Quasi-single-stage micro inverter and electronic equipment

Abstract

The invention discloses a quasi-single-stage micro inverter and electronic equipment, the quasi-single-stage micro inverter comprises a boost converter circuit and a buck converter circuit, the boost converter circuit is coupled with the buck converter circuit, one of the boost converter circuit and the buck converter circuit is coupled with a power grid end, and the other of the boost converter circuit and the buck converter circuit is coupled with a power grid end. The other one of the boost converter circuit and the buck converter circuit is coupled with the direct current end; wherein when the absolute value of the power grid voltage is smaller than the mode switching voltage, the buck converter circuit is controlled to carry out buck work, and the boost converter circuit is controlled to work in the optimal efficiency working condition; the absolute value of the power grid voltage is greater than the mode switching voltage; if yes, controlling the boost converter circuit to perform boost work and controlling the buck converter circuit to work in the optimal efficiency working condition. By means of the mode, the quasi-single-stage micro inverter is higher in efficiency and easy to control, and circuit parameters are convenient to optimize.

Description

Technical Field

[0001] This application relates to the field of microinverter technology, specifically to a quasi-single-stage microinverter and electronic equipment. Background Technology

[0002] Currently, common micro-inverter solutions include single-stage and two-stage solutions. The single-stage solution has the advantages of fewer components and higher efficiency. However, its DC port and grid port are directly coupled, making control very complex and circuit parameter optimization difficult. In contrast, the two-stage solution has the advantages of simple control and convenient circuit parameter optimization. Its front-stage DC-to-DC inverter can be optimized according to the DC port, and its rear-stage DC-to-AC inverter can be optimized according to the grid port, decoupling the front and rear stages. However, it uses more components and has lower efficiency. Summary of the Invention

[0003] To address the aforementioned problems, this application proposes a quasi-single-stage micro inverter and electronic equipment, which aims to solve the problems described above.

[0004] To solve the above-mentioned technical problems, one technical solution adopted in this application is: providing a quasi-single-stage micro-inverter, which includes a boost converter circuit and a buck converter circuit, the boost converter circuit and the buck converter circuit being coupled together, one of the boost converter circuit and the buck converter circuit being coupled to the grid terminal, and the other of the boost converter circuit and the buck converter circuit being coupled to the DC terminal; wherein, in response to the absolute value of the grid voltage being less than the mode switching voltage, the buck converter circuit is controlled to perform buck operation and the boost converter circuit is controlled to operate in the optimal efficiency condition; in response to the absolute value of the grid voltage being greater than the mode switching voltage, the boost converter circuit is controlled to perform boost operation and the buck converter circuit is controlled to operate in the optimal efficiency condition.

[0005] At least one of the boost converter circuit and the buck converter circuit is equipped with an isolation transformer.

[0006] The mode switching voltage is set to the product of the fixed gain of the boost converter circuit and the buck converter circuit, the rated voltage of the DC terminal components, and the turns ratio of the isolation transformer.

[0007] The boost converter circuit includes a DC-DC boost converter circuit, and the buck converter circuit includes a first series resonant converter circuit. The input terminal of the DC-DC boost converter circuit is coupled to the DC terminal, the output terminal of the DC-DC boost converter circuit is coupled to the input terminal of the first series resonant converter circuit, and the output terminal of the first series resonant converter circuit is coupled to the power grid terminal.

[0008] The DC-DC boost converter circuit includes a first capacitor, a second capacitor, a first inductor, a first switch, and a second switch. The first terminal of the first capacitor is connected to the first terminal of the first inductor. The second terminal of the first inductor is connected to the first terminal of the first switch and the first terminal of the second switch. The second terminal of the second switch is connected to the first terminal of the second capacitor. The second terminals of the first capacitor, the first switch, and the second capacitor are grounded. The two terminals of the first capacitor serve as the input terminals of the DC-DC boost converter circuit and are coupled to the DC terminal. The two terminals of the second capacitor serve as the output terminals of the DC-DC boost converter circuit and are coupled to the input terminals of the first series resonant converter circuit. When the DC-DC boost converter circuit operates under optimal efficiency conditions, the first switch is open and the second switch is on. When the DC-DC boost converter circuit is performing boost operation, the first switch is switched on and off at high frequency, and the second switch is complementary to the first switch. When the first series resonant converter circuit operates under optimal efficiency conditions, it operates at the resonant frequency point and the phase shift angle is 0.

[0009] The boost converter circuit includes a second series resonant converter circuit, and the buck converter circuit includes a full-bridge inverter circuit. The input terminal of the second series resonant converter circuit is coupled to the DC terminal, the output terminal of the second series resonant converter circuit is coupled to the input terminal of the full-bridge inverter circuit, and the output terminal of the full-bridge inverter circuit is coupled to the grid terminal.

[0010] The full-bridge inverter circuit includes a third switch, a fourth switch, a fifth switch, and a sixth switch. The output terminal of the second series resonant converter circuit is connected to the first terminal of the third switch and the first terminal of the fifth switch. The second terminal of the third switch is connected to the first terminal of the fourth switch, and the second terminal of the fifth switch is connected to the first terminal of the sixth switch. The second terminals of the fourth switch and the sixth switch are coupled and grounded. The connection point between the second terminal of the third switch and the first terminal of the fourth switch, and the connection point between the second terminal of the fifth switch and the first terminal of the sixth switch, serve as the output terminal of the full-bridge inverter circuit. When the second series resonant converter circuit operates under optimal efficiency conditions, it operates at the resonant frequency point with a phase shift angle of 0. When the full-bridge inverter circuit operates under optimal efficiency conditions, the third and sixth switches are always on, or the fourth and fifth switches are always on.

