CN112117908A - Frequency conversion phase shift modulation device and method for double-active-bridge series resonant converter circuit - Google Patents

Frequency conversion phase shift modulation device and method for double-active-bridge series resonant converter circuit Download PDF

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CN112117908A
CN112117908A CN202010802117.7A CN202010802117A CN112117908A CN 112117908 A CN112117908 A CN 112117908A CN 202010802117 A CN202010802117 A CN 202010802117A CN 112117908 A CN112117908 A CN 112117908A
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phase shift
transmission power
bridge circuit
switching
secondary side
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张宇
杨立新
徐应年
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Wuhan Hyderabad Technology Co ltd
Huazhong University of Science and Technology
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Wuhan Hyderabad Technology Co ltd
Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention discloses a frequency conversion phase-shifting modulation device and method of a double-active-bridge series resonant converter circuit, wherein the double-active-bridge series resonant converter circuit comprises a primary side H-bridge circuit, a resonant capacitor, an auxiliary inductor, a transformer, a secondary side H-bridge circuit, a primary side voltage stabilizing capacitor and a secondary side voltage stabilizing capacitor; obtaining a combination of a switching frequency ratio and a phase shift angle according to a per unit transmission power instruction and a voltage gain of a converter and a piecewise linearization method; and controlling the on and off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit. The invention makes the converter obtain nearly the highest efficiency according to the principle of efficiency optimization.

Description

Frequency conversion phase shift modulation device and method for double-active-bridge series resonant converter circuit
Technical Field
The invention belongs to the field of direct-current power supply conversion, and particularly relates to a frequency conversion phase-shifting modulation device and method for a double-active-bridge series resonant converter circuit.
Background
The dual-active-bridge series resonant converter (DB-SRC) has the advantages of bidirectional energy flow, easiness in realizing soft switching, high power density and the like, wherein the resonant capacitor has the function of isolating direct current, and can effectively protect the resonant inductor and the high-frequency transformer when a load is in short circuit. The converter is widely applied to the fields of new energy electric automobiles, large-scale energy storage systems, renewable energy sources and the like. In addition, the DB-SRC has flexible control modes, such as: frequency conversion modulation mode and phase shift modulation mode.
When the DB-SRC adopts frequency conversion modulation, soft switching of all switching tubes is easy to realize. However, for a wide voltage variation range application scenario, the converter requires a very wide operating frequency. This makes the design of the magnetic elements such as transformers and inductors difficult, and also increases the overall cost of the converter. In addition, when frequency conversion modulation is adopted, because the LC resonant tank and the output end are in a series structure, when the impedance of the LC resonant tank reaches the minimum, the voltage gain is only 1 at the maximum, and the output voltage is difficult to control under light load or no-load conditions. If a phase-shift modulation mode is adopted, the switching frequency is fixed, various problems existing in frequency conversion modulation can be effectively solved, meanwhile, the voltage regulation range is wide, and the voltage gain can be larger than 1 or smaller than 1. Phase shift control has various modes such as single phase shift control, double phase shift control, triple phase shift control, etc., but Single Phase Shift (SPS) modulation has some problems, such as: soft switching range is limited, backflow power is large, etc. Therefore, the optimal design can be performed by a Double Phase Shift (DPS) modulation mode and a Triple Phase Shift (TPS) modulation mode, but the DPS modulation mode and the TPS modulation mode are both complex.
Aiming at the defects of the DB-SRC in frequency conversion modulation or phase shift modulation, the frequency conversion modulation and the phase shift modulation can be combined to form a frequency conversion phase shift modulation mode. However, on the premise that the transmission power and the voltage gain are fixed, if the operating frequency and the phase shift angle are not properly selected, the effective current value of the resonant tank and the current stress of the switching tube are both increased rapidly, which leads to a serious decrease in the operating efficiency of the converter. Therefore, it is necessary to select the optimized operating frequency and phase shift angle from the viewpoint of efficiency optimization.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a frequency conversion phase shift modulation device and a frequency conversion phase shift modulation method for a double-active-bridge series resonant converter circuit, aiming at determining the optimal working frequency and phase shift angle in the process of adjusting the output voltage aiming at DB-SRC of frequency conversion phase shift modulation according to the principle of efficiency optimization, so that the converter can obtain nearly the highest efficiency.
