CN115473441B - Optimized control strategy for isolated three-port soft switching converter - Google Patents

Optimized control strategy for isolated three-port soft switching converter Download PDF

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CN115473441B
CN115473441B CN202211372901.4A CN202211372901A CN115473441B CN 115473441 B CN115473441 B CN 115473441B CN 202211372901 A CN202211372901 A CN 202211372901A CN 115473441 B CN115473441 B CN 115473441B
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converter
phase shift
voltage
current
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CN115473441A (en
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刘晓悦
李月
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North China 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
    • H02M3/33569—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
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • 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
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • 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
    • H02M1/083—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the ignition at the zero crossing of the voltage or the current
    • 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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

The invention discloses an optimization control strategy for an isolated three-port soft switching converter, which comprises the following steps: (1) Deducing and obtaining expressions of full-bridge output current and soft switching conditions of each port of the isolated three-port converter, and calculating and realizing a phase shift angle value range of the soft switch of the switching tube according to the expressions; (2) Analyzing the application principle of the rectification average current optimization modulation method in the double-active bridge converter to obtain an expression of the rectification average value; (3) According to the symmetry of the three-port structure, the method for optimizing and modulating the rectified average current is popularized to an isolated three-port converter, and the critical value of a phase shift angle is found through the variation curve of the rectified average value and the power under different voltage ratios; (4) And determining the optimal phase shift angle through the phase shift angle value range and the phase shift angle critical value. By adopting the method, the invention utilizes the phase shift angle parameter determined by the phase shift combined with the rectification average current optimization modulation method, thereby not only realizing soft switching, but also reducing the conduction loss caused by current and further improving the efficiency of the converter.

Description

Optimized control strategy for isolated three-port soft switching converter
Technical Field
The invention relates to the technical field of DC/DC converters, in particular to an optimization control strategy for an isolated three-port soft switching converter.
Background
In recent years, the development and utilization of new energy resources have become a new trend, and power electronic conversion devices have received extensive attention and research as their core technologies.
The three-port DC/DC converter can be classified into a non-isolated type, a semi-isolated type and an isolated type according to an isolation method thereof. The non-isolated converter has the advantages of simple structure, high efficiency, easiness in expansion and the like, but also has the problem of low voltage gain, and voltage and current stress needs to be relieved by adopting a series input and parallel output mode. The semi-isolation structure effectively expands the voltage gain range due to the introduction of the isolation transformer, and meanwhile, the power device is multiplexed between the two ports, so that the integration level is higher, and the size of the converter is reduced. However, in applications requiring complete isolation, both non-isolated and semi-isolated topologies have significant disadvantages. Therefore, intensive research into a fully isolated three-port converter is particularly important.
At present, the converter is applied to new energy power generation and requires high conversion efficiency, and most researches are focused on realizing soft switching by using a resonant network, adding an auxiliary switching tube or utilizing a winding coupling inductor of a transformer, namely reducing switching loss. However, in the converter operating circuit operating at a lower frequency, the conduction loss is much larger than the switching loss. Therefore, it is necessary to develop an optimal control strategy for reducing converter losses to improve efficiency without adding components to change the converter topology.
Disclosure of Invention
The invention deduces and obtains the current of each port full-bridge converter and the expression of the soft switching condition based on phase shift control, analyzes and obtains the phase shift angle selection condition of the isolated three-port converter for realizing the soft switching condition, and selects the phase shift angle in the range to reduce the switching loss of the converter.
