A two-stage inverter and photovoltaic system for photovoltaic power generation

Abstract

This invention relates to the field of photovoltaic power generation technology, and discloses a two-stage inverter and photovoltaic system for photovoltaic power generation. The two-stage inverter includes an input inductor branch, a switching transistor branch, a diode branch, an output capacitor branch, a clamping capacitor branch, and a half-bridge inverter unit. In use, the three nodes of the two capacitors in the output capacitor branch form a three-level output structure, eliminating the need for additional windings. Furthermore, capacitor C6 can be clamped together with the capacitors and the first-end diode in the clamping capacitor branch, reducing the number of capacitors required for clamping and decreasing the voltage stress on the diode. Additionally, the input inductor branch, clamping capacitor branch, first-end diode, capacitor C6, and capacitor C7 form a zero-input current ripple structure, which can reduce the inductance, size, and cost of the inductor in the input inductor branch. Moreover, since the zero-input current ripple structure shares components with the diode branch and the clamping capacitor branch, the number of components in this invention can be reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation technology, and more specifically to a two-stage inverter and photovoltaic system for photovoltaic power generation. Background Technology

[0002] With the increasing severity of the energy crisis and environmental pollution, new energy technologies such as solar energy have become a hot topic of attention and research. The utilization of solar energy requires first converting it into electrical energy, and then connecting this electrical energy to the grid. This grid connection necessitates the use of a photovoltaic grid-connected inverter to transmit the electrical energy output from the photovoltaic system to the grid for load use. The requirement is to increase the voltage output by the photovoltaic system to the DC bus voltage.

[0003] In photovoltaic grid-connected inverters, microinverters have been widely used due to their advantages such as independent tracking, reliable performance, and convenient installation. Existing photovoltaic inverter structures employ an interleaved Flyback + full-bridge power frequency switching topology to transfer energy to the grid. However, because the Flyback topology has low gain, a full-bridge inverter is required for voltage inversion, resulting in a large number of inverter switches (a full-bridge inverter requires four switches).

[0004] Furthermore, most existing micro-inverters output two-level signals. If a three-level signal is to be output, the number of output levels can only be increased by adding windings. However, this increases the cost and size of the transformer and brings a large voltage static error. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a two-stage inverter and photovoltaic system for photovoltaic power generation, which can use a half-bridge inverter for inversion and output a three-level signal without adding windings.

[0006] To address the above technical problems, in a first aspect, the present invention provides the following technical solution: a two-stage inverter for photovoltaic power generation, comprising...

[0007] The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply.

[0008] The switching transistor branch is electrically connected to the first end of the input inductor of the input inductor branch and the tail end of the input inductor of the terminal branch. Based on the input control signal, the first end of the input inductor and the tail end of the input inductor of the input inductor branch are turned on or off.

[0009] A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor;

[0010] The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply.

[0011] The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the intermediate node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch and one end of capacitor C6, respectively. The anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. The anode of the diode electrically connected to the anode of the last diode is electrically connected to the other end of the last clamping capacitor through capacitor C1.

[0012] The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

[0013] The second invention provides a second type of two-stage inverter for photovoltaic power generation, including...

[0014] The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply.

[0015] The switching transistor branch is electrically connected to the first end of the input inductor of the input inductor branch and the tail end of the input inductor of the terminal branch. Based on the input control signal, the first end of the input inductor and the tail end of the input inductor of the input inductor branch are turned on or off.

[0016] A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor;

[0017] The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply.

[0018] The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the middle node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch. The anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor and one end of capacitor C6 through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. The anode of the diode electrically connected to the anode of the last diode is electrically connected to the other end of the last clamping capacitor through capacitor C1.

[0019] The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

[0020] Thirdly, the present invention provides a third type of two-stage inverter for photovoltaic power generation, including...

[0021] The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply.

[0022] The switching transistor branch is electrically connected to the first end of the input inductor of the input inductor branch and the tail end of the input inductor of the terminal branch. Based on the input control signal, the first end of the input inductor and the tail end of the input inductor of the input inductor branch are turned on or off.

[0023] A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor;

[0024] The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply.

[0025] The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the intermediate node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch, and the anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. One end of the anode capacitor C1 and one end of the capacitor C6 of the diode electrically connected to the anode of the last diode are electrically connected, and the other end of capacitor C1 is electrically connected to the other end of the last clamping capacitor.

