CN112260552B - Discrete extension phase-shift control method and device for double-active-bridge DC-DC converter - Google Patents

Discrete extension phase-shift control method and device for double-active-bridge DC-DC converter Download PDF

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CN112260552B
CN112260552B CN202011188625.7A CN202011188625A CN112260552B CN 112260552 B CN112260552 B CN 112260552B CN 202011188625 A CN202011188625 A CN 202011188625A CN 112260552 B CN112260552 B CN 112260552B
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bridge
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CN112260552A (en
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沙金
陈丽蓉
周国华
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Southwest Jiaotong University
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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
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • H02M1/15—Arrangements for reducing ripples from dc input or output using active elements

Abstract

The invention discloses a discrete extended phase shift control method and a device of a double-active bridge DC-DC converter, and the method and the device start at each switching periodOutput voltage value U of double-active-bridge DC-DC converter sampled at initial momentoAnd judge UoBelongs to which of m-stage output voltages, and the output voltage boundary of each stage is Uref±jeref，
Figure DDA0002752135740000011
Setting the internal shift ratio of the primary side and the external shift ratio between the secondary sides of the primary side of the double-active-bridge DC-DC converter corresponding to the m-level output voltages respectively, performing phase shift to obtain m groups of discrete phase shift control pulse groups respectively, and performing phase shift according to UoThe corresponding group of switching tubes for controlling the double-active bridge DC-DC converter is selected from the m groups of discrete phase-shift control pulse groups according to the judgment result, so that U is formedoQuickly stabilize in UrefThe transient response speed of the system is accelerated; in addition, the invention also provides the method for optimizing the reflux power, sets the phase shift ratio corresponding to the control pulse group according to the expected output power and the voltage conversion ratio, can reduce the reflux power, and has simple and reliable control loop without a compensation network and a load current loop.

Description

Discrete extension phase-shift control method and device for double-active-bridge DC-DC converter
Technical Field
The invention belongs to the technical field of power electronics, and relates to a discrete expansion phase shift control method and a discrete expansion phase shift control device for a double-active-bridge DC-DC converter.
Background
In the early 90 s of the 20 th century, a Dual Active Bridge (DAB) DC-DC converter was proposed by Doncker. The high-power energy bidirectional flow switch has the advantages of high power density, bidirectional energy flow, easiness in realizing soft switching, high reliability and the like, and is widely applied to the fields of fuel cells, electric automobiles and the like. The control method determines the steady-state performance and the transient performance of the DAB converter. At present, a control mode of the DAB converter is mainly phase shift control, and includes single-phase-shift (SPS) control, extended-phase-shift (EPS) control, dual-phase-shift (DPS) control and the like, and the SPS control principle is simple and easy to implement, but when a voltage conversion ratio is not 1, a larger backflow power and a larger current stress are generated. The EPS control and the DPS control improve the performance of the DAB converter and reduce the reflux power, but the phase-shifting control method cannot improve the transient performance of the DAB converter.
In the applications of power conversion systems of electric automobiles, fuel cell systems of space vehicles and aircrafts and the like, input and load disturbance is inevitable, and the slow dynamic response can cause long disturbance influence time and influence the performance and stability of the system, so that the research on the dynamic performance of the DAB converter is very important. At present, a phase-shift control mode for improving dynamic response of the DAB converter mainly comprises a load current feedback loop method and a PI compensation network design method, and although the two methods can effectively improve the dynamic response speed of the DAB converter to a certain extent, the design difficulty and complexity of a control system are increased, so that the research on a control method capable of simultaneously improving the steady-state performance and the transient performance of the DAB converter is of great importance.
Disclosure of Invention
Aiming at the problems of slow dynamic response and large backflow power of the traditional DAB converter, the invention provides the discrete expansion phase-shifting control method and the discrete expansion phase-shifting control device of the double-active-bridge DC-DC converter, only the output voltage of the double-active-bridge DC-DC converter is needed to be sampled for discrete expansion phase-shifting control, an error amplifier and a corresponding compensation network are not needed to be arranged, the complexity of the system structure is reduced, the stability of the system is enhanced, and the transient response speed of the system is accelerated; the multi-stage discrete control is adopted, so that the output voltage ripple is lower; meanwhile, a backflow power control algorithm is optimized, and backflow power is reduced.
The invention provides a discrete extension phase-shifting control method of a double-active-bridge DC-DC converter, which adopts the technical scheme that:
a double-active bridge DC-DC converter comprises a transformer, a primary side H bridge and a secondary side H bridge, wherein the primary side H bridge and the secondary side H bridge are respectively connected to the primary side and the secondary side of the transformer;
the control method of the double-active-bridge DC-DC converter is used for controlling the X switching tubes and comprises the following steps:
step one, sampling an output voltage value U of the double-active-bridge DC-DC converter at the initial time of each switching periodo；
Step two, generating m groups of discrete phase-shift control pulse groups, wherein m is an even number greater than 2, and the specific method comprises the following steps:
2.1, initializing and setting an output voltage reference value U of the double-active-bridge DC-DC converterrefOutput voltage error reference value erefAnd a sampling period Ts(ii) a Selecting one switching tube from the switching tubes of the primary side H bridge or the secondary side H bridge as a standard switching tube and setting a control signal of the standard switching tube;
2.2, dividing the output voltage of the double-active-bridge DC-DC converter into m levels, wherein the boundary of each level of output voltage is
Figure GDA0003151221390000021
The output voltage level 1 is satisfied
Figure GDA0003151221390000022
Its per unit value corresponding to output power is po_1(ii) a Output voltage level 2 satisfies
Figure GDA0003151221390000023
Its per unit value corresponding to output power is po_2(ii) a … …, respectively; output voltage mth stage satisfies
Figure GDA0003151221390000024
Its per unit value corresponding to output power is po_m；
2.3, setting the per unit value of the output power corresponding to the m-level output voltage to satisfy that p is more than or equal to 0o_m≤po_m-1≤…≤po_1≤1；
And setting the primary side internal shift phase ratio and the external shift phase ratio between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the m-level output voltage respectively, wherein the primary side internal shift phase ratio of the double-active-bridge DC-DC converter corresponding to the ith level output voltage is D1_iAnd the external shift ratio D between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the ith output voltage2_i，i∈[1，m]，D1_iAnd D2_iThe following conditions are satisfied:
0≤D1_i≤D2_i≤1；
Figure GDA0003151221390000025
2.4 obtaining m groups of discrete phase-shift control pulse groups P1To PmObtaining the discrete phase shift control pulse group P corresponding to the ith output voltageiThe method comprises the following steps:
d corresponding to the control signal of the standard switch tube according to the ith-level output voltage1_iAnd D2_iPerforming phase shift to obtain control signals of the rest X-1 switching tubes, and combining the control signals of the standard switching tube and the control signals of the rest X-1 switching tubes to form a discrete phase shift control pulse group P corresponding to the ith-stage output voltagei；
Step three, judging the U obtained by sampling in the step oneoBelongs to which of the m-level output voltages, if the U obtained in the step oneoBelonging to ith stage of m-stage output voltage, selecting discrete phase-shifting control pulse group PiAnd controlling X switching tubes of the double-active-bridge DC-DC converter as an effective control signal group.
