CN114157150A - High-gain bidirectional Y source-LLC isolation direct current-direct current converter - Google Patents

High-gain bidirectional Y source-LLC isolation direct current-direct current converter Download PDF

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CN114157150A
CN114157150A CN202111257269.4A CN202111257269A CN114157150A CN 114157150 A CN114157150 A CN 114157150A CN 202111257269 A CN202111257269 A CN 202111257269A CN 114157150 A CN114157150 A CN 114157150A
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llc
switching tube
voltage
source
direct current
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CN114157150B (en
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袁也
关远鹏
谢运祥
王宗友
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Shenzhen Sosen Electronics Co Ltd
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Shenzhen Sosen Electronics 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
    • 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
    • H02M3/33592—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 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • 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 high-gain bidirectional Y source-LLC isolation direct current-direct current converter. The bidirectional Y source-LLC isolation direct current-direct current converter comprises a Y source impedance network, an LLC resonance network and a high-voltage side full bridge which are sequentially cascaded; the Y-source impedance network provides high gain through the Y-type coupling inductor, and reduces the parasitic effect of the transformer; the LLC resonant network provides pulse frequency modulation capability through a resonant cavity and a transformer, and realizes adjustment of voltages on two sides and port isolation; the high-voltage side full bridge provides synchronous rectification and inversion functions, so that bidirectional flow of energy is realized, and the efficiency of the converter is improved. The invention greatly reduces the difference of the primary and secondary turns of the transformer in the LLC resonant network and effectively reduces the high-frequency parasitic capacitance in the transformer. The input loop and the output loop of the invention have electrical isolation, thereby optimizing the operating environment of the Y source impedance network and reducing the number and cost of the switch tubes.

Description

High-gain bidirectional Y source-LLC isolation direct current-direct current converter
Technical Field
The invention relates to the technical field of LLC resonant DC-DC converters and impedance source network DC-DC converters, in particular to a bidirectional Y source-LLC isolation DC-DC converter with high gain.
Background
With the rapid development and the technological progress of the society, the dc-dc converter is used as an important component for dc power conversion, and the high-gain topology becomes the current research focus. The full-bridge LLC resonant converter is one of the isolated DC-DC converters widely applied at present, has a wider input and output voltage regulation range and higher conversion efficiency, and can realize the soft switching characteristic and the electrical isolation of an input side and an output side in a wider range. However, the gain of the full-bridge LLC resonant converter is mainly provided by the transformer, and the number of primary and secondary turns of the transformer is greatly different under the condition of higher gain, and the parasitic effect caused by the difference is not negligible. In particular, when the switching frequency is high, the LLC converter has large EMI, even resulting in the circuit not working properly. Moreover, the bidirectional full-bridge LLC resonant converter needs 8 switching tubes, and due to parasitic effect, there is a complex potential working mode, which is not favorable for the converter to work safely and stably.
To further increase the gain of the system, Y-source converters have been proposed in recent years. The Y-source converter is a high-gain DC-DC converter and has the characteristics of small number of used switching tubes, low control difficulty, simple circuit structure and the like. However, as the impedance source converter, the input side and the output side of the impedance source converter are grounded, an additional isolation circuit is usually required to be arranged, a large number of switching tubes are added, and difficulties are brought to circuit design and application popularization. Documents "h.sugali and s.sathyan," Design and Analysis of Zero Current switching Y-Source DC/DC Converter for Renewable Energy Applications, "2021IEEE Kansas Power and Energy references (KPEC),2021, pp.1-5" propose a Y-Source boost type DC-DC Converter, which adopts a structure in which a Y-Source impedance network, a middle full bridge, a parallel resonant cavity, and a high-voltage full bridge are sequentially cascaded. The Y-source Boost type direct current-direct current converter reduces the transformation ratio of a transformer by utilizing the high gain of a Y-source impedance network, realizes pulse frequency modulation on output voltage by utilizing a parallel resonant cavity, realizes pulse width modulation on the output voltage by utilizing an intermediate full bridge, and isolates an input loop from an output loop by utilizing the transformer; however, in order to realize these functions, the Y-source Boost type dc-dc converter uses 4 switching tubes and 5 diodes, the power of the converter can only flow from the low-voltage side to the high-voltage side, and in addition, the resonant cavity element of the converter is composed of the parasitic capacitance and the leakage inductance of the transformer, the resonant frequency is very high, the converter can only work in an under-resonance region, so that the switching tubes and the diodes can only realize zero current turn-off but not zero voltage turn-on, the efficiency of the system is reduced, and meanwhile, the uncertainty of the parasitic parameters also brings difficulty to the parameter design.
Disclosure of Invention
The invention provides a novel high-gain bidirectional Y source-LLC isolation direct current-direct current converter aiming at the contradiction of potential abnormal operation modes caused by high gain and parasitic effect existing in the traditional direct current-direct current converter, and the Y source impedance network and the LLC resonance network flexibly provide high gain together, so that the turns difference and the parasitic effect of a transformer coil in the LLC resonance network are reduced, and support is provided for safe and stable operation of the LLC bidirectional converter; a transformer in the LLC resonant network provides electrical isolation for the input loop and the output loop; only 6 switching tubes are needed to realize bidirectional flow of energy, and cost of a switching device is effectively reduced.
The purpose of the invention is realized by at least one of the following technical solutions.
A high-gain bidirectional Y source-LLC isolation direct current-direct current converter comprises a Y source impedance network, an LLC resonance network and a high-voltage side full bridge which are sequentially cascaded;
because the power in the bidirectional Y source-LLC isolation direct current-direct current converter can flow bidirectionally, the condition that the power flows from the low-voltage side to the high-voltage side in a forward direction and the power flows from the high-voltage side to the low-voltage side in a reverse direction is defined;
when power flows in the forward direction, the Y-source impedance network realizes high gain through the Y-type coupling inductor, boosts the voltage at the low-voltage side of the bidirectional Y-source-LLC isolation direct current-direct current converter, converts the voltage into unipolar square wave voltage and outputs the unipolar square wave voltage to the LLC resonant network;
the LLC resonant network filters out a direct-current component through the resonant cavity, converts the unipolar square wave voltage from the Y-source impedance network into bipolar square wave voltage, boosts the voltage again through the transformer and outputs the voltage to the high-voltage side full bridge;
the high-voltage side full bridge realizes alternating-direct current conversion through four switching tubes, converts bipolar square wave voltage from the LLC resonant network into direct current voltage, and finally outputs the direct current voltage to the high-voltage side of the bidirectional Y source-LLC isolation direct current-direct current converter;
when power flows reversely, the high-voltage side full bridge realizes direct-alternating current conversion through four switching tubes, converts the high-voltage side voltage of the bidirectional Y source-LLC isolation direct current-direct current converter into bipolar square wave voltage and outputs the bipolar square wave voltage to the LLC resonant network;
after the voltage of the LLC resonant network is reduced by a transformer, the LLC resonant network provides direct current bias by a resonant cavity, converts the bipolar square wave voltage from the high-voltage side full bridge into unipolar square wave voltage and outputs the unipolar square wave voltage to the Y-source impedance network;
the Y-source impedance network realizes high gain through the Y-type coupling inductor, and the unipolar square wave voltage from the LLC resonant network is reduced again, filtered by the low-voltage side filter capacitor and then output to the low-voltage side of the bidirectional Y-source-LLC isolation direct current-direct current converter.
