Photovoltaic inverter and auxiliary power supply thereof

Abstract

The utility model relates to the technical field of inverters, in particular to a photovoltaic inverter and an auxiliary power supply thereof. The auxiliary power supply comprises a first voltage output end, a flyback transformer, a plurality of first capacitors and a plurality of first rectifier diodes, the flyback transformer is provided with a primary side and a first secondary side, the primary side of the flyback transformer is connected with an external mains supply, and each first capacitor is correspondingly connected with one first rectifier diode in parallel; the multiple first rectifier diodes are sequentially connected in series, the positive electrode after series connection is connected with the first secondary side of the flyback transformer, and the negative electrode is connected with a first voltage output end which is used for charging an external bus capacitor. According to the invention, high voltage is output and supplied to the external bus capacitor, the voltage stress of the plurality of first rectifier diodes is relatively balanced, each first rectifier diode retains high margin, the possibility of damage is reduced, and normal work of the auxiliary power supply at the mains supply side is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to inverter technical field, especially a photovoltaic inverter and its auxiliary power supply. BACKGROUND

[0002] The photovoltaic inverter can convert the variable DC voltage generated by the photovoltaic solar panel into the commercial frequency AC power, which can be fed back to the commercial power transmission system or used for off-grid power grid.

[0003] In the off-grid photovoltaic inverter, multiple or multi-stage auxiliary power supplies are generally set to take power from different power sources to ensure that the machine can be normally started under various working conditions and there is no power short circuit state after failure.

[0004] Generally, the auxiliary power supply on the commercial power side of the photovoltaic inverter rectifies the AC power of the power grid and transmits it to the flyback transformer for voltage conversion, and the secondary side of the flyback transformer generates a suitable voltage to supply power to other circuits of the photovoltaic inverter.

[0005] However, due to the characteristics of the flyback transformer, the reflected voltage thereof causes the voltage stress of multiple rectifier diodes on the secondary side to be unbalanced, the voltage stress of some rectifier diodes is too high, and the rectifier diodes are easily damaged, resulting in abnormal operation of the auxiliary power supply on the commercial power side. SUMMARY

[0006] The technical problem to be solved by the embodiments of the utility model lies in providing a photovoltaic inverter and its auxiliary power supply to solve the problem that the voltage stress of multiple rectifier diodes of the auxiliary power supply on the commercial power side of the photovoltaic inverter in the prior art is unbalanced, the voltage stress of some rectifier diodes is too high, the rectifier diodes are easily damaged, and the auxiliary power supply on the commercial power side is abnormally operated.

[0007] The utility model discloses a kind of auxiliary power supplies of photovoltaic inverter, including first voltage output end, flyback transformer, multiple first capacitors and multiple first rectifier diodes, the flyback transformer is equipped with primary side and first secondary side, the primary side of the flyback transformer is connected with external commercial power, every first capacitor is corresponding with a first rectifier diode in parallel, multiple first rectifier diodes are connected in series in sequence and the positive pole after series connection is connected with the first secondary side of the flyback transformer, negative pole connects the first voltage output end, the first voltage output end is used to charge external bus capacitor.

[0008] Optionally, the flyback transformer further comprises a second secondary side, and the auxiliary power supply further comprises a second voltage output end, a second capacitor and a plurality of second rectifier diodes, the plurality of second rectifier diodes are connected in parallel and connected in parallel with the second capacitor, the positive pole of the plurality of second rectifier diodes connected in parallel is connected with the second voltage output end, and the second voltage output end is used for supplying power for the main auxiliary power supply on the battery side.

[0009] Optionally, the flyback transformer further comprises a third secondary side, and the auxiliary power supply further comprises a master control chip, a third voltage output end, a third capacitor and a third rectifier diode, the third capacitor and the third rectifier diode are connected in parallel, the positive pole of the third rectifier diode is connected with the third voltage output end, and the third voltage output end is used for supplying power for the master control chip.

[0010] Optionally, the auxiliary power supply further comprises an anti-backflow diode and a fourth capacitor, the anti-backflow diode is connected in parallel with the fourth capacitor, the negative pole of the plurality of first rectifier diodes connected in series is connected with the positive pole of the anti-backflow diode, and the negative pole of the anti-backflow diode is connected with the first voltage output end.