Specifically, the primary side H bridge and the secondary side H bridge both comprise two bridge arms, each bridge arm comprises an upper switching tube and a lower switching tube, and X is 8;
performing reflux power optimization control in the step 2.3, and setting the per unit value of the output power corresponding to the m-level output voltage to satisfy pomin≤po_m≤po_m-1≤…≤po_m/2+1≤p≤po_m/2…≤po_1≤1；
Wherein p is a per unit value of the desired output power of the dual active bridge DC-DC converter, and p is Uref 2/R/PNR is the load resistance value of the double-active bridge DC-DC converter,
Figure GDA0003151221390000031
Uin、Uorespectively an input voltage value and an output voltage value of the double-active-bridge DC-DC converter, n is the turn ratio of the primary side and the secondary side of the transformer, fsFor the opening of said dual active bridge DC-DC converterThe off frequency, L is the auxiliary inductance value of the double active bridge DC-DC converter;
pominfor the per unit value of the minimum output power of the double-active bridge DC-DC converter, p is obtained by the following formula calculationomin：
Figure GDA0003151221390000032
Figure GDA0003151221390000033
po(D10) is the primary side internal shift ratio of the dual active bridge DC-DC converter respectively
Figure GDA0003151221390000034
When 0, the per unit value of the output power of the double-active bridge DC-DC converter, k is Uin/nUoIs a voltage conversion ratio;
setting the i-th stage output voltage corresponding to the primary side internal shift phase ratio D of the double-active-bridge DC-DC converter1_iComparison with outward shift between primary and secondary2_iThe following conditions are satisfied:
Figure GDA0003151221390000035
Figure GDA0003151221390000036
pomaxis a per unit value of the critical output power,
Figure GDA0003151221390000037
specifically, an upper switching tube of a first bridge arm of the primary side H bridge is selected as the standard switching tube;
controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D1_iTsObtaining the primary side H bridgeControl signal v of lower switch tube of second bridge armp4And controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D2_iTs/2 obtaining a control signal v of an upper switching tube of the first bridge arm of the secondary side H bridgep5And a control signal v of a lower switching tube of a second bridge arm of the secondary side H bridgep8V is to bep1、vp4、vp5、vp8Respectively shift phase Ts/2 obtaining a control signal v of a lower switching tube of the first bridge arm of the primary side H bridgep2And a control signal v of an upper switching tube of the second bridge arm of the primary side H bridgep3And a control signal v of a lower switch tube of the first bridge arm of the secondary side H bridgep6And a control signal v of an upper switching tube of the second bridge arm of the secondary side H bridgep7V at this timep1、vp2、vp3、vp4、vp5、vp6、vp7、vp8Jointly form said discrete phase-shift control pulse group Pi。
Specifically, the control signal v of the upper switching tube of the first bridge arm of the primary side H bridgep1Is a square wave signal with a duty cycle of 50%.
Based on the control method, the invention also provides a corresponding control device, and the technical scheme is as follows:
a discrete extended phase-shift control device of a double-active-bridge DC-DC converter comprises a transformer, a primary side H-bridge and a secondary side H-bridge, wherein the primary side H-bridge and the secondary side H-bridge are respectively connected to the primary side and the secondary side of the transformer;
the discrete expansion phase-shift control device of the double-active-bridge DC-DC converter comprises a voltage sampling module, a discrete phase-shift control pulse group selector, a discrete phase-shift control pulse group generator, a phase-shift ratio generator and a driving module,
the voltage sampling module is used for sampling the output voltage value U of the double-active-bridge DC-DC converter at the initial moment of each switching periodoAnd output to the said discrete phase shift control pulse group selector;
the above-mentionedThe discrete phase shift control pulse group selector is used for judging the output voltage value U of the double-active-bridge DC-DC converter sampled by the voltage sampling moduleoBelongs to which of m-stage output voltages, wherein m is an even number greater than 2, and the output voltage boundary of each stage is Uref±jeref，
Figure GDA0003151221390000041
The output voltage level 1 is satisfied
Figure GDA0003151221390000042
Figure GDA0003151221390000043
Its per unit value corresponding to output power is po_1(ii) a Output voltage level 2 satisfies
Figure GDA0003151221390000044
Figure GDA0003151221390000045
Its per unit value corresponding to output power is po_2(ii) a … …, respectively; output voltage mth stage satisfies
Figure GDA0003151221390000046
Its per unit value corresponding to output power is po_m；
The phase shift ratio generator is used for setting the per unit value of the output power corresponding to the m-level output voltage to satisfy that p is more than or equal to 0o_m≤po_m-1≤…≤po_1Less than or equal to 1, and generating primary side internal shift phase ratio D of the double-active-bridge DC-DC converter corresponding to m-level output voltages respectively1_1To D1_mComparison with outward shift between primary and secondary2_1To D2_mThe output is output to the discrete phase-shift control pulse group generator, wherein the primary side internal shift ratio of the double-active-bridge DC-DC converter corresponding to the ith stage output voltage is D1_iAnd the external shift ratio D between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the ith output voltage2_i，i∈[1，m]，D1_iAnd D2_iSatisfies the followingConditions are as follows:
0≤D1_i≤D2_i≤1；
Figure GDA0003151221390000047
the discrete phase-shift control pulse group generator is used for selecting one switching tube from the X switching tubes as a standard switching tube, and performing phase shift on a control signal of the standard switching tube according to a primary side internal shift ratio and a primary side external shift ratio of the double-active-bridge DC-DC converter corresponding to m-level output voltages output by the phase-shift ratio generator respectively to obtain m groups of discrete phase-shift control pulse groups P1To PmObtaining the discrete phase shift control pulse group P corresponding to the ith output voltageiThe method comprises the following steps: d corresponding to the control signal of the standard switch tube according to the ith-level output voltage1_iAnd D2_iPerforming phase shift to obtain control signals of the rest X-1 switching tubes, and combining the control signals of the standard switching tube and the control signals of the rest X-1 switching tubes to form a discrete phase shift control pulse group P corresponding to the ith-stage output voltagei；
The discrete phase shift control pulse group selector obtains m groups of discrete phase shift control pulse groups P output by the discrete phase shift control pulse group generator1To PmAnd according to the output voltage value U of the double-active bridge DC-DC converteroFrom m groups of discrete phase-shift control pulse groups P1To PmThe corresponding group of the discrete phase shift control pulse group selector judges the output voltage value U of the double-active bridge DC-DC converter obtained by sampling of the voltage sampling moduleoWhen the voltage belongs to the ith stage in the m-stage output voltage, the discrete phase-shift control pulse group P corresponding to the ith stage output voltage is usediOutputting;
the driving module generates a grid driving signal for controlling the X switching tubes according to a group of discrete phase-shift control pulse group signals output by the discrete phase-shift control pulse group selector, and is used for controlling the X switching tubes of the double-active-bridge DC-DC converter.
