A three-phase buck-boost inverter circuit and modulation method

Abstract

The present invention discloses a three-phase buck-boost inverter circuit and a modulation method, which includes a DC power supply circuit, a chopper circuit and a three-phase voltage source circuit. The input of the chopper circuit is connected to the DC power supply circuit, and the output of the chopper circuit is connected to the three-phase voltage source circuit; the DC power supply circuit is used for providing DC power supply for the inverter circuit; the chopper circuit is used to realize inversion in buck / boost / buck-boost mode; the three-phase voltage source circuit is used to absorb energy during inversion. The present invention is applicable to occasions where the input voltage varies within a wide range; the multi-mode modulation method maximally utilizes the DC input voltage, reduces the number of switching tubes operating at high frequencies, reduces switching losses, and improves the conversion efficiency; the volume, weight and cost of the inverter are reduced, and the power density is increased.

Description

Technical Field

[0001] The present invention relates to an inverter circuit and a modulation method, and in particular to a three-phase buck-boost inverter circuit and a modulation method. Background Art

[0002] The continuous advancement of industrialization has led to an increasing demand for energy, and resource depletion has become a major crisis facing mankind. With the rapid development of power electronics technology, inverter technology is widely used in defense fields such as aviation, aerospace, and navigation, as well as power inverters, transportation, postal and telecommunications, industrial control and other civil fields. In particular, with the increasing shortage of major energy sources such as oil, coal and natural gas, the development and utilization of new energy sources have received more and more attention. The key technology of using new energy, inverter technology, can convert DC power converted by other new energy sources such as batteries, solar cells and fuel cells into AC power and connect to the power grid for power generation. Therefore, inverter technology plays a vital role in the development and utilization of new energy.

[0003] Since renewable energy is deeply affected by external factors such as climate, weather and environment, its energy output has great randomness and uncertainty. One of the specific manifestations of this randomness and uncertainty is the wide fluctuation of output power, which is manifested as a wide range of changes in output DC voltage in photovoltaic cells, fuel cells and small DC wind turbines. This requires the inverter as an energy conversion device to withstand a wide range of input voltage fluctuations. Whether the inverter is independently supplying power to the load or connecting to the grid for power generation, it needs a stable output.

[0004] The current inverter circuit structure has the problems of small output voltage variation range, low conversion efficiency, large power switch fast-off loss, and large inverter size. Summary of the invention

[0005] Purpose of the invention: The present invention aims to solve the above-mentioned deficiencies in the prior art and provide a three-phase buck-boost inverter circuit and modulation method to solve the problems of small input voltage variation range, low conversion efficiency, large switching loss and large inverter size.

[0006] Technical solution: The three-phase buck-boost inverter circuit described in the present invention includes a DC power supply circuit, a chopper circuit and a three-phase voltage source circuit. The input of the chopper circuit is connected to the DC power supply circuit, and the output of the chopper circuit is connected to the three-phase voltage source circuit; the DC power supply circuit is used for DC power supply of the inverter circuit; the chopper circuit is used to realize inversion of buck / boost / buck-boost mode; the three-phase voltage source circuit is used to absorb energy during inversion.

[0007] The chopper circuit includes a power switch tube Q 1 ~Q 14 、Diode D 1 ~D14 and an inductor L 1 ; the emitter of the power switch tubes Q 1 ~Q 14 is respectively connected to the anode of the diodes D 1 ~D 14 ; the collector of the power switch tubes Q 4 、Q 7 is connected to the cathode of the diodes D 1 、D 10 ; the collector of the power switch tubes Q 5 、Q 8 is connected to the cathode of the diodes D 2 、D 11 ; the collector of the power switch tubes Q 6 、Q 9 is connected to the cathode of the diodes D 3 、D 12 ; the collectors of the power switch tubes Q 1 、Q 2 、Q 3 、Q 13 are connected together; the cathodes of the diodes D 4 、D 5 、D 6 、D 14 are connected together; the cathodes of the diodes D 7 、D 8 、D 9 、D 13 are connected together and then connected to one end of the inductor L 1 ; the collectors of the power switch tubes Q 10 、Q 11 、Q 12 、Q 14 are connected together and then connected to the other end of the inductor L 1 .

[0008] The DC power supply circuit includes a DC voltage source E; the three-phase voltage source circuit includes three-phase voltage sources a, b, and c with initial phases differing by 120° in sequence, and one ends of the three-phase voltage sources a, b, and c are connected together.

[0009] The positive pole of the DC voltage source E of the DC power supply circuit is connected to the collectors of the power switch tubes Q 1 、Q 2 、Q 3 、Q 13 of the chopper circuit; the negative pole of the DC voltage source E of the DC power supply circuit is connected to the cathodes of the diodes D 4 、D 5 、D 6 、D 14 of the chopper circuit.

[0010] The other end of the a-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switch tubes Q 4 and Q 7 and the cathodes of the diodes D 1 and D 10 of the chopper circuit. The other end of the b-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switch tubes Q 5 and Q 8 and the cathodes of the diodes D 2 and D 11 of the chopper circuit. The other end of the c-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switch tubes Q 6 and Q 9 and the cathodes of the diodes D 3 and D 12 of the chopper circuit.

[0011] The power switch tubes Q 1 to Q 14 are IGBTs or MOSFETs.

[0012] It includes a filter, and the filter is arranged between the three-phase voltage source circuit and the chopper circuit.

[0013] The buck modulation method of the three-phase buck-boost inverter circuit according to the present invention includes the following steps:

[0014] (1) When the grid voltage U a > 0 > U b > U c , the power switch tubes Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 11 , Q 12 , Q 14 are always off, Q 6 , Q 9 , Q 10 are always on, Q 13 is modulated by high-frequency PWM, Q 5 is turned on during the off period of Q 13 , and Q 5 is modulated by high-frequency PWM during the on period of Q 13 ; Q 8 is turned on during the on period of Q 13 , and Q 8 is modulated by high-frequency PWM during the off period of Q 13 ;

[0015] (2) When the grid voltage U a > U b > 0 > Uc When, power switch Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 12 、Q 13 are always off, Q 1 、Q 9 、Q 10 are always on, Q 14 is modulated by high-frequency PWM, Q 2 turns on during the off period of Q 14 and is modulated by high-frequency PWM during the on period of Q; 2 turns on during the on period of Q 14 and is modulated by high-frequency PWM during the off period of Q; 11 turns on during the on period of Q 14 and is modulated by high-frequency PWM during the off period of Q; 11 14 b a

[0016] (3) When the grid voltage U b >U a >0>U c When, power switch Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 12 、Q 13 are always off, Q 2 、Q 9 、Q 11 are always on, Q 14 is modulated by high-frequency PWM, Q 1 turns on during the off period of Q 14 and is modulated by high-frequency PWM during the on period of Q; 1 turns on during the on period of Q 14 and is modulated by high-frequency PWM during the off period of Q; 10 turns on during the on period of Q 14 and is modulated by high-frequency PWM during the off period of Q; 10 14 b a

[0017] (4) When the grid voltage U b >0>U a >U c When, power switch Q 1 、Q 2 、Q 3 、Q 5 、Q 8 、Q 10 、Q 12 、Q 14Normally off, Q 6 , Q 9 , Q 11 Normally on, Q 13 High-frequency PWM modulation, Q 4 During Q 13 Turn on during the off period, Q 4 During Q 13 High-frequency PWM modulation during the conduction period; Q 7 During Q 13 Turn on during the conduction period, Q 7 During Q 13 High-frequency PWM modulation during the off period;

[0018] (5) Grid voltage U b >0>U c >U a When, power switch Q 1 , Q 2 , Q 3 , Q 5 , Q 8 , Q 10 , Q 12 , Q 14 Normally off, Q 4 , Q 7 , Q 11 Normally on, Q 13 High-frequency PWM modulation, Q 6 During Q 13 Turn on during the off period, Q 6 During Q 13 High-frequency PWM modulation during the conduction period; Q 9 During Q 13 Turn on during the conduction period, Q 9 During Q 13 High-frequency PWM modulation during the off period;

[0019] (6) Grid voltage U b >U c >0>U a When, power switch Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 13 Normally off, Q 2 , Q 7 , Q 11 Normally on, Q 14 High-frequency PWM modulation, Q 3 During Q 14 Turn on during the off period, Q 3 During Q 14High-frequency PWM modulation during conduction; Q 12 During Q 14 Turn on during conduction, Q 12 During Q 14 High-frequency PWM modulation during turn-off;

[0020] (7) Grid voltage U c >U b >0>U a When, power switch Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 13 Always off, Q 3 、Q 7 、Q 12 Always on, Q 14 High-frequency PWM modulation, Q 2 During Q 14 Turn on during turn-off, Q 2 During Q 14 High-frequency PWM modulation during conduction; Q 11 During Q 14 Turn on during conduction, Q 11 During Q 14 High-frequency PWM modulation during turn-off;

