CN113507224A

CN113507224A - Three-phase buck-boost rectifier converter and control method

Info

Publication number: CN113507224A
Application number: CN202110712490.8A
Authority: CN
Inventors: 李伦全; 李玲; 陈乾宏
Original assignee: Nanchang Dudi Electronic Technology Co ltd; Shenzhen Gaoyi Intelligent Electrical Co ltd
Current assignee: Shenzhen Gaoyi Intelligent Electrical Co ltd
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2021-10-15
Anticipated expiration: 2041-06-25
Also published as: CN113507224B

Abstract

The invention discloses a three-phase buck-boost rectifying converter and a control method thereof, wherein the three-phase buck-boost rectifying converter comprises an input rectifying bridge group, a buck unit and an energy storage freewheeling 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 follow current unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth follow current inductors and a filter capacitor. The three-phase rectifier converter is provided with two buck switch units, can work in parallel in the same phase or in parallel in a staggered phase, can realize the maximum multiplexing of an 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 a switch tube, and is suitable for a middle-power and high-power output voltage rangeWide envelope or output voltage between

Is multiplied by

The input phase voltage range is multiplied, and the high efficiency and high power density are needed.

Description

Three-phase buck-boost rectifier converter and control method

Technical Field

The application relates to the field of power electronics, in particular to a three-phase buck-boost rectification converter and a control method.

Background

The power of the current electric equipment is larger and larger, the electric equipment adopting a three-phase power supply mode is more and more, the electric energy quality of the power grid is greatly damaged if the electric equipment does not have a Power Factor Correction (PFC) function, and even paralysis of the power grid can be caused in severe cases. In order to meet the quality requirement of a power grid and reduce harmonic pollution to the power grid or cause unnecessary transmission burden of a distribution network, three-phase electric equipment must have a PFC function or be additionally provided with a filter device so as to meet the requirements of relevant regulations.

Generally, a rectifier converter circuit for three-phase ac input is mainly of a two-level or three-level boost type if a PFC function is required. However, after boosting, the output voltage is high, and there is a limit to the use of the converter or load connected to the back end, such as inputting a 380V ac voltage of a nominal three-phase three-wire, the output is generally set at about 720V, even as high as 800V. When the rear-end output voltage needs to be adjusted by a converter, the conventional power tube with better performance is below 650V, and in recent years, novel switching devices such as SiC and the like with slightly higher voltage and better high-frequency switching performance are available, but the cost is high; in order to solve the limitation of the power device of the dc converter at the rear end of the rectifying converter and to take efficiency and other factors into consideration, a buck-type two-level rectifying converter has become a hot point of research in recent years, such as the boost-type PFC shown in fig. 1, which needs to be reduced when the initial voltage is low, and the buck-type PFC shown in fig. 2, which can stably output the rated voltage of the voltage peak voltage of 1.5 times the maximum voltage in theory if the buck-type PFC is adopted, and can stably output the required voltage if the required voltage exceeds the voltageWithin the pressure range but not up to

For the peak value of the multiplied phase voltage, a one-stage non-isolated DC/DC direct-current conversion circuit (such as a boost scheme) must be added at the rear end to convert the peak value into the required output voltage, and fig. 3 is implemented by adopting a boost or buck scheme and then performing one-stage DC/DC voltage stabilization conversion, so that the two-stage scheme has higher cost, and the efficiency is reduced due to the two-stage conversion.

Disclosure of Invention

The invention aims to provide a three-phase buck-boost rectifying converter and a control method thereof, and solves the technical problems that in the prior art, a plurality of current-guiding circuit-connecting devices are arranged, the current-guiding capacity of a buck switching device cannot be fully utilized, the loss is large, and the three-phase buck-boost rectifying converter is not suitable for being applied in 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 follow current unit; the input rectifier bridge group comprises first to third rectifier bridges, the first to third rectifier bridges comprise four diodes, the four diodes are respectively connected in series in two same directions 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 middle points of the two diodes in series in the bridge arm groups, a rectifier output positive end, namely the cathode of the bridge arm groups, and a rectifier output negative end, namely the anode of the bridge arm groups; the voltage reduction unit comprises two voltage reduction switch units, the first voltage reduction switch unit comprises first to fourth switch tubes and thirteenth to fourteenth diodes, and the second voltage reduction 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 of the input rectifier bridges; the energy storage follow current unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth follow current inductors and a filter capacitor; the three input rectifier bridge groups are respectively connected with any two phases of the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;

the first rectifier bridge comprises first to fourth diodes, and the positive rectifying output end of the first rectifier bridge, namely the cathodes of the first diode and the second diode, is connected with the drain electrode of the first switching tube; the negative end of the rectification output of the first rectifier bridge, namely the anodes of the third diode and the fourth diode, is connected with the source electrode of the second switching tube; the second rectifier bridge comprises fifth to eighth diodes; the positive rectification output end 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 rectifying output end of the third rectifier bridge, namely the cathodes of the ninth diode and the twelfth diode, is 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, is connected with the source electrode of the eighth switching tube; the source electrode of the third switching tube is connected with the cathode electrode of the thirteenth diode, one end of the first follow current inductor is respectively connected with the source electrode of the first switching tube, the source electrode of the third switching tube and the cathode electrode of the seventeenth diode, the other end of the first follow current inductor is respectively connected with the anode electrode of the nineteenth diode and the drain electrode of the ninth switching tube, and one end of the filter capacitor is connected with the cathode electrode of the nineteenth diode to form the positive output end of the rectifier converter; the drain electrode of the fifth switching tube is connected with the cathode of a fifteenth diode, one end of a third freewheeling 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 an eighteenth diode, the other end of the third freewheeling inductor is respectively connected with the anode of a twentieth diode and the drain electrode of a tenth switching tube, and the cathode of the twentieth diode is connected with the positive output end of the rectifying converter; the source electrode of the fourth switch tube is connected with the anode of the fourteenth diode, one end of the second freewheeling inductor is respectively connected with the drain electrode of the second switch tube, the drain electrode of the fourth switch tube and the anode of the seventeenth diode, and the other end of the second freewheeling inductor is respectively connected with the source electrode of the ninth switch tube and the filter capacitor to form the 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 freewheeling inductor is 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 respectively, and the other end of the fourth freewheeling inductor is connected with the source electrode of the tenth switching tube.