Specifically, the primary side H bridge and the secondary side H bridge both comprise two bridge arms, each bridge arm comprises an upper switching tube and a lower switching tube, and X is 8; the connection point of the upper switch tube and the lower switch tube of the first bridge arm in the primary side H bridge is connected with the homonymous end of the primary side winding of the transformer after passing through the auxiliary inductor of the double-active bridge DC-DC converter, and the connection point of the upper switch tube and the lower switch tube of the second bridge arm in the primary side H bridge is connected with the synonym end of the primary side winding of the transformer; the connection point of an upper switch tube and a lower switch tube of a first bridge arm in the secondary H bridge is connected with the homonymous end of the secondary winding of the transformer, and the connection point of an upper switch tube and a lower switch tube of a second bridge arm in the secondary H bridge is connected with the heteronymous end of the secondary winding of the transformer;
the phase-shift ratio generator also comprises a reflux power optimization control module, wherein the reflux power optimization control module sets the per unit value of the output power corresponding to the m-level output voltage to satisfy pomin≤po_m≤po_m-1≤…≤po_m/2+1≤p≤po_m/2…≤p o_11, where p is the per unit value of the desired output power of the dual active bridge DC-DC converter, and p is Uref 2/R/PNR is the load resistance value of the double-active bridge DC-DC converter,
Figure GDA0003151221390000051
Uin、Uorespectively an input voltage value and an output voltage value of the double-active-bridge DC-DC converter, n is the turn ratio of the primary side and the secondary side of the transformer, fsIs the switching frequency of the dual active bridge DC-DC converter, and L is the auxiliary inductance value of the dual active bridge DC-DC converter;
pominfor the per unit value of the minimum output power of the double-active bridge DC-DC converter, p is obtained by the following formula calculationomin：
Figure GDA0003151221390000052
Figure GDA0003151221390000053
po(D10) is the primary side internal shift ratio of the dual active bridge DC-DC converter respectively
Figure GDA0003151221390000061
When 0, the per unit value of the output power of the double-active bridge DC-DC converter, k is Uin/nUoIs a voltage conversion ratio;
the backflow power optimization control module is also provided with an i-th-stage output voltage corresponding to the primary side internal shift ratio D of the double-active-bridge DC-DC converter1_iComparison with outward shift between primary and secondary2_iThe following conditions are satisfied:
Figure GDA0003151221390000062
Figure GDA0003151221390000063
pomaxis a per unit value of the critical output power,
Figure GDA0003151221390000064
specifically, the discrete phase shift control pulse group generator selects the upper switching tube of the first bridge arm of the primary side H bridge as the standard switching tube, and applies the control signal v of the upper switching tube of the first bridge arm of the primary side H bridgep1Phase shift D1_iTs/2 obtaining a control signal v of a lower switching tube of the second bridge arm of the primary side H bridgep4And controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D2_iTs/2 obtaining a control signal v of an upper switching tube of the first bridge arm of the secondary side H bridgep5And a control signal v of a lower switching tube of a second bridge arm of the secondary side H bridgep8V is to bep1、vp4、vp5、vp8Are respectively provided withPhase shift Ts/2 obtaining a control signal v of a lower switching tube of the first bridge arm of the primary side H bridgep2And a control signal v of an upper switching tube of the second bridge arm of the primary side H bridgep3And a control signal v of a lower switch tube of the first bridge arm of the secondary side H bridgep6And a control signal v of an upper switching tube of the second bridge arm of the secondary side H bridgep7V at this timep1、vp2、vp3、vp4、vp5、vp6、vp7、vp8Jointly form said discrete phase-shift control pulse group Pi。
Compared with the prior art, the invention has the beneficial effects that:
compared with the existing voltage closed-loop control, the invention does not need a load current feedback loop and a PI compensation network, only needs to sample output voltage, is simple and easy to implement, is convenient to apply, reduces the complexity of the system structure, enhances the stability and the anti-interference capability of the system, and accelerates the transient response speed of the system.
Compared with the existing voltage closed-loop control, the embodiment of the invention also provides the optimization of the backflow power, improves the transient response speed, reduces the backflow power, reduces the current stress, improves the efficiency of the system and improves the stability of the system.
Compared with the traditional two-stage discrete control, the invention adopts multi-stage discrete control and has lower output voltage ripple.
Drawings
The following description of various embodiments of the invention may be better understood with reference to the following drawings, which schematically illustrate major features of some embodiments of the invention. These figures and examples provide some embodiments of the invention in a non-limiting, non-exhaustive manner. For purposes of clarity, the same reference numbers will be used in different drawings to identify the same or similar elements or structures having the same function.
Fig. 1 is a structural block diagram of a discrete extended phase shift control method and device for a dual-active bridge DC-DC converter according to the present invention.
Fig. 2 is a schematic circuit diagram of a discrete extended phase shift control method and apparatus for a dual active bridge DC-DC converter according to an embodiment of the present invention.
Fig. 3 is a time domain simulation waveform diagram of a dual active bridge DC-DC converter in a certain period under a steady state condition when the discrete extended phase shift control method and apparatus provided by the present invention are applied to the embodiment.
