High-gain bipolar grid-connected inverter applied to photovoltaic hydrogen production system

Abstract

The invention discloses a high-gain bipolar grid-connected inverter applied to a photovoltaic hydrogen production system, which comprises a first transformer, a second transformer, a two-phase staggered inversion unit, a three-level rectifying unit and a half-bridge inverter, and is characterized in that primary coils of the first transformer and the second transformer are connected in parallel, and secondary coils of the first transformer and the second transformer are connected in series in opposite directions; the two-phase interlaced inversion unit is used for interlacing and connecting a photovoltaic power supply with primary coils of the first transformer and the second transformer in parallel and complementing current ripples of direct current output by the photovoltaic power supply; the three-level rectifying unit is used for boosting the voltage of the alternating current output by the first transformer and the second transformer and converting the alternating current with the boosted voltage into direct current with a bipolar characteristic to be output; and the half-bridge inverter is used for converting the direct current output by the three-level rectifying unit into alternating current and outputting the alternating current to a hydrogen production power grid. According to the invention, leakage current can be suppressed, the cost is low, the size is small, and three-level output is realized.

Description

Technical Field

[0001] The invention relates to a grid-connected inverter, and in particular to a high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system. Background Art

[0002] As energy crisis and environmental pollution become increasingly serious, solar power generation technology has become a hot topic of concern and research in countries around the world. However, solar power has poor quality and strong randomness, and cannot be used in most application scenarios. Using solar energy to produce hydrogen has become an important means of absorbing solar energy. Using solar energy to produce hydrogen usually requires raising the photovoltaic voltage to the high-voltage bus voltage required for grid connection, and then converting it into AC power by the inverter, which is then transmitted to the hydrogen production plant through the hydrogen production grid transmission line to reduce transmission losses. Therefore, grid-connected inverter matching becomes crucial.

[0003] Existing grid-connected inverters generally use a two-level DC converter with an interleaved Flyback + full-bridge power frequency flipping topology to achieve energy transfer to the grid. The full-bridge inverter has a large number of switch tubes, high cost, and large size. In addition, the bus capacitor voltage ripple of the DC two-level structure is large, which can easily cause the life of the grid-connected inverter to be short. In addition, due to the large parasitic capacitance of the photovoltaic panel, a large leakage current will be caused. The leakage current will return to the ground from the positive pole of the photovoltaic panel through the grid-connected inverter, causing large losses, bringing voltage and current distortion, and reducing the power quality of the grid. In addition, the input current ripple of the existing two-level DC converter is large, and the photovoltaic panel is usually equivalent to a current source. The large current ripple reduces the overall output power of the photovoltaic panel.

[0004] At present, the traditional clamping structure cannot achieve the output three-level function. In order to achieve the three-level structure, the existing technology usually adopts the method of adding three or more coils. This method increases the cost and volume of the transformer and brings a large voltage static difference, causing uneven voltage at the three levels and causing leakage current. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a high-gain bipolar grid-connected inverter for photovoltaic hydrogen production system which can suppress leakage current, has low cost, small size and realizes three-level output.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A high-gain bipolar grid-connected inverter for use in a photovoltaic hydrogen production system, comprising:

[0008] A first transformer and a second transformer, wherein the primary coils of the first transformer and the second transformer are connected in parallel and the secondary coils are connected in series;

[0009] A two-phase interleaved inverter unit is used to connect the photovoltaic power source to the primary coils of the first transformer and the second transformer in parallel and to complement the current ripple of the direct current output by the photovoltaic power source;

