CN112202336B - Control method of bidirectional CLLLC type converter capable of automatically switching power directions - Google Patents

Control method of bidirectional CLLLC type converter capable of automatically switching power directions Download PDF

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CN112202336B
CN112202336B CN202010982941.5A CN202010982941A CN112202336B CN 112202336 B CN112202336 B CN 112202336B CN 202010982941 A CN202010982941 A CN 202010982941A CN 112202336 B CN112202336 B CN 112202336B
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switch tube
primary side
resonant
tube
switching
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CN112202336A (en
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康龙云
赵子先
张健彬
于玮
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South China University of Technology SCUT
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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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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

Abstract

The invention discloses a control method of a bidirectional CLLLC type converter with automatically switchable power directions, which enables the switching-on time of a switching tube at one side of a transformer to be always kept in a half resonance period, and one bridge arm switching tube at the other side of the transformer is added with corresponding phase shift along with the change of frequency, so that the converter realizes the smooth switching of the power flow directions on the basis of maintaining the soft switching characteristics, and when the voltage at the load side is higher than the output voltage, the power flow is automatically reversed. In the method, the voltage regulation mode is frequency conversion and voltage regulation, the converter is divided into a boosting mode and a voltage reduction mode, and the circuit topology has high symmetry, so that the forward and reverse current waveforms are symmetrical in the boosting mode, the boosting forward running characteristic is the same as the voltage reduction reverse running characteristic, and the boosting reverse running characteristic is the same as the voltage reduction forward running characteristic, and the zero-voltage conduction of the switching tube on one side and the zero-current turn-off of the switching tube on the other side can be realized in any mode.

Description

Control method of bidirectional CLLLC type converter capable of automatically switching power directions
Technical Field
The invention relates to the technical field of bidirectional resonant DC-DC converters, in particular to a control method of a bidirectional CLLLC converter with automatically switchable power direction.
Background
With the rapid development of new energy, electric vehicles, direct-current micro-grids and other technologies, the application of the bidirectional DC-DC converter is more and more extensive, and the bidirectional resonant DC-DC converter has the advantages of simple structure, good soft switching performance and the like, and is widely concerned. When the bidirectional LLC resonant DC-DC converter operates in the forward direction, the good operation characteristic of an LLC circuit under the traditional unidirectional control can be kept, but the bidirectional LLC resonant DC-DC converter degenerates into LC series resonance when operating in the reverse direction, the voltage gain is always smaller than 1, and the bidirectional LLC resonant DC-DC converter can only operate in a voltage reduction mode. In order to enable the circuit to be capable of boosting to operate in a reverse direction, a scholars proposes an asymmetric CLLC resonant cavity structure, namely a resonant capacitor is added on a secondary side, so that although the forward and reverse operation can keep the characteristics of the LLC circuit, the design difficulty of the circuit and a controller is greatly increased due to the asymmetry of the circuit structure. In order to obtain a symmetrical resonant cavity structure, a student adds a resonant inductor and a resonant capacitor on the secondary side of a transformer, and the obtained bidirectional CLLLC resonant DC-DC converter has completely symmetrical forward and reverse operation characteristics, so that the difficulty of circuit design and controller design is greatly reduced, the advantage that LLC resonance can be maintained during forward and reverse operation is achieved, and the efficiency is high.
However, the control method of the bidirectional CLLLC resonant DC-DC converter is generally single-side frequency modulation control, the secondary side is in an uncontrolled rectification or synchronous rectification state, and power can only flow from the primary side to the secondary side under normal operation, which makes the bidirectional CLLLC circuit unable to realize smooth switching of power under the traditional frequency modulation control and requires an additional control strategy.
Disclosure of Invention
The invention aims to solve the problem that the power flow direction of the traditional CLLLC circuit can not be automatically switched under the traditional control, and provides a control method of a bidirectional CLLLC type converter with the power direction capable of being automatically switched. In both the boosting mode and the voltage reduction mode, when the voltage on the load side is greater than the output voltage of the resonant cavity, the flow direction of the power can be automatically reversed without shutdown switching.