Fig. 4 (a) is a time domain simulation waveform diagram of the discrete extended phase shift control DAB converter output power with a load of 10 Ω and using a reflux power optimization link at a certain time period.
Fig. 4 (b) is a time domain simulation waveform diagram of the output power of the discrete extended phase shift control DAB converter with a load of 10 Ω and without using a reflux power optimization link in the same period.
Fig. 5 (a) is a time domain simulation waveform diagram of the discrete extended phase shift control DAB converter output power with a load of 15 Ω and adopting a reflux power optimization link at a certain time period.
Fig. 5 (b) is a time domain simulation waveform diagram of the output power of the discrete extended phase shift control DAB converter with a load of 15 Ω and without using a reflux power optimization link in the same period.
Fig. 6 (a) and (b) are time domain simulation waveforms of the DAB converter according to the embodiment of the present invention when the load suddenly changes and the input voltage suddenly changes, respectively.
Fig. 7 (a) and (b) are time domain simulation waveforms of the voltage closed loop control DAB converter during sudden load change and sudden input voltage change respectively.
Fig. 8 (a) is a time domain simulation waveform diagram of the output voltage of the DAB converter under four-stage discrete phase shift control.
Fig. 8 (b) is a time domain simulation waveform diagram of the output voltage of the DAB converter under the two-stage discrete phase shift control in the same output power range.
The simulation conditions of fig. 3, 4, 5, 6, and 7 are as follows: reference value U of output voltagerefAn error reference value e of output voltage of 48Vref0.1V, a transformer turn ratio n of 1, and a transformer leakage inductance LsAt 90 μ H, switching frequency fsThe input and output capacitances are both 470 muF at 20 kHz. FIG. 3, FIG. 4 and FIG. 5 are the sameInput voltage UinThe power values corresponding to the control pulse groups in fig. 4 and 5 are the same at 96V.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Specific details of the embodiments described below, such as specific circuit configurations in the embodiments and specific parameters of these circuit elements, are provided to provide a better understanding of the embodiments of the present invention. It will be understood by those skilled in the art that embodiments of the present invention may be practiced without some of these details or with other methods, components, materials, etc.
The invention provides a discrete extended phase-shifting control method which is suitable for a double-active-bridge DC-DC converter, wherein the double-active-bridge DC-DC converter comprises a transformer, a primary side H-bridge and a secondary side H-bridge, wherein the primary side H-bridge and the secondary side H-bridge are respectively connected to the primary side and the secondary side of the transformer, both the primary side H-bridge and the secondary side H-bridge are in a full-bridge structure, and the double-active-bridge DC-DC converter comprises X switching tubes which are formed by two bridge arms in total. As shown in fig. 2, the structure of the dual-active bridge DC-DC converter is shown, in this embodiment, the dual-active bridge DC-DC converter is a two-level converter structure, as shown in fig. 2, each bridge arm includes an upper switch tube and a lower switch tube, X in this embodiment is 8, and the upper switch tube S of the first bridge arm of the primary-side H-bridge is an upper switch tube S of the first bridge arm1And a lower switching tube S2The connection point of the transformer is connected with the homonymous end of the primary winding of the transformer after passing through the auxiliary inductor of the double-active-bridge DC-DC converter, and the upper switching tube S of the second bridge arm in the primary H-bridge3And a lower switching tube S4The connecting point of the transformer is connected with the synonym end of the primary winding of the transformer; upper switch tube S of first bridge arm in secondary side H bridge5And a lower switching tube S6The connecting point of the upper switch tube S is connected with the homonymous end of the secondary winding of the transformer, and the upper switch tube S of the second bridge arm in the secondary H bridge7And a lower switching tube S8The connecting point of the transformer is connected with the different name end of the secondary winding of the transformer.
The double-active-bridge DC-DC converter structure shown in this embodiment needs to consider the optimization problem of the backflow power, and in the double-active-bridge DC-DC converter structures with other multilevel structures, the three-level converter may not have the backflow power, and the backflow power may not be optimized.
The invention comprises a voltage sampling link and a discrete phase-shifting control pulse group generation link, wherein the voltage sampling link is used for sampling the output voltage value U of the double-active-bridge DC-DC converter at the initial moment of each switching period by arranging a voltage sampling moduleo. The discrete phase-shift control pulse group generation link generates m groups of internal and external phase-shift ratios, phase-shift is carried out according to the m groups of internal and external phase-shift ratios to generate m groups of discrete phase-shift control pulse groups, and then a proper control pulse group is selected from the m groups of discrete phase-shift control pulse groups as an effective driving signal of a switching tube according to the output state and the control rule of the converter so as to realize the control of the converter.
The discrete phase-shift control pulse group generation link is firstly initialized by a device, and an output voltage reference value U of a double-active-bridge DC-DC converter is setrefOutput voltage error reference value erefAnd a sampling period Ts(ii) a One switching tube is selected from X switching tubes of the dual-active bridge DC-DC converter as a standard switching tube, and in this embodiment, the dual-active bridge DC-DC converter shown in fig. 2 is taken as an example, because S in the dual-active bridge is1Control signal v ofp1In this embodiment, the upper switch tube S of the first arm of the primary side H-bridge is selected as a square wave signal with a duty ratio of 50%1As a standard switching tube.
