Two-way low-grid-voltage high-power grid-connected inverter
By designing a dual-path high-power grid-connected inverter with low grid voltage, and utilizing flyback circuits, inverter circuits, and filter circuits, the high-efficiency operation of the high-power grid-connected inverter under low grid voltage conditions is achieved, solving the problem of insufficient power in micro-inverters.
Patent Information
- Application Number
- CN202520108487.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2035-01-17
AI Technical Summary
Existing micro photovoltaic inverters have insufficient power under low grid voltage conditions, making it difficult to achieve high-power grid connection.
The system employs a dual-path low-grid-voltage high-power grid-connected inverter, which includes a flyback circuit, an inverter circuit, a relay, and a filter circuit. The photovoltaic modules are connected through four main transformers and current transformers. The secondary side of the main transformer is connected to the inverter circuit through SiC diodes. The output of the inverter circuit is connected to the filter circuit through a relay. The filter circuit includes a common-mode inductor connected in sequence.
High-power grid-connected inverters of 800W, 1000W and 1200W are realized in low grid voltage environments to meet the high power requirements under low grid voltage conditions.
Smart Images
Figure CN223771953U_ABST
Abstract
Description
Technical Field
[0001] This utility model inverter relates to the technical field, specifically to a dual-path low grid voltage high-power grid-connected inverter. Background Technology
[0002] A photovoltaic grid-connected inverter is a device that converts direct current (DC) to alternating current (AC) and can then connect the converted AC power to the mains power grid.
[0003] Current grid-connected inverters generally have a power output of over 1000W. However, due to limitations in overall product size, micro-inverters typically have a power output of less than 1000W. Furthermore, under low grid voltage conditions, the power output of micro-photovoltaic grid-connected inverters is even lower.
[0004] Therefore, how to provide a high-power grid-connected inverter suitable for low grid voltage environments has become an urgent problem to be solved in this field. Utility Model Content
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-power grid-connected inverter suitable for low grid voltage environments.
[0006] To achieve the above objectives, the dual-path low-grid-voltage high-power grid-connected inverter of this utility model has the following configuration:
[0007] This dual-path low-grid-voltage high-power grid-connected inverter includes a flyback circuit, an inverter circuit, a relay, and a filter circuit. The input terminal of the flyback circuit is connected to a photovoltaic module. The flyback circuit includes several main transformers. The output of the filter circuit is connected to the AC grid. The inverter is characterized by including four main transformers T0, T1, T2, and T3. The primary windings of each main transformer T0, T1, T2, and T3 are connected to corresponding current transformers CT0, CT1, and CT2. 1. CT2 and CT3 are connected to photovoltaic modules. The primary side of each main transformer T0, T1, T2, and T3 is also connected to its corresponding control unit. The secondary side of each main transformer T0, T1, T2, and T3 is connected to the inverter circuit through its corresponding SiC diodes D1, D2, D30, and D31. The inverter circuit includes two thyristors D20 and D21 and secondary MOSFETs QS1 and QS2 corresponding to the two thyristors D20 and D21, respectively. The node between the thyristors D20 and D21 and the secondary MOSFETs QS1 and QS2 is the output terminal of the inverter circuit. The output terminal of the inverter circuit is connected to the filter circuit through relay k1. The filter circuit includes three common-mode inductors L3, L2, and L1 connected in sequence. A filter capacitor is connected between the primary and secondary sides of each common-mode inductor L3, L2, and L1.
[0008] In this dual-path low grid voltage high-power grid-connected inverter, each control unit includes two parallel primary-side MOSFETs QP0, QP1, QP2, QP3, QP4, QP5, QP6, and QP7. The gates of the two parallel primary-side MOSFETs are connected to control signals GP0, GP1, GP2, and GP3, the drains are connected to the primary side of the corresponding main transformers T0, T1, T2, and T3, and the sources are grounded.