Furthermore, the Y-source impedance network comprises a low-voltage side filter capacitor, a first switch tube, a Y-type coupling inductor, a first capacitor and a second switch tube; the Y-type coupling inductor comprises a first winding, a second winding and a third winding; the LLC resonant network comprises a resonant capacitor, a resonant inductor and a transformer; the transformer comprises a fourth winding and a fifth winding; the high-voltage side full bridge comprises a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube and a high-voltage side filter capacitor;
the positive electrode of the low-voltage side filter capacitor is connected with the emitter of the first switching tube and the positive electrode of the direct-current voltage source or the equivalent load, and the negative electrode of the low-voltage side filter capacitor is connected with the negative electrode of the direct-current voltage source or the equivalent load;
the collector of the first switching tube is connected with the homonymous end of the first winding;
the different-name end of the first winding is connected with the same-name ends of the second winding and the third winding;
the synonym end of the third winding is connected with the anode of the first capacitor, and the cathode of the first capacitor is connected with the cathode of the low-voltage side filter capacitor;
the synonym end of the second winding is connected with the collector of the second switching tube and one end of the resonant capacitor;
an emitter of the second switching tube is connected with the negative electrode of the low-voltage side filter capacitor;
the other end of the resonant capacitor is connected with one end of the resonant inductor, and the other end of the resonant inductor is connected with the same-name end of the fourth winding;
the synonym end of the fourth winding is connected with the negative electrode of the low-voltage side filter capacitor;
the dotted end of the fifth winding is connected with the emitter of the third switching tube and the collector of the fourth switching tube; the synonymy end of the fifth winding is connected with the emitter of the fifth switching tube and the collector of the sixth switching tube;
the collector of the third switching tube is connected with the collector of the fifth switching tube, the positive electrode of the high-voltage side filter capacitor and the positive electrode of the direct-current voltage source or the equivalent load;
an emitter of the fourth switching tube is connected with an emitter of the sixth switching tube, a cathode of the high-voltage side filter capacitor and a cathode of the direct-current voltage source or the equivalent load;
when the low-voltage side filter capacitor and the first switch tube are connected with a direct-current voltage source, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube and the high-voltage side filter capacitor are connected with an equivalent load;
when the low-voltage side filter capacitor and the first switch tube are connected with the equivalent load, the third switch tube, the fourth switch tube, the fifth switch tube, the sixth switch tube and the high-voltage side filter capacitor are connected with a direct-current voltage source.
Further, a first port is formed by taking the anode of the low-voltage side filter capacitor and the emitter of the first switching tube as one end and the cathode of the low-voltage side filter capacitor as the other end, and the voltage of the first port is defined as the low-voltage side voltage of the bidirectional Y source-LLC isolation direct current-direct current converter;
a second port is formed by taking the synonym end of a second winding of the Y-shaped coupling inductor and a collector of a second switching tube as one end and taking the negative electrode of the low-voltage side filter capacitor as the other end, and the voltage of the second port is defined as the high-voltage side voltage of the Y-source impedance network;
one side of the resonant capacitor, which is not connected with the resonant inductor, is taken as one end, the synonym end of the fourth winding is taken as the other end, a third port is formed, the voltage of the third port is defined as the low-voltage side voltage of the LLC resonant network, and the third port is cascaded with the second port;
a homonymous end of the fifth winding is taken as one end, a synonym end of the fifth winding is taken as the other end to form a fourth port, and the voltage of the fourth port is defined as the high-voltage side voltage of the LLC resonant network;
an emitter of the third switching tube and a collector of the fourth switching tube are used as one end, an emitter of the fifth switching tube and a collector of the sixth switching tube are used as the other end to form a fifth port, and the fifth port and the fourth port are in cascade connection; a sixth port is formed by taking a collector of the third switching tube, a collector of the fifth switching tube and a positive electrode of the high-voltage side filter capacitor as one end, an emitter of the fourth switching tube, an emitter of the sixth switching tube and a negative electrode of the high-voltage side filter capacitor as the other end, and voltage of the sixth port is defined as voltage of the high-voltage side of the bidirectional Y source-LLC isolation direct current-direct current converter;
a transformer T in the LLC resonant network isolates a low-voltage side loop and a high-voltage side loop of the bidirectional Y source-LLC isolation direct current-direct current converter from each other.
Further, when power in the bidirectional Y source-LLC isolated DC-DC converter flows in the forward direction, the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in a synchronous rectification mode or an uncontrolled rectification mode;
when power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction and the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in a synchronous rectification mode, if the collecting and transmitting voltage of the third switching tube, the fourth switching tube, the fifth switching tube or the sixth switching tube is reduced to a certain value, namely when a body diode of the switching tube is switched on, a corresponding switching tube is applied with a conducting signal; if the direction of the collecting and emitting voltage of the third switching tube, the fourth switching tube, the fifth switching tube or the sixth switching tube is changed from negative to positive, the corresponding switching tube is applied with a turn-off signal;
when power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction and the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in an uncontrolled rectification mode, driving signals of the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube are locked, and rectification is completed through diodes in the corresponding switching tubes;
when power in the bidirectional Y source-LLC isolation direct current-direct current converter reversely flows, the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube work in an inversion mode, and driving signals with dead zones are applied to the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube; in the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube, the driving signals of the switching tubes of different bridge arms are synchronous, namely the third switching tube and the fifth switching tube are simultaneously turned on and simultaneously turned off, the fourth switching tube and the sixth switching tube are simultaneously turned on and simultaneously turned off, the switching tubes of the same bridge arm have a phase difference of half period and dead time, namely the driving signals of the third switching tube and the fourth switching tube have a phase difference of half period and dead time, and the driving signals of the fifth switching tube and the sixth switching tube have a phase difference of half period and dead time.
Further, when the power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction or the reverse direction, the working modes of the bidirectional Y source-LLC isolation direct current-direct current converter comprise a direct-connection mode and a non-direct-connection mode;
the direct mode refers to that the port voltages of the second port and the third port are zero, namely the second port and the third port are short-circuited; the non-through mode means that the port voltages of the second port and the third port are not zero, that is, the second port and the third port are not short-circuited;
when the bidirectional Y source-LLC isolation direct current-direct current converter works in a direct-through mode, the first switch tube is switched off, and the second switch tube is switched on;
when the bidirectional Y source-LLC isolation direct current-direct current converter works in a non-direct-through mode, the first switch tube is conducted, and the second switch tube is turned off.
Further, when power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction, a driving signal of the first switching tube is locked;
when the power in the bidirectional Y source-LLC isolation direct current-direct current converter reversely flows, the driving signal of the second switch tube is locked.