The purpose of the invention can be achieved by adopting the following technical scheme:
a control method of a bidirectional CLLLC type converter with automatically switchable power direction is applied to a bidirectional CLLLC resonant DC-DC converter topology, and the topology comprises a primary side first switch tube S1Primary side second switch tube S2Third switch tube S on primary side3Primary side fourth switch tube S4And a fifth secondary switch tube S5And a sixth secondary switch tube S6And a seventh secondary switch tube S7And the eighth secondary switch tube S8Primary side first resonant inductor Lr1Primary side first resonance capacitor Cr1And an excitation inductor LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2And a high-frequency transformer connected with the primary side and the secondary side, wherein the primary side is provided with a first switch tube S1Primary side second switch tube S2A primary side left bridge arm and a primary side third switch tube S are formed by connecting in series3Fourth switch tube on primary sideS4The primary side right bridge arm is formed by connecting in series; secondary side fifth switch tube S5And a sixth secondary switch tube S6A secondary-side left bridge arm and a secondary-side seventh switching tube S are formed by connecting in series7And the eighth secondary switch tube S8A secondary side right bridge arm is formed by connecting in series; primary side first resonance inductance Lr1Primary side first resonance capacitor Cr1And an excitation inductor LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2Together form a resonant cavity, and a primary side first resonant inductor Lr1Is equal to the secondary side second resonant inductor Lr2Inductance value, primary side first resonant capacitor Cr1Second resonance capacitor C with capacitance equal to secondary sider2A capacitance value; a. b is the middle point of the left and right bridge arms of the primary side, c and d are the middle points of the left and right bridge arms of the secondary side, wherein the first resonant inductor L of the primary sider1Is connected with point a, and a primary side first resonant capacitor Cr1Is connected with point b, and a primary side first resonant inductor Lr1Another end of (1), excitation inductance LmPrimary side first resonance capacitor Cr1Are sequentially connected in turn, and an excitation inductor LmAre connected in parallel at the primary side of the high-frequency transformer, and a secondary side is connected with a second resonance inductor Lr2Is connected with point c, and a secondary side second resonant inductor Lr2Is connected with one end of the secondary side of the high-frequency transformer, and the secondary side is provided with a second resonance capacitor Cr2Is connected with point d, and a secondary side second resonant capacitor Cr2The other end of the secondary side of the high-frequency transformer is connected with the other end of the secondary side of the high-frequency transformer; i.e. ir1Is primary side resonant current ir2Is a secondary side resonant current imIs an exciting current; the resonant frequency of the resonant cavity is defined by a primary side first resonant inductor Lr1Primary side first resonance capacitor Cr1Determining the resonant frequency
Figure GDA0003243411530000031
The operating modes of the topology are divided into a boost mode and a buck mode, wherein,
the control method in the boosting mode comprises the following steps: fifth switching tube S for adjusting secondary side5Sixth switch of secondary sidePipe S6And a seventh secondary switch tube S7And the eighth secondary switch tube S8The duty ratio of the secondary side switching tube enables the conduction time of the secondary side switching tube to be one half of the resonance period all the time, the control signal of the primary side left bridge arm switching tube is subjected to phase shifting, and the primary side first switching tube S is enabled to be1And a secondary side fifth switch tube S5And the eighth secondary switch tube S8Turn off the second switch tube S on the primary side at the same time2And a sixth secondary switch tube S6And a seventh secondary switch tube S7Simultaneously turned off and phase-shifted by an angle of
Figure GDA0003243411530000032
fsTo the switching frequency, frFor resonant frequency, the voltage is adjusted by means of the switching frequency fsIs completed;
the control method in the pressure reduction mode comprises the following steps: regulating a primary side first switching tube S1Primary side second switch tube S2Third switch tube S on primary side3Primary side fourth switch tube S4The on-state time of the primary side switching tube is always one half of the resonance period, and the phase of the on-state signal of the secondary side left bridge arm switching tube is shifted to enable the secondary side fifth switching tube S5First switch tube S connected with primary side1Primary side fourth switch tube S4And the sixth secondary switch tube S is turned off simultaneously6And the primary side second switch tube S2Primary side third switch tube S3Simultaneously turned off and phase-shifted by an angle of
Figure GDA0003243411530000033
fsTo the switching frequency, frFor resonant frequency, the voltage is adjusted by means of the switching frequency fsIs performed.
Furthermore, each forward and reverse waveform is symmetrical in the same mode, the forward operation characteristic of the boosting mode is consistent with the reverse operation characteristic of the voltage reduction mode, and the reverse operation characteristic of the boosting mode is consistent with the forward operation characteristic of the voltage reduction mode, so that the voltage boosting circuit has good symmetry.