[0026] The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

[0027] In one embodiment of the first to third aspects, the input inductor branch includes inductor L1 and inductor L0, inductor L0 is the end input inductor, one end of inductor L0 is used to be electrically connected to the positive terminal of an external power supply, and the other end of inductor L0 is electrically connected to one end of inductor L1 and capacitor C7 respectively, and the other end of inductor L1 is the beginning end of the beginning input inductor.

[0028] In one embodiment of the first to third aspects, the diode branch includes seven diodes connected in series, namely diode D6, diode D4, diode D5, diode D3, diode D1, diode D2 and diode D0, where diode D6 is the first diode and diode D0 is the last diode.

[0029] One end of the end clamping capacitor is electrically connected to the cathode of diode D5. The anode of diode D5 is electrically connected to the cathode of diode D3 through capacitor C3. The anode of diode D5 is electrically connected to the anode of diode D0 through capacitor C2. The anode of diode D2 is electrically connected to the other end of the end clamping capacitor through capacitor C1.

[0030] In one embodiment of the first to third aspects, the switching transistor branch includes an NMOS transistor S, the drain of the NMOS transistor S is electrically connected to the first end of the first-end input inductor, the source of the NMOS transistor S is electrically connected to the tail end of the last-end input inductor, and the gate of the NMOS transistor S is used to input the control signal.

[0031] In one embodiment of the first to third aspects, the clamping capacitor branch includes capacitor C4 and capacitor C5, wherein capacitor C4 is the first-end clamping capacitor and capacitor C5 is the last-end clamping capacitor.

[0032] In one embodiment of the first to third aspects, the first and second switching transistors are both NMOS transistors, with the drain of the NMOS transistor being the input terminal of the switching transistor and the source of the NMOS transistor being the output terminal of the switching transistor.

[0033] In one embodiment of the first to third aspects, the other end of the capacitor C0 is also electrically connected to one end of the inductor Lf.

[0034] Fourthly, the present invention provides a photovoltaic system including the aforementioned two-stage inverter for photovoltaic power generation.

[0035] The beneficial effects of this invention compared with the prior art are as follows: First, the three nodes of the two capacitors in the output capacitor branch constitute a three-level output structure, which does not require the addition of windings. In addition, capacitor C6 can be clamped together with the capacitor in the clamping capacitor branch and the first-end diode, which reduces the number of capacitors required for clamping and reduces the diode voltage stress in the diode branch.

[0036] In addition, the input inductor branch, clamping capacitor branch, first-end diode, capacitor C6, and capacitor C7 constitute a zero-input current ripple structure, which can reduce the inductance, size, and cost of the inductor in the input inductor branch. Furthermore, since the zero-input current ripple structure shares components with the diode branch and clamping capacitor branch, the number of components in this invention can be reduced.

[0037] Finally, capacitors C0, C6, C1, C2, C3, the clamping capacitor branch, and the diode branch constitute a multi-stage boost structure, which can increase the voltage conversion gain according to the duty cycle of the control signal of the switching transistor branch. After the voltage conversion gain is increased, it can be inverted through the half-bridge inverter unit. Attached Figure Description

[0038] Figure 1 This is the circuit diagram of the two-stage inverter in Example 1;

[0039] Figure 2 This is the circuit diagram of the two-stage inverter in Example 2;

[0040] Figure 3 This is the circuit diagram of the two-stage inverter in Example 3. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0042] Example 1

[0043] like Figure 1 As shown, this embodiment provides a two-stage inverter for photovoltaic power generation, including...

[0044] Input inductor branch 1 includes two input inductors connected in series, namely inductor L0 and inductor L1. Inductor L0 is the end input inductor and inductor L1 is the beginning input inductor. The end of inductor L0 is used to connect to the positive terminal of the external power supply.

[0045] The switching transistor branch 2 is electrically connected to the start end of inductor L1 and the end end of inductor L0, and turns the start end of inductor L1 and the end end of inductor L0 on or off based on the input control signal.

[0046] Diode branch 3 includes seven diodes connected in series: diode D6, diode D4, diode D5, diode D3, diode D1, diode D2, and diode D0. Diode D6 is the first diode, and diode D0 is the last diode. The anode of diode D6 is electrically connected to inductor L1.

[0047] Output capacitor branch 4 includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of diode D0, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to connect to the negative terminal of external power supply Vin.

