CN113507224B - Three-phase buck-boost rectifying converter and control method - Google Patents

Three-phase buck-boost rectifying converter and control method Download PDF

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Publication number
CN113507224B
CN113507224B CN202110712490.8A CN202110712490A CN113507224B CN 113507224 B CN113507224 B CN 113507224B CN 202110712490 A CN202110712490 A CN 202110712490A CN 113507224 B CN113507224 B CN 113507224B
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phase
diode
switching tube
switching
buck
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CN113507224A (en
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李伦全
李玲
陈乾宏
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Nanchang Dudi Electronic Technology Co ltd
Shenzhen Gaoyi Intelligent Electrical Co ltd
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Nanchang Dudi Electronic Technology Co ltd
Shenzhen Gaoyi Intelligent Electrical Co ltd
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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
    • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
    • H02M7/08—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode arranged for operation in parallel
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1584—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load with a plurality of power processing stages connected in parallel
    • 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
    • H02M7/2173—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 biphase or polyphase circuit arrangement

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

Abstract

The invention discloses a three-phase buck-boost rectifier converter and a control method thereof, wherein the three-phase buck-boost rectifier converter comprises an input rectifier bridge group, a buck unit and an energy storage freewheel unit; the input rectifier bridge group comprises first to third rectifier bridges, the voltage reduction unit comprises first to eighth switching tubes and thirteenth to sixteenth diodes, and the energy storage freewheel unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth freewheel inductors and a filter capacitor. The invention has two buck switch units which can work in parallel or in parallel with each other in phase and in error, and can realize the maximum multiplexing of the input rectifier bridge group and the buck switch units in the three-phase rectifier converter by applying a 'middle' mode PWM driving signal and a 'high' mode PWM driving signal to the switch tube, thereby being applicable to the wide range of medium and high power output voltage or having the output voltage betweenMultiple times toMultiple input phase voltage ranges and where high efficiency, high power density are required.

Description

Three-phase buck-boost rectifying converter and control method
Technical Field
The application relates to the field of power electronics, in particular to a three-phase buck-boost rectifier converter and a control method.
Background
The current electric equipment is more and more in power, and the electric equipment adopting a three-phase power supply mode is more and more, if the electric equipment does not have a Power Factor Correction (PFC) function, the electric energy quality of a power grid is greatly damaged, and even the power grid is paralyzed when serious. In order to meet the power grid quality requirement, reduce harmonic pollution to the power grid or cause unnecessary conveying burden of the distribution network, three-phase electric equipment must have PFC function or increase filter device to meet the related regulation requirement.
In general, if a PFC function is required for a three-phase ac input rectifier circuit, a two-level or three-level boost type is generally used. However, after boosting, the output voltage is relatively high, and the use of the inverter or load connected to the rear end is limited, for example, the output is generally set to about 720V, even up to 800V when the nominal three-phase three-wire 380V alternating voltage is input. When the output voltage of the rear end is regulated by a converter, a conventional power tube with better performance is below 650V, and in recent years, a novel switching device such as SiC with about 1200V and the like has higher voltage and better high-frequency switching performance, but the cost is high; in order to solve the limitation of the power device of the dc converter at the back end of the rectifier converter and to consider the efficiency and other factors, the buck-type two-level rectifier converter has become a hot spot of research in recent years, such as the buck PFC of fig. 1, which needs to be subjected to a reduction process when the initial voltage is low, and the buck PFC of fig. 2, which is shown in fig. 2, can theoretically stably output a rated voltage of up to 1.5 times the peak voltage of the phase voltage if the buck PFC is adopted, and if the output required voltage exceeds the voltage range but does not reachThe back end of the phase voltage peak value is required to be additionally provided with a one-stage non-isolated DC/DC direct current conversion circuit (such as a boost scheme) to convert the phase voltage peak value into the required output voltage, and the phase voltage peak value is realized by adopting a boost or buck scheme and then performing one-stage DC/DC voltage stabilizing conversion in fig. 3, so that the two-stage scheme has higher cost, and meanwhile, the efficiency can be reduced due to the two-stage conversion.
Disclosure of Invention
The invention aims to provide a three-phase buck-boost rectifier converter and a control method, which solve the technical problems that in the prior art, a plurality of diversion channel devices are arranged, the diversion capacity of a buck switch device cannot be fully utilized, so that the loss is large, and the three-phase buck-boost rectifier converter is not suitable for being applied to places with relatively high cost requirements.
The first technical scheme adopted by the invention is as follows: a non-isolated three-phase buck-boost rectifier converter comprises an input rectifier bridge group, a buck unit and an energy storage freewheel unit; the input rectifier bridge group comprises first to third rectifier bridges, each of the first to third rectifier bridges comprises four diodes, the four diodes are respectively connected in parallel in pairs to form two bridge arm groups with the same function, the two bridge arm groups are connected in parallel to form two alternating current input ports, namely the midpoints of the two diodes in the bridge arm groups connected in series, one rectifier output positive end, namely the cathode of the bridge arm group, and one rectifier output negative end, namely the anode of the bridge arm group; the step-down unit comprises two step-down switch units, wherein the first step-down switch unit comprises first to fourth switch tubes and thirteenth to fourteenth diodes, and the second step-down switch unit comprises fifth to eighth switch tubes and fifteenth to sixteenth diodes; the first buck switch unit and the second buck switch unit share one rectifier bridge in the input rectifier bridge group; the energy storage freewheel unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth freewheel inductors and a filter capacitor; the three input rectifier bridge groups are respectively connected with any two phases in the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;
The first rectifying bridge comprises first to fourth diodes, and the rectifying output positive end of the first rectifying bridge, namely the cathodes of the first diode and the second diode, are connected with the drain electrode of the first switch tube; the negative rectification output end of the first rectification bridge, namely the anodes of the third diode and the fourth diode are connected with the source electrode of the second switching tube; the second rectifier bridge includes fifth to eighth diodes; the positive ends of the rectification output of the second rectification bridge, namely the cathodes of the fifth diode and the sixth diode are respectively connected with the anode of the thirteenth diode and the anode of the fifteenth diode; the negative rectification output end of the second rectification bridge, namely the anodes of the seventh diode and the eighth diode are respectively connected with the cathode of the fourteenth diode and the cathode of the sixteenth diode; the third rectifier bridge comprises ninth to twelfth diodes, and the positive ends of the rectification output of the third rectifier bridge, namely the cathodes of the ninth diode and the twelfth diode are connected with the drain electrode of the seventh switching tube; the negative rectification output end of the third rectification bridge, namely the anodes of the eleventh diode and the twelfth diode are connected with the source electrode of the eighth switching tube; the source electrode of the third switch tube is connected with the cathode of the thirteenth diode, one end of the first follow current inductor is respectively connected with the source electrode of the first switch tube, the source electrode of the third switch tube and the cathode of the seventeenth diode, the other end of the first follow current inductor is respectively connected with the anode of the nineteenth diode and the drain electrode of the ninth switch tube, and one end of the filter capacitor is connected with the cathode of the nineteenth diode to form a positive output end of the rectifier converter; the drain electrode of the fifth switching tube is connected with the cathode of the fifteenth diode, one end of the third follow current inductor is respectively connected with the source electrode of the fifth switching tube, the source electrode of the seventh switching tube and the cathode of the eighteenth diode, the other end of the third follow current inductor is respectively connected with the anode of the twentieth diode and the drain electrode of the tenth switching tube, and the cathode of the twentieth diode is connected with the positive output end of the rectifier converter; the source electrode of the fourth switching tube is connected with the anode of the fourteenth diode, one end of the second follow current inductor is respectively connected with the drain electrode of the second switching tube, the drain electrode of the fourth switching tube and the anode of the seventeenth diode, and the other end of the second follow current inductor is respectively connected with the source electrode of the ninth switching tube and the filter capacitor to form a negative output end of the rectifier converter; the source electrode of the sixth switching tube is connected with the anode of the sixteenth diode, one end of the fourth follow current inductor is respectively connected with the drain electrode of the sixth switching tube, the drain electrode of the eighth switching tube and the anode of the eighteenth diode, and the other end of the fourth follow current inductor is connected with the source electrode of the tenth switching tube.