[0011] The boost converter circuit includes a second series resonant converter circuit, and the buck converter circuit includes a buck chopper circuit and a power frequency folding bridge circuit. The input terminal of the second series resonant converter circuit is coupled to the DC terminal, the output terminal of the second series resonant converter circuit is coupled to the input terminal of the buck chopper circuit, the output terminal of the buck chopper circuit is coupled to the input terminal of the power frequency folding bridge circuit, and the output terminal of the power frequency folding bridge circuit is coupled to the grid terminal.

[0012] The power frequency folding bridge circuit includes a seventh switch, an eighth switch, a ninth switch, and a tenth switch. The output terminal of the buck chopper circuit is connected to the first terminal of the seventh switch and the first terminal of the ninth switch. The second terminal of the seventh switch is connected to the first terminal of the eighth switch, and the second terminal of the ninth switch is connected to the first terminal of the tenth switch. The second terminals of the eighth switch and the tenth switch are coupled and grounded. The connection point between the second terminal of the seventh switch and the first terminal of the eighth switch, and the connection point between the second terminal of the ninth switch and the first terminal of the tenth switch, serve as the output terminal of the power frequency folding bridge circuit. When the second series resonant converter circuit operates at its optimal efficiency, it operates at the resonant frequency and the phase shift angle is 0. When the buck chopper circuit and the power frequency folding bridge circuit operate at their optimal efficiency, the seventh and tenth switches are always on, or the eighth and ninth switches are always on.

[0013] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide an electronic device, which includes any of the above-mentioned quasi-single-stage micro inverters and controllers.

[0014] The beneficial effects of this application are as follows: Unlike the prior art, the quasi-single-stage micro inverter of this application includes a boost converter circuit and a buck converter circuit, which are coupled together. One of the boost converter circuit and the buck converter circuit is coupled to the grid terminal, and the other of the boost converter circuit and the buck converter circuit is coupled to the DC terminal. Specifically, in response to the absolute value of the grid voltage being less than the mode switching voltage, the buck converter circuit is controlled to perform buck operation while the boost converter circuit operates at its optimal efficiency. In response to the absolute value of the grid voltage being greater than the mode switching voltage, the boost converter circuit is controlled to perform boost operation while the buck converter circuit operates at its optimal efficiency. Through the above methods, the quasi-single-stage micro inverter of this application can enable the boost converter and buck converter circuits to operate at their optimal efficiency under different grid voltages, thereby improving the efficiency of the quasi-single-stage micro inverter over the entire power frequency cycle. At the same time, since this application can be combined using conventional circuit topologies, the parameter optimization method and control method are relatively simple, and the engineering feasibility is high. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application.

[0016] Figure 1 This is a schematic diagram of the structure of the first embodiment of the quasi-single-stage micro inverter provided in this application;

[0017] Figure 2 This is a schematic diagram of the structure of the second embodiment of the quasi-single-stage micro inverter provided in this application;

[0018] Figure 3 This is a schematic diagram of the structure of the third embodiment of the quasi-single-stage micro inverter provided in this application;

[0019] Figure 4 This is a schematic diagram of the phase-shift control waveform of the first series resonant converter circuit provided in this application;

[0020] Figure 5 yes Figure 3 Example diagram of drive signals for a quasi-single-stage micro inverter;

[0021] Figure 6 This is a schematic diagram of the structure of the fourth embodiment of the quasi-single-stage micro inverter provided in this application;

[0022] Figure 7 This is a schematic diagram of the structure of the fifth embodiment of the quasi-single-stage micro inverter provided in this application;

[0023] Figure 8 This is a schematic diagram of the phase-shift control waveform of the second series resonant converter circuit provided in this application;

[0024] Figure 9 yes Figure 7 A schematic diagram of the drive signal for a quasi-single-stage micro inverter;

[0025] Figure 10 This is a schematic diagram of the structure of the sixth embodiment of the quasi-single-stage micro-inverter provided in this application;

[0026] Figure 11 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] Currently, common micro-inverter solutions include single-stage and two-stage solutions. The single-stage solution has the advantages of fewer components and higher efficiency. However, its DC port and grid port are directly coupled, making control very complex and circuit parameter optimization difficult. In contrast, the two-stage solution has the advantages of simple control and convenient circuit parameter optimization. Its front-stage DC-to-DC inverter can be optimized according to the DC port, and its rear-stage DC-to-AC inverter can be optimized according to the grid port, decoupling the front and rear stages. However, it uses more components and has lower efficiency.

[0029] To address the aforementioned issues, this application first proposes a quasi-single-stage micro inverter. Please refer to [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the quasi-single-stage micro inverter provided in this application. As shown in Figure 1, the quasi-single-stage micro inverter 100 of this embodiment includes a boost converter circuit 10 and a buck converter circuit 20. The boost converter circuit 10 and the buck converter circuit 20 are coupled together. The buck converter circuit 20 is coupled to the grid terminal, and the boost converter circuit 10 is coupled to the DC terminal.

[0030] Please see Figure 2 , Figure 2 This is a schematic diagram of the second embodiment of the quasi-single-stage microinverter provided in this application. In other embodiments, the positions of the boost converter 10 and the buck converter 20 can be interchanged. That is, as follows: Figure 2 As shown, the buck converter circuit 20 is coupled to the DC terminal, and the boost converter circuit 10 is coupled to the grid terminal.