An optimization control strategy for an isolated three-port soft switching converter comprises the following steps:
(1) Deducing and obtaining an expression of the current of each port full-bridge converter of the isolated three-port converter and the soft switching condition, and calculating the value range of the phase shift angle of the soft switching tube soft switch according to the expression;
Figure DEST_PATH_IMAGE001
in the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE002
is the bridge arm midpoint voltage corresponding to port 1,
Figure DEST_PATH_IMAGE003
、
Figure DEST_PATH_IMAGE004
respectively converting the voltage to the midpoint voltage of the bridge arm corresponding to the port 1;
Figure DEST_PATH_IMAGE005
is the operating frequency of the converter;
Figure DEST_PATH_IMAGE006
representing the phase shift angle between port 1 and port 2,
Figure DEST_PATH_IMAGE007
represents the phase shift angle between port 1 and port 3;
Figure DEST_PATH_IMAGE008
、
Figure DEST_PATH_IMAGE009
and
Figure DEST_PATH_IMAGE010
are respectively port currents
Figure DEST_PATH_IMAGE011
、
Figure DEST_PATH_IMAGE012
And
Figure DEST_PATH_IMAGE013
the time corresponding to the waveform zero crossing point;
(2) Analyzing the application principle of the rectification average optimization modulation method in the double-active bridge converter to obtain the expression of the rectification average value
Figure DEST_PATH_IMAGE014
；
Figure DEST_PATH_IMAGE015
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE016
is the voltage on the primary side of the transformer,
Figure DEST_PATH_IMAGE017
is a voltage gain
Figure DEST_PATH_IMAGE018
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure DEST_PATH_IMAGE019
is the operating frequency of the converter and is,
Figure DEST_PATH_IMAGE020
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage source of the two side bridges
Figure DEST_PATH_IMAGE021
；
Figure DEST_PATH_IMAGE022
Is a port inductance;
(3) According to the symmetry of the three-port structure, the rectification average value is popularized to the isolation type three-port converter, and the critical value of a phase shift angle is found through the variation curve of the rectification average value and power under different voltage ratios;
Figure DEST_PATH_IMAGE023
in the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE024
is the bridge arm midpoint voltage corresponding to port 1,
Figure DEST_PATH_IMAGE025
is the inductance of the port, and is,
Figure DEST_PATH_IMAGE026
is the operating frequency of the converter;
Figure DEST_PATH_IMAGE027
is the ratio of the voltages at port 2,
Figure DEST_PATH_IMAGE028
being the ratio of the voltages at the port 3,
Figure DEST_PATH_IMAGE029
、
Figure DEST_PATH_IMAGE030
、
Figure DEST_PATH_IMAGE031
respectively the number of turns of the transformer winding,
Figure DEST_PATH_IMAGE032
is the input voltage of the port 1 and,
Figure DEST_PATH_IMAGE033
is the input voltage of the port 3 and,
Figure DEST_PATH_IMAGE034
is the output voltage of port 2, defining the voltage ratio
Figure DEST_PATH_IMAGE035
；
Figure DEST_PATH_IMAGE036
Representing the phase shift angle between port 1 and port 2,
Figure DEST_PATH_IMAGE037
represents the phase shift angle between port 1 and port 3; order to
Figure DEST_PATH_IMAGE038
；
(4) And determining the optimal phase shift angle through the value range of the phase shift angle and the critical value of the phase shift angle.
Further, the step (1) specifically comprises:
determining the topological structure of the converter, and analyzing the working principle of the converter;
drawing a switching mode diagram in one period of the converter according to the working principle waveform diagram and analyzing;
obtaining current expressions of three port windings in one period according to the periodicity and symmetry of the voltage and the current of the converter;
converting the requirements to be met by soft switching of each switching tube of the converter into time point constraint conditions;
Figure DEST_PATH_IMAGE039
in the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE040
、
Figure DEST_PATH_IMAGE041
and
Figure DEST_PATH_IMAGE042
are respectively port currents
Figure DEST_PATH_IMAGE043
、
Figure DEST_PATH_IMAGE044
And
Figure DEST_PATH_IMAGE045
the time corresponding to the waveform zero crossing point;
and determining the value range of the phase shift angle for realizing the soft switch of the switch tube according to the time constraint condition.