Then the discrete phase shift control pulse group selector grades the output voltage and the corresponding power, divides the output voltage of the double-active bridge DC-DC converter into m grades, and surrounds the reference voltage U of the double-active bridge DC-DC converterrefSetting the output voltage boundaries of each stage
Figure GDA0003151221390000081
I.e. the voltage interval of the 1 st stage of the output voltage is
Figure GDA0003151221390000082
Figure GDA0003151221390000091
Its per unit value corresponding to output power is po_1(ii) a The voltage interval of the 2 nd stage of the output voltage is
Figure GDA0003151221390000092
Figure GDA0003151221390000093
Its per unit value corresponding to output power is po_2(ii) a … …, respectively; by analogy, the voltage interval of the mth level of the output voltage is
Figure GDA0003151221390000094
Its per unit value corresponding to output power is po_m。
The 1 st stage of output voltage corresponds to the largest output power, and the mth stage of output voltage corresponds to the smallest output power. The phase shift ratio generator sets the per unit value of the output power corresponding to the m-level output voltage to satisfy that p is more than or equal to 0o_m≤po_m-1≤…≤po_1Less than or equal to 1; and setting the primary side internal shift phase ratio and the primary side external shift phase ratio of the double-active-bridge DC-DC converter corresponding to the m-level output voltage respectively, wherein the primary side internal shift phase ratio of the double-active-bridge DC-DC converter corresponding to the ith level output voltage is D1_iThe external shift phase ratio D between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the ith output voltage2_i，i∈[1，m]，D1_iAnd D2_iThe following conditions are satisfied:
0≤D1_i≤D2_i≤1；
Figure GDA0003151221390000095
the above is a case where the reflux power optimization is not considered, and is applicable to a multi-level topology, such as a DAB converter of a three-level topology. For the two-level topology DAB converter in this embodiment as shown in fig. 2, the optimal control of the reflux power is considered, so a reflux power optimal control module is also provided in the phase shift ratio generator, and according to the m-level output voltage boundary, the per-unit value of the output power of the m-level discrete phase shift control pulse group is set to satisfy pomin≤po_m≤po_m-1≤…≤po_m/2+1≤p≤po_m/2…≤p o_11 or less, wherein，p＝Uref 2/R/PNIs the per unit value of the desired output power, R is the load resistance value, PNThe maximum power output is controlled for the spread phase shift and can be obtained by the following formula:
Figure GDA0003151221390000096
wherein n is the turn ratio of the primary side and the secondary side of the transformer, Uin、UoAre input and output voltages, respectivelysFor the switching frequency, L is the auxiliary inductance value. p is a radical ofominThe per unit value of the minimum output power can be obtained by the following equation:
Figure GDA0003151221390000097
in the formula (I), the compound is shown in the specification,
Figure GDA0003151221390000098
po(D10) is the primary side internal shift ratio of the dual active bridge DC-DC converter respectively
Figure GDA0003151221390000099
Per unit value of output power of 0-time double-active-bridge DC-DC converter, k is Uin/nUoIs the voltage conversion ratio.
In addition, a reflux power optimization control module in the phase shift ratio generator sets the internal shift ratio D of each stage in consideration of minimum reflux power optimization1_1To D1_mComparison with outward Shift2_1To D2_mWherein D is1_1To D1_mIs a switch tube S1And S4Controlling the ratio of the on-time difference of the signals to the half switching period; d2_1To D2_mIs a switch tube S1And S5The ratio of the on-time difference of the control signal to the half-switching period. Wherein the ith stage output voltage considering the optimal control of the reflux power corresponds to the primary side internal shift ratio D of the double-active bridge DC-DC converter1_iComparison with outward shift between primary and secondary2_iThe setting mode is as follows: when D is more than or equal to 01_i≤D2_iWhen the voltage is less than or equal to 1, according to the per unit value p of the output power corresponding to the i-th level output voltageo_i(i ═ 1,2, …, m) and the per unit value p of the critical output poweromax＝
Figure GDA0003151221390000101
In combination with Lagrange's equation and the expression of reflux power, control pulse group Po_i(i ═ 1,2, …, m), the ratio of the internal and external phase shifts of the discrete shift phase signal is obtained by:
Figure GDA0003151221390000102
Figure GDA0003151221390000103
obtaining primary side internal shift phase ratio D of m groups of double-active-bridge DC-DC converters1_1To D1_mComparison with outward shift between primary and secondary2_1To D2_mThen entering a phase-shifting link, and utilizing a discrete phase-shifting control pulse group generator to control signals of the standard switch tube according to D1_1To D1_mAnd D1_1To D1_mAnd performing phase shift to obtain m groups of discrete phase shift control pulse groups P1To PmIn this embodiment, the discrete phase shift control pulse group P corresponding to the ith output voltage is obtainediThe method comprises the following steps: an upper switch tube S of a first bridge arm of a primary side H bridge1Control signal v ofp1Phase shift D1_iTs/2 lower switch tube S for obtaining second bridge arm of primary side H bridge4Control signal v ofp4An upper switch tube S of a first bridge arm of a primary side H bridge1Control signal v ofp1Phase shift D2_iTs/2 obtaining upper switch tube S of first bridge arm of secondary side H bridge5Control signal v ofp5Lower switch tube S of secondary side H bridge second bridge arm8Control signal v ofp8V is to bep1、vp4、vp5、vp8Respectively shift phase Ts/2 lower switch tube S for obtaining first bridge arm of primary side H bridge2Control signal v ofp2Upper switch tube S of second bridge arm of primary side H bridge3Control signal v ofp3Lower switch tube S of first bridge arm of secondary side H bridge6Control signal v ofp6Upper switch tube S of secondary side H bridge arm7Control signal v ofp7V at this timep1、vp2、vp3、vp4、vp5、vp6、vp7、vp8Jointly forming discrete phase-shift control pulse groups Pi。
Then, the discrete phase shift control pulse group selector is used to obtain m discrete phase shift control pulse groups P output by the discrete phase shift control pulse group generator1To PmAnd according to the output voltage value U of the double-active-bridge DC-DC converteroFrom m groups of discrete phase-shift control pulse groups P1To PmIf U is selected, the corresponding group is output to the driving moduleo≤Uref-(m/2-1)erefDescription of UoBelonging to the 1 st stage, the discrete phase-shift control pulse group selector selects the discrete phase-shift control pulse group P with the maximum power1As effective control pulse group output, the driving capability is improved by the driving circuit, and then the switching tube S is controlled1-S8Raising the output voltage; if U isref-(j+1)eref≤Uo≤Uref-jerefDescription of UoBelong to the first
Figure GDA0003151221390000111
Stage, discrete phase shift control pulse group selector selects discrete phase shift control pulse group Pm/2-jAs effective control pulse group output, the driving capability is improved by the driving circuit, and then the switching tube S is controlled1-S8Raising the output voltage; if U isref+jeref≤Uo≤Uref+(j+1)erefThe discrete phase shift control pulse group selector selects the discrete phase shift control pulse group Pm/2+j+1As effective control pulse group output, the driving capability is improved by the driving circuit, and then the switching tube S is controlled1-S8To drop the output voltage; if U iso≥Uref+(m/2-1)erefDescription of UoBelonging to the m-th stage, the discrete phase-shift control pulse group selector selects the discrete phase-shift control pulse group P with the minimum powermAs an effective control pulse group, the output voltage is reduced, and the output voltage is quickly stabilized on the output voltage reference value.
