CN114448274A - Three-phase single-stage resonant type electric energy conversion device and control method - Google Patents
Three-phase single-stage resonant type electric energy conversion device and control method Download PDFInfo
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- CN114448274A CN114448274A CN202210376910.4A CN202210376910A CN114448274A CN 114448274 A CN114448274 A CN 114448274A CN 202210376910 A CN202210376910 A CN 202210376910A CN 114448274 A CN114448274 A CN 114448274A
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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
- 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
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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
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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
- 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
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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
- 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
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- 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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Abstract
The invention provides a three-phase single-stage resonant type electric energy conversion device which comprises an AC/DC (alternating current/direct current) rectification circuit and a DC/DC resonance circuit, wherein the input end of the AC/DC rectification circuit is connected with three-phase alternating current, the output end of the AC/DC rectification circuit comprises a first terminal, a second terminal and a third terminal, the first terminal outputs the maximum forward value of the three-phase alternating current, the second terminal outputs the middle value of the three-phase alternating current, the third terminal outputs the maximum reverse value of the three-phase alternating current, the DC/DC resonance circuit is connected with the output end of the AC/DC rectification circuit and comprises a three-level bridge unit, the input end of the three-level bridge unit is connected with the first terminal and the third terminal, and the middle point of a bridge arm of the three-level bridge unit is connected with the second terminal. The electric energy conversion device realizes power factor correction and output current or voltage regulation, and improves the reliability, conversion efficiency and power density of the electric energy conversion device.
Description
Technical Field
The invention belongs to the field of electric energy conversion, and particularly relates to a control method of a matrix type full-bridge circuit.
Background
An isolated AC/DC converter generally adopts a two-stage structure, the front stage adopts a three-phase PFC converter structure to complete a three-phase current control task, various power grid distortion problems are solved, the power quality of a power grid is ensured, the rear stage adopts an isolated DCDC structure to realize electrical isolation between a power supply side and a power utilization side, and stable output voltage is realized under different load conditions. However, because of two-stage power conversion, the structure has the defects of low conversion efficiency, high cost and the like. In addition, the two-stage configuration also requires bulky bus capacitors (typically using inexpensive and short-lived electrolytic capacitors) to buffer the energy of the front and rear stage converters, which reduces the reliability of the converters and limits the optimization of their power density.
Compared with a two-stage structure, the single-stage ACDC converter structure can improve the overall efficiency and the power density of the converter by reducing the energy conversion level and removing the intermediate direct-current bus capacitor, and is more consistent with the design requirements of the current AC/DC power supply equipment.
In the known technology, single-stage ACDC energy conversion can be realized through a complex control strategy, but soft switching of all switching tubes under the full-load condition cannot be guaranteed, so that the popularization and application of the converter are limited.
Disclosure of Invention
In order to solve the technical problems in the background art, the DC/DC resonant circuit is added into the low-frequency rectification conversion process, soft switching of the high-frequency switching tube in the three-level bridge unit is realized by virtue of the LLC resonant unit so as to reduce switching loss, and meanwhile, the wide gain characteristic of the DC/DC resonant circuit is utilized to complete three-phase input current control and output voltage or current control by adjusting the switching frequency and duty ratio of the high-frequency switching tube in the three-level bridge unit.
In order to achieve the purpose, the invention mainly adopts the following technical scheme:
a three-phase single-stage resonant power conversion device comprises,
an AC/DC rectification circuit having an input terminal to which a three-phase alternating current is connected, an output terminal including a first terminal outputting a maximum value of the three-phase alternating current in a forward direction, a second terminal outputting an intermediate value of the three-phase alternating current, and a third terminal outputting a maximum value of the three-phase alternating current in a reverse direction,
the DC/DC resonance circuit is connected with the output end of the AC/DC rectification circuit and comprises a three-level bridge unit, a resonance unit and an output rectification filter unit, wherein the input end of the three-level bridge unit is connected with a first terminal and a third terminal, the middle point of a bridge arm of the three-level bridge unit is connected with a second terminal, the input end of the resonance unit is connected with the output end of the three-level bridge unit in parallel, and the rectification filter unit is connected with the output end of the resonance unit in parallel.