Furthermore, the first to tenth switching tubes are semiconductor devices controlled to be turned on and turned off by high-frequency driving signals, and the switching tubes are provided with anti-parallel diodes which are integrated diodes, parasitic diodes or extra diodes.

Further, the filter capacitor is a non-polar capacitor or a polar capacitor; and 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 freewheeling inductor and the second freewheeling inductor may be two separate inductors, or two inductors wound on the same magnetic material; the third freewheeling inductor and the fourth freewheeling inductor may be two separate inductors, or two inductors wound on the same magnetic material.

The three-phase three-wire power supply further comprises an input filter, and 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 for a non-isolated three-phase buck-boost rectifier converter, which is used for controlling the non-isolated three-phase buck-boost rectifier converter according to the first technical solution, includes the following steps:

s100: analyzing the phase and the interval of each phase power supply at the current moment according to the phase lock of the input three-phase three-wire power supply voltage signal;

s200: analyzing the instantaneous value of the voltage of each phase power supply in each section according to the phase;

s300: applying a driving signal to the voltage reduction unit in the current interval section to carry out PWM driving control so as to enable two-phase current with higher instantaneous value to be firstly conducted; switching off a switching tube on the conducted instantaneous value secondary high-phase alternating current circuit, and continuing conducting the current of the phase with the highest instantaneous value and the phase with the lowest instantaneous value; if the amplitude directions of the lowest phase of the instantaneous value and the second highest phase of the instantaneous value are the same and share one voltage reduction switch unit channel, directly switching off all switch tubes in the voltage reduction switch unit;

s400: when two phases of current with higher instantaneous values are conducted, judging whether the maximum numerical value of the interphase instantaneous value pressure difference of the conducted two phases is larger than or equal to a set value of output voltage or not, and controlling a ninth switching tube and a tenth switching tube, wherein if the maximum numerical value of the interphase instantaneous value pressure difference of the conducted two phases is larger than or equal to the set value of the output voltage, the ninth switching tube or the tenth switching tube is not required to be switched on, and if the maximum numerical value of the interphase instantaneous value pressure difference of the conducted two phases is smaller than the set value of the output voltage, the ninth switching tube or the tenth switching tube is required to be switched on;

s500: all driving signals of the voltage reduction unit are turned off, and follow current is performed through the energy storage follow current unit, so that each phase of current can be conducted in each switching period.

Further, the specific method of step S300 is: simultaneously applying high-mode PWM driving signals with the same duty ratio to corresponding switching tubes in two-phase alternating current loops with the highest instantaneous value and the lowest instantaneous value, and simultaneously applying middle-mode PWM driving signals to corresponding switching tubes in current loops with the next-highest amplitude instantaneous value, so that the switching tubes applying the high-mode PWM driving signals are switched off in each section, and the switching tubes applying the middle-mode PWM driving signals are switched off firstly; and if the amplitude directions of the lowest phase of the instantaneous value and the second highest phase of the instantaneous value are the same and share one step-down switching unit channel, applying a 'middle' mode PWM (pulse width modulation) driving signal to a switching tube in the step-down switching unit.

Further, when the ninth switching tube or the tenth switching tube is in an on state, the PWM switching frequency of the ninth switching tube or the tenth switching tube is consistent with the PWM switching frequency of the first to eighth switching tubes.

Furthermore, the first to eighth switching tubes in the first step-down switching unit and the second step-down switching unit work in the same frequency and phase or work in a staggered mode according to 0-1/2 high-frequency switching cycles.

The invention has the beneficial effects that:

(1) from the structure and performance, the defect of high voltage at the rear end of the traditional boost three-phase rectification conversion circuit is overcome, the complexity of conversion of a multi-stage circuit is also avoided, the limitation of a direct-current converter power device at the rear end is reduced, and the selectable space is larger;

(2) the traditional boost or buck three-phase rectification conversion circuit is changed, the output voltage has smaller limitation compared with the alternating current input, can be boost, buck and even the voltage with a phase difference amplitude, namely the output voltage is between

Is multiplied by

Within a range of multiple input phase voltages, the advantages of replacing the traditional passive PFC are obvious, and particularly replacing the traditional three-phase passive PFC below 30 kW;

(3) the circuit breakover impedance of the circuit is only half of that of the existing known scheme under the condition of using the same switching tube in a voltage reduction mode, the efficiency is higher, and the circuit is suitable for occasions with high efficiency and high power density requirements;

(4) due to the structural simplification, the control method is simplified by applying regular or logic combined PWM driving signals to the switching tube of each phase in view of the switching operation of the PFC function; meanwhile, the impedance of the positive and negative current loops among the parallel circuits is changed by adjusting the conduction time of each phase loop, so that the cross circulation is avoided.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used 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 it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic diagram of a conventional 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 of three-phase voltage waveforms and a schematic diagram of junction definition in embodiment 1 of the present invention;

fig. 6 is a schematic diagram 1 of an AB phase conduction loop in an AC-BC interval according to embodiment 1 of the present invention, which is in a buck inductor energy storage mode;

FIG. 7 is a schematic diagram of a BC-phase continuous flow loop in an AC-O interval in embodiment 1 of the present invention;