In summary, the discrete extended phase shift control method and apparatus for a dual active bridge DC-DC converter provided by the present invention utilize the voltage sampling module to output the voltage U to the voltage sampling circuit at the initial time of each switching periodoSampling, inputting the sampled data to a discrete phase shift control pulse group selector, wherein the value of the switching period is equal to the value of the sampling period; the phase-shifting ratio generator outputs the internal and external phase-shifting ratios corresponding to each stage of discrete phase-shifting control pulse group according to the per unit value p of the expected output power and the voltage conversion ratio k, and inputs the internal and external phase-shifting ratios into the discrete phase-shifting control pulse group generator, and the optimization of the reflux power is also considered in the two-level structure; the discrete phase-shift control pulse group generator performs phase-shift processing on a control signal of the standard switch tube according to the m-level internal and external phase-shift ratio, and outputs each level of discrete phase-shift control pulse group to the discrete phase-shift control pulse group selector; the discrete phase-shift control pulse group selector selects a proper control pulse group as an effective driving signal by comparing the output voltage with the boundary value of each level of output voltage, and the proper control pulse group is input into a driving module of the DAB converter to drive each switching tube of the DAB converter after being processed. The discrete phase shift control pulse group selector can be composed of a comparator, a D trigger and a logic gate, the comparator is used for comparing the boundary value of the output voltage and the output voltage, the comparison result is input into the data input end of the D trigger, a logic signal is output to the input end of the logic gate at the initial moment of a switching period, and a proper control pulse group is output through one logic gate selected from m to serve as an effective control pulse group.
Taking a four-level discrete phase shift control pulse group as an example, where m is 4, the method of this embodiment is subjected to time domain simulation analysis by Matlab/simulink software, and the result is as follows:
FIG. 3 is the time domain of the DAB converter of this embodiment during a certain period of time under steady state conditionsA simulated oscillogram; in FIG. 3, the horizontal axis represents time (ms) and the vertical axis represents the control pulse group vp(V), output voltage Uo(V) and an inductor current iL(A) In that respect As can be seen from FIG. 3, the discrete extended phase shift control technique proposed by the present invention can realize the control of the output voltage of the DAB converter, and the combination mode of the discrete phase shift pulse groups is 5P2-7P3The output voltage ripple is about 12 mV.
Fig. 4 (a) and (b) are time domain simulation waveforms of output power of the discrete extended phase shift control DAB converter in the same period under the steady state condition, in which the reflux power optimization link and the discrete extended phase shift control DAB converter without the reflux power optimization link are adopted when the load is 10 Ω, and the portion below the horizontal axis is the reflux power. The per unit value of the corresponding output power is larger than the critical output power p when the load is 10 omegaomax. Fig. 5 (a) and (b) are time domain simulation waveforms of output power of the discrete extended phase shift control DAB converter in the same period under the steady state condition, wherein the discrete extended phase shift control DAB converter adopts the reflux power optimization link and does not adopt the reflux power optimization link when the load is 15 Ω. The per unit value of the corresponding output power is less than the critical output power and greater than p when the load is 15 omegaomaxThe corresponding return power is smaller than in the case of (3). From the comparison of fig. 4 (a) and fig. 4 (b), and the comparison of fig. 5 (a) and fig. 5 (b), it can be seen that the critical output power p is greater than or less thanomaxUnder the two loads, the invention adopts the reflux power optimization link to reduce the reflux power.
Fig. 6 (a) and (b) are time domain simulation waveforms of the DAB converter according to the embodiment of the present invention when the load suddenly changes and the input voltage suddenly changes, respectively. Fig. 7 (a) and (b) are time domain simulation waveforms of the voltage closed loop control DAB converter in the load sudden change and the input voltage sudden change respectively. The horizontal axes of fig. 6 and 7 represent time(s), and the vertical axes of fig. 6 (a) and 7 (a) represent output voltage Uo(V) and output current io(A) The vertical axes of (b) in FIG. 6 and (b) in FIG. 7 represent the output voltage Uo(V) and input voltage Uin(V). In fig. 6 (a) and fig. 7 (a), the load changes from 10 Ω to 15 Ω at 0.03s and 0.3s, respectively, the transient response time of the conventional closed-loop control is 0.13s, and the DAB converter using the present invention is almost noneTransient response time, the system immediately enters steady state. In fig. 6 (b) and fig. 7 (b), the input voltage is changed from 96V to 86V at 0.03s and 0.3s, respectively, the transient response time of the conventional closed-loop control is 0.20s, the DAB converter adopting the invention has almost no transient response time, and the system immediately enters the steady state. It can be seen that the DAB converter of the present invention has very good transient response characteristics.
Fig. 8 (a) and (b) are time domain simulation waveforms of output voltages under four-stage and two-stage discrete phase shift control in the same output power range, respectively. It can be seen that the output voltage ripple (0.13V) under the four-stage discrete phase-shift control is obviously smaller than the output voltage ripple (0.42V) under the two-stage discrete phase-shift control, and it can be seen that the multi-stage discrete phase-shift control can obtain smaller output voltage ripple, i.e. the DAB converter of the present invention has smaller output voltage ripple.
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge of those skilled in the art, and the changes are included in the scope of the present invention. Various modifications and variations of the present invention, such as using other structures to charge the capacitor to obtain the output clock signal, or using other structures to generate the control signal that varies with the variation of the output clock signal, can be made by those skilled in the art, and the present invention is intended to cover such modifications and variations as fall within the scope of the appended claims and their equivalents without departing from the design concept of the present invention.