[0021] (8) Grid voltage U c >0>U b >U a When, power switch Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 Always off, Q 4 、Q 7 、Q 12 Always on, Q 13 High-frequency PWM modulation, Q 5 During Q 13 Turn on during turn-off, Q 5 During Q 13 High-frequency PWM modulation during conduction; Q 8 During Q 13 Turn on during conduction, Q 8 During Q 13 High-frequency PWM modulation during turn-off;

[0022] (9) Grid voltage U c>0>U a >U b When, power switch tube Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 are always off, Q 5 、Q 8 、Q 12 are always on, Q 13 is modulated by high-frequency PWM, Q 4 turns on during the turn-off period of Q 13 and is modulated by high-frequency PWM during the conduction period of Q 4 turns on during the conduction period of Q 13 and is modulated by high-frequency PWM during the turn-off period of Q 7 turns on during the conduction period of Q 13 and is modulated by high-frequency PWM during the turn-off period of Q 7 turns on during the conduction period of Q 13 and is modulated by high-frequency PWM during the turn-off period of Q

[0023] (10) Grid voltage U c >U a >0>U b When, power switch tube Q 2 、Q 4 、Q 5 、Q 6 、Q 7 、Q 9 、Q 11 、Q 13 are always off, Q 3 、Q 8 、Q 12 are always on, Q 14 is modulated by high-frequency PWM, Q 1 turns on during the turn-off period of Q 14 and is modulated by high-frequency PWM during the conduction period of Q 1 turns on during the conduction period of Q 14 and is modulated by high-frequency PWM during the turn-off period of Q 10 turns on during the conduction period of Q 14 and is modulated by high-frequency PWM during the turn-off period of Q 10 turns on during the conduction period of Q 14 and is modulated by high-frequency PWM during the turn-off period of Q

[0024] (11) Grid voltage U a >U c >0>U b When, power switch tube Q 2 、Q 4 、Q 5 、Q 6 、Q 7 、Q 9 、Q11 , Q 13 Normally off, Q 1 , Q 8 , Q 10 Normally on, Q 14 High-frequency PWM modulation, Q 3 During the off period of Q 14 Turn on, Q 3 During the on period of Q 14 High-frequency PWM modulation; Q 12 During the on period of Q 14 Turn on, Q 12 During the off period of Q 14 High-frequency PWM modulation;

[0025] (12) Grid voltage U a > 0 > U c > U b When, power switch Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 11 , Q 12 , Q 14 Normally off, Q 5 , Q 8 , Q 10 Normally on, Q 13 High-frequency PWM modulation, Q 6 During the off period of Q 13 Turn on, Q 6 During the on period of Q 13 High-frequency PWM modulation; Q 9 During the on period of Q 13 Turn on, Q 9 During the off period of Q 13 High-frequency PWM modulation.

[0026] The boost modulation method of the three-phase buck-boost inverter circuit described in the present invention includes the following steps:

[0027] (1) Grid voltage U a > 0 > U b > U c When, power switch Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 8 , Q 9 , Q 11 , Q 12 Normally off, Q 6 , Q 10 , Q13 Constant conduction, Q 14 High-frequency PWM modulation, Q 5 During Q 14 Turn on during conduction, Q 5 During Q 14 High-frequency PWM modulation during the off period;

[0028] (2) Grid voltage U a >U b >0>U c When, power switch Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 10 、Q 11 、Q 12 Constant off, Q 1 、Q 9 、Q 14 Constant conduction, Q 13 High-frequency PWM modulation, Q 2 During Q 13 Turn on during conduction, Q 2 During Q 13 High-frequency PWM modulation during the off period;

[0029] (3) Grid voltage U b >U a >0>U c When, power switch Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 10 、Q 11 、Q 12 Constant off, Q 2 、Q 9 、Q 14 Constant conduction, Q 13 High-frequency PWM modulation, Q 1 During Q 13 Turn on during conduction, Q 1 During Q 13 High-frequency PWM modulation during the off period;

[0030] (4) Grid voltage U b >0>U a >U c When, power switch Q 1 、Q 2 、Q 3 、Q 5 、Q7 , Q 8 , Q 9 , Q 10 , Q 12 Normally off, Q 6 , Q 11 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 4 During the conduction period of Q 14 Turn on, Q 4 During the conduction period of Q 14 Perform high-frequency PWM modulation during the turn-off period of Q;

[0031] (5) Grid voltage U b > 0 > U c > U a When, the power switch tubes Q 1 , Q 2 , Q 3 , Q 5 , Q 7 , Q 8 , Q 9 , Q 10 , Q 12 Normally off, Q 4 , Q 11 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 6 During the conduction period of Q 14 Turn on, Q 6 During the conduction period of Q 14 Perform high-frequency PWM modulation during the turn-off period of Q;

[0032] (6) Grid voltage U b > U c > 0 > U a When, the power switch tubes Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 11 , Q 12 Normally off, Q 2 , Q 7 , Q 14 Normally on, Q 13 High-frequency PWM modulation, Q 3 During the conduction period of Q 13 Turn on, Q 3 During the conduction period of Q 13 Perform high-frequency PWM modulation during the turn-off period of Q;

[0033] (7) Grid voltage Uc >U b >0>U a When, power switch Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 3 、Q 7 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 2 turns on during the conduction period of Q 13 and is high-frequency PWM modulated during the off period of Q; 2 During the conduction period of Q 13 it turns on and is high-frequency PWM modulated during the off period of Q;

[0034] (8) Grid voltage U c >0>U b >U a When, power switch Q 1 、Q 2 、Q 3 、Q 6 、Q 7 、Q 8 、Q 9 、Q 10 、Q 11 are always off, Q 4 、Q 12 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 5 During the conduction period of Q 14 it turns on and is high-frequency PWM modulated during the off period of Q; 5 During the conduction period of Q 14 it turns on and is high-frequency PWM modulated during the off period of Q;

[0035] (9) Grid voltage U c >0>U a >U b When, power switch Q 1 、Q 2 、Q 3 、Q 6 、Q 7 、Q 8 、Q 9 、Q 10 、Q 11 are always off, Q 5 、Q 12 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q4 Turn on during the conduction period of Q 14 and perform high-frequency PWM modulation during the turn-off period of Q 4 During the conduction period of Q 14 Turn on, and perform high-frequency PWM modulation during the turn-off period of Q

[0036] (10) Grid voltage U c >U a >0>U b When this is the case, power switch tubes Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 10 , Q 11 , Q 12 are always off, Q 3 , Q 8 , Q 14 are always on, Q 13 Performs high-frequency PWM modulation, Q 1 During the conduction period of Q 13 Turn on, and perform high-frequency PWM modulation during the turn-off period of Q 1 During the conduction period of Q 13 Turn on, and perform high-frequency PWM modulation during the turn-off period of Q

[0037] (11) Grid voltage U a >U c >0>U b When this is the case, power switch tubes Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 10 , Q 11 , Q 12 are always off, Q 1 , Q 8 , Q 14 are always on, Q 13 Performs high-frequency PWM modulation, Q 3 During the conduction period of Q 13 Turn on, and perform high-frequency PWM modulation during the turn-off period of Q 3 During the conduction period of Q 13 Turn on, and perform high-frequency PWM modulation during the turn-off period of Q

[0038] (12) Grid voltage U a >0>U c >U b When this is the case, power switch tubes Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 8 , Q9 , Q 11 , Q 12 Normally off, Q 5 , Q 10 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 6 During the conduction of Q 14 Turn on, Q 6 During the conduction of Q 14 During the off period of Q, perform high-frequency PWM modulation.

[0039] The buck-boost modulation method of the three-phase buck-boost inverter circuit described in the present invention includes the following steps:

[0040] (1) When the grid voltage U a > 0 > U b > U c , the power switch tubes Q 1 -Q 6 , Q 7 , Q 11 , Q 12 Are normally off, Q 9 , Q 10 , Q 14 Are normally on, Q 13 High-frequency PWM modulation, Q 8 During the conduction of Q 13 Turn on. When Q 13 Turns off, Q 8 Performs high-frequency PWM modulation;

[0041] (2) When the grid voltage U a > U b > 0 > U c , the power switch tubes Q 1 -Q 6 , Q 7 , Q 8 , Q 12 Are normally off, Q 9 , Q 10 , Q 13 Are normally on, Q 14 High-frequency PWM modulation, Q 11 During the conduction of Q 14 Turn on. When Q 14 Turns off, Q 11 Performs high-frequency PWM modulation;

[0042] (3) When the grid voltage U b > U a > 0 > U c , the power switch tubes Q 1 -Q 6 , Q 7 , Q8 , Q 12 Normally off, Q 9 , Q 11 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 10 During the conduction period of Q 14 turn on, when Q 14 turns off, Q 10 High-frequency PWM modulation;

[0043] (4) Grid voltage U b > 0 > U a > U c When, the power switch Q 1 -Q 6 , Q 8 , Q 10 , Q 12 Normally off, Q 9 , Q 11 , Q 14 Normally on, Q 13 High-frequency PWM modulation, Q 7 During the conduction period of Q 13 turn on, when Q 13 turns off, Q 7 High-frequency PWM modulation;

