Photovoltaic inverter

Abstract

The invention provides a photovoltaic inverter, and belongs to the technical field of power electronics. The photovoltaic inverter provided by the invention comprises a DC / DC conversion circuit and a first absorption circuit. Wherein the DC / DC conversion circuit comprises a bypass diode connected between the positive electrode of the input end and the positive electrode of the output end, and the first absorption circuit is connected with the bypass diode in parallel. When the input end of the DC / DC conversion circuit is subjected to negative differential-mode lightning stroke and backward voltage is generated at the two ends of the bypass diode, the first absorption circuit can absorb the energy of the backward voltage. Therefore, the amplitude of the backward voltage at the two ends of the bypass diode can be effectively reduced, the bypass diode is prevented from being damaged due to the overvoltage of the backward voltage, and the safety and the stability of the photovoltaic inverter during working are ensured.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly to a photovoltaic inverter. Background Art

[0002] The three-level boost circuit is a commonly used boost circuit in a photovoltaic inverter. To cope with positive differential-mode lightning strikes, a bypass diode is also provided between the positive pole of the input end and the positive pole of the output end of the three-level boost circuit.

[0003] However, when the input end of the three-level boost circuit is subjected to a negative differential-mode lightning strike, a negative voltage will be generated on the input capacitor at the input end. After the negative voltage is superimposed on the positive voltage of the output capacitor at the output end of the three-level boost circuit, it is easy to cause an overvoltage of the reverse voltage of the bypass diode, resulting in device damage. Summary of the Invention

[0004] This application provides a photovoltaic inverter, which can solve the technical problem that when the input end of the three-level boost circuit is subjected to a negative differential-mode lightning strike, it is easy to cause overvoltage damage to the bypass diode.

[0005] In a first aspect, a photovoltaic inverter is provided. The photovoltaic inverter includes: a direct current / direct current (DC / DC) conversion circuit and a first absorption circuit. The input end of the DC / DC conversion circuit is used to connect to a photovoltaic panel, and the output end is used to connect to a DC bus. The DC / DC conversion circuit is used to perform voltage conversion on the direct current provided by the photovoltaic panel and then output it. Moreover, the DC / DC conversion circuit includes: an input capacitor, a first diode, a second diode, a first switching tube, a second switching tube, an inductor, a flying capacitor, an output capacitor, and a bypass diode. Among them, the input capacitor is connected between the positive pole and the negative pole of the input end; the first diode, the second diode, the first switching tube, and the second switching tube are sequentially connected in series between the positive pole and the negative pole of the output end; one end of the inductor is connected to the positive pole of the input end, and the other end of the inductor is connected to the series node between the second diode and the first switching tube; one end of the flying capacitor is connected to the series node between the first diode and the second diode, and the other end of the flying capacitor is connected to the series node between the first switching tube and the second switching tube; the output capacitor is connected between the positive pole and the negative pole of the output end; the bypass diode is connected between the positive pole of the input end and the positive pole of the output end. When the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the polarity of the lightning strike voltage generated across the input capacitor is opposite to the polarity of the input end, and the voltage direction of the voltage after the lightning strike voltage is superimposed on the voltage across the output capacitor is opposite to the conduction direction of the bypass diode. The first absorption circuit is connected in parallel with the bypass diode and is used to absorb the energy of the above-mentioned superimposed voltage generated across the bypass diode.

[0006] Among them, the voltage direction refers to the direction from the high potential to the low potential. The high potential of the superimposed voltage is the negative electrode of the bypass diode, that is, the positive electrode of the output end, and the low potential is the positive electrode of the bypass diode, that is, the positive electrode of the input end. It can be seen from this that for the bypass diode, the superimposed voltage is a reverse voltage, and this reverse voltage will make the bypass diode in a reverse bias state. Moreover, if this reverse voltage exceeds the breakdown voltage of the bypass diode, it will cause the bypass diode to break down reversely, resulting in device damage. In the solution provided by this application, since the first absorption circuit connected in parallel with the bypass diode can effectively absorb the energy of this reverse voltage, the amplitude of this reverse voltage can be reduced, avoiding damage to the bypass diode due to overvoltage of the reverse voltage, and thus ensuring the stability and safety during the operation of the photovoltaic inverter.

[0007] Optionally, the first absorption circuit includes a first absorption capacitor. The first absorption capacitor can be composed of one or more capacitors, and among them, the multiple capacitors can be connected in series and / or in parallel.

[0008] It can be understood that when a reverse voltage is generated across the bypass diode due to negative differential-mode lightning strikes, the first absorption capacitor can be quickly charged, thereby storing the lightning energy in the form of electric field energy. Thus, it can effectively suppress the rapid rise of the reverse voltage across the bypass diode and keep the reverse voltage across the bypass diode within a relatively stable range, thereby achieving effective protection for the bypass diode.

[0009] Optionally, the first absorption circuit includes a series-connected first absorption capacitor and resistor. That is to say, the first absorption circuit can be a resistor-capacitor (RC) absorption circuit.

[0010] Among them, the first absorption capacitor can suppress the rapid rise of the reverse voltage across the bypass diode by charging, and the resistor can limit the charging current of the first absorption capacitor to avoid damage to other components in the circuit due to excessive charging current. It can be understood that the first absorption circuit can also be implemented by other passive devices or combinations of passive devices.

[0011] Optionally, the first absorption capacitor in the above first absorption circuit can be a capacitor in the microfarad (uF) range. For example, the capacitance value of the first absorption capacitor can be greater than or equal to 150 uF. By using a capacitor in the uF range, it can be ensured that when a reverse voltage is generated across the bypass diode, the first absorption capacitor can be quickly charged, thereby effectively suppressing the rising speed and amplitude of the reverse voltage.

[0012] Optionally, the first absorption circuit includes a transient voltage suppression (TVS) diode or a surge protection device (SPD). The breakdown voltages of the TVS and SPD can be slightly lower than the withstand voltage of the bypass diode, which refers to the maximum voltage that can be tolerated in the reverse bias state. Thus, not only can effective protection of the bypass diode be achieved, but false operation of the TVS and SPD can be avoided.

[0013] Among them, the positive electrode of the TVS diode can be connected to the positive electrode of the input terminal of the DC / DC conversion circuit, and the negative electrode can be connected to the positive electrode of the output terminal of the DC / DC conversion circuit. Based on this, when a reverse voltage is generated across the bypass diode due to a negative differential-mode lightning strike, if the reverse voltage across the bypass diode exceeds the breakdown voltage of the TVS diode, the TVS diode conducts and clamps the voltage, thereby effectively preventing the bypass diode from being reversely broken down.