[0048] Clamping capacitor branch 5 includes two clamping capacitors, C4 and C5, with C4 being the initial clamping capacitor and C5 the final clamping capacitor. One end of capacitor C4 is electrically connected to the cathode of diode D6, and the other end of capacitor C4 is electrically connected to the intermediate node of input inductor branch 1 via capacitor C7. One end of capacitor C5 is electrically connected to both the cathode of diode D5 and one end of capacitor C6. The anode of diode D5 is electrically connected to the other end of capacitor C5 via inductor L2. The anode of diode D5 is also electrically connected to the cathode of diode D3 via capacitor C3. The anode of diode D5 is also electrically connected to the anode of diode D0 via capacitor C2. The anode of diode D2 is electrically connected to the other end of capacitor C5 via capacitor C1.

[0049] The half-bridge inverter unit 6 includes a first switch Q1 and a second switch Q2 connected in series. The input terminal of the first switch Q1 is electrically connected to one end of the capacitor C0, and the output terminal of the second switch Q2 is electrically connected to the other end of the capacitor C6.

[0050] In this embodiment, capacitors C0-C7 have positive and negative terminals. The end of capacitor C0 connected to diode D0 is the positive terminal, and the other end is the negative terminal. The end of capacitor C1 connected to the anode of diode D1 is the positive terminal, and the other end is the negative terminal. The end of capacitor C2 connected to diode D2 is the negative terminal, and the end of capacitor C2 connected to diode D4 is the positive terminal. The end of capacitor C3 connected to the anode of diode D5 is the negative terminal, and the end of capacitor C3 connected to the cathode of diode D3 is the positive terminal. The end of capacitor C4 connected to the cathode of diode D6 is the negative terminal, and the other end is the positive terminal. The end of capacitor C5 connected to inductor L2 is the negative terminal, and the other end is the positive terminal. The end of capacitor C6 connected to the negative terminal of external power supply Vin is the negative terminal, and the other end is the positive terminal. The end of capacitor C7 connected to input inductor branch 1 is the negative terminal, and the other end is the positive terminal.

[0051] In this embodiment, the switching transistor branch 2 includes an NMOS transistor S. The drain of the NMOS transistor S is electrically connected to the first end of the inductor L1, the source of the NMOS transistor S is electrically connected to the last end of the inductor L0, and the gate of the NMOS transistor S is used to input control signals.

[0052] In this embodiment, both the first switch Q1 and the second switch Q2 are NMOS transistors, with the drain of the NMOS transistor being the input terminal and the source of the NMOS transistor being the output terminal. In actual use, the first switch Q1 and the second switch Q2 are alternately turned on and off.

[0053] In this embodiment, the other end of capacitor C0 is also electrically connected to one end of inductor Lf, which is used for filtering, and voltage Vg is the voltage for grid connection.

[0054] right Figure 1 The circuit shown is analyzed as follows:

[0055] First, diode D6, capacitor C4, capacitor C5 and capacitor C6 form a three-capacitor clamping structure. The three-capacitor clamping structure can reduce the rate of decrease of leakage inductance of inductor L0 and inductor L1. In addition, capacitor C6 and capacitor C0 form a three-level output structure. The three-level output structure and the three-capacitor level output structure share a capacitor, which can reduce the voltage stress on the diode in the circuit.

[0056] For the three-capacitor clamping structure, when the NMOS transistor S is turned on, capacitors C4 and C5, together with diodes D4 and D5, form a boost unit; when the NMOS transistor S is turned off, the leakage inductance is transferred to capacitor C6 through diode D6, capacitors C4 and C5, thereby blocking voltage and current spikes.

[0057] Secondly, the inductor L1, diode D6, capacitors C4, C5, C6, C7, and inductor L0 constitute a zero-input current ripple structure. In practical applications, the zero-input current ripple structure can reduce the inductance, size, and cost of the inductor. In addition, the zero-input current ripple structure shares diode D6, capacitors C4, C5, and C6 with the three-capacitor clamping structure, thereby reducing the number of diodes and capacitors.

[0058] For the zero-input current ripple structure, when the NMOS transistor S is turned on, the current in inductor L1 is less than the current in inductor L0 and begins to rise. The external power supply Vin, inductor L0, capacitors C5, C6 and C7 form a capacitor loop. The external power supply Vin, inductor L0, inductor L1 and NMOS transistor S form another current loop. The current fluctuations of inductor L1 and capacitor C7 are superimposed, making the current ripple flowing through inductor L0 equal to zero.

[0059] Specifically, when the current in inductor L1 rises to be greater than the current in inductor L0, inductor L1, NMOS transistor S capacitor C5, capacitor C6 and capacitor C7 form a current loop. The current fluctuations of inductor L1 and capacitor C7 are superimposed, making the current ripple flowing through inductor L0 equal to zero.