[0011] Optionally, the auxiliary power supply further comprises a switch tube, a first resistor, a fifth capacitor and a sixth capacitor, the first resistor, the fifth capacitor and the sixth capacitor are connected in series, the other end of the first resistor is connected with the drain of the switch tube, the other end of the sixth capacitor is connected with the source of the switch tube, and the gate of the switch tube is connected with the master control chip.

[0012] Optionally, the auxiliary power supply further comprises a fourth rectifier diode, a third resistor and an eighth capacitor, the third resistor and the eighth capacitor are connected in parallel, the first end of the parallel connection is connected with the first end of the primary side of the flyback transformer and external mains, the second end of the parallel connection is connected with the negative pole of the fourth rectifier diode, the positive pole of the fourth rectifier diode is connected with the second end of the primary side of the flyback transformer and the drain of the switch tube, and the source of the switch tube is also connected with the ground.

[0013] Optionally, the auxiliary power supply further comprises a plurality of first resistor units, each first resistor unit is connected in parallel with a corresponding first rectifier diode after being connected in series with a corresponding first capacitor.

[0014] Optionally, the auxiliary power supply further comprises a second resistor unit, the second resistor unit is connected in parallel with a plurality of second rectifier diodes after being connected in series with the second capacitor.

[0015] Optionally, the auxiliary power supply further comprises a third resistor unit, the third resistor unit is connected in parallel with the third rectifier diode after being connected in series with the third capacitor.

[0016] The utility model discloses still a kind of photovoltaic inverter, including the auxiliary power supply of the photovoltaic inverter as described above.

[0017] Compared with prior art, the auxiliary power supply of the photovoltaic inverter provided by the utility model embodiment has the beneficial effects that: the auxiliary power supply of the photovoltaic inverter is provided with a first voltage output end, a flyback transformer, a plurality of first capacitors and a plurality of first rectifier diodes, the plurality of first rectifier diodes are connected in series and the positive electrode after series connection is connected to the first secondary side of the flyback transformer, and the negative electrode is connected to the first voltage output end, so that the first secondary side of the flyback transformer can output higher voltage after rectification by the plurality of first rectifier diodes, to supply external bus capacitor; each capacitor is connected in parallel with a first rectifier diode, so that the voltage stress of the plurality of first rectifier diodes is more balanced, so that each first rectifier diode retains higher margin, reduces the possibility of damage, and ensures the normal work of the auxiliary power supply on the side of commercial power. BRIEF DESCRIPTION OF DRAWINGS

[0018] The technical solutions of the utility model will be further described in detail below with reference to the drawings and embodiments, and in the drawings:

[0019] Figure 1 is part of the circuit schematic diagram of the auxiliary power supply of the photovoltaic inverter provided by the utility model embodiment;

[0020] Figure 2 is another part of the circuit schematic diagram of the auxiliary power supply of the photovoltaic inverter provided by the utility model embodiment.

[0021] In the drawings, the reference signs are:

[0022] 10, first voltage output end; 20, second voltage output end; 30, third voltage output end; 40, first resistance unit; 50, second resistance unit; 60, third resistance unit; 70, fourth resistance unit; T1, flyback transformer; C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; C5, fifth capacitor; C6, sixth capacitor; C8, eighth capacitor; D1, first rectifier diode; D2, second rectifier diode; D3, third rectifier diode; D4, fourth rectifier diode; D5, anti-backflow diode; Q1, switch tube; R1, first resistance; R3, third resistance; R4, fourth resistance; R5, fifth resistance; R6, sixth resistance. DETAILED DESCRIPTION

[0023] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The preferred embodiments of the utility model will be described in detail with reference to the drawings.

