CN117081403A - Mixed modulation method applied to wide output voltage CLLC converter - Google Patents

Mixed modulation method applied to wide output voltage CLLC converter Download PDF

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Publication number
CN117081403A
CN117081403A CN202311073417.6A CN202311073417A CN117081403A CN 117081403 A CN117081403 A CN 117081403A CN 202311073417 A CN202311073417 A CN 202311073417A CN 117081403 A CN117081403 A CN 117081403A
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China
Prior art keywords
modulation
converter
cllc
frequency
cllc converter
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Inventor
杨之青
吴周宇
陈鹏
苑梓恒
赵爽
李贺龙
丁立健
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Hefei University of Technology
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Hefei University of 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
    • H02M1/08—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
    • H02M1/14—Arrangements for reducing ripples from dc input or output
    • 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
    • H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
    • 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
    • H02M3/01—Resonant DC/DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33584—Bidirectional converters
    • 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)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a mixed modulation method applied to a CLLC converter with wide output voltage, which comprises the steps that the CLLC converter adopts phase-shift modulation in an idle state; the method comprises the steps of adopting mixed modulation of frequency conversion and phase shift under a non-empty state, wherein the CLLC converter selects and fixes the switching frequency in an under-resonance state under the empty state, and adopting phase shift modulation to meet the output requirement of a full voltage range; in the non-empty state, variable frequency modulation is adopted first, and phase shift modulation is introduced when the voltage reduction requirement cannot be met, so that the output voltage range is expanded. Aiming at the wide output voltage occasion, the invention considers the no-load state, reduces the ripple of the no-load output voltage through the mixed control of frequency conversion modulation and phase shift modulation, and widens the output voltage range, thereby realizing the wide output voltage of the converter in the no-load and non-no-load states.

Description

Mixed modulation method applied to wide output voltage CLLC converter
Technical Field
The invention belongs to the technical field of DC-DC converters, and particularly relates to a modulation method of wide voltage gain of a CLLC resonant converter.
Background
In recent years, development and utilization of new energy are rapidly developed due to the two challenges of energy shortage and environmental pollution. In applications in new energy fields such as new energy power generation, energy storage, and electric vehicle-mounted chargers, a DC-DC converter is an important link of power transmission, and its circuit performance has a significant influence on the efficiency of the whole system. Thus, high efficiency, high power density topologies have been the focus of research.
As an isolated DC-DC converter, CLLC converters have the advantages of low switching loss, good high-frequency characteristics, and capability of realizing bidirectional energy flow, and are often used in situations with high efficiency and power density requirements, because of zero-voltage turn-on. Currently, the analysis and modulation methods for CLLC converters generally follow the relevant methods for LLC converters. The traditional variable frequency modulation has wide switching range required by realizing wide gain, and excessive switching frequency also brings challenges to the design of devices, and the control effect of the variable frequency modulation is not ideal in a light load state. In some cases, CLLC converters also require the ability to output no load. In order to realize stable output voltage of the CLLC converter in an idle state, a hiccup mode is generally adopted for control in the prior art, but electromagnetic interference is easy to generate in the hiccup mode, and ripple waves of the output voltage are generally larger and the stability is poor.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a hybrid modulation method applied to a wide output voltage CLLC converter, aiming at the condition of converter load, phase-shift modulation is adopted to replace hiccup mode control in an idle state, and electromagnetic interference and output voltage ripple are reduced while adjustable output voltage is achieved; the mixed control of variable frequency modulation and phase shift modulation is adopted under the normal non-empty state, so that the defect of insufficient voltage reduction gain of variable frequency modulation can be overcome, and the wide output voltage can be realized.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention relates to a mixed modulation method applied to a CLLC converter with wide output voltage, which is composed of an inversion network composed of primary side H bridges, a resonant cavity and a rectification network composed of secondary side H bridges, wherein the resonant cavity is of a symmetrical structure composed of primary side resonance inductance, primary side resonance capacitance, secondary side resonance inductance, secondary side resonance capacitance and a transformer;
the primary side H bridge and the secondary side H bridge are formed by connecting two groups of bridge arms in parallel, and each group of bridge arms is formed by connecting two switching tubes in series;
the resonant cavity is a two-port network, one end of the resonant cavity is connected to the midpoints of two bridge arms of the primary side H bridge, and the other end of the resonant cavity is connected to the midpoints of two bridge arms of the secondary side H bridge; the method is characterized by comprising the following steps of:
step 1: determining an operating state of the CLLC converter based on an output current of the CLLC converter, comprising: dummy load idle state and normal non-idle state;
when the output current is greater than the current threshold I th When the CLLC converter is operated in a non-idle state;
when the output current is smaller than the current threshold I th When the CLLC converter works in an idle state;
step 2: selecting a modulation mode according to an operating state of the CLLC converter, comprising: variable frequency modulation and phase shift modulation;
when the CLLC converter is in idle state, the CLLC converter adopts phase-shifting modulation and changes the CLLCThe switching frequency of the converter is fixed at the under-resonant frequency f 1 ；
When the CLLC converter is in a non-empty state and the light load is low in gain, the CLLC converter adopts phase-shifting modulation and fixes the switching frequency of the CLLC converter at the maximum frequency f max ；
When the CLLC converter is in a non-empty load state and is not in light load and low in gain, the CLLC converter adopts variable frequency modulation;
when the CLLC converter is in a non-empty state and is switched between a light-load low-gain and a non-light-load low-gain, setting hysteresis time and correspondingly switching between two modulation modes;
step 3: and controlling the PWM wave driving signal by the frequency control quantity output by the variable-frequency modulated compensator or the phase-shift angle control quantity output by the phase-shift modulated compensator so as to control the switching tube on logic of the inverter network, thereby controlling the output voltage of the CLLC converter.