Further, the step (2) specifically comprises the following steps:
analyzing the working principle and the switching mode of the double-active bridge converter to obtain expressions of the inductive current in different time periods in one period;
calculating the current value at any moment according to the inductance current expression so as to obtain the average value of the inductance current and the input power under the traditional single phase-shifting control;
Figure DEST_PATH_IMAGE046
Figure DEST_PATH_IMAGE047
in the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE048
is the voltage on the primary side of the transformer,
Figure DEST_PATH_IMAGE049
is a voltage gain
Figure DEST_PATH_IMAGE050
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure DEST_PATH_IMAGE051
is the frequency of operation of the converter and,
Figure DEST_PATH_IMAGE052
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage source of the two side bridges
Figure DEST_PATH_IMAGE053
；
Figure DEST_PATH_IMAGE054
Is a port inductance;
voltage, current, power and
Figure DEST_PATH_IMAGE055
performing per unit on the reference value to obtain a per unit value expression of the current and the power under SPS modulation;
determining a constraint condition according to a voltage ratio and a condition that the double active bridges realize zero voltage under phase shift control;
Figure DEST_PATH_IMAGE056
defining a rectified mean value of an inductor current
Figure DEST_PATH_IMAGE057
From the current waveformThe area enclosed by the horizontal coordinate represents the rectification average value by the area, and finally the expression of the rectification average value is obtained;
Figure DEST_PATH_IMAGE058
in the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE059
the area enclosed by the current waveform and the abscissa is obtained;
Figure DEST_PATH_IMAGE060
are respectively as
Figure DEST_PATH_IMAGE061
The instantaneous value of the current at the moment,
Figure DEST_PATH_IMAGE062
corresponding to the starting time of the trigger pulse of the switching tube of the leading bridge arm on the primary side,
Figure DEST_PATH_IMAGE063
correspond to
Figure DEST_PATH_IMAGE064
The time value corresponding to the first zero-crossing point of the current waveform,
Figure DEST_PATH_IMAGE065
the secondary side is ahead of the rising edge time of the trigger pulse of the bridge arm switch tube,
Figure DEST_PATH_IMAGE066
the time of the falling edge of the trigger pulse of the leading bridge arm switching tube on the primary side is the half-cycle time.
The invention adopts the above optimization control strategy, and has the following advantages: 1) A soft switching condition of the three-port converter is determined. The phase shift angle is selected within the range of the phase shift angle capable of realizing the soft switching, so that the switching loss of a switching tube can be reduced, and the efficiency of the converter is improved; 2) The problem of inaccurate phase shift angle selection under the soft switching condition is solved, and the phase shift angle parameters determined by combining phase shift with a rectification average current optimization modulation method are utilized, so that the soft switching is realized, the conduction loss caused by current is reduced, and the efficiency of the converter is further improved.
Drawings
FIG. 1 is an overall process of the present invention;
FIG. 2 is a three-port converter topology;
FIG. 3 is a schematic diagram of the operation of a three-port converter;
FIG. 4 is a soft switching range under different conditions;
FIG. 5 is a dual active bridge converter topology;
FIG. 6 is a schematic diagram of the operation of a dual active bridge converter;
FIG. 7 is a dual active bridge converter power curve;
FIG. 8 illustrates soft switching ranges of a dual active bridge converter;
FIG. 9 is a graph showing the variation of current value versus transmission power for three-port converters with different voltage ratios;
FIG. 10 is a three-port converter simulation model;
FIG. 11 is a soft switching result verification;
fig. 12 shows port current comparison results before and after optimization.
Detailed Description
The technical scheme of the invention is further explained by combining the drawings and the embodiment.
As shown in fig. 1, an optimization control strategy for an isolated three-port soft switching converter first derives and obtains an expression of current and soft switching conditions of a full-bridge converter of each port, and then determines a value range of a phase shift angle or voltage of a switching tube to realize soft switching; secondly, analyzing the double-active-bridge converter, obtaining the relation between transmission power and voltage ratio through a rectification optimization average modulation method and finding a phase shift angle; and finally, according to the symmetry of the three-port structure, the conclusion of the double-active converter is pushed to the three-port converter, and finally, the optimal phase shift angle is determined in the value range of the phase shift angle. And finally, verifying the method by combining the simulation example.
1. And determining the value range of the phase shifting angle or the voltage.
The topology of the converter is determined as shown in fig. 2.
The operation principle of the transducer is analyzed as shown in fig. 3.
And drawing a switching mode diagram of the three-port converter in one period according to the working principle waveform diagram and analyzing. And (3) obtaining a current expression of each port winding in one period according to the periodicity and symmetry of the voltage and the current of the converter, namely the expressions (1), (2) and (3).