[0014] For the scenario where the first absorption circuit is implemented using an SPD, when a reverse voltage is generated across the bypass diode due to a negative differential-mode lightning strike, since the SPD can utilize its own non-linear characteristics to discharge the energy of the reverse voltage (i.e., surge energy), it can effectively prevent the bypass diode from being damaged by the reverse voltage.

[0015] Optionally, the photovoltaic inverter further includes a second absorption circuit, which is connected in parallel with the input capacitor and is used to absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike.

[0016] Since the second absorption circuit can absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike, it can effectively slow down the rising rate of the lightning strike voltage (i.e., negative voltage) across the input capacitor and reduce the rising amplitude of the negative voltage. Correspondingly, after the negative voltage of the input capacitor is superimposed with the positive voltage of the output capacitor, it will not cause the bypass diode to be damaged due to reverse voltage overvoltage.

[0017] Optionally, the second absorption circuit includes a second absorption capacitor and a third diode connected in series. Among them, the third diode is reversely connected between the positive and negative electrodes of the input terminal of the DC / DC conversion circuit. For example, one end of the second absorption capacitor is connected to the positive electrode of the input terminal, the other end of the second absorption capacitor is connected to the negative electrode of the third diode, and the positive electrode of the third diode is connected to the negative electrode of the input terminal. Or, the negative electrode of the third diode is connected to the positive electrode of the input terminal, the positive electrode of the third diode is connected to one end of the second absorption capacitor, and the other end of the second absorption capacitor is connected to the negative electrode of the input terminal.

[0018] It can be understood that when the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the third diode can conduct, so that the second absorption capacitor is connected in parallel with the input capacitor. At this time, the lightning energy generated by the negative differential-mode lightning strike can charge both the second absorption capacitor and the input capacitor simultaneously, thereby effectively slowing down the rising speed of the negative voltage across the input capacitor, and further slowing down the rising speed of the reverse voltage across the bypass diode. Moreover, since the second absorption capacitor and the input capacitor are connected in parallel, which is equivalent to increasing the total capacitance of the input capacitor, it can also effectively reduce the rising amplitude of the negative voltage across the input capacitor, and further reduce the rising amplitude of the reverse voltage across the bypass diode, avoiding damage to the bypass diode due to overvoltage of the reverse voltage.

[0019] Optionally, the second absorption capacitor in the above second absorption circuit can also be a capacitor in the uF range. For example, the capacitance value of the second absorption capacitor can be greater than or equal to 100 uF. By using a capacitor in the uF range, it can be ensured that when the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the second absorption capacitor and the input capacitor connected in parallel can be quickly charged, thereby effectively suppressing the rising speed and rising amplitude of the negative voltage across the input capacitor.

[0020] Optionally, the photovoltaic inverter includes a plurality of DC / DC conversion circuits, and the photovoltaic inverter further includes a direct current / alternating current (DC / AC) conversion circuit. The output ends of the plurality of DC / DC conversion circuits are connected in parallel to a DC bus, and the DC bus is also connected to the DC end of the DC / AC conversion circuit. The AC end of the DC / AC conversion circuit is used to connect to the power grid. The DC / AC conversion circuit is used to convert the direct current output by the DC / DC conversion circuit into alternating current and then output it to the power grid. Among them, the DC / DC conversion circuit is also called the front-stage power conversion circuit, and the DC / AC conversion circuit is also called the rear-stage power conversion circuit.

[0021] In a second aspect, another photovoltaic inverter is provided, which includes a DC / DC conversion circuit and an absorption circuit. The input end of the DC / DC conversion circuit is used to connect to a photovoltaic panel, and the output end is used to connect to a DC bus. The DC / DC conversion circuit is used to convert the DC power provided by the photovoltaic panel and then output it to the DC bus. Moreover, the DC / DC conversion circuit includes an input capacitor, a first diode, a second diode, a first switching tube, a second switching tube, an inductor, a flying capacitor, an output capacitor, and a bypass diode. Among them, the input capacitor is connected between the positive and negative poles of the input end; the first diode, the second diode, the first switching tube, and the second switching tube are sequentially connected in series between the positive and negative poles of the output end; one end of the inductor is connected to the positive pole of the input end, and the other end of the inductor is connected to the series node between the second diode and the first switching tube; one end of the flying capacitor is connected to the series node between the first diode and the second diode, and the other end of the flying capacitor is connected to the series node between the first switching tube and the second switching tube; the output capacitor is connected between the positive and negative poles of the output end; the bypass diode is connected between the positive pole of the input end and the positive pole of the output end. When a negative differential-mode lightning strike occurs at the input end of the DC / DC conversion circuit, the polarity of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike is opposite to the polarity of the input end, and the voltage direction of the voltage after the lightning strike voltage is superimposed with the voltage across the output capacitor is opposite to the conduction direction of the bypass diode. The absorption circuit is connected in parallel with the input capacitor and is used to absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike.

[0022] Since the absorption circuit can absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike, the rising rate of the lightning strike voltage (i.e., negative voltage) across the input capacitor can be effectively slowed down, and the rising amplitude of the negative voltage can be reduced. Correspondingly, after the negative voltage of the input capacitor is superimposed with the positive voltage of the output capacitor, it will not cause the bypass diode to be damaged due to reverse voltage overvoltage, ensuring the safety and stability of the photovoltaic inverter during operation.

[0023] Optionally, the absorption circuit includes a series-connected absorption capacitor and a third diode. Among them, the third diode is reversely connected between the positive and negative poles of the input end of the DC / DC conversion circuit, and the absorption capacitor can be a capacitor in the uF range. For example, the capacitance value of the absorption capacitor can be greater than or equal to 100 uF.

[0024] When the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the third diode can conduct, enabling the absorption capacitor to be connected in parallel with the input capacitor. After the absorption capacitor and the input capacitor are connected in parallel, it can not only effectively slow down the rising speed of the reverse voltage across the bypass diode, but also effectively reduce the rising amplitude of this reverse voltage, thereby achieving effective protection for the bypass diode. When the DC / DC conversion circuit is operating normally, since the third diode is in a reverse cut-off state, it is possible to prevent the absorption capacitor from affecting the total capacitance of the input capacitor of the DC / DC conversion circuit, and further avoid affecting the normal operation of the DC / DC conversion circuit.

