CN117134625A - Current modulation method, device and storage medium for mixed three-level DAB - Google Patents

Current modulation method, device and storage medium for mixed three-level DAB Download PDF

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Publication number
CN117134625A
CN117134625A CN202311072521.3A CN202311072521A CN117134625A CN 117134625 A CN117134625 A CN 117134625A CN 202311072521 A CN202311072521 A CN 202311072521A CN 117134625 A CN117134625 A CN 117134625A
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China
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mode
bridge
full
current
hybrid
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Chinese (zh)
Inventor
方世琦
刘恕宇
戴鹏
黄云辰
杨梓薇
武涵
尹志
郭庆
郭灿
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China University of Mining and Technology CUMT
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China University of Mining and Technology CUMT
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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
    • H02M1/0048—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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/4835—Converters with outputs that each can have more than two voltages levels comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • 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)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a current modulation method, device and storage medium of mixed three-level DAB, and relates to the technical field of converter control. The method comprises the following steps: dividing the current mode of the mixed three-level DAB, and determining the inductive current and the transmission power under the current mode; the current mode includes a full-bridge mode and a full-bridge half-bridge mode; calculating effective values of the inductance current in each mode, and carrying out numerical discrete optimization on the effective values in the corresponding transmission power range to obtain an off-line optimal control table of the two modes; comparing the optimized data in each off-line optimal control table, and determining a mode switching boundary; and carrying out current modulation on the mixed three-level DAB by utilizing the mode switching boundary and the optimized control table. The asymmetric duty ratio modulation method is applied to the converter, the converter can be controlled based on the mode switching boundary and the off-line optimal control table, the control degree of freedom of the converter is increased, and the overall operation efficiency is improved.

Description

Current modulation method, device and storage medium for mixed three-level DAB
Technical Field
The invention relates to the technical field of converter control, in particular to a current modulation method, device and storage medium of hybrid three-level DAB.
Background
The most traditional control strategy of the hybrid three-level double-active-bridge converter (DAB) with the blocking capacitor is single phase shift control (Single Phase Shift, SPS) which changes the direction and the size of transmission power by controlling the inter-bridge phase shift angle of the primary side and the secondary side, but only has one control degree of freedom, the single phase shift control is used for the diode clamping hybrid three-level double-active-bridge converter with the blocking capacitor, the SPS control is difficult to realize zero voltage opening in the full range under light load, and the zero voltage opening in the full power range can be realized under k=v1/nv2=1. When the voltages at two sides of the converter are not matched, namely k is not equal to 1, zero-voltage turn-on characteristics are lost in light load, and the defects of high current stress, low converter efficiency and the like exist. At this time, a plurality of control degrees of freedom are needed, and because of the coupling relation between different control degrees of freedom, the more the control quantity is, the more complicated the control is, and the more difficult the optimization of the effective value of the current is by the traditional mathematical method.
Disclosure of Invention
The invention aims to provide a current modulation method, device and storage medium of mixed three-level DAB, which can control a converter based on a mode switching boundary and an off-line optimal control table, increase the control freedom of the converter and improve the overall operation efficiency.
In order to achieve the above object, the present invention provides the following solutions:
a current modulation method, apparatus and storage medium for hybrid three-level DAB, comprising:
dividing the current mode of the mixed three-level DAB, and determining the inductive current and the transmission power under the current mode; the current mode comprises a full-bridge mode and a full-bridge half-bridge mode;
calculating the effective value of the inductance current in each mode, and carrying out numerical discrete optimization on the effective value in the corresponding transmission power range to obtain an off-line optimal control table of the two modes;
comparing the optimized data in each off-line optimal control table, and determining a mode switching boundary;
and carrying out current modulation on the mixed three-level DAB by utilizing the mode switching boundary and the optimized control table.
Optionally, the dividing the current mode of the mixed three-level DAB to determine the inductive current and the transmission power in the current mode specifically includes:
dividing a full-bridge mode and a corresponding working mode and a full-bridge half-bridge mode and a corresponding working mode according to the magnitude relation of the duty ratio of a primary side switching tube and the phase shift angle between bridges of the hybrid three-level DAB; the working modes of the full-bridge mode comprise a full-bridge mode first mode, a full-bridge mode second mode, a full-bridge mode third mode and a full-bridge mode fourth mode; the working modes of the full-bridge half-bridge mode comprise a full-bridge half-bridge mode first mode, a full-bridge half-bridge mode second mode, a full-bridge half-bridge mode third mode and a full-bridge half-bridge mode fourth mode;
based on the divided modes and corresponding working modes of the hybrid three-level DAB, respectively solving the inductive current and the transmission power in the full-bridge mode and the full-bridge half-bridge mode according to an equivalent circuit model and typical waveforms.