To achieve the above object, according to an aspect of the present invention, there is provided a frequency conversion phase shift modulation apparatus for a dual-active-bridge series resonant converter circuit, the dual-active-bridge series resonant converter circuit includes a primary side H-bridge circuit, a resonant capacitor Cr, an auxiliary inductor Lr, a transformer, a secondary side H-bridge circuit, a primary side voltage stabilizing capacitor C1, and a secondary side voltage stabilizing capacitor C2;
the direct current side of the primary side H-bridge circuit is connected with a primary side voltage source, and the alternating current side of the primary side H-bridge circuit is connected with the primary side of the transformer through a resonant capacitor Cr and an auxiliary inductor Lr; the alternating current side of the secondary side H-bridge circuit is connected with the secondary side of the transformer, and the direct current side of the secondary side H-bridge circuit is connected with a secondary side load;
the primary side voltage-stabilizing capacitor C1 and the secondary side voltage-stabilizing capacitor C2 are respectively connected in parallel with the primary side H-bridge circuit and the secondary side H-bridge circuit.
The frequency conversion phase shift modulation device comprises a direct power control unit, a piecewise linearization frequency conversion phase shift modulation unit and a pulse width generation unit. The input end of the direct power control unit is connected with a primary side direct current bus and a secondary side direct current bus of a main circuit of the double-active-bridge series resonant converter, and the output end of the direct power control unit is connected with the piecewise linearization frequency conversion phase shift modulation unit; the output end of the piecewise linearization frequency conversion phase shift modulation unit is connected with the pulse width generation units of the primary side H-bridge circuit and the secondary side H-bridge circuit;
the direct power control unit is used for acquiring the actual output voltage of the converter and obtaining an instruction value of per unit transmission power according to the error between the acquired actual output voltage and the expected voltage;
and the piecewise linearization frequency conversion phase shift modulation unit is used for determining the switching frequency and the phase shift angle according to the per unit transmission power instruction and the voltage gain and a piecewise linearization method and sending the switching frequency and the phase shift angle to the pulse width generation unit. The pulse width generating unit is used for controlling the on-off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit, so that the effective value of the resonant current and the stress of the switching current are optimized, and the efficiency of the converter is further optimized;
the pulse width generating unit is used for generating two groups of square wave signals with adjustable frequency and 50% duty ratio and adjusting the phase difference between the two groups of square wave signals;
the piecewise linearization method is to obtain the switching frequency and the phase shift angle according to the principle of minimizing the effective value of the resonant current and minimizing the current stress. The specific determination method is that a frequency conversion modulation mode or a phase shift modulation mode is selected according to the value of the per unit transmission power instruction, and then the switching frequency ratio and the phase shift angle are determined. When the per unit transmission power instruction is smaller than a set demarcation value 1, a phase shift modulation mode is adopted, the frequency is set to be a maximum allowable switching frequency ratio in a fixed and unchangeable mode, and a phase shift angle is determined according to the transmission power instruction; when the per unit transmission power instruction is between the boundary value 1 and the boundary value 2, adopting variable frequency modulation, fixing the phase shift angle, and determining the switching frequency ratio according to the transmission power instruction; when the per unit transmission power instruction is larger than the demarcation value 2, phase shift modulation is adopted, the frequency is fixedly and invariably set as the minimum allowable switching frequency ratio, and the phase shift angle is determined according to the transmission power instruction.
Wherein the voltage gain is M ═ nV2/V1N is the turn ratio of the primary side and the secondary side of the transformer, V1For a DC input voltage, V, connected to a primary side H-bridge circuit2Is a direct current output voltage connected with a secondary side H-bridge circuit;
further, the primary side H-bridge circuit includes: four switching devices, respectively: the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the corresponding anti-parallel diode and the voltage stabilizing capacitor on the primary side; the primary side voltage stabilizing capacitor is connected in parallel with the primary side H-bridge circuit.