[0010] The three-level rectifier unit is used to increase the voltage of the AC power output by the first transformer and the second transformer, and convert the AC power after the voltage increase into DC power with bipolar characteristics for output; specifically includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitor C1, a second capacitor C2, a first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4 The first ends of the secondary coils of the first transformer and the second transformer connected in series are respectively connected to the first end of the first capacitor C1, the first end of the second capacitor C2, the cathode of the first diode D1, and the anode of the second diode D2. The anode of the third diode D3 is connected to the cathode of the second diode D2. The anode of the fourth diode D4 is respectively connected to the cathode of the third diode D3 and the second end of the first capacitor C1. The fourth bipolar capacitor C o4 The first end of the secondary coil of the first transformer and the second transformer is connected in series with the cathode of the second diode D2, the second end of the secondary coil of the first transformer and the second transformer is connected to the cathode of the fourth diode D4, and the second end of the secondary coil of the first transformer and the second transformer is connected to the first bipolar capacitor C o1 The first terminal and the second bipolar capacitor C o2 The first end of the first bipolar capacitor C o1 The second end of the first diode D1 is connected to the anode of the first diode D1, the cathode of the sixth diode D6, and the third bipolar capacitor C o3 The first end of the second bipolar capacitor C o2 The second end of the fourth bipolar capacitor C o4 The first end of the sixth diode D6 is connected to the second end of the second capacitor C2, and the third bipolar capacitor C o3 The second end of is connected to the second end of the second capacitor C2 through a fifth forward diode D5;

[0011] The half-bridge inverter is used to convert the direct current output by the three-level rectifier unit into alternating current and then output it to the hydrogen production grid.

[0012] Furthermore, the two-phase interleaved inverter unit includes a first switch tube S C1 , the second switch tube S C2 , the third switch tube S1, the fourth switch tube S2, the first capacitor C C1 , the second capacitor CC2 , wherein the first switch tube S C1 The drain of C1 The source is connected to the first photovoltaic output terminal through the primary coil of the first transformer, and the drain of the third switch tube S1 is connected to the first switch tube S C1 The source is connected to the second photovoltaic output terminal, and the second switch tube S C2 The drain of C2 The source is connected to the first photovoltaic output terminal through the primary coil of the second transformer in turn, and the drain of the fourth switch tube S2 is connected to the second switch tube S C2 The source is connected to the second output terminal of the photovoltaic.

[0013] Furthermore, the half-bridge inverter includes the first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4 And the fifth switch tube Q1, the sixth switch tube Q2, the filter inductor L f The drain of the fifth switch tube Q1 is connected to the fourth bipolar capacitor C o4 The second end of the switch tube Q2 has a source connected to the drain of the sixth switch tube Q2, and the source of the sixth switch tube Q2 is connected to the third bipolar capacitor C o3 The second end of the filter inductor L f One end is connected to the second input end of the hydrogen production grid, and the other end is connected to the second bipolar capacitor C o2 The first end.

[0014] Furthermore, the secondary coils of the first transformer and the second transformer are connected in series in opposite directions. The turns ratio of the primary coil and the secondary coil of the first transformer and the second transformer is the same.

[0015] Furthermore, the high-gain bipolar grid-connected inverter meets the following conditions:

[0016] C s1 ≤4N 2 I in 2 L k1 / V o 2

[0017] C s2 ≤4N 2 I in 2 L k2 / Vo 2

[0018] In the formula, C s1 =C s2 , C s1 , C s2 They represent the parasitic capacitance of the third switch tube S1 and the fourth switch tube S2 respectively, N represents the turns ratio of the first transformer and the second transformer, I in Indicates the current output by the photovoltaic power source, L k1 , L k2 Respectively represent the leakage inductance of the first transformer and the second transformer, V o Represents the output voltage of the high gain bipolar grid-tied inverter.

[0019] Furthermore, the first switch tube S C1 The gate inputs the first PWM control wave signal, and the second switch tube S C2 The gate inputs the second PWM control wave signal, the gate of the third switch tube S1 inputs the third PWM control wave signal, the gate of the fourth switch tube S2 inputs the fourth PWM control wave signal, the first PWM control wave signal and the second PWM control wave signal are staggered by 180°, the third PWM control wave signal and the fourth PWM control wave signal are staggered by 180°. The gate of the fifth switch tube Q1 inputs the fifth PWM control wave signal, and the gate of the sixth switch tube Q2 inputs the sixth PWM control wave signal.