The AC/DC rectification circuit comprises a three-phase rectification unit, wherein the three-phase rectification unit comprises an A-phase bridge arm module, a B-phase bridge arm module and a C-phase bridge arm module, the A-phase bridge arm module, the B-phase bridge arm module and the C-phase bridge arm module are connected in parallel, the three-phase alternating current is respectively connected with the bridge arm middle points of the A-phase bridge arm module, the B-phase bridge arm module and the C-phase bridge arm module, the AC/DC rectification circuit also comprises an A-phase bidirectional switch, a B-phase bidirectional switch and a C-phase bidirectional switch, one end of the A-phase bidirectional switch, one end of the B-phase bidirectional switch and one end of the C-phase bidirectional switch are respectively connected with bridge arm middle points of the A-phase bridge arm module, the B-phase bridge arm module and the C-phase bridge arm module, the other end of the A-phase bidirectional switch, the B-phase bidirectional switch and the C-phase bidirectional switch are connected in parallel to form a second terminal, and the A-phase, the B-phase and the C-phase of three-phase alternating current are respectively connected with bridge arm middle points of the A-phase bridge arm module, the B-phase bridge arm module and the C-phase bridge arm module.
The resonance unit comprises an inductor, a capacitor and a transformer, wherein the inductor, the capacitor and the transformer are connected in series.
The three-level bridge unit is a half-bridge three-level bridge unit or a full-bridge three-level bridge unit.
The invention also provides a control method of the three-phase single-stage resonant type electric energy conversion device, which comprises the following steps,
step T01 of sampling the three-phase alternating current, comparing the absolute voltage values of the alternating currents of each phase, where the phase with the maximum absolute voltage value is the first phase, the phase with the intermediate absolute voltage value is the second phase, and the phase with the minimum absolute voltage value is the third phase;
step T02 turns off the bidirectional switches connected in the first phase and the second phase, the bidirectional switches being the a-phase bidirectional switch, the B-phase bidirectional switch, and the C-phase bidirectional switch, and turns on the bidirectional switch connected in the third phase, the bidirectional switches being the a-phase bidirectional switch, the B-phase bidirectional switch, and the C-phase bidirectional switch;
step T03, sampling the output current, adjusting the output current with a reference value of the output current to generate a first reference value, multiplying the first reference value with a second phase voltage of the three-phase alternating current to generate a reference value of the phase current, and adjusting the first reference value with the sampling value of the phase current to generate a first duty ratio of a switch in the three-level bridge unit;
step T04, multiplying the first reference value by the first phase voltage of the three-phase ac power to generate a reference value of the phase current, and adjusting the reference value and the sampled value of the phase current to generate a switching period for switching control in the three-level bridge unit;
and step T05, when the switching period is greater than the first set value, setting the switching period to the first set value, multiplying the first reference value by the first phase voltage of the three-phase alternating current to generate a reference value of the phase current, and adjusting the reference value of the phase current with the sampled value of the phase current to generate a second duty ratio for switching control in the three-level bridge unit.
The time multiplied by the first duty ratio and the switching period is a first moment, the switching control period starts to the first moment, and the voltage at two ends of the resonance unit is controlled to be the voltage between the first terminal and the second terminal.
And controlling the voltage between two ends of the resonance unit to be the voltage between the first terminal and the third terminal or the voltage between the third terminal and the second terminal between the first time and one half of the switching period.
And the time multiplied by the second duty ratio and the switching period is the second moment, and the voltage at two ends of the resonance unit is controlled to be the voltage between the first terminal and the third terminal or the voltage between the third terminal and the second terminal between the first moment and the second moment.
And controlling the voltage at two ends of the resonance unit to be zero between the second moment and one half of the switching period.
The switching cycle includes a positive half-cycle and a negative half-cycle in which the voltage across the resonant unit is controlled to be positive and negative symmetric.
The switching period comprises a positive half-period in which the voltage across the resonant cell is controlled to have an input voltage and a negative half-period in which the voltage across the resonant cell is controlled to be zero.
The invention adds various forms of DC/DC resonant circuits into the low-frequency rectification AC/DC rectification circuit, ensures that the high-frequency switching tube realizes soft switching under all conditions by means of the LLC resonance unit so as to reduce switching loss, and simultaneously adjusts output voltage or current and three-phase input current by utilizing the wide gain characteristic of the DC/DC resonant circuit. Three phase voltages are converted into three line voltages by a low frequency rectifying AC/DC rectifying circuit to cope with distorted and unbalanced grid conditions.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings according to the drawings.