[0025] In a third aspect, a photovoltaic power generation system is provided. The photovoltaic power generation system includes: a plurality of photovoltaic inverters provided as in the first aspect or the second aspect above. The input ends of the DC / DC conversion circuits in the plurality of photovoltaic inverters are used to connect to photovoltaic panels, the AC ends of the DC / AC conversion circuits in the plurality of photovoltaic inverters are connected in parallel, and the parallel AC ends are used to connect to the power grid through a transformer.

[0026] In summary, the present application provides a photovoltaic inverter. The photovoltaic inverter provided by the present application includes a DC / DC conversion circuit and a first absorption circuit. Among them, the DC / DC conversion circuit includes a bypass diode connected between the positive pole of the input end and the positive pole of the output end, and the first absorption circuit is connected in parallel with the bypass diode. When the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the voltage direction of the voltage after the lightning strike voltage is superimposed on the voltage across the output capacitor is opposite to the conduction direction of the bypass diode. That is, this negative differential-mode lightning strike will generate a reverse voltage across the bypass diode. Since the first absorption circuit can effectively absorb the energy of this reverse voltage, it can prevent the bypass diode from being damaged due to overvoltage of the reverse voltage, ensuring the safety and stability of the photovoltaic inverter during operation. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of a photovoltaic power generation system provided by an embodiment of the present application;

[0028] Figure 2 is a schematic structural diagram of a photovoltaic inverter provided by an embodiment of the present application;

[0029] Figure 3 is a schematic diagram of the input end of a photovoltaic inverter provided by an embodiment of the present application being subjected to a negative differential-mode lightning strike;

[0030] Figure 4 is a schematic structural diagram of another photovoltaic inverter provided by an embodiment of the present application;

[0031] Figure 5 is a schematic structural diagram of yet another photovoltaic inverter provided by an embodiment of the present application;

[0032] Figure 6 is a schematic structural diagram of another photovoltaic inverter provided by an embodiment of the present application;

[0033] Figure 7 is a schematic structural diagram of another photovoltaic inverter provided by an embodiment of the present application;

[0034] Figure 8 is a schematic structural diagram of another photovoltaic inverter provided by an embodiment of the present application;

[0035] Figure 9 is a schematic structural diagram of another photovoltaic inverter provided by an embodiment of the present application. Detailed implementation manners

[0036] The following will introduce in detail the photovoltaic inverter provided by the embodiment of the present application with reference to the accompanying drawings. First, the key terms related to the embodiment of the present application will be introduced.

[0037] Photovoltaic (PV) panel: Also known as a photovoltaic module, it is a device used to convert solar energy into direct current electrical energy.

[0038] Three-level boost circuit: A boost circuit that can generate three levels. Common topologies include: diode-clamped type, flying-capacitor type, or symmetric boost type. In the embodiment of the present application, the flying-capacitor type three-level boost circuit is taken as an example for illustration.

[0039] Differential-mode lightning strike: It refers to the lightning strike voltage (also known as surge voltage) generated by a lightning strike that appears in the circuit in the form of a differential-mode signal. For example, the surge voltage generated by a lightning strike is applied between the positive and negative poles of the input end of the three-level boost circuit.

[0040] Positive differential-mode lightning strike: The polarity of the lightning strike voltage generated by a lightning strike is the same as the polarity of the input end of the three-level boost circuit.

[0041] Negative differential-mode lightning strike: The polarity of the lightning strike voltage generated by a lightning strike is opposite to the polarity of the input end of the three-level boost circuit.

[0042] Transient overvoltage: It refers to an abnormal phenomenon in the power system where the voltage appears much higher than the normal working voltage in a short time due to various reasons (such as lightning strikes).

[0043] Figure 1 is a schematic structural diagram of a photovoltaic power generation system provided by an embodiment of the present application. As Figure 1As shown, the photovoltaic power generation system may include at least one (i.e., one or more) photovoltaic inverters. The DC side of each photovoltaic inverter is used to connect to a photovoltaic panel, and the AC side may be connected to one end of a transformer. For example, referring to Figure 1 , the AC sides of multiple photovoltaic inverters may be connected in parallel to an AC bus, and the AC bus is connected to one end of the transformer. The other end of the transformer is used to connect to the power grid. Among them, each photovoltaic inverter can be used to convert the direct current (DC) of the photovoltaic panel into alternating current (AC) and then transmit it to the transformer. The transformer is used to boost the alternating current output by the multiple photovoltaic inverters and then output it to the power grid. It can be understood that the above photovoltaic inverter can be referred to as an inverter or a photovoltaic inverter. And, Figure 1 The architecture of the photovoltaic power generation system shown is only a schematic, and the photovoltaic power generation system may also adopt other architectures, which are not limited in the embodiments of the present application.

[0044] Figure 2 FIG. is a schematic structural diagram of a photovoltaic inverter provided by an embodiment of the present application. As Figure 2 shown, the photovoltaic inverter may include two cascaded power conversion circuits. Among them, the front-stage power conversion circuit is a DC / DC conversion circuit 10, and the rear-stage power conversion circuit is a DC / AC conversion circuit 20. The input end of the DC / DC conversion circuit 10 is used to connect to a photovoltaic panel, and the output end is connected to the DC side of the DC / AC conversion circuit 20. The DC / DC conversion circuit 10 can be used to perform voltage conversion on the direct current provided by the photovoltaic panel and then output it to the subsequent DC / AC conversion circuit 20. For example, the DC / DC conversion circuit 10 may be a boost circuit, which can boost the direct current provided by the photovoltaic panel and then output it to the DC / AC conversion circuit 20. The AC side of the DC / AC conversion circuit 20 is used to connect to the power grid. For example, the AC side is connected to the power grid through a transformer. The DC / AC conversion circuit 20 is used to convert the direct current output by the DC / DC conversion circuit 10 into alternating current and then output it to the power grid.

[0045] Optionally, referring to Figure 2 , the photovoltaic inverter may include multiple DC / DC conversion circuits 10, and the DC sides of the multiple DC / DC conversion circuits 10 are connected in parallel to a DC bus. The DC bus is connected to the DC side of the DC / AC conversion circuit 20.