[0024] The utility model discloses an auxiliary power supply of photovoltaic inverter, which comprises a first voltage output end 10, a flyback transformer T1, a plurality of first capacitors C1 and a plurality of first rectifier diodes D1. Figure 1 As shown, the auxiliary power supply comprises a first voltage output end 10, a flyback transformer T1, a plurality of first capacitors C1 and a plurality of first rectifier diodes D1. The flyback transformer T1 is provided with a primary side and a first secondary side. The primary side of the flyback transformer T1 is connected to external mains. Each first capacitor C1 is connected in parallel with a first rectifier diode D1. The plurality of first rectifier diodes D1 are connected in series and the positive poles of the series-connected first rectifier diodes D1 are connected to the first secondary side of the flyback transformer T1, and the negative poles are connected to the first voltage output end 10. The first voltage output end 10 is used to charge the external bus capacitor.

[0025] According to the embodiment of the present application, the first voltage output end 10, the flyback transformer T1, the plurality of first capacitors C1 and the plurality of first rectifier diodes D1 are arranged. The plurality of first rectifier diodes D1 are connected in series and the positive poles of the series-connected first rectifier diodes D1 are connected to the first secondary side of the flyback transformer T1, and the negative poles are connected to the first voltage output end 10. The first secondary side of the flyback transformer T1 can output a higher voltage after rectification by the plurality of first rectifier diodes D1, which is used to supply the external bus capacitor. Each capacitor is connected in parallel with a first rectifier diode D1, so that the voltage stress of the plurality of first rectifier diodes D1 is balanced. Each first rectifier diode D1 has a higher margin, which reduces the possibility of damage and ensures the normal operation of the auxiliary power supply on the mains side.

[0026] The first voltage output end 10 can be connected to the bus capacitor in the photovoltaic inverter to charge the bus capacitor. As an example, the voltage output by the first secondary side of the flyback transformer T1 is rectified by the plurality of first rectifier diodes D1 to output a voltage of 170V, which is used to charge the external bus capacitor. The external mains is rectified to obtain a direct current, which is input to the primary side of the flyback transformer T1.

[0027] The number of first rectifier diodes D1 can be two, three or more than three. Correspondingly, the number of first capacitors C1 can be two, three or more than three. The number of first rectifier diodes D1 can be selected according to the voltage of the external bus capacitor and the reflected voltage of the flyback transformer T1. As an example, three first rectifier diodes D1 are arranged, and three first capacitors C1 are correspondingly arranged. Each first capacitor C1 is connected in parallel with a first rectifier diode D1. After testing, for the first rectifier diode D1 with a specification of 1000V, the voltage stress of the three first rectifier diodes D1 is 850V, 172V and 268V respectively when no first capacitor C1 is connected. After connecting the first capacitor C1 in parallel, the voltage stress of the three first rectifier diodes D1 is 520V, 496V and 472V respectively. The voltage stress is balanced and a higher margin is reserved. The first capacitor C1 is arranged in this way, and the cost is relatively low.

[0028] In this embodiment, referring to Figure 1 , the flyback transformer T1 further includes a second secondary side, and the auxiliary power supply further includes a second voltage output end 20, a second capacitor C2 and a plurality of second rectifier diodes D2, the plurality of second rectifier diodes D2 are connected in parallel and connected in parallel with the second capacitor C2, the positive electrode of the plurality of second rectifier diodes D2 connected in parallel is connected to the second secondary side of the flyback transformer T1, and the negative electrode is connected to the second voltage output end 20, and the second voltage output end 20 is used to supply power to the main auxiliary power supply on the battery side.

[0029] Through the second secondary side of the flyback transformer T1, the plurality of second rectifier diodes D2 and the second capacitor C2 can rectify and output appropriate voltage to supply power to the main auxiliary power supply on the battery side. Among them, by connecting the plurality of second rectifier diodes D2 in parallel, a higher output power can be withstood, so that the second voltage output end 20 can output higher power to supply power to the main auxiliary power supply on the battery side. The second capacitor C2 and the second rectifier diode D2 can absorb the voltage stress peak of the plurality of second rectifier diodes D2, reduce the voltage stress of the second rectifier diode D2, and prolong the service life of the second rectifier diode D2.

[0030] For example, the voltage output by the second secondary side of the flyback transformer T1 is rectified by the plurality of second rectifier diodes D2 to output a voltage of 68V to supply power to the main auxiliary power supply on the battery side.