The hybrid modulation method applied to the wide output voltage CLLC converter is also characterized in that:
the variable frequency modulation is to control the switching frequency of two bridge arm switching tubes of the primary side H bridge to control the output voltage;
the phase shift modulation is to control the output voltage by controlling the phase shift angle of the opening time sequence of the switching tubes of the two bridge arms of the primary side H bridge.
When the two modulation modes are correspondingly switched, if the variable frequency modulation is switched to the phase shift modulation, the switching frequency is used as a switching limit, and if the phase shift modulation is switched to the variable frequency modulation, the phase shift angle is used as a switching limit.
The switching process from variable frequency modulation to phase shift modulation is as follows:
when the switching frequency of the CLLC converter is increased to the maximum frequency f max And at a lag time t th When the internal gain is not reached, the switching frequency is fixed at f max The CLLC converter starts phase-shift modulation;
the switching process from phase-shift modulation to variable frequency modulation is as follows:
when the phase shift angle of the CLLC converter is reduced to 0 and at the hysteresis time t th Internal increaseWhen the gain is not reached, the phase shift angle is fixed at 0, and the CLLC converter starts variable frequency modulation.
The CLLC converter adopts a variable-frequency PI controller and a phase-shifting PI controller as compensators respectively;
and after the given voltage value is differenced with the voltage value actually output, the difference value is sent to a corresponding compensator, so that the frequency control quantity output by the variable-frequency modulated compensator and the phase-shift angle control quantity output by the phase-shift modulated compensator are respectively obtained and used for controlling the on-off of a switching tube in the primary side H bridge.
Compared with the prior art, the invention has the advantages that:
aiming at the CLLC converter, the invention adopts phase-shift modulation under the underresonant frequency for the idle state of the CLLC converter, and the converter realizes wide voltage output under the idle state. Meanwhile, for the non-empty state of the converter, the mixed control of variable frequency modulation and phase shift modulation is adopted, the defect of insufficient gain of variable frequency modulation under light load and low gain is overcome, and the frequency and phase shift angle are adopted as modulation switching and hysteresis conditions, so that the gain of the mixed control of variable frequency modulation and phase shift modulation is continuous, the voltage overshoot is small during switching, and the control is stable.
Drawings
FIG. 1 is a topology of a CLLC converter circuit of the present invention;
FIG. 2 is a control flow diagram of a CLLC converter according to the present invention;
FIG. 3 is a timing diagram of the driving of variable frequency modulation and phase shift modulation of the CLLC converter of the present invention;
FIG. 4 is a normalized gain curve under variable frequency modulation of a CLLC converter in the present invention;
FIG. 5 is a gain curve for phase-shifting modulation of a CLLC converter according to the present invention;
FIG. 6 is a control block diagram of a CLLC converter according to the present invention;
FIG. 7 is a graph of experimental results of the idle state of the CLLC converter in the present invention;
fig. 8 is a graph of experimental results of switching between variable frequency modulation and phase shift modulation in a non-empty state of a CLLC converter according to the present invention.
Detailed Description
In order to more clearly and clearly describe the technical scheme of the implementation of the invention, the specific implementation of the invention is further described below through the attached drawings and the embodiments.