[0046] In the embodiments of the present application, the above DC / DC conversion circuit 10 may be a three-level boost circuit. As Figure 3As shown, the three-level boost circuit includes: an input capacitor Cin, an inductor L, a first diode D1, a second diode D2, a first switching transistor T1, a second switching transistor T2, a flying capacitor Cfly, and output capacitors Cout1 and Cout2. Among them, the input capacitor Cin is connected between the positive and negative poles of the input terminal of the DC / DC conversion circuit 10. Since the input terminal of the DC / DC conversion circuit 10 is used to connect to a photovoltaic panel, this input capacitor Cin is also called the PV input capacitor. The output capacitors Cout1 and Cout2 are connected in series between the positive and negative poles of the output terminal of the DC / DC conversion circuit 10. The first diode D1, the second diode D2, the first switching transistor T1, and the second switching transistor T2 are sequentially connected in series between the positive and negative poles of the output terminal of the DC / DC conversion circuit 10. One end of the inductor L is connected to the positive pole of the input terminal of the DC / DC conversion circuit 10, and the other end is connected to the series node between the second diode D2 and the first switching transistor T1. One end of the flying capacitor Cfly is connected to the series node between the first diode D1 and the second diode D2, and the other end is connected to the series node between the first switching transistor T1 and the second switching transistor T2.

[0047] Since the photovoltaic panel connected to the input terminal of the DC / DC conversion circuit 10 is installed outdoors, the input terminal of the DC / DC conversion circuit 10 may be struck by lightning. To cope with positive differential-mode lightning strikes, as Figure 3 shown, the three-level boost circuit further includes bypass diodes D3 and D4. The bypass diodes D3 and D4 are connected between the positive pole of the input terminal and the positive pole of the output terminal of the DC / DC conversion circuit 10. That is to say, the bypass diodes D3 and D4 are connected in parallel across the inductor L1, the first diode D1, and the second diode D2. When the input terminal of the three-level boost circuit is struck by a positive differential-mode lightning strike, the bypass diodes D3 and D4 can conduct to discharge the lightning energy, thereby protecting the inductor L1, the first diode D1, and the second diode D2.

[0048] Optionally, continuing to refer to Figure 3 , the three-level boost circuit may further include a diode D5. One end of the diode D5 is connected to the series node between the first switching transistor T1 and the second switching transistor T2, and the other end is connected to the series node between the output capacitors Cout1 and Cout2.

[0049] In the above three-level boost circuit with bypass diodes, when the input terminal is struck by a negative differential-mode lightning strike, the negative differential-mode lightning strike will turn the input capacitor Cin into a negative voltage, that is, the negative differential-mode lightning strike will cause the voltage polarity of the input capacitor Cin to be opposite to the original polarity. As Figure 3As shown by the dashed arrow in the figure, the negative voltage of the input capacitor Cin will be superimposed on the positive voltage of the output capacitor Cout, which will further cause the reverse voltage across the bypass diodes (D3 and D4) to exceed the rated voltage, resulting in device damage and affecting the stability and safety of the PV inverter. Herein, the reverse voltage across the bypass diodes refers to the voltage that makes the bypass diodes in the reverse bias state.

[0050] Embodiments of the present application provide a PV inverter, which can be applied to a PV power generation system such as Figure 1 shown in the figure. Moreover, the PV inverter can effectively avoid the damage of the bypass diodes due to overvoltage of the reverse voltage when the input end suffers from negative differential mode lightning strikes. As Figure 4 shown in the figure, the PV inverter includes: a DC / DC conversion circuit 10 and a first absorption circuit 30. The input end of the DC / DC conversion circuit 10 is used to connect to a PV panel, the output end of the DC / DC conversion circuit 10 is used to connect to a DC bus, and the DC / DC conversion circuit 10 is used to convert the DC power provided by the PV panel and then output it to the DC bus.

[0051] Continuing to refer to Figure 4 , the DC / DC conversion circuit 10 can be a three-level boost circuit, and the DC / DC conversion circuit 10 includes: an input capacitor Cin, a first diode D1, a second diode D2, a first switch tube T1, a second switch tube T2, an inductor L1, a flying capacitor Cfly, an output capacitor Cout, and a bypass diode D3. Among them, the input capacitor Cin is connected between the positive and negative poles of the input end. The first diode D1, the second diode D2, the first switch tube T1, and the second switch tube T2 are sequentially connected in series between the positive and negative poles of the output end. One end of the inductor L1 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, and the other end of the inductor L1 is connected to the series node between the second diode D2 and the first switch tube T1. One end of the flying capacitor Cfly is connected to the series node between the first diode D1 and the second diode D2, and the other end of the flying capacitor Cfly is connected to the series node between the first switch tube T1 and the second switch tube T2. The output capacitor Cout is connected between the positive and negative poles of the output end. The bypass diode D3 is connected between the positive pole of the input end and the positive pole of the output end. That is to say, the bypass diode D3 is connected in parallel across the inductor L1, the second diode D2, and the first diode D1. Moreover, as can be seen from FIG. 4, the positive pole of the bypass diode D3 is connected to the positive pole of the input end, and the negative pole of the bypass diode D3 is connected to the positive pole of the output end.

[0052] It can be understood that the DC / DC conversion circuit 10 may include one or more bypass diodes. The multiple bypass diodes can be connected in series and / or in parallel. For example, referring to Figure 4, the DC / DC conversion circuit 10 may include a bypass diode D3. Alternatively, referring to Figure 5 , the DC / DC conversion circuit 10 may include two bypass diodes D3 and D4 connected in series. Or, the DC / DC conversion circuit 10 may include a plurality of bypass diode groups connected in series, and each bypass diode group includes at least two bypass diodes connected in parallel.

[0053] When a negative differential-mode lightning strike occurs at the input end of the DC / DC conversion circuit 10, the polarity of the lightning strike voltage generated across the input capacitor Cin by the negative differential-mode lightning strike is opposite to the polarity of the input end. That is, the negative differential-mode lightning strike will cause a negative voltage across the input capacitor Cin. The direction of the voltage after the superposition of the lightning strike voltage (i.e., negative voltage) and the voltage across the output capacitor Cout (i.e., positive voltage) is opposite to the conduction direction of the bypass diode D3. Here, the voltage direction refers to the direction from the high potential to the low potential. The high potential of the above-mentioned superposed voltage is the negative electrode of the bypass diode D3, i.e., the positive electrode of the output end, and the low potential is the positive electrode of the bypass diode D3, i.e., the positive electrode of the input end. It can be seen that for the bypass diode D3, the above-mentioned superposed voltage is a reverse voltage. When this reverse voltage is applied across the bypass diode D3, it will cause the bypass diode D3 to be in a reverse-biased state. And if this reverse voltage exceeds the breakdown voltage of the bypass diode D3, it will cause the bypass diode D3 to break down in reverse.