Further, the first to tenth switching transistors are semiconductor devices for controlling on and off by a high-frequency driving signal, and the switching transistors have inverse parallel diodes, and the inverse parallel diodes are integrated diodes, parasitic diodes or external diodes.
Further, the filter capacitor is a nonpolar capacitor or a polar capacitor; the positive electrode of the capacitor with polarity is respectively connected with the cathode of the nineteenth diode and the cathode of the twentieth diode, and the negative electrode of the capacitor with polarity is respectively connected with the source electrode of the ninth switching tube and the source electrode of the tenth switching tube.
Further, the first flywheel inductor and the second flywheel inductor may be two separate inductors, or may be two inductors wound on the same magnetic material; the third flywheel inductor and the fourth flywheel inductor may be two separate inductors, or may be two inductors wound on the same magnetic material.
Further, the three-phase three-wire power supply also comprises an input filter, wherein the input filter is connected between the three-phase three-wire power supply and the input rectifier bridge group.
The second technical scheme adopted by the invention is as follows: a control method of a non-isolated three-phase buck-boost rectifier converter is used for controlling the non-isolated three-phase buck-boost rectifier converter according to the first technical scheme, and comprises the following steps:
s100: according to the phase lock of the input three-phase three-wire power supply voltage signal, analyzing the phase and interval section of each phase power supply at the current moment;
s200: analyzing the instantaneous value of the voltage of each phase power supply in each interval section according to the phase;
S300: applying a driving signal to the voltage reduction unit under the current interval section to perform PWM driving control so that the two-phase current with a higher instantaneous value is conducted first; switching off a switching tube on a circuit of the secondary high-phase current circuit of the conducted instantaneous value, so that the current of the phase with the highest instantaneous value and the current of the phase with the lowest instantaneous value are continuously conducted; if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switch unit path, all switch tubes in the step-down switch unit are directly turned off;
S400: when the two-phase current with higher instantaneous value is conducted, judging whether the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is larger than or equal to an output voltage set value, controlling a ninth switching tube and a tenth switching tube, and if the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is larger than or equal to the output voltage set value, the ninth switching tube or the tenth switching tube is not required to be turned on, and if the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is smaller than the output voltage set value, the ninth switching tube or the tenth switching tube is required to be turned on;
s500: all driving signals of the step-down unit are turned off, and then the energy storage freewheel unit is used for freewheel, so that each phase of current can be conducted in each switching period.
Further, the specific method of step S300 is as follows: simultaneously applying a high-mode PWM driving signal with the same duty ratio to a corresponding switching tube in a two-phase alternating current loop with the highest instantaneous value and the lowest instantaneous value, simultaneously applying a medium-mode PWM driving signal to a corresponding switching tube in a current loop with the next highest amplitude value, and turning off the switching tube applying the high-mode PWM driving signal in each interval section and turning off the switching tube applying the medium-mode PWM driving signal; and if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switching unit path, applying a PWM driving signal in a medium mode to a switching tube in the step-down switching unit.
Further, when the ninth switching tube or the tenth switching tube is in the on state, the PWM switching frequency of the ninth switching tube or the tenth switching tube coincides with the PWM switching frequencies of the first to eighth switching tubes.
Further, the first to eighth switching tubes in the first buck switching unit and the second buck switching unit work in the same frequency and the same phase or work in a phase-shifting mode according to 0-1/2 high-frequency switching period.
The invention has the beneficial effects that:
(1) The high-voltage power converter overcomes the defect of high voltage at the rear end of the traditional boost three-phase rectification conversion circuit in terms of structure and performance, avoids the complexity of multi-stage circuit conversion, reduces the limitation of a power device of a direct-current converter at the rear end, and has larger optional scope;
(2) The realization mode of the traditional step-up or step-down three-phase rectification conversion circuit is changed, the output voltage has smaller limitation compared with the alternating current input, can be step-up, step-down and even can be the voltage in the phase difference amplitude, namely the output voltage is between Multiple to/>In the input phase voltage range, the advantages are obvious in replacing the traditional passive PFC, and especially the traditional three-phase passive PFC below 30kW is replaced;
(3) The invention changes the realization channel form of the traditional buck three-phase rectification conversion circuit, has lower loop conduction impedance, and is particularly suitable for occasions with high efficiency and high power density requirements because the loop conduction impedance is only half of that of the existing known scheme under the condition of using the same switching tube in a buck mode;
(4) Because of the structural simplification, only the conduction of the output positive end or the output negative end of the buck switch unit is controlled, so that the control difficulty is reduced, and from the aspect of the switching operation of the PFC function, the control method is simplified by applying regular or logical combined PWM driving signals to the switching tube of each phase; and simultaneously, the positive and negative current loop impedance between the parallel circuits is changed by adjusting the on time of each phase of loop, so that cross loop current is avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a conventional classical buck PFC circuit;
FIG. 2 is a schematic diagram of a prior art Swiss rectifier circuit;
FIG. 3 is a schematic diagram of a prior art DC output block;
FIG. 4 is a schematic diagram of a non-isolated three-phase buck-boost rectifier converter according to embodiment 1 of the present invention;
FIG. 5 is a schematic diagram showing waveforms of three-phase voltages and definition of junction in embodiment 1 of the present invention;
FIG. 6 is a schematic diagram of an AC-BC interval AB phase conduction loop of embodiment 1 of the present invention, which is in a buck inductor energy storage mode;
FIG. 7 is a schematic diagram of the AC-O interval BC phase-sequence loop of embodiment 1 of the present invention;
FIG. 8 is a schematic diagram of an O-BC interval AC phase-sequence loop in accordance with embodiment 1 of the present invention;
FIG. 9 is a schematic diagram of an AC-BC interval inductor current freewheel loop in accordance with embodiment 1 of the present invention;
FIG. 10 is a schematic diagram of an AC-BC interval AB phase conduction loop 2 of embodiment 1 of the present invention, which is in a boost inductor energy storage mode;
FIG. 11 is a schematic diagram of the AB phase conduction loop in the AC-BC segment in embodiment 1 of the present invention, which is a boost inductor energy release mode;
FIG. 12 is an equivalent transformation schematic 1 of embodiment 1 of the present invention;
FIG. 13 is an equivalent transformation schematic diagram 2 of embodiment 1 of the present invention;
Fig. 14 is a schematic diagram showing the relationship between driving waveforms of each switch group in a three-phase ac cycle according to embodiment 1 of the present invention.