Further, the secondary side H-bridge circuit includes: four switching devices, respectively: a fifth switching tube, a sixth switching tube, a seventh switching tube, an eighth switching tube, a corresponding anti-parallel diode and a voltage stabilizing capacitor on the secondary side; and the voltage stabilizing capacitor on the secondary side is connected with the single-phase H-bridge circuit on the secondary side in parallel.
The invention proposes two control variables: a switching frequency ratio Fn defined as a ratio of the switching frequency to the resonance frequency; the phase shift angle theta is defined as the phase angle that the driving signal of the fifth switching tube in the secondary side H-bridge circuit lags behind the driving signal of the first switching tube in the primary side H-bridge circuit;
wherein the resonant frequency is
Figure RE-GDA0002757783820000041
Cr is a resonance capacitor, and Lr is an auxiliary inductor.
The invention also provides a modulation method for frequency conversion and phase shift, which comprises the following steps:
step 1: the direct power control unit acquires the output voltage of the converter and obtains a per unit transmission power instruction according to the error between the acquired output voltage and the expected voltage;
step 2: the piecewise linearization frequency conversion phase shift modulation unit obtains a combination of a piecewise switching frequency ratio Fn and a phase shift angle theta according to a per unit transmission power instruction and the voltage gain of the converter by a piecewise linearization method;
and step 3: the pulse width generating unit controls the on and off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit according to the combination of the switching frequency ratio Fn and the phase shift angle theta.
Further, in step 2, according to the per unit transmission power command and the voltage gain of the converter, the combination of the switching frequency ratio Fn and the phase shift angle θ is obtained by a piecewise linearization method, and the specific process includes:
(1) calculating the transmission power of the converter according to the transformer transformation ratio, the input voltage at the direct current side of the primary side H bridge circuit, the output voltage at the direct current side of the secondary side H bridge circuit, the switching frequency ratio Fn and the voltage gain, and calculating the per-unit transmission power of the converter according to the reference transmission power of the converter;
(2) according to the maximum permissible switching frequency ratio FnmaxMinimum allowable switching frequency ratio FnminDetermining the relation between a fixed phase shift angle A and a voltage gain M in a frequency conversion mode, wherein the expression is as follows:
Figure RE-GDA0002757783820000042
(3) the boundary values Po1 and Po2 of the transmission power are determined according to equations (1) and (2). When the per unit transmission power instruction is larger than Po2, a phase-shifting modulation mode is adopted, and the switching frequency ratio is fixed to a minimum allowable value Fnmin(ii) a When the per-unit transmission power command is smaller than Po1, the switching frequency ratio is fixed to the maximum allowable value Fnmax. Meanwhile, determining a phase shift angle according to the principle shown in the formula (3); when the transmission power is less than Po1 and greater than Po2, the modulation mode of the frequency conversion is selected, the phase shift angle is fixed to A rad, and the switching frequency is determined according to equation (3).
Figure RE-GDA0002757783820000051
Figure RE-GDA0002757783820000052
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
(1) when the DB-SRC works in light load or no load, the invention adopts phase-shift modulation to the DB-SRC, can effectively solve the problem that the voltage gain of the series resonant converter can not be flexibly adjusted, and the converter obtains higher efficiency because the switch tube is easy to realize zero voltage switching-on.
(2) When the DB-SRC transmission power is between Po2 and Po1, the frequency modulation mode is adopted for the converter, the phase shift angle is fixed, and a lower current effective value and current stress can be obtained at the moment, so that the efficiency of the converter is improved; while at the same time obtaining a wide range of voltage regulation capabilities.
(3) When the DB-SRC works in a heavy load, the phase shift modulation is adopted for the converter, the switching frequency of the converter is low, and the full-range ZVS can be obtained to obtain high efficiency.