[0031] based on Figure 1 and Figure 2 In one embodiment, in response to the absolute value of the grid voltage being less than the mode switching voltage, the buck converter circuit 20 is controlled to perform buck operation and the boost converter circuit 10 is controlled to operate in the optimal efficiency condition; in response to the absolute value of the grid voltage being greater than the mode switching voltage, the boost converter circuit 10 is controlled to perform boost operation and the buck converter circuit 20 is controlled to operate in the optimal efficiency condition.

[0032] In this embodiment, the optimal efficiency condition refers to the boost converter circuit 10 and the buck converter circuit 20 operating at their respective optimal operating conditions, under which the efficiency of the boost converter circuit 10 and the buck converter circuit 20 is the highest. For example, the optimal efficiency conditions for the Buck converter current and the Boost converter circuit are when their main switches are shoot-on and normally off, respectively.

[0033] Unlike existing technologies, the quasi-single-stage micro inverter 100 of this application includes a boost converter circuit 10 and a buck converter circuit 20. The boost converter circuit 10 and the buck converter circuit 20 are coupled together. One of the boost converter circuit 10 and the buck converter circuit 20 is coupled to the grid terminal, and the other of the boost converter circuit 10 and the buck converter circuit 20 is coupled to the DC terminal. When the absolute value of the grid voltage is less than the mode switching voltage, the buck converter circuit 20 is controlled to perform buck operation while the boost converter circuit 10 is controlled to operate at its optimal efficiency. When the absolute value of the grid voltage is greater than the mode switching voltage, the boost converter circuit 10 is controlled to perform boost operation while the buck converter circuit 20 is controlled to operate at its optimal efficiency. In the above manner, the quasi-single-stage micro inverter 100 of this application can enable the boost converter 10 and the buck converter circuit 20 to operate at their optimal efficiency under different grid voltages, thereby improving the efficiency of the quasi-single-stage micro inverter 100 throughout the entire power frequency cycle. At the same time, since this application can be combined using conventional circuit topologies, the parameter optimization method and control method are relatively simple, and the engineering feasibility is high.

[0034] Optionally, based on Figure 1 and Figure 2 In this embodiment, at least one of the boost converter circuit 10 and the buck converter circuit 20 is provided with an isolation transformer, which enables micro-inverting electrical isolation properties.

[0035] Optionally, based on Figure 1 and Figure 2 In this embodiment, the mode switching voltage is set to the product of the fixed gain of the boost converter circuit 10 and the buck converter circuit 20, the rated voltage of the DC terminal component, and the turns ratio of the isolation transformer.

[0036] For example, the mode switching voltage V M The calculation formula is shown in formula (1):

[0037] V M =kNV PVrated

[0038] Among them, V M V represents the mode switching voltage, k represents the fixed gain of the boost converter circuit 10 and the buck converter circuit 20, and V represents the voltage at which the mode is switched. PVrated The rated voltage of the DC terminal component is represented by N, and the turns ratio of the isolation transformer is represented by N.

[0039] Optionally, please refer to Figure 3 , Figure 3 This is a schematic diagram of the third embodiment of the quasi-single-stage microinverter provided in this application. Figure 3As shown, the boost converter circuit of this embodiment includes a DC boost converter circuit 11, and the buck converter circuit includes a first series resonant converter circuit 21. The input terminal of the DC boost converter circuit 11 is coupled to the DC terminal, the output terminal of the DC boost converter circuit 11 is coupled to the input terminal of the first series resonant converter circuit 21, and the output terminal of the first series resonant converter circuit 21 is coupled to the grid terminal.

[0040] Optionally, based on Figure 3 Examples, such as Figure 3 As shown, the DC-DC boost converter circuit 11 of this embodiment includes a first capacitor Cin, a second capacitor Cbus, a first inductor Lin, a first switch S1, and a second switch S2. The first terminal of the first capacitor Cin is connected to the first terminal of the first inductor Lin. The second terminal of the first inductor Lin is connected to the first terminal of the first switch S1 and the first terminal of the second switch S2, respectively. The second terminal of the second switch S2 is connected to the first terminal of the second capacitor Cbus. The second terminal of the first capacitor Cin, the second terminal of the first switch S1, and the second terminal of the second capacitor Cbus are grounded. The two terminals of the first capacitor Cin serve as the input terminal of the DC-DC boost converter circuit 11 and are coupled to the DC terminal. The two terminals of the second capacitor Cbus serve as the output terminal of the DC-DC boost converter circuit 11 and are coupled to the input terminal of the first series resonant converter circuit 21.

[0041] When the absolute value of the grid voltage is less than the mode switching voltage, the DC-DC boost converter circuit 11 is controlled to operate in the optimal efficiency condition. At this time, the first switch S1 of the DC-DC boost converter circuit is opened and the second switch S2 is turned on.

[0042] When the absolute value of the grid voltage is greater than the mode switching voltage, the DC-DC boost converter circuit is controlled to perform boost operation. At this time, controlling the DC-DC boost converter circuit to perform boost operation means controlling the first switch S1 of the DC-DC boost converter circuit to perform high-frequency switching. The second switch S2 is complementary to the first switch S1. The opening and closing of the second switch S2 and the first switch S1 are always opposite and will not be opened or closed at the same time.