Optionally, the equivalent circuit model is composed of a primary full bridge, a secondary full bridge, a leakage inductance equivalent inductance, a high-frequency isolation transformer, a blocking capacitor and 3 bypass capacitors; the primary full bridge consists of 8 switching tubes and 4 diodes; the secondary full bridge consists of 4 switching tubes.
Optionally, calculating an effective value of the inductor current in each mode, and performing numerical discrete optimization on the effective value in a corresponding transmission power range to obtain an offline optimal control table of two modes, wherein the offline optimal control table specifically comprises:
calculating the effective value of the inductance current in each mode, performing discrete numerical optimization on the effective value of the inductance current in a full power range by taking the effective value of the inductance current as an optimization target and taking transmission power and a soft switch as limiting conditions, and establishing an offline optimal control table of the two modes.
Optionally, the determining a mode switching boundary by comparing the optimization data in each offline optimal control table specifically includes:
drawing k and P by using optimized data in each off-line optimal control table * 、i * rms A three-dimensional map; wherein k represents the ratio of input voltage to output voltage; p (P) * Representing transmission power; i.e * rms Representing the effective value of the inductor current;
k, P of two modes * 、i * rms And overlapping the three-dimensional images, and demarcating a mode switching boundary on an intersection line of two images in a top view of the overlapped three-dimensional images by using a fuzzy piecewise linear method.
Optionally, using the mode switching boundary and the optimization control table, performing current modulation on the mixed three-level DAB, specifically including:
and using the mode switching boundary and the optimization control table to enable the mixed three-level DAB to generate corresponding direct-current bias voltage under the working mode of the corresponding mode so as to meet different input-output voltage ratios and finish current modulation.
The invention also provides an electronic device comprising a memory for storing a computer program and a processor which runs the computer program to cause the electronic device to execute the current modulation method of hybrid three-level DAB according to the above.
The present invention also provides a computer readable storage medium storing a computer program which when executed by a processor implements the current modulation method of hybrid three-level DAB as described above.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention discloses a current modulation method, equipment and a storage medium of mixed three-level DAB, wherein the method comprises the steps of dividing current modes of the mixed three-level DAB and determining inductive current and transmission power under the current modes; the current mode includes a full-bridge mode and a full-bridge half-bridge mode; calculating effective values of the inductance current in each mode, and carrying out numerical discrete optimization on the effective values in a corresponding transmission power range to obtain an off-line optimal control table of the two modes; comparing the optimized data in each off-line optimal control table, and determining a mode switching boundary; and carrying out current modulation on the mixed three-level DAB by utilizing the mode switching boundary and the optimized control table. The invention applies the asymmetric duty ratio modulation method to the converter, controls the converter based on the modal switching boundary, and can enable the converter to generate corresponding direct-current bias voltage under the corresponding working mode so as to adapt to different input-output voltage ratios, thereby greatly reducing the switching loss of the converter; meanwhile, the converter is controlled based on the off-line optimal control table, so that the control degree of freedom of the converter is increased, the effective value of the current of the converter is reduced, the on-state loss is reduced, and the overall operation efficiency is improved on the premise of ensuring safe operation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a current modulation method of the hybrid three-level DAB of the present invention;
fig. 2 is a hybrid three-level DAB topology based on dc blocking capacitors in the present embodiment;
FIG. 3 is a diagram of an inductor current effective value control framework based on the structure of FIG. 2 in the present embodiment;
FIG. 4 is a schematic diagram of the working waveforms of each mode in the present embodiment; wherein (a) is a waveform diagram of a first mode of a full-bridge mode, (b) is a waveform diagram of a second mode of the full-bridge mode, (c) is a waveform diagram of a third mode of the full-bridge mode, (d) is a waveform diagram of a fourth mode of the full-bridge mode, (e) is a waveform diagram of the first mode of the full-bridge half-bridge mode, (f) is a waveform diagram of the second mode of the full-bridge half-bridge mode, (g) is a waveform diagram of the third mode of the full-bridge half-bridge mode, and (h) is a waveform diagram of the fourth mode of the full-bridge half-bridge mode;