Drawings
Fig. 1 is a block diagram of a frequency conversion phase shift modulation apparatus of a dual-active-bridge series resonant converter circuit provided in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a main circuit topology and a frequency conversion phase shift modulation method of a dual-active-bridge series resonant converter provided in an embodiment of the present invention;
fig. 3(a) is a per-unit current effective value and a per-unit current stress optimization control locus when the voltage gain M is 0.75 according to an embodiment of the present invention;
fig. 3(b) is a two-dimensional plan view of a piecewise-linearized optimized control trajectory when the voltage gain M is 0.75 according to an embodiment of the present invention;
FIG. 4 is a graph of voltage gain M versus phase shift angle A, A1, A2 according to an embodiment of the present invention;
FIG. 5 is a plot of voltage gain M versus power at the boundary Po1 and Po2 in accordance with the present invention;
FIG. 6 is a chart of the ZVS range under the condition that Fn is more than or equal to 1.1 and less than or equal to 1.6 according to the invention;
FIG. 7 is a waveform illustrating the operation of the phase shift control under light load according to the present invention;
fig. 8 is a waveform of operation of the present invention under control of Po1< p < Po2 down-conversion phase-shifting.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Referring to fig. 1, a block diagram of a frequency conversion phase shift modulation apparatus of a dual-active-bridge series resonant converter circuit provided by the present invention includes the dual-active-bridge series resonant converter circuit and the frequency conversion phase shift modulation apparatus, where the dual-active-bridge series resonant converter circuit mainly includes a primary side single-phase H-bridge circuit, a resonant capacitor Cr, an auxiliary inductor Lr, a transformer T, a secondary side single-phase H-bridge circuit, a primary side voltage stabilizing capacitor C1, and a secondary side voltage stabilizing capacitor C2; the control part comprises a direct power control unit and a piecewise linearization frequency conversion phase shift modulation unit;
the direct current side of the primary side H bridge is connected with a primary side voltage source, and the alternating current side of the primary side H bridge is connected with the primary side of a transformer T through a resonant capacitor Cr and an auxiliary inductor Lr; the alternating current side of the secondary side H bridge is connected with the secondary side of the transformer T, and the direct current side of the secondary side H bridge is connected with a secondary side load; the input end of the direct power control unit is respectively connected with a primary side voltage source V1 and a secondary side voltage source V of the DB-SRC main circuit2The output end of the phase-shifting unit is connected with the phase-shifting unit; the primary side voltage-stabilizing capacitor C1 and the secondary side voltage-stabilizing capacitor C2 are respectively connected with the primary side H bridge circuit in parallel and the secondary side H bridge circuit in parallel; the output end of the frequency conversion phase shift modulation unit is respectively connected with the pulse width generation units of the primary side H-bridge circuit and the secondary side H-bridge circuit; a direct power control unit for sampling to obtain a real-time value V of the output voltage2And according to the collected actual output voltage and the expected output voltage VrefComparing to obtain an instruction value p of per unit transmission power; and the piecewise linearization frequency conversion phase shift modulation unit is used for determining the switching frequency and the phase shift angle according to the per unit transmission power instruction and the voltage gain and a piecewise linearization method and sending the switching frequency and the phase shift angle to the pulse width generation unit. The pulse width generating unit is used for controlling the on-off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit, so that the effective value of the resonant current and the stress of the switching current are optimized, and the efficiency of the converter is further optimized; the pulse width generating unit is used for generating square wave signals with adjustable frequency and 50% duty ratio and adjusting the phase difference between the two groups of square wave signals. The pulse width generating unit controls the on-off of the switch tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit to realize the optimization of the effective value of the resonant current and the stress of the switch current,the efficiency of the converter is optimized; the piecewise linearization method is to obtain the switching frequency and the phase shift angle according to the principle of minimizing the effective value of the resonant current and minimizing the current stress. The specific determination method is that a frequency conversion modulation mode or a phase shift modulation mode is selected according to the value of the per unit transmission power instruction, and then the switching frequency ratio and the phase shift angle are determined. When the per unit transmission power instruction is smaller than a set demarcation value 1, a phase shift modulation mode is adopted, the frequency is set to be a maximum allowable switching frequency ratio in a fixed and unchangeable mode, and a phase shift angle is determined according to the transmission power instruction; when the per unit transmission power instruction is between the boundary value 1 and the boundary value 2, adopting variable frequency modulation, fixing the phase shift angle, and determining the switching frequency ratio according to the transmission power instruction; when the per unit transmission power instruction is larger than the demarcation value 2, phase shift modulation is adopted, the frequency is fixedly and invariably set as the minimum allowable switching frequency ratio, and the phase shift angle is determined according to the transmission power instruction.