Reference numerals explain: FB1, FB2, FB3, third rectifier bridge, D1, first diode, D2, second diode, D3, third diode, D4, fourth diode, D5, fifth diode, D6, sixth diode, D7, seventh diode, D8, eighth diode d9.ninth diode, D10.tenth diode, D11.eleventh diode, D12.twelfth diode, D13.thirteenth diode, D14.fourteenth diode, D15.fifteenth diode, D16.sixteenth diode, D17.seventeenth diode an eighteenth diode, a D19 nineteenth diode, a D20 twentieth diode, a Q1 first switching tube, a Q2 second switching tube, a Q3 third switching tube, a Q4 fourth switching tube, a Q5 fifth switching tube, a Q6 sixth switching tube, a Q7 seventh switching tube, a Q8 eighth switching tube, a Q9 ninth switching tube, a Q10 tenth switching tube, a L1 first freewheeling inductor, a L2 second freewheeling inductor, a L3 third freewheeling inductor, a L4 fourth freewheeling inductor, a C1 filter capacitor, a Phase A, a Phase B, a Phase C.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than as described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements. Likewise, the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate a relative positional relationship, which changes accordingly when the absolute position of the object to be described changes.
As shown in fig. 4, a non-isolated three-phase buck-boost rectifier converter includes an input rectifier bridge set, a buck unit and an energy storage freewheel unit; the input rectifier bridge group comprises first to third rectifier bridges FB1 to FB3, wherein the first to third rectifier bridges FB1 to FB3 comprise four diodes, the four diodes are respectively connected in parallel in pairs to form two bridge arm groups with the same function, the two bridge arm groups are connected in parallel to form two alternating current input ports, namely the midpoints of the series connection of the two diodes in the bridge arm groups, one rectifier output positive end, namely the cathode of the bridge arm group, and one rectifier output negative end, namely the anode of the bridge arm group; the voltage reduction unit comprises two voltage reduction switch units, wherein the first voltage reduction switch unit comprises first to fourth switch tubes Q1 to Q4 and thirteenth to fourteenth diodes D13 to D14, and the second voltage reduction switch unit comprises fifth to eighth switch tubes Q5 to Q8 and fifteenth to sixteenth diodes D15 to D16; the first buck switch unit and the second buck switch unit share one rectifier bridge in the input rectifier bridge group; the energy storage freewheel unit comprises seventeenth to twentieth diodes D17 to D20, ninth to tenth switching tubes Q9 to Q10, first to fourth freewheel inductors L1 to L4 and a filter capacitor C1; the three input rectifier bridge groups are respectively connected with any two phases in the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;
The first rectifier bridge FB1 includes first to fourth diodes D1 to D4, and the rectifying output positive end of the first rectifier bridge FB1, that is, the cathodes of the first diode D1 and the second diode D2 are connected with the drain electrode of the first switching tube Q1; the negative rectification output end of the first rectification bridge FB1, namely the anodes of the third diode D3 and the fourth diode D4 are connected with the source electrode of the second switching tube Q2; the second rectifier bridge FB2 comprises fifth to eighth diodes D5-D8; the positive ends of the rectification output of the second rectification bridge FB2, namely the cathodes of the fifth diode D5 and the sixth diode D6 are respectively connected with the anode of the thirteenth diode D13 and the anode of the fifteenth diode D15; the negative rectification output end of the second rectification bridge FB2, namely the anodes of the seventh diode D7 and the eighth diode D8 are respectively connected with the cathode of the fourteenth diode D14 and the cathode of the sixteenth diode D16; the third rectifier bridge FB3 includes ninth to twelfth diodes D9 to D12, and the positive ends of the rectification output of the third rectifier bridge FB3, that is, the cathodes of the ninth diode D9 and the tenth diode D12 are connected with the drain electrode of the seventh switching tube Q7; the negative rectification output end of the third rectification bridge FB3, namely an eleventh diode D11 and an anode D12 of a twelfth diode are connected with the source electrode of the eighth switching tube Q8; the source electrode of the third switching tube Q3 is connected with the cathode of the thirteenth diode D13, one end of the first follow current inductor L1 is respectively connected with the source electrode of the first switching tube Q1, the source electrode of the third switching tube Q3 and the cathode of the seventeenth diode D17, the other end of the first follow current inductor L1 is respectively connected with the anode of the nineteenth diode D19 and the drain electrode of the ninth switching tube Q9, and one end of the filter capacitor C1 is connected with the cathode of the nineteenth diode D19 to form a positive output end of the rectifier converter; the drain electrode of the fifth switching tube Q5 is connected with the cathode of the fifteenth diode D15, one end of the third follow current inductor L3 is respectively connected with the source electrode of the fifth switching tube Q5, the source electrode of the seventh switching tube Q7 and the cathode of the eighteenth diode D18, the other end of the third follow current inductor L3 is respectively connected with the anode of the twentieth diode D20 and the drain electrode of the tenth switching tube Q10, and the cathode of the twentieth diode D20 is connected with the positive output end of the rectifier converter; the source electrode of the fourth switching tube Q4 is connected with the anode of the fourteenth diode D14, one end of the second follow current inductor L2 is respectively connected with the drain electrode of the second switching tube Q2, the drain electrode of the fourth switching tube Q4 and the anode of the seventeenth diode D17, and the other end of the second follow current inductor L2 is respectively connected with the source electrode of the ninth switching tube Q9 and the filter capacitor C1 to form a negative output end of the rectifier converter; the source electrode of the sixth switching tube Q6 is connected to the anode electrode of the sixteenth diode D16, one end of the fourth freewheeling inductor L4 is connected to the drain electrode of the sixth switching tube Q6, the drain electrode of the eighth switching tube Q8, and the anode electrode of the eighteenth diode D18, respectively, and the other end is connected to the source electrode of the tenth switching tube Q10.