In this embodiment, a hybrid modulation method applied to a CLLC converter with wide output voltage is to consider an idle state in a wide output situation of the CLLC converter, reduce an idle output voltage ripple through hybrid control of variable frequency modulation and phase shift modulation, widen an output voltage range, and realize wide output voltages of the converter in idle and non-idle states. The circuit topology structure applied by the method is shown in fig. 1, and comprises the following steps: the inverter network is a primary side H bridge formed by connecting two bridge arms in parallel, and the primary side H bridge comprises a switching tube S P1 And a switch tube S P2 A primary side first bridge arm and a switch tube S P3 And a switch tube S P4 A primary side second bridge arm is formed; the rectifying network is a secondary side H bridge formed by connecting two bridge arms in parallel, and the secondary side H bridge comprises a switching tube S S1 And a switch tube S S2 A first bridge arm of the secondary side and a switch tube S S3 And a switch tube S S4 A second bridge arm of the secondary side is formed; the resonant cavity is a two-port network with symmetrical structure and comprises a primary side resonant inductor L r Primary side resonance capacitor C r Secondary side resonant inductance L s Secondary side resonance capacitor C s And a transformer, the transformation ratio of the transformer being n; one end of the high-voltage side of the resonant cavity is connected to the middle point of two bridge arms of the primary side H bridge, and one end of the low-voltage side is connected to the middle point of two bridge arms of the secondary side H bridge.
Specifically, the method comprises the following steps:
step 1: determining an operating state of the CLLC converter based on an output current of the CLLC converter, comprising: dummy load idle state and normal non-idle state, the flow of which is shown in figure 2;
when the output current is greater than the current threshold I th Indicating CLLC converter operationIn a non-empty state;
when the output current is smaller than the current threshold I th When the CLLC converter works in an idle state;
step 2: selecting a modulation mode according to an operating state of the CLLC converter, comprising: variable frequency modulation and phase shift modulation; the variable frequency modulation is to control the switching frequency of two bridge arm switching tubes of the primary side H bridge to control the output voltage; the phase shift modulation is to control the output voltage by controlling the phase shift angle of the opening time sequence of the switching tubes of the two bridge arms of the primary side H bridge.
When the CLLC converter is in an idle state, the CLLC converter adopts phase-shifting modulation and fixes the switching frequency of the CLLC converter at the under-resonance frequency f 1 ；
When the CLLC converter is in a non-empty state and the light load is low in gain, the CLLC converter adopts phase-shifting modulation and fixes the switching frequency of the CLLC converter at the maximum frequency f max ；
When the CLLC converter is in a non-empty load state and is not in light load and low in gain, the CLLC converter adopts variable frequency modulation;
when the CLLC converter is in a non-empty state and is switched between a light-load low-gain and a non-light-load low-gain, setting hysteresis time and correspondingly switching between two modulation modes;
during frequency conversion modulation and phase shift modulation of the CLLC converter, the PWM wave driving signals of the four switching tubes of the primary side H bridge have the same frequency, the duty ratio is 0.5, and the switching tubes S P1 And a switch tube S P2 The phase difference of PWM wave is 180 degrees, and is in a complementary state, and dead time is set to prevent direct connection, and a switching tube S P3 And a switch tube S P4 The phase difference of the PWM waves is 180 degrees, the PWM waves are in a complementary state, and dead time is set to prevent direct connection. Wherein the PWM wave of the primary side H bridge diagonal switching tube is the same when in variable frequency modulation, namely the switching tube S P1 And a switch tube S P3 PWM wave is the same, switch tube S P2 And a switch tube S P4 The PWM waves are the same; the primary side H bridge has alpha phase difference to the PWM wave of the diagonal switching tube, namely the switching tube S during phase shifting modulation P3 PWM wave hysteresis switch tube S P1 PWM wave alpha degree, switch tube S P4 PWM wave hysteresis switch tube S P2 PWMWave alpha degree, the phase shift modulation is an internal phase shift modulation. The driving sequence of the CLLC converter switching tube is shown in fig. 3, wherein the phase shift angle α is 0 when frequency-variable modulating.
In this embodiment, under the analysis of fundamental wave equivalent model, taking the ideal state of the circuit into consideration, the gain-normalized frequency curve of the CLLC converter under variable frequency modulation is shown in fig. 4, and the voltage gain formula is formula (1):
in the formula (1), f n ＝f s /f r Is the normalized frequency (f s Is the switching frequency, f r Is the resonant frequency),is the quality factor, k=l m /L r Is the excitation inductance ratio, h=c seq /C r Is capacitance ratio (C seq ＝C s /n 2 )，g＝L seq /L r Is the inductance ratio (L seq ＝n 2 L s )。
The gain magnitude of the CLLC converter varies with the conversion of its operating frequency, whereby the gain magnitude of the converter can be varied by adjusting the operating frequency of the converter. The gain of the CLLC converter is related to the load when the switching frequency is fixed after the resonant cavity parameters of the CLLC converter are given, as shown in fig. 4, which shows the gain curves of the CLLC converter under different loads, which is consistent with the fact that the gain of the CLLC converter is hardly reduced as the switching frequency continues to increase after the switching frequency has increased to a certain value.