[0020] Furthermore, the first switch tube S C1 , the second switch tube S C2 The third switch tube S1 and the fourth switch tube S2 are all NMOS tubes. The fifth switch tube Q1 and the sixth switch tube Q2 are all NMOS tubes.

[0021] Compared with the prior art, the present invention has the following beneficial effects: the two-phase interleaved inverter unit of the present invention realizes input current ripple complementation, reduces the function of input current ripple, and at the same time reduces the single-channel power level and reduces the demand for inductance; the three-level rectifier unit is controlled by S1 and S2 in a 180° interleaved control mode to generate positive, negative and zero levels, effectively reducing the voltage stress of the components of the three-level rectifier unit, and at the same time, the positive and negative symmetry is effectively improved by C o1 -C o4 The bus voltage composed of series connection, the output voltage of the three-level rectifier unit has bipolar characteristics, which not only realizes the conversion from AC to DC, but also realizes high voltage gain and improves the bus voltage of the inverter; the half-bridge inverter adopts C o1 -C o4The four capacitors are connected in series, and the voltages of the four capacitors are added to form the bus voltage. The four capacitors are charged and discharged alternately, which effectively reduces the pulsation of the bus voltage and the requirements for the capacitance of the four capacitors. CBB capacitors can be used to replace electrolytic capacitors, which greatly improves the service life of the inverter. The bus voltage of the half-bridge inverter has a bipolar characteristic, and Q1 and Q2 adopt a power frequency complementary control method; the inverter also has two clamping structures (S C1 , S C2 , C C1 , C C2 ), not only realizes voltage clamping but also k1 , L k2 Resonance, to achieve soft switching of S1 and S2; S C1 , S C2 , S1, S2 adopt 180° staggered control mode, and S C1 , S C2 Complementary control, this control method is to achieve the characteristics of three levels; the inverter has isolation performance and bipolar function, which can effectively reduce the leakage current caused by the parasitic capacitance of the photovoltaic panel on the input side; the overall circuit has few components, low cost and small size. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 An electrical schematic diagram of a high-gain bipolar grid-connected inverter for use in a photovoltaic hydrogen production system provided by an embodiment of the present invention;

[0023] Figure 2 This is an electrical schematic diagram of an embodiment of the present invention when working in mode I;

[0024] Figure 3 This is an electrical schematic diagram of an embodiment of the present invention when working in mode II;

[0025] Figure 4 It is an electrical schematic diagram of an embodiment of the present invention when working in mode III;

[0026] Figure 5 It is an electrical schematic diagram of an embodiment of the present invention when working in mode IV;

[0027] Figure 6 It is an electrical schematic diagram of an embodiment of the present invention when working in mode V;

[0028] Figure 7 It is an electrical schematic diagram of an embodiment of the present invention when working in mode VI;

[0029] Figure 8 , which is a theoretical waveform of an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0031] An embodiment of the present invention provides a high-gain bipolar grid-connected inverter for use in a photovoltaic hydrogen production system, comprising a first transformer, a second transformer, a two-phase interleaved inverter unit, a three-level rectifier unit, and a half-bridge inverter, wherein the primary coils of the first transformer and the second transformer are connected in parallel, and the secondary coils are connected in series in opposite directions; the two-phase interleaved inverter unit is used to interleave the photovoltaic power source with the primary coils of the first transformer and the second transformer, respectively, in parallel, and to complement the current ripple of the direct current output by the photovoltaic power source; the three-level rectifier unit is used to increase the voltage of the alternating current output by the first transformer and the second transformer, and convert the alternating current with the increased voltage into direct current with bipolar characteristics for output; the half-bridge inverter is used to convert the direct current output by the three-level rectifier unit into alternating current, and then output it to the hydrogen production grid.