In the embodiment of the present invention, the first ac input port of the first rectifier bridge FB1, that is, the anode of the first diode D1 is connected to the a of the three-phase three-wire power supply; the anode of a second alternating current input port of the first rectifier bridge FB1, namely a second diode D2 is connected with the phase B of the three-phase three-wire power supply; the anode of the fifth diode D5, which is the first alternating current input port of the second rectifier bridge FB2, is connected with the phase B of the three-phase three-wire power supply; the anode of a second alternating current input port of the second rectifier bridge FB2, namely a sixth diode D6 is connected with the C phase of the three-phase three-wire power supply; the anode of the ninth diode D9, which is the first alternating current input port of the third rectifier bridge FB3, is connected with the A phase of the three-phase three-wire power supply; the anode of the twelfth pole tube D10, which is the second alternating current input port of the third rectifier bridge FB3, is connected with the C phase of the three-phase three-wire power supply; the first buck switching unit and the second buck switching unit share a second rectifier bridge FB2; the first freewheeling inductor L1 and the second freewheeling inductor L2 may be two separate inductors, or may be two inductors wound on the same magnetic material; the third freewheeling inductor L3 and the fourth freewheeling inductor L4 may be two separate inductors or two inductors wound on the same magnetic material; the filter capacitor C1 is a nonpolar capacitor or a polar capacitor; if the filter capacitor C1 is a capacitor with a polarity, the positive electrode of the filter capacitor C1 is connected to the cathode of the nineteenth diode D19 and the cathode of the twentieth diode D20, respectively, and the negative electrode is connected to the source of the ninth switching tube Q9 and the source of the tenth switching tube Q10, respectively. The embodiment of the invention also comprises an input filter, wherein the input filter is connected between the three-phase three-wire power supply and the input rectifier bridge group, and can filter the input power supply and filter and attenuate internal clutter reflected to an input end. The first to tenth switching transistors Q1 to Q10 may be MOS transistors, IGBT transistors, or the like, and those skilled in the art should understand that the present invention is not limited to the above two semiconductor power switches, but may be other power devices capable of performing high frequency switching operations. An independent driving power supply is used between the first switching tube Q1 to the tenth switching tube Q10, the first switching tube Q1 and the third switching tube Q3 can share one driving power supply, and the fifth switching tube Q5 or the seventh switching tube Q7 can share one driving power supply.
The control method adopted by the embodiment of the invention is as follows: a control method of a non-isolated three-phase buck-boost rectifier converter comprises the following steps:
s100: according to the phase lock of the input three-phase three-wire power supply voltage signal, analyzing the phase and interval section of each phase power supply at the current moment;
s200: analyzing the instantaneous value of the voltage of each phase power supply in each interval section according to the phase;
S300: applying a driving signal to the voltage reduction unit under the current interval section to perform PWM driving control so that the two-phase current with a higher instantaneous value is conducted first; switching off a switching tube on a circuit of the secondary high-phase current circuit of the conducted instantaneous value, so that the current of the phase with the highest instantaneous value and the current of the phase with the lowest instantaneous value are continuously conducted; if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switch unit path, all switch tubes in the step-down switch unit are directly turned off; the specific method comprises the following steps: simultaneously applying a high-mode PWM driving signal with the same duty ratio to a corresponding switching tube in a two-phase alternating current loop with the highest instantaneous value and the lowest instantaneous value, simultaneously applying a medium-mode PWM driving signal to a corresponding switching tube in a current loop with the next highest amplitude value, and turning off the switching tube applying the high-mode PWM driving signal in each interval section and turning off the switching tube applying the medium-mode PWM driving signal; if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switching unit path, a 'medium' mode PWM driving signal is applied to a switching tube in the step-down switching unit;
S400: when the two-phase current with higher instantaneous value is conducted, judging whether the maximum value of the inter-phase instantaneous value voltage difference of the conducted two phases is larger than or equal to an output voltage set value, controlling a ninth switching tube Q9 and a tenth switching tube Q10, and if the maximum value is larger than or equal to the output voltage set value, the ninth switching tube Q9 or the tenth switching tube Q10 is not required to be turned on, and if the maximum value is smaller than the output voltage set value, the ninth switching tube Q9 or the tenth switching tube Q10 is required to be turned on; when the ninth switching tube Q9 or the tenth switching tube Q10 is in an on state, the PWM switching frequency of the ninth switching tube Q9 or the tenth switching tube Q10 is consistent with the PWM switching frequencies of the first to eighth switching tubes Q1-Q8;
s500: all driving signals of the step-down unit are turned off, and then the energy storage freewheel unit is used for freewheel, so that each phase of current can be conducted in each switching period.
The method for judging the magnitude of the instantaneous value is to compare the absolute value magnitude of the instantaneous value of each phase. The first to tenth switching tubes Q1 to Q10 in the first step-down switching unit and the second step-down switching unit work in the same frequency and the same phase or work in a phase-shifting mode according to 0 to 1/2 high-frequency switching period. In the embodiment of the invention, the first to tenth switching tubes Q1 to Q10 in the first buck switching unit and the second buck switching unit operate in a phase-shifting manner according to 1/2 of the high-frequency switching period, and are the optimal values.
As shown in fig. 5, the input three-Phase ac power includes an a-Phase input Phase a, a B-Phase input Phase B, and a C-Phase input Phase C. For convenience of description, three-phase voltages are set to be 120 DEG different and sinusoidal, and each 360 DEG is circulated; in view of visual convenience of expression, the points of 30 degrees to 390 degrees, namely 30 degrees of the next period are taken as a complete period, and each intersection point is respectively defined as AC (30 degrees), BC (90 degrees), BA (150 degrees), CA (210 degrees), CB (270 degrees), AB (330 degrees), AC (30 degrees or 390 degrees); zero crossings are marked as "0" points.
As shown in fig. 4, a load or a circuit equivalent to a load may be connected between the positive output terminal and the negative output terminal. According to the basic principle of circuit voltage reduction, the output voltage should be lower than the input voltage to form voltage reduction. Therefore, in the embodiment of the present invention, the two phases with the largest instantaneous values form the opposite output ends of the conduction, and the 0 ° or origin of the a phase in fig. 5 is used as a reference, and the lowest point of the instantaneous difference of the voltage difference should be the 30 °, 90 °, 150 °, 210 °, 270 °, 330 ° points of the a phase, or similar periodic phase difference relation points, where the lowest value is 1+1/2 times of the highest amplitude of the phase voltage; the highest point of the instantaneous difference of the voltage difference is 60 DEG, 120 DEG, 180 DEG, 240 DEG, 300 DEG, 360 DEG of the A phase, or the similar periodic phase difference relation point, and the highest value isThe highest amplitude of the phase voltage is multiplied. When the output voltage is set to be less than/>WhereinThe effective value of the phase voltage is smaller than the minimum voltage difference value of any time between two phases of the three-phase voltage, and the output working state of the embodiment of the invention is in a full-step-down mode. When the output voltage setting is greater than/>The output working state of the embodiment of the invention is a boost mode, which is higher than the maximum voltage difference between the three-phase voltage and the two phases at any time. When the output voltage is between/>In the working mode of the embodiment of the invention, both the voltage boosting and the voltage reducing are carried out.