[0009] In this dual-path low-grid-voltage high-power grid-connected inverter, the anodes of thyristors D20 and D21 in the inverter circuit are connected to thyristor drive resistors R53 and R55, respectively, and to the secondary side of each main transformer T0, T1, T2, and T3; the cathodes of thyristors D20 and D21 are the output terminals VH+ and VH- of the inverter circuit, respectively, and are connected to the drains of the corresponding secondary-side MOSFETs QS1 and QS2, respectively, and are also grounded through varistors RV2 and RV4, respectively; the gates of the secondary-side MOSFETs QS1 and QS2 are connected to the corresponding control terminals GS1 and GS2, and their sources are grounded through secondary-side current sensing resistors R118, R119, R231, and R233.
[0010] In this dual-path low grid voltage high-power grid-connected inverter, a varistor RV1 is connected between the primary and secondary sides of the common-mode inductor L3, a varistor RV3 and a discharge tube are connected between the primary and secondary sides of the common-mode inductor L2, and a fuse F2 is connected between the common-mode inductor L2 and the common-mode inductor L1.
[0011] This dual-path low-grid-voltage high-power grid-connected inverter has a rated power of 800W or 1000W, wherein:
[0012] The inductance range of the main transformers T0, T1, T2, and T3 is 2.8uH to 3.2uH, and the turns ratio is 3:10 to 2:7.
[0013] The SiC diodes D1, D2, D30, and D31 have a DC reverse withstand voltage of 1200V and a continuous forward current IF of 9.5A to 15A.
[0014] The thyristor drive resistors R53 and R55 have an accuracy of 1%, a temperature coefficient of 100ppm / ℃, a rated voltage of 400V, and a resistance value of 150Ω~200Ω.
[0015] The off-state peak voltage Vdrm of the thyristors D20 and D21 is 800V, and the on-state RMS current It(rms) is 21A~40A.
[0016] The drain-source voltage of the secondary-side MOSFETs QS1 and QS2 is 650V, and the continuous drain current is 27.8A to 32.8A.
[0017] The maximum switching current of the relay k1 is 15A to 20A, and the coil voltage is 12Vdc.
[0018] The rated voltage of the fuse F2 is 250V, and the rated current is 12.6A to 15A.
[0019] The common-mode inductor L1 is made of MnZn ferrite, with a minimum diameter of 0.81mm and 2UEW enameled wire, and 14 turns; the inductance range is 1.5mH to 2.8mH.
[0020] The common-mode inductor L2 is amorphous, with a minimum diameter of 1.2mm and 2UEW enameled wire, 13 turns; the inductance range is 4mH to 6mH.
[0021] The common-mode inductor L3 is made of MnZn ferrite Minφ1.2mm 2UEW enameled wire with 21 turns; the inductance range is 4mH to 6mH.
[0022] This dual-path low-grid-voltage high-power grid-connected inverter has a rated power of 1200W, of which:
[0023] The inductance range of the main transformers T0, T1, T2, and T3 is 2.8uH to 3.2uH, and the turns ratio is 3:10 to 2:7.
[0024] The SiC diodes D1, D2, D30, and D31 have a DC reverse withstand voltage of 1200V and a continuous forward current IF of 9.5A to 15A.
[0025] The primary-side MOSFETs QP0, QP1, QP2, QP3, QP4, QP5, QP6, and QP7 are all N-channel MOSFETs with a maximum drain current Id = 35A, drain-source voltage Vds = 150V, drain-source resistance Rds(on) = 9.5mΩ, and gate-source voltage Vgs ≤ ±20V.
[0026] The current transformers CT0, CT1, CT2, and CT3 have an inductance of 3mH (L1-3), a minimum DC resistance of 6.5Ω (Min, DCR(1-3), a maximum DC resistance of 0.75mΩ (max, DCR(8-7), and a maximum turns ratio of 125:1 (max, N1:N2).
[0027] The thyristor drive resistors R53 and R55 have an accuracy of 1%, a temperature coefficient of 100ppm / ℃, a rated voltage of 400V, and a resistance value of 150Ω~200Ω.
