent models of the reverse operation of the bidirectional CLL resonant converter of the present invention;
6a-b are reverse run equivalent topologies of the present invention;
FIGS. 7a-f are diagrams of reverse operation modes of the bidirectional CLL resonant converter of the present invention;
FIG. 8 is a diagram of the impedance characteristic of the resonant cavity for the reverse operation of the bidirectional CLL resonant converter of the present invention;
FIG. 9 is matlab simulation waveforms of drive and current for the bi-directional CLL resonant converter of the present invention in forward operation;
fig. 10 is matlab simulation waveforms of drive and current for the bi-directional CLL resonant converter of the present invention operating in reverse.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, a bidirectional CLL resonant converter and a control method thereof, as shown in fig. 1, includes:
the high-frequency transformer comprises a first bus capacitor C9, a first H bridge, a resonant capacitor Cr, a high-frequency transformer T1, a resonant inductor Lr, a second H bridge and a second bus capacitor C10.
The first bus capacitor C9 is connected with the DC sides V1+ and V1-of the first H bridge, the midpoint A of the left bridge arm of the first H bridge is connected with the resonance capacitor Cr, the resonance capacitor Cr and the midpoint B of the right bridge arm of the first H bridge are connected with the primary side of the high-frequency transformer T0, the secondary side of the high-frequency transformer is connected with the midpoint C of the right bridge arm of the second H bridge and the resonance inductor Lr, the resonance inductor Lr is connected with the midpoint D of the left bridge arm of the second H bridge, and the DC sides V2+ and V2-of the second H bridge are connected with the second bus capacitor C10. The resonant capacitor Cr, the high-frequency transformer T0 and the resonant inductor Lr form a resonant cavity.
When the bidirectional CLL resonant converter works in a forward direction, the first H bridge works in an inversion state, the second H bridge works in a rectification state, and energy flows from V1 to V2. When the bidirectional CLL resonant converter works reversely, the first H bridge works in a rectification state, the second H bridge works in an inversion state, and energy flows from V2 to V1.
As shown in fig. 2, the driving method: the drive is two sets of PWM waves with fixed frequency and 50% duty ratio. The T1, T4, T6 and T7 driving signals are the same, and the T2, T3, T5 and T8 driving signals are the same. The two sets of drives are in complementary conduction.
Specifically, during forward operation, based on a fundamental wave analysis method and the like, as shown in fig. 3, the equivalent parameters are:
Figure BDA0003384742740000061
lr _ eq _ P: the resonant inductor Lr is equivalent to the equivalent resonant inductor of the primary side of the transformer when the transformer works in the forward direction;
n: the transformation ratio between the primary side and the secondary side of the transformer is obtained;
Figure BDA0003384742740000062
rac _ eq _ P: when the circuit runs in the forward direction, the rectification side circuit is equivalent to the equivalent alternating current impedance of the inversion side.
R Ld The equivalent direct current load on the rectifying side is operated in the forward direction.
Figure BDA0003384742740000063
V2: a second H-bridge DC side voltage.
Pout: and the DC side of the second H bridge outputs power.
Cr is a resonance capacitor, Lm _ P is a primary side excitation inductance of the high-frequency transformer. And Lr _ eq _ P is equivalent resonance inductance of the primary side of the transformer equivalent to the resonance inductance Lr in forward operation. Rac _ eq _ P is equivalent alternating-current impedance of a secondary side circuit equivalent to an inverter side when the circuit operates in the forward direction.
Defining the ratio of the excitation inductance and the resonance inductance as:
Figure BDA0003384742740000064
normalized switching frequency:
Figure BDA0003384742740000065
the figure of merit is defined as:
Figure BDA0003384742740000066
characteristic impedance:
Figure BDA0003384742740000071
characteristic frequency:
Figure BDA0003384742740000072
the transfer function of a bidirectional CLL resonant converter in forward operation is:
Figure BDA0003384742740000073
ω s ＝2πf s
when the bidirectional CLL resonant converter operates in a forward direction, the direct current gain is as follows:
Figure BDA0003384742740000074
calculating design parameters of a resonant cavity:
calculating the resonance capacitance:
Figure BDA0003384742740000075
and (3) when the transformer works in the forward direction, the resonance inductance Lr is equivalent to the equivalent resonance inductance of the primary side of the transformer for calculation:
Figure BDA0003384742740000076
calculating the resonance inductance:
L r ＝Lr_eq_P/n 2
after design parameters of U1, Pout, n, switching frequency fs and normalized frequency fn are determined, k is 25.6, and Q is 0.21, so that design values of resonant cavity design parameters Cr and Lr can be obtained.