(1) Determining a buck mode based on output voltage demand
As shown in fig. 6, in the AC-BC interval from the AC point to the BC point, the absolute value of the instantaneous value of the a-phase and B-phase voltages is higher than that of the C-phase, so that the internal positive-side diodes of the first rectifier bridge FB1 and the third rectifier bridge FB3 connected to the a-phase, that is, the first diode D1 and the ninth diode D9 are turned on by the forward bias voltage, the voltage is denoted as Va, and the internal negative-side diodes of the first rectifier bridge FB1 and the second rectifier bridge FB2 of the rectifier bridge group connected to the B-phase, that is, the fourth diode D4 and the seventh diode D7 are turned on by the forward bias voltage, the voltage is denoted as Vb; the internal diodes of the second rectifier bridge FB2 and the third rectifier bridge FB3 connected to C are reverse biased by the voltages Va and Vb and cannot be turned on, the cathode voltage of the twelfth diode D10 is clamped Va, and the anode voltage of the eighth diode D8 is clamped Vb. When the PWM driving on signals are applied to the first to fourth switching tubes Q1 to Q4 or the fifth to eighth switching tubes Q5 to Q8 at the same time, the corresponding switching tubes of the Q first to fourth switching tubes Q1 to Q4 or the fifth to eighth switching tubes Q5 to Q8 are turned on. The current of the A phase can flow through the first freewheeling inductor L1, the nineteenth diode D19, the filter capacitor C1 and the second freewheeling inductor L2 through the first diode D1 and the first switching tube Q1, and returns to the B freewheeling source through the branch formed by the second switching tube Q2 and the fourth diode D4 or the branch formed by the fourth switching tube Q4, the fourteenth diode 4 and the seventh diode D7; the current of the phase a can also flow through the ninth diode D9 and the seventh switching tube Q7, through the third freewheeling inductor L3, the twentieth diode D20 and the filter capacitor C1, and back to the B-phase current source through the fourth freewheeling inductor L4, the sixth switching tube Q6, the sixteenth diode D16 and the seventh diode D7. At this time, two buck through-current loops of the first buck switch unit and the second buck switch unit are provided, and the two buck switch units share the second rectifier bridge FB2 where the B phase is located as a current loop.
As shown in fig. 7, in the AC-0 interval, after the driving of the first switching tube Q1 and the seventh switching tube Q7 is turned off; at this time, the current loop of the first buck switch unit has the first freewheeling inductor L1 and the second freewheeling inductor L2, so that the current cannot immediately reverse, the inductance electromotive force can reverse and freewheel, and the current loop is conducted with the sixth diode D6 and the thirteenth diode D13 under the forward bias voltage. Since the third switching tube Q3 is always turned on by the on driving signal, the current flows from the C-phase through the sixth diode D6, the thirteenth diode D13 and the third switching tube Q5, through the first freewheeling inductor L1, the nineteenth diode D19, the filter capacitor C1 and the second freewheeling inductor L2, and returns to the B-phase freewheeling source through the branch formed by the second switching tube Q2 and the fourth diode D4 or the branch formed by the fourth switching tube Q4, the fourteenth diode D14 and the seventh diode D7. The third freewheeling inductor L3 and the fourth freewheeling inductor L4 are arranged in the through-flow loop of the second buck switching unit, so that the freewheeling can not happen immediately, the inductance electromotive force can be reversed and can not be conducted by the reverse bias of the A-phase voltage, the sixth diode D6 and the fifteenth diode D15 are conducted by the forward bias voltage, the fifth switching tube Q5 is conducted all the time due to the turn-on driving signal, the current flows through the third freewheeling inductor L3, the twenty-second diode D20, the filter capacitor C1 and the fourth freewheeling inductor L4 from the C-phase through the sixth diode D6, the twenty-second diode D16 and the seventh diode D7 to the B-phase intersecting current source, and the first buck switching unit and the second buck switching unit share the second rectifier bridge 2 where the C-phase is located as a necessary current return path at the moment.
As shown in fig. 8, in the interval 0-BC, after the driving signals of the fifth to sixth switching tubes Q5 to Q6 are turned off, the current is not immediately reversed due to the third freewheeling inductor L3 and the fourth freewheeling inductor L4 in the second buck switching unit loop, the electromotive force of the inductor is reversed and freewheels, and meanwhile the twelfth diode D12 is turned on by the forward bias voltage, and the seventh switching tube Q7 and the eighth switching tube Q8 are always turned on by the on driving signals, so that the current flows from the a phase through the ninth diode D9 and the seventh switching tube Q7, flows through the third freewheeling inductor L3, the twentieth diode D20, the filter capacitor C1 and the fourth freewheeling diode L4, and returns to the C-phase intersecting current source through the eighth switching tube Q8 and the twelfth diode D12. The first buck switch unit is B, C in the same direction, and the instantaneous value of the C phase is smaller than that of the B phase, so that the eighth diode D8 is reverse biased and cannot be turned on, at this time, the first to fourth switch tubes Q1 to Q4 cannot apply the on driving signal any more, but the first freewheeling inductor L1 and the second freewheeling inductor L2 exist in the loop, the electromotive force of the inductor is reversed, so that the seventeenth diode D17 is reverse biased, and the current flows through the loop formed by the second freewheeling inductor L2, the seventeenth diode D17, the first freewheeling inductor L1 and the nineteenth diode D19.
From the above, it can be seen that the current can be conducted by each phase in each switching period, so that the key of achieving high PF value and low THDI is that two phases with higher instantaneous value and opposite polarity are conducted first, energy is stored in the inductance of the loop, and then the switching tube in the conduction loop of the next highest phase with absolute value of the instantaneous value is turned off, so that the freewheeling current passes through the lowest phase of the instantaneous value; if the two phase power sources are of the same polarity and are connected to the same input rectifier bridge group, i.e. share the same switching circuit, the rectifier bridge diode of the lowest instantaneous phase will be reverse biased and will not conduct. Therefore, in each switching period, the current loop with the instantaneous value of the next highest phase is turned off first, the PWM driving mode of the switching tube turned off first is marked as 'middle', and the PWM driving mode of the switching tube turned off later is marked as 'high'. Although the switching tube driving of the lowest instantaneous value phase can also apply a PWM driving signal in a high mode, the switching tube needs to be turned on after the PWM driving signal in a medium mode is turned off, and the PWM driving mode can be called a low mode. Therefore, in the actual control of this embodiment, although the duty ratio of the switching tube on may be three, the PWM driving of each period normally has two values to satisfy the control.