[0043] like Figure 3 As shown, the first series resonant converter circuit 21 of this embodiment includes a switching circuit 211, a resonant circuit 212, an isolation transformer 213, and a first rectifier circuit 214. The switching circuit 211 includes an eleventh switch S11, a twelfth switch S12, a thirteenth switch S13, and a fourteenth switch S14. The resonant circuit 212 includes a resonant inductor Lr, a first resonant capacitor Cr1, and a second resonant capacitor Cr2. The first rectifier circuit 214 includes a fifteenth switch S15, a sixteenth switch S16, a seventeenth switch S17, an eighteenth switch S18, and an output capacitor Co.

[0044] The positive output terminal of the DC-DC boost converter circuit 11 is connected to the first terminal of the eleventh switch S11 and the first terminal of the thirteenth switch S13, respectively. The second terminal of the eleventh switch S11 is connected to the first terminal of the twelfth switch S12, and the second terminal of the thirteenth switch S13 is connected to the second terminal of the fourteenth switch S14. The second terminals of the twelfth switch S12 and the fourteenth switch S14 are grounded. The connection point between the second terminal of the eleventh switch S11 and the first terminal of the twelfth switch S12 is connected to the first terminal of the resonant inductor Lr. The second terminal of the resonant inductor Lr is connected to the first terminal of the primary winding of the isolation transformer 213. The connection point between the second terminal of the thirteenth switch S13 and the fourteenth switch S14 is connected to the second terminal of the primary winding of the isolation transformer 213. The first terminal of the fifteenth switch S15 is connected to the first terminal of the first resonant capacitor Cr1, and the second terminal of the fifteenth switch S15 is connected to the tenth switch S14. The first terminal of switch S16 is connected; the second terminal of switch S16 is connected to the first terminal of switch S17; the second terminal of switch S17 is connected to the first terminal of switch S18; the second terminal of first resonant capacitor Cr1 is connected to the first terminal of second resonant capacitor Cr2; the first terminal of input capacitor Co is connected to the first terminal of switch S15; the second terminal of switch S18, the second terminal of second resonant capacitor Cr2, and the second terminal of output capacitor Co are coupled and grounded; the first terminal of the secondary side of isolation transformer 213 is connected to the connection point between the second terminal of switch S16 and the first terminal of switch S17; the second terminal of the secondary side of isolation transformer 213 is connected to the connection point between the second terminal of first resonant capacitor Cr1 and the first terminal of second resonant capacitor Cr2; the two ends of output capacitor Co serve as the output terminals of the first series resonant converter circuit 21.

[0045] In addition, such as Figure 3 As shown, the output terminal of the first series resonant converter circuit 21 in this embodiment is also connected to the grid terminal through an LC filter circuit 30, which is used to filter the grid-connected voltage.

[0046] When the absolute value of the grid voltage is greater than the mode switching voltage, the first series resonant converter circuit 21 is controlled to operate in the optimal efficiency condition. At this time, controlling the first series resonant converter circuit 21 to operate in the optimal efficiency condition means controlling the first series resonant converter circuit 21 to operate at the resonant frequency point, and adjusting the phase shift angle... Set to 0.

[0047] When the absolute value of the grid voltage is less than the mode switching voltage, the first series resonant converter circuit 21 is controlled to perform a step-down operation. At this time, the shift angle can be set based on the step-down requirement. Set the shift angle of the first series resonant converter circuit 21 At this time, it is necessary to move the angle The voltage is set to be greater than zero; and in the first rectifier circuit 214, when the absolute value of the grid voltage is less than the mode switching voltage and the grid voltage is positive, the first series resonant converter circuit 21 is controlled to perform voltage reduction operation, that is, the sixteenth switch S16 and the eighteenth switch S18 are kept on, and the fifteenth switch S15 and the seventeenth switch S17 perform synchronous rectification operation; when the absolute value of the grid voltage is less than the mode switching voltage and the grid voltage is negative, the first series resonant converter circuit 21 is controlled to perform voltage reduction operation, that is, the sixteenth switch S16 and the eighteenth switch S18 are controlled to perform synchronous rectification operation, and the fifteenth switch S15 and the seventeenth switch S17 are kept on.

[0048] Please see Figures 3 to 4 , Figure 4 This is a schematic diagram of the phase-shift control waveform of the first series resonant converter circuit provided in this application. In this embodiment, as... Figure 3 As shown, the secondary side of the first series resonant converter circuit 21 in this embodiment adopts a Cyclo rectifier structure, which can achieve positive or negative output voltage to adapt to the grid voltage. Figure 4 As shown, the first series resonant converter circuit 21 in this embodiment can achieve voltage reduction through primary-side phase shift control or frequency conversion control. Furthermore, Figure 4 The ratio of the time by which the leading edge of the fourteenth switch S14 lags behind the leading edge of the eleventh switch S11 during the switching cycle, multiplied by 2π, is called the phase shift angle mentioned earlier. When the first series resonant converter circuit 21 operates at the resonant frequency and the phase shift angle is... When set to 0, it operates at its optimal efficiency, at which point its efficiency is at its highest, and it can be regarded as a DC transformer.

[0049] Please see Figure 5 , Figure 5 yes Figure 3 Example diagram of drive signals for a quasi-single-stage micro inverter. Figure 3 The drive state of the quasi-single-stage micro inverter 100 corresponding to the embodiment is as follows: Figure 5 As shown, where V M This refers to the mode switching voltage mentioned earlier.