FIG. 8 is a schematic diagram of an O-BC interval AC phase-continuous flow loop in embodiment 1 of the present invention;

FIG. 9 is a schematic diagram of an AC-BC interval inductor current freewheel circuit according to embodiment 1 of the present invention;

fig. 10 is a schematic diagram 2 of an AB phase conduction loop in an AC-BC interval according to embodiment 1 of the present invention, which is in a boost inductor energy storage mode;

fig. 11 is a schematic diagram 3 of an AB phase conduction loop in an AC-BC interval according to embodiment 1 of the present invention, which is a boost inductor energy release mode;

FIG. 12 is a schematic diagram 1 of an equivalent transformation of embodiment 1 of the present invention;

FIG. 13 is a schematic diagram 2 showing an equivalent transformation in embodiment 1 of the present invention;

fig. 14 is a schematic diagram of the relationship between the driving waveforms of the switch groups in the three-phase ac cycle according to embodiment 1 of the present invention.

The reference signs explain: FB1, a first rectifier bridge, FB2, a second rectifier bridge, FB3, a third rectifier bridge, D1, a first diode, D2, a second diode, D3, a third diode, D4, a fourth diode, D5, a fifth diode, D6, a sixth diode, D7, a seventh diode, D8, an eighth diode, D9, a ninth diode, D10, a twelfth diode, D11, an eleventh diode, D12, a twelfth diode, D13, a thirteenth diode, D13, a fourteenth diode, D13, a fifteenth diode, D13, a sixteenth diode, D13, a seventeenth diode, D13, an eighteenth diode, D13, a nineteenth diode, D13, a twentieth diode, Q13, a first switch tube, Q13, a second switch tube, Q13, a third switch tube, Q13, a fourth switch tube, Q13, a fifth switch tube, Q13, a fourth switch tube, a Q13, a fifth switch tube, a fourth switch tube, a fifth diode, a D13, a fourth diode, a D6957, a fifth diode, a fourth diode, a fifth diode, a fourth diode, a fifth diode, a fourth diode, a fifth diode, a fourth diode, a sixth diode, a fourth diode, a sixth diode, a fourth diode, a fifth diode, a fourth diode, a sixth diode, a fourth diode, a sixth diode, a fourth, Q6, sixth switching tube, Q7, seventh switching tube, Q8, eighth switching tube, Q9, ninth switching tube, Q10, tenth switching tube, L1, first freewheeling inductor, L2, second freewheeling inductor, L3, third freewheeling inductor, L4, fourth freewheeling inductor, C1, filter capacitor, Phase A. A Phase input, Phase B. B Phase input and Phase C. C Phase input.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments disclosed below.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. The use of "first," "second," and similar terms in the description and claims of this patent application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. Also, the use of 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 "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships are changed accordingly.

As shown in fig. 4, a non-isolated three-phase buck-boost rectifier converter includes an input rectifier bridge group, a buck unit and an energy storage freewheeling unit; the input rectifier bridge group comprises first to third rectifier bridges FB 1-FB 3, the first to third rectifier bridges FB 1-FB 3 respectively comprise four diodes, the four diodes are respectively connected in series in two same directions 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 middle points of the two diodes in series 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, the first voltage reduction switch unit comprises first to fourth switch tubes Q1-Q4 and thirteenth to fourteenth diodes D13-D14, the second voltage reduction switch unit comprises fifth to eighth switch tubes Q5-Q8 and fifteenth to sixteenth diodes D15-D16; the first buck switch unit and the second buck switch unit share one of the input rectifier bridges; the energy storage follow current unit comprises seventeenth to twentieth diodes D17-D20, ninth to tenth switching tubes Q9-Q10, first to fourth follow current inductors L1-L4 and a filter capacitor C1; the three input rectifier bridge groups are respectively connected with any two phases of the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;

the first rectifying bridge FB1 comprises first to fourth diodes D1-D4, and the positive rectifying output end of the first rectifying bridge FB1, namely the cathodes of the first diode D1 and the second diode D2, is connected with the drain of a first switching tube Q1; the rectified output negative terminal of the first rectifying bridge FB1, namely the anodes of the third diode D3 and the fourth diode D4 are connected with the source of the second switching tube Q2; the second rectifier bridge FB2 comprises fifth to eighth diodes D5-D8; the positive rectifying output terminals of the second rectifying bridge FB2, i.e., the cathodes of the fifth diode D5 and the sixth diode D6 are connected to the anode of the thirteenth diode D13 and the anode of the fifteenth diode D15, respectively; the rectified output negative terminal of the second rectifying bridge FB2, i.e. the anodes of the seventh diode D7 and the eighth diode D8 are connected to the cathode of the fourteenth diode D14 and the cathode of the sixteenth diode D16, respectively; the third rectifying bridge FB3 comprises ninth to twelfth diodes D9-D12, and the positive rectifying output end of the third rectifying bridge FB3, namely the cathodes of the ninth diode D9 and the twelfth diode D12, is connected with the drain of a seventh switch tube Q7; the negative rectifying output terminal of the third rectifying bridge FB3, namely the anode D12 of the eleventh diode D11 and the twelfth diode, is connected to the source of the eighth switching tube Q8; the source of the third switching tube Q3 is connected with the cathode of the thirteenth diode D13, one end of the first freewheeling inductor L1 is connected with the source of the first switching tube Q1, the source of the third switching tube Q3 and the cathode of the seventeenth diode D17, respectively, the other end is connected with the anode of the nineteenth diode D19 and the drain of the ninth switching tube Q9, one end of the filter capacitor C1 is connected with the cathode of the nineteenth diode D19, forming the positive output end of the rectifier converter; the drain of the fifth switching tube Q5 is connected with the cathode of a fifteenth diode D15, one end of a third freewheeling inductor L3 is connected with the source of the fifth switching tube Q5, the source of the seventh switching tube Q7 and the cathode of an eighteenth diode D18, respectively, the other end is connected with the anode of a twentieth diode D20 and the drain of a tenth switching tube Q10, and the cathode of the twentieth diode D20 is connected with the positive output end of the rectifying converter; the source of the fourth switching tube Q4 is connected with the anode of the fourteenth diode D14, one end of the second freewheeling inductor L2 is connected with the drain of the second switching tube Q2, the drain of the fourth switching tube Q4 and the anode of the seventeenth diode D17, respectively, and the other end is connected with the source of the ninth switching tube Q9 and the filter capacitor C1, respectively, so as to form the negative output end of the rectifier-converter; the source of the sixth switching tube Q6 is connected to the anode of the sixteenth diode D16, one end of the fourth freewheeling inductor L4 is connected to the drain of the sixth switching tube Q6, the drain of the eighth switching tube Q8 and the anode of the eighteenth diode D18, respectively, and the other end is connected to the source of the tenth switching tube Q10.