Wherein the voltage gain is M ═ nV2/V1N is the turn ratio of the primary side and the secondary side of the transformer, V1For the DC bus voltage, V, connected to the primary side H-bridge2The direct current bus voltage is connected with the secondary side H-bridge circuit;
specifically, as shown in fig. 2, the primary-side H-bridge circuit includes: four switching devices, respectively: first switch tube S1A second switch tube S2A third switch tube S3And a fourth switching tube S4And a corresponding anti-parallel diode D1、D2、D3、D4And a primary side voltage stabilizing capacitor C1(ii) a Primary side voltage stabilizing capacitor C1Connected in parallel with the primary side H-bridge circuit; the secondary side H-bridge circuit includes: four switching devices, respectively fifth switching tube S5The sixth switching tube S6Seventh switching tube S7The eighth switching tube S8And a corresponding anti-parallel diode D5、D6、D7、D8And a secondary side voltage stabilizing capacitor C2(ii) a Secondary side voltage stabilizing capacitor C2And is connected with the secondary side H-bridge circuit in parallel.
The invention includes two control variables: a switching frequency ratio Fn defined as a ratio of the switching frequency to the resonance frequency, Fn being 1.1 or more and 1.6 or less; the phase shift angle theta is defined as the phase angle of a driving signal of a fifth switching tube in the secondary side H-bridge circuit lagging behind a driving signal of a first switching tube in the primary side H-bridge circuit, and theta is more than or equal to 0 and less than or equal to 0.5 pi;
wherein the resonant frequency is
Figure RE-GDA0002757783820000081
Cr is a resonance capacitor, and Lr is an auxiliary inductor.
The invention also provides a frequency conversion phase shift modulation method of the double-active-bridge series resonant converter circuit, which comprises the following steps:
step 1: direct power control unit collects output voltage V of converter2And according to the collected output voltage and the expected voltage VrefObtaining per unit transmission power instruction p;
step 2: the piecewise linearization frequency conversion phase shift modulation unit obtains the combination of a switching frequency ratio Fn and a phase shift angle theta according to a per unit transmission power instruction p and a converter voltage gain M by a piecewise linearization method;
and step 3: the pulse width generating unit controls the on and off of switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit according to the combination of the switching frequency ratio Fn and the phase shift angle theta;
specifically, in step 2, according to the per unit transmission power command and the voltage gain of the converter, the combination of the switching frequency ratio Fn and the phase shift angle θ is obtained by a piecewise linearization method, and the specific process includes:
(1) calculating the transmission power of the converter according to the transformer transformation ratio, the input voltage at the direct current side of the primary side H bridge circuit, the output voltage at the direct current side of the secondary side H bridge circuit, the switching frequency ratio Fn and the voltage gain M, and obtaining the per-unit transmission power of the converter according to the reference transmission power of the converter;
the per-unit transmission power of the converter is:
Figure RE-GDA0002757783820000091
wherein the reference power of the converter is
Figure RE-GDA0002757783820000092
V1Cr is a resonance capacitor, and Lr is an auxiliary inductor.