Figure DEST_PATH_IMAGE067
（1）
Figure DEST_PATH_IMAGE068
（2）
Figure DEST_PATH_IMAGE069
（3）
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE070
is the bridge arm midpoint voltage corresponding to port 1,
Figure DEST_PATH_IMAGE071
、
Figure DEST_PATH_IMAGE072
respectively converted to the bridge arm midpoint voltage corresponding to the port 1.
Figure DEST_PATH_IMAGE073
Is the inductance of each of the ports, and,
Figure DEST_PATH_IMAGE074
is the operating frequency of the converter.
Figure DEST_PATH_IMAGE075
Indicating between port 1 and port 2The phase shift angle is set to be in a phase shift angle,
Figure DEST_PATH_IMAGE076
representing the phase shift angle between port 1 and port 3.
And converting the condition to be met by each switching tube of the converter to realize zero voltage into a time constraint condition, which is shown in an equation (4).
Figure DEST_PATH_IMAGE077
（4）
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE078
is the bridge arm midpoint voltage corresponding to port 1,
Figure DEST_PATH_IMAGE079
、
Figure DEST_PATH_IMAGE080
respectively converted to the bridge arm midpoint voltage corresponding to the port 1.
Figure DEST_PATH_IMAGE081
Is the operating frequency of the converter.
Figure DEST_PATH_IMAGE082
Representing the phase shift angle between port 1 and port 2,
Figure DEST_PATH_IMAGE083
representing the phase shift angle between port 1 and port 3.
Figure DEST_PATH_IMAGE084
、
Figure DEST_PATH_IMAGE085
And
Figure DEST_PATH_IMAGE086
are respectively port currents
Figure DEST_PATH_IMAGE087
、
Figure DEST_PATH_IMAGE088
And
Figure DEST_PATH_IMAGE089
the time corresponding to the waveform zero crossing point.
Defining a voltage ratio
Figure DEST_PATH_IMAGE090
From the above expressions, it is known that the condition for realizing soft switching is related to the voltage ratio between the ports and the inter-bridge phase shift angle. If fixed
Figure DEST_PATH_IMAGE091
And phase shift angle between port 1 and port 3
Figure DEST_PATH_IMAGE092
It can be obtained that when the three port switch tubes all satisfy zero voltage
Figure DEST_PATH_IMAGE093
And phase shift angle between Port 1 and Port 2
Figure DEST_PATH_IMAGE094
The relationship of the feet.
As shown in fig. 4, when the voltage of a certain port increases, the soft switching range of the switching tube of the port increases, and the soft switching ranges of the other two ports decrease; when the voltage ratio of each port is 1, all the switching tubes can realize soft switching in the maximum range; for each port, when the voltage and the phase shift angle of a certain port are fixed, the range of the port switch tube for realizing soft switching is in direct proportion to the absolute value of the phase shift angle.
When the voltage values are different, the corresponding phase shift angle ranges of all the switch tube soft switches can be different. Get and decide
Figure DEST_PATH_IMAGE095
Can calculate out
Figure DEST_PATH_IMAGE096
The value boundary of (1) is determined in the same way
Figure DEST_PATH_IMAGE097
Can calculate
Figure DEST_PATH_IMAGE098
The value boundary of (a).
The value range of the phase shift angle or the voltage of the soft switch of the switching tube is determined according to the soft switch condition, and the value of a definite parameter cannot be determined. Therefore, the scheme further selects a rectification average current optimization modulation method for optimization.
2. Dual active bridge converter analysis.
According to the symmetry of the three-port structure, the application principle of the rectification optimization average modulation method in the double-active bridge converter is analyzed, and then the conclusion is popularized to the three-port converter.
By analyzing the working principle and the switching mode of the double-active-bridge converter with reference to fig. 5 and 6, expression (5) of the inductive current in different time periods in one cycle can be obtained.