Further, when power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction, the duty ratio of a driving signal applied to the second switching tube is 50%;
when the power in the bidirectional Y source-LLC isolation direct current-direct current converter reversely flows, the duty ratio of the driving signal applied to the first switch tube is 50%.
Further, when the bidirectional Y source-LLC isolation DC-DC converter flows in the forward direction of power, the voltage gain is KY-LLC-FAnd n is the transformation ratio of the transformer T, namely:
Figure BDA0003324268530000061
wherein N ist1、Nt2The number of turns of the coil of the fourth winding and the number of turns of the coil of the fifth winding are respectively;
the ratio of the sum of the excitation inductance and the resonance inductance of the transformer to the inductance of the resonance inductance is recorded as a resonance inductance ratio m, and the expression is as follows:
Figure BDA0003324268530000062
then K isY-LLC-FThe expression of (a) is:
Figure BDA0003324268530000063
wherein KYThe gain of the Y source impedance network is expressed as:
Figure BDA0003324268530000064
wherein k is the winding factor of the Y-type coupling inductor, and the expression is as follows:
Figure BDA0003324268530000065
wherein N is1、N2And N3The number of coil turns of the first winding, the second winding and the third winding are respectively;
KLLC-Fthe forward gain coefficient of a resonant cavity in the LLC resonant network is expressed as follows:
Figure BDA0003324268530000071
wherein FxThe expression is the standard switch operation frequency:
Figure BDA0003324268530000072
wherein f issTo the switching frequency, f1The frequency of the series resonance of the resonance inductor and the resonance capacitor is expressed as follows:
Figure BDA0003324268530000073
Qfis a forward quality factor, and the expression is:
Figure BDA0003324268530000074
wherein R isac-fThe expression is a forward alternating current equivalent resistance:
Figure BDA0003324268530000075
wherein R is0Is the resistance of the equivalent load.
Furthermore, when the power of the bidirectional Y source-LLC isolation direct current-direct current converter flows reversely, the voltage gain of the bidirectional Y source-LLC isolation direct current-direct current converter is KY-LLC-R，KY-LLC-RThe expression of (a) is:
Figure BDA0003324268530000076
KLLC-Rthe expression of the reverse gain coefficient of the resonant cavity in the LLC resonant network is as follows:
Figure BDA0003324268530000077
wherein QrThe expression for the inverse quality factor is:
Figure BDA0003324268530000078
wherein R isac-rThe expression is the reverse alternating current equivalent resistance:
Figure BDA0003324268530000079
eliminating reverse gain coefficient K of resonant cavityLLC-RReverse quality factor QrAnd a reverse AC equivalent resistance Rac-rThe expressions of the remaining symbols are the same as when power flows in the forward direction.
Further, when power in the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction, the high-voltage side voltage is adjusted by adjusting the switching frequency of all the switching tubes simultaneously;
when power in the bidirectional Y source-LLC isolation direct current-direct current converter reversely flows, the low-voltage side voltage is adjusted by adjusting the switching frequency of all the switching tubes simultaneously.
Compared with the prior art, the invention has the advantages that:
the invention not only makes up the defect that the difference of turns of the transformer winding is very large when the difference of input and output voltages of the traditional LLC resonant converter is large by obtaining high gain through the Y source impedance network, but also solves the problem that the input loop and the output loop of the traditional Y source converter are in common ground. In addition, the high-side full bridge adopts a switch tube, and can be used as synchronous rectification to reduce switching loss when power flows in the forward direction and used as an inversion full bridge when power flows in the reverse direction. The traditional bidirectional LLC resonant converter needs 8 switching tubes, while the direct cascade connection of the Y-source converter with the LLC resonant converter needs 10 switching tubes. Compared with direct cascade connection, the high-gain bidirectional Y source-LLC isolated direct current-direct current conversion reduces the number of the switching tubes to 6 while ensuring high gain and voltage regulation capability, is beneficial to reducing loss, improving efficiency and reducing control difficulty, and specifically comprises the following steps:
1. the high-gain bidirectional Y source-LLC isolation direct current-direct current converter greatly reduces the difference of the turns of the primary side and the secondary side of a transformer in an LLC resonant network, and effectively reduces high-frequency parasitic capacitance in the transformer.
2. The high-gain bidirectional Y source-LLC isolation direct current-direct current converter has electrical isolation between the input loop and the output loop, optimizes the running environment of a Y source impedance network, and reduces the number and cost of switching tubes.
3. The high-gain bidirectional Y source-LLC isolation direct current-direct current converter provided by the invention only uses 6 switch tubes while realizing bidirectional energy flow, and is reduced by 25% compared with the switch tubes of the traditional bidirectional LLC direct current-direct current converter.
4. The high-gain bidirectional Y source-LLC isolation direct current-direct current converter can realize synchronous rectification and zero current turn-off by the high-voltage side full bridge switching tube when power flows in the forward direction; when power flows reversely, the high-voltage side full-bridge switch tube can realize zero-voltage switching-on, and the efficiency of the converter and the operating environment of the switch tube are effectively improved.
Drawings
FIG. 1 is a schematic diagram of a high-gain bidirectional Y-source-LLC isolated DC-DC converter circuit structure according to the invention;
FIG. 2 is a schematic diagram of a typical application circuit structure of a high-gain bidirectional Y-source-LLC isolated DC-DC converter according to the invention;
FIG. 3 shows an excitation inductor (L) added with a Y-type coupling inductor when the power of a high-gain bidirectional Y source-LLC isolated DC-DC converter of the present invention flows in the forward directionym) The later circuit structure schematic diagram;
fig. 4 is a schematic circuit diagram of the high-gain bidirectional Y source-LLC isolated dc-dc converter in phase 1 of the forward non-shoot-through mode according to the present invention;
fig. 5 is a schematic circuit diagram of the high-gain bidirectional Y source-LLC isolated dc-dc converter in stage 2 of the forward non-shoot-through mode of the present invention;
fig. 6 is a schematic circuit diagram of the circuit structure in the 3 rd stage of the forward non-shoot-through mode of the high-gain bidirectional Y source-LLC isolated dc-dc converter according to the present invention;
FIG. 7 shows the second switch tube (S) of the high-gain bidirectional Y source-LLC isolation DC-DC converter of the present invention in forward operation2) Collecting and transmitting voltage US2Full bridge output current IobA second winding of the Y-type coupling inductor (N)2) Current IN2Resonant cavity current ILcAnd transformer exciting current ItmA schematic diagram of the waveform of (a);
FIG. 8 is a schematic diagram showing a simulated waveform of an output voltage of a high-gain bidirectional Y-source LLC isolated DC-DC converter according to the present invention in the forward direction;
FIG. 9 shows the fifth winding (N) of a high-gain bidirectional Y-source LLC isolated DC-DC converter according to the invention in forward operationt2) Voltage UNt2Full bridge output current IobResonant cavity current ILcAnd transformer exciting current ItmThe steady state enlargement of the simulated waveform;
fig. 10 is a schematic diagram of a circuit structure after an equivalent excitation inductor of a Y-type coupling inductor is added when power of a high-gain bidirectional Y source-LLC isolated dc-dc converter of the present invention flows in the reverse direction;
FIG. 11 is a schematic diagram of the circuit configuration of a high-gain bidirectional Y-source-LLC isolated DC-DC converter of the present invention in phase 1 of reverse non-shoot-through mode;
FIG. 12 is a schematic diagram of the circuit configuration of a high-gain bidirectional Y-source-LLC isolated DC-DC converter of the present invention in stage 2 of reverse non-shoot-through mode;
FIG. 13 is a schematic diagram of the circuit configuration of a high-gain bidirectional Y-source-LLC isolated DC-DC converter of the present invention in stage 3 of reverse non-shoot-through mode;
FIG. 14 shows the full-bridge driving signals and the fifth winding (N) of a high-gain bidirectional Y-source LLC isolated DC-DC converter according to the invention during reverse operationt2) Voltage UNt2Full bridge input current IibA second winding of the Y-type coupling inductor (N)2) Current IN2Resonant cavity current ILcAnd transformer exciting current ItmA schematic diagram of the waveform of (a);
FIG. 15 is a schematic diagram showing a simulated waveform of an output voltage of a high-gain bidirectional Y-source LLC isolated DC-DC converter according to the invention in reverse operation;
FIG. 16 shows the fifth winding (N) of a high-gain bidirectional Y-source LLC isolated DC-DC converter according to the invention in reverse operationt2) Voltage UNt2Full bridge input current IibResonant cavity current ILcAnd transformer exciting current ItmSteady state enlargement of the simulated waveform of (1).