In the embodiment of the present invention, the first ac input port of the first rectifier bridge FB1, i.e. the anode of the first diode D1, is connected to a of a three-phase three-wire power supply; a second alternating current input port of the first rectifier bridge FB1, namely the anode of the second diode D2, is connected with the B of the three-phase three-wire power supply; a first alternating current input port of the second rectifier bridge FB2, namely an anode of a fifth diode D5, is connected with the B of the three-phase three-wire power supply; a second alternating current input port of the second rectifier bridge FB2, namely an anode of a sixth diode D6, is connected with the C of the three-phase three-wire power supply; a first alternating current input port of the third rectifier bridge FB3, namely an anode of a ninth diode D9 is connected with A of the three-phase three-wire power supply; a second alternating current input port of the third rectifier bridge FB3, namely an anode of a twelfth pole tube D10, is connected with the C of the three-phase three-wire power supply; the first buck switching unit and the second buck switching unit share a second rectifier bridge FB 2; the first freewheeling inductor L1 and the second freewheeling inductor L2 may be two separate inductors, or 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 non-polar capacitor or a polar capacitor; if the filter capacitor C1 is a polar capacitor, the anode 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 cathode is connected to the source of the ninth switching transistor Q9 and the source of the tenth switching transistor 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, plays a role in filtering the input power supply and can also play a role in filtering and attenuating internal clutter reflected to the input end. The first to tenth switching tubes Q1-Q10 may be MOS transistors, IGBT transistors, etc., and it should be understood by those skilled in the art that the present invention is not limited to the above two semiconductor power switches, and may be other power devices capable of performing high frequency switching operation. Independent driving power supplies are used among the first to tenth switching tubes Q1-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:

s300: applying a driving signal to the voltage reduction unit in the current interval section to carry out PWM driving control so as to enable two-phase current with higher instantaneous value to be firstly conducted; switching off a switching tube on the conducted instantaneous value secondary high-phase alternating current circuit, and continuing conducting the current of the phase with the highest instantaneous value and the phase with the lowest instantaneous value; if the amplitude directions of the lowest phase of the instantaneous value and the second highest phase of the instantaneous value are the same and share one voltage reduction switch unit channel, directly switching off all switch tubes in the voltage reduction switch unit; the specific method comprises the following steps: simultaneously applying high-mode PWM driving signals with the same duty ratio to corresponding switching tubes in two-phase alternating current loops with the highest instantaneous value and the lowest instantaneous value, and simultaneously applying middle-mode PWM driving signals to corresponding switching tubes in current loops with the next-highest amplitude instantaneous value, so that the switching tubes applying the high-mode PWM driving signals are switched off in each section, and the switching tubes applying the middle-mode PWM driving signals are switched off firstly; if the amplitude directions of the lowest phase and the next highest phase of the instantaneous value are the same and share one voltage reduction switch unit channel, applying a 'middle' mode PWM driving signal to a switch tube in the voltage reduction switch unit;

s400: when the two-phase current with higher instantaneous value is conducted, whether the maximum value of the interphase instantaneous value voltage difference of the two conducted phases is larger than or equal to the set value of the output voltage is judged, the ninth switch tube Q9 and the tenth switch tube Q10 are controlled, if the maximum value of the interphase instantaneous value voltage difference of the two conducted phases is larger than or equal to the set value of the output voltage, the ninth switch tube Q9 or the tenth switch tube Q10 does not need to be turned on, and if the maximum value of the interphase instantaneous value voltage difference of the two conducted phases is smaller than the set value of the output voltage, the ninth switch tube Q9 or the tenth switch tube Q10 needs 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 frequency of the first to eighth switching tubes Q1-Q8;

The method for judging the magnitude of the instantaneous value is to compare the magnitude of the absolute value of the instantaneous value of each phase. First to tenth switching tubes Q1~ Q10 in first step-down switch unit and the second step-down switch unit are with the same frequency in-phase work or according to 0~1/2 high frequency switching cycle phase-staggered work. In the embodiment of the invention, the first to tenth switching tubes Q1-Q10 in the first buck switching unit and the second buck switching unit work in a staggered mode according to 1/2 high-frequency switching cycles, and the optimal value is obtained.

As shown in fig. 5, the three-Phase ac power supply includes an a-Phase input Phase a, a B-Phase input Phase B, and a C-Phase input Phase C. For convenience of description, the three-phase voltage is set to have a phase difference of 120 degrees and is a sinusoidal voltage, and one cycle is carried out every 360 degrees; in consideration of intuitive convenience, the convergence points are respectively defined as AC (30 °), BC (90 °), BA (150 °), CA (210 °), CB (270 °), AB (330 °), AC (30 ° or 390 °), with 30 ° to 390 °, i.e., a 30 ° point of the next cycle as one complete cycle; the zero crossing point is marked as "0".