Since the inductor current varies periodically
Figure DEST_PATH_IMAGE099
The current value at each time may be found from a current expression, where the expression for each time period is:
Figure DEST_PATH_IMAGE100
. Further, the average value of the inductive current is obtained
Figure DEST_PATH_IMAGE101
Input power under traditional single phase shift control
Figure DEST_PATH_IMAGE102
。
Figure DEST_PATH_IMAGE103
（5）
Figure DEST_PATH_IMAGE104
（6）
Figure DEST_PATH_IMAGE105
（7）
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE106
is the voltage on the primary side of the transformer,
Figure DEST_PATH_IMAGE107
in order to be an inductor, the inductor,
Figure DEST_PATH_IMAGE108
is a voltage gain
Figure DEST_PATH_IMAGE109
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure DEST_PATH_IMAGE110
is the operating frequency of the converter and is,
Figure DEST_PATH_IMAGE111
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage source of the two side bridges
Figure DEST_PATH_IMAGE112
；
Figure DEST_PATH_IMAGE113
Is a port inductance;
current and power are converted into
Figure DEST_PATH_IMAGE114
A per unit value expression of current and power under SPS modulation can be obtained by performing per unit on the reference value, see table 1.
TABLE 1 Current and Power per Unit value expression
Figure DEST_PATH_IMAGE115
Plotting SPS modulation phase Down Angle according to expression
Figure DEST_PATH_IMAGE116
The variation curve of the per unit transmission power is shown in fig. 7. When the phase shift angle is fixed, the ratio of the transmitted power to the voltagekIs in direct proportion; current to voltage ratiokAt a timing and phase shift angle of
Figure DEST_PATH_IMAGE117
The transmission power is maximized.
According to the condition that the double active bridges realize zero voltage under the phase shift control, according tokDifferent values of (a) may result in different constraints.
Figure DEST_PATH_IMAGE118
（8）
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE119
is a voltage gain
Figure DEST_PATH_IMAGE120
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure DEST_PATH_IMAGE121
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage sources of the two side bridges
Figure DEST_PATH_IMAGE122
。
The soft switching range can be obtained according to equation (8), as shown in fig. 8. The SPS control does not enable soft switching over the full range, its ratio to voltagekIt is relevant.kThe soft switching range is maximal when =1k>1 when followingkThe soft switching range is smaller and smaller, and the transmission power of the system is more influencedAnd (4) limiting.
In the power loss of the switching tubes of the bridge arms of the double-active bridge working at a lower switching frequency, the conduction loss is larger than the switching loss. Since the conduction voltage drop of the switching tube is a fixed value, the loss caused by the current is a main part of the overall loss of the converter. Therefore, it is necessary to select the phase shift angle corresponding to the minimum current for transmitting the same power.
Defining the average value of the rectification of the inductor current as
Figure DEST_PATH_IMAGE123
Then, there are:
Figure DEST_PATH_IMAGE124
（9）
the areas enclosed by the current waveform and the abscissa can be obtained according to the current waveform
Figure DEST_PATH_IMAGE125
The expression for the rectified mean value in area is:
Figure DEST_PATH_IMAGE126
（10）
in which as shown in the shaded portion of figure 6,
Figure 878217DEST_PATH_IMAGE125
the expression is as follows:
Figure DEST_PATH_IMAGE127
（11）
from equation (5):
Figure DEST_PATH_IMAGE128
（12）
Figure DEST_PATH_IMAGE129
（13）
Figure DEST_PATH_IMAGE130
（14）
according to the current waveform in fig. 6, it can be seen that:
Figure DEST_PATH_IMAGE131
the simultaneous formulas (10), (11), (12), (13) and (14) are reduced to obtain an expression (15) of the rectified average value.
Figure DEST_PATH_IMAGE132
（15）
Analyzing the curves of the average value of the transmitted power and the current of the converter shown in the graph (a) in fig. 9 shows that: the maximum power which can be transmitted by the converter is different in different voltage ratios; under the condition of the same voltage ratio, before the maximum transmission power point is reached, a large current average value and a small current average value exist in certain transmission power; there is a certain voltage ratio where the converters deliver the same power so that the average value of the current in the circuit is minimal. Therefore, the converter should select the parameter corresponding to the minimum average value of the current to reduce the conduction loss, thereby improving the working efficiency of the converter.