As shown in fig. 9, when all PWM on voltages applied to the switching tube are turned off, all current loops input after the switching tube is turned off are cut off, and the first freewheeling inductor L1, the second freewheeling inductor L2, the third freewheeling inductor L3 and the fourth freewheeling inductor L4 must keep freewheeling due to the fact that the current of the inductor cannot be transient, so the seventeenth diode D17 and the eighteenth diode D18 will be biased to be turned on by the forward voltage, respectively. The current can be returned to the positive end of the filter capacitor C1 or the equivalent load positive end of the circuit output end by the negative end of the filter capacitor C1 through a branch formed by the second freewheeling inductor L2, the seventeenth diode D17, the first freewheeling inductor L1 and the nineteenth diode D19 or a branch formed by the fourth freewheeling inductor L4, the eighteenth diode D18, the third freewheeling inductor L3 and the twentieth diode D20 to form a current freewheeling loop, so that energy storage in the inductor is released, and the conversion state of one switching cycle of the rectifier converter is completed.
According to the above working principle of the embodiment of the present invention, in the step-down unit, in the same switching period, the driving signal mode in which the PWM driving signal of the switching tube on the turn-on loop is turned off first is denoted as "middle", and the PWM driving signal mode in which the PWM driving signal is turned off later is denoted as "high". In each switching period, the control method firstly conducts two phases with relatively higher instantaneous values and opposite polarities, the inductance of the conducting loop generates voltage drop and energy storage, and then switches off the switching tube in the path with the next highest instantaneous value, so that the follow current passes through the lowest absolute value phase of the instantaneous value. Meanwhile, as the two-phase power supplies have the same polarity and are connected to the same input rectifier bridge group and share the same step-down switch unit loop, the diode of the input rectifier bridge group connected with the lowest phase of the instantaneous value is reversely biased and cannot be conducted, and meanwhile, the step-down switch unit has no other paths for conducting the phase, and under the condition of the state, the corresponding switch tube in the step-down switch unit must be turned off. If the duty ratio of the PWM driving signal is modulated according to real-time control, the current waveform and the voltage waveform are consistent, so that a higher PF value can be obtained, namely, the PFC correction function is realized.
In addition, when the control complexity is not considered and the same effect needs to be achieved, another control mode may be adopted, wherein a driving signal is not simultaneously applied to the switching tubes of each step-down loop, a signal is firstly applied to two phases with higher instantaneous values and opposite polarities to conduct the switching tubes, then the switch of the current path with the instantaneous value next highest phase in the two phases being conducted is turned off, a driving signal is applied to the switching tube on the lowest intersection loop of the instantaneous values to conduct the switching tubes, so that the follow current passes through the lowest phase of the instantaneous values, and then the switching tubes in the step-down switching units are controlled to be turned off. Therefore, in each switching period, the current loop of the higher phase with the same amplitude is turned off first, the PWM driving signal mode turned off first is marked as "middle", the PWM driving signal mode turned on later is marked as "low", and the PWM driving signal mode turned on first and turned off last is marked as "high". This approach does not depart from our previous "high" and "medium" control strategy and will not be described in detail below.
(2) Determining boost mode based on output voltage demand
In addition to the first to fourth switching tubes Q1 to Q4 and the fifth to eighth switching tubes Q5 to Q8 being driven correspondingly according to the driving control manner shown in fig. 14, PWM driving needs to be applied to the ninth switching tube Q9 and the tenth switching tube Q10, and when the ninth switching tube Q9 and the tenth switching tube Q10 are turned on, the input current is directly shorted by the ninth switching tube Q9 or the tenth switching tube Q10 to form a reflux loop. As shown in fig. 10, the voltage of the ac source is applied to the first and second freewheeling inductors L1 and L2, and the third and fourth freewheeling inductors L3 and L4, respectively, so that the inductance stores energy. As shown in fig. 11, when the driving of the ninth switching transistor Q9 and the tenth switching transistor Q10 is turned off, the current cannot be reversed due to the first freewheeling inductor L1, the second freewheeling inductor L2, the third freewheeling inductor L3 and the fourth freewheeling inductor L4, and the current continues to remain in the original direction, so that the electromotive force of the inductor is reversed, and the electromotive force is connected in series with the input voltage to supply power to the output or load terminal.
According to the analysis of the working principle, the equivalent transformation of the circuit in each working mode can be carried out. The method is characterized in that the method comprises the steps of simplifying the diagram of fig. 4 according to symmetry and switching functionality to obtain the diagram of fig. 12, rectifying an alternating current source through a diode under a transient condition to be equivalent to a direct current source, or the alternating current source and the diode can be regarded as a direct current source in an instantaneous circuit; meanwhile, the combined switch tube in the alternating current loop can be simplified and equivalent to one switch, so that fig. 12 can be further simplified into fig. 13. After the circuit of the embodiment of the invention is equivalent, the circuit can be actually regarded as a step-up/step-down circuit, so that the circuit has typical step-down function and step-up function. Considering the conduction loss of devices in a circuit, the loss of the duty ratio conduction angle such as dead zone, driving delay and the like and the necessary power factor correction function, compared with the traditional two-stage conversion mode, the amplitude range of the output voltage of the embodiment of the invention is optimally equal to the effective value of the input three-phase voltageThe ratio may slightly exceed this range.
For other intervals, the control method is similar to that of the AC-BC interval, if two phase power supplies have the same polarity and are connected to the same input rectifier bridge group, and share the same step-down switch unit loop, the rectifier bridge diode with the lowest instantaneous value is reversely biased and cannot be conducted, meanwhile, the step-down switch unit has no other paths to conduct the phase current, under the condition of the state, the corresponding switch tube in the step-down switch unit is turned off, and at the moment, the corresponding switch tube can only apply a 'medium' PWM driving signal.
For the BC-BA interval, in the BC-0 interval, the driving signal of the switching tube of the A, B two-phase current path is a high-mode PWM driving signal, and the driving signal of the switching tube of the C-phase current path is a middle-mode PWM driving signal, namely, the C-phase loop is firstly turned off; in the interval of 0-BA, the driving signal of the switching tube of C, B two-phase current paths is a 'high' mode PWM driving signal, and the driving signal of the switching tube of A-phase current paths is a 'medium' mode PWM driving signal, namely the A-phase loop is turned off first.
For the BA-CA interval, in the BA-0 interval, the driving signal of the switching tube of the A, C two-phase current path is a 'high' mode PWM driving signal, and the driving signal of the switching tube of the B-phase current path is a 'medium' mode PWM driving signal, namely, the B-phase loop is firstly turned off; in the interval 0-CA, the driving signal of the switching tube of A, B two-phase current paths is a 'high' mode PWM driving signal, and the driving signal of the switching tube of C-phase current paths is a 'medium' mode PWM driving signal, namely, the C-phase loop is firstly turned off.
For the CA-CB interval, in the CA-0 interval, the driving signal of the switching tube of the B, C two-phase current path is a 'high' mode PWM driving signal, and the driving signal of the switching tube of the A-phase current path is a 'medium' mode PWM driving signal, namely, the A-phase loop is firstly turned off; in the 0-CB interval, the driving signal of the switching tube of the A, C two-phase current path is a 'high' mode PWM driving signal, and the driving signal of the switching tube of the B-phase current path is a 'medium' mode PWM driving signal, namely the B-phase loop is firstly turned off.