FIG. 5 shows the modes k and P in the present embodiment * 、i * rms A three-dimensional map; wherein part (a) is a three-dimensional view of a full-bridge half-bridge modality; part (b) is a three-dimensional view of a full-bridge mode;
FIG. 6 is a diagram of overlapping k and P in the present embodiment * 、i * rms Three-dimensional and top views; wherein part (a) is a three-dimensional view and part (b) is a top view;
fig. 7 is a schematic diagram of a control flow of the controller in the present embodiment.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a current modulation method, device and storage medium of mixed three-level DAB, which can control a converter based on a mode switching boundary and an off-line optimal control table, increase the control freedom of the converter and improve the overall operation efficiency.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in fig. 1, the present invention provides a current modulation method of hybrid three-level DAB, comprising:
step 100: dividing the current mode of the mixed three-level DAB, and determining the inductive current and the transmission power under the current mode; the current mode comprises a full-bridge mode and a full-bridge half-bridge mode; the method specifically comprises the following steps:
dividing a full-bridge mode and a corresponding working mode and a full-bridge half-bridge mode and a corresponding working mode according to the magnitude relation of the duty ratio of a primary side switching tube and the phase shift angle between bridges of the hybrid three-level DAB; the working modes of the full-bridge mode comprise a full-bridge mode first mode, a full-bridge mode second mode, a full-bridge mode third mode and a full-bridge mode fourth mode; the working modes of the full-bridge half-bridge mode comprise a full-bridge half-bridge mode first mode, a full-bridge half-bridge mode second mode, a full-bridge half-bridge mode third mode and a full-bridge half-bridge mode fourth mode; based on the divided modes and corresponding working modes of the hybrid three-level DAB, respectively solving the inductive current and the transmission power in the full-bridge mode and the full-bridge half-bridge mode according to an equivalent circuit model and typical waveforms.
The equivalent circuit model consists of a primary full bridge, a secondary full bridge, a leakage inductance equivalent inductor, a high-frequency isolation transformer, a blocking capacitor and 3 bypass capacitors; the primary full bridge consists of 8 switching tubes and 4 diodes; the secondary full bridge consists of 4 switching tubes.
Step 200: calculating the effective value of the inductance current in each mode, and carrying out numerical discrete optimization on the effective value in the corresponding transmission power range to obtain an off-line optimal control table of the two modes; the method specifically comprises the following steps:
calculating the effective value of the inductance current in each mode, performing discrete numerical optimization on the effective value of the inductance current in a full power range by taking the effective value of the inductance current as an optimization target and taking transmission power and a soft switch as limiting conditions, and establishing an offline optimal control table of the two modes.
Step 300: comparing the optimized data in each off-line optimal control table, and determining a mode switching boundary; the method specifically comprises the following steps:
drawing k and P by using optimized data in each off-line optimal control table * 、i * rms A three-dimensional map; wherein k represents the ratio of input voltage to output voltage; p (P) * Representing transmission power; i.e * rms Representing the effective value of the inductor current; k, P of two modes * 、i * rms And overlapping the three-dimensional images, and demarcating a mode switching boundary on an intersection line of two images in a top view of the overlapped three-dimensional images by using a fuzzy piecewise linear method. When the mode switching boundary is marked by overlapping the top view of the three-dimensional graph, the intersection line of the two images in the top view is the mode switching boundary, but the mode switching boundary cannot be accurately described by an expression, so that the mode switching boundary is approximately marked by using a fuzzy piecewise linear method.
Step 400: and carrying out current modulation on the mixed three-level DAB by utilizing the mode switching boundary and the optimized control table. The method specifically comprises the following steps:
and using the mode switching boundary and the optimization control table to enable the mixed three-level DAB to generate corresponding direct-current bias voltage under the working mode of the corresponding mode so as to meet different input-output voltage ratios and finish current modulation.
On the basis of the technical scheme, the following embodiments are provided.
When input and output voltages are not matched based on the mixed three-level DAB under the traditional phase-shifting control, particularly under the light load condition, the inductance current stress and the reflux power of the traditional phase-shifting control are larger, the on-state loss is increased, and the efficiency of the converter is seriously reduced.