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail below with reference to the drawings in the embodiments of the present invention, and it should be understood that the following detailed description is only illustrative of the present invention and is not intended to limit the scope of the present invention.
A high-gain bidirectional Y source-LLC isolation DC-DC converter is shown in figure 1 and comprises a Y source impedance network, an LLC resonant network and a high-voltage side full bridge which are sequentially cascaded;
the Y source impedance network comprises a low-voltage side filter capacitor C0A first switch tube S1Y-type coupling inductor and first capacitor C1And a second switching tube S2(ii) a The Y-type coupling inductor comprises a first winding N1A second winding N2And a third winding N3(ii) a The LLC resonant network comprises a resonant capacitor CrResonant inductor LrAnd a transformer T; the transformer T comprises a fourth winding Nt1And a fifth winding Nt2(ii) a The high-voltage side full bridge comprises a third switching tube S3And a fourth switching tube S4The fifth switch tube S5The sixth switching tube S6And a high-voltage side filter capacitor C2；
Wherein, the low-voltage side filter capacitor C0Is connected with a first switch tube S1Emitter of (2), positive pole of DC voltage source or equivalent load, low-voltage side filter capacitor C0Is connected with the negative pole of a direct current voltage source or an equivalent load,
first switch tube S1Collector electrode of the transformer is connected with the first winding N1The same name end of (1);
first winding N1The different name end of the first winding is connected with the second winding N2And a third winding N3The same name end of (1);
third winding N3The different name end of the first capacitor C is connected with the first capacitor C1The anode of (1), the first capacitor C1Negative pole of the capacitor is connected with a low-voltage side filter capacitor C0The negative electrode of (1);
second winding N2The different name end of the first switch tube is connected with a second switch tube S2The collector electrode and one end of a resonance capacitor Cr;
a second switch tube S2The emitter is connected with a low-voltage side filter capacitor C0The negative electrode of (1);
resonant capacitor CrThe other end is connected with a resonance inductor LrOne terminal of (1), resonant inductor LrIs connected with the fourth winding Nt1The same name end of (1);
fourth winding Nt1The different name end of the filter is connected with a low-voltage side filter capacitor C0The negative electrode of (1);
the fifth winding Nt2The same name end of the first switch tube is connected with a third switch tube S3Emitter and fourth switching tube S4A collector electrode of (a); the fifth winding Nt2The different name end of the switch is connected with a fifth switch tube S5OfEmitter and sixth switching tube S6A collector electrode of (a);
third switch tube S3Collector of the transformer is connected with a fifth switch tube S5Collector electrode, high-voltage side filter capacitor C2And a positive electrode of a direct current voltage source or an equivalent load;
fourth switch tube S4Is connected with a sixth switching tube S6Emitter and high-voltage side filter capacitor C2And a dc voltage source or a negative electrode of an equivalent load;
when the low-voltage side filter capacitor C0And a first switching tube S1When connected with a DC voltage source, the third switch tube S3And a fourth switching tube S4The fifth switch tube S5The sixth switching tube S6And a high-voltage side filter capacitor C2Connecting with an equivalent load;
when the low-voltage side filter capacitor C0And a first switching tube S1When connected with an equivalent load, the third switch tube S3And a fourth switching tube S4The fifth switch tube S5The sixth switching tube S6And a high-voltage side filter capacitor C2Is connected with a direct current voltage source.
A typical application circuit structure of a high-gain bidirectional Y source-LLC isolation DC-DC converter is shown in FIG. 2, and the high-voltage and low-voltage side voltage and current are sampled, are sent to a DSP after being subjected to A/D conversion, and are processed according to control requirements to generate corresponding switch tube driving signals to switch tubes located in a Y source impedance network and a high-voltage side full bridge.
Example 1:
when the second switch tube S is matched2Applying a driving signal to latch the first switch tube S1When the power of the bidirectional Y source-LLC isolating direct current-direct current converter is driven, the power of the bidirectional Y source-LLC isolating direct current-direct current converter flows in the forward direction from the low-voltage side to the high-voltage side, and the second switching tube S2The control signal of (2) is square wave, and the third switch tube S3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6Operating in synchronous rectification or in using a body diode D in a third switching tube3In the fourth switch tubeBody diode D4A body diode D in the fifth switch tube5And a body diode D in the sixth switching tube6Is not controlled to a rectified state. For the purpose of analysis, the first winding N of the Y-type coupled inductor1Upper equivalent parallel connection of an excitation inductor LymThe energy of the Y-type coupling inductor is concentrated and stored in the equivalent excitation inductor L of the Y-type coupling inductorymAs shown in fig. 3. Memory resonance inductance LrAnd a resonance capacitor CrFrequency f when series resonance occurs1Resonant inductance LrResonant capacitor CrAnd transformer excitation inductance LtmThe frequency of the three resonant frequencies is f0. The switching frequency in this embodiment is fsAnd f issSlightly less than f1And is greater than f0。
When the power of the bidirectional Y source-LLC isolation direct current-direct current converter flows in the forward direction, the bidirectional Y source-LLC isolation direct current-direct current converter has two working modes, namely a forward non-direct-connection mode and a forward direct-connection mode, and the two modes respectively have 3 stages.