[0054] As Figure 4 shown, the first absorption circuit 30 is connected in parallel with the bypass diode D3 and is used to absorb the energy of the reverse voltage across the bypass diode D3. It can be understood that if the first absorption circuit 30 is not provided, the above-mentioned reverse voltage will form a transient overvoltage across the bypass diode D3, and this transient overvoltage can also be called a spike voltage. Correspondingly, the function of the first absorption circuit 30 can also be understood as being used to suppress (or absorb) the energy of the transient overvoltage across the bypass diode D3. Thus, the reverse voltage across the bypass diode D3 can be limited within a safe range to prevent the bypass diode D3 from being damaged due to overvoltage of the reverse voltage. In addition, the function of the first absorption circuit 30 can also be understood as being used to absorb lightning strike energy, or absorb the surge energy generated by the lightning strike. Or it can also be understood that: the current generated by the negative differential-mode lightning strike can pass through the first absorption circuit 30, but will not pass through the reverse-biased bypass diode D3, thereby realizing the protection of the bypass diode D3.

[0055] Optionally, continuing to refer to Figure 4, the DC / DC conversion circuit 10 may include two output capacitors Cout1 and Cout2. The two output capacitors Cout1 and Cout2 are connected in series between the positive and negative poles of the output terminal of the DC / DC conversion circuit 10. And, the DC / DC conversion circuit 10 may further include a diode D5, one end of the diode D5 is connected to the series node between the first switching transistor T1 and the second switching transistor T2, and the other end is connected to the series node between the output capacitors Cout1 and Cout2.

[0056] As a first alternative implementation, as Figure 4 shown, the first absorption circuit 30 includes: a first absorption capacitor C1 connected in parallel with the bypass diode D3. It can be understood that the first absorption capacitor C1 may include one or more capacitors. If the first absorption capacitor C1 includes multiple capacitors, the multiple capacitors may be connected in series and / or in parallel.

[0057] In this implementation, when a reverse voltage is generated across the bypass diode D3 due to a negative differential-mode lightning strike, the first absorption capacitor C1 can quickly charge, thereby storing the lightning energy in the form of electric field energy. Thus, it is possible to suppress the rapid rise of the reverse voltage across the bypass diode D3 and keep the reverse voltage across the bypass diode D3 within a relatively stable range to effectively protect the bypass diode D3.

[0058] As a second alternative implementation, the first absorption circuit 30 may be an RC absorption circuit composed of a resistor R and a capacitor C. By way of example, referring to Figure 5 , the first absorption circuit 30 may include a series-connected first absorption capacitor C1 and a resistor R1.

[0059] In this implementation, when a reverse voltage is generated across the bypass diode D3 due to a negative differential-mode lightning strike, the first absorption capacitor C1 can suppress the rapid rise of the reverse voltage across the bypass diode D3 by charging. The resistor R1 is also called a current-limiting resistor, which can limit the charging current of the first absorption capacitor C1 and prevent other components in the circuit from being damaged due to excessive charging current.

[0060] Optionally, in the above two implementations, the first absorption capacitor C1 may be a capacitor in the uF range. For example, the capacitance value of the first absorption capacitor C1 may be greater than or equal to 150 uF. By using a capacitor in the uF range, it can be ensured that when a reverse voltage is generated across the bypass diode D3, the first absorption capacitor C1 can quickly charge, thereby effectively suppressing the rising speed and amplitude of the reverse voltage. The above resistor R1 may be an independent resistor element, or may also be the line resistance in the first absorption circuit 30.

[0061] As a third alternative implementation, the first absorption circuit 30 includes: a TVS diode or an SPD. Among them, the TVS diode is also called a transient voltage suppressor.

[0062] For example, Figure 6 As shown, taking the first absorption circuit 30 including a TVS diode as an example, the positive electrode (i.e., the anode) of the TVS diode can be connected to the positive electrode of the input end of the DC / DC conversion circuit 10, and the negative electrode (i.e., the cathode) can be connected to the positive electrode of the output end of the DC / DC conversion circuit 10. That is, the TVS diode is connected in parallel with the bypass diode D3 in the forward direction. Based on this, when a reverse voltage is generated across the bypass diode D3 due to a negative differential-mode lightning strike, if the reverse voltage across the bypass diode D3 exceeds the breakdown voltage of the TVS diode, the TVS diode conducts and clamps the voltage, thereby preventing the bypass diode D3 from being reversely broken down.

[0063] For the scenario where the first absorption circuit 30 is implemented by an SPD, the SPD can discharge or limit the energy of the reverse voltage when a reverse voltage is generated across the bypass diode D3 due to the energy of a negative differential-mode lightning strike, so it can effectively prevent the bypass diode D3 from being damaged by reverse overvoltage.

[0064] It can be understood that the breakdown voltages of the above TVS and SPD can be slightly lower than the withstand voltage value of the bypass diode D3. The withstand voltage value of the bypass diode D3 refers to the maximum voltage that the bypass diode D3 can withstand in the reverse-biased state. Thus, not only can effective protection of the bypass diode D3 be achieved, but also misoperation of the TVS and SPD can be avoided. For example, the breakdown voltages of the TVS and SPD can be less than or equal to 3000 volts (V).

[0065] It can also be understood that the several implementation manners of the first absorption circuit 30 above are only illustrative, and the first absorption circuit 30 can also be implemented by using other passive devices or combinations of passive devices that can suppress transient overvoltage, and the embodiments of the present application do not limit this.

[0066] Optionally, as Figure 7 shown, the photovoltaic inverter 10 further includes: a second absorption circuit 40, which is connected in parallel with the input capacitor Cin and is used to absorb the energy of the lightning strike voltage generated across the input capacitor Cin by the negative differential-mode lightning strike.

[0067] It can be understood that, as described above, when the input end of the DC / DC conversion circuit 10 is subjected to a negative differential-mode lightning strike, the lightning energy will generate a lightning voltage across the input capacitor Cin, and the polarity of this lightning voltage is opposite to that of the input end, that is, this lightning voltage is a negative voltage. In the embodiment of the present application, since the photovoltaic inverter 10 includes a second absorption circuit 40 connected in parallel with the input capacitor Cin, and this second absorption circuit 40 can absorb the energy of the lightning voltage across the input capacitor Cin, it is possible to effectively slow down the rising rate of the negative voltage across the input capacitor Cin and reduce the rising amplitude of this negative voltage. Correspondingly, after the negative voltage of the input capacitor Cin is superimposed with the positive voltage of the output capacitor Cout, it will not cause the bypass diode D3 to be damaged due to reverse voltage overvoltage.