Fig. 1 is a schematic block diagram of a three-phase single-stage resonant converter according to the present invention.
Fig. 2 shows a first embodiment of the three-phase single-stage resonant converter of the present invention.
Fig. 3 shows a second embodiment of the three-phase single-stage resonant converter of the present invention.
Fig. 4 shows a third embodiment of the three-phase single-stage resonant converter of the present invention.
Fig. 5 shows a fourth embodiment of the three-phase single-stage resonant converter of the present invention.
Fig. 6 shows a fifth embodiment of the three-phase single-stage resonant converter of the present invention.
Fig. 7 is a waveform diagram of key points in the AC/DC rectifier circuit of fig. 2-6.
Fig. 8 is a waveform diagram of key points of the control method shown in fig. 11 for controlling the DC/DC resonant circuit in the embodiment shown in fig. 4.
Fig. 9 is a waveform diagram of key points of the DC/DC resonant circuit in the first operating state in the embodiment of fig. 6 controlled by the control method shown in fig. 11.
Fig. 10 is a waveform diagram of a key point of the control method shown in fig. 11 in the second working state of the DC/DC resonant circuit in the embodiment shown in fig. 6.
Fig. 11 is a flowchart of a control method of the three-phase single-stage power conversion device according to the present invention.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Fig. 1 is a schematic block diagram of a three-phase single-stage resonant conversion device according to the present invention, in which a three-phase AC power is input to an AC/DC rectifier circuit 11, the AC/DC rectifier circuit 11 outputs a DC power to three terminals PYN, and a DC/DC resonant circuit 12 converts the power at the three terminals PYN to an output voltage Vo to a load. The DC/DC resonant circuit 12 regulates the output voltage Vo and the three-phase input currenti A i B i C Or regulating the output current Io and the three-phase input currenti A i B i C 。
In an embodiment, the AC/DC rectifying circuit 11 is, for example, an AC/DC rectifying circuit in a low-frequency operating state, which improves the capability of the single-stage power conversion device to cope with fault conditions such as grid distortion and three-phase imbalance.
The DC/DC resonant circuit 12 uses an LLC resonant unit to ensure that a high-frequency switch in the DC/DC resonant circuit 12 realizes soft switching under all conditions so as to reduce switching loss, and simultaneously uses the wide gain characteristic of the LLC resonant unit to regulate the output voltage Vo or the output current Io and the three-phase input currenti A i B i C 。
As shown in fig. 2, the AC/DC rectifying circuit 21 according to the first embodiment of the present invention includes a three-phase rectifying unit 211 and bidirectional switching tubes Say, Sby, and Scy that are switched on at low frequencies at the time when the two-phase voltages intersect. The two-phase bidirectional switch with larger voltage amplitude absolute value in the two intersected phases is turned off, and the two-phase bidirectional switch with smaller amplitude is turned on at the same time. Thus, in the three-phase rectifying unit 211, one phase with a larger amplitude in the positive voltage is connected to the P terminal through the upper end diode Dap or Dbp or Dcp, one phase with a larger amplitude in the negative voltage is connected to the N terminal through the lower end diode Dan or Dbn or Dcn, and the remaining one phase is connected to the Y terminal through the conducted bidirectional switch tube Say, Sby or Scy, in combination with fig. 7, the three-phase rectifying unit will be describedu A 、u B 、u C Become intou P 、u N 、u Y To obtain three forward line voltagesu PN 、u PY Andu YN in whichu PN The input voltage is always the largest one, no matter whether the input voltage is in normal power supply or has the problems of distortion or three-phase imbalance and the like,u PN one and two of the others being always the largestu PY Andu YN alternating.
The DC/DC resonant circuit 22 regulates the output voltage Vo and the three-phase input currenti A i B i C Or regulating the output current Io and the three-phase input currenti A i B i C 。
Referring to fig. 3 again, the AC/DC rectifying circuit 31 outputs a DC power to three terminals PYN, and the DC/DC resonant circuit 32 converts the power at three terminals PYN to an output voltage Vo to the load. The DC/DC resonant circuit 32 regulates the output voltage Vo and the three-phase input currenti A i B i C Or regulating the output current Io and the three-phase input currenti A i B i C 。
The input voltage of the DC/DC resonant circuit 32 is three line voltagesu PN 、u PY Andu YN switching the switches in the three-level bridge unit 321 at high frequency to apply voltageu PN 、u PY 、u YN And the 0 level are fed to the LLC resonant unit 322, which LLC resonant unit 322 is used to provide soft switching conditions for the switches in the three-level bridge unit 321. The rectifying and filtering unit 323 is connected in parallel with the secondary winding of the transformer T to rectify and filter the electric energy output by the transformer T.