Under the forward non-through mode, the first switch tube S1The internal body diode is conducted, the second switch tube S2Off, fig. 4 is an equivalent circuit diagram of the 1 st stage of the forward non-through mode, the dotted line representing the loop current flow direction, this stage corresponding to [ t ] of fig. 70,t1]The waveform of the interval. At this time, the voltage source VinLow voltage side filter capacitor C0The Y-type coupling inductor is a first capacitor C1Charging; transformer primary side fourth winding Nt1Receiving forward voltage, the secondary side third switch tube S3The sixth switching tube S6The internal body diode is conducted, and the excitation inductance L istmIs a first capacitor C1High-voltage side filter capacitor C2And an equivalent load R0Providing energy; excitation inductance LtmThe voltages on both sides are clamped by the high voltage side, so the excitation current varies linearly.
FIG. 5 is an equivalent circuit diagram of stage 2 of the forward non-shoot-through mode, where the dotted line represents the loop current flow direction, which corresponds to [ t ] of FIG. 71,t2]The waveform of the interval. At this time, the voltage source VinLow voltage side filter capacitor C0The Y-type coupling inductor is a first capacitor C1Charging energy, and simultaneously providing energy by a high-voltage side; transformer primary side fourth winding Nt1Receiving forward voltage, the secondary side third switch tube S3The sixth switching tube S6The inner body diode is conducted; excitation inductance LtmA high-voltage side filter capacitor C2And an equivalent load R0Providing energy, and using voltage source V to release energyinLow voltage side filter capacitor C0Is an excitation inductor L together with the Y-type coupling inductortmCharging; excitation inductance LtmThe voltages on both sides are clamped by the high-side voltage, so the excitation current varies linearly.
FIG. 6 is an equivalent circuit diagram of stage 3 of the forward non-shoot-through mode, where the dotted line represents the loop current flow direction, which corresponds to [ t ] of FIG. 72,t3]The waveform of the interval. At this time, the voltage source VinLow voltage side filter capacitor C0The Y-type coupling inductor is a first capacitor C1And (6) charging energy. However, at this time, the resonant current is not enough to maintain the exciting current and the energy is supplied to the high-voltage side, so the secondary side third switch tube S3The sixth switching tube S6The body diode in the transformer is turned off at zero current, and the resonance current is totally used as the excitation inductance LtmAnd (6) charging energy. At this time, the excitation inductance LtmThe voltages on both sides are no longer clamped by the voltage on the high side.
In the forward direction through mode, the first switch tube S1The internal body diode is turned off, the second switch tube S2Conduction, which also has 3 stages and whose course is completely symmetrical to the 3 stages of the forward non-through mode, the 4 th, 5 th and 6 th stages of the forward through mode are respectively the same as [ t ] of fig. 73,t4]、[t4,t5]And [ t5,t6]The waveforms of the intervals correspond, and the specific working principle is not repeated here.
Note that n is the transformation ratio of the transformer T, namely:
Figure BDA0003324268530000131
wherein N ist1、Nt2Are respectively a fourth winding Nt1A fifth winding Nt2The number of turns of the coil of (a);
recording transformer excitation inductance LtmAnd a resonant inductor LcSum and resonant inductance LcThe inductance ratio of (1) is a resonance inductance ratio m, and the expression is as follows:
Figure BDA0003324268530000132
gain K of Y source impedance networkYThe expression of (a) is:
Figure BDA0003324268530000133
wherein k is the winding factor of the Y-type coupling inductor, and the expression is as follows:
Figure BDA0003324268530000134
wherein N is1、N2And N3Are respectively a first winding N1A second winding N2And a third winding N3The number of turns of the coil of (a);
the forward gain coefficient of the resonant cavity is KLLC-FThe expression is as follows:
Figure BDA0003324268530000135
wherein FxThe expression is the standard switch operation frequency:
Figure BDA0003324268530000141
wherein f issTo the switching frequency, f1Is a resonant inductor LrAnd a resonance capacitor CrGeneration stringThe frequency of the coupled resonance is expressed as:
Figure BDA0003324268530000142
Qfis a forward quality factor, and the expression is:
Figure BDA0003324268530000143
wherein R isac-fThe expression is a forward alternating current equivalent resistance:
Figure BDA0003324268530000144
wherein R is0Is an equivalent load R0The resistance value of (1);
in summary, the converter of the present invention has a voltage gain of K when operating in the forward directionY-LLC-FThe expression is as follows:
Figure BDA0003324268530000145
in order to verify the correctness of the invention, a simulation model is built in simulation software according to the graph 3, a switching tube is set as an ideal device, the voltage of a low-voltage side direct-current voltage source is 15V, and the turn ratio N of a Y-shaped coupling inductor is1：N2：N3Inductance L of resonant inductor 20:70:20r79 muH, resonant capacitance CrTransformer turns ratio N of 200nFt1:Nt220: 80, equivalent load resistance R060 Ω, switching frequency fs39.9 kHz. Calculating the obtained series resonance frequency f1＝40kHz。
Can obtain a theoretical output voltage U0About 300V, it can be seen from FIG. 8 that the output voltage U obtained by simulation0About 296V. At this time, the boosting multiple reaches 20 times, but the turn ratio of the transformer is only 1: 4, achieveThe purpose of reducing the difference of the turns of the transformer coil on the premise of maintaining high gain is achieved; meanwhile, only 1 switching tube needs to be controlled in the Y source impedance network and the LLC resonant network, so that dead time does not need to be set. When synchronous rectification is adopted, only 5 switching tubes are required to be controlled, if body diode rectification is adopted, only 1 switching tube is required to be controlled by the whole converter, the driving signal is square wave, and the control difficulty is very low.
Fifth winding N shown in FIG. 9t2Voltage UNt2Full bridge output current IobResonant cavity current ILcAnd transformer exciting current ItmThe steady state enlarged view of the simulated waveform is consistent with the theoretical derivation result due to fsAnd f1Very close to each other, and fsSlightly less than f1The time of the 2 nd phase and the 4 th phase are each almost equal to the time of a half cycle, and the third switch tube S can be realized just in this case3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6Or body diode D in a third switch tube3Body diode D in fourth switch tube4A body diode D in the fifth switch tube5And a body diode D in the sixth switching tube6The zero current of (c) is turned off.
From the above expression, the bidirectional Y source-LLC isolated dc-dc converter still has the characteristics of an LLC resonant converter, i.e. can be obtained by adjusting the first switching tube S1A third switch tube S3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6The frequency of the control signal adjusts the resonant cavity gain to control the output voltage.
Example 2:
when the first switch tube S is matched1Applying a driving signal to latch the second switch tube S2When the driving signal is generated, the power flows in the reverse direction from the high-voltage side to the low-voltage side, and the first switch tube S1The control signal of (2) is square wave, and the third switch tube S3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6Working in an inversion state, the conducting signals of the upper and lower bridge arms need to be provided with dead zones,for the purpose of analysis, the first winding N of the Y-type coupled inductor1Upper equivalent parallel connection of an excitation inductor LymThe energy of the Y-type coupling inductor is concentrated and stored in the equivalent excitation inductor L of the Y-type coupling inductorymFig. 10 shows an equivalent circuit diagram at this time. Memory resonance inductance LrAnd a resonance capacitor CrFrequency f when series resonance occurs1Resonant inductance LrResonant capacitor CrAnd transformer excitation inductance LtmThe frequency of the three resonant frequencies is f0. In this embodiment, the switching frequency is fsAnd f issSlightly less than f1And is greater than f0The dead time is set in the first switch tube S1After the state changes.