Furthermore, the working frequency of the resonant cavity is always below the resonant frequency, the voltage gain changes monotonically with the reduction of the frequency in a normal working mode, and zero voltage conduction of the switch tube on one side of the transformer and zero current turn-off of the switch tube on the other side can be realized through reasonable design parameters.
Further, the direction of power flow can be switched naturally and smoothly without shutdown commutation, whether the cavity is in boost or buck mode.
Further, in a certain frequency range, the adjustment range of the voltage gain is mainly influenced by the excitation inductance LmFirst resonance inductance L with primary sider1The smaller the ratio, the wider the adjustment range.
Further, for converters designed with different parameters, the frequency change range and the upper limit of the output power are limited differently, and if the frequency is modulated excessively or the output power is too large, the waveforms of the resonator may be distorted, and thus part of the advantages of the control method is lost.
Compared with the prior art, the invention has the following advantages and effects:
compared with the traditional frequency modulation control method, the control method provided by the invention can realize smooth switching of power, namely, no matter in a boosting mode or a voltage reduction mode, when the voltage on the load side is higher than the output voltage of the converter, the power can be naturally commutated without stopping switching.
Meanwhile, in the control method, no matter in a boosting mode or a reducing mode, zero-voltage conduction of the switching tube on one side of the transformer and zero-current turn-off of the switching tube on the other side can be realized, and the switching loss is smaller.
Compared with frequency modulation control, the voltage regulation range of the control method in the voltage reduction mode is wider, wide-range voltage regulation is facilitated, the working frequency range of the converter does not exceed the resonant frequency all the time, and adverse effects such as loss increase caused by overhigh switching frequency in voltage regulation are avoided.
Drawings
FIG. 1 is a topological structure diagram of a bidirectional CLLLC resonant DC-DC converter in the invention;
FIG. 2 is a diagram of the waveforms of the driving signals and the key waveforms of the circuit for forward operation in the boost mode of the present invention;
FIG. 3 is a diagram of the waveform of the driving signal for reverse operation and the key waveform of the circuit in the boost mode of the present invention;
FIG. 4 is a diagram of the waveforms of the driving signals and the key waveforms of the circuit for forward operation in the buck mode of the present invention;
FIG. 5 is a diagram of the waveforms of the driving signals for reverse operation and the key waveforms of the circuit in the buck mode of the present invention;
FIG. 6 is a schematic diagram of the gain curves of the buck-boost mode and the boost mode obtained by simulation and time domain analysis according to the present invention;
FIG. 7 is a schematic diagram of a key waveform of the boost forward operation obtained by simulation in the present invention;
FIG. 8 is a schematic diagram of a key waveform of boost reverse operation obtained by simulation in the present invention;
FIG. 9 is a schematic diagram of key waveforms of forward operation of voltage reduction obtained by simulation in the present invention;
fig. 10 is a schematic diagram of key waveforms of the buck reverse operation obtained by simulation in the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Examples
To better illustrate the present invention, the present embodiment applies the control method to a simulation example of a bidirectional CLLLC resonant DC-DC converter, and the applied topology is shown in fig. 1.