Fig. 4 is a schematic diagram of an embodiment of the present invention, in which the three-level bridge unit 421 is a three-level half-bridge unit, and the rectifying and filtering unit 423 is a full-bridge rectifying and filtering unit. The waveforms of the input voltage and the resonant current of the specific switching logic and LLC resonant unit 422 are shown in FIG. 8. Wherein the resonant currenti Lr For the current flowing from the input of the LLC resonant unit 422, the excitation currenti Lm The bit flows through the field current of the transformer T, as will be described below. Here in order tou PY Is greater thanu YN The corresponding switching cycle is taken as an example, and the corresponding working process is introduced:
1) stage 1[ t0-t1]: at time t0, switches S1 and S4 are turned on, and the LLC resonant unit input voltage isu PN The inductance Lr and the capacitance Cr resonate, and the resonant currenti Lr From negative to positive. At t1= DTsAt time S4 is turned off, the resonant currenti Lr The junction capacitor of S4 is charged and the junction capacitor of switch S3 is discharged until the capacitor voltage drops to 0, and the body diode of S3 is turned on to provide a zero voltage turn-on condition for S3. In this phase, a resonant current flows in from the terminal P and out from the terminal N.
2) Stage 2[ t1-t2]: at time t2, the switch S3 turns on at zero voltage, and the LLC resonant unit 221 input voltage becomesu PY The inductor Lr and the capacitor Cr continue to resonate, if the resonant current flowsi Lr Equal to the excitation currenti Lm It becomes three-element resonance of inductance Lr, inductance Lm and capacitance Cr. At T2= TsAt time/2, switch S1 is turned off, and the resonant current flowsi Lr Still positive, the capacitor at the junction of switch S1 is charged, while the capacitor at the junction of switch S2 is discharged until the capacitor voltage drops to 0, providing a zero voltage turn-on condition for switch S2. In this phase, the resonant currenti Lr Flows in from the P end and flows out from the Y end.
After the input energy processed by the AC/DC rectifying circuit 41 is transferred to the LLC resonant unit 422 in the whole positive half cycle, part of the energy in the LLC resonant unit 422 is transferred to the secondary side, and part of the energy is stored in the resonant capacitorCrAnd form a resonant capacitorCrA dc bias on.
3) Stage 3[ t2-t3]: at time t3, S2 turns on at zero voltage, the LLC resonant unit 422 input voltageu LLC When the voltage becomes 0, the inductor Lr and the capacitor Cr resonate again, and the resonant current flowsi Lr From positive to negative. At T = TsAt the moment, the switches S2 and S3 are turned off, and the negative resonant current is generatedi Lr The capacitor across switches S2 and S3 is charged while the capacitor across switches S1 and S4 is discharged until the capacitor voltage drops to 0, providing a zero voltage turn-on condition for switches S1 and S4. In this stage, a resonance-free current flows through the AC/DC rectifying circuit 41. Resonance capacitorCrThe upper stored energy is transferred to the secondary side, the resonant capacitorCrThe dc bias on becomes the input voltage of the LLC resonant unit 422.
When in useu PY Is less thanu YN When the input voltage of only the positive half-cycle of the LLC resonant unit becomesu PY Andu YN the switches S1, S2 and S3, S4 are logically changed, and the working process is almost similar.
The embodiment shown in fig. 4 realizes three-phase ACDC conversion by a single-stage conversion structure, and all high-frequency switches can obtain soft switching conditions by means of an LLC resonant unit, so that the efficiency of energy transfer of the whole ACDC conversion system is higher, and at the same time, by means of an AC/DC rectifier circuit 41, various three-phase voltage conditions can be handled: whether the three phases are balanced or faults such as distortion, unbalance and the like occur. When a fault occurs, the control unit controls the operation of the control unit,u PN 、u PY andu YN the forward direction of the air flow is kept,u PN the line voltage in which the amplitude is the largest. In addition, the DC/DC resonant circuit 42 only has 4 high-frequency switches, the cost is low, the switching logic of the high-frequency switches is very simple, the switching logic is determined by the time sequence of the resonant cavity input voltage, and the two groups of switches S1 and S2 and S3 and S4 are kept in complementary conduction, so that the danger of two-phase direct connection can be avoided.