When power flows reversely, the bidirectional Y source-LLC isolation direct current-direct current converter has two working modes, namely a reverse non-direct-connection mode and a reverse direct-connection mode, and the two modes respectively have 3 stages.
In reverse non-through mode, the first switch tube S1Conducting the second switch tube S2The internal body diode is turned off, fig. 11 is an equivalent circuit diagram of the 1 st stage of the reverse non-through mode, and the dotted line represents the loop current flow direction, which corresponds to [ t ] of fig. 140,t1]The waveform of the interval. In the phase, the inverter bridge signal is in dead time, and the third switch tube S3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6The control signals are turn-off signals, and the high-voltage side bridge arm is originally switched on by the fourth switching tube S4The fifth switch tube S5And (6) turning off. At the beginning of this phase, the second switch tube S2Internal body diode D2Turn off, first switch tube S1Is turned on and the resonant capacitor CrThe voltages on both sides cannot change suddenly, so the fourth winding N of the transformer Tt1Both sides are applied with forward voltage and are induced by resonant inductance LrAnd transformer excitation inductance LtmThe current on the third switch tube S can not suddenly change3Internal body diode D3The sixth switching tube S6Internal body diode D6On, high-voltage side bridge arm input current IibThe original size is kept to pass through a body diode D in a third switch tube3Body diode D in sixth switch tube6Free-wheeling, i.e. high-side bridge input current IibThe size is unchanged, but the direction changes. At this time, the first capacitor C1Providing energy to the Y-type coupling inductor, the low-voltage side and the high-voltage side; transformer excitation inductance LtmReleasing energy to the high-pressure side; transformer excitation inductance LtmClamped by input voltage, excitation current ItmLinearly changing.
FIG. 12 is an equivalent circuit diagram of stage 2 of the reverse non-through mode, with the dashed line representing the loop current flow direction, which corresponds to [ t ] of FIG. 141,t2]The waveform of the interval. At the beginning of this phase, the dead time ends and the third switching tube S3The sixth switching tube S6Is applied with a conducting signal, since in the last phase the third switch tube S3Internal body diode D3The sixth switching tube S6Internal body diode D6Has been conducted, so the third switch tube S3The sixth switching tube S6Are all zero voltage turn-on. At this time, the first capacitor C1Providing energy to the Y-type coupling inductor, the low-voltage side and the high-voltage side; transformer excitation inductance LtmReleasing energy to the high-pressure side; transformer excitation inductance LtmClamped by high side voltage, exciting current ItmLinearly changing.
FIG. 13 is an equivalent circuit diagram of stage 3 of the reverse non-through mode, with the dotted line representing the loop current flow direction, which corresponds to [ t ] of FIG. 142,t3]The waveform of the interval. At this time, the third switch tube S3The sixth switching tube S6And keeping on, and the zero crossing of the resonant current is changed to be positive at the stage, so that the high-voltage side full-bridge input current is changed to be positive at the subsequent zero crossing. At this time, the high voltage side and the first capacitor C1Providing energy to the Y-type coupling inductor and the low-voltage side; transformer excitation inductance LtmFirstly, releasing energy to a low-pressure side, and then charging energy to a high-pressure side; transformer excitation inductance LtmClamped by high side voltage, exciting current ItmLinearly changing.
In reverse-through mode, firstSwitch tube S1Off, the second switching tube S2Internal body diode D2Conduction, which also has 3 phases, and the process of 3 phases of the reverse non-through mode is completely symmetrical with 3 phases of the reverse non-through mode, these 3 phases corresponding to [ t ] of fig. 143,t4]、[t4,t5]And [ t5,t6]The waveforms of the intervals correspond, and the specific working principle is not repeated here.
Note that n is the transformation ratio of the transformer T, namely:
Figure BDA0003324268530000171
wherein N ist1、Nt2Are respectively a fourth winding Nt1A fifth winding Nt2The number of turns of the coil of (a);
recording transformer excitation inductance LtmAnd a resonant inductor LcSum and resonant inductance LcThe inductance ratio of (1) is a resonance inductance ratio m, and the expression is as follows:
Figure BDA0003324268530000172
gain K of Y source impedance networkYThe expression of (a) is:
Figure BDA0003324268530000173
wherein k is the winding factor of the Y-type coupling inductor, and the expression is as follows:
Figure BDA0003324268530000174
the reverse gain coefficient of the resonant cavity is KLLC-RThe expression is as follows:
Figure BDA0003324268530000175
wherein FxThe expression is the standard switch operation frequency:
Figure BDA0003324268530000176
wherein f issTo the switching frequency, f1Is a resonant inductor LrAnd a resonance capacitor CrThe frequency at which series resonance occurs is expressed as:
Figure BDA0003324268530000177
Qrthe expression for the inverse quality factor is:
Figure BDA0003324268530000178
wherein R isac-rThe expression is the reverse alternating current equivalent resistance:
Figure BDA0003324268530000179
the converter of the invention has a voltage gain of K when operating in reverseY-LLC-RThe expression is as follows:
Figure BDA0003324268530000181
in order to verify the correctness of the invention, a simulation model is built in simulation software according to the graph 10, a switching tube is set as an ideal device, the voltage of a direct-current voltage source at a high-voltage side is 300V, and the turn ratio of a Y-shaped coupling inductor is N1：N2：N320:70:20, resonant inductance Lr160 muH, capacitance value C of resonance capacitorrTransformer turns ratio N of 100nFt1:Nt220: 80, equivalent load resistance R00.15 Ω, switching frequency fs39.75 kHz. Calculating the obtained series resonance frequency f1＝39.79kHz。
From the expression above, the theoretical output voltage U can be obtained0At 15V, the simulated output voltage U can be seen from FIG. 150About 14.6V. The step-down factor reaches about 20 times, but the turns ratio of the transformer is only 1: 4, the purpose of reducing the difference of the turns of the transformer coil on the premise of maintaining high gain is achieved; at this time, the full bridge operates in the inverter mode, and the dead time needs to be set.
Fifth winding N shown in FIG. 16t2Voltage UNt2Full bridge input current IibResonant cavity current ILcAnd transformer exciting current ItmThe steady state enlarged view of the simulated waveform is consistent with the theoretical derivation result. At the moment, the third switch tube S on the high-voltage side full bridge can be realized3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6The zero voltage of (2) turns on.