(2) According to the maximum allowable switching frequency ratio Fnmax1.6, minimum allowed switching frequency ratio Fnmin1.1, respectively obtaining an optimal control track of the effective value of the current and an optimal control track of the stress of the switching current according to the principles of minimizing the effective value of the resonant current and minimizing the stress of the current, and finally obtaining a fixed phase shift angle A at a frequency conversion boundary;
obtaining a control track with minimized current effective value and a control track with minimized switch current stress, and the specific steps are as follows:
1) obtaining an effective value of the current of the resonant tank of the converter according to the transformer transformation ratio, the input voltage at the direct current side of the primary side H-bridge circuit, the output voltage at the direct current side of the secondary side H-bridge circuit, the switching frequency ratio Fn and the voltage gain M, and obtaining a per-unit effective value of the current of the resonant tank by using the reference current;
the effective value of the per-unit resonance tank current of the converter is as follows:
Figure RE-GDA0002757783820000093
in the formula:
Figure RE-GDA0002757783820000094
wherein the reference current is
Figure RE-GDA0002757783820000095
V1Cr is a resonance capacitor and Lr is an auxiliary inductor.
2) Obtaining current stress of the converter according to the transformer transformation ratio, the input voltage at the direct current side of the primary side H-bridge circuit, the output voltage at the direct current side of the secondary side H-bridge circuit, the switching frequency ratio Fn and the voltage gain M, and obtaining per-unit current stress by using reference current;
the per unit current stress of the converter is:
Figure RE-GDA0002757783820000101
wherein the reference current is
Figure RE-GDA0002757783820000102
V1Cr is a resonance capacitor and Lr is an auxiliary inductor.
3) Under the condition that the per-unit transmission power instruction is determined, the effective value of the resonant tank current is optimized and solved according to the constraint condition, and an optimized control track of combination of Fn and theta for minimizing the effective value of the per-unit current is obtained;
taking the voltage gain M equal to 0.75 as an example, the optimization objective function is formula (5), and the modal boundary constraint conditions are:
Figure RE-GDA0002757783820000103
4) under the condition of a per-unit transmission power instruction, optimally solving the current stress of the resonance tank according to a constraint condition to obtain a combined control track of Fn and theta for minimizing the per-unit current stress;
taking the example that the voltage gain M is 0.75, the optimization objective function is formula (6), and the modal boundary constraint conditions are:
Figure RE-GDA0002757783820000104
as shown in fig. 3(a), the curves of the trajectories of the current effective value minimization and the current stress minimization and the control combinations Fn and θ are obtained, and it can be seen that, under different given per unit transmission power commands, the trajectories of the current effective value optimization and the current stress optimization are close to each other, so that the optimization control effect is equivalent.
5) A piecewise function is adopted, the current effective value minimization and the current stress minimization control trajectory are fitted in a linear mode to be the only piecewise optimization control trajectory, and as shown in a figure 3(b), a phase shift angle theta and a switch resonance frequency ratio Fn control combination curve are obtained; as can be seen from fig. 3, if the per unit transmission power command p is smaller than the threshold Po1, the switching frequency ratio is fixed to Fn equal to 1.6, and the phase shift angle is determined according to equation (10); when the per-unit transmission power command is: selecting a frequency conversion modulation mode when Po1< P < Po2, keeping a phase shift angle as a turning point phase shift angle A, and determining a switching frequency ratio Fn according to a formula (10); when P > Po1, the switching frequency ratio Fn is 1.1, and the phase shift angle is determined according to equation (10).
Similarly, the optimized control traces under different voltage gains M can be analyzed, FIG. 4 is the relationship curve between different voltage gains M and phase shift angles A, A1 and A2 given by the invention,
a1 is the turning point phase shift angle of the linear fitting control track when Fn is 1.6, A2 is the turning point phase shift angle when Fn is 1.1, wherein A is (A)1+A2)/2。
The boundary value of the transmission power can be determined according to the equations (9) and (1), fig. 5 is a relationship curve of Po1 and Po2 under different voltage gains M, and with reference to fig. 5, Po1 and Po2 under different voltage gains M can be obtained, and the corresponding calculation process can be easily deduced by those skilled in the art according to the technical solution.