The present embodiment is thus ready to solve the following problems: 1. the problem that the effective value of the inductance current is larger when the three-level DAB is mixed under the traditional phase-shifting control is solved; 2. the traditional phase shift control has low flexibility; 3. and when the input voltage and the output voltage are not matched, the effective value of the inductance current is larger.
The embodiment discloses a modulation method for reducing inductance current of a hybrid three-level double-active-bridge converter. The topological structure of the transformer consists of a three-level full bridge, a two-level full bridge, equivalent leakage inductance, a high-frequency isolation transformer and a blocking capacitor connected in series with the secondary side of the transformer. The primary side three-level full bridge consists of 8 switching tubes and 4 clamping diodes, and the secondary side two-level full bridge consists of 4 switching tubes. Such a topology can reduce the voltage stress experienced by the switching tube and increase the converter flexibility, thereby enabling the converter to be used in higher voltage class applications, such as: solid state transformers, electric vehicles, medium voltage direct current grids, and the like.
In general, the converter commonly uses SPS modulation as a control method of the converter, but when the input-output voltage ratio k is not matched, the modulation has problems of difficulty in realizing soft switching, overlarge current stress and the like, which seriously increases loss and reduces energy transmission efficiency. To improve this, the present embodiment employs a modulation method of asymmetric duty cycle. Compared with the traditional modulation methods such as SPS, the ADPWM modulation of the embodiment adopts asymmetric PWM control signals in a primary three-level full bridge and symmetric PWM control signals in a secondary full bridge. And the mode switching between the full bridge and the half bridge of the secondary side is realized by matching the blocking capacitor at the secondary side with the PWM signal. Fig. 4 is a typical waveform of a three-level dual active bridge circuit with blocking capacitance in each mode under asymmetric duty cycle control, where V1 is the primary input voltage, V2 is the secondary output voltage,the phase difference between the primary bridge and the secondary bridge is represented by D, the duty ratio of the switching tube of the primary bridge, VAB, VCD, vcs, and DC bias voltage on the blocking capacitor.
In the scheme of the embodiment, under the full-bridge mode, cs does not generate direct current bias to the secondary side port voltage, and the direct current bias is considered to be 0 at the moment, and the secondary side port voltage has positive and negative output bus voltage and 0 three voltage levels; under the full-bridge half-bridge mode, cs generates direct current bias to the secondary side port voltage, and the direct current bias is considered to be half of the output direct current bus voltage at the moment, and the secondary side port voltage has positive and negative half of the output direct current bus voltage and 0 three voltage classes.
Firstly, dividing working areas in a full-bridge mode and a half-bridge mode; then analyzing the effective values of the inductance current and the transmission power under different mode modes, and performing discrete numerical optimization on the obtained effective values of the inductance current; based on the optimization result, comparing the optimized effective values in the half two modes to determine a mode switching boundary; finally, switching control of the three-level double-active bridge is completed in a matched mode switching boundary and an optimized control table.
In the scheme, the converter is controlled based on the mode switching boundary, so that the converter can generate corresponding direct-current bias voltage to adapt to different input-output voltage ratios k under the corresponding working mode, and the switching loss of the converter can be greatly reduced; meanwhile, the converter is controlled based on the optimal control table, so that the current effective value of the converter is reduced, the on-state loss is reduced, and the overall operation efficiency is improved on the premise of ensuring safe operation.
Thus, the algorithm described above uses PWM and inter-bridge phase shift angles of asymmetric duty cycle to control the magnitude and direction of energy transfer. And selecting a secondary bridge to work in a full bridge or half bridge mode according to the power transmission requirement, and then selecting an optimal working point according to an optimal working table, so that the transmission efficiency of the converter is improved when the effective value of the inductance current is reduced. Meanwhile, the running cost of the converter is reduced, and the flexibility of the converter is improved.
In addition, as a controller control flow as shown, the steps are respectively:
s1: dividing the hybrid three-level double-active-bridge converter into a full-bridge mode and a full-bridge half-bridge mode through control signals, and solving inductive current and transmission power in the full-bridge mode and the full-bridge half-bridge mode according to converter topology and switching signals;
s2: obtaining an effective value of the inductance current according to the inductance current solved in the step S1, and carrying out numerical optimization on the effective value in a full power range to obtain an offline optimization control table;
s3: comparing the effective values of the full-bridge mode and the full-bridge half-bridge mode to determine a mode switching boundary;
s4: and controlling the converter through the coordination of the mode switching boundary and the optimized control table.