3. Three-port transducer analysis.
And (4) pushing a rectification average value expression under the two ports to the three-port converter network. It is clear that the rectified mean value in a three-port converter network is a function of voltage and phase shift angle, and thus it follows that both soft switching conditions and rectified mean values are a function of voltage and phase shift angle in a three-port configuration. As can be seen in connection with figure 3,
Figure DEST_PATH_IMAGE133
。
the expression for the rectified mean in a three-port network is:
Figure DEST_PATH_IMAGE134
（16）
according to FIG. 3The current waveform can obtain the area of the shaded part
Figure DEST_PATH_IMAGE135
The expression is as follows:
Figure DEST_PATH_IMAGE136
（17）
the simultaneous formulas (1), (2), (3), (4), (16) and (17) can be simplified and arranged to obtain
Figure DEST_PATH_IMAGE137
Figure DEST_PATH_IMAGE138
（18）
In the formula (I), the compound is shown in the specification,
Figure DEST_PATH_IMAGE139
is the bridge arm midpoint voltage corresponding to port 1,
Figure DEST_PATH_IMAGE140
is the inductance of each port, and the inductance of each port,
Figure DEST_PATH_IMAGE141
is the operating frequency of the converter.
Figure DEST_PATH_IMAGE142
Is the ratio of the voltages at port 2,
Figure DEST_PATH_IMAGE143
for the voltage ratio of port 3, the voltage ratio is defined
Figure DEST_PATH_IMAGE144
；
Figure DEST_PATH_IMAGE145
Representing the phase shift angle between port 1 and port 2,
Figure DEST_PATH_IMAGE146
indicates the phase shift angle between port 1 and port 3, such that
Figure DEST_PATH_IMAGE147
。
It is clear that the rectified mean value is a function of the voltage and the phase shift angle, i.e.
Figure DEST_PATH_IMAGE148
. It follows that in a three-port configuration, both soft switching conditions and rectified mean values are functions of voltage and phase shift angle.
Get
Figure DEST_PATH_IMAGE149
Constant value, changing the voltage of port 3, the average current of load end and
Figure DEST_PATH_IMAGE150
the relationship (c) is shown in FIG. 9 (b). It can be seen that the voltage at the second port is fixed and takes a fixed phase shift angle
Figure DEST_PATH_IMAGE151
In the case of (2), there is only a suitable voltage ratio
Figure DEST_PATH_IMAGE152
So as to correspond to the phase shift angle
Figure DEST_PATH_IMAGE153
The lower current average is minimal. Let two be different
Figure DEST_PATH_IMAGE154
The average values of the currents are equal, and the phase shift angle can be obtained
Figure DEST_PATH_IMAGE155
Is measured. The more proper phase shift angle can be determined by combining with the phase shift angle boundary under the soft switching condition, the phase shift angle not only can realize zero voltage of all switching tubes, but also can minimize the average current value, thereby reducing conduction loss and switching lossThe working efficiency of the converter is improved by one step.
Through the analysis of the characteristics of the soft switch of the three-port converter, the voltage selection of the port 3 is different, and the corresponding phase shift angle range of the soft switch can be different. Suppose that
Figure DEST_PATH_IMAGE156
Ratio of sum to voltage
Figure DEST_PATH_IMAGE157
Is a fixed value, then
Figure DEST_PATH_IMAGE158
The soft switching of all switching tubes can be realized within a certain value range. By analyzing the method for optimizing and modulating the average current of the rectifying current, the hypothesis can be known
Figure DEST_PATH_IMAGE159
At the same phase shift angle as a fixed value
Figure DEST_PATH_IMAGE160
Under, there is a certain
Figure DEST_PATH_IMAGE161
So that the rectified average current is minimized.
4. Simulation example
The application effect of the present invention is explained below with reference to the simulation example.
A simulation model of the three-port converter is built, phase shift is controlled by combining with a rectification average optimization strategy, soft switch implementation conditions and current magnitude conditions of the converter before and after optimization are compared, and simulation parameters are shown in table 2.