[0031] Further, the auxiliary power supply further includes an anti-backflow diode D5 and a fourth capacitor C4, the anti-backflow diode D5 is connected in parallel with the fourth capacitor C4, the negative electrode of the plurality of first rectifier diodes D1 connected in series is connected to the positive electrode of the anti-backflow diode D5, and the negative electrode of the anti-backflow diode D5 is connected to the first voltage output end 10.

[0032] By setting the anti-backflow diode D5, the reverse voltage impact of the external bus capacitor can be prevented, the damage of the reverse voltage impact to the elements of the auxiliary power supply can be avoided, the service life of the auxiliary power supply is prolonged, the stability of the auxiliary power supply is improved, and the circuit structure is simple. The fourth capacitor C4 is connected in parallel with the anti-backflow diode D5, and is used to absorb the voltage stress peak of the anti-backflow diode D5, reduce the voltage stress of the anti-backflow diode D5, and prolong the service life of the anti-backflow diode D5.

[0033] In this embodiment, referring to Figure 1 , the flyback transformer T1 further includes a third secondary side, and the auxiliary power supply further includes a main control chip (not shown in the figure), a third voltage output end 30, a third capacitor C3 and a third rectifier diode D3, the third capacitor C3 and the third rectifier diode D3 are connected in parallel, the positive electrode of the third rectifier diode D3 is connected to the third secondary side of the flyback transformer T1, and the negative electrode is connected to the third voltage output end 30, and the third voltage output end 30 is used to supply power to the main control chip.

[0034] The third secondary side of the flyback transformer T1 can cooperate with the third rectifier diode D3 and the second capacitor C2 to rectify an appropriate voltage and output the appropriate voltage to power the main control chip of the auxiliary power supply, and the main control chip is used to control the output voltage and current of the flyback transformer T1. Among them, compared with the charging voltage of the bus capacitor and the power supply voltage of the battery side, the power supply voltage of the main control chip is lower, so a third rectifier diode D3 is used to rectify the output voltage of the third secondary side, so as to realize the output of appropriate voltage with a simpler circuit structure. The third capacitor C3 is connected in parallel with the third rectifier diode D3, which can absorb the voltage stress peak of the third rectifier diode D3, reduce the voltage stress of the third rectifier diode D3, and prolong the service life of the third rectifier diode D3.

[0035] For example, the voltage output by the third secondary side of the flyback transformer T1 is rectified by the third rectifier diode D3 to output a voltage of 15V to power the main control chip.

[0036] In this embodiment, referring to Figure 1 and Figure 2 The auxiliary power supply further comprises a switch tube Q1, a first resistor R1, a fifth capacitor C5 and a sixth capacitor C6, the first resistor R1, the fifth capacitor C5 and the sixth capacitor C6 are connected in series, one end of the first resistor R1 is connected to the drain of the switch tube Q1, the other end of the sixth capacitor C6 is connected to the source of the switch tube Q1, and the gate of the switch tube Q1 is connected to the main control chip.

[0037] The switch tube Q1 can be controlled by the main control chip to be turned on or turned off, thereby adjusting the output voltage of the flyback transformer. It can be realized by conventional technology, which will not be described here. The first resistor R1, the fifth capacitor C5 and the sixth capacitor C6 form a filter circuit, which can absorb the voltage stress peak of the switch tube Q1, reduce the voltage stress of the switch tube Q1, and prolong the service life of the switch tube Q1.

[0038] Further, the auxiliary power supply further comprises a fourth rectifier diode D4, a third resistor R3 and an eighth capacitor C8, the third resistor R3 and the eighth capacitor C8 are connected in parallel, and the first end of the parallel connection is connected to the first end of the primary side of the flyback transformer T1 and the external power supply, the second end of the parallel connection is connected to the negative electrode of the fourth rectifier diode D4, the positive electrode of the fourth rectifier diode D4 is connected to the second end of the primary side of the flyback transformer T1 and the drain of the switch tube Q1, and the source of the switch tube Q1 is also connected to the ground.

[0039] By setting the fourth rectifier diode D4, the third resistor R3 and the eighth capacitor C8, the voltage stress peak of the primary side of the flyback transformer T1 can be absorbed, and the stability of the circuit connected to the primary side of the flyback transformer T1 can be ensured.