Figure RE-GDA0002784056280000111
Figure RE-GDA0002784056280000112
And (3) combining the formula (10) and the piecewise optimization control track shown in the figure 3(b) to realize the frequency conversion phase shift modulation of the DB-SRC.
Fig. 6 shows the ZVS range of the present invention under the condition that Fn is greater than or equal to 1.6, and under the condition of different voltage gains M, the corresponding full ZVS operating region can be obtained for a given per unit transmission power p, and it can be seen that the ZVS range is significantly smaller when Fn is 1.1 than when Fn is 1.6. Meanwhile, in order to obtain higher power transmission efficiency, when the per-unit effective current value and current stress are analyzed and optimized, ZVS constraint can be preferentially considered when a full ZVS range is obtained.
Fig. 7 is a working waveform diagram of the present invention under light load, when the series resonant converter works in a light load or no-load state, the ratio of the switching resonant frequency is fixed to Fn 1.6, and phase shift control is adopted for DB-SRC, thereby realizing stable output of voltage under light load or no-load, and effectively solving the problem that the voltage gain of the series resonant converter cannot be flexibly adjusted. At the same time, ZVS is easily implemented to achieve higher efficiency.
Fig. 8 is a waveform diagram of the operation of the present invention under the transmission power command Po1< p < Po2, when the DB-SRC operates in the frequency modulation mode, the phase shift angle θ is fixed, and the lowest effective value of the resonant current and the current stress can be obtained, thereby improving the efficiency of the converter; while at the same time obtaining a wide range of voltage regulation capability.
It should be noted that all the data in the above embodiments are described as an example, the present invention is not limited to this, and the actual process may be set and calculated as needed.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A frequency conversion phase shift modulation device of a double-active-bridge series resonant converter circuit comprises a primary side H-bridge circuit, a resonant capacitor, an auxiliary inductor, a transformer, a secondary side H-bridge circuit, a primary side voltage stabilizing capacitor and a secondary side voltage stabilizing capacitor, and is characterized by comprising a direct power control unit, a segmented linearization frequency conversion phase shift modulation unit and a pulse width generation unit; the input end of the direct power control unit is connected with a primary side direct current bus and a secondary side direct current bus of a main circuit of the double-active-bridge series resonant converter, and the output end of the direct power control unit is connected with the piecewise linearization frequency conversion phase shift modulation unit; the output end of the piecewise linearization frequency conversion phase shift modulation unit is connected with the pulse width generation units of the primary side H-bridge circuit and the secondary side H-bridge circuit;
the direct power control unit is used for acquiring the actual output voltage of the converter and obtaining an instruction value of per unit transmission power according to the error between the acquired actual output voltage and the expected voltage;
the piecewise linearization frequency conversion phase shift modulation unit is used for determining the switching frequency and the phase shift angle according to the per unit linearization method and the per unit linearization transmission power instruction and the voltage gain, and sending the switching frequency and the phase shift angle to the pulse width generation unit; the pulse width generating unit is used for controlling the on-off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit, so that the effective value of the resonant current and the stress of the switching current are optimized, and the efficiency of the converter is further optimized;
the pulse width generating unit is used for generating two groups of square wave signals with adjustable frequency and 50% duty ratio and adjusting the phase difference between the two groups of square wave signals.
2. The frequency-converting phase-shifting modulation device according to claim 1, wherein the piecewise linearization method is to obtain the switching frequency and the phase shift angle according to the principle of minimizing the effective value of the resonant current and minimizing the stress of the current.
3. The frequency-converting phase-shifting modulation device according to claim 2, wherein the principle of minimizing the effective value of the resonant current and minimizing the current stress is to select a frequency-converting modulation mode or a phase-shifting modulation mode according to the value of the per-unit transmission power command, and further determine the switching frequency ratio and the phase-shifting angle; when the per unit transmission power instruction is smaller than a set demarcation value 1, a phase shift modulation mode is adopted, the frequency is set to be a maximum allowable switching frequency ratio in a fixed and unchangeable mode, and a phase shift angle is determined according to the transmission power instruction; when the per unit transmission power instruction is between the boundary value 1 and the boundary value 2, adopting variable frequency modulation, fixing the phase shift angle, and determining the switching frequency ratio according to the transmission power instruction; when the per unit transmission power instruction is larger than the demarcation value 2, phase shift modulation is adopted, the frequency is fixedly and invariably set as the minimum allowable switching frequency ratio, and the phase shift angle is determined according to the transmission power instruction.