The AC/DC rectifying circuit 51 in FIG. 5 outputs three line voltagesu PN 、u PY Andu YN the DC/DC resonant circuit 52 implements the three-level bridge unit 521 by using a three-level I-type full bridge unit, wherein the connection P of the positive terminals (drains of S5 and S6) of the three-level bridge unit 521 is connected to the negative terminal (sources of S11 and S12) of the three-level bridge unit 521 is connected to the terminal N. Connected to terminal Y between diodes D5 and D6 and between diodes D7 and D8. Two ends of the LLC resonant unit 522 are connected between switches S7, S9 and switches S8, S10, respectively.
The input voltage to the DC/DC resonant circuit 52 is again three line voltagesu PN 、u PY Andu YN switching the voltage at high frequency S5-S12u PN 、u PY Andu YN fed to the LLC resonant unit 522, the switches S5-S12 are soft switched by means of the LLC resonant unit 522. The rectifying and filtering unit 523 is connected in parallel to the secondary winding of the transformer T.
Fig. 6 illustrates a three-level bridge unit 621 implemented by using a three-level T-type full bridge unit, wherein the positive terminal (drains of switches S13 and S14) of the three-level bridge unit 621 is connected to terminal P, and the negative terminal (sources of switches S15 and S16) of the three-level bridge unit 621 is connected to terminal N. Two terminals of the LLC resonant unit 622 are connected to terminal Y through bidirectional switches S17 and S18 and bidirectional switches S19 and S20, respectively.
The AC/DC rectifying circuit 61 outputs three line voltagesu PN 、u PY Andu YN the input voltage to the DC/DC resonant circuit 62 is again three line voltagesu PN 、u PY Andu YN switching the voltage at high frequency S13-S20u PN 、u PY Andu YN fed to the LLC resonant unit 622, the LLC resonant unit 622 is utilized to provide soft switching for high frequency switching. The rectifying and filtering unit 623 is a full-bridge rectifying and filtering unit.
The waveforms of the input voltage and the resonant current of the specific switching logic and LLC cavity are shown in FIG. 9, here againu PY Is greater thanu YN The corresponding switching cycle is taken as an example, and the corresponding working process is introduced:
1) stage 1[ t0-t1]: at time t0, switches S13 and S16 are turned on, and the LLC resonant unit 622 input voltage isu PN The inductance Lr and the capacitance Cr resonate, and the resonant currenti Lr From negative to positive. Switch S20 can be turned on at the same time at this stage because switch S19 is not turned on and its body diode direction is equal tou YN The voltage direction is the same in the opposite direction, and zero current turn-on can be achieved by turning on switch S20 at this stage. At t = DTsAt that time, switch S16 is turned off, and the forward resonant current iLr charges the junction capacitor of switch S16, discharging the junction capacitor of switch S19 until the junction capacitor voltage drops to 0, and the body diode of switch S19 turns on, providing a zero voltage turn-on condition for switch S19. In this phase, the resonant currenti Lr Flows in from the P terminal and flows out from the N terminal.
2) Stage 2[ t1-t2]: switch S19 is at zero at time t2Voltage condition is turned on, the LLC resonant unit 622 input voltage becomes uPYThe inductor Lr and the capacitor Cr continue to resonate, if the resonant current iLr is equal to the exciting currenti Lm It becomes an Lr, Lm and Cr three-element resonance. At T = TsAt time/2, S13, S19, and S20 are turned off simultaneously, and at this time, the resonant current iLr is still positive, charging the S13, S19, and S20 junction capacitances, and simultaneously discharging the junction capacitances of S15 and S14 until the capacitance voltage drops to 0, providing a zero voltage turn-on condition for S15 and S14. In this phase, a resonant current flows in from the P terminal and flows out from the Y terminal.