[0044] (5) Grid voltage U b > 0 > U c > U a When, the power switch Q 1 -Q 6 , Q 8 , Q 10 , Q 12 Normally off, Q 7 , Q 11 , Q 14 Normally on, Q 13 High-frequency PWM modulation, Q 9 During the conduction period of Q 13 turn on, when Q 13 turns off, Q 9 High-frequency PWM modulation;

[0045] (6) Grid voltage U b > U c > 0 > U a When, the power switch Q 1 -Q 6 , Q 8 , Q 9 , Q 10 Normally off, Q 7 , Q 11 , Q 13Normal conduction, Q 14 High-frequency PWM modulation, Q 12 During Q 14 Turn on during conduction. When Q 14 Turn off, Q 12 High-frequency PWM modulation;

[0046] (7) Grid voltage U c >U b >0>U a When, the power switch tube Q 1 -Q 6 、Q 8 、Q 9 、Q 10 Normally off, Q 7 、Q 12 、Q 13 Normal conduction, Q 14 High-frequency PWM modulation, Q 11 During Q 14 Turn on during conduction. When Q 14 Turn off, Q 11 High-frequency PWM modulation;

[0047] (8) Grid voltage U c >0>U b >U a When, the power switch tube Q 1 -Q 6 、Q 9 、Q 10 、Q 11 Normally off, Q 7 、Q 12 、Q 14 Normal conduction, Q 13 High-frequency PWM modulation, Q 8 During Q 13 Turn on during conduction. When Q 13 Turn off, Q 8 High-frequency PWM modulation;

[0048] (9) Grid voltage U c >0>U a >U b When, the power switch tube Q 1 -Q 6 、Q 9 、Q 10 、Q 11 Normally off, Q 8 、Q 12 、Q 14 Normal conduction, Q 13 High-frequency PWM modulation, Q 7 During Q 13 Turn on during conduction. When Q 13When off, Q 7 High-frequency PWM modulation;

[0049] (10) Grid voltage U c >U a >0>U b When, the power switch Q 1 -Q 6 、Q 7 、Q 9 、Q 11 Are always off, Q 8 、Q 12 、Q 13 Are always on, Q 14 High-frequency PWM modulation, Q 10 Turns on during the conduction of Q 14 , and when Q 14 turns off, Q 10 High-frequency PWM modulation;

[0050] (11) Grid voltage U a >U c >0>U b When, the power switch Q 1 -Q 6 、Q 7 、Q 9 、Q 11 Are always off, Q 8 、Q 10 、Q 13 Are always on, Q 14 High-frequency PWM modulation, Q 12 Turns on during the conduction of Q 14 , and when Q 14 turns off, Q 12 High-frequency PWM modulation;

[0051] (12) Grid voltage U a >0>U c >U b When, the power switch Q 1 -Q 6 、Q 7 、Q 11 、Q 12 Are always off, Q 8 、Q 10 、Q 14 Are always on, Q 13 High-frequency PWM modulation, Q 9 Turns on during the conduction of Q 13 , and when Q 13 turns off, Q 9 High-frequency PWM modulation.

[0052] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are as follows: (1) It is applicable to occasions with a wide range of input voltage variations. (2) The volume, weight, and cost of the inverter are reduced, and the power density is increased. (3) The multi-mode modulation method maximally utilizes the DC input voltage, reduces the number of switching tubes operating at high frequencies, decreases the switching loss, and improves the conversion efficiency. Description of the Drawings

[0053] Figure 1 is a schematic circuit diagram of the present invention;

[0054] Figures 2(a) to 2(d) is U a >0>U b >U c when it is the current loop mode of step-down inversion;

[0055] Figures 2(e) to 2(h) is U a <0<U b <U c when it is the current loop mode of step-down inversion;

[0056] Figure 2(i) is a working state diagram of each switching tube within one cycle of step-down inversion;

[0057] Figure 2(j) is for step-down inversion U a >0>U b >U c when Q 13 、Q 5 、Q 8 partial enlarged view of the drive signals;

[0058] Figures 3(a) to 3(c) is U a >0>U b >U c when it is the current loop mode of boost inversion;

[0059] Figures 3(d) to 3(f) is U a <0<U b <U c when it is the current loop mode of boost inversion;

[0060] Figure 3(g) is a working state diagram of each switching tube within one cycle of boost inversion;

[0061] Figure 3(h) is for boost inversion U a >0>U b >U c when Q 14 、Q 5 partial enlarged view of the drive signals;

[0062] Figures 4(a) to 4(c) is U a>0>U b >U c Current loop mode of buck-boost inversion

[0063] Figures 4(d) to 4(f) is U a <0<U b <U c Current loop mode of buck-boost inversion

[0064] Figure 4(g) is the working state diagram of each switching tube within one period of buck-boost inversion

[0065] Figure 4(h) is for buck-boost inversion U a >0>U b >U c when Q 13 、Q 8 Partial enlarged view of drive signals Specific implementation mode

[0066] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings

[0067] As can be seen from Figure 1 , the three-phase buck-boost inverter circuit described in the present invention includes: a DC power supply circuit 1, a chopper circuit 2, and a three-phase voltage source circuit 3. Among them: the DC power supply circuit 1 is composed of a DC voltage source E; the chopper circuit 2 includes power switching tubes Q 1 ~Q 14 , diodes D 1 ~D 14 and an inductor L 1 , and the emitters of the power switching tubes Q 1 ~Q 14 are respectively connected to the anodes of the diodes D 1 ~D 14 , the collectors of the power switching tubes Q 4 、Q 7 are connected to the cathodes of the diodes D 1 、D 10 , the collectors of the power switching tubes Q 5 、Q 8 are connected to the cathodes of the diodes D 2 、D 11 , the collectors of the power switching tubes Q 6 、Q 9 are connected to the cathodes of the diodes D 3 、D 12 , the collectors of the power switching tubes Q 1 、Q 2 、Q 3 、Q 13 are connected, and the cathodes of the diodes D 4 、D 5, D 6 , D 14 is connected to the cathode of diode D 7 , D 8 , D 9 , D 13 After the cathodes are connected, they are connected to one end of inductor L 1 The collector electrodes of power switch transistors Q 10 , Q 11 , Q 12 , Q 14 are connected and then connected to the other end of inductor L 1 The three-phase voltage source circuit 3 includes three sinusoidal voltage sources with initial phases of a, b, and c that differ by 120° in sequence. One end of the a, b, and c three-phase voltage sources is connected together; the positive pole of the DC voltage source E of the DC power supply circuit 1 is connected to the collector electrodes of the power switch transistors Q 1 , Q 2 , Q 3 , Q 13 of the chopper circuit 2, and the negative pole of the DC voltage source E of the DC power supply circuit 1 is connected to the cathodes of the diodes D 4 , D 5 , D 6 , D 14 of the chopper circuit 2.

[0068] The other end of the a-phase voltage source of the three-phase voltage source circuit 3 is connected to the collector electrodes of the power switch transistors Q 4 , Q 7 and the cathodes of the diodes D 1 , D 10 of the chopper circuit 2. The other end of the b-phase voltage source of the three-phase voltage source circuit 3 is connected to the collector electrodes of the power switch transistors Q 5 , Q 8 and the cathodes of the diodes D 2 , D 11 of the chopper circuit 2. The other end of the c-phase voltage source of the three-phase voltage source circuit 3 is connected to the collector electrodes of the power switch transistors Q 6 , Q 9 and the cathodes of the diodes D 3 , D 12 of the chopper circuit 2.

[0069] The power switch transistors Q 1 ~Q 14 are IGBTs or MOSFETs.

[0070] A filter is provided between the three-phase voltage source circuit and the chopper circuit, or the filter can be removed.

[0071] The buck modulation method of the three-phase buck-boost inverter circuit described in the present invention includes the following steps:

[0072] (1) Grid voltage U a >0>U b >U c When, power switch tubes Q 1 、Q 2 、Q 3 、Q 4 、Q 7 、Q 11 、Q 12 、Q 14 are always off, Q 6 、Q 9 、Q 10 are always on, Q 13 is high-frequency PWM modulated, Q 5 turns on during the off period of Q 13 、Q 5 turns on during the on period of Q 13 and is high-frequency PWM modulated during the on period of Q; 8 turns on during the on period of Q 13 、Q 8 turns on during the off period of Q 13 and is high-frequency PWM modulated during the off period of Q;

[0073] (2) Grid voltage U a >U b >0>U c When, power switch tubes Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 12 、Q 13 are always off, Q 1 、Q 9 、Q 10 are always on, Q 14 is high-frequency PWM modulated, Q 2 turns on during the off period of Q 14 、Q 2 turns on during the on period of Q 14 and is high-frequency PWM modulated during the on period of Q; 11 turns on during the on period of Q 14 、Q 11 turns on during the off period of Q 14 and is high-frequency PWM modulated during the off period of Q;