[0060] When the NMOS transistor S is turned off, the current in inductor L1 begins to decrease. Inductor L1, diode D6, capacitor C4, and capacitor C7 form a current loop. The current fluctuations of inductor L1 and capacitor C7 cancel each other out, thus eliminating the current ripple of inductor L0. When the current of inductor L1 drops to a negative value, the external power supply Vin, inductor L0, capacitor C5, capacitor C6, and then capacitor C7 form a current loop. The current fluctuations of inductor L1 and capacitor C7 cancel each other out, thus eliminating the current ripple of inductor L0.

[0061] Finally, capacitors C1-C5 and diodes D-D5 form a multi-boost structure. For the multi-boost structure, when the NMOS transistor S is turned on, inductor L2 charges capacitor C4 through diode D4, and inductor L2 and capacitor C5 charge capacitor C3 together through diode D3. Inductor L2 and capacitor C1 also charge capacitor C2 through diode D2.

[0062] When NMOS transistor S is turned off, inductor L2 charges capacitor C5 through diode D5, and inductor L2 and capacitor C3 charge capacitor C1 through diode D1. Capacitor C2 charges capacitor C0 through diode D0. External power supply Vin, inductor L1, capacitor C4, and capacitor C5 charge capacitor C6 through diode D6. When inductor L1 and inductor L2 are equal in magnitude, the voltages of capacitors C0 and C6 are equal, both being 0.5 times the output voltage, forming a three-level structure. This improves power transmission efficiency and reduces system losses. Furthermore, in this embodiment, inductor L1 and inductor L2 form a transformer, with inductor L1 acting as the primary side and inductor L2 acting as the secondary side.

[0063] In this embodiment, the voltage stress of each diode and the voltages of capacitors C0 and C6 are as follows:

[0064]

[0065]

[0066]

[0067]

[0068] Inductors L1 and L2 form a transformer, with inductor L1 coupled to inductor L2. N is the primary-to-secondary turns ratio of the transformer, D is the duty cycle, and V... in V is the input voltage of the external power supply Vin. o This is the output voltage.

[0069] Because photovoltaic panels have large parasitic capacitance, they cause significant leakage current. This leakage current eventually flows from the positive terminal of the photovoltaic panel back to ground through the inverter, causing substantial losses and voltage / current distortion, thus degrading the power quality of the grid. Therefore, two-level DC high-gain converters cannot suppress leakage current. However, as shown in the above formula, the diode voltage stress of this invention is very low, and when the turns ratio N=1, the DC output is a three-level structure, thereby solving the problem of leakage current caused by photovoltaic panels affecting the downstream inverter.

[0070] Example 2

[0071] This embodiment provides a second two-stage inverter structure. Unlike the two-stage inverter in Embodiment 1, this embodiment modifies the connection of the positive terminal of capacitor C6 to the positive terminal of capacitor C5, and instead connects the positive terminal of capacitor C6 to the positive terminal of capacitor C4.

[0072] In this embodiment, the voltages of capacitors C0 and C6 are respectively:

[0073]

[0074]

[0075] From the above formula, it can be seen that when At this time, the DC output is a three-level structure.

[0076] Example 3

[0077] This embodiment provides a third two-stage inverter structure. Unlike the two-stage inverter in Embodiment 1, this embodiment modifies the connection of the positive terminal of capacitor C6 to the positive terminal of capacitor C5, and instead connects the positive terminal of capacitor C6 to the positive terminal of capacitor C1.

[0078] In this embodiment, the voltages of capacitors C0 and C6 are respectively:

[0079]

[0080] Example 4

[0081] This embodiment provides a photovoltaic system, which includes a two-stage inverter for photovoltaic power generation as described in Embodiment 1, Embodiment 2, or Embodiment 3.

[0082] Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this invention. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A two-stage inverter for photovoltaic power generation, characterized in that, include The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply. The switching transistor branch is electrically connected to the first input inductor and the tail end of the first and last input inductors of the input inductor branch, and the first and last input inductors of the input inductor branch are turned on or off based on the input control signal. A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor; The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply. The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the intermediate node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch and one end of capacitor C6, respectively. The anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. The anode of the diode electrically connected to the anode of the last diode is electrically connected to the other end of the last clamping capacitor through capacitor C1. The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