Claims (7)

1. A double-active bridge DC-DC converter comprises a transformer, a primary side H bridge and a secondary side H bridge, wherein the primary side H bridge and the secondary side H bridge are respectively connected to the primary side and the secondary side of the transformer;
the control method of the double-active-bridge DC-DC converter is used for controlling the X switching tubes and comprises the following steps:
step one, sampling an output voltage value U of the double-active-bridge DC-DC converter at the initial time of each switching periodo；
Step two, generating m groups of discrete phase-shift control pulse groups, wherein m is an even number greater than 2, and the specific method comprises the following steps:
2.1, initializing and setting an output voltage reference value U of the double-active-bridge DC-DC converterrefOutput voltage error reference value erefAnd a sampling period Ts(ii) a Selecting one switching tube from the switching tubes of the primary side H bridge or the secondary side H bridge as a standard switching tube and setting a control signal of the standard switching tube;
2.2, dividing the output voltage of the double-active-bridge DC-DC converter into m levels, wherein the boundary of each level of output voltage is Uref±jeref，
Figure FDA0003168178490000011
The output voltage level 1 is satisfied
Figure FDA0003168178490000012
Its per unit value corresponding to output power is po_1(ii) a Output voltage level 2 satisfies
Figure FDA0003168178490000013
Its per unit value corresponding to output power is po_2(ii) a … …, respectively; output voltage mth stage satisfies
Figure FDA0003168178490000014
Its per unit value corresponding to output power is po_m；
2.3, setting the per unit value of the output power corresponding to the m-level output voltage to satisfy that p is more than or equal to 0o_m≤po_m-1≤...≤po_1Less than or equal to 1; and setting the primary side internal shift phase ratio and the external shift phase ratio between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the m-level output voltage respectively, wherein the primary side internal shift phase ratio of the double-active-bridge DC-DC converter corresponding to the ith level output voltage is D1_iOutput of the ith stageThe voltage corresponds to the external shift ratio D between the primary side and the secondary side of the double-active-bridge DC-DC converter2_i，i∈[1，m]，D1_iAnd D2_iThe following conditions are satisfied:
0≤D1_i≤D2_i≤1；
Figure FDA0003168178490000015
2.4 obtaining m groups of discrete phase-shift control pulse groups P1To PmObtaining the discrete phase shift control pulse group P corresponding to the ith output voltageiThe method comprises the following steps:
d corresponding to the control signal of the standard switch tube according to the ith-level output voltage1_iAnd D2_iPerforming phase shift to obtain control signals of the rest X-1 switching tubes, and combining the control signals of the standard switching tube and the control signals of the rest X-1 switching tubes to form a discrete phase shift control pulse group P corresponding to the ith-stage output voltagei；
Step three, judging the U obtained by sampling in the step oneoBelongs to which of the m-level output voltages, if the U obtained in the step oneoBelonging to ith stage of m-stage output voltage, selecting discrete phase-shifting control pulse group PiAnd controlling X switching tubes of the double-active-bridge DC-DC converter as an effective control signal group.
2. The discrete extended phase-shifting control method of the dual-active bridge DC-DC converter according to claim 1, wherein the primary side H bridge and the secondary side H bridge both comprise two bridge arms, each bridge arm comprises an upper switching tube and a lower switching tube, and X is 8;
performing reflux power optimization control in the step 2.3, and setting the per unit value of the output power corresponding to the m-level output voltage to satisfy pomin≤po_m≤po_m-1≤...≤po_m/2+1≤p≤po_m/2...≤po_1≤1；
Wherein p is the desired output of the dual active bridge DC-DC converterPer unit value of output, p ═ Uref 2/R/PNR is the load resistance value of the double-active bridge DC-DC converter,
Figure FDA0003168178490000021
Uin、Uorespectively an input voltage value and an output voltage value of the double-active-bridge DC-DC converter, n is the turn ratio of the primary side and the secondary side of the transformer, fsIs the switching frequency of the dual active bridge DC-DC converter, and L is the auxiliary inductance value of the dual active bridge DC-DC converter;
pominfor the per unit value of the minimum output power of the double-active bridge DC-DC converter, p is obtained by the following formula calculationomin：
Figure FDA0003168178490000022
Figure FDA0003168178490000023
po(D10) is the primary side internal shift ratio of the dual active bridge DC-DC converter respectively
Figure FDA0003168178490000024
When 0, the per unit value of the output power of the double-active bridge DC-DC converter, k is Uin/nUoIs a voltage conversion ratio;
setting the i-th stage output voltage corresponding to the primary side internal shift phase ratio D of the double-active-bridge DC-DC converter1_iComparison with outward shift between primary and secondary2_iThe following conditions are satisfied:
Figure FDA0003168178490000025
Figure FDA0003168178490000026
pomaxis a per unit value of the critical output power,
Figure FDA0003168178490000027
3. the discrete extended phase-shifting control method of the double-active-bridge DC-DC converter according to claim 2, characterized in that an upper switching tube of a first bridge arm of the primary-side H-bridge is selected as the standard switching tube;
controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D1_iTs/2 obtaining a control signal v of a lower switching tube of the second bridge arm of the primary side H bridgep4And controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D2_iTs/2 obtaining a control signal v of an upper switching tube of the first bridge arm of the secondary side H bridgep5And a control signal v of a lower switching tube of a second bridge arm of the secondary side H bridgep8V is to bep1、vp4、vp5、vp8Respectively shift phase Ts/2 obtaining a control signal v of a lower switching tube of the first bridge arm of the primary side H bridgep2And a control signal v of an upper switching tube of the second bridge arm of the primary side H bridgep3And a control signal v of a lower switch tube of the first bridge arm of the secondary side H bridgep6And a control signal v of an upper switching tube of the second bridge arm of the secondary side H bridgep7V at this timep1、vp2、vp3、vp4、vp5、vp6、vp7、vp8Jointly form said discrete phase-shift control pulse group Pi。
4. The discrete extended phase-shifting control method for the dual-active bridge DC-DC converter according to claim 3, wherein the control signal v of the upper switching tube of the first leg of the primary side H bridgep1Is a square wave signal with a duty cycle of 50%.