Example 2
Taking a bidirectional CLL resonant converter design with output power Pout of 5000W, U1 of 770V, U2 of 600V, switching frequency fs of 125kHz, transformer transformation ratio n of 1.28, and normalization parameter fn of 0.95 as an example, k of 25.6 and Q of 0.21 are taken for calculation, and the design parameters of the bidirectional CLL resonant converter are as follows:
item Name (R) Unit of Parameter(s)
Input voltage U1 V 770
Diode conduction voltage drop V F V 1.400
Output power Po kW 5
Output voltage U2 V 600
Excitation inductance Lm_P uH 625.97
Primary equivalent resonance inductor Lr_eq_P uh 24.45
Secondary side resonance inductor L r uh 14.85
Load resistance R o Ω 72.000
Resonance capacitor C r nF 62.23
Frequency of operation f s kHz 125.00
Resonant frequency f r kHz 131.58
Transformation ratio of transformer n 1.28
Quality factor Q 0.21
Ratio of inductances k(λ) 25.60
Normalized switching frequency f n 0.950
Equivalent load resistor at primary end of transformer Rac_eq_P Ω 96.21
Duty cycle T r us 8.000
Dead time T dead ns 750
And (3) checking whether the reverse operation works in the inductive area:
equivalent resonant capacitance in reverse operation: cr _ eq _ N ═ N 2 C r ＝125nf
Equivalent alternating current impedance in reverse operation:
Figure BDA0003384742740000081
ratio of equivalent excitation inductance to resonance inductance in reverse operation:
Figure BDA0003384742740000082
quality factor Q corresponding to the inductive and capacitive boundary res Comprises the following steps:
Figure BDA0003384742740000091
equivalent resonant frequency in reverse operation:
Figure BDA0003384742740000092
the figure of merit for reverse full power operation is:
Figure BDA0003384742740000093
from the above verification analysis:
f s ＜f r2
Q 5kw_2 ＜Q res2
as shown in fig. 8, the reverse operation meets the requirement of working in perceptual region @.
The example meets the design requirement, and the final designed resonance parameters of the bidirectional CLL resonant converter required in the table are Cr-62.23 nf, Lr-14.85 uH and Lm-625.97 uH.
In order to verify the effectiveness of the invention, a simulation experiment is carried out on a model built in Matlab/Simulink, and the correctness of current and driving waveform of the bidirectional CLL resonant converter in forward operation and reverse operation and the forming process of a soft switch are verified. As shown in fig. 9, it is matlab simulation waveform of driving and current when the bidirectional CLL resonant converter of the present invention works in forward direction; fig. 10 shows matlab simulation waveforms of driving and current when the bidirectional CLL resonant converter of the present invention operates in reverse.
The above-described embodiments are merely preferred embodiments of the present invention, and general changes and substitutions by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.

Claims (4)

1. A control method of a bidirectional cll resonant converter is characterized in that,
the bidirectional cll resonant converter structurally comprises a first bus capacitor C9, a first H bridge, a resonant capacitor Cr, a high-frequency transformer T0, a resonant inductor Lr, a second H bridge and a second bus capacitor C10, wherein the resonant capacitor Cr, the high-frequency transformer T0 and the resonant inductor Lr form a resonant cavity;
the first bus capacitor C9 is connected to the dc sides V1+ and V1 "of the first H-bridge,
the midpoint A of the left bridge arm of the first H bridge is connected with one end of the resonant capacitor Cr,
the other end of the resonance capacitor Cr and the midpoint B of the right bridge arm of the first H bridge are respectively connected with two ends of the primary side of the high-frequency transformer T0,
two ends of the secondary side of the high-frequency transformer T0 are respectively connected with the middle point C of the right bridge arm of the second H bridge and one end of the resonant inductor Lr,
the other end of the resonant inductor Lr is connected with the midpoint D of the left bridge arm of the second H bridge,
the direct current sides V2+ and V2-of the second H bridge are connected with the second bus capacitor C10;
when the bidirectional CLL resonant converter works in the forward direction, the first H bridge works in an inversion state, the second H bridge works in a rectification state, and energy flows from V1 to V2;
when the bidirectional CLL resonant converter works reversely, the first H bridge works in a rectification state, the second H bridge works in an inversion state, and energy flows from V2 to V1;