[0032] like Figure 1 As shown, the two-phase interleaved inverter unit includes a first switch tube S C1 , the second switch tube S C2 , the third switch tube S1, the fourth switch tube S2, the first capacitor C C1 , the second capacitor C C2 , wherein the first switch tube S C1 The drain of C1 The source is connected to the first photovoltaic output terminal through the primary coil of the first transformer, and the drain of the third switch tube S1 is connected to the first switch tube S C1 The source is connected to the second photovoltaic output terminal, and the second switch tube S C2 The drain of C2 The source is connected to the first photovoltaic output terminal through the primary coil of the second transformer in turn, and the drain of the fourth switch tube S2 is connected to the second switch tube S C2 The source is connected to the second output terminal of the photovoltaic.

[0033] like Figure 1 As shown, the three-level rectifying unit specifically includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitor C1, a second capacitor C2, a first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4The first ends of the secondary coils of the first transformer and the second transformer connected in series are respectively connected to the first end of the first capacitor C1, the first end of the second capacitor C2, the cathode of the first diode D1, and the anode of the second diode D2. The anode of the third diode D3 is connected to the cathode of the second diode D2. The anode of the fourth diode D4 is respectively connected to the cathode of the third diode D3 and the second end of the first capacitor C1. The fourth bipolar capacitor C o4 The first end of the secondary coil of the first transformer and the second transformer is connected in series with the cathode of the second diode D2, the second end of the secondary coil of the first transformer and the second transformer is connected to the cathode of the fourth diode D4, and the second end of the secondary coil of the first transformer and the second transformer is connected to the first bipolar capacitor C o1 The first terminal and the second bipolar capacitor C o2 The first end of the first bipolar capacitor C o1 The second end of the first diode D1 is connected to the anode of the first diode D1, the cathode of the sixth diode D6, and the third bipolar capacitor C o3 The first end of the second bipolar capacitor C o2 The second end of the fourth bipolar capacitor C o4 The first end of the sixth diode D6 is connected to the second end of the second capacitor C2, and the third bipolar capacitor C o3 The second end of is connected to the second end of the second capacitor C2 through a forward fifth diode D5.

[0034] like Figure 1 As shown, the half-bridge inverter includes the first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4 And the fifth switch tube Q1, the sixth switch tube Q2, the filter inductor L f The drain of the fifth switch tube Q1 is connected to the fourth bipolar capacitor C o4 The second end of the switch tube Q2 has a source connected to the drain of the sixth switch tube Q2, and the source of the sixth switch tube Q2 is connected to the third bipolar capacitor C o3 The second end of the filter inductor L f One end is connected to the second input end of the hydrogen production grid, and the other end is connected to the second bipolar capacitor C o2 The first end of the first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4Located in both the three-level rectifier unit and the half-bridge inverter, these devices play two roles and are therefore included in both unit circuits.

[0035] Among them, the first switch tube S C1 , the second switch tube S C2 The third switch tube S1 and the fourth switch tube S2 are all NMOS tubes. The fifth switch tube Q1 and the sixth switch tube Q2 are all NMOS tubes. C1 The gate inputs the first PWM control wave signal, and the second switch tube S C2 The gate inputs the second PWM control wave signal, the gate of the third switch tube S1 inputs the third PWM control wave signal, the gate of the fourth switch tube S2 inputs the fourth PWM control wave signal, the first PWM control wave signal and the second PWM control wave signal are staggered by 180°, and the third PWM control wave signal and the fourth PWM control wave signal are staggered by 180°. The gate of the fifth switch tube Q1 inputs the fifth PWM control wave signal, and the gate of the sixth switch tube Q2 inputs the sixth PWM control wave signal. Each PWM control wave signal can control the conduction and shutdown of the switch tube, which is specifically output by the external drive circuit.