Stage 3[ t2-t3]And stage 4[ t3-t4]Exactly symmetrical to the input voltage of stages 1, 2 (the input voltage becomes-u PN And-u PY ) The waveform of the resonant current iLr is also positive and symmetric, the resonant current iLr changes from positive to negative, the working process is also similar, and details are not repeated here.
In each half switching period, the energy in the LLC resonant cavity can be completely transmitted to the secondary side, and the voltage waveform of the capacitor Cr is symmetrical as that of a traditional DC/DC full-bridge LLC converter, so that direct current bias can not occur.
The switching period Ts is adjusted to control the energy delivered by the LLC resonant unit to adjust the output voltage or current, and the duty cycle is adjusted to distribute the magnitude of the currents at the ends of the resonant currents iLr to P, N, Y to achieve three-phase input current power factor correction.
Referring to fig. 11, the method for controlling a three-phase single-stage power conversion device according to the present invention includes the steps of,
step T01 samples the three-phase alternating current, compares the absolute voltage values of the alternating currents of each phase, and determines that the phase in which the absolute voltage value is the maximum value is the first phase, the phase in which the absolute voltage value is the middle value is the second phase, and the phase in which the absolute voltage value is the minimum value is the third phase.
Step T02 turns off the bidirectional switch Say, Sby, or Scy corresponding to the first phase and the second phase, and turns on the bidirectional switch Say, Sby, or Scy corresponding to the third phase.
Step T03 samples the output current and adjusts the output current to generate a first reference value, which is multiplied by the input voltage of the second phase to generate a reference value for the phase input current, and adjusts the sampled value of the phase input current to generate a first duty cycle of the switches in the three-level bridge unit.
Referring to fig. 8-10, the first duty cycle is D1.
The output voltage can also be sampled and adjusted with the output voltage reference value to generate a first reference value, and the first reference value is changed according to the specific application scene.
And step T04, multiplying the first reference value by the input voltage of the first phase to generate a reference value of the input current of the phase, and adjusting the reference value and the sampled value of the input current of the phase to generate a switching period of the switching control in the three-level bridge unit.
Referring to fig. 8-10, the switching period is Ts.
And step T05, when the switching period is greater than the first set value, setting the switching period to the first set value, multiplying the input voltage of the phase corresponding to the maximum value of the input voltage by the first reference value to generate a reference value of the input current of the phase, and adjusting the reference value of the input current of the phase with the sampling value of the input current of the phase to generate a second duty ratio for switching control in the three-level bridge unit.
Referring to fig. 10, the second duty cycle is D2.
Zero voltage turn-on of all switches can be achieved. By switching the region in the power frequency period and adding the proper transition driving time sequence, the method can ensure that the interphase direct connection does not occur in the transition region and simultaneously realize better current waveform.
It should be understood that the detailed description of the present invention is only for illustrating the present invention and is not limited by the technical solutions described in the embodiments of the present invention, and those skilled in the art should understand that the present invention can be modified or substituted equally to achieve the same technical effects; and are within the scope of the present invention as long as the requirements of use are met.
Claims (14)
1. A three-phase single-stage resonant power converter is characterized by comprising,
an AC/DC rectification circuit having an input terminal to which a three-phase alternating current is connected, an output terminal including a first terminal outputting a maximum value of the three-phase alternating current in a forward direction, a second terminal outputting an intermediate value of the three-phase alternating current, and a third terminal outputting a maximum value of the three-phase alternating current in a reverse direction,
the DC/DC resonance circuit is connected with the output end of the AC/DC rectification circuit and comprises a three-level bridge unit, a resonance unit and an output rectification filter unit, wherein the input end of the three-level bridge unit is connected with a first terminal and a third terminal, the middle point of a bridge arm of the three-level bridge unit is connected with a second terminal, the input end of the resonance unit is connected with the output end of the three-level bridge unit in parallel, and the rectification filter unit is connected with the output end of the resonance unit in parallel.