The topology comprises a primary side first switch tube S1Primary side second switch tube S2Third switch tube S on primary side3Primary side fourth switch tube S4And a fifth secondary switch tube S5And the sixth secondary switch tubeS6And a seventh secondary switch tube S7And the eighth secondary switch tube S8Primary side first resonant inductor Lr1Primary side first resonance capacitor Cr1And an excitation inductor LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2And a high-frequency transformer connected with the primary side and the secondary side, wherein the primary side is provided with a first switch tube S1Primary side second switch tube S2Form a primary side left bridge arm and a primary side third switch tube S3Primary side fourth switch tube S4Forming a primary side right bridge arm; secondary side fifth switch tube S5And a sixth secondary switch tube S6Form a secondary left bridge arm and a secondary seventh switch tube S7And the eighth secondary switch tube S8Forming a secondary side right bridge arm; primary side first resonance inductance Lr1Primary side first resonance capacitor Cr1And an excitation inductor LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2Together form a resonant cavity, and a primary side first resonant inductor Lr1Is equal to the secondary side second resonant inductor Lr2Inductance value, primary side first resonant capacitor Cr1Second resonance capacitor C with capacitance equal to secondary sider2A capacitance value; a. b is the middle point of the left and right bridge arms of the primary side, c and d are the middle points of the left and right bridge arms of the secondary side, ir1Is primary side resonant current ir2Is a secondary side resonant current imIs an exciting current; the resonant frequency of the resonant cavity is defined by a primary side first resonant inductor Lr1Primary side first resonance capacitor Cr1Determining the resonant frequency
Figure GDA0003243411530000061
The specific parameter design is shown in table 1:
TABLE 1 simulation Circuit parameters
Parameter(s) Value taking
Input voltage 600V
Output voltage 300-500V
Transformation ratio of transformer 1.5
Maximum output power 3.3kW
Primary side first resonance inductance Lr1 21.52μH
Secondary side second resonant inductor Lr2 10.01μH
Primary side first resonant capacitor Cr1 71.99nF
Secondary side second resonance capacitor Cr2 161.99nF
Excitation inductance 135.1μH
Resonant frequency 100kHz
The control method is applied to a symmetrical CLLLC resonant DC-DC converter, the forward operation characteristics of the boost mode and the reverse operation characteristics of the buck mode are consistent, and the forward operation characteristics of the boost mode and the reverse operation characteristics of the buck mode are consistent, so that the control method has good symmetry. In the boost mode, when the circuit operates in the forward direction, the circuit has a total of four operation modes within a half switching period, and the key waveforms are as shown in fig. 2:
1) mode 1[ t ]0-t1]
At t0Before the moment, the current of the primary side of the transformer is a negative value, and the current is supplied to a fourth switching tube S of the primary side in dead time4Is discharged through the capacitor of S4Is zero voltage conduction (ZVS), S4After conduction, exciting current imApproximately linearly rising, primary side resonant current ir1And secondary side resonance current ir2Approximately in the form of a sinusoid. The duration of mode 1 is half the resonance period.
2) Mode 2[ t ]1-t2]
Mode 2 is dead time, t1Moment turn-off primary side first switch tube S1And a secondary side fifth switch tube S5The eighth switching tube S8According to the nature of LLC resonance, the secondary side resonance current ir2The secondary side switching tube is turned off at Zero Current (ZCS) after the voltage is approximately reduced to zero, and the primary side resonant current i is at the momentr1Is equal to the excitation current imDue to the excitation current imIs positive and thus gives the primary side a second switching tube S2Is discharged and then passes through S2The anti-parallel diode freewheels when the voltage input to the resonant cavity is zero.
3) Mode 3[ t ]2-t3]
t2At the moment, the second switch tube S on the primary side is enabled2Is turned on when S2Is conducted at Zero Voltage (ZVS), and the current passes through the switch tube S2And S4Follow current, the resonant cavity input voltage is zero, and energy is not transferred in the mode.
4) Mode 4[ t ]3-t4]
Mode 4 is dead time due to primary side resonant current ir1Is positive and gives the third switch tube S on the primary side in the dead time3Is discharged from the capacitor ofThen follow current through its body diode, S3And zero voltage turn-on when turning on again.
The waveform in the second half period is completely symmetrical with the first half period.
In the buck mode, when the circuit is operating in the forward direction, there are a total of four operating modes within a half switching period, and the key waveforms are as shown in fig. 4.
1) Mode 1[ t ]0-t1]
At t0In the dead time before arrival, the secondary side current is positive, so the eighth switching tube S of the secondary side is supplied8Is discharged and then passes through S8The anti-parallel diode freewheels, hence S8Turn on is zero voltage turn on (ZVS). In mode 1, the excitation current imApproximately linearly rising, primary side resonant current ir1Starting from zero, secondary side resonant current ir2Approximately sinusoidal in form and advanced by zero crossing. The duration of mode 1 is half the resonance period.
2) Mode 2[ t ]1-t2]
Mode 2 is dead time, t1Moment turn-off primary side first switch tube S1Primary side fourth switch tube S4And a secondary side fifth switch tube S5At this time, S is reduced to zero because the primary current has already dropped1、S4Zero current off (ZCS). At this time, the secondary side resonant current ir2The zero crossing is advanced, the magnitude is equal to the exciting current, and the sixth switching tube S on the secondary side can be provided in dead time6Is discharged and then passes through S6Freewheeling of the anti-parallel diode.