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 the voltage reduction. Therefore, in the embodiment of the present invention, the two phases with the largest instantaneous values in the three phases form the conducting opposite output terminals to form a voltage difference, and with reference to 0 ° or the origin of the phase a in fig. 5, the lowest instantaneous difference value of the voltage difference should be the 30 °, 90 °, 150 °, 210 °, 270 °, 330 ° points of the phase a, or similar periodic phase difference relationship points, where the lowest value at this time is the phase voltage highest amplitude value 1+1/2 times; the highest point of the instantaneous difference of the voltage difference is the point of 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees and 360 degrees of the phase A or the similar periodic phase difference relation point, and the highest value at this time is

The maximum amplitude of the phase voltage is multiplied. When the output voltage is set to be less than

Wherein

Is the effective value of the phase voltage, thenThe voltage difference is smaller than the minimum voltage difference value of two phases of three-phase voltage at any time, and the output working state of the embodiment of the invention is in a full voltage reduction mode. When the output voltage is set to be greater than

The voltage difference is higher than the maximum voltage difference value of the three-phase voltage at any time, and the output working state of the embodiment of the invention is a boosting mode. When the output voltage is between

And

meanwhile, the working mode of the embodiment of the invention has both voltage boosting and voltage reducing.

(1) Determining a buck mode based on output voltage requirements

As shown in fig. 6, in the AC-BC interval from the AC point to the BC point, the absolute values of instantaneous values of the phase a and phase B voltages are higher than that of the phase C, so that the internal positive side diodes of the first rectifier bridge FB1 and the third rectifier bridge FB3 connected to a, i.e., the first diode D1 and the ninth diode D9, are turned on by the forward bias voltage, denoted by 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 B, i.e., the fourth diode D4 and the seventh diode D7, are turned on by the forward bias voltage, denoted by Vb; the internal diodes of the second rectifier bridge FB2 and the third rectifier bridge FB3 connected to C are reverse biased to be non-conductive by the voltages Va and Vb, the cathode voltage of the D10 of the twelfth diode is clamped by Va, and the anode voltage of the eighth diode D8 is clamped by Vb. When the first to fourth switching tubes Q1-Q4 or the fifth to eighth switching tubes Q5-Q8 are simultaneously applied with the PWM driving turn-on signal, the corresponding switching tube of the Q first to fourth switching tubes Q1-Q4 or the fifth to eighth switching tubes Q5-Q8 is turned on. The current of the phase a can flow through the first diode D1 and the first switch tube Q1, the first freewheeling inductor L1, the nineteenth diode D19, the filter capacitor C1 and the second freewheeling inductor L2, and return to the phase B alternating current source through the branch formed by the second switch tube Q2 and the fourth diode D4 or the branch formed by the fourth switch tube Q4, the fourteenth diode 4 and the seventh diode D7; the current of the a-phase may also flow through the third freewheeling inductor L3, the twentieth diode D20 and the filter capacitor C1 via the ninth diode D9 and the seventh diode Q7, and return to the B-phase alternating current source via the fourth freewheeling inductor L4, the sixth switching tube Q6, the sixteenth diode D16 and the seventh diode D7. There are two step-down through-current loops of the first step-down switching unit and the second step-down switching unit, and the two step-down switching 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, since the first freewheeling inductor L1 and the second freewheeling inductor L2 exist in the current loop of the first buck switching unit, the current does not reverse immediately, the electromotive force of the inductor reverses to freewheel, and the inductor is turned on by the forward bias voltage with the sixth diode D6 and the thirteenth diode D13. The third switching tube Q3 is always turned on by the on-drive signal, and the current flows from the phase C 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 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 to the phase B alternating current source. The through-current loop of the second buck switch unit does not immediately reverse due to the existence of the third freewheeling inductor L3 and the fourth freewheeling inductor L4, the electromotive force of the inductor reverses to freewheel, meanwhile, the third rectifier bridge FB3 connected with the C is reverse biased by the A phase voltage and can not be conducted, the sixth diode D6 and the fifteenth diode D15 are forward biased and conducted, since the fifth switch tube Q5 is always conducted by the on-driving signal, the current flows from the phase C through the sixth diode D6, the fifteenth diode D15 and the fifth switch tube Q5, through the third freewheeling tube L3, the twentieth diode D20, the filter capacitor C1 and the fourth freewheeling inductor L4, and the current returns to the B-phase alternating-current source through the sixth switching tube Q6, the sixteenth diode D16 and the seventh diode D7, and at this time, the second rectifier bridge FB2 where the first buck switching unit and the second buck switching unit share the C phase serves as a path through which the current must return.

As shown in fig. 8, in the interval 0-BC, after the driving signals of the fifth to sixth switching tubes Q5-Q6 are turned off, at this time, because the third freewheeling inductor L3 and the fourth freewheeling inductor L4 exist in the second buck switching unit loop, the current does not immediately reverse, the inductor electromotive force reverses to freewheel, meanwhile, the twelfth diode D12 is turned on by the forward bias voltage, because the seventh switching tube Q7 and the eighth switching tube Q8 are always turned on by the on-driving signal, the current flows from the phase a through the ninth diode D9 and the seventh switching tube Q7, flows through the third freewheeling inductor L3, the twenty diode D20, the filter capacitor C1 and the fourth freewheeling diode L4, and returns to the phase C alternating current source through the eighth switching tube Q8 and the twelfth diode D12. The first buck switch unit is in the same direction as B, C, and the instantaneous value of the phase C is smaller than that of the phase B, so the eighth diode D8 is reverse biased and cannot be conducted, at this time, the first to fourth switch tubes Q1 to Q4 cannot apply conduction driving signals any more, but because the loop has the first freewheeling inductor L1 and the second freewheeling inductor L2, the electromotive force of the inductors is reversed, so that the seventeenth diode D17 is reverse biased, and 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.