For the CB-AB section, in the CB-0 section, the driving signal of the switching tube of the B, A two-phase current path is a high-mode PWM driving signal, and the driving signal of the switching tube of the C-phase current path is a medium-mode PWM driving signal, namely, the C-phase loop is firstly turned off; in the 0-AB interval, the driving signal of the switching tube of the B, C two-phase current path is a 'high' mode PWM driving signal, and the driving signal of the switching tube of the A-phase current path is a 'medium' mode PWM driving signal, namely the A-phase loop is firstly turned off.
For the AB-AC interval, in the AB-0 interval, the driving signal of the switching tube of the C, A two-phase current path is a 'high' mode PWM driving signal, and the driving signal of the switching tube of the B-phase current path is a 'medium' mode PWM driving signal, namely, the B-phase loop is firstly turned off; in the 0-AC interval, the driving signal of the switching tube of B, A two-phase current paths is a 'high' mode PWM driving signal, and the driving signal of the switching tube of C-phase current paths is a 'medium' mode PWM driving signal, namely, the C-phase loop is firstly turned off.
In reality, the three-phase voltage is not necessarily completely ideal, and the phase, amplitude and direction changes only can judge and generate the driving waveform of each section according to the actual phase lock, so the driving waveform of each section should be judged according to the characteristics of the instantaneous waveform of each alternating-current voltage of each section, but not by an ideal angle, and the driving waveform of each switching tube driving signal can be divided into twelve sections according to the characteristics of the three-phase power signal, and the waveform logic table of the twelve sections according to the principle is shown in table 1.
Table 1 switching tube driving state logic table
The "low" mode means that the same drive signal as the switching tube of the maximum instantaneous value can be applied according to the control method described above, or the drive signal constituting the freewheel can be applied to the switching tube of the other phase in the same direction as the instantaneous value before the drive signal of the switching tube of the maximum instantaneous value is turned off at the latest, and the duty ratio is recorded as "high-medium". The "low 1" mode indicates that no driving signal needs to be applied or a signal of an arbitrary duty ratio can be applied during the maximum instantaneous value phase of the morning switch tube conduction; therefore, in view of simplification and normalization of control, the "low" and "low 1" modes are regularized into the following driving signals on the basis of not affecting the function implementation. At this time, table 1 can be simplified into a switching tube driving state logic table as shown in table 2:
table 2 simplified switching tube drive state logic table
According to the availability of each interval section of the driving waveform logic table, the following control method can be executed:
Detecting input alternating voltage, judging whether various indexes of the input voltage meet working conditions, and continuing waiting if the indexes of the input voltage do not meet the working conditions; if the condition is met, starting to work, and analyzing the phase and the interval section of each phase of power supply at the current moment according to the phase locking judgment of the input three-phase three-wire power supply voltage signal; the absolute value of the instantaneous value of the voltage of each phase of power supply is analyzed, and whether the embodiment of the invention works in a boosting mode or a step-down mode is judged according to the instantaneous value of the voltage of the input phase and the set value of the output voltage. If the voltage boosting mode is adopted, PWM driving is required to be applied according to the operation result to turn on a ninth switching tube Q9 or a tenth switching tube Q10; otherwise, the voltage is reduced, and the ninth switching tube Q9 or the tenth switching tube Q10 is not required to be turned on. If two phase power supplies have the same polarity and are connected to the same rectifier bridge, and share the same step-down switching unit loop, the rectifier bridge diode of the lowest instantaneous value phase is reversely biased and cannot be conducted, meanwhile, the step-down switching unit has no other paths for conducting the phase current, under the condition of the state, the corresponding switching tube in the step-down switching unit is turned off, and at the moment, the corresponding switching tube can only apply a 'medium' PWM driving signal; and applying a 'medium' mode PWM driving signal to a corresponding switching tube in a current loop of the absolute value of the instantaneous value of the second highest phase, and applying 'high' mode PWM driving signals with the same duty ratio to the rest switching tubes. The two-phase power supply with higher instantaneous value forms a current path, meanwhile, boosting energy storage or partial pressure energy storage is formed on the inductance of the energy storage freewheel unit, after the PWM driving signal in the 'middle' mode is turned off, the switching tube of the other two phases of the PWM driving signal in the 'high' mode is originally applied to provide a freewheel path for the inductance to be continuously conducted, if the switching tube is in the boosting mode, after the boosting switching tube is turned off, the electromotive force of the inductance is reversely connected in series with the input voltage to enter the energy release freewheel mode. The specific duty ratio of the PWM driving signals in the high mode and the medium mode is determined by the real-time control operation result of the controller. When the driving of all the switching tubes is turned off, the inductance electromotive force is reversed, and the inductance current is freewheeled by the seventeenth diode D17 or the eighteenth diode D18 to form a path. In general, the time at which each phase inputs on-current is relative to the instantaneous value of the phase voltage, i.e., the higher the instantaneous value, the longer the on-time, the greater the duty cycle, the current on-time for the phase with the largest instantaneous value is equal to the sum of the current on-times for the other two phases with the relatively lower instantaneous value and less than the total time of the switching cycle, and the associated waveform drive is as shown in fig. 14.
Through the control method, the three phases are effectively guaranteed to have current flowing in each switching period, meanwhile, the duty ratio of the PWM driving signal is modulated according to real-time control, so that the current waveform and the voltage waveform are consistent in follow-up, a higher PF value can be obtained, and the PFC correction function is realized.