2. A two-stage inverter for photovoltaic power generation, characterized in that, include The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply. The switching transistor branch is electrically connected to the first end of the input inductor of the input inductor branch and the tail end of the input inductor of the terminal branch. Based on the input control signal, the first end of the input inductor and the tail end of the input inductor of the input inductor branch are turned on or off. A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor; The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply. The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the middle node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch. The anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor and one end of capacitor C6 through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. The anode of the diode electrically connected to the anode of the last diode is electrically connected to the other end of the last clamping capacitor through capacitor C1. The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

3. A two-stage inverter for photovoltaic power generation, characterized in that, include The input inductor branch includes multiple input inductors connected in series, and the tail end of the terminal input inductor is used to connect to the positive terminal of an external power supply. The switching transistor branch is electrically connected to the first end of the input inductor of the input inductor branch and the tail end of the input inductor of the terminal branch. Based on the input control signal, the first end of the input inductor and the tail end of the input inductor of the input inductor branch are turned on or off. A diode branch includes multiple diodes connected in series, with the anode of the first diode electrically connected to the first end of the first input inductor; The output capacitor branch includes capacitor C0 and capacitor C6. One end of capacitor C0 is electrically connected to the cathode of the diode at the end of the diode branch, and the other end of capacitor C0 is electrically connected to one end of capacitor C6. The other end of capacitor C6 is used to be electrically connected to the negative terminal of the external power supply. The clamping capacitor branch includes multiple clamping capacitors connected in series. One end of the first clamping capacitor is electrically connected to the cathode of the first diode, and the other end of the first clamping capacitor is electrically connected to the intermediate node of the input inductor branch through capacitor C7. One end of the last clamping capacitor is electrically connected to the cathode of an intermediate diode in the diode branch, and the anode of the intermediate diode is electrically connected to the other end of the last clamping capacitor through inductor L2. The anode of the intermediate diode is also electrically connected to the cathode of its adjacent diode through capacitor C3. The anode of the intermediate diode is also electrically connected to the anode of the last diode through capacitor C2. One end of the anode capacitor C1 and one end of the capacitor C6 of the diode electrically connected to the anode of the last diode are electrically connected, and the other end of capacitor C1 is electrically connected to the other end of the last clamping capacitor. The half-bridge inverter unit includes a first switch and a second switch connected in series. The input terminal of the first switch is electrically connected to one end of the capacitor C0, and the output terminal of the second switch is electrically connected to the other end of the capacitor C6.

4. A two-stage inverter for photovoltaic power generation according to any one of claims 1-3, characterized in that, The input inductor branch includes inductor L1 and inductor L0. Inductor L0 is the end input inductor. One end of inductor L0 is used to connect to the positive terminal of an external power supply. The other end of inductor L0 is connected to one end of inductor L1 and capacitor C7 respectively. The other end of inductor L1 is the beginning end of the beginning input inductor.

5. A two-stage inverter for photovoltaic power generation according to claim 4, characterized in that, The diode branch includes seven diodes connected in series, namely diode D6, diode D4, diode D5, diode D3, diode D1, diode D2 and diode D0, with diode D6 being the first diode and diode D0 being the last diode. One end of the end clamping capacitor is electrically connected to the cathode of diode D5. The anode of diode D5 is electrically connected to the cathode of diode D3 through capacitor C3. The anode of diode D5 is electrically connected to the anode of diode D0 through capacitor C2. The anode of diode D2 is electrically connected to the other end of the end clamping capacitor through capacitor C1.

6. A two-stage inverter for photovoltaic power generation according to any one of claims 1-3, characterized in that, The switching transistor branch includes an NMOS transistor S, the drain of which is electrically connected to the first end of the first-end input inductor, the source of which is electrically connected to the last end of the last-end input inductor, and the gate of which is used to input the control signal.

7. A two-stage inverter for photovoltaic power generation according to any one of claims 1-3, characterized in that, The clamping capacitor branch includes capacitor C4 and capacitor C5, wherein capacitor C4 is the first-end clamping capacitor and capacitor C5 is the last-end clamping capacitor.

8. A two-stage inverter for photovoltaic power generation according to any one of claims 1-3, characterized in that, Both the first and second switching transistors are NMOS transistors, with the drain of the NMOS transistor being the input terminal of the switching transistor and the source of the NMOS transistor being the output terminal of the switching transistor.

9. A two-stage inverter for photovoltaic power generation according to any one of claims 1-3, characterized in that, The other end of the capacitor C0 is also electrically connected to one end of the inductor Lf.

10. A photovoltaic system, characterized in that, Includes a two-stage inverter for photovoltaic power generation as described in any one of claims 1-9.

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