As can be seen from the above, the key to realize that each phase can conduct current in each switching period, thereby realizing a high PF value and a low THDI is that two phases with higher instantaneous values and opposite polarities are conducted, and energy is stored in the inductance of the loop, and then the switching tube in the conducting loop of the next-highest phase with the absolute value of the instantaneous value is turned off, so that the follow current passes through the lowest phase with the instantaneous value; if the two-phase power supplies have the same polarity and are connected to the same input bridge group, i.e. share the same switching circuit, the bridge diode of the phase with the lowest instantaneous value will be reverse biased and not conducting. Therefore, in each switching period, the current loop of the next-highest phase with the instantaneous value is firstly switched off, the PWM driving mode of the switching tube which is firstly switched off is marked as "medium", and the PWM driving mode of the switching tube which is then switched off is marked as "high". Although the switching tube driving of the phase with the lowest instantaneous value can also apply a high mode PWM driving signal, the switching tube needs to be conducted after the middle mode PWM driving signal is switched off, and the PWM driving mode can be recorded as a low mode. Therefore, in the actual control of this embodiment, although there may be three duty ratios of the on-state of the switching tube, there are normally two values of the PWM driving per cycle to satisfy the control.

As shown in fig. 9, when all PWM on-voltages applied to the switching tubes are turned off, all current loops input after the switching tubes are turned off are cut off, and since the current of the inductors cannot be transited, the first freewheeling inductor L1, the second freewheeling inductor L2, the third freewheeling inductor L3 and the fourth freewheeling inductor L4 must keep freewheeling, so that the seventeenth diode D17 and the eighteenth diode D18 are biased to be turned on by the forward voltage respectively. The current can return to the positive end of the filter capacitor C1 or the equivalent load positive end of the circuit output end through a branch consisting of the second freewheeling inductor L2, the seventeenth diode D17, the first freewheeling inductor L1 and the nineteenth diode D19 or a branch consisting of the fourth freewheeling inductor L4, the eighteenth diode D18, the third freewheeling inductor L3 and the twentieth diode D20 by the negative end of the filter capacitor C1 or the equivalent load negative end of the circuit output end to form a current freewheeling loop, the stored energy in the inductor is released, and the conversion state of the rectifying converter in one switching period is completed.

According to the operating principle of the embodiment of the present invention, in the voltage reduction unit, in the same switching period, the PWM driving signal mode in which the PWM driving signal of the switching tube on the conducting loop is first turned off is recorded as "medium", and the PWM driving signal mode in which the PWM driving signal is then turned off is recorded as "high". According to the control method, two phases with relatively high instantaneous values and opposite polarities are firstly conducted in each switching period, voltage drop and energy storage can be generated by the inductance of a conducting loop, and then the switching tube in the next-highest phase passage with the instantaneous values is turned off, so that follow current passes through the lowest phase of the absolute value of the instantaneous values. Meanwhile, because the two-phase power supplies have the same polarity and are connected to the same input rectifier bridge group and share the same buck switch unit loop, the diode of the input rectifier bridge group connected to the phase with the lowest instantaneous value is reverse biased and cannot be conducted, meanwhile, the buck switch unit has no other path to conduct the phase, and under the condition of the state, the corresponding switch tube in the buck switch unit must be turned off. If the duty ratio of the PWM driving signal is modulated well according to real-time control, the current waveform and the voltage waveform can be made to follow the same, so that a higher PF value can be obtained, namely, the PFC correction function is realized.

In addition, when the same effect as described above needs to be achieved without considering the control complexity, another control mode may be adopted, in which the switching tubes of the respective buck circuits are not simultaneously applied with driving signals, signals are applied to two phases with higher instantaneous values and opposite polarities to turn on the two phases, then the switches of the current paths of the next higher instantaneous values in the two phases that are being turned on are turned off, and the driving signals are applied to the switching tube on the ac circuit with the lowest instantaneous value to turn on the switching tube, so that the freewheeling current passes through the phase with the lowest instantaneous value, and then the switching tubes in the buck switching units are controlled to be turned off. Therefore, in each switching period, the current loops of the two phases with the same amplitude and the same direction of the higher phase are firstly turned off, the PWM driving signal mode which is firstly turned off is marked as 'middle', the PWM driving signal mode which is then turned on is marked as 'low', and the PWM driving signal mode which is firstly turned on and is finally turned off is marked as 'high'. This approach does not depart from our previously described "high" and "medium" control strategy and will not be described in detail.

(2) Determining boost mode based on output voltage demand

The first to fourth switching tubes Q1 to Q4 and the fifth to eighth switching tubes Q5 to Q8 need to be driven correspondingly according to the driving control method shown in fig. 14, and also need to apply PWM driving to the ninth switching tube Q9 and the tenth switching tube Q10, when the ninth switching tube Q9 and the tenth switching tube Q10 are turned on, the input current is directly short-circuited by the ninth switching tube Q9 or the tenth switching tube Q10 to form a backflow loop. As shown in fig. 10, at this time, the voltage of the ac source is applied to the inductor first freewheeling inductor L1 and the inductor second freewheeling inductor L2, and the inductor third freewheeling inductor L3 and the inductor fourth freewheeling inductor L4, respectively, so that the inductor stores energy. As shown in fig. 11, when the ninth switching tube Q9 and the tenth switching tube Q10 are driven off, the current cannot be reversed and the current continues to be maintained in the original direction due to the presence of the first freewheeling inductor L1, the second freewheeling inductor L2, the third freewheeling inductor L3 and the fourth freewheeling inductor L4, so that the inductor electromotive force is reversed and 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 circuit of the embodiment of the invention in each working mode can be equivalently transformed. Fig. 12 is obtained by simplifying fig. 4 according to the symmetry and the switching functionality, and in the transient state, the ac source is rectified by the diode and then equivalent to a dc source, or the ac source plus the diode can be regarded as a dc source in the transient circuit; meanwhile, the combined switch tube in the alternating current loop can be simplified and equivalent to a switch, so that the figure 12 can be further simplified into the figure 13. After the circuit of the embodiment of the invention is subjected to the above equivalence, the circuit can be actually regarded as a buck-boost circuit, so that the circuit has a typical buck function and a boost function. Considering the conduction loss of devices in the circuit, the loss of duty ratio conduction angles such as dead zones, drive 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 the effective value of the input three-phase voltage

The ratio may be slightly more than this range.