From the above expression, the bidirectional Y source-LLC isolated dc-dc converter still has the characteristics of an LLC converter when the power flows in the reverse direction, i.e. by adjusting the second switching tube S2A third switch tube S3And a fourth switching tube S4The fifth switch tube S5And a sixth switching tube S6The frequency of the control signal adjusts the resonant cavity gain to control the output voltage.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. A high-gain bidirectional Y source-LLC isolation direct current-direct current converter is characterized by comprising a Y source impedance network, an LLC resonant network and a high-voltage side full bridge which are sequentially cascaded;
defining that the power flows from the low-pressure side to the high-pressure side as a forward flow, and the power flows from the high-pressure side to the low-pressure side as a reverse flow;
when power flows in the forward direction, the Y-source impedance network boosts the voltage at the low-voltage side of the bidirectional Y-source-LLC isolation direct-current-direct-current converter through the Y-type coupling inductor, converts the voltage into unipolar square wave voltage and outputs the unipolar square wave voltage to the LLC resonant network;
the LLC resonant network filters out a direct-current component through the resonant cavity, converts the unipolar square wave voltage from the Y-source impedance network into bipolar square wave voltage, boosts the voltage again through the transformer and outputs the voltage to the high-voltage side full bridge;
the high-voltage side full bridge realizes alternating-direct current conversion through four switching tubes, converts bipolar square wave voltage from the LLC resonant network into direct current voltage, and finally outputs the direct current voltage to the high-voltage side of the bidirectional Y source-LLC isolation direct current-direct current converter;
when power flows reversely, the high-voltage side full bridge realizes direct-alternating current conversion through four switching tubes, converts the high-voltage side voltage of the bidirectional Y source-LLC isolation direct current-direct current converter into bipolar square wave voltage and outputs the bipolar square wave voltage to the LLC resonant network;
after the voltage of the LLC resonant network is reduced by a transformer, the LLC resonant network provides direct current bias by a resonant cavity, converts the bipolar square wave voltage from the high-voltage side full bridge into unipolar square wave voltage and outputs the unipolar square wave voltage to the Y-source impedance network;
the Y-source impedance network reduces the unipolar square wave voltage from the LLC resonant network again through the Y-type coupling inductor, and the unipolar square wave voltage is output to the low-voltage side of the bidirectional Y-source-LLC isolation direct current-direct current converter after being filtered by the low-voltage side filter capacitor.
2. A high gain bi-directional Y-source-LLC isolated DC-DC converter as claimed in claim 1, wherein the Y-source impedance network comprises a low side filter capacitor (C)0) A first switch tube (S)1) Y-type coupled inductor, first capacitor C1) And a second switching tube (S)2) (ii) a Y-type couplingThe inductor comprises a first winding (N)1) A second winding (N)2) And a third winding (N)3) (ii) a LLC resonant network comprises a resonant capacitor (C)r) Resonant inductor (L)r) And a transformer (T); the transformer (T) comprises a fourth winding (N)t1) And a fifth winding (N)t2) (ii) a The high-side full bridge comprises a third switching tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) And a high-voltage side filter capacitor (C)2)；
Wherein, the low-voltage side filter capacitor (C)0) Is connected with the first switch tube (S)1) And the positive pole of the DC voltage source or equivalent load, the low-voltage side filter capacitor (C)0) The negative pole of the power supply is connected with a direct current voltage source or the negative pole of an equivalent load;
a first switch tube (S)1) Is connected to the first winding (N)1) The same name end of (1);
first winding (N)1) Is connected with the second winding (N)2) And a third winding (N)3) The same name end of (1);
third winding (N)3) Is connected with a first capacitor (C)1) Positive electrode of (2), first capacitor (C)1) Negative pole of (2) is connected with a low-voltage side filter capacitor (C)0) The negative electrode of (1);
second winding (N)2) The different name end of the first switch tube is connected with the second switch tube (S)2) One end of the collector and the resonance capacitor (Cr);
a second switch tube (S)2) Is connected with a low-voltage side filter capacitor (C)0) The negative electrode of (1);
resonance capacitance (C)r) The other end is connected with a resonance inductor (L)r) One terminal of (1), resonant inductance (L)r) Is connected to the fourth winding (N)t1) The same name end of (1);
fourth winding (N)t1) The different name end of the filter is connected with a low-voltage side filter capacitor (C)0) The negative electrode of (1);
fifth winding (N)t2) The same name end of the first switch tube is connected with a third switch tube (S)3) Emitter and fourth switching tube (S)4) A collector electrode of (a); fifth winding (N)t2) Different name end ofIs connected with a fifth switch tube (S)5) Emitter and sixth switching tube (S)6) A collector electrode of (a);
third switch tube (S)3) Is connected with a fifth switch tube (S)5) Collector electrode, high-voltage side filter capacitor (C)2) And a positive electrode of a direct current voltage source or an equivalent load;
fourth switch tube (S)4) Is connected with a sixth switching tube (S)6) Emitter electrode, high-voltage side filter capacitor (C)2) And a dc voltage source or a negative electrode of an equivalent load;
when the low voltage side filter capacitor (C)0) And a first switch tube (S)1) When connected with a DC voltage source, the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) And a high-voltage side filter capacitor (C)2) Connecting with an equivalent load;
when the low voltage side filter capacitor (C)0) And a first switch tube (S)1) When connected with an equivalent load, the third switching tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) And a high-voltage side filter capacitor (C)2) Is connected with a direct current voltage source.
3. A high gain bi-directional Y-source-LLC isolated DC-DC converter as claimed in claim 2, characterized by a low side filter capacitor (C)0) Positive electrode and first switching tube (S)1) Has one end as the emitter, and a low-voltage side filter capacitor (C)0) The negative electrode of the bidirectional Y source-LLC isolation direct current-direct current converter is the other end, a first port is formed, and the voltage of the first port is defined as the low-voltage side voltage of the bidirectional Y source-LLC isolation direct current-direct current converter;
second winding (N) of the inductor coupled in a Y-shape2Different name end and second switch tube (S)2) The collector of (A) is connected to a low-voltage side filter capacitor (C)0) The negative electrode of the power supply is the other end to form a second port, and the voltage of the second port is defined as the high-voltage side voltage of the Y-source impedance network;
with resonant capacitance (C)r) Not in resonance with electricityFeeling (L)r) One side of the connection is one end, with a fourth winding (N)t1) The synonym end of the second port is the other end to form a third port, the voltage of the third port is defined as the low-voltage side voltage of the LLC resonant network, and the third port is cascaded with the second port;
with a fifth winding (N)t2) The same name end of (A) is one end, and a fifth winding (N)t2) The synonym end of the second port is the other end to form a fourth port, and the voltage of the fourth port is defined as the high-voltage side voltage of the LLC resonant network;
with a third switching tube (S)3) Emitter and fourth switching tube (S)4) The collector of (A) is connected to one end of a fifth switching tube (S)5) Emitter and sixth switching tube (S)6) The collector of (a) is the other end, forming a fifth port, and the fifth port is cascaded with the fourth port; with a third switching tube (S)3) Collector and fifth switching tube (S)5) Collector electrode, high-voltage side filter capacitor (C)2) With the positive electrode as one end, and a fourth switching tube (S)4) Emitter and sixth switching tube (S)6) Emitter electrode, high-voltage side filter capacitor (C)2) The negative electrode of the bidirectional Y source-LLC isolation direct current-direct current converter is the other end to form a sixth port, and the voltage of the sixth port is defined as the voltage of the high-voltage side of the bidirectional Y source-LLC isolation direct current-direct current converter;
a transformer T in the LLC resonant network isolates a low-voltage side loop and a high-voltage side loop of the bidirectional Y source-LLC isolation direct current-direct current converter from each other.