The control method provided by the embodiment increases the control degree of freedom of the duty ratio on the basis of the conventional phase shift control method. Under the premise, the scheme switches the converter in different modes to solve the problems that when the input and output voltage transformation ratios are not matched, the effective current value is large and soft switching is difficult to realize; performing numerical discrete optimization on effective values of the inductance current under different modes, and establishing an offline optimal control table; comparing the effective values of the inductive currents in the full-bridge mode and the full-bridge half-bridge mode to determine a mode switching boundary; and finally, controlling the hybrid three-level double-active bridge through the coordination and matching of the switching boundary and the off-line optimal control table.
In the example, the control method based on the asymmetric duty ratio can realize the soft switching characteristic of the full power range when the ultra-light load or the input-output voltage transformation ratio is not matched; and the degree of freedom of control is increased, the flexibility of the converter is improved, the current stress is reduced, and the efficiency of the converter is improved. In addition, in the implementation patent, the converter is controlled based on the mode switching boundary, and the situation that the current stress is large and the soft switching range is small when the input-output voltage transformation ratio is not matched can be improved by generating direct current bias through the blocking capacitor at the secondary side of the transformer, so that no inductance current impact connection between mode switching is realized; and the converter is controlled based on the off-line optimal control table, so that the converter has good steady-state performance, and the overall efficiency is improved on the premise of ensuring the safe operation of the converter.
It should be noted that the hybrid three-level double-active-bridge converter topology is composed of a primary full bridge composed of 8 switching tubes (S11-S18) and 4 diodes (D1-D4), a secondary full bridge composed of 4 switching tubes (S21-S24), three bypass capacitors (C1, C2 and C3), a leakage inductance equivalent inductance L, a high-frequency isolation transformer T and a blocking capacitor Cs connected in series with the same, as shown in fig. 2. The input side direct current voltage source is V1, the output side direct current voltage source is V2, the transformer transformation ratio is n 1, and the capacitance value of C1 and C2 is the same.
In this embodiment, cs does not generate a voltage bias to the secondary side port voltage in the full-bridge mode, and is considered to be 0 at this time; and in the full-bridge half-bridge mode, cs generates voltage deviation on the secondary side port voltage, and the direct current bias is considered to be half of the output direct current bus voltage at the moment.
The hybrid three-level double-active-bridge converter inductance current effective value optimization control framework is shown in fig. 3, and specifically comprises the following steps:
the first step is to solve the instantaneous value of the inductive current and the transmission power of the hybrid three-level double-active-bridge converter based on the equivalent circuit model of the divided-mode down-converter and the control signal waveform.
Further, the dividing modes refer to full-bridge and full-bridge half-bridge modes, specifically:
determining that the full-bridge mode working modes comprise a full-bridge mode first mode, a full-bridge mode second mode, a full-bridge mode third mode and a full-bridge mode fourth mode according to the magnitude relation of the duty ratio of the three-level full-bridge switching tube and the phase shift angle between the bridges, the full-bridge half-bridge mode working modes comprise a full-bridge half-bridge mode first mode, a full-bridge half-bridge mode second mode, a full-bridge half-bridge mode third mode and a full-bridge half-bridge mode fourth mode.
In this example, the control method of the two modes is asymmetric duty cycle combined with inter-bridge phase shift. The duty ratio of the primary side switching tube is D, and the phase shift angle between the bridges isFour modes are providedMode of operation, ->In order to be in the mode i,for mode II->For mode III->The MODE IV is eight working MODEs in total, namely a full-bridge MODE (MODE A) MODE I, namely a full-bridge MODE first MODE; full-bridge MODE (MODE a) MODE ii, full-bridge MODE second MODE; full-bridge MODE (MODE a) MODE iii, i.e., full-bridge MODE third MODE; full-bridge MODE (MODE a) MODE iv, full-bridge MODE fourth MODE; full-bridge half-bridge MODE (MODE a) MODE i, i.e., full-bridge half-bridge MODE first MODE; full-bridge half-bridge MODE (MODE a) MODE ii, full-bridge half-bridge MODE second MODE; full-bridge half-bridge MODE (MODE a) MODE iii, i.e., full-bridge half-bridge MODE third MODE; full-bridge half-bridge MODE (MODE a) MODE iv, full-bridge half-bridge MODE fourth MODE. At the same time D, & lt & gt>Needs to meet->
The control quantity range is the whole operation range under the corresponding mode, and is the natural operation range before optimization. Wherein fig. 4 is a typical waveform diagram of the corresponding mode under the control of the asymmetric duty cycle modulation method. The instantaneous value of the inductor current and the transmission power can be obtained in combination with fig. 4 and an equivalent circuit model, as shown in table 1.