When the switching frequency is fixed, the gain-phase angle curve of the CLLC converter under phase-shift modulation is shown in fig. 5, and the voltage gain formula is formula (2):
G＝cos(α) (2)
in the formula (2), alpha is a phase shift angle, and the purpose of reducing the voltage can be achieved through phase shift modulation, so that the defect of insufficient gain under variable frequency modulation is overcome.
CLLC converterWhen in no-load state, phase-shift modulation is adopted, and because the phase-shift modulation can only reduce voltage, in order to enable the CLLC converter to boost and reduce voltage for output, the full-range output voltage is realized, and the switching frequency is selected and fixed at the under-resonance frequency f 1 。
When the converter is in a non-empty state, the single variable frequency modulation has the defect of insufficient voltage reduction gain, and the mixed modulation of variable frequency modulation and phase shift modulation is adopted.
When the two modulation modes are correspondingly switched, if the variable frequency modulation is switched to the phase shift modulation, the switching frequency is used as a switching limit, and if the phase shift modulation is switched to the variable frequency modulation, the phase shift angle is used as a switching limit.
The switching process from variable frequency modulation to phase shift modulation is as follows:
when the switching frequency of the CLLC converter is increased to the maximum frequency f max And at a lag time t th When the internal gain is not reached, the switching frequency is fixed at f max The CLLC converter starts phase-shift modulation;
the switching process from phase-shift modulation to variable frequency modulation is as follows:
when the phase shift angle of the CLLC converter is reduced to 0 and at the hysteresis time t th When the internal gain is not reached, the phase shift angle is fixed at 0, and the CLLC converter starts variable frequency modulation.
Step 3: the CLLC converter adopts a variable-frequency PI controller and a phase-shifting PI controller as compensators respectively;
as shown in fig. 6, after a given voltage value is differenced from an actually output voltage value, the difference value is sent to a corresponding compensator, so that a frequency control amount output by the variable-frequency-modulated compensator and a phase-shift angle control amount output by the phase-shift-modulated compensator are obtained respectively, and a PWM wave driving signal is controlled to control the on-off logic of a switching tube of the inverter network, namely, to control the on-off of the switching tube in the primary side H bridge, so as to control the output voltage of the CLLC converter.
In order to verify the feasibility of the technical scheme, an experimental circuit of the CLLC converter is built.
In this embodiment, the parameters of the CLLC converter are as follows: the input voltage is 800V, the output voltage is 200-500V, the switching frequency is 70kHZ-200kHz, the primary side resonance inductance is 20 muH, the primary side resonance capacitance is 75nF, the secondary side resonance inductance is 10.33 muH, the secondary side resonance capacitance is 188nF, the excitation inductance is 92 muH, the transformation ratio of the transformer is 2.4, and the rated power of the converter is 11kW.
As shown in fig. 7, the experimental waveform of the output voltage of the CLLC converter in the no-load state is shown, wherein the part (a) in fig. 7 is the output voltage 300V, the part (b) in fig. 7 is the output voltage 400V, and the part (c) in fig. 7 is the output voltage 500V. From experimental results, the CLLC converter adopts phase-shift modulation under the under-resonance frequency in the no-load state, so that the control of boosting and reducing can be realized, the ripple wave of the output voltage is smaller, and the control effect is more ideal.
The switching of the variable frequency modulation and the phase shift modulation is performed in the manner described above, and the resulting waveform of the CLLC converter output voltage in this manner is shown in fig. 8. Wherein the output voltage is controlled at 220v,1800w output power is the limit of variable frequency modulation and phase shift modulation. The output power of the CLLC converter 1610W and the output power of 1930W are shown in the figure, when the output power of the CLLC converter is 1610W, it is operated in the phase-shift modulation mode, when the output power of the converter is 1930W, it is operated in the variable-frequency modulation mode, the two modulation modes are switched with a certain hysteresis time, part (a) in fig. 8 shows the output voltage waveform when the phase-shift modulation is switched to the variable-frequency modulation, and part (b) in fig. 8 shows the output voltage waveform when the variable-frequency modulation is switched to the phase-shift modulation. From the experimental results, the overshoot of the output voltage is smaller during switching.
The above embodiments are detailed descriptions of the technical solutions of the present invention, and it can be seen from the experimental results of the embodiments that the technical solutions of the present invention have high feasibility.