[0068] Optionally, continue to refer to Figure 7 , the second absorption circuit 40 includes: a second absorption capacitor C2 and a third diode D6 connected in series. Among them, the third diode D6 is reversely connected between the positive and negative poles of the input end of the DC / DC conversion circuit 10.

[0069] Exemplarily, as Figure 7 shown, one end of the second absorption capacitor C2 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, the other end of the second absorption capacitor C2 is connected to the negative pole of the third diode D6, and the positive pole of the third diode D6 is connected to the negative pole of the input end of the DC / DC conversion circuit 10. Alternatively, the negative pole of the third diode D6 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, the positive pole of the third diode D6 is connected to one end of the second absorption capacitor C2, and the other end of the second absorption capacitor C2 is connected to the negative pole of the input end of the DC / DC conversion circuit 10.

[0070] It can be understood that when the input end of the DC / DC conversion circuit 10 is subjected to a negative differential-mode lightning strike, the third diode D6 can conduct, so that the second absorption capacitor C2 is connected in parallel with the input capacitor Cin. At this time, the lightning energy generated by the negative differential-mode lightning strike can charge both the second absorption capacitor C2 and the input capacitor Cin at the same time. Compared with only charging the input capacitor Cin, when the second absorption capacitor C2 and the input capacitor Cin are charged in parallel, it can effectively slow down the rising speed of the reverse voltage at the input end of the DC / DC conversion circuit 10, and further slow down the rising speed of the reverse voltage across the bypass diode D3. And, since the second absorption capacitor C2 and the input capacitor Cin are connected in parallel, it is equivalent to increasing the total capacitance of the input capacitor, so it can also effectively reduce the rising amplitude of the reverse voltage across the bypass diode D3. Based on the above analysis, it can be known that after the third diode D6 can conduct, it can reduce the rising speed and amplitude of the reverse voltage across the bypass diode D3, thus effectively avoiding the bypass diode D3 from being damaged due to reverse overvoltage and playing a protective role for the bypass diode D3.

[0071] It can also be understood that when the DC / DC conversion circuit 10 is operating normally, the third diode D6 is in a reverse cut-off state. At this time, the second absorption capacitor C2 will not be connected in series with the input capacitor Cin, that is, it will not affect the total capacitance of the input capacitor of the DC / DC conversion circuit 10. Thus, the normal operation of the DC / DC conversion circuit 10 can be avoided from being affected.

[0072] Optionally, the above-mentioned second absorption capacitor C2 can be a capacitor in the uF range. For example, the capacitance value of the second absorption capacitor C2 can be greater than or equal to 100 uF. By using the capacitor in the uF range, it can be ensured that when the input end of the DC / DC conversion circuit 10 is subjected to a negative differential-mode lightning strike, the second absorption capacitor C2 and the input capacitor Cin connected in parallel can be quickly charged, thereby effectively suppressing the rising speed and rising amplitude of the negative voltage across the input capacitor Cin.

[0073] It can also be understood that the implementation manner of the above-mentioned second absorption circuit 40 is only illustrative, and the second absorption circuit 40 can also be implemented by using other passive devices or combinations of passive devices that can suppress transient overvoltage. For example, the second absorption circuit 40 can also include a resistor connected in series with the second absorption capacitor C2 and the third diode D6, and this resistor can be used to limit the charging current of the second absorption capacitor C2. The embodiments of the present application do not limit the implementation manner of this second absorption circuit.

[0074] Optionally, as Figure 2 shown, the photovoltaic inverter provided by the embodiments of the present application may include a plurality of DC / DC conversion circuits 10. Moreover, this photovoltaic inverter further includes: a DC / AC conversion circuit 20. The output ends of the plurality of DC / DC conversion circuits 10 are connected in parallel to the DC bus, the DC bus is connected to the DC end of the DC / AC conversion circuit 20, and the AC end of the DC / AC conversion circuit 20 is used to connect to the power grid. The DC / AC conversion circuit 20 is used to convert the direct current output by the DC / DC conversion circuit 10 into alternating current and then output it to the power grid.

[0075] Based on Figure 2 the structure shown, the photovoltaic inverter provided by the embodiments of the present application is a two-stage photovoltaic inverter, and this two-stage photovoltaic inverter includes two cascaded power conversion circuits. Among them, the front-stage power conversion circuit is the DC / DC conversion circuit 10, and the rear-stage power conversion circuit is the DC / AC conversion circuit 20.

[0076] Optionally, as Figure 8As shown in the figure, the photovoltaic inverter provided by the embodiment of the present application further includes a lightning protection circuit 50 connected to the input end of the DC / DC conversion circuit 10. The lightning protection circuit 50 can be used to absorb (also known as discharge) lightning strike energy, so as to prevent the subsequent system (i.e., the subsequent DC / AC conversion circuit 20) from being subjected to a large impact current. That is to say, the lightning protection circuit 50 can bypass part of the impact current for the subsequent system.

[0077] Exemplarily, referring to Figure 8 , the lightning protection circuit 50 can be a Y-shaped lightning protection circuit composed of SPDs. The Y-shaped lightning protection circuit includes SPD1, SPD2, and SPD3. Among them, one end of SPD1 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, and one end of SPD2 is connected to the negative pole of the input end of the DC / DC conversion circuit 10. The other ends of SPD1 and SPD2 are both connected to one end of SPD3, and the other end of SPD3 is grounded. When the input end of the DC / DC conversion circuit 10 is subjected to differential mode lightning strikes (including positive and negative), SPD1 and SPD2 will be broken down, and the lightning strike energy will be bypassed outside the subsequent circuit. When the input end of the DC / DC conversion circuit 10 is subjected to common mode lightning strikes, and the common mode lightning strikes are applied between the positive pole of the input end of the DC / DC conversion circuit 10 and the ground terminal, SPD1 and SPD3 can conduct the positive pole of the input end of the DC / DC conversion circuit 10 and the ground terminal to discharge the lightning strike energy. When the input end of the DC / DC conversion circuit 10 is subjected to common mode lightning strikes, and the common mode lightning strikes are applied between the negative pole of the input end of the DC / DC conversion circuit 10 and the ground terminal, SPD2 and SPD3 can conduct the negative pole of the input end of the DC / DC conversion circuit 10 and the ground terminal to discharge the lightning strike energy.