[0036] The high-gain bipolar grid-connected inverter of the present invention meets the following conditions:

[0037] C s1 ≤4N 2 I in 2 L k1 / V o 2

[0038] C s2 ≤4N 2 I in 2 L k2 / V o 2

[0039] In the formula, C s1 =C s2 , C s1 , C s2 They represent the parasitic capacitance of the third switch tube S1 and the fourth switch tube S2 respectively, N represents the turns ratio of the first transformer and the second transformer, and the turns ratios of the two transformers are the same, and I in Indicates the current output by the photovoltaic power source, L k1 , L k2 Respectively represent the leakage inductance of the first transformer and the second transformer, V o Represents the output voltage of the high-gain bipolar grid-connected inverter. The final bus voltage gain is: M CCM=4N / (1-D), D is the duty cycle of the PWM control wave signal of S1 and S2.

[0040] The working principle of the present invention is described below. In the figure, Lk1 and Lk2 are the leakage inductance of the first transformer and the second transformer, Lm 11 , Lm 21 is the excitation inductance of the primary coils of the first transformer and the second transformer.

[0041] like Figure 2 As shown, in mode I, S1 and S2 are turned on at the same time, L k1 , L k2 , L m11 , L m21 The three-level rectifier unit does not work. Since Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0042] like Figure 3 As shown, in mode II, S1 is turned on, S2 is turned off, and L k1 , L m11 Charged by photovoltaic power source, L k2 , L m21 Release energy and with C C2 Resonance, L k2 Because of the special design of the resonant working mode, the current is reversed, and the soft switch of S2 can be realized for mode III. The three-level rectifier unit works at this time. The port voltage of L2 and L4 is positive at point A and negative at point B. L2 and L4 are connected in series through D2 to C o2 Charging, L2, L4 in series with C1 through D4 to C o4 Charging, L2, L4 in series C o1 Charge C2 through D6, C o1 Discharge, in addition, C o3 Also discharges, because Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the hydrogen production grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0043] like Figure 4 As shown, in mode III, S1 and S2 are turned on at the same time, L k1 , L m11 Charged by photovoltaic power source, Lk2 , L m21 Release energy and with C C2 Resonance, L k2 Because of the special design of the resonant working mode, the current is reversed, and the soft switch of S2 can be realized for mode III. The three-level rectifier unit works at this time. The port voltage of L2 and L4 is positive at point A and negative at point B. L2 and L4 are connected in series through D2 to C o2 Charging, L2, L4 Connect C1 in series to C through D4 o4 Charging, L2, L4 in series C o1 Charge C2 through D6, C o1 Discharge, in addition, C o3 Also discharges, because Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the hydrogen production grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0044] like Figure 5 As shown, in mode IV, S1 and S2 are turned on at the same time, L k1 , L k2 , L m11 , L m21 The three-level rectifier unit does not work. Since Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the hydrogen production grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0045] like Figure 6 As shown, in mode V, S2 is on, S1 is off, and L k2 , L m21 Charged by photovoltaic power source, L k1 , L m11 Release energy and with C C1 Resonance, L k1 Because of the special design of the resonant working mode, the current is reversed, and the soft switch of S1 can be realized for mode VI. The three-level rectifier unit works at this time. The port voltage of L2 and L4 is positive at point B and negative at point A. L2 and L4 are connected in series with C o2 C1 is charged through D3, and C2 is charged through D5 by L2 and L4 in series. o3 Charging, L2, L4 to C through D1 o1 Charging, C o1 and Co3 Charging, in addition, C o2 and C o4 Discharge, because Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the hydrogen production grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0046] like Figure 7 As shown, in mode VI, S1 and S2 are turned on at the same time, L k1 , L k2 , L m11 , L m21 The three-level rectifier unit works at this time. The voltage at the ports of L2 and L4 is positive at point B and negative at point A. L2 and L4 are connected in series. o2 C1 is charged through D3, and C2 is charged through D5 by L2 and L4 in series. o3 Charging, L2, L4 to C through D1 o1 Charging, C o1 and C o3 Charging, in addition, C o2 and C o4 Discharge, because Q1 and Q2 adopt the power frequency complementary control mode, when Q1 is turned on and Q2 is turned off, C o2 and C o4 The series connection provides energy to the hydrogen production grid. When Q2 is turned on and Q1 is turned off, C o1 and C o3 The series connection provides energy to the hydrogen production grid.