2. The three-phase single-stage resonance type electric energy conversion device according to claim 1, wherein the AC/DC rectifier circuit includes a three-phase rectifier unit including an a-phase bridge arm module, a B-phase bridge arm module, and a C-phase bridge arm module, the a-phase bridge arm module, the B-phase bridge arm module, and the C-phase bridge arm module being connected in parallel, the three-phase alternating current being connected to bridge arm midpoints of the a-phase bridge arm module, the B-phase bridge arm module, and the C-phase bridge arm module, respectively, the AC/DC rectifier circuit further includes an a-phase bidirectional switch, a B-phase bidirectional switch, and a C-phase bidirectional switch, one end of the a-phase bidirectional switch, the B-phase bidirectional switch, and the C-phase bidirectional switch being connected to bridge arm midpoints of the a-phase bridge arm module, the B-phase bridge arm module, and the C-phase bridge arm module, respectively, and the other end thereof being connected in parallel to form a second terminal, and the A phase, the B phase and the C phase of the three-phase alternating current are respectively connected with the bridge arm middle points of the A-phase bridge arm module, the B-phase bridge arm module and the C-phase bridge arm module.
3. A three-phase single-stage resonance type electric energy conversion device according to claim 2, wherein said resonance unit comprises an inductor, a capacitor and a transformer, said inductor, capacitor and transformer being connected in series.
4. A three-phase single-stage resonant type power conversion device according to claim 3, wherein said three-level bridge unit is a half-bridge three-level bridge unit.
5. The apparatus of claim 3, wherein the three-level bridge unit is a full-bridge three-level bridge unit.
6. A control method of a three-phase single-stage resonance type electric energy conversion device applied to the three-phase single-stage resonance type electric energy conversion device according to any one of claims 1 to 5, comprising,
step T01 of sampling the three-phase alternating current, comparing the absolute voltage values of the alternating currents of each phase, where the phase with the maximum absolute voltage value is the first phase, the phase with the intermediate absolute voltage value is the second phase, and the phase with the minimum absolute voltage value is the third phase;
step T02 turns off the bidirectional switches connected in the first phase and the second phase, the bidirectional switches being the a-phase bidirectional switch, the B-phase bidirectional switch, and the C-phase bidirectional switch, and turns on the bidirectional switch connected in the third phase, the bidirectional switches being the a-phase bidirectional switch, the B-phase bidirectional switch, and the C-phase bidirectional switch;
step T03, sampling the output current, adjusting the output current with a reference value of the output current to generate a first reference value, multiplying the first reference value with a second phase voltage of the three-phase alternating current to generate a reference value of the phase current, and adjusting the first reference value with the sampling value of the phase current to generate a first duty ratio of a switch in the three-level bridge unit;
and step T04, multiplying the first reference value by the first phase voltage of the three-phase alternating current to generate a reference value of the phase current, and adjusting the reference value and the sampled value of the phase current to generate a switching period of the switching control in the three-level bridge unit.
7. The method of claim 6, further comprising, when the switching period is greater than a first set value at step T05, setting the switching period to the first set value, multiplying the first reference value by a first phase voltage of the three-phase ac power to generate a reference value of the phase current, and adjusting the reference value of the phase current to generate a second duty ratio for switching control in the three-level bridge unit.
8. A method of controlling a three-phase single-stage resonant-type electric power conversion apparatus as set forth in claim 6, wherein the time period by which said first duty cycle is multiplied by said switching period is a first time, the switching control period is started up until said first time, and the voltage across said resonant unit is the voltage between said first terminal and said second terminal.
9. A method of controlling a three-phase single-stage resonant type electric energy conversion device according to claim 8, wherein between the first time and one-half of the switching cycle, the voltage across the resonant unit is the voltage between the first terminal and the third terminal or the voltage between the third terminal and the second terminal.
10. The method of claim 7, wherein the time multiplied by the second duty cycle and the switching period is a second time between the first time and the second time, and the voltage across the resonant cell is a voltage between the first terminal and the third terminal or a voltage between the third terminal and the second terminal.
11. The method of claim 10, wherein the voltage across the resonant unit is zero between the second time and one-half of the switching period.
12. A method of controlling a three-phase single-stage resonant-type electric energy conversion device as set forth in claim 6, wherein the switching cycle includes a positive half cycle and a negative half cycle in which voltages across the resonant unit are symmetric in positive and negative.
13. A method of controlling a three-phase single-stage resonant-type electric energy conversion device as set forth in claim 6, wherein the switching cycle includes a positive half-cycle in which the voltage across the resonant unit has the input voltage and a negative half-cycle in which the voltage across the resonant unit is zero.
14. The method of claim 6, wherein the step T03 samples the output voltage and adjusts the sampled output voltage with a reference value of the output voltage to generate the first reference value.
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