3) Mode 3[ t ]2-t3]
t2At the moment, the secondary side sixth switching tube S is driven6Is turned on when S6Is conducted at Zero Voltage (ZVS), and the current passes through the switch tube S6And S8Freewheeling, which does not transfer energy in this mode.
4) Mode 4[ t ]3-t4]
Mode 4 is dead time due to secondary side resonant current ir2Negative values, given in the dead timeSecondary seventh switch tube S7Is charged and then freewheels through its body diode, S7And zero voltage turn-on when turning on again.
The waveform in the second half period is completely symmetrical with the first half period.
The invention discloses a phase-shift-unequal-width frequency modulation synchronous control method applied to the topology, which is specifically realized as follows:
a boosting mode: adjusting the duty ratio of the secondary switch tube to make the conduction time of the secondary switch tube always be one-half of the resonance period, and shifting the phase of the control signal of the primary left bridge arm switch tube to make the primary first switch tube S1And a secondary side fifth switch tube S5And the eighth secondary switch tube S8Turn off the second switch tube S on the primary side at the same time2And a sixth secondary switch tube S6And a seventh secondary switch tube S7Simultaneously turned off and phase-shifted by an angle of
Figure GDA0003243411530000081
fsTo the switching frequency, frFor resonant frequency, the voltage is adjusted by means of the switching frequency fsIs performed.
A pressure reduction mode: adjusting the duty ratio of the primary side switching tube to make the conduction time of the primary side switching tube always be one-half resonance period, and shifting the phase of the conduction signal of the secondary side left bridge arm switching tube to make the secondary side fifth switching tube S5First switch tube S connected with primary side1Primary side fourth switch tube S4And the sixth secondary switch tube S is turned off simultaneously6And the primary side second switch tube S2Primary side third switch tube S3Simultaneously turned off and phase-shifted by an angle of
Figure GDA0003243411530000091
fsTo the switching frequency, frIs the resonant frequency. The voltage being regulated by the switching frequency fsIs performed.
The control method is applied to a symmetrical CLLLC resonant DC-DC converter, the forward operation characteristics of the boost mode and the reverse operation characteristics of the buck mode are consistent, and the forward operation characteristics of the boost mode and the reverse operation characteristics of the buck mode are consistent, so that the control method has good symmetry.
By simulation, the gain curves of the buck-boost mode and the boost mode shown in fig. 6 are obtained, respectively. The actual simulation result accords with the result of time domain analysis, and it can be seen that no matter in the boost mode or the buck mode, a wide voltage adjustment range can be obtained in a small frequency range, and the converter always works below the resonant frequency.
The key waveform diagram for the boosting forward operation shown in fig. 7, the key waveform diagram for the boosting reverse operation shown in fig. 8, the key waveform diagram for the step-down forward operation shown in fig. 9, and the key waveform diagram for the step-down reverse operation shown in fig. 10 all show that simulation results are in line with expectations, and it is confirmed that no matter which mode the converter operates in, zero-voltage conduction of the switching tube on one side of the transformer and zero-current turn-off of the switching tube on the other side can be realized, so that the control method has smaller switching loss. In the boost mode and the buck mode, the reverse waveforms are obtained by increasing the power supply voltage at the load side on the basis of not changing the control signal of the switching tube, and the control method is proved to be capable of realizing free bidirectional power switching.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (3)

1. A control method of a bidirectional CLLLC type converter with automatically switchable power direction is applied to a bidirectional CLLLC resonant DC-DC converter topology, and the topology comprises a primary side first switch tube S1Primary side second switch tube S2Third switch tube S on primary side3Primary side fourth switch tube S4And a fifth secondary switch tube S5And a sixth secondary switch tube S6And a seventh secondary switch tube S7And the eighth secondary switch tube S8Primary side first resonant inductor Lr1Primary side first resonance capacitor Cr1And an exciting currentFeeling LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2And a high-frequency transformer connected with the primary side and the secondary side, wherein the primary side is provided with a first switch tube S1Primary side second switch tube S2A primary side left bridge arm and a primary side third switch tube S are formed by connecting in series3Primary side fourth switch tube S4The primary side right bridge arm is formed by connecting in series; secondary side fifth switch tube S5And a sixth secondary switch tube S6A secondary-side left bridge arm and a secondary-side seventh switching tube S are formed by connecting in series7And the eighth secondary switch tube S8A secondary side right bridge arm is formed