the bidirectional cll resonant converter is driven by two groups of PWM waves with fixed frequency and 50% duty ratio, the first H bridge comprises left bridge arm switching tubes T1 and T2 and right bridge arm switching tubes T3 and T4, the second H bridge comprises left bridge arm switching tubes T5 and T6 and right bridge arm switching tubes T7 and T8, wherein T1, T4, T6 and T7 are driven by the same signals, T2, T3, T5 and T8 are driven by the same signals, and the two groups of drives are in complementary conduction;
the switch tubes T1-T8 are respectively provided with body diodes D1-D8 and body capacitors C1-C8;
when the bidirectional CLL resonant converter works in the forward direction, the equivalent model is a Type-11 model, and the equivalent model comprises the following components: the resonant inductor comprises a resonant capacitor Cr, a primary side excitation inductor Lm _ P of a high-frequency transformer T0, an equivalent resonant inductor Lr _ eq _ P and an equivalent alternating current impedance Rac _ eq _ P, wherein Lr _ eq _ P is the equivalent resonant inductor of the resonant inductor Lr equivalent to the primary side of the transformer when working in the forward direction, and Rac _ eq _ P is the equivalent alternating current impedance of a secondary side circuit equivalent to the inversion side when working in the forward direction;
the structure after equivalent transformation according to the equivalent model when the bidirectional CLL resonant converter works in the forward direction comprises the following steps:
l2 is Lr _ eq _ P, and the resonant inductor Lr is equivalent to the equivalent resonant inductor on the primary side of the transformer T0 when the transformer operates in the forward direction;
l1 ═ Lm _ P, primary side excitation inductance of high frequency transformer T0;
cr, resonant capacitance;
the current through the resonant capacitor Cr is ic,
the current flowing through the primary side excitation inductor L1 of the high-frequency transformer T0 is i1,
the current flowing through L2 is i2, the current flowing through diode D5 is i5, and the current flowing through diode D7 is i 7;
the bidirectional CLL resonant converter has the following modes in forward working:
analyzing the working state when i1 is positive, the forward working mode of the bidirectional CLL resonant converter is as follows:
stage t3-t 4: t1, T4, T6 and T7 are turned on, ic is decreased in the positive direction after passing a peak value, and at the time T4, ic is equal to i 1; i1 increases in the positive direction after zero crossing, ic is i1+ i2, i1 is ic at time t4, i2 is 0;
time t 4: i1 ═ ic, i2 ═ 0, D6, D7 zero current turn off, T6T7 is always on, V2 and C10 start discharging, the secondary winding of the transformer starts excitation, and current is generated;
stage t4-t 5: the negative increase of i2 after zero crossing is caused by the reverse excitation of the transformer, the short-time energy feedback of the secondary side to the inversion side is realized, the magnitude of the reverse current is, ic is continuously reduced, and i1 is ic + i 2;
at time t5, ic is 0, i1 is i 2;
stage t5-t 6: i1 continues to increase, is increases due to negative increase after ic zero crossing, i2, i7 increase negatively;
at the time T6, T1, T4, T6 and T7 are turned off, ic and i2, i7 reach a negative transient peak, and T6T7 is turned off hard;
stage t6-t 8: entering a dead zone T1T4, switching off the is after T6T7, converting to D5D8, and starting to reduce; i2 decreases negatively therewith; at the same time, ic decreases negatively, decreasing to zero at time t7, and then increases positively;
stage t8-t 9: after the C1-C4 capacitor finishes charging and discharging, ic starts to follow current through D2D3 to prepare for T2T3 to realize zero voltage;
stage t9-t 10: and zero voltage is switched on at the time T2T3 and T5T8 at T9, so that ZVS is realized.
2. The method of claim 1, wherein the step of controlling the bidirectional cll resonant converter comprises,
when two-way CLL resonant converter reverse work equivalent model is Type-4 model, its structure includes: the resonant inductor Lr, the secondary equivalent excitation inductor Lm _ N of the high-frequency transformer T0, the equivalent resonant capacitor Cr _ eq _ N, and the equivalent alternating-current impedance Rac _ eq _ N, wherein: cr _ eq _ N is an equivalent resonant capacitor equivalent to the secondary side of the transformer by the resonant capacitor Cr in reverse operation, and Rac _ eq _ N is an equivalent alternating current impedance equivalent to the inverter side by the primary side circuit of the transformer in reverse operation.