TABLE 2 simulation parameters
Figure DEST_PATH_IMAGE162
A simulation model of the three-port converter was constructed in simulink based on the above parameters, as shown in FIG. 10. The simulation time was set to 0.04s. It can be seen from the simulation result of voltage and current in fig. 11 that the zero crossing point of current lags behind the zero crossing point of voltage, so that soft switching of all switching tubes is realized, and switching loss is reduced. According to the comparison of the current before and after optimization with the current in fig. 12, the zero crossing point of the current after optimization is delayed a little more than that before optimization, and the realization of soft switching is ensured more. In addition, the average value of the current after optimization is smaller than that before optimization, and the conduction loss is reduced.
The above is a specific embodiment of the present invention, but the scope of the present invention should not be limited thereto. Any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention, and therefore, the protection scope of the present invention is subject to the protection scope defined by the appended claims.

Claims (3)

1. An optimization control strategy for an isolated three-port soft switching converter is characterized by comprising the following steps:
(1) Deducing and obtaining an expression of the current of each port full-bridge converter of the isolated three-port converter and the soft switching condition, and calculating the value range of the phase shift angle of the soft switching tube soft switch according to the expression;
Figure 394909DEST_PATH_IMAGE001
in the formula (I), the compound is shown in the specification,
Figure 174646DEST_PATH_IMAGE002
is the bridge arm midpoint voltage corresponding to port 1,
Figure 38697DEST_PATH_IMAGE003
、
Figure 56331DEST_PATH_IMAGE004
respectively converting to bridge arm midpoint voltage corresponding to the port 1;
Figure 347635DEST_PATH_IMAGE005
is the operating frequency of the converter;
Figure 817931DEST_PATH_IMAGE006
representing the phase shift angle between port 1 and port 2,
Figure 751252DEST_PATH_IMAGE007
represents the phase shift angle between port 1 and port 3;
Figure 888972DEST_PATH_IMAGE008
、
Figure 616757DEST_PATH_IMAGE009
and
Figure 105507DEST_PATH_IMAGE010
are respectively port currents
Figure 311360DEST_PATH_IMAGE011
、
Figure 569166DEST_PATH_IMAGE012
And
Figure 467852DEST_PATH_IMAGE013
the time corresponding to the waveform zero crossing point;
(2) Analyzing the application principle of the rectification average optimization modulation method in the double-active bridge converter to obtain the expression of the rectification average value
Figure 178319DEST_PATH_IMAGE014
；
Figure 187863DEST_PATH_IMAGE015
In the formula (I), the compound is shown in the specification,
Figure 565755DEST_PATH_IMAGE016
is the voltage on the primary side of the transformer,
Figure 104184DEST_PATH_IMAGE017
is a voltage gain
Figure 301947DEST_PATH_IMAGE018
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure 115182DEST_PATH_IMAGE019
is the operating frequency of the converter and is,
Figure 347580DEST_PATH_IMAGE020
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage source of the two side bridges
Figure 322490DEST_PATH_IMAGE021
；
Figure 273128DEST_PATH_IMAGE022
Is a port inductance;
(3) According to the symmetry of the three-port structure, the average rectification value is popularized to an isolated three-port converter, and the critical value of a phase shift angle is found through the average rectification value and the change curve of power under different voltage ratios;
Figure 890054DEST_PATH_IMAGE023
in the formula (I), the compound is shown in the specification,
Figure 976959DEST_PATH_IMAGE024
is the bridge arm midpoint voltage corresponding to port 1,
Figure 122769DEST_PATH_IMAGE025
is the inductance of the port, and is,
Figure 29546DEST_PATH_IMAGE026
is the operating frequency of the converter;
Figure 184583DEST_PATH_IMAGE027
being the ratio of the voltages at port 2,
Figure 125995DEST_PATH_IMAGE028
being the ratio of the voltages at the port 3,
Figure 442706DEST_PATH_IMAGE029
、
Figure 102358DEST_PATH_IMAGE030
、
Figure 529928DEST_PATH_IMAGE031
respectively the number of turns of the transformer winding,
Figure 325846DEST_PATH_IMAGE032
is the input voltage of the port 1 and,
Figure 79038DEST_PATH_IMAGE033
is the input voltage of the port 3 and,
Figure 225986DEST_PATH_IMAGE034
is the output voltage of port 2, defining the voltage ratio
Figure 457247DEST_PATH_IMAGE035
；
Figure 107671DEST_PATH_IMAGE036
Representing the phase shift angle between port 1 and port 2,
Figure 297344DEST_PATH_IMAGE037
represents the phase shift angle between port 1 and port 3; order to
Figure 400429DEST_PATH_IMAGE038
；
(4) And determining the optimal phase shift angle through the value range of the phase shift angle and the critical value of the phase shift angle.