[0074] (3) Grid voltage U b >U a >0>U c When, power switch tubes Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q8 , Q 12 , Q 13 Normally off, Q 2 , Q 9 , Q 11 Normally on, Q 14 High-frequency PWM modulation, Q 1 During the off period of Q 14 Turn on, Q 1 During the on period of Q 14 High-frequency PWM modulation; Q 10 During the on period of Q 14 Turn on, Q 10 During the off period of Q 14 High-frequency PWM modulation;

[0075] (4) Grid voltage U b > 0 > U a > U c When, power switch Q 1 , Q 2 , Q 3 , Q 5 , Q 8 , Q 10 , Q 12 , Q 14 Normally off, Q 6 , Q 9 , Q 11 Normally on, Q 13 High-frequency PWM modulation, Q 4 During the off period of Q 13 Turn on, Q 4 During the on period of Q 13 High-frequency PWM modulation; Q 7 During the on period of Q 13 Turn on, Q 7 During the off period of Q 13 High-frequency PWM modulation;

[0076] (5) Grid voltage U b > 0 > U c > U a When, power switch Q 1 , Q 2 , Q 3 , Q 5 , Q 8 , Q 10 , Q 12 , Q 14 Normally off, Q 4 , Q 7 , Q 11 Normally on, Q 13 High-frequency PWM modulation, Q 6 During the off period of Q13 Turn on during the off period, Q 6 During Q 13 High-frequency PWM modulation during conduction; Q 9 During Q 13 Turn on during the conduction period, Q 9 During Q 13 High-frequency PWM modulation during the off period;

[0077] (6) Grid voltage U b >U c >0>U a When, power switch Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 13 Always off, Q 2 、Q 7 、Q 11 Always on, Q 14 High-frequency PWM modulation, Q 3 During Q 14 Turn on during the off period, Q 3 During Q 14 High-frequency PWM modulation during conduction; Q 12 During Q 14 Turn on during the conduction period, Q 12 During Q 14 High-frequency PWM modulation during the off period;

[0078] (7) Grid voltage U c >U b >0>U a When, power switch Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 13 Always off, Q 3 、Q 7 、Q 12 Always on, Q 14 High-frequency PWM modulation, Q 2 During Q 14 Turn on during the off period, Q 2 During Q 14 High-frequency PWM modulation during conduction; Q 11 During Q 14 Turn on during the conduction period, Q 11 During Q 14 High-frequency PWM modulation during the off period;

[0079] (8) Grid voltage U c > 0 > U b > U a When, power switch tubes Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 are always off, Q 4 、Q 7 、Q 12 are always on, Q 13 is high-frequency PWM modulated, Q 5 During the turn-off period of Q 13 it turns on, Q 5 During the conduction period of Q 13 it is high-frequency PWM modulated; Q 8 During the conduction period of Q 13 it turns on, Q 8 During the turn-off period of Q 13 it is high-frequency PWM modulated;

[0080] (9) Grid voltage U c > 0 > U a > U b When, power switch tubes Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 are always off, Q 5 、Q 8 、Q 12 are always on, Q 13 is high-frequency PWM modulated, Q 4 During the turn-off period of Q 13 it turns on, Q 4 During the conduction period of Q 13 it is high-frequency PWM modulated; Q 7 During the conduction period of Q 13 it turns on, Q 7 During the turn-off period of Q 13 it is high-frequency PWM modulated;

[0081] (10) Grid voltage U c > U a > 0 > U b When, power switch tubes Q 2 、Q 4 、Q 5 、Q6 , Q 7 , Q 9 , Q 11 , Q 13 Normally off, Q 3 , Q 8 , Q 12 Normally on, Q 14 High-frequency PWM modulation, Q 1 During Q 14 Turn on during the off period, Q 1 During Q 14 High-frequency PWM modulation during the on period; Q 10 During Q 14 Turn on during the on period, Q 10 During Q 14 High-frequency PWM modulation during the off period;

[0082] (11) Grid voltage U a > U c > 0 > U b When, power switch Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 11 , Q 13 Normally off, Q 1 , Q 8 , Q 10 Normally on, Q 14 High-frequency PWM modulation, Q 3 During Q 14 Turn on during the off period, Q 3 During Q 14 High-frequency PWM modulation during the on period; Q 12 During Q 14 Turn on during the on period, Q 12 During Q 14 High-frequency PWM modulation during the off period;

[0083] (12) Grid voltage U a > 0 > U c > U b When, power switch Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 11 , Q 12 , Q 14 Normally off, Q 5 , Q 8 , Q 10 Normally on, Q 13High-frequency PWM modulation, Q 6 During the turn-off period of Q, it is turned on. 13 During the turn-off period of Q, it is turned on. 6 During the conduction period of Q, high-frequency PWM modulation is carried out. 13 During the conduction period of Q, high-frequency PWM modulation is carried out. 9 During the conduction period of Q, it is turned on. 13 During the conduction period of Q, it is turned on. 9 During the turn-off period of Q, high-frequency PWM modulation is carried out. 13 During the turn-off period of Q, high-frequency PWM modulation is carried out.

[0084] To simplify the analysis, this embodiment introduces the case where the three-phase grid voltages are symmetrical. For other grid voltage conditions, those skilled in the art should be able to understand a control method for realizing buck / boost / buck-boost output in this embodiment. Since the three phases are symmetrical, then i a +i b +i c =0, and the absolute value of the current of the out-of-phase phase is equal to the sum of the absolute values of the currents of the in-phase phases.

[0085] For convenience of analysis, the phase angle of phase b is defined as 0° at the moment when the a-phase is at the positive peak value, and in combination with the variation law of the three-phase grid voltages, the working states of each power switch tube within one cycle starting from being 0° in the buck-inverter mode are shown in Fig. 2(i). Fig. 2(j) is a partial enlarged view of the drive signals of Q when U a >0>U b >U c . 13 、Q 5 、Q 8 The detailed working process during buck inversion is as follows: Taking U

[0086] a >0>U b >U c and U a <0<U b <U c as an example for analysis.

[0087] When the grid voltage U a >0>U b >U c 1 、Q 2 、Q 3 、Q 4 、Q 7 、Q 11 、Q 12 、Q 14 、Q 6 are always off, Q 9 、Q 10 、Q 13 are always on, Q 13High-frequency PWM modulation, the current of phase a flows into the power grid, and the currents of phases b and c flow out of the power grid. The power switch tube Q 5 turns on during the turn-off period of Q 13 . Since Q 1 , Q 2 , Q 3 , Q 13 are turned off, the branch where Q 5 is located cannot form a current loop, and no current flows through Q 5 . Therefore, Q 5 can achieve zero-current turn-on. When Q 13 is conducting, the inductor L 1 stores energy. Q 5 performs high-frequency PWM modulation. The operating modes of the inverter are shown in Figures 2(a) and 2(b); the power switch tube Q 8 turns on during the conduction period of Q 13 . Since the cathode potential of D 13 is relatively high, the current does not flow through Q 8 . Therefore, Q 8 can also achieve zero-current turn-on. When Q 13 is turned off, the inductor L 1 releases energy. At this time, Q 8 performs high-frequency PWM modulation. The operating modes of the inverter are shown in Figures 2(c) and 2(d).

[0088] When the grid voltage U a <0 < U b < U c , the power switch tubes Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 13 are always off, and Q 3 , Q 7 , Q 12 are always on. Q 14 performs high-frequency PWM modulation. The current of phase a flows out of the power grid, and the currents of phases b and c flow into the power grid. The power switch tube Q 2 turns on during the turn-off period of Q 14 . Since Q 4 , Q 5 , Q 6 , Q 14 are turned off, the branch where Q 2 is located cannot form a loop, and no current flows through Q 2 . Therefore, Q 2 can achieve zero-current turn-on. When Q 14 is conducting, the inductor L 1 stores energy. At this time, Q2 High-frequency PWM modulation, the rest of the power switching transistors are turned off, and the operating modes of the inverter are shown in Figures 2(e) and 2(f); power switching transistor Q 11 During the conduction of Q 14 is turned on. Since Q 5 is turned off and no current flows through Q 11 , so Q 11 can also achieve zero-current turn-on. When Q 14 is turned off, the inductor L 1 releases energy. At this time, Q 11 is under high-frequency PWM modulation. The operating modes of the inverter are shown in Figures 2(g) and 2(h).