4. A high gain bidirectional Y source-LLC isolated DC-DC converter as claimed in claim 2, characterized in that the third switch (S) is arranged such that when the power in the bidirectional Y source-LLC isolated DC-DC converter flows in the forward direction3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) Working in a synchronous rectification or uncontrolled rectification mode;
when the power in the bidirectional Y source-LLC isolation DC-DC converter flows in the forward direction and the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) Operating in synchronous rectification modeIf the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) Or a sixth switching tube (S)6) When the collecting voltage is reduced to a certain value, namely a body diode of the switch tube is switched on, a corresponding switch tube is applied with a conducting signal; if the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) Or a sixth switching tube (S)6) The direction of the collecting voltage is changed from negative to positive, and a corresponding switch tube is applied with a turn-off signal;
when the power in the bidirectional Y source-LLC isolation DC-DC converter flows in the forward direction and the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) When working in the uncontrolled rectifying mode, the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) The driving signals are all locked, and the rectification is completed through the diodes in the corresponding switch tubes;
when the power in the bidirectional Y source-LLC isolation DC-DC converter reversely flows, the third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) Operating in an inverter mode, a third switching tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) Are each applied with a drive signal with a dead zone; third switch tube (S)3) And a fourth switching tube (S)4) And a fifth switching tube (S)5) And a sixth switching tube (S)6) In, the driving signals of the switching tubes of different arms are synchronous, i.e. the third switching tube (S)3) And a fifth switching tube (S)5) A fourth switching tube (S) which is simultaneously turned on and off4) And a sixth switching tube (S)6) The switching tubes of the same bridge arm have a phase difference of half period and dead time, namely a third switching tube (S)3) And a fourth switching tube (S)4) Has a phase difference of half cycle and has a dead time, and a fifth switching tube (S)5) And a sixth switching tube (S)6) Is driven byThere is a half-cycle phase difference in the signals and a dead time.
5. The high-gain bidirectional Y source-LLC isolated DC-DC converter according to claim 4, wherein when the power in the bidirectional Y source-LLC isolated DC-DC converter flows in a forward direction or a reverse direction, the operation modes of the bidirectional Y source-LLC isolated DC-DC converter include a pass-through mode and a non-pass-through mode;
wherein the through mode means that the port voltages of the second port and the third port are zero; non-pass-through mode means that the port voltages of the second port and the third port are not zero;
when the bidirectional Y source-LLC isolation direct current-direct current converter works in a direct-through mode, the first switch tube (S)1) Off, second switching tube (S)2) Conducting;
when the bidirectional Y source-LLC isolation direct current-direct current converter works in the non-direct-through mode, the first switch tube (S)1) Conducting the second switch tube (S)2) And (6) turning off.
6. A high gain bidirectional Y source-LLC isolated DC-DC converter as claimed in claim 4, characterized in that the first switch (S) is arranged such that the power in the bidirectional Y source-LLC isolated DC-DC converter flows in the forward direction1) The driving signal of (2) is locked;
when the power in the bidirectional Y source-LLC isolation DC-DC converter reversely flows, the second switch tube (S)2) The drive signal of (2) is latched.
7. A high gain bidirectional Y source-LLC isolated DC-DC converter as claimed in claim 4, characterized in that the power in the bidirectional Y source-LLC isolated DC-DC converter is applied to the second switching tube (S) in the forward direction2) The duty ratio of the driving signal of (2) is 50%;
when the power in the bidirectional Y source-LLC isolation DC-DC converter flows reversely, the power is applied to the first switch tube (S)1) The duty cycle of the driving signal of (2) is 50%.
8. A high-gain bidirectional Y source-LLC isolated DC-DC converter as claimed in claim 4, wherein when power flows in forward direction, the bidirectional Y source-LLC isolated DC-DC converter has voltage gain KY-LLC-FAnd n is the transformation ratio of the transformer (T), namely:
Figure FDA0003324268520000051
wherein N ist1、Nt2Are respectively a fourth winding (N)t1) A fifth winding (N)t2) The number of turns of the coil of (a);
recording the excitation inductance (L) of the transformertm) And resonant inductance (L)c) Sum and resonance inductance (L)c) The inductance ratio of (1) is a resonance inductance ratio m, and the expression is as follows:
Figure FDA0003324268520000052
then K isY-LLC-FThe expression of (a) is:
Figure FDA0003324268520000053
wherein KYThe gain of the Y source impedance network is expressed as:
Figure FDA0003324268520000054
wherein k is the winding factor of the Y-type coupling inductor, and the expression is as follows:
Figure FDA0003324268520000061
wherein N is1、N2And N3Are respectively the first winding (N)1) A second winding (N)2) And a third winding (N)3) The number of turns of the coil of (a);
KLLC-Fthe forward gain coefficient of a resonant cavity in the LLC resonant network is expressed as follows:
Figure FDA0003324268520000062
wherein FxThe expression is the standard switch operation frequency:
Figure FDA0003324268520000068
wherein f issTo the switching frequency, f1Is a resonant inductor (L)r) And a resonance capacitance (C)r) The frequency at which series resonance occurs is expressed as:
Figure FDA0003324268520000063
Qfis a forward quality factor, and the expression is:
Figure FDA0003324268520000064
wherein R isac-fThe expression is a forward alternating current equivalent resistance:
Figure FDA0003324268520000065
wherein R is0Is an equivalent load (R)0) The resistance value of (c).
9. A high gain bi-directional Y-source-LLC isolated DC-DC converter as claimed in claim 8, whereinThe voltage gain of the bidirectional Y source-LLC isolation direct current-direct current converter is K when power flows reverselyY-LLC-R，KY-LLC-RThe expression of (a) is:
Figure FDA0003324268520000066
KLLC-Rthe expression of the reverse gain coefficient of the resonant cavity in the LLC resonant network is as follows:
Figure FDA0003324268520000067
wherein QrThe expression for the inverse quality factor is:
Figure FDA0003324268520000071
wherein R isac-rThe expression is the reverse alternating current equivalent resistance:
Figure FDA0003324268520000072
eliminating reverse gain coefficient K of resonant cavityLLC-RReverse quality factor QrAnd a reverse AC equivalent resistance Rac-rThe expressions of the remaining symbols are the same as when power flows in the forward direction.
10. The high-gain bidirectional Y source-LLC isolated DC-DC converter according to any one of claims 1 to 9, wherein when power in the bidirectional Y source-LLC isolated DC-DC converter flows in a forward direction, the high-voltage side voltage is adjusted by adjusting the switching frequency of all the switching tubes simultaneously;
when power in the bidirectional Y source-LLC isolation direct current-direct current converter reversely flows, the low-voltage side voltage is adjusted by adjusting the switching frequency of all the switching tubes simultaneously.
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