[0050] In other embodiments, please refer to Figure 6 , Figure 6 This is a schematic diagram of the fourth embodiment of the quasi-single-stage micro-inverter provided in this application. Figure 6 Show, and Figure 3 Unlike the previous embodiment, the first series resonant converter circuit 21 in this embodiment includes a switching circuit 211, a resonant circuit 212, an isolation transformer 213, and a second rectifier circuit 215. The circuit structure and connection relationship of the switching circuit 211, the resonant circuit 212, and the isolation transformer 213 are similar to those in the previous embodiment. Figure 3The same as the implementation example, and Figure 3 The difference in the embodiment is that the rectifier circuit of the second rectifier circuit 215 adopts a voltage doubler rectifier structure. In addition, in order to connect to the grid, the first series resonant converter circuit 21 is also equipped with a power frequency folding bridge circuit 40.

[0051] like Figure 6 As shown, the second rectifier circuit 215 includes a first diode D1, a second diode D2, and an output capacitor Co. The negative terminal of the first diode D1 is connected to the first terminal of the first resonant capacitor Cr1, the positive terminal of the first diode D1 is connected to the negative terminal of the second diode D2, the second terminal of the first resonant capacitor Cr1 is connected to the first terminal of the second resonant capacitor Cr2, the first terminal of the output capacitor Co is connected to the negative terminal of the first diode D1, and the positive terminal of the second diode D2, the second terminal of the second resonant capacitor Cr2, and the second terminal of the output capacitor Co are coupled and grounded. The first terminal of the secondary side of the isolation transformer 213 is connected to the connection point between the positive terminal of the first diode D1 and the negative terminal of the second diode D2. The second terminal of the secondary side of the isolation transformer 213 is connected to the connection point between the second terminal of the first resonant capacitor Cr1 and the first terminal of the second resonant capacitor Cr2. The first and second terminals of the output capacitor Co serve as the output terminals of the second rectifier circuit 215.

[0052] like Figure 6 As shown, the power frequency folding bridge circuit 40 includes a seventh switch S7, an eighth switch S8, a ninth switch S9, a tenth switch S10, and the LC filter circuit 30 described above. The output terminal of the second rectifier circuit 215 is connected to the first terminal of the seventh switch S7 and the first terminal of the ninth switch S9. The second terminal of the seventh switch S7 is connected to the first terminal of the eighth switch S8. The second terminal of the ninth switch S9 is connected to the first terminal of the tenth switch S10. The second terminals of the eighth switch S8 and the tenth switch S10 are coupled and grounded. The connection between the second terminal of the seventh switch S7 and the first terminal of the eighth switch S8, and the connection between the second terminal of the ninth switch S9 and the first terminal of the tenth switch S10, serve as the output terminals of the power frequency folding bridge circuit 40 and are connected to the power grid terminal through the LC filter circuit 30.

[0053] In this embodiment, compared to Figure 3 The quasi-single-stage micro inverter 100 shown in this embodiment replaces the secondary-side rectification of the first series resonant converter circuit 21 with diode rectification, and achieves grid connection through the power frequency folding bridge circuit 40. Its working principle is the same as... Figure 3 The implementation examples are similar.

[0054] When the absolute value of the grid voltage is greater than the mode switching voltage, the first series resonant converter circuit 21 is controlled to operate in the optimal efficiency condition. At this time, controlling the first series resonant converter circuit 21 to operate in the optimal efficiency condition means controlling the first series resonant converter circuit 21 to operate at the resonant frequency point, and adjusting the phase shift angle... Set to 0.

[0055] When the absolute value of the grid voltage is less than the mode switching voltage, the first series resonant converter circuit 21 is controlled to perform a step-down operation. At this time, the shift angle can be set based on the step-down requirement. Set the shift angle of the first series resonant converter circuit 21 At this time, it is necessary to move the angle The voltage is set to be greater than zero; and in the power frequency folding bridge circuit 40, when the absolute value of the grid voltage is less than the mode switching voltage and the grid voltage is positive, the first series resonant converter circuit 21 is controlled to perform voltage reduction operation, which means controlling the seventh switch S7 and the tenth switch S10 to be on all the time; when the absolute value of the grid voltage is less than the mode switching voltage and the grid voltage is negative, the first series resonant converter circuit 21 is controlled to perform voltage reduction operation, which means controlling the eighth switch S8 and the ninth switch S9 to be on all the time.

[0056] Optionally, please refer to Figure 7 , Figure 7 This is a structural schematic diagram of the fifth embodiment of the quasi-single-stage microinverter provided in this application. Figure 7 As shown, the boost converter circuit of this embodiment includes a second series resonant converter circuit 12, and the buck converter circuit includes a full-bridge inverter circuit 22. The input terminal of the second series resonant converter circuit 12 is coupled to the DC terminal, the output terminal of the second series resonant converter circuit 12 is coupled to the input terminal of the full-bridge inverter circuit 22, and the output terminal of the full-bridge inverter circuit 22 is coupled to the grid terminal.

[0057] based on Figure 7 Examples, such as Figure 7 As shown, the second series resonant converter circuit 12 includes a switching circuit 121, a resonant circuit 122, an isolation transformer 123, and a third rectifier circuit 124. The circuit structure and connection relationship of the switching circuit 121, the resonant circuit 122, and the isolation transformer 123 in the second series resonant converter circuit 12 are as follows: Figure 3 In the first series resonant converter circuit 21 in the embodiment, the circuit structure and connection relationship of the switch circuit 211, the resonant circuit 212 and the isolation transformer 213 are the same. The difference is that the third rectifier circuit 124 in this embodiment only includes the nineteenth switch S19, the twentieth switch S20 and the output capacitor.