4. The apparatus according to claim 1, wherein the primary side H-bridge circuit has a dc side connected to a primary side voltage source and an ac side connected to the primary side of the transformer via a resonant capacitor and an auxiliary inductor; the alternating current side of the secondary side H-bridge circuit is connected with the secondary side of the transformer, and the direct current side of the secondary side H-bridge circuit is connected with a secondary side load;
the primary side voltage-stabilizing capacitor and the secondary side voltage-stabilizing capacitor are respectively connected with the primary side H-bridge circuit and the secondary side H-bridge circuit in parallel.
5. The apparatus according to claim 1, wherein the primary H-bridge circuit comprises four switching devices, respectively: the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the corresponding anti-parallel diode and the voltage stabilizing capacitor on the primary side;
the secondary side H-bridge circuit comprises four switching devices which are respectively: the fifth switching tube, the sixth switching tube, the seventh switching tube, the eighth switching tube, the corresponding anti-parallel diode and the voltage stabilizing capacitor on the secondary side.
6. A frequency conversion phase shift modulation method based on the double-active-bridge series resonant converter circuit of any one of claims 1 to 5 is characterized by comprising the following steps:
step 1: the direct power control unit acquires the output voltage of the converter and obtains a per unit transmission power instruction according to the error between the acquired output voltage and the expected voltage;
step 2: the piecewise linearization frequency conversion phase shift modulation unit obtains a combination of a piecewise switching frequency ratio Fn and a phase shift angle theta according to the per unit transmission power instruction and the voltage gain of the converter by a piecewise linearization method;
and step 3: the pulse width generating unit controls the on and off of the switching tubes in the primary side H-bridge circuit and the secondary side H-bridge circuit according to the combination of the switching frequency ratio Fn and the phase shift angle theta.
7. The frequency conversion and phase shift modulation method according to claim 6, wherein the step 2 of obtaining the combination of the switching frequency ratio Fn and the phase shift angle θ by a piecewise linearization method according to the per-unit transmission power command and the voltage gain of the converter comprises:
(1) calculating the transmission power of the converter according to the transformer transformation ratio, the input voltage at the direct current side of the primary side H bridge circuit, the output voltage at the direct current side of the secondary side H bridge circuit, the switching frequency ratio Fn and the voltage gain, and calculating the per-unit transmission power of the converter according to the reference transmission power of the converter;
(2) according to the maximum permissible switching frequency ratio FnmaxMinimum allowable switching frequency ratio FnminDetermining the relation between a fixed phase shift angle A and a voltage gain M in a frequency conversion mode, wherein the expression is as follows:
Figure RE-FDA0002757783810000031
(3) determining boundary values Po1 and Po2 of transmission power according to equations (1) and (2), and when the per unit transmission power command is larger than Po2, adopting phase-shift modulation mode, and fixing the switching frequency ratio to the minimum allowable value Fnmin(ii) a When the per-unit transmission power command is smaller than Po1, the switching frequency ratio is fixed to the maximum allowable value Fnmax(ii) a Meanwhile, determining a phase shift angle according to the principle shown in the formula (3); when the transmission power is less than Po1 and greater than Po2, selecting a frequency conversion modulation mode, fixing the phase shift angle to A rad, and determining the switching frequency according to the formula (3);
Figure RE-FDA0002757783810000032
Figure RE-FDA0002757783810000033
where Fn is the switching frequency ratio and theta is the phase shift angle.
CN202010802117.7A 2020-08-11 2020-08-11 Frequency conversion phase shift modulation device and method for double-active-bridge series resonant converter circuit Pending CN112117908A (en)

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