[0078] Optionally, as Figures 6 to 8 shown, the DC bus connected to the output end of the DC / DC conversion circuit 10 includes a positive bus BUS+ and a negative bus BUS-. A bus capacitor is also connected between the positive bus BUS+ and the negative bus BUS-, for example, two bus capacitors C3 and C4 are connected in series. And, a filter inductor L2 is also connected in series between the positive pole of the output end of the DC / DC conversion circuit 10 and the positive bus BUS+, and a filter inductor L3 is also connected in series between the negative pole of the output end of the DC / DC conversion circuit 10 and the negative bus BUS-. The output capacitor Cout (or Cout1 and Cout2) in the DC / DC conversion circuit 10 can also be referred to as a bus capacitor.

[0079] In summary, the embodiment of the present application provides a photovoltaic inverter. The photovoltaic inverter includes a DC / DC conversion circuit and a first absorption circuit. Among them, the DC / DC conversion circuit includes a bypass diode connected between the positive electrode of the input end and the positive electrode of the output end, and the first absorption circuit is connected in parallel with the bypass diode. When the input end of the DC / DC conversion circuit is subjected to a negative differential-mode lightning strike, the voltage direction of the voltage after the lightning strike voltage is superimposed on the voltage across the output capacitor is opposite to the conduction direction of the bypass diode. That is, the negative differential-mode lightning strike will generate a reverse voltage across the bypass diode. Since the first absorption circuit can effectively absorb the energy of the reverse voltage, it can avoid the damage of the bypass diode due to overvoltage of the reverse voltage, ensuring the safety and stability of the photovoltaic inverter during operation. Moreover, the above-mentioned first absorption circuit can be implemented by passive devices, and its structure is relatively simple, which can avoid increasing the cost and structural complexity of the photovoltaic inverter.

[0080] The embodiment of the present application also provides another photovoltaic inverter, which can be applied to a photovoltaic power generation system such as Figure 1 shown. And, when the input end of the photovoltaic inverter is subjected to a negative differential-mode lightning strike, it can effectively avoid the damage of the bypass diode due to overvoltage of the reverse voltage. As Figure 9 shown, the photovoltaic inverter includes: a DC / DC conversion circuit 10 and an absorption circuit 40. The input end of the DC / DC conversion circuit 10 is used to connect to a photovoltaic panel, the output end of the DC / DC conversion circuit 10 is used to connect to a DC bus, and the DC / DC conversion circuit 10 is used to convert the DC power provided by the photovoltaic panel and output it to the DC bus.

[0081] Refer to Figure 9, the DC / DC conversion circuit 10 can be a three-level boost circuit, and the DC / DC conversion circuit 10 includes: an input capacitor Cin, a first diode D1, a second diode D2, a first switching transistor T1, a second switching transistor T2, an inductor L1, a flying capacitor Cfly, an output capacitor Cout, and a bypass diode D3. Among them, the input capacitor Cin is connected between the positive and negative terminals of the input end. The first diode D1, the second diode D2, the first switching transistor T1, and the second switching transistor T2 are connected in series between the positive and negative terminals of the output end. One end of the inductor L1 is connected to the positive terminal of the input end of the DC / DC conversion circuit 10, and the other end of the inductor L1 is connected to the series node between the second diode D2 and the first switching transistor T1. One end of the flying capacitor Cfly is connected to the series node between the first diode D1 and the second diode D2, and the other end is connected to the series node between the first switching transistor T1 and the second switching transistor T2. The output capacitor Cout is connected between the positive and negative terminals of the output end. The bypass diode D3 is connected between the positive terminal of the input end and the positive terminal of the output end. That is to say, the bypass diode D3 is connected in parallel across the inductor L1, the second diode D2, and the first diode D1. And, as can be seen from 4, the positive terminal of the bypass diode D3 is connected to the positive terminal of the input end, and the negative terminal of the bypass diode D3 is connected to the positive terminal of the output end.

[0082] When a negative differential-mode lightning strike occurs at the input end of the DC / DC conversion circuit 10, the polarity of the lightning strike voltage generated across the input capacitor Cin by the negative differential-mode lightning strike is opposite to the polarity of the input end. That is to say, the negative differential-mode lightning strike will cause a negative voltage across the input capacitor Cin. The direction of the voltage after the superposition of this lightning strike voltage (i.e., negative voltage) and the voltage across the output capacitor Cout (i.e., positive voltage) is opposite to the conduction direction of the bypass diode D3. Among them, the voltage direction refers to the direction from a high potential to a low potential. The high potential of the voltage after the above superposition is the negative terminal of the bypass diode D3, that is, the positive terminal of the output end, and the low potential is the positive terminal of the bypass diode D3, that is, the positive terminal of the input end. It can be seen that for the bypass diode D3, the voltage after the above superposition is a reverse voltage. This reverse voltage is applied across the bypass diode D3, which will cause the bypass diode D3 to be in a reverse-biased state. And, if this reverse voltage exceeds the breakdown voltage of the bypass diode D3, it will cause the bypass diode D3 to break down in the reverse direction.

[0083] Continue to refer to Figure 9 , the absorption circuit 40 is connected in parallel with the input capacitor Cin and is used to absorb the energy of the lightning strike voltage generated across the input capacitor Cin by the negative differential-mode lightning strike. Thus, the rising rate of the lightning strike voltage (i.e., negative voltage) across the input capacitor Cin can be effectively slowed down, and the rising amplitude of this negative voltage can be reduced. Correspondingly, after the negative voltage of the input capacitor Cin is superposed with the positive voltage of the output capacitor Cout, it will not cause the bypass diode D3 to be damaged due to overvoltage of the reverse voltage.

[0084] Optionally, continuing to refer to Figure 9 , the absorption circuit 40 includes: an absorption capacitor C2 and a third diode D6 connected in series. Among them, the third diode D6 is reversely connected between the positive and negative poles of the input end of the DC / DC conversion circuit 10.

[0085] Exemplarily, as Figure 9 shown, one end of the absorption capacitor C2 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, the other end of the absorption capacitor C2 is connected to the negative pole of the third diode D6, and the positive pole of the third diode D6 is connected to the negative pole of the input end of the DC / DC conversion circuit 10. Alternatively, the negative pole of the third diode D6 is connected to the positive pole of the input end of the DC / DC conversion circuit 10, the positive pole of the third diode D6 is connected to one end of the absorption capacitor C2, and the other end of the absorption capacitor C2 is connected to the negative pole of the input end of the DC / DC conversion circuit 10.

[0086] As described above, when the input end of the DC / DC conversion circuit 10 is subjected to a negative differential-mode lightning strike, the third diode D6 can conduct, so that the absorption capacitor C2 is connected in parallel with the input capacitor Cin. At this time, the lightning energy generated by the negative differential-mode lightning strike can charge both the absorption capacitor C2 and the input capacitor Cin. Thus, the rising speed and amplitude of the reverse voltage across the bypass diode D3 can be effectively slowed down, thereby effectively avoiding damage to the bypass diode D3 due to reverse overvoltage, and playing a protective role for the bypass diode D3.