3. The method of claim 2, wherein the step of controlling the bidirectional cll resonant converter comprises,
under the reverse equivalent model, the reverse operation equivalent topology is transformed into: the resonant tank resonant elements are Cr _ eq _ N, Lr, Lm _ N when the excitation inductance is added to resonance, Cr _ eq _ N, Lr when the excitation inductance is clamped, the converter having two resonant frequencies:
first resonance frequency:
Figure FDA0003762116550000031
the second resonant frequency is:
Figure FDA0003762116550000032
4. the control method of the bidirectional CLL resonant converter of claim 3, wherein the reverse operation mode of the bidirectional CLL resonant converter is as follows:
the mode 1 is time T0-T1, wherein at time T0, the driving voltages of T1, T4, T6 and T7 become high level, and at this time, T6 and T7 start to be conducted; the resonant tank input voltage VCD leads the resonant current ic, ic current direction and V CD The modes at the end of the negative half period are consistent, ic is negative, and the resonant current ic is transferred from the body diode to the switch body and flows through the switch tube T6T7 in the reverse direction; the rectified side current is transferred from the body diode D1D4 to the switch body and flows through the switch tube T1T4 in the reverse direction;
t1 and T4 are conducted, an excitation inductor Lm _ N is clamped by the secondary side voltage of the transformer, the change rate of an excitation current iLM is positive, the resonance tank consists of Lr and Cr _ eq _ N, and the resonance frequency of the circuit is f 1;
the mode 2 is time T1-T2, wherein at time T1, the driving voltages T1, T4, T6 and T7 become high level, and at this time, T6 and T7 start to be conducted; the resonant current ic decreases reversely to zero and starts to increase from zero in a forward direction, and the resonant current ic flows through the switch tube T6T7 in the forward direction; the transformer secondary side T1 and T4 are conducted, the excitation inductor Lm _ N is clamped by the transformer secondary side voltage, the change rate of the excitation current iLM is positive, the resonance tank consists of Lr and Cr _ eq _ N, and the circuit resonance frequency is f 1;
the mode 3 is a time t2-t3, wherein at the time t2, the direction of an exciting current iLM is changed into a positive direction under the action of a primary voltage; the secondary sides T1 and T4 of the transformer are conducted, the excitation inductor Lm _ N is still clamped by the secondary side voltage of the transformer, the change rate of the excitation current iLM is positive, the resonant tank consists of Lr and Cr _ eq _ N, and the resonant frequency of the circuit is f 1; at the time T3, the resonant current ic changes to be consistent with the exciting current iLM in a sinusoidal mode, and the current ID1 or T1 flowing through T1 is reduced to zero;
the mode 4 is a time from T3 to T4, in the mode, the resonant current ic and the exciting current iLM are kept equal, the primary side current of the transformer is reduced to 0, the body diodes of the rectifier side T1 and the rectifier side T4 stop conducting, the rectifier side diodes D1 and D4 realize zero current turn-off, and the load energy is provided by a voltage stabilizing capacitor; the switching tube on the secondary side stops conducting, the clamping effect of the reflected voltage of the output voltage on the excitation inductor disappears, Lm _ N starts to add resonance, the resonance groove consists of Lm _ N, Lr and Cr _ eq _ N, the resonance frequency of the circuit is f2, and meanwhile, the second resonance period is much larger than the first resonance period, so that the resonance current changes little in the mode;
the mode 5 is a time T4-T5, wherein at a time T4, T1, T4, T6 and T7 are turned off, the process is hard turn off, a circuit enters dead time, resonant current ic charges body capacitors C6 and C7, C5 and C8 are discharged, after charging and discharging of the body capacitors are finished, D5 and D8 freewheel, at a time T2, T3, T5 and T8 are turned on at a time T5, and zero-voltage turn-on is realized at inverter sides T5 and T8;
after the time T4, ic is reduced faster than iLM, the current is on the rectifying side is reversely increased, the bulk capacitors C1 and C4 are charged, C2 and C3 are discharged, after the capacitors are charged and discharged, D2 and D3 follow currents, T2, T3, T5 and T8 are switched on at the time T5, and zero-voltage switching on the rectifying sides T2 and T3 is achieved; lm _ N exits the resonant cavity after D2 and D3 freewheel, and the change rate of the exciting current iLM becomes negative.
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