by connecting in series; primary side first resonance inductance Lr1Primary side first resonance capacitor Cr1And an excitation inductor LmSecondary side second resonance inductor Lr2And a secondary side second resonant capacitor Cr2A and b are respectively the middle points of the left and right bridge arms of the primary side, c and d are respectively the middle points of the left and right bridge arms of the secondary side, wherein, a first resonant inductor L of the primary sider1Is connected with point a, and a primary side first resonant capacitor Cr1Is connected with point b, and a primary side first resonant inductor Lr1Another end of (1), excitation inductance LmPrimary side first resonance capacitor Cr1Are sequentially connected in turn, and an excitation inductor LmAre connected in parallel at the primary side of the high-frequency transformer, and a secondary side is connected with a second resonance inductor Lr2Is connected with point c, and a secondary side second resonant inductor Lr2Is connected with one end of the secondary side of the high-frequency transformer, and the secondary side is provided with a second resonance capacitor Cr2Is connected with point d, and a secondary side second resonant capacitor Cr2The other end of the secondary side of the high-frequency transformer is connected with the other end of the secondary side of the high-frequency transformer; characterized in that the operating modes of the topology are divided into a boost mode and a buck mode, wherein,
the control method in the boosting mode comprises the following steps: fifth switching tube S for adjusting secondary side5And a sixth secondary switch tube S6And a seventh secondary switch tube S7And the eighth secondary switch tube S8The on-state time of the secondary side switching tube is always one half of the resonance period, the upper and lower tubes of the same bridge arm of the primary side switching tube are complementarily conducted according to the 50 percent duty ratio and added with a dead zone for a certain time, and the left bridge arm of the primary side is openedThe control signal of the switch-off tube is shifted in phase to enable the first switch tube S on the primary side1And a secondary side fifth switch tube S5And the eighth secondary switch tube S8Turn off the second switch tube S on the primary side at the same time2And a sixth secondary switch tube S6And a seventh secondary switch tube S7Simultaneously turn off, primary side third switch tube S3And a sixth secondary switch tube S6And a seventh secondary switch tube S7Simultaneously conducted, the fourth switch tube S on the primary side4And a secondary side fifth switch tube S5And the eighth secondary switch tube S8Are simultaneously conducted at a phase shift angle of
Figure FDA0003289370480000021
fsTo the switching frequency, frFor resonant frequency, the voltage is adjusted by means of the switching frequency fsIs completed;
the control method in the pressure reduction mode comprises the following steps: regulating a primary side first switching tube S1Primary side second switch tube S2Third switch tube S on primary side3Primary side fourth switch tube S4The on-state time of the primary side switching tube is always one half of the resonance period, the upper and lower tubes of the same bridge arm of the secondary side switching tube are complementarily conducted according to the 50 percent duty ratio and added with a dead zone for a certain time, the phase of a conducting signal of the switching tube of the left bridge arm of the secondary side is shifted, and the fifth switching tube S of the secondary side is enabled to be5First switch tube S connected with primary side1Primary side fourth switch tube S4And the sixth secondary switch tube S is turned off simultaneously6And the primary side second switch tube S2Third switch tube S on primary side3Seventh switching tube S with auxiliary side turned off simultaneously7And the primary side second switch tube S2Third switch tube S on primary side3And the eighth switch tube S on the secondary side8First switch tube S connected with primary side1Primary side fourth switch tube S4Are simultaneously conducted at a phase shift angle of
Figure FDA0003289370480000022
fsTo the switching frequency, frFor resonant frequency, the voltage is adjusted by means of the switching frequency fsIs completed;
wherein the primary side first resonant inductor Lr1Is equal to the secondary side second resonant inductor Lr2Inductance value, the primary first resonant capacitor Cr1Second resonance capacitor C with capacitance equal to secondary sider2A capacitance value.
2. The method as claimed in claim 1, wherein the resonant frequency of the resonant cavity is determined by a primary first resonant inductor Lr1Primary side first resonance capacitor Cr1Determining the resonant frequency
Figure FDA0003289370480000031
3. The method according to claim 1, wherein the waveforms in forward and reverse directions are symmetrical in the same mode, the forward operation characteristic of the boost mode is consistent with the reverse operation characteristic of the buck mode, and the forward operation characteristic of the boost mode is consistent with the forward operation characteristic of the buck mode, so that the power direction of the bidirectional CLLLC converter is automatically switched.
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