[0058] like Figure 7As shown, the first terminal of the nineteenth switch S19 is connected to the first terminal of the first resonant capacitor Cr1, the second terminal of the nineteenth switch S19 is connected to the first terminal of the twentieth switch S20, the second terminal of the first resonant capacitor Cr1 is connected to the first terminal of the second resonant capacitor Cr2, the first terminal of the input capacitor Co is connected to the first terminal of the nineteenth switch S19, the second terminal of the twentieth switch S20, the second terminal of the second resonant capacitor Cr2, and the second terminal of the output capacitor Co are coupled and grounded; the first terminal of the secondary side of the isolation transformer 123 is connected to the connection point between the second terminal of the nineteenth switch S19 and the first terminal of the twentieth switch S20; the second terminal of the secondary side of the isolation transformer 123 is connected to the connection point between the second terminal of the first resonant capacitor Cr1 and the first terminal of the second resonant capacitor Cr2; the two ends of the output capacitor Co are coupled to the input terminal of the full-bridge inverter circuit 22 as the output terminal of the second series resonant converter circuit 12.

[0059] In this embodiment, when the absolute value of the grid voltage is greater than the mode switching voltage, the second series resonant converter circuit 12 is controlled to perform boost operation. At this time, the phase shift angle can be set based on the boost requirement. Set the phase shift angle of the second series resonant converter circuit 12 At this time, it is necessary to adjust the phase shift angle of the second series resonant converter circuit 12. Set to greater than 0.

[0060] When the absolute value of the grid voltage is less than the mode switching voltage, the second series resonant converter circuit 12 is controlled to operate in the optimal efficiency condition. Controlling the second series resonant converter circuit 12 to operate in the optimal efficiency condition means controlling the second series resonant converter circuit 12 to operate at the resonant frequency point, and adjusting the phase shift angle... When set to 0, the second series resonant converter circuit 12 can be regarded as a DC transformer.

[0061] Optionally, based on Figure 7 Examples, such as Figure 7 As shown, the full-bridge inverter circuit 22 includes a third switch S3, a fourth switch S4, a fifth switch S5, and a sixth switch S6. The output terminal of the second series resonant converter circuit 12 is connected to the first terminal of the third switch S3 and the first terminal of the fifth switch S5. The second terminal of the third switch S3 is connected to the first terminal of the fourth switch S4. The second terminal of the fifth switch S5 is connected to the first terminal of the sixth switch S6. The second terminals of the fourth switch S4 and the sixth switch S6 are coupled and grounded. The connection point between the second terminal of the third switch S3 and the first terminal of the fourth switch S4, and the connection point between the second terminal of the fifth switch S5 and the first terminal of the sixth switch S6, serve as the output terminal of the full-bridge inverter circuit 22.

[0062] In this embodiment, the full-bridge inverter circuit 22 is controlled to operate at its optimal efficiency when the absolute value of the grid voltage is greater than the mode switching voltage. Specifically, for the full-bridge inverter circuit 22, its optimal efficiency is achieved when the third switch S3 and the sixth switch S6 are continuously on, or when the fourth switch S4 and the fifth switch S5 are continuously on. That is, when the absolute value of the grid voltage is greater than the mode switching voltage and the voltage is positive, the third switch S3 and the sixth switch S6 of the full-bridge inverter circuit 22 are continuously on to ensure the full-bridge inverter circuit 22 operates at its optimal efficiency; when the absolute value of the grid voltage is greater than the mode switching voltage and the voltage is negative, the fourth switch S4 and the fifth switch S5 of the full-bridge inverter circuit 22 are continuously on to ensure the full-bridge inverter circuit 22 operates at its optimal efficiency.

[0063] When the absolute value of the grid voltage is less than the mode switching voltage, the full-bridge inverter circuit 22 is controlled to operate at high frequency to achieve voltage reduction. In this embodiment, when the full-bridge inverter circuit 22 operates at high frequency, conventional SPWM control, unipolar modulation or bipolar modulation can be used.

[0064] Please see Figure 8 , Figure 8 This is a schematic diagram of the phase-shift control waveform of the second series resonant converter circuit provided in this application. In this embodiment, as... Figure 8 As shown, the time by which the leading edge of the twentieth switch S20 on the secondary side of the second series resonant converter circuit 12 lags behind the leading edge of the eleventh switch S11 by the switching period multiplied by 2π is called the phase shift angle. Similarly, when the second series resonant converter circuit 12 operates at the resonant frequency point, and the phase shift angle is... When set to 0, it operates at its optimal efficiency, at which point its efficiency is highest and it can be considered a DC transformer.

[0065] Please see Figure 9 , Figure 9 yes Figure 7 A schematic diagram of the drive signal for a quasi-single-stage micro inverter. Figure 7 The drive state of the quasi-single-stage micro inverter 100 corresponding to the embodiment is as follows: Figure 9 As shown, where V M The mode switching voltage mentioned above is used for the full-bridge inverter circuit 22. Controlling the third switch S3 and the sixth switch S6 to be on or controlling the fourth switch S4 and the fifth switch S5 to be on can make the full-bridge inverter circuit 22 work in the optimal efficiency condition, at which time its efficiency is the highest.