2. The optimal control strategy for the isolated three-port soft-switching converter according to claim 1, wherein the step (1) specifically comprises:
determining the topological structure of the converter, and analyzing the working principle of the converter;
drawing a switching mode diagram in one period of the converter according to the working principle waveform diagram and analyzing;
obtaining current expressions of three port windings in one period according to the periodicity and symmetry of the voltage and the current of the converter;
converting the requirements to be met by soft switching of each switching tube of the converter into time point constraint conditions;
Figure 700961DEST_PATH_IMAGE039
in the formula (I), the compound is shown in the specification,
Figure 205891DEST_PATH_IMAGE040
、
Figure 566465DEST_PATH_IMAGE041
and
Figure 688005DEST_PATH_IMAGE042
are respectively port currents
Figure 272788DEST_PATH_IMAGE043
、
Figure 897804DEST_PATH_IMAGE044
And
Figure 429280DEST_PATH_IMAGE045
the time corresponding to the waveform zero crossing point;
and determining the value range of the phase shift angle for realizing the soft switch of the switch tube according to the time constraint condition.
3. The optimal control strategy for the isolated three-port soft switching converter according to claim 1, wherein the step (2) specifically comprises:
analyzing the working principle and the switching mode of the double-active bridge converter to obtain expressions of the inductive current in different time periods in one period;
calculating the current value at any moment according to the inductance current expression so as to obtain the average value of the inductance current and the input power under the traditional single phase-shifting control;
Figure 506957DEST_PATH_IMAGE046
in the formula (I), the compound is shown in the specification,
Figure 149291DEST_PATH_IMAGE047
is the voltage on the primary side of the transformer,
Figure 894393DEST_PATH_IMAGE048
is a voltage gain
Figure 331191DEST_PATH_IMAGE049
，NIs the turn ratio of the primary winding and the secondary winding of the transformer,
Figure 161743DEST_PATH_IMAGE050
is the operating frequency of the converter and is,
Figure 76610DEST_PATH_IMAGE051
is the phase difference of the midpoint position of the positive level or the negative level of the square wave voltage sources of the two side bridges
Figure 676218DEST_PATH_IMAGE052
；
Figure 549497DEST_PATH_IMAGE053
Is a port inductance;
voltage, current, power and
Figure 867345DEST_PATH_IMAGE054
performing per unit on the reference value to obtain a per unit value expression of the current and the power under SPS modulation;
determining a constraint condition according to a voltage ratio and a condition that the double active bridges realize zero voltage under phase shift control;
Figure 54744DEST_PATH_IMAGE055
defining a rectified mean value of an inductor current
Figure 243280DEST_PATH_IMAGE056
Calculating the area enclosed by the current waveform and the abscissa according to the current waveform, and expressing the average rectification value by the area to finally obtain an expression of the average rectification value;
Figure 756301DEST_PATH_IMAGE057
in the formula (I), the compound is shown in the specification,
Figure 561446DEST_PATH_IMAGE058
the area enclosed by the current waveform and the abscissa is obtained;
Figure 349273DEST_PATH_IMAGE059
are respectively as
Figure 392316DEST_PATH_IMAGE060
The instantaneous value of the current at the moment,
Figure 607396DEST_PATH_IMAGE061
corresponding to the starting time of the trigger pulse of the switching tube of the leading bridge arm of the primary side,
Figure 368679DEST_PATH_IMAGE062
correspond to
Figure 694618DEST_PATH_IMAGE063
The time value corresponding to the first zero-crossing point of the current waveform,
Figure 123326DEST_PATH_IMAGE064
the secondary side is ahead of the rising edge time of the trigger pulse of the bridge arm switch tube,
Figure 243728DEST_PATH_IMAGE065
the time of the falling edge of the trigger pulse of the leading bridge arm switching tube on the primary side is the half-cycle time.
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