Table 1 transmission power and inductor current for mode
Step two, according to the instantaneous value of the inductance current obtained in the step one, solving the effective value of the inductance current by combining an effective value formula; and then discrete numerical optimizing is carried out on the effective value of the inductance current in the full power range by taking the effective value of the inductance current as an optimization target and taking the transmission power and the soft switch as limiting conditions, and an offline optimization control table of two modes is established.
It should be noted that the effective values i of the inductor currents in different mode * rms Obtained on the basis of equivalent circuit models of the respective modality modes, their expressions are therefore as follows:
MODE A Ⅰ：
MODE A Ⅱ:
MODE A Ⅲ:
MODE A Ⅳ:
MODE BⅠ:
MODE BⅡ:
MODE BⅢ:
MODE BⅣ:
in the above expression, the parameters k each represent an input-output voltage transformation ratio, k=v 1 /nV 2 Where n is the transformer ratio.
And thirdly, drawing three-dimensional graphs of two modes on the basis of an offline optimal control table, overlapping the three-dimensional graphs, and determining a mode switching boundary through a top view.
It should be noted that k, P of full-bridge and full-bridge half-bridge modes can be obtained by drawing a three-dimensional graph * 、i * rms And (5) a three-dimensional diagram. And then k and P of the two modes * 、i * rms And overlapping the three-dimensional images, and demarcating a mode switching boundary through overlapping the top view of the three-dimensional images, wherein the intersection line of the two images in the top view is the mode switching boundary. The mode switching boundary cannot be accurately described by an expression, and is approximately defined by a fuzzy piecewise linear method. K, P of each mode * 、i * rms Three-dimensional diagram is shown in FIG. 5, with k and P overlapping * 、i * rms The three-dimensional and top view is shown in fig. 6.
Boundary conditions of the two modes are:
when the transmission power and the voltage modulation ratio are in the abcd range, selecting MODE A, namely a full-bridge MODE; otherwise, MODE B is selected as the MODE of full-bridge half-bridge.
Fourth step is based on k and P * And determining a working mode, determining the duty ratio of the converter by a method of inquiring an offline optimal control table, and adjusting the phase shift angle between the bridges by a PI regulator to realize steady-state control of the converter. Fig. 7 is a control flow diagram of the controller performing the above method.
Finally, the program for realizing the control method is stored in the upper computer, and when the upper computer executes the program, the control method for the effective value of the mixed three-level double-active-bridge inductance current is realized.
It should be noted that, through this step, the system robustness and the dynamic response speed can be ensured while the system steady-state control requirement is achieved.
In order to further explain the technical scheme of the invention, the technical effect is highlighted, a hybrid three-level double-active-bridge converter simulation platform based on an asymmetric duty ratio modulation method and a traditional single phase shift modulation method is built, and parameters of the simulation platform are shown in table 2:
table 2 hybrid three level dual active bridge converter simulation platform parameters
Input voltage V1 200V
Output voltage V2 100V
Transformer transformation ratio n 2:1
Equivalent leakage inductance L 200μH
Switching frequency fs 10K Hz
Maximum transmission power Pbase 800W
Dc blocking capacitance Cp 1000μF
By giving the same transmission power P * And the modulation ratio k of the input voltage and the output voltage ensures that the method provided by the invention is consistent with the test working condition of the single phase shift modulation method, and the inductive current peak value and the inductive current effective value of the two methods are measured.
TABLE 3 simulation comparison of the present modulation method with the conventional modulation method
According to the simulation results of table 3, it can be seen that the modulation method of the present embodiment can effectively reduce the effective value of the inductance current and the current stress in the full power range compared with the single phase shift control, and greatly reduce the conduction loss.
In addition, the invention also provides electronic equipment, which comprises a memory and a processor, wherein the memory is used for storing a computer program, and the processor runs the computer program to enable the electronic equipment to execute the current modulation method of the mixed three-level DAB.