5. A discrete extended phase-shift control device of a double-active-bridge DC-DC converter comprises a transformer, a primary side H-bridge and a secondary side H-bridge, wherein the primary side H-bridge and the secondary side H-bridge are respectively connected to the primary side and the secondary side of the transformer;
it is characterized in that the discrete expansion phase-shift control device of the double-active bridge DC-DC converter comprises a voltage sampling module, a discrete phase-shift control pulse group selector, a discrete phase-shift control pulse group generator, a phase-shift ratio generator and a driving module,
the voltage sampling module is used for sampling the output voltage value U of the double-active-bridge DC-DC converter at the initial moment of each switching periodoAnd output to the said discrete phase shift control pulse group selector;
the discrete phase shift control pulse group selector is used for judging the output voltage value U of the double-active-bridge DC-DC converter sampled by the voltage sampling moduleoBelongs to which of m-stage output voltages, wherein m is an even number greater than 2, and the output voltage boundary of each stage is Uref±jeref，
Figure FDA0003168178490000031
The output voltage level 1 is satisfied
Figure FDA0003168178490000032
Figure FDA0003168178490000033
Its per unit value corresponding to output power is po_1(ii) a Output voltage level 2 satisfies
Figure FDA0003168178490000034
Figure FDA0003168178490000035
Its per unit value corresponding to output power is po_2(ii) a … …, respectively; output voltage mth stage satisfies
Figure FDA0003168178490000036
Its per unit value corresponding to output power is po_m；
The phase shift ratio generator is used for setting the per unit value of the output power corresponding to the m-level output voltage to satisfy that p is more than or equal to 0o_m≤po_m-1≤...≤po_1Less than or equal to 1, and generating primary side internal shift phase ratio D of the double-active-bridge DC-DC converter corresponding to m-level output voltages respectively1_1To D1_mComparison with outward shift between primary and secondary2_1To D2_mThe output is output to the discrete phase-shift control pulse group generator, wherein the primary side internal shift ratio of the double-active-bridge DC-DC converter corresponding to the ith stage output voltage is D1_iAnd the external shift ratio D between the primary side and the secondary side of the double-active-bridge DC-DC converter corresponding to the ith output voltage2_i，i∈[1，m]，D1_iAnd D2_iThe following conditions are satisfied:
0≤D1_i≤D2_i≤1；
Figure FDA0003168178490000041
the discrete phase-shift control pulse group generator is used for selecting one switching tube from the X switching tubes as a standard switching tube, and performing phase shift on a control signal of the standard switching tube according to a primary side internal shift ratio and a primary side external shift ratio of the double-active-bridge DC-DC converter corresponding to m-level output voltages output by the phase-shift ratio generator respectively to obtain m groups of discrete phase-shift control pulse groups P1To PmObtaining the discrete phase shift control pulse group P corresponding to the ith output voltageiThe method comprises the following steps: d corresponding to the control signal of the standard switch tube according to the ith-level output voltage1_iAnd D2_iPerforming phase shift to obtain control signals of the rest X-1 switching tubes, and combining the control signals of the standard switching tube and the control signals of the rest X-1 switching tubes to form a discrete phase shift control pulse group P corresponding to the ith-stage output voltagei；
The discrete phase shift control pulse group selector obtains m groups of discrete phase shift control pulse groups P output by the discrete phase shift control pulse group generator1To PmAnd according to the output voltage value U of the double-active bridge DC-DC converteroFrom m groups of discrete phase-shift control pulse groups P1To PmThe corresponding group of the discrete phase shift control pulse group selector judges the output voltage value U of the double-active bridge DC-DC converter obtained by sampling of the voltage sampling moduleoWhen the voltage belongs to the ith stage in the m-stage output voltage, the discrete phase-shift control pulse group P corresponding to the ith stage output voltage is usediOutputting;
the driving module generates a grid driving signal for controlling the X switching tubes according to a group of discrete phase-shift control pulse group signals output by the discrete phase-shift control pulse group selector, and is used for controlling the X switching tubes of the double-active-bridge DC-DC converter.
6. The discrete extended phase-shifting control device of the dual-active bridge DC-DC converter according to claim 5, wherein the primary side H bridge and the secondary side H bridge both comprise two bridge arms, each bridge arm comprises an upper switch tube and a lower switch tube, and X is 8; the connection point of the upper switch tube and the lower switch tube of the first bridge arm in the primary side H bridge is connected with the homonymous end of the primary side winding of the transformer after passing through the auxiliary inductor of the double-active bridge DC-DC converter, and the connection point of the upper switch tube and the lower switch tube of the second bridge arm in the primary side H bridge is connected with the synonym end of the primary side winding of the transformer; the connection point of an upper switch tube and a lower switch tube of a first bridge arm in the secondary H bridge is connected with the homonymous end of the secondary winding of the transformer, and the connection point of an upper switch tube and a lower switch tube of a second bridge arm in the secondary H bridge is connected with the heteronymous end of the secondary winding of the transformer;
the phase-shift ratio generator also comprises a reflux power optimization control module, wherein the reflux power optimization control module sets the per unit value of the output power corresponding to the m-level output voltage to satisfy pomin≤po_m≤po_m-1≤...≤po_m/2+1≤p≤po_m/2...≤po_11, where p is the per unit value of the desired output power of the dual active bridge DC-DC converter, and p is Uref 2/R/PNR is the load resistance value of the double-active bridge DC-DC converter,
Figure FDA0003168178490000042
Uin、Uorespectively an input voltage value and an output voltage value of the double-active-bridge DC-DC converter, n is the turn ratio of the primary side and the secondary side of the transformer, fsIs the switching frequency of the dual active bridge DC-DC converter, and L is the auxiliary inductance value of the dual active bridge DC-DC converter;
pominfor the per unit value of the minimum output power of the double-active bridge DC-DC converter, p is obtained by the following formula calculationomin：
Figure FDA0003168178490000051
Figure FDA0003168178490000052
po(D10) is the primary side internal shift ratio of the dual active bridge DC-DC converter respectively
Figure FDA0003168178490000053
When 0, the per unit value of the output power of the double-active bridge DC-DC converter, k is Uin/nUoIs a voltage conversion ratio;
the backflow power optimization control module is also provided with an i-th-stage output voltage corresponding to the primary side internal shift ratio D of the double-active-bridge DC-DC converter1_iComparison with outward shift between primary and secondary2_iThe following conditions are satisfied:
Figure FDA0003168178490000054
Figure FDA0003168178490000055
pomaxis a per unit value of the critical output power,
Figure FDA0003168178490000056
7. the discrete extended phase-shift control device of the dual-active bridge DC-DC converter according to claim 6, wherein the discrete phase-shift control pulse group generator selects the upper switch tube of the first bridge arm of the primary H bridge as the standard switch tube, and applies the control signal v of the upper switch tube of the first bridge arm of the primary H bridgep1Phase shift D1_iTs/2 obtaining a control signal v of a lower switching tube of the second bridge arm of the primary side H bridgep4And controlling a control signal v of an upper switching tube of a first bridge arm of the primary side H bridgep1Phase shift D2_iTs/2 obtaining a control signal v of an upper switching tube of the first bridge arm of the secondary side H bridgep5And a control signal v of a lower switching tube of a second bridge arm of the secondary side H bridgep8V is to bep1、vp4、vp5、vp8Respectively shift phase Ts/2 obtaining a control signal v of a lower switching tube of the first bridge arm of the primary side H bridgep2And a control signal v of an upper switching tube of the second bridge arm of the primary side H bridgep3And a control signal v of a lower switch tube of the first bridge arm of the secondary side H bridgep6And a control signal v of an upper switching tube of the second bridge arm of the secondary side H bridgep7V at this timep1、vp2、vp3、vp4、vp5、vp6、vp7、vp8Jointly form said discrete phase-shift control pulse group Pi。
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