[0040] In this embodiment, referring to Figure 1 The auxiliary power supply further comprises a plurality of first resistance units 40, each first resistance unit 40 is connected in series with a first capacitor C1 and connected in parallel with a corresponding first rectifier diode D1.

[0041] By setting the first resistance unit 40, the voltage stress peak of the switch tube Q1 of the primary side of the flyback transformer T1 can be absorbed, and the temperature of the first capacitor C1 and the first rectifier diode D1 can be debugged to avoid the working temperature of the first capacitor C1 and the first rectifier diode D1 being too high. The designer can select the appropriate resistance value according to the needs. In specific implementation, the first resistance unit 40 can include at least one fourth resistor R4. When two or more fourth resistors R4 are set, the plurality of fourth resistors R4 are connected in parallel and connected in series with the first capacitor C1. The designer can set the number of fourth resistors R4 according to the needs.

[0042] In this embodiment, referring to Figure 1 The auxiliary power supply further comprises a second resistance unit 50, which is connected in series with a second capacitor C2 and connected in parallel with a plurality of second rectifier diodes D2.

[0043] By setting the second resistance unit 50, the voltage stress peak of the switch tube Q1 of the primary side of the flyback transformer T1 can also be absorbed, and the temperature of the second capacitor C2 and the second rectifier diode D2 can be debugged to avoid the working temperature of the second capacitor C2 and the second rectifier diode D2 being too high. The designer can select the appropriate resistance value according to the needs. In specific implementation, the second resistance unit 50 can include at least one fifth resistor R5. When two or more fifth resistors R5 are set, the plurality of fifth resistors R5 are connected in parallel and connected in series with the second capacitor C2. The designer can set the number of fifth resistors R5 according to the needs.

[0044] In this embodiment, referring to Figure 1 The auxiliary power supply further comprises a third resistance unit 60, which is connected in series with a third capacitor C3 and connected in parallel with a third rectifier diode D3.

[0045] By setting the third resistance unit 60, the voltage stress peak of the switch tube Q1 of the primary side of the flyback transformer T1 can also be absorbed, and the temperature of the third capacitor C3 and the third rectifier diode D3 can be debugged. The designer can select the appropriate resistance value according to the needs. In specific implementation, the third resistance unit 60 can include at least one sixth resistor R6. When two or more sixth resistors R6 are set, the plurality of sixth resistors R6 are connected in parallel and connected in series with the third capacitor C3. The designer can set the number of sixth resistors R6 according to the needs.

[0046] The auxiliary power supply can further include a fourth resistance unit 70, which is connected in series with the fourth capacitor C4 and then connected in parallel with the anti-inrush diode D5.

[0047] By setting the fourth resistance unit 70, the voltage stress peak of the switch tube Q1 of the primary side of the flyback transformer T1 can also be helped to be absorbed, and the temperature of the fourth capacitor C4 and the anti-inrush diode D5 can be adjusted. Designers can select appropriate resistance values as needed. In a specific implementation, the third resistance unit 60 can include at least one seventh resistance. When two or more seventh resistances are provided, the multiple seventh resistances are connected in parallel and then connected in series with the fourth capacitor C4. Designers can set the number of seventh resistances as needed.

[0048] The embodiments of the present application also provide a photovoltaic inverter, which includes the auxiliary power supply of the photovoltaic inverter as described above.

[0049] In the photovoltaic inverter of the embodiments of the present application, the first voltage output end 10, the flyback transformer T1, the multiple first capacitors C1, and the multiple first rectifier diodes D1 are provided. The multiple first rectifier diodes D1 are connected in series and the positive pole of the series connection is connected to the first secondary side of the flyback transformer T1, and the negative pole is connected to the first voltage output end 10. The first secondary side of the flyback transformer T1 can output a higher voltage after being rectified by the multiple first rectifier diodes D1, which is supplied to the external bus capacitor. Each capacitor is connected in parallel with a first rectifier diode D1, so that the voltage stress of the multiple first rectifier diodes D1 is more balanced, so that each first rectifier diode D1 retains a higher margin, reduces the possibility of damage, and ensures the normal work of the auxiliary power supply on the power side.