The present invention also provides a computer readable storage medium storing a computer program which when executed by a processor implements the current modulation method of hybrid three-level DAB as described above.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the core concept of the invention; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (8)

1. A current modulation method of hybrid three-level DAB, comprising:
dividing the current mode of the mixed three-level DAB, and determining the inductive current and the transmission power under the current mode; the current mode comprises a full-bridge mode and a full-bridge half-bridge mode;
calculating the effective value of the inductance current in each mode, and carrying out numerical discrete optimization on the effective value in the corresponding transmission power range to obtain an off-line optimal control table of the two modes;
comparing the optimized data in each off-line optimal control table, and determining a mode switching boundary;
and carrying out current modulation on the mixed three-level DAB by utilizing the mode switching boundary and the optimized control table.
2. The method for modulating the current of the hybrid three-level DAB according to claim 1, wherein the dividing the current mode of the hybrid three-level DAB to determine the inductor current and the transmission power in the current mode comprises the following steps:
dividing a full-bridge mode and a corresponding working mode and a full-bridge half-bridge mode and a corresponding working mode according to the magnitude relation of the duty ratio of a primary side switching tube and the phase shift angle between bridges of the hybrid three-level DAB; the working modes of the full-bridge mode comprise a full-bridge mode first mode, a full-bridge mode second mode, a full-bridge mode third mode and a full-bridge mode fourth mode; the working modes of the full-bridge half-bridge mode comprise a full-bridge half-bridge mode first mode, a full-bridge half-bridge mode second mode, a full-bridge half-bridge mode third mode and a full-bridge half-bridge mode fourth mode;
based on the divided modes and corresponding working modes of the hybrid three-level DAB, respectively solving the inductive current and the transmission power in the full-bridge mode and the full-bridge half-bridge mode according to an equivalent circuit model and typical waveforms.
3. The method for modulating the current of the hybrid three-level DAB according to claim 2, characterized in that the equivalent circuit model is composed of a primary full bridge, a secondary full bridge, a leakage inductance equivalent inductance, a high-frequency isolation transformer, a blocking capacitor and 3 bypass capacitors; the primary full bridge consists of 8 switching tubes and 4 diodes; the secondary full bridge consists of 4 switching tubes.
4. The method for modulating the current of the hybrid three-level DAB according to claim 1, characterized in that the effective value of the inductor current in each mode is calculated, and the effective value is subjected to numerical discrete optimization in a corresponding transmission power range, so as to obtain an off-line optimal control table of two modes, which comprises the following steps:
calculating the effective value of the inductance current in each mode, performing discrete numerical optimization on the effective value of the inductance current in a full power range by taking the effective value of the inductance current as an optimization target and taking transmission power and a soft switch as limiting conditions, and establishing an offline optimal control table of the two modes.
5. The method for current modulation of hybrid three-level DAB according to claim 1, wherein said determining a mode switching boundary by comparing the optimized data in each of said offline optimal control tables comprises:
drawing k and P by using optimized data in each off-line optimal control table * 、i * rms A three-dimensional map; wherein k represents the ratio of input voltage to output voltage; p (P) * Representing transmission power; i.e * rms Representing the effective value of the inductor current;
k, P of two modes * 、i * rms And overlapping the three-dimensional images, and demarcating a mode switching boundary on an intersection line of two images in a top view of the overlapped three-dimensional images by using a fuzzy piecewise linear method.
6. The method for current modulation of hybrid three-level DAB according to claim 1, characterized in that said hybrid three-level DAB is current modulated by means of said mode switching boundaries and said optimization control table, in particular comprising:
and using the mode switching boundary and the optimization control table to enable the mixed three-level DAB to generate corresponding direct-current bias voltage under the working mode of the corresponding mode so as to meet different input-output voltage ratios and finish current modulation.
7. An electronic device comprising a memory for storing a computer program and a processor that runs the computer program to cause the electronic device to perform the current modulation method of hybrid three-level DAB as claimed in claims 1-6.
8. A computer-readable storage medium, characterized in that it stores a computer program which, when executed by a processor, implements the method of current modulation of hybrid three-level DAB as claimed in claims 1-6.
CN202311072521.3A 2023-08-23 2023-08-23 Current modulation method, device and storage medium for mixed three-level DAB Pending CN117134625A (en)

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