[0087] Moreover, when the DC / DC conversion circuit 10 is operating normally, since the third diode D6 is in a reverse cut-off state, the absorption capacitor C2 will not be connected in series with the input capacitor Cin, thereby avoiding affecting the normal operation of the DC / DC conversion circuit 10.

[0088] Optionally, the above absorption capacitor C2 can be a capacitor in the uF range. For example, the capacitance value of the absorption capacitor C2 can be greater than or equal to 100 uF. By using the capacitor in the uF range, it can be ensured that when the input end of the DC / DC conversion circuit 10 is subjected to a negative differential-mode lightning strike, the parallel-connected absorption capacitor C2 and input capacitor Cin can be quickly charged, thereby effectively suppressing the rising speed and rising amplitude of the negative voltage across the input capacitor Cin.

[0089] It can be understood that Figure 9 the structure and function of the photovoltaic inverter provided by the embodiment shown can also refer to the relevant descriptions of the foregoing embodiments (such as Figures 4 to 8 the embodiment shown), which will not be elaborated here.

[0090] The embodiment of the present application also provides a photovoltaic power generation system. Refer to Figure 1, the photovoltaic power generation system includes a plurality of photovoltaic inverters provided in the above embodiments. The input ends of the DC / DC conversion circuits in the plurality of photovoltaic inverters are used to connect to photovoltaic panels, and the AC ends of the DC / AC conversion circuits in the plurality of photovoltaic inverters can be connected in parallel to one end of a transformer, and the other end of the transformer is connected to the power grid.

[0091] It can be understood that the photovoltaic power generation system has substantially the same technical effects as the photovoltaic inverter provided in the foregoing embodiments. Therefore, for the sake of simplicity, the technical effects of the photovoltaic power generation system will not be repeated here.

[0092] In the embodiments of the present application, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. The term "at least one" means one or more, and "a plurality" means two or more.

[0093] In the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the front and rear associated objects.

[0094] As described above, the above are only alternative embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A photovoltaic inverter, characterized in that, The photovoltaic inverter includes: a DC / DC conversion circuit and a first absorption circuit. The input end of the DC / DC conversion circuit is used to connect to a photovoltaic panel, and the output end is used to connect to a DC bus. The DC / DC conversion circuit is used to convert the DC power provided by the photovoltaic panel and then output it. The DC / DC conversion circuit includes: an input capacitor, a first diode, a second diode, a first switch tube, a second switch tube, an inductor, a flying capacitor, an output capacitor, and a bypass diode; Wherein, the input capacitor is connected between the positive and negative poles of the input end; the first diode, the second diode, the first switch tube, and the second switch tube are connected in series between the positive and negative poles of the output end; one end of the inductor is connected to the positive pole of the input end, and the other end of the inductor is connected to the series node between the second diode and the first switch tube; one end of the flying capacitor is connected to the series node between the first diode and the second diode, and the other end of the flying capacitor is connected to the series node between the first switch tube and the second switch tube; the output capacitor is connected between the positive and negative poles of the output end; the bypass diode is connected between the positive pole of the input end and the positive pole of the output end; When a negative differential-mode lightning strike occurs at the input end, the polarity of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike is opposite to the polarity of the input end. The voltage direction of the voltage after the lightning strike voltage is superimposed on the voltage across the output capacitor is opposite to the conduction direction of the bypass diode; The first absorption circuit is connected in parallel with the bypass diode and is used to absorb the energy of the superimposed voltage across the bypass diode.

2. The photovoltaic inverter according to claim 1, characterized in that, The first absorption circuit includes a first absorption capacitor, and the capacitance value of the first absorption capacitor is greater than or equal to 150 microfarads.

3. The photovoltaic inverter according to claim 1, characterized in that, The first absorption circuit includes a first absorption capacitor and a resistor connected in series, and the capacitance value of the first absorption capacitor is greater than or equal to 150 microfarads.

4. The photovoltaic inverter according to claim 1, characterized in that, The first absorption circuit includes: a transient voltage suppression diode TVS or a surge protector SPD.

5. The photovoltaic inverter according to any one of claims 1 to 4, characterized in that, The photovoltaic inverter further includes: a second absorption circuit. The second absorption circuit is connected in parallel with the input capacitor and is used to absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike.

6. The photovoltaic inverter according to claim 5, wherein, The second absorption circuit includes: a second absorption capacitor and a third diode connected in series; wherein, the third diode is reversely connected between the positive and negative poles of the input end, and the capacitance value of the second absorption capacitor is greater than or equal to 100 microfarads.

7. A photovoltaic inverter, characterized in that, The photovoltaic inverter includes: a DC / DC conversion circuit and an absorption circuit. The input end of the DC / DC conversion circuit is used to connect to a photovoltaic panel, and the output end is used to connect to a DC bus. The DC / DC conversion circuit is used to convert the DC power provided by the photovoltaic panel and then output it to the DC bus. The DC / DC conversion circuit includes: an input capacitor, an output capacitor, a first diode, a second diode, a first switch tube, a second switch tube, an inductor, and a bypass diode; Wherein, the input capacitor is connected between the positive and negative poles of the input terminal; the output capacitor is connected between the positive and negative poles of the output terminal; the first diode, the second diode, the first switching transistor and the second switching transistor are connected in series between the positive and negative poles of the output terminal; one end of the inductor is connected to the positive pole of the input terminal, and the other end of the inductor is connected to the series node between the second diode and the first switching transistor; the bypass diode is connected between the positive pole of the input terminal and the positive pole of the output terminal; When a negative differential-mode lightning strike occurs at the input terminal, the polarity of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike is opposite to the polarity of the input terminal, and the voltage direction of the voltage after the lightning strike voltage is superimposed with the voltage across the output capacitor is opposite to the conduction direction of the bypass diode; The absorption circuit is connected in parallel with the input capacitor and is used to absorb the energy of the lightning strike voltage generated across the input capacitor by the negative differential-mode lightning strike.

8. The photovoltaic inverter according to claim 7, wherein, The absorption circuit includes: an absorption capacitor and a third diode connected in series; wherein, the third diode is reversely connected between the positive and negative poles of the input terminal, and the capacitance value of the absorption capacitor is greater than or equal to 100 microfarads.

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