[0089] The boost modulation method of the three-phase buck-boost inverter circuit according to the present invention includes the following steps:

[0090] (1) When the grid voltage U a > 0 > U b > U c , the power switching transistors Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 8 , Q 9 , Q 11 , Q 12 are always off, Q 6 , Q 10 , Q 13 are always on, Q 14 is under high-frequency PWM modulation, Q 5 is turned on during the conduction of Q 14 , Q 5 is under high-frequency PWM modulation during the turn-off of Q 14 ;

[0091] (2) When the grid voltage U a > U b > 0 > U c , the power switching transistors Q 3 , Q 4 , Q 5 , Q 6 , Q 7 , Q 8 , Q 10 , Q 11 , Q 12 are always off, Q 1 , Q 9 , Q 14 are always on, Q 13 is under high-frequency PWM modulation, Q 2 is turned on during the conduction of Q 13 , Q2 During the turn-off period of Q, high-frequency PWM modulation; 13 During the turn-off period of Q, high-frequency PWM modulation;

[0092] (3) Grid voltage U b > U a > 0> U c When, power switch Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 10 、Q 11 、Q 12 are always off, Q 2 、Q 9 、Q 14 are always on, Q 13 High-frequency PWM modulation, Q 1 During the turn-on period of Q, turn on, Q 13 During the turn-on period of Q, turn on, Q 1 During the turn-off period of Q, high-frequency PWM modulation; 13 During the turn-off period of Q, high-frequency PWM modulation;

[0093] (4) Grid voltage U b > 0> U a > U c When, power switch Q 1 、Q 2 、Q 3 、Q 5 、Q 7 、Q 8 、Q 9 、Q 10 、Q 12 are always off, Q 6 、Q 11 、Q 13 are always on, Q 14 High-frequency PWM modulation, Q 4 During the turn-on period of Q, turn on, Q 14 During the turn-on period of Q, turn on, Q 4 During the turn-off period of Q, high-frequency PWM modulation; 14 During the turn-off period of Q, high-frequency PWM modulation;

[0094] (5) Grid voltage U b > 0> U c > U a When, power switch Q 1 、Q 2 、Q 3 、Q 5 、Q 7 、Q 8 、Q 9 、Q 10 、Q 12 are always off, Q4 , Q 11 , Q 13 Normally conducting, Q 14 High-frequency PWM modulation, Q 6 During Q 14 Turn on during conduction, Q 6 During Q 14 Perform high-frequency PWM modulation during the off period;

[0095] (6) Grid voltage U b > U c > 0 > U a When, power switch Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 11 , Q 12 Normally off, Q 2 , Q 7 , Q 14 Normally conducting, Q 13 High-frequency PWM modulation, Q 3 During Q 13 Turn on during conduction, Q 3 During Q 13 Perform high-frequency PWM modulation during the off period;

[0096] (7) Grid voltage U c > U b > 0 > U a When, power switch Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 11 , Q 12 Normally off, Q 3 , Q 7 , Q 14 Normally conducting, Q 13 High-frequency PWM modulation, Q 2 During Q 13 Turn on during conduction, Q 2 During Q 13 Perform high-frequency PWM modulation during the off period;

[0097] (8) Grid voltage U c > 0 > U b > U a When, power switch Q 1 , Q 2 , Q3 , Q 6 , Q 7 , Q 8 , Q 9 , Q 10 , Q 11 Normally off, Q 4 , Q 12 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 5 During the conduction period of Q 14 Turn on, Q 5 During the conduction period of Q 14 High-frequency PWM modulation during the turn-off period;

[0098] (9) Grid voltage U c > 0 > U a > U b When, power switch Q 1 , Q 2 , Q 3 , Q 6 , Q 7 , Q 8 , Q 9 , Q 10 , Q 11 Normally off, Q 5 , Q 12 , Q 13 Normally on, Q 14 High-frequency PWM modulation, Q 4 During the conduction period of Q 14 Turn on, Q 4 During the conduction period of Q 14 High-frequency PWM modulation during the turn-off period;

[0099] (10) Grid voltage U c > U a > 0 > U b When, power switch Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 10 , Q 11 , Q 12 Normally off, Q 3 , Q 8 , Q 14 Normally on, Q 13 High-frequency PWM modulation, Q 1 During the conduction period of Q 13 Turn on, Q 1 During the conduction period of Q 13 High-frequency PWM modulation during the turn-off period;

[0100] (11) Grid voltage U a >U c >0>U b When, power switch tubes Q 2 、Q 4 、Q 5 、Q 6 、Q 7 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 1 、Q 8 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 3 turns on during the conduction period of Q 13 and is high-frequency PWM modulated during the off period of Q 3 During the conduction period of Q 13 turns on and is high-frequency PWM modulated during the off period of Q;

[0101] (12) Grid voltage U a >0>U c >U b When, power switch tubes Q 1 、Q 2 、Q 3 、Q 4 、Q 7 、Q 8 、Q 9 、Q 11 、Q 12 are always off, Q 5 、Q 10 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 6 turns on during the conduction period of Q 14 and is high-frequency PWM modulated during the off period of Q 6 During the conduction period of Q 14 turns on and is high-frequency PWM modulated during the off period of Q.

[0102] Combined with the variation law of the three-phase grid voltage, the working states of each power switch tube within one cycle starting from 0° in the boost-inversion mode are shown in Fig. 3(g). Fig. 3(h) is the partial enlarged view of the drive signals of Q a >0>U b >U c When, Q 14 、Q 5 The detailed working process during boost inversion is as follows: Taking U a >0>U b >U c and U a <0<Ub <U c is taken as an example for analysis.

[0103] When the grid voltage U a >0>U b >U c is the case, the power switch transistors Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 8 , Q 9 , Q 11 , Q 12 are always off, Q 6 , Q 10 , Q 13 are always on, Q 14 is under high-frequency PWM modulation. When Q 14 is on, the inductor L 1 stores energy, and the operating mode of the inverter is shown in Figure 3(a); the power switch transistor Q 5 turns on during the conduction period of Q 14 . There is no current flowing through Q 5 , and Q 5 can achieve zero-current turn-on. When Q 14 turns off, the inductor L 1 and the power supply E release energy simultaneously. The current of phase a flows into the grid, and the currents of phases b and c flow out of the grid. At this time, Q 5 is under high-frequency PWM modulation, and the operating modes of the inverter are shown in Figures 3(b) and 3(c).

[0104] When the grid voltage U a <0<U b <U c is the case, the power switch transistors Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 11 , Q 12 are always off, Q 3 , Q 7 , Q 14 are always on, Q 13 is under high-frequency PWM modulation. When Q 13 is on, the inductor L 1 stores energy, and the operating mode of the inverter is shown in Figure 3(d); the power switch transistor Q 2 turns on during the conduction period of Q 13 . Similarly, there is no current flowing through Q 2 , and Q 2Zero-current turn-on can also be achieved, Q 13 When turning off, the inductor L 1 and the power supply E release energy simultaneously. The current of phase a flows out of the power grid, and the currents of phases b and c flow into the power grid. At this time, Q 2 High-frequency PWM modulation is performed, and the operating modes of the inverter are shown in Figures 3(e) and 3(f).

[0105] The buck-boost modulation method of the three-phase buck-boost inverter circuit described in the present invention includes the following steps:

[0106] (1) When the grid voltage U a >0>U b >U c the power switch tubes Q 1 -Q 6 、Q 7 、Q 11 、Q 12 are always off, Q 9 、Q 10 、Q 14 are always on, Q 13 High-frequency PWM modulation is performed, and Q 8 turns on during the conduction period of Q 13 . When Q 13 turns off, Q 8 performs high-frequency PWM modulation;

[0107] (2) When the grid voltage U a >U b >0>U c the power switch tubes Q 1 -Q 6 、Q 7 、Q 8 、Q 12 are always off, Q 9 、Q 10 、Q 13 are always on, Q 14 High-frequency PWM modulation is performed, and Q 11 turns on during the conduction period of Q 14 . When Q 14 turns off, Q 11 performs high-frequency PWM modulation;

[0108] (3) When the grid voltage U b >U a >0>U c the power switch tubes Q 1 -Q 6 、Q 7 、Q 8 、Q 12 are always off, Q 9 、Q 11 、Q13 Constant conduction, Q 14 High-frequency PWM modulation, Q 10 During Q 14 Turn on during conduction, when Q 14 When turning off, Q 10 High-frequency PWM modulation;

[0109] (4) Grid voltage U b >0>U a >U c When, the power switch Q 1 -Q 6 、Q 8 、Q 10 、Q 12 Constant off, Q 9 、Q 11 、Q 14 Constant conduction, Q 13 High-frequency PWM modulation, Q 7 During Q 13 Turn on during conduction, when Q 13 When turning off, Q 7 High-frequency PWM modulation;

[0110] (5) Grid voltage U b >0>U c >U a When, the power switch Q 1 -Q 6 、Q 8 、Q 10 、Q 12 Constant off, Q 7 、Q 11 、Q 14 Constant conduction, Q 13 High-frequency PWM modulation, Q 9 During Q 13 Turn on during conduction, when Q 13 When turning off, Q 9 High-frequency PWM modulation;

[0111] (6) Grid voltage U b >U c >0>U a When, the power switch Q 1 -Q 6 、Q 8 、Q 9 、Q 10 Constant off, Q 7 、Q 11 、Q 13 Constant conduction, Q 14 High-frequency PWM modulation, Q 12 During Q 14 Turn on during conduction, when Q14 When turned off, Q 12 High-frequency PWM modulation;

[0112] (7) Grid voltage U c >U b >0>U a When, power switch Q 1 -Q 6 、Q 8 、Q 9 、Q 10 Are always off, Q 7 、Q 12 、Q 13 Are always on, Q 14 High-frequency PWM modulation, Q 11 Turns on during the conduction of Q 14 When Q is turned off, Q 14 When turned off, Q 11 High-frequency PWM modulation;