[0047] The main theoretical waveforms of high-gain bipolar grid-connected inverter are as follows: Figure 8 shown.

[0048] The two-phase interleaved inverter unit of the embodiment of the present invention realizes input current ripple complementation, reduces the function of input current ripple, and at the same time reduces the single-channel power level and reduces the demand for inductance; the three-level rectifier unit is controlled by S1 and S2 in a 180° interleaved control mode to generate positive, negative and zero levels, effectively reducing the voltage stress of the components of the three-level rectifier unit, and at the same time, the positive and negative symmetry is effectively improved by C o1 -C o4 The bus voltage composed of series connection, the output voltage of the three-level rectifier unit has bipolar characteristics, which not only realizes the conversion from AC to DC, but also realizes high voltage gain and improves the bus voltage of the inverter; the half-bridge inverter adopts C o1 -C o4The four capacitors are connected in series, and the voltages of the four capacitors are added to form the bus voltage. The four capacitors are charged and discharged alternately, which effectively reduces the pulsation of the bus voltage and the requirements for the capacitance of the four capacitors. CBB capacitors can be used to replace electrolytic capacitors, which greatly improves the service life of the inverter. The bus voltage of the half-bridge inverter has a bipolar characteristic, and Q1 and Q2 adopt a power frequency complementary control method; the inverter also has two clamping structures (S C1 , S C2 , C C1 , C C2 ), not only realizes voltage clamping but also k1 , L k2 Resonance, to achieve soft switching of S1 and S2; S C1 , S C2 , S1, S2 adopt 180° staggered control mode, and S C1 , S C2 Complementary control, this control method is to achieve the characteristics of three levels; the inverter has isolation performance and bipolar function, which can effectively reduce the leakage current caused by the parasitic capacitance of the photovoltaic panel on the input side; the overall circuit has few components, low cost and small size.

[0049] It should be noted that, in this document, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0050] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system, characterized in that: include A first transformer and a second transformer, wherein the primary coils of the first transformer and the second transformer are connected in parallel and the secondary coils are connected in series; A two-phase interleaved inverter unit is used to connect the photovoltaic power source to the primary coils of the first transformer and the second transformer in parallel and to complement the current ripple of the direct current output by the photovoltaic power source; The three-level rectifier unit is used to increase the voltage of the AC power output by the first transformer and the second transformer, and convert the AC power after the voltage increase into DC power with bipolar characteristics for output; specifically includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first capacitor C1, a second capacitor C2, a first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4 The first ends of the secondary coils of the first transformer and the second transformer connected in series are respectively connected to the first end of the first capacitor C1, the first end of the second capacitor C2, the cathode of the first diode D1, and the anode of the second diode D2. The anode of the third diode D3 is connected to the cathode of the second diode D2. The anode of the fourth diode D4 is respectively connected to the cathode of the third diode D3 and the second end of the first capacitor C1. The fourth bipolar capacitor C o4 The first end of the secondary coil of the first transformer and the second transformer is connected in series with the cathode of the second diode D2, the second end of the secondary coil of the first transformer and the second transformer is connected to the cathode of the fourth diode D4, and the second end of the secondary coil of the first transformer and the second transformer is connected to the first bipolar capacitor C o1 The first terminal and the second bipolar capacitor C o2 The first end of the first bipolar capacitor C o1 The second end of the first diode D1 is connected to the anode of the first diode D1, the cathode of the sixth diode D6, and the third bipolar capacitor C o3 The first end of the second bipolar capacitor C o2 The second end of the fourth bipolar capacitor C o4 The first end of the sixth diode D6 is connected to the second end of the second capacitor C2, and the third bipolar capacitor C o3 The second end of is connected to the second end of the second capacitor C2 through a fifth forward diode D5; The half-bridge inverter is used to convert the direct current output by the three-level rectifier unit into alternating current and then output it to the hydrogen production grid.

2. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 1, characterized in that: The two-phase interleaved inverter unit includes a first switch tube S C1 , the second switch tube S C2 , the third switch tube S1, the fourth switch tube S2, the first capacitor C C1 , the second capacitor C C2 , wherein the first switch tube S C1 The drain of C1 The source is connected to the first photovoltaic output terminal through the primary coil of the first transformer, and the drain of the third switch tube S1 is connected to the first switch tube S C1 The source is connected to the second photovoltaic output terminal, and the second switch tube S C2 The drain of C2 The source is connected to the first photovoltaic output terminal through the primary coil of the second transformer in turn, and the drain of the fourth switch tube S2 is connected to the second switch tube S C2 The source is connected to the second output terminal of the photovoltaic.

3. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 2, characterized in that: The half-bridge inverter includes the first bipolar capacitor C o1 , the second bipolar capacitor C o2 , the third bipolar capacitor C o3 , the fourth bipolar capacitor C o4 And the fifth switch tube Q1, the sixth switch tube Q2, the filter inductor L f The drain of the fifth switch tube Q1 is connected to the fourth bipolar capacitor C o4 The second end of the switch tube Q2 is connected to the drain of the sixth switch tube Q2, and the source of the sixth switch tube Q2 is connected to the third bipolar capacitor C o3 The second end of the filter inductor L f One end is connected to the second input end of the hydrogen production grid, and the other end is connected to the second bipolar capacitor C o2 The first end.

4. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 3, characterized in that: The secondary coils of the first transformer and the second transformer are connected in series in opposite directions.

5. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 4, characterized in that: The turns ratio of the primary coil and the secondary coil of the first transformer and the second transformer is the same.

6. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 5, characterized in that: The high-gain bipolar grid-connected inverter meets the following conditions: C s1 ≤4N 2 I in 2 L k1 / V o 2 C s2 ≤4N 2 I in 2 L k2 / V o 2 In the formula, C s1 =C s2 , C s1 , C s2 They represent the parasitic capacitance of the third switch tube S1 and the fourth switch tube S2 respectively, N represents the turns ratio of the first transformer and the second transformer, I in Indicates the current output by the photovoltaic power source, L k1 , L k2 Respectively represent the leakage inductance of the first transformer and the second transformer, V o Represents the output voltage of the high gain bipolar grid-tied inverter.

7. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 2, characterized in that: The first switch tube S C1 The gate inputs the first PWM control wave signal, and the second switch tube S C2 The gate inputs the second PWM control wave signal, the gate of the third switch tube S1 inputs the third PWM control wave signal, the gate of the fourth switch tube S2 inputs the fourth PWM control wave signal, the first PWM control wave signal and the second PWM control wave signal are staggered 180°, and the third PWM control wave signal and the fourth PWM control wave signal are staggered 180°.

8. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 3, characterized in that: The gate of the fifth switch tube Q1 inputs a fifth PWM control wave signal, and the gate of the sixth switch tube Q2 inputs a sixth PWM control wave signal.

9. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 2, characterized in that: The first switch tube S C1 , the second switch tube S C2 The third switch tube S1 and the fourth switch tube S2 are all NMOS tubes.

10. The high-gain bipolar grid-connected inverter used in a photovoltaic hydrogen production system according to claim 3, characterized in that: The fifth switch tube Q1 and the sixth switch tube Q2 are both NMOS tubes.

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