[0066] Optionally, please refer to Figure 10 , Figure 10 This is a schematic diagram of the sixth embodiment of the quasi-single-stage microinverter provided in this application. Figure 10As shown, the boost converter circuit of this embodiment includes a second series resonant converter circuit 12, and the buck converter circuit includes a buck chopper circuit 23 and a power frequency folding bridge circuit 40. The input terminal of the second series resonant converter circuit 12 is coupled to the DC terminal, the output terminal of the second series resonant converter circuit 12 is coupled to the input terminal of the buck chopper circuit 23, the output terminal of the buck chopper circuit 23 is coupled to the input terminal of the power frequency folding bridge circuit 40, and the output terminal of the power frequency folding bridge circuit is coupled to the grid terminal.

[0067] Optionally, such as Figure 10 As shown, the circuit structure and connection relationship of the second series resonant converter circuit 12 in this embodiment are similar to those of the previous embodiment. Figure 7 The circuit structure and connection relationship of the second series resonant converter circuit 12 in the embodiment are exactly the same.

[0068] like Figure 7 As shown, the buck chopper circuit 23 includes a 21st switch S21, a 22nd switch S22, a buck inductor Lbuck, and a 3rd capacitor Cbuck. The first terminal of the 21st switch S21 is connected to the positive output terminal of the second series resonant converter circuit 12. The second terminal of the 21st switch S21 is connected to the first terminal of the buck inductor Lbuck and the first terminal of the 22nd switch S22. The second terminal of the buck inductor Lbuck is connected to the first terminal of the output capacitor Cbuck. The second terminal of the 22nd switch S22 and the second terminal of the output capacitor Cbuck are coupled and grounded. The two ends of the output capacitor Cbuck serve as the output terminals of the buck chopper circuit 23 and are connected to the input terminals of the power frequency folding bridge circuit 40.

[0069] The power frequency folding bridge circuit 40 includes a seventh switch S7, an eighth switch S8, a ninth switch S9, a tenth switch S10, and the LC filter circuit 30 mentioned above. The output terminal of the step-down chopper circuit 23 is connected to the first terminal of the seventh switch S7 and the first terminal of the ninth switch S9. The second terminal of the seventh switch S7 is connected to the first terminal of the eighth switch S8. The second terminal of the ninth switch S9 is connected to the first terminal of the tenth switch S10. The second terminals of the eighth switch S8 and the tenth switch S10 are coupled and grounded. The connection between the second terminal of the seventh switch S7 and the first terminal of the eighth switch S8, and the connection between the second terminal of the ninth switch S9 and the first terminal of the tenth switch S10, serve as the output terminals of the power frequency folding bridge circuit 40 and are connected to the power grid terminal through the LC filter circuit 30.

[0070] In this embodiment, when the absolute value of the grid voltage is greater than the mode switching voltage, the second series resonant converter circuit 12 is controlled to perform boost operation. At this time, the phase shift angle of the second series resonant converter circuit 12 can be set based on the boost requirement. And set the phase shift angle of the second series resonant converter circuit 12. At this time, it is necessary to adjust the phase angle. Set to greater than 0.

[0071] When the absolute value of the grid voltage is greater than the mode switching voltage, it is necessary to control the buck chopper circuit 23 and the power frequency switching bridge circuit 40 to operate in the optimal efficiency condition. At this time, controlling the buck chopper circuit 23 and the power frequency switching bridge circuit 40 to operate in the optimal efficiency condition means controlling the seventh switch S7 and the tenth switch S10 of the power frequency switching bridge circuit 40 to be on or the eighth switch S8 and the ninth switch S9 to be on.

[0072] When the absolute value of the grid voltage is less than the mode switching voltage, it is necessary to control the second series resonant converter circuit 12 to operate in the optimal efficiency condition, that is, to control the second series resonant converter circuit 12 to operate at the resonant frequency point, and to adjust the phase shift angle. When set to 0, the second series resonant converter circuit 12 can be regarded as a DC transformer.

[0073] When the absolute value of the grid voltage is less than the mode switching voltage, the step-down chopper circuit 23 needs to be controlled to step down the voltage, and grid connection is achieved through the power frequency folding bridge circuit 40.

[0074] Furthermore, based on all the embodiments described above, in this application, the switches in the quasi-single-stage micro inverter 100 of all the above embodiments can be any switches such as metal-oxide-semiconductor field-effect transistors (MOSFETs), gallium nitride-based light-emitting diodes, silicon carbide metal-oxide-semiconductor field-effect transistors, and insulated gate bipolar transistors (IGBTs) with anti-parallel diodes. The series resonant converter circuits in all the above embodiments can be replaced with series-parallel resonant converter circuits, dual active bridge converter circuits, or other isolated converter circuits. The specific control method of the converter circuits is not limited, as long as boost or buck conversion can be achieved; frequency conversion control, duty cycle control, or phase shift control are all acceptable.

[0075] Optionally, this application further proposes an electrical appliance; please refer to [link to relevant documentation]. Figure 11 , Figure 11 This is a schematic diagram of the structure of an embodiment of the electronic device provided in this application. Figure 11 As shown, the electronic device 200 of this embodiment includes the quasi-single-stage micro inverter 100 and controller 110 of the above embodiments.

[0076] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A quasi-single-stage micro inverter, characterized in that, It includes a boost converter circuit and a buck converter circuit, wherein the boost converter circuit and the buck converter circuit are coupled together, one of the boost converter circuit and the buck converter circuit is coupled to the mains terminal, and the other of the boost converter circuit and the buck converter circuit is coupled to the DC terminal. Specifically, if the absolute value of the grid voltage is less than the mode switching voltage, the buck converter circuit is controlled to perform buck operation and the boost converter circuit is controlled to operate at the optimal efficiency condition; if the absolute value of the grid voltage is greater than the mode switching voltage, the boost converter circuit is controlled to perform boost operation and the buck converter circuit is controlled to operate at the optimal efficiency condition.