Claims (5)

1. The mixed modulation method is applied to a CLLC converter with wide output voltage, wherein the CLLC converter is an inversion network formed by a primary side H bridge, a resonant cavity and a rectification network formed by a secondary side H bridge, and the resonant cavity is a symmetrical structure formed by a primary side resonant inductor, a primary side resonant capacitor, a secondary side resonant inductor, a secondary side resonant capacitor and a transformer;
the primary side H bridge and the secondary side H bridge are formed by connecting two groups of bridge arms in parallel, and each group of bridge arms is formed by connecting two switching tubes in series;
the resonant cavity is a two-port network, one end of the resonant cavity is connected to the midpoints of two bridge arms of the primary side H bridge, and the other end of the resonant cavity is connected to the midpoints of two bridge arms of the secondary side H bridge; the method is characterized by comprising the following steps of:
step 1: determining an operating state of the CLLC converter based on an output current of the CLLC converter, comprising: dummy load idle state and normal non-idle state;
when the output current is greater than the current threshold I th When the CLLC converter is operated in a non-idle state;
when the output current is smaller than the current threshold I th When the CLLC converter works in an idle state;
step 2: selecting a modulation mode according to an operating state of the CLLC converter, comprising: variable frequency modulation and phase shift modulation;
when the CLLC converter is in an idle state, the CLLC converter adopts phase-shifting modulation and fixes the switching frequency of the CLLC converter at the under-resonance frequency f 1 ；
When the CLLC converter is in a non-empty state and the light load is low in gain, the CLLC converter adopts phase-shifting modulation and fixes the switching frequency of the CLLC converter at the maximum frequency f max ；
When the CLLC converter is in a non-empty load state and is not in light load and low in gain, the CLLC converter adopts variable frequency modulation;
when the CLLC converter is in a non-empty state and is switched between a light-load low-gain and a non-light-load low-gain, setting hysteresis time and correspondingly switching between two modulation modes;
step 3: and controlling the PWM wave driving signal by the frequency control quantity output by the variable-frequency modulated compensator or the phase-shift angle control quantity output by the phase-shift modulated compensator so as to control the switching tube on logic of the inverter network, thereby controlling the output voltage of the CLLC converter.
2. The hybrid modulation method applied to a wide output voltage CLLC converter of claim 1, wherein:
the variable frequency modulation is to control the switching frequency of two bridge arm switching tubes of the primary side H bridge to control the output voltage;
the phase shift modulation is to control the output voltage by controlling the phase shift angle of the opening time sequence of the switching tubes of the two bridge arms of the primary side H bridge.
3. The hybrid modulation method applied to a wide output voltage CLLC converter of claim 1, wherein: when the two modulation modes are correspondingly switched, if the variable frequency modulation is switched to the phase shift modulation, the switching frequency is used as a switching limit, and if the phase shift modulation is switched to the variable frequency modulation, the phase shift angle is used as a switching limit.
4. A hybrid modulation method applied to a wide output voltage CLLC converter of claim 3, wherein:
the switching process from variable frequency modulation to phase shift modulation is as follows:
when the switching frequency of the CLLC converter is increased to the maximum frequency f max And at a lag time t th When the internal gain is not reached, the switching frequency is fixed at f max The CLLC converter starts phase-shift modulation;
the switching process from phase-shift modulation to variable frequency modulation is as follows:
when the phase shift angle of the CLLC converter is reduced to 0 and at the hysteresis time t th When the internal gain is not reached, the phase shift angle is fixed at 0, and the CLLC converter starts variable frequency modulation.
5. The hybrid modulation method applied to a wide output voltage CLLC converter of claim 1, wherein:
the CLLC converter adopts a variable-frequency PI controller and a phase-shifting PI controller as compensators respectively;
and after the given voltage value is differenced with the voltage value actually output, the difference value is sent to a corresponding compensator, so that the frequency control quantity output by the variable-frequency modulated compensator and the phase-shift angle control quantity output by the phase-shift modulated compensator are respectively obtained and used for controlling the on-off of a switching tube in the primary side H bridge.
CN202311073417.6A 2023-08-24 2023-08-24 Mixed modulation method applied to wide output voltage CLLC converter Pending CN117081403A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117175968A (en) * 2023-11-05 2023-12-05 浙江大学 Single-stage CLLC bidirectional converter and control method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117175968A (en) * 2023-11-05 2023-12-05 浙江大学 Single-stage CLLC bidirectional converter and control method thereof
CN117175968B (en) * 2023-11-05 2024-02-13 浙江大学 Single-stage CLLC bidirectional converter and control method thereof

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