[0113] (8) Grid voltage U c >0>U b >U a When, power switch Q 1 -Q 6 、Q 9 、Q 10 、Q 11 Are always off, Q 7 、Q 12 、Q 14 Are always on, Q 13 High-frequency PWM modulation, Q 8 Turns on during the conduction of Q 13 When Q is turned off, Q 13 When turned off, Q 8 High-frequency PWM modulation;

[0114] (9) Grid voltage U c >0>U a >U b When, power switch Q 1 -Q 6 、Q 9 、Q 10 、Q 11 Are always off, Q 8 、Q 12 、Q 14 Are always on, Q 13 High-frequency PWM modulation, Q 7 Turns on during the conduction of Q 13 When Q is turned off, Q 13 When turned off, Q 7 High-frequency PWM modulation;

[0115] (10) Grid voltage Uc >U a >0>U b When, power switch Q 1 -Q 6 and Q 7 and Q 9 and Q 11 are always off, Q 8 and Q 12 and Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 10 turns on during the conduction period of Q 14 When Q 14 turns off, Q 10 is modulated by high-frequency PWM;

[0116] (11) Grid voltage U a >U c >0>U b When, power switch Q 1 -Q 6 and Q 7 and Q 9 and Q 11 are always off, Q 8 and Q 10 and Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 12 turns on during the conduction period of Q 14 When Q 14 turns off, Q 12 is modulated by high-frequency PWM;

[0117] (12) Grid voltage U a >0>U c >U b When, power switch Q 1 -Q 6 and Q 7 and Q 11 and Q 12 are always off, Q 8 and Q 10 and Q 14 are always on, Q 13 is modulated by high-frequency PWM, Q 9 turns on during the conduction period of Q 13 When Q 13 turns off, Q 9 is modulated by high-frequency PWM.

[0118] Combined with the variation law of three-phase grid voltage, the working states of each power switch in a cycle of the buck-boost inverter mode starting from 0° are shown in Fig. 4(g). Fig. 4(h) is for the buck-boost inverter mode Ua >0>U b >U c When Q 13 and Q 8 Partial enlarged view of the drive signal. The power switch tube Q in the buck-boost mode 1 to Q 6 are always in the off state.

[0119] Taking U a >0>U b >U c and U a <0<U b <U c as an example for analysis, when U a >0>U b >U c the power switch tubes Q 1 and Q 2 and Q 3 and Q 4 and Q 5 and Q 6 and Q 7 and Q 11 and Q 12 are always off, Q 9 and Q 10 and Q 14 are always on, Q 13 is under high-frequency PWM modulation. When Q 13 conducts, the inductor L 1 stores energy, and the operating mode of the inverter is shown in Fig. 4(a). Q 8 turns on during the conduction period of Q 13 . Since the cathode potential of D 13 is relatively high, the current does not flow through Q 8 , so Q 8 can achieve zero-current turn-on. When Q 13 turns off, the inductor L 1 releases energy, the a-phase current flows into the grid, and the b-phase and c-phase currents flow out of the grid. At this time, Q 8 is under high-frequency PWM modulation, and the operating modes of the inverter are shown in Figs. 4(b) and 4(c).

[0120] When U a <0<U b <U c the power switch tubes Q 1 and Q 2 and Q 3 and Q 4 and Q 5 and Q 6 and Q 8 and Q 9 and Q 10Normally off, Q 7 , Q 12 , Q 13 Normally on, Q 14 High-frequency PWM modulation. When Q 14 conducts, the inductor L 1 stores energy, and the operating mode of the inverter is as shown in Figure 4(d), Q 11 turns on during the conduction of Q 14 . Since Q 5 turns off, the branch where Q 11 is located cannot form a current loop, and no current flows through Q 11 , so Q 11 can achieve zero-current turn-on. When Q 14 turns off, the inductor L 1 releases energy, the a-phase current flows out of the grid, and the b-phase and c-phase currents flow into the grid. At this time, Q 11 is under high-frequency PWM modulation, and the operating modes of the inverter are as shown in Figures 4(e) and 4(f).

Claims

1. A buck modulation method for a three-phase buck-boost inverter circuit, Characterized in that: It includes the following steps: (1) Grid voltage U a > 0 > U b > U c When, power switch tubes Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 11 , Q 12 , Q 14 Are always off, Q 6 , Q 9 , Q 10 Are always on, Q 13 High - frequency PWM modulation, Q 5 Turns on during the off period of Q 13 , Q 5 Turns on during the on period of Q 13 High - frequency PWM modulation; Q 8 Turns on during the on period of Q 13 , Q 8 Turns on during the off period of Q 13 High - frequency PWM modulation; (2) Grid voltage U a >U b >0>U c When, power switch tubes Q 3 , Q 4 , Q 5 , Q 6 , Q 7 , Q 8 , Q 12 , Q 13 are always off, Q 1 , Q 9 , Q 10 are always on, Q 14 is under high-frequency PWM modulation, Q 2 turns on during the off period of Q 14 , Q 2 is under high-frequency PWM modulation during the on period of Q 14 ; Q 11 turns on during the on period of Q 14 , Q 11 is under high-frequency PWM modulation during the off period of Q 14 ​ (3) Grid voltage U b >U a >0>U c When, the power switch tubes Q 3 , Q 4 , Q 5 , Q 6 , Q 7 , Q 8 , Q 12 , Q 13 are always off, Q 2 , Q 9 , Q 11 are always on, Q 14 is high-frequency PWM modulated, Q 1 turns on during the off period of Q 14 , Q 1 is high-frequency PWM modulated during the on period of Q 14 ; Q 10 turns on during the on period of Q 14 , Q 10 is high-frequency PWM modulated during the off period of Q 14 ; (4) Grid voltage U b >0>U a >U c When, power switch transistors Q 1 、Q 2 、Q 3 、Q 5 、Q 8 、Q 10 、Q 12 、Q 14 are always off, Q 6 、Q 9 、Q 11 are always on, Q 13 is high-frequency PWM modulated, Q 4 turns on during the off period of Q 13 and is high-frequency PWM modulated during the on period of Q 4 turns on during the on period of Q 13 and is high-frequency PWM modulated during the off period of Q; Q 7 turns on during the on period of Q 13 and is high-frequency PWM modulated during the off period of Q 7 ; Q 13 turns on during the off period of Q and is high-frequency PWM modulated; (5) Grid voltage U b >0>U c >U a When, the power switch tubes Q 1 , Q 2 , Q 3 , Q 5 , Q 8 , Q 10 , Q 12 , Q 14 are always off, Q 4 , Q 7 , Q 11 are always on, Q 13 is high-frequency PWM modulated, Q 6 turns on during the turn-off period of Q 13 , Q 6 turns on during the conduction period of Q 13 and is high-frequency PWM modulated during the conduction period; Q 9 turns on during the conduction period of Q 13 , Q 9 turns on during the turn-off period of Q 13 and is high-frequency PWM modulated during the turn-off period; (6) Grid voltage U b >U c >0>U a When, power switch tubes Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 13 are always off, Q 2 , Q 7 , Q 11 are always on, Q 14 is high-frequency PWM modulated, Q 3 turns on during the off period of Q 14 , Q 3 turns on during the on period of Q 14 and is high-frequency PWM modulated during the on period of Q; Q 12 turns on during the on period of Q 14 , Q 12 turns on during the off period of Q 14 and is high-frequency PWM modulated during the off period of Q; (7) Grid voltage U c >U b >0>U a When, power switch tubes Q 1 , Q 4 , Q 5 , Q 6 , Q 8 , Q 9 , Q 10 , Q 13 are always off, Q 3 , Q 7 , Q 12 are always on, Q 14 is high-frequency PWM modulated, Q 2 turns on during the turn-off period of Q 14 , Q 2 is high-frequency PWM modulated during the conduction period of Q 14 ; Q 11 turns on during the conduction period of Q 14 , Q 11 is high-frequency PWM modulated during the turn-off period of Q 14 ; (8) Grid voltage U c > 0 > U b > U a When, power switch tubes Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 are always off, Q 4 、Q 7 、Q 12 are always on, Q 13 is high-frequency PWM modulated, Q 5 turns on during the off period of Q 13 and is high-frequency PWM modulated during the on period of Q 5 turns on during the on period of Q 13 and is high-frequency PWM modulated during the off period of Q; Q 8 turns on during the on period of Q 13 and is high-frequency PWM modulated during the off period of Q 8 、Q 13 ​ (9) Grid voltage U c > 0 > U a > U b When, power switch tubes Q 1 、Q 2 、Q 3 、Q 6 、Q 9 、Q 10 、Q 11 、Q 14 are always off, Q 5 、Q 8 、Q 12 are always on, Q 13 is high-frequency PWM modulated, Q 4 is turned on during the turn-off period of Q 13 and is high-frequency PWM modulated during the conduction period of Q 4 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the turn-off period of Q 7 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the turn-off period of Q 7 is turned on during the turn-off period of Q 13 and is high-frequency PWM modulated during the conduction period of Q (10) Grid voltage U c >U a >0>U b When, power switch tubes Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 11 , Q 13 are always off, Q 3 , Q 8 , Q 12 are always on, Q 14 is high-frequency PWM modulated, Q 1 turns on during the off period of Q 14 , Q 1 turns on during the on period of Q 14 and is high-frequency PWM modulated during the on period of Q; Q 10 turns on during the on period of Q 14 , Q 10 turns on during the off period of Q 14 and is high-frequency PWM modulated during the off period; (11) Grid voltage U a >U c >0>U b When, power switch tubes Q 2 , Q 4 , Q 5 , Q 6 , Q 7 , Q 9 , Q 11 , Q 13 are always off, Q 1 , Q 8 , Q 10 are always on, Q 14 is high-frequency PWM modulated, Q 3 turns on during the off period of Q 14 , Q 3 is high-frequency PWM modulated during the on period of Q 14 ; Q 12 turns on during the on period of Q 14 , Q 12 is high-frequency PWM modulated during the off period of Q 14 ; (12) Grid voltage U a >0>U c >U b When, power switch tubes Q 1 , Q 2 , Q 3 , Q 4 , Q 7 , Q 11 , Q 12 , Q 14 are always off, Q 5 , Q 8 , Q 10 are always on, Q 13 is high-frequency PWM modulated, Q 6 Turns on during the off period of Q 13 , Q 6 Turns on during the on period of Q 13 and is high-frequency PWM modulated during the on period of Q; Q 9 Turns on during the on period of Q 13 , Q 9 Turns on during the off period of Q 13 and is high-frequency PWM modulated during the off period; The three-phase buck-boost inverter circuit includes a DC power supply circuit, a chopper circuit, and a three-phase voltage source circuit. The input of the chopper circuit is connected to the DC power supply circuit, and the output of the chopper circuit is connected to the three-phase voltage source circuit. The DC power supply circuit is used for DC power supply of the inverter circuit. The chopper circuit is used to realize inversion in buck / boost / buck-boost mode. The three-phase voltage source circuit is used to absorb energy during inversion; The chopper circuit includes power switching transistors Q 1 ~Q 14 , diodes D 1 ~D 14 and an inductor L 1 ; The emitters of the power switching transistors Q 1 ~Q 14 are respectively connected to the anodes of the diodes D 1 ~D 14 , the collectors of the power switching transistors Q 4 , Q 7 are connected to the cathodes of the diodes D 1 , D 10 , the collectors of the power switching transistors Q 5 , Q 8 are connected to the cathodes of the diodes D 2 , D 11 , the collectors of the power switching transistors Q 6 , Q 9 are connected to the cathodes of the diodes D 3 , D 12 , the collectors of the power switching transistors Q 1 , Q 2 , Q 3 , Q 13 are connected, the cathodes of the diodes D 4 , D 5 , D 6 , D 14 are connected, the cathodes of the diodes D 7 , D 8 , D 9 , D 13 are connected and then connected to one end of the inductor L 1 , the collectors of the power switching transistors Q 10 , Q 11 , Q 12 , Q 14 are connected and then connected to the other end of the inductor L 1 ; The DC power supply circuit includes a DC voltage source E. The three-phase voltage source circuit includes three-phase voltage sources a, b, and c with initial phases differing by 120° in sequence, and one ends of the three-phase voltage sources a, b, and c are connected together; The positive electrode of the DC voltage source E of the DC power supply circuit is connected to the collector of the power switch transistors Q 1 , Q 2 , Q 3 , Q 13 of the chopper circuit, and the negative electrode of the DC voltage source E of the DC power supply circuit is connected to the cathode of the diodes D 4 , D 5 , D 6 , D 14 of the chopper circuit; The other end of the a-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 4 and Q 7 and the cathodes of the diodes D 1 and D 10 of the chopper circuit. The other end of the b-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 5 and Q 8 and the cathodes of the diodes D 2 and D 11 of the chopper circuit. The other end of the c-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 6 and Q 9 and the cathodes of the diodes D 3 and D 12 of the chopper circuit.