[0050] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. For those skilled in the art, the technical solutions recorded in the above embodiments can be modified, or some technical features can be replaced by equivalents. All these modifications and replacements should be within the protection scope of the claims of the present application.

Claims

1. An auxiliary power supply for a photovoltaic inverter, characterized by, The auxiliary power supply comprises a first voltage output end, a flyback transformer, a plurality of first capacitors and a plurality of first rectifier diodes, the flyback transformer is provided with a primary side and a first secondary side, the primary side of the flyback transformer is connected with external mains, each first capacitor is connected in parallel with a first rectifier diode, the plurality of first rectifier diodes are connected in series, the positive pole of the series connection is connected with the first secondary side of the flyback transformer, and the negative pole is connected with the first voltage output end, and the first voltage output end is used for charging an external bus capacitor.

2. Auxiliary power supply for a photovoltaic inverter according to claim 1, characterized in that The flyback transformer further comprises a second secondary side, and the auxiliary power supply further comprises a second voltage output end, a second capacitor and a plurality of second rectifier diodes, the plurality of second rectifier diodes are connected in parallel and connected in parallel with the second capacitor, the positive pole of the parallel connection of the plurality of second rectifier diodes is connected with the second secondary side of the flyback transformer, and the negative pole is connected with the second voltage output end, and the second voltage output end is used for supplying power to a main auxiliary power supply on the battery side.

3. Auxiliary power supply for a photovoltaic inverter according to claim 2, characterized in that The flyback transformer further comprises a third secondary side, and the auxiliary power supply further comprises a master control chip, a third voltage output end, a third capacitor and a third rectifier diode, the third capacitor and the third rectifier diode are connected in parallel, the positive pole of the third rectifier diode is connected with the third secondary side of the flyback transformer, and the negative pole is connected with the third voltage output end, and the third voltage output end is used for supplying power to the master control chip.

4. Auxiliary power supply for a photovoltaic inverter according to any of claims 1-3, characterized in that, The auxiliary power supply further comprises an anti-backflow diode and a fourth capacitor, the anti-backflow diode is connected in parallel with the fourth capacitor, the negative pole of the series connection of the plurality of first rectifier diodes is connected with the positive pole of the anti-backflow diode, and the negative pole of the anti-backflow diode is connected with the first voltage output end.

5. The auxiliary power supply for a photovoltaic inverter according to claim 3, characterized in that, The auxiliary power supply further comprises a switch tube, a first resistor, a fifth capacitor and a sixth capacitor, the first resistor, the fifth capacitor and the sixth capacitor are connected in series, the other end of the first resistor is connected with the drain of the switch tube, the other end of the sixth capacitor is connected with the source of the switch tube, and the gate of the switch tube is connected with the master control chip.

6. The auxiliary power supply for a photovoltaic inverter according to claim 5, characterized in that, The auxiliary power supply further comprises a fourth rectifier diode, a third resistor and an eighth capacitor, the third resistor and the eighth capacitor are connected in parallel, the first end of the parallel connection is connected with the first end of the primary side of the flyback transformer and external mains, the second end of the parallel connection is connected with the negative pole of the fourth rectifier diode, the positive pole of the fourth rectifier diode is connected with the second end of the primary side of the flyback transformer and the drain of the switch tube, and the source of the switch tube is further connected with the ground.

7. The auxiliary power supply for a photovoltaic inverter according to claim 5, characterized in that, The auxiliary power supply further comprises a plurality of first resistor units, each first resistor unit is connected in series with a corresponding first capacitor and connected in parallel with a corresponding first rectifier diode.

8. The auxiliary power supply for a photovoltaic inverter according to claim 7, characterized in that, The auxiliary power supply further comprises a second resistor unit, the second resistor unit is connected in series with the second capacitor and connected in parallel with a plurality of second rectifier diodes.

9. The auxiliary power supply for a photovoltaic inverter according to claim 8, characterized in that, The auxiliary power supply further comprises a third resistor unit, the third resistor unit is connected in series with the third capacitor and connected in parallel with the third rectifier diode.

10. A photovoltaic inverter, characterized by The auxiliary power supply comprises the photovoltaic inverter as claimed in any one of claims 1-9.

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