For other sections, the control method is similar to that of the AC-BC section, if two-phase power supplies have the same polarity and are connected to the same input rectifier bridge group and share the same buck switch unit loop, the rectifier bridge diode of the phase with the lowest instantaneous value will be reverse biased and cannot be conducted, and at the same time, the buck switch unit has no other path to conduct the phase current, and under the condition of this state, the corresponding switch tube in the buck switch unit is turned off, and at this time, the corresponding switch tube can only apply a "medium" PWM drive signal.

For a BC-BA interval, in a BC-0 interval, a driving signal of a switching tube of an A, B two-phase current path is a high mode PWM driving signal, a driving signal of a switching tube of a C-phase current path is a middle mode PWM driving signal, namely a C-phase loop is firstly turned off; in the interval 0-BA, the driving signal of the switch tube of the C, B two-phase current path is a high mode PWM driving signal, and the driving signal of the switch tube of the A-phase current path is a middle mode PWM driving signal, namely, the A-phase loop is firstly turned off.

For a BA-CA interval, in a BA-0 interval, a driving signal of a switching tube of an A, C two-phase current path is a high mode PWM driving signal, a driving signal of a switching tube of a B-phase current path is a middle mode PWM driving signal, namely a B-phase loop is firstly turned off; in the interval 0-CA, 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 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, the driving signal of the switching tube of the A-phase current path is a middle mode PWM driving signal, namely, the A-phase loop is firstly turned off; in the interval 0-CB, 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 middle mode PWM driving signal, namely, a B-phase loop is firstly turned off.

For a CB-AB interval, in a CB-0 interval, a driving signal of a switching tube of an B, A two-phase current path is a high mode PWM driving signal, a driving signal of a switching tube of a C-phase current path is a middle mode PWM driving signal, namely a C-phase loop is firstly turned off; in the interval from 0 to AB, 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 middle mode PWM driving signal, namely, the A-phase loop is firstly turned off.

For an AB-AC interval, in an AB-0 interval, a driving signal of a switching tube of an C, A two-phase current path is a high mode PWM driving signal, a driving signal of a switching tube of a B-phase current path is a middle mode PWM driving signal, namely a B-phase loop is firstly turned off; in the 0-AC interval, 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 middle mode PWM driving signal, namely, the C-phase loop is firstly turned off.

In reality, three-phase voltage is not completely ideal, changes of phase, amplitude and direction exist, and the driving waveform of each section can be judged and generated only according to actual phase locking, so that the judgment is carried out according to the characteristics of the instantaneous waveform of each alternating voltage of the section, but not according to an ideal angle, the driving waveform can be divided into twelve sections according to the characteristics of three-phase power signals, and the waveform logic table of each switching tube driving signal is shown in table 1 according to the principle.

TABLE 1 Driving state logic table for switching tube

The "low" mode indicates that the same drive signal as the switching tube having the maximum instantaneous value can be applied by the control method described above, or the drive signal that makes a free-wheeling with the switching tube having the maximum instantaneous value is applied at the latest before the drive signal of the switching tube of the other phase having the instantaneous value in the same direction is turned off, and the duty ratio is described as "high-medium". The "low 1" mode means that no drive signal needs to be applied or a signal of any duty cycle can be applied during the conduction of the switching tube in the morning at the maximum instantaneous value; therefore, in consideration of simplification and normalization of control, the "low" and "low 1" modes are normalized to the following drive signals without affecting the function implementation. In this case, table 1 can be simplified into a logic table of driving states of the switching tube as shown in table 2:

TABLE 2 simplified logic table of driving states of switching tubes

According to the logic table of the driving waveform, the following control method can be executed:

detecting input alternating voltage, judging whether each index of the input voltage meets a working condition or not, and continuing waiting when the index does not meet the condition; if the current phase of the three-phase three-wire power supply meets the conditions, starting working, judging according to the phase locking of the input three-phase three-wire power supply voltage signals, and analyzing the phase and the interval of each phase power supply at the current moment; and analyzing the absolute value of the instantaneous value of the voltage of each phase power supply, and judging whether the embodiment of the invention works in a boosting mode or a voltage reduction mode according to the instantaneous value of the input interphase voltage and the set value of the output voltage. If the voltage boosting mode is adopted, PWM is applied according to the operation result to drive the ninth switch tube Q9 or the tenth switch tube Q10 to be turned on; otherwise, the voltage reduction mode is performed, 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 buck switch unit loop, the rectifier bridge diode of the phase with the lowest instantaneous value is reversely biased and cannot be conducted, meanwhile, the buck switch unit does not have other paths to enable the phase current to be conducted, under the condition of the state, the corresponding switch tube in the buck switch unit is turned off, and at the moment, the corresponding switch tube can only apply a 'middle' PWM driving signal; and applying a middle mode PWM driving signal to a corresponding switching tube in a current loop of a second-highest phase with the absolute value of the instantaneous value, and applying high mode PWM driving signals with the same duty ratio to the other switching tubes. The two-phase power supply with higher instantaneous value forms a current path, and simultaneously, a boost energy storage or a voltage-dividing energy storage is formed on an inductor of the energy storage follow current unit, after the 'middle' mode PWM driving signal is switched off, the other two-phase switching tube which originally applies the 'high' mode PWM driving signal can provide a follow current path for the inductor to be continuously conducted, if the boost mode is adopted, after the boost switching tube is switched off, the inductive electromotive force is reversely connected with the input voltage in series, and then the energy-releasing follow current mode is entered. The specific duty ratio of the PWM driving signals in the high mode and the middle mode is determined by the real-time control operation result of the controller. When the drive of all the switch tubes is cut off, the electromotive force of the inductor is reversed, and the inductor current forms a path by the seventeenth diode D17 or the eighteenth diode D18. In general, the time for inputting the conduction current of each phase is in a relative relationship with the instantaneous value of the phase voltage, i.e., the higher the instantaneous value, the longer the current conduction time, the larger the duty ratio, the current conduction time of the phase with the maximum instantaneous value is equal to the sum of the current conduction times of the other two phases with relatively lower instantaneous values and less than the total time of the switching period, and the relevant waveform driving is as shown in fig. 14.