2. A boost modulation method for a three-phase buck-boost inverter circuit, Characterized in that: It includes the following steps: (1) Grid voltage U a >0>U b >U c When, power switch tubes Q 1 、Q 2 、Q 3 、Q 4 、Q 7 、Q 8 、Q 9 、Q 11 、Q 12 are always off, Q 6 、Q 10 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 5 turns on during the conduction period of Q 14 and is modulated by high-frequency PWM during the turn-off period of Q 5 During the turn-off period of Q 14 ; (2) Grid voltage U a >U b >0>U c When, power switch tubes Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 10 、Q 11 、Q 12 are always off, Q 1 、Q 9 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 2 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the turn-off period of Q 2 During the turn-off period of Q 13 ; (3) Grid voltage U b >U a >0>U c When, power switch tubes Q 3 、Q 4 、Q 5 、Q 6 、Q 7 、Q 8 、Q 10 、Q 11 、Q 12 are always off, Q 2 、Q 9 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 1 turns on during the conduction period of Q 13 and is high-frequency PWM modulated during the turn-off period of Q 1 During the turn-off period of Q 13 ; (4) Grid voltage U b >0>U a >U c When, power switch tubes Q 1 、Q 2 、Q 3 、Q 5 、Q 7 、Q 8 、Q 9 、Q 10 、Q 12 are always off, Q 6 、Q 11 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 4 is turned on during the conduction period of Q 14 and is high-frequency PWM modulated during the off period of Q 4 During the off period of Q 14 ; (5) Grid voltage U b > 0 > U c > U a When, power switch tubes Q 1 、Q 2 、Q 3 、Q 5 、Q 7 、Q 8 、Q 9 、Q 10 、Q 12 are always off, Q 4 、Q 11 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 6 is turned on during the conduction period of Q 14 and is high-frequency PWM modulated during the off period of Q 6 During the off period of Q 14 ; (6) Grid voltage U b >U c >0>U a When, power switch tubes Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 2 、Q 7 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 3 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the off period of Q 3 During the off period of Q 13 ; (7) Grid voltage U c >U b >0>U a When, power switch tubes Q 1 、Q 4 、Q 5 、Q 6 、Q 8 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 3 、Q 7 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 2 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the off period of Q 2 During the off period of Q 13 ; (8) Grid voltage U c >0>U b >U a When, power switch tubes Q 1 、Q 2 、Q 3 、Q 6 、Q 7 、Q 8 、Q 9 、Q 10 、Q 11 are always off, Q 4 、Q 12 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 5 During the conduction period of Q 14 it turns on, Q 5 During the off period of Q 14 it is high-frequency PWM modulated; (9) Grid voltage U c >0>U a >U b When, power switch transistors Q 1 、Q 2 、Q 3 、Q 6 、Q 7 、Q 8 、Q 9 、Q 10 、Q 11 are always off, Q 5 、Q 12 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 4 is turned on during the conduction period of Q 14 and is high-frequency PWM modulated during the turn-off period of Q 4 During the turn-off period of Q 14 ; (10) Grid voltage U c >U a >0>U b When, power switch tubes Q 2 、Q 4 、Q 5 、Q 6 、Q 7 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 3 、Q 8 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 1 turns on during the conduction period of Q 13 and is high-frequency PWM modulated during the turn-off period of Q 1 During the turn-off period of Q 13 ; (11) Grid voltage U a >U c >0>U b When, power switch tubes Q 2 、Q 4 、Q 5 、Q 6 、Q 7 、Q 9 、Q 10 、Q 11 、Q 12 are always off, Q 1 、Q 8 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 3 is turned on during the conduction period of Q 13 and is high-frequency PWM modulated during the off period of Q 3 During the off period of Q 13 ; (12) Grid voltage U a >0>U c >U b When, power switch tubes Q 1 、Q 2 、Q 3 、Q 4 、Q 7 、Q 8 、Q 9 、Q 11 、Q 12 are always off, Q 5 、Q 10 、Q 13 are always on, Q 14 is high-frequency PWM modulated, Q 6 is turned on during the conduction period of Q 14 and is high-frequency PWM modulated during the turn-off period of Q 6 During the turn-off period of Q 14 is high-frequency PWM modulated; The three-phase buck-boost inverter circuit includes a DC power supply circuit, a chopper circuit, and a three-phase voltage source circuit. The input of the chopper circuit is connected to the DC power supply circuit, and the output of the chopper circuit is connected to the three-phase voltage source circuit. The DC power supply circuit is used for DC power supply of the inverter circuit. The chopper circuit is used to realize inversion in buck / boost / buck-boost mode. The three-phase voltage source circuit is used to absorb energy during inversion; The chopper circuit includes a power switch tube Q 1 ~Q 14 、Diode D 1 ~D 14 And the inductor L 1 ; The power switch tube Q 1 ~Q 14 The emitter of diode D 1 ~D 14 The anode of the power switch tube Q 4 , Q 7 Collector and diode D 1 , D 10 The cathode of the power switch tube Q 5 , Q 8 The collector of the diode D 2 , D 11 The cathode of the power switch tube Q 6 , Q 9 The collector of the diode D 3 , D 12 The cathode of the power switch tube Q 1 , Q 2 , Q 3 , Q 13 The collector of diode D 4 , D 5 , D 6 , D 14 The cathode of diode D 7 , D 8 , D 9 , D 13 The cathode of the 1 One end of the power switch tube Q 10 , Q 11 , Q 12 , Q 14 The collector of is connected to the inductor L 1 The other end of The DC power supply circuit includes a DC voltage source E. The three-phase voltage source circuit includes three-phase voltage sources a, b, and c with initial phases differing by 120° in sequence, and one ends of the three-phase voltage sources a, b, and c are connected together; The positive pole of the DC voltage source E of the DC power supply circuit is connected to the power switch transistors Q 1 , Q 2 , Q 3 , Q 13 of the chopper circuit. The negative pole of the DC voltage source E of the DC power supply circuit is connected to the diodes D 4 , D 5 , D 6 , D 14 of the chopper circuit at their cathodes; The other end of the a-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 4 , Q 7 and the cathodes of the diodes D 1 , D 10 of the chopper circuit. The other end of the b-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 5 , Q 8 and the cathodes of the diodes D 2 , D 11 of the chopper circuit. The other end of the c-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 6 , Q 9 and the cathodes of the diodes D 3 , D 12 of the chopper circuit.