2. The quasi-single-stage micro inverter according to claim 1, characterized in that, At least one of the boost converter circuit and the buck converter circuit is provided with an isolation transformer.

3. The quasi-single-stage micro inverter according to claim 2, characterized in that, The value of the mode switching voltage satisfies: The mode switching voltage is set as the product of the fixed gain of the boost converter circuit and the buck converter circuit, the rated voltage of the DC terminal component, and the turns ratio of the isolation transformer.

4. The quasi-single-stage micro inverter according to claim 1, characterized in that, The boost converter circuit includes a DC-DC boost converter circuit, and the buck converter circuit includes a first series resonant converter circuit. The input terminal of the DC-DC boost converter circuit is coupled to the DC terminal, and the output terminal of the DC-DC boost converter circuit is coupled to the input terminal of the first series resonant converter circuit. The output terminal of the first series resonant converter circuit is coupled to the grid terminal.

5. The quasi-single-stage micro inverter according to claim 4, characterized in that, The DC-DC boost converter circuit includes a first capacitor, a second capacitor, a first inductor, a first switch, and a second switch. The first terminal of the first capacitor is connected to the first terminal of the first inductor. The second terminal of the first inductor is connected to the first terminal of the first switch and the first terminal of the second switch. The second terminal of the second switch is connected to the first terminal of the second capacitor. The second terminals of the first capacitor, the first switch, and the second capacitor are grounded. The two terminals of the first capacitor serve as the input terminals of the DC-DC boost converter circuit and are coupled to the DC terminal. The two terminals of the second capacitor serve as the output terminals of the DC-DC boost converter circuit and are coupled to the input terminals of the first series resonant converter circuit. When the DC-DC boost converter circuit operates under the optimal efficiency condition, the first switch is open and the second switch is on; when the DC-DC boost converter circuit performs boost operation, the first switch is switched on and off at high frequency, and the second switch is complementary to the first switch; when the first series resonant converter circuit operates under the optimal efficiency condition, the first series resonant converter circuit operates at the resonant frequency point and the phase shift angle is 0.

6. The quasi-single-stage micro inverter according to claim 1, characterized in that, The boost converter circuit includes a second series resonant converter circuit, and the buck converter circuit includes a full-bridge inverter circuit. The input terminal of the second series resonant converter circuit is coupled to the DC terminal, the output terminal of the second series resonant converter circuit is coupled to the input terminal of the full-bridge inverter circuit, and the output terminal of the full-bridge inverter circuit is coupled to the grid terminal.

7. The quasi-single-stage micro inverter according to claim 6, characterized in that, The full-bridge inverter circuit includes a third switch, a fourth switch, a fifth switch, and a sixth switch. Wherein, the output terminal of the second series resonant converter circuit is connected to the first terminal of the third switch and the first terminal of the fifth switch, the second terminal of the third switch is connected to the first terminal of the fourth switch, the second terminal of the fifth switch is connected to the first terminal of the sixth switch, the second terminal of the fourth switch and the second terminal of the sixth switch are coupled and grounded, and the connection point between the second terminal of the third switch and the first terminal of the fourth switch and the connection point between the second terminal of the fifth switch and the first terminal of the sixth switch serve as the output terminal of the full-bridge inverter circuit; Wherein, when the second series resonant converter circuit operates under the optimal efficiency condition, the second series resonant converter circuit operates at the resonant frequency point and the phase shift angle is 0; when the full-bridge inverter circuit operates under the optimal efficiency condition, the third switch and the sixth switch are always on or the fourth switch and the fifth switch are always on.

8. The quasi-single-stage micro inverter according to claim 1, characterized in that, The boost converter circuit includes a second series resonant converter circuit, and the buck converter circuit includes a buck chopper circuit and a power frequency folding bridge circuit. The input terminal of the second series resonant converter circuit is coupled to the DC terminal, the output terminal of the second series resonant converter circuit is coupled to the input terminal of the buck chopper circuit, the output terminal of the buck chopper circuit is coupled to the input terminal of the power frequency folding bridge circuit, and the output terminal of the power frequency folding bridge circuit is coupled to the grid terminal.

9. The quasi-single-stage micro inverter according to claim 8, characterized in that, The power frequency folding bridge circuit includes a seventh switch, an eighth switch, a ninth switch, and a tenth switch. Wherein, the output terminal of the step-down chopper circuit is connected to the first terminal of the seventh switch and the first terminal of the ninth switch, the second terminal of the seventh switch is connected to the first terminal of the eighth switch, the second terminal of the ninth switch is connected to the first terminal of the tenth switch, the second terminal of the eighth switch and the second terminal of the tenth switch are coupled and grounded, and the connection point between the second terminal of the seventh switch and the first terminal of the eighth switch and the connection point between the second terminal of the ninth switch and the first terminal of the tenth switch serve as the output terminal of the power frequency folding bridge circuit; When the second series resonant converter circuit operates under the optimal efficiency condition, it operates at the resonant frequency and the phase shift angle is 0. When the buck chopper circuit and the power frequency folding bridge circuit operate under the optimal efficiency condition, the seventh switch and the tenth switch are always on, or the eighth switch and the ninth switch are always on.

10. An electronic device, characterized in that, Includes the quasi-single-stage micro inverter and controller as described in any one of claims 1-9.

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