By the control method, current circulation of three phases in each switching period is effectively guaranteed, and meanwhile, the duty ratio of the PWM driving signal is well modulated according to real-time control, so that the current waveform and the voltage waveform can be consistent, a high PF value can be obtained, and the PFC correction function is realized.

In the embodiment of the invention, two voltage reduction switch unit paths exist, and each voltage reduction switch unit can independently realize power conversion, so that the two voltage reduction switch units can work in the same frequency and phase or in a staggered phase mode according to 0-1/2 high-frequency switch cycles; according to the total ripple of the input current and the comprehensive characteristics of the system, the interleaving mode with 1/2 high frequency switching cycles is the best mode of the embodiment of the present invention, i.e. the driving of the first to fourth switching tubes Q1-Q4 or the switching tubes of the fifth to eighth switching tubes Q5-Q8 are interleaved with 1/2 switching cycles. The alternating current input end can be connected in parallel in a staggered mode, so that the alternating current input current can be more easily continuous, the defect of interruption of the input current of the voltage-reducing power supply is overcome, and meanwhile, the input filter and EMI interference can be reduced.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A non-isolated three-phase buck-boost rectifier converter is characterized by comprising an input rectifier bridge group, a buck unit and an energy storage freewheeling unit; the input rectifier bridge group comprises first to third rectifier bridges, the first to third rectifier bridges comprise four diodes, the four diodes are respectively connected in series in two same directions 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 middle points of the two diodes in series in the bridge arm groups, a rectifier output positive end, namely the cathode of the bridge arm groups, and a rectifier output negative end, namely the anode of the bridge arm groups; the voltage reduction unit comprises two voltage reduction switch units, the first voltage reduction switch unit comprises first to fourth switch tubes and thirteenth to fourteenth diodes, and the second voltage reduction 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 of the input rectifier bridges; the energy storage follow current unit comprises seventeenth to twentieth diodes, ninth to tenth switching tubes, first to fourth follow current inductors and a filter capacitor; the three input rectifier bridge groups are respectively connected with any two phases of the three-phase three-wire power supply, and the input line voltage of each input rectifier bridge group is different;

2. The non-isolated three-phase buck-boost rectifier converter according to claim 1, wherein the first to tenth switching transistors are semiconductor devices controlled by high frequency driving signals to turn on and off, and the switching transistors have a cascode diode, and the cascode diode is an integrated diode, a parasitic diode, or an extra diode.

3. The non-isolated three-phase buck-boost rectifier converter according to claim 1, wherein the filter capacitor is a non-polar capacitor or a polar capacitor; and 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 according to claim 1, wherein the first freewheeling inductor and the second freewheeling inductor may be two separate inductors or two inductors wound on the same magnetic material; the third freewheeling inductor and the fourth freewheeling inductor may be two separate inductors, or two inductors wound on the same magnetic material.

5. The non-isolated three-phase buck-boost rectifier converter according to claim 1, further comprising an input filter coupled between the three-phase three-wire power source and the input rectifier bridge bank.

6. A control method for a non-isolated three-phase buck-boost rectifier converter, which is used for controlling the non-isolated three-phase buck-boost rectifier converter as claimed in any one of claims 1 to 5, and comprises the following steps:

7. The non-isolated three-phase buck-boost rectifier converter method according to claim 6, wherein the specific method in step S300 is as follows: simultaneously applying high-mode PWM driving signals with the same duty ratio to corresponding switching tubes in two-phase alternating current loops with the highest instantaneous value and the lowest instantaneous value, and simultaneously applying middle-mode PWM driving signals to corresponding switching tubes in current loops with the next-highest amplitude instantaneous value, so that the switching tubes applying the high-mode PWM driving signals are switched off in each section, and the switching tubes applying the middle-mode PWM driving signals are switched off firstly; and if the amplitude directions of the lowest phase of the instantaneous value and the second highest phase of the instantaneous value are the same and share one step-down switching unit channel, applying a 'middle' mode PWM (pulse width modulation) driving signal to a switching tube in the step-down switching unit.

8. The method as claimed in claim 6, wherein when the ninth switch tube or the tenth switch tube is in an on state, the PWM switching frequency of the ninth switch tube or the tenth switch tube is consistent with the PWM switching frequency of the first to eighth switch tubes.

9. The control method of a non-isolated three-phase buck-boost rectifier converter according to claim 6, wherein the first to eighth switching tubes in the first buck switching unit and the second buck switching unit operate in the same frequency and phase or operate in a staggered phase according to 0 to 1/2 high frequency switching cycles.