3. A buck-boost modulation method for a three-phase buck-boost inverter circuit, Characterized in that: It includes the following steps: (1) Grid voltage U a > 0 > U b > U c When, power switch tube Q 1 -Q 6 、Q 7 、Q 11 、Q 12 are always off, Q 9 、Q 10 、Q 14 are always on, Q 13 is modulated by high-frequency PWM, Q 8 During the conduction period of Q 13 turns on, when Q 13 turns off, Q 8 is modulated by high-frequency PWM; (2) Grid voltage U a >U b >0>U c When, power switch tube Q 1 -Q 6 、Q 7 、Q 8 、Q 12 are always off, Q 9 、Q 10 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 11 is turned on during the conduction period of Q 14 When Q 14 is turned off, Q 11 is modulated by high-frequency PWM; (3) Grid voltage U b >U a >0>U c When, the power switch tubes Q 1 -Q 6 、Q 7 、Q 8 、Q 12 are always off, Q 9 、Q 11 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 10 is turned on during the conduction period of Q 14 , and when Q 14 is turned off, Q 10 is modulated by high-frequency PWM; (4) Grid voltage U b >0>U a >U c When, the power switch tubes Q 1 -Q 6 、Q 8 、Q 10 、Q 12 are always off, Q 9 、Q 11 、Q 14 are always on, Q 13 is modulated by high-frequency PWM, Q 7 is turned on during the conduction period of Q 13 , and when Q 13 is turned off, Q 7 is modulated by high-frequency PWM; (5) Grid voltage U b > 0 > U c > U a When, the power switch tubes Q 1 -Q 6 、Q 8 、Q 10 、Q 12 are always off, Q 7 、Q 11 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 9 is turned on during the conduction period of Q 13 , and when Q 13 is turned off, Q 9 is high-frequency PWM modulated; (6) Grid voltage U b >U c >0>U a When, the power switch tubes Q 1 -Q 6 、Q 8 、Q 9 、Q 10 are always off, Q 7 、Q 11 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 12 is turned on during the conduction period of Q 14 , when Q 14 is turned off, Q 12 is modulated by high-frequency PWM; (7) Grid voltage U c >U b >0>U a When, the power switch tubes Q 1 -Q 6 、Q 8 、Q 9 、Q 10 are always off, Q 7 、Q 12 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 11 is turned on during the conduction period of Q 14 When Q 14 is turned off, Q 11 is modulated by high-frequency PWM; (8) Grid voltage U c > 0 > U b > U a When, power switch tube Q 1 -Q 6 、Q 9 、Q 10 、Q 11 is always off, Q 7 、Q 12 、Q 14 is always on, Q 13 High-frequency PWM modulation, Q 8 During the conduction period of Q 13 turns on, when Q 13 turns off, Q 8 High-frequency PWM modulation; (9) Grid voltage U c > 0 > U a > U b When, the power switch tubes Q 1 -Q 6 、Q 9 、Q 10 、Q 11 are always off, Q 8 、Q 12 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 7 During the conduction period of Q 13 turns on, when Q 13 turns off, Q 7 is high-frequency PWM modulated; (10) Grid voltage U c >U a >0>U b When, power switch tube Q 1 -Q 6 、Q 7 、Q 9 、Q 11 are always off, Q 8 、Q 12 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 10 is turned on during the conduction period of Q 14 When Q 14 is turned off, Q 10 is modulated by high-frequency PWM; (11) Grid voltage U a >U c >0>U b When, power switch tube Q 1 -Q 6 、Q 7 、Q 9 、Q 11 are always off, Q 8 、Q 10 、Q 13 are always on, Q 14 is modulated by high-frequency PWM, Q 12 is turned on during the conduction period of Q 14 , when Q 14 is turned off, Q 12 is modulated by high-frequency PWM; (12) Grid voltage U a >0> U c > U b When, power switch tube Q 1 -Q 6 、Q 7 、Q 11 、Q 12 are always off, Q 8 、Q 10 、Q 14 are always on, Q 13 is high-frequency PWM modulated, Q 9 is turned on during the conduction period of Q 13 When Q 13 is turned off, Q 9 is high-frequency PWM modulated; The three-phase buck-boost inverter circuit includes a DC power supply circuit, a chopper circuit, and a three-phase voltage source circuit. The input of the chopper circuit is connected to the DC power supply circuit, and the output of the chopper circuit is connected to the three-phase voltage source circuit. The DC power supply circuit is used for DC power supply of the inverter circuit. The chopper circuit is used to realize inversion in buck / boost / buck-boost mode. The three-phase voltage source circuit is used to absorb energy during inversion; The chopper circuit includes power switching transistors Q 1 ~Q 14 , diodes D 1 ~D 14 and an inductor L 1 ; The emitters of the power switching transistors Q 1 ~Q 14 are respectively connected to the anodes of the diodes D 1 ~D 14 . The collectors of the power switching transistors Q 4 , Q 7 are connected to the cathodes of the diodes D 1 , D 10 . The collectors of the power switching transistors Q 5 , Q 8 are connected to the cathodes of the diodes D 2 , D 11 . The collectors of the power switching transistors Q 6 , Q 9 are connected to the cathodes of the diodes D 3 , D 12 . The collectors of the power switching transistors Q 1 , Q 2 , Q 3 , Q 13 are connected together. The cathodes of the diodes D 4 , D 5 , D 6 , D 14 are connected together and then connected to one end of the inductor L 7 , D 8 , D 9 , D 13 . The collectors of the power switching transistors Q 1 , Q 10 , Q 11 , Q 12 , Q 14 are connected together and then connected to the other end of the inductor L 1 ; The DC power supply circuit includes a DC voltage source E. The three-phase voltage source circuit includes three-phase voltage sources a, b, and c with initial phases differing by 120° in sequence, and one ends of the three-phase voltage sources a, b, and c are connected together; The positive pole of the DC voltage source E of the DC power supply circuit is connected to the power switch transistors Q 1 , Q 2 , Q 3 , Q 13 of the chopper circuit. The negative pole of the DC voltage source E of the DC power supply circuit is connected to the diodes D 4 , D 5 , D 6 , D 14 of the chopper circuit at their cathodes; The other end of the a-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 4 , Q 7 and the cathodes of the diodes D 1 , D 10 of the chopper circuit. The other end of the b-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 5 , Q 8 and the cathodes of the diodes D 2 , D 11 of the chopper circuit. The other end of the c-phase voltage source of the three-phase voltage source circuit is connected to the collector of the power switching transistors Q 6 , Q 9 and the cathodes of the diodes D 3 , D 12 of the chopper circuit.

4. A three-phase buck-boost inverter circuit based on the buck modulation method of the three-phase buck-boost inverter circuit according to claim 1, Characterized in that: The power switching transistor Q 1 ~Q 14 is an IGBT or a MOSFET.

5. According to the three-phase buck-boost inverter circuit described in claim 4, Characterized in that: It includes a filter, and the filter is arranged between the three-phase voltage source circuit and the chopper circuit.

6. A three-phase buck-boost inverter circuit based on the boost modulation method of the three-phase buck-boost inverter circuit according to claim 2, Characterized in that: The power switching transistor Q 1 ~Q 14 is an IGBT or a MOSFET.

7. According to the three-phase buck-boost inverter circuit described in claim 6, Characterized in that: It includes a filter, and the filter is arranged between the three-phase voltage source circuit and the chopper circuit.

8. A three-phase buck-boost inverter circuit based on the buck-boost modulation method of the three-phase buck-boost inverter circuit according to claim 3, Characterized in that: The power switch tubes Q 1 ~Q 14 are IGBTs or MOSFETs.

9. The three-phase buck-boost inverter circuit according to claim 8, characterized in that: it includes a filter, and the filter is arranged between the three-phase voltage source circuit and the chopper circuit.

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