In the embodiment of the invention, two buck switch unit paths exist, and each buck switch unit can independently realize power conversion, so that the two buck switch units can work in the same frequency and in the same phase or in a staggered phase according to 0-1/2 high-frequency switch period; according to the total ripple of the input current and the comprehensive characteristics of the system, the staggered working mode of 1/2 high-frequency switching cycles is the optimal working mode of the embodiment of the invention, namely, the switching tube driving of the first to fourth switching tubes Q1 to Q4 or the fifth to eighth switching tubes Q5 to Q8 is staggered by 1/2 switching cycles. Because the current of the alternating current input end can form staggered parallel connection, the alternating current input current can be more easy to achieve continuity, the defect of intermittent input current of the step-down power supply is overcome, and meanwhile, the input filter and the EMI interference can be reduced.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. The non-isolated three-phase buck-boost rectifier converter is characterized by comprising an input rectifier bridge group, a buck unit and an energy storage freewheel unit; the input rectifier bridge group comprises first to third rectifier bridges, each of the first to third rectifier bridges comprises four diodes, the four diodes are respectively connected in parallel in pairs to form two bridge arm groups with the same function, the two bridge arm groups are connected in parallel to form two alternating current input ports, namely the midpoints of the two diodes in the bridge arm groups connected in series, one rectifier output positive end, namely the cathode of the bridge arm group, and one rectifier output negative end, namely the anode of the bridge arm group; the step-down unit comprises two step-down switch units, wherein the first step-down switch unit comprises first to fourth switch tubes and thirteenth to fourteenth diodes, and the second step-down switch unit comprises fifth to eighth switch tubes and fifteenth to sixteenth diodes; the first buck switch unit and the second buck switch unit share one rectifier bridge in the input rectifier bridge group; the energy storage freewheel unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth freewheel inductors and a filter capacitor; the three input rectifier bridge groups are respectively connected with any two phases in the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;
The first rectifying bridge comprises first to fourth diodes, and the rectifying output positive end of the first rectifying bridge, namely the cathodes of the first diode and the second diode, are connected with the drain electrode of the first switch tube; the negative rectification output end of the first rectification bridge, namely the anodes of the third diode and the fourth diode are connected with the source electrode of the second switching tube; the second rectifier bridge includes fifth to eighth diodes; the positive ends of the rectification output of the second rectification bridge, namely the cathodes of the fifth diode and the sixth diode are respectively connected with the anode of the thirteenth diode and the anode of the fifteenth diode; the negative rectification output end of the second rectification bridge, namely the anodes of the seventh diode and the eighth diode are respectively connected with the cathode of the fourteenth diode and the cathode of the sixteenth diode; the third rectifier bridge comprises ninth to twelfth diodes, and the positive ends of the rectification output of the third rectifier bridge, namely the cathodes of the ninth diode and the twelfth diode are connected with the drain electrode of the seventh switching tube; the negative rectification output end of the third rectification bridge, namely the anodes of the eleventh diode and the twelfth diode are connected with the source electrode of the eighth switching tube; the source electrode of the third switch tube is connected with the cathode of the thirteenth diode, one end of the first follow current inductor is respectively connected with the source electrode of the first switch tube, the source electrode of the third switch tube and the cathode of the seventeenth diode, the other end of the first follow current inductor is respectively connected with the anode of the nineteenth diode and the drain electrode of the ninth switch tube, and one end of the filter capacitor is connected with the cathode of the nineteenth diode to form a positive output end of the rectifier converter; the drain electrode of the fifth switching tube is connected with the cathode of the fifteenth diode, one end of the third follow current inductor is respectively connected with the source electrode of the fifth switching tube, the source electrode of the seventh switching tube and the cathode of the eighteenth diode, the other end of the third follow current inductor is respectively connected with the anode of the twentieth diode and the drain electrode of the tenth switching tube, and the cathode of the twentieth diode is connected with the positive output end of the rectifier converter; the source electrode of the fourth switching tube is connected with the anode of the fourteenth diode, one end of the second follow current inductor is respectively connected with the drain electrode of the second switching tube, the drain electrode of the fourth switching tube and the anode of the seventeenth diode, and the other end of the second follow current inductor is respectively connected with the source electrode of the ninth switching tube and the filter capacitor to form a negative output end of the rectifier converter; the source electrode of the sixth switching tube is connected with the anode of the sixteenth diode, one end of the fourth follow current inductor is respectively connected with the drain electrode of the sixth switching tube, the drain electrode of the eighth switching tube and the anode of the eighteenth diode, and the other end of the fourth follow current inductor is connected with the source electrode of the tenth switching tube.
2. The non-isolated three-phase buck-boost rectifier converter of claim 1 wherein the first through tenth switching tubes are semiconductor devices that are controlled by a high frequency drive signal to turn on and off, and the switching tubes have anti-parallel diodes that are integrated diodes, parasitic diodes, or external diodes.
3. The non-isolated three-phase buck-boost rectifier converter of claim 1 wherein the filter capacitor is a non-polar capacitor or a polar capacitor; the positive electrode of the capacitor with polarity is respectively connected with the cathode of the nineteenth diode and the cathode of the twentieth diode, and the negative electrode of the capacitor with polarity is respectively connected with the source electrode of the ninth switching tube and the source electrode of the tenth switching tube.
4. The non-isolated three-phase buck-boost rectifier converter of claim 1, wherein the first freewheeling inductor and the second freewheeling inductor are two separate inductors or two inductors wound on the same magnetic material; the third flywheel inductor and the fourth flywheel inductor are two independent inductors or two inductors wound on the same magnetic material.
5. The non-isolated three-phase buck-boost rectifier converter of claim 1 further including an input filter coupled between the three-phase three-wire power supply and the input rectifier bridge bank.
6. A control method of a non-isolated three-phase buck-boost rectifier converter, which is characterized by being used for controlling the non-isolated three-phase buck-boost rectifier converter according to any one of claims 1-5, and comprising the following steps:
s100: according to the phase lock of the input three-phase three-wire power supply voltage signal, analyzing the phase and interval section of each phase power supply at the current moment;
s200: analyzing the instantaneous value of the voltage of each phase power supply in each interval section according to the phase;
S300: applying a driving signal to the voltage reduction unit under the current interval section to perform PWM driving control so that the two-phase current with a higher instantaneous value is conducted first; switching off a switching tube on a circuit of the secondary high-phase current circuit of the conducted instantaneous value, so that the current of the phase with the highest instantaneous value and the current of the phase with the lowest instantaneous value are continuously conducted; if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switch unit path, all switch tubes in the step-down switch unit are directly turned off;
S400: when the two-phase current with higher instantaneous value is conducted, judging whether the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is larger than or equal to an output voltage set value, controlling a ninth switching tube and a tenth switching tube, and if the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is larger than or equal to the output voltage set value, the ninth switching tube or the tenth switching tube is not required to be turned on, and if the maximum value of the inter-phase instantaneous value voltage difference of the conducted two-phase is smaller than the output voltage set value, the ninth switching tube or the tenth switching tube is required to be turned on;
s500: all driving signals of the step-down unit are turned off, and then the energy storage freewheel unit is used for freewheel, so that each phase of current can be conducted in each switching period.
7. The method of the non-isolated three-phase buck-boost rectifier converter of claim 6, wherein the specific method of step S300 is as follows: simultaneously applying a high-mode PWM driving signal with the same duty ratio to a corresponding switching tube in a two-phase alternating current loop with the highest instantaneous value and the lowest instantaneous value, simultaneously applying a medium-mode PWM driving signal to a corresponding switching tube in a current loop with the next highest amplitude value, and turning off the switching tube applying the high-mode PWM driving signal in each interval section and turning off the switching tube applying the medium-mode PWM driving signal; and if the amplitude directions of the lowest instantaneous value phase and the second highest instantaneous value phase are the same and share one step-down switching unit path, applying a PWM driving signal in a medium mode to a switching tube in the step-down switching unit.
8. The method according to claim 6, wherein when the ninth switching tube or the tenth switching tube is in an on state, a PWM switching frequency of the ninth switching tube or the tenth switching tube is identical to PWM switching frequencies of the first to eighth switching tubes.
9. The method for controlling a non-isolated three-phase buck-boost rectifier according to claim 6, wherein the first to eighth switching tubes of the first buck switching unit and the second buck switching unit operate in the same frequency and in the same phase or in a phase-shifting manner according to 0-1/2 of the high frequency switching cycles.
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