[0028] The off-state peak voltage Vdrm of the thyristors D20 and D21 is 800V, and the on-state RMS current It(rms) is 40A~80A.
[0029] The drain-source voltage of the secondary-side MOSFETs QS1 and QS2 is 650V, and the continuous drain current is 49A to 78A.
[0030] The maximum switching current of the relay k1 is 15A to 20A, and the coil voltage is 12Vdc.
[0031] The rated voltage of the fuse F2 is 250V, and the rated current is 15A to 20A.
[0032] The resistance values of the secondary current sensing resistors R231, R118, R233, and R119 are 20mR.
[0033] The rated voltage of varistors RV1, RV2, RV3, and RV4 is 175VAC, the rated power is 99J, and the rated current is 6KA.
[0034] The common-mode inductor L1 is made of MnZn ferrite, with a minimum diameter of 0.81mm and 2UEW enameled wire, and 14 turns; the inductance range is 1.5mH to 2.8mH.
[0035] The common-mode inductor L2 is amorphous, with a minimum diameter of 1.2mm and 2UEW enameled wire, 13 turns; the inductance range is 4mH to 6mH.
[0036] The common-mode inductor L3 is made of MnZn ferrite Minφ1.2mm 2UEW enameled wire with 21 turns; the inductance range is 4mH to 6mH.
[0037] This utility model discloses a dual-path, low-grid-voltage, high-power grid-connected inverter, comprising a flyback circuit, an inverter circuit, a relay, and a filter circuit. It uses four main transformers connected to photovoltaic modules via corresponding current transformers. The secondary windings of each main transformer are connected to the inverter circuit via corresponding SiC diodes. The output of the inverter circuit is connected to the filter circuit via relay k1. The filter circuit includes three common-mode inductors connected in sequence. This provides a high-power grid-connected inverter suitable for low-grid-voltage environments with rated power reaching 800W, 1000W, and 1200W. Attached Figure Description
[0038] Figure 1 This is a schematic diagram of the circuit structure of the dual-path low grid voltage high-power grid-connected inverter of this utility model. Detailed Implementation
[0039] In order to better understand the technical content of this utility model, the following embodiments are provided for detailed description.
[0040] Please see Figure 1 The diagram shown is a schematic diagram of the circuit structure of the dual-path low grid voltage high-power grid-connected inverter of this utility model.
[0041] In one embodiment, a dual-path low-grid-voltage high-power grid-connected inverter includes: a flyback circuit, an inverter circuit, a relay, and a filter circuit. The input terminal of the flyback circuit is connected to a photovoltaic module. The flyback circuit includes several main transformers. The output of the filter circuit is connected to the AC grid. The inverter is characterized by including four main transformers T0, T1, T2, and T3, with the primary windings of each main transformer T0, T1, T2, and T3 connected to corresponding current transformers CT0, CT1, and CT2. 1. CT2 and CT3 are connected to photovoltaic modules. The primary side of each main transformer T0, T1, T2, and T3 is also connected to its corresponding control unit. The secondary side of each main transformer T0, T1, T2, and T3 is connected to the inverter circuit through its corresponding SiC diodes D1, D2, D30, and D31. The inverter circuit includes two thyristors D20 and D21 and secondary MOSFETs QS1 and QS2 corresponding to the two thyristors D20 and D21, respectively. The node between the thyristors D20 and D21 and the secondary MOSFETs QS1 and QS2 is the output terminal of the inverter circuit. The output terminal of the inverter circuit is connected to the filter circuit through relay k1. The filter circuit includes three common-mode inductors L3, L2, and L1 connected in sequence. A filter capacitor is connected between the primary and secondary sides of each common-mode inductor L3, L2, and L1.
[0042] In a preferred embodiment, each of the control units includes two parallel primary-side MOSFETs QP0, QP1, QP2, QP3, QP4, QP5, QP6, and QP7. The gates of the two parallel primary-side MOSFETs are connected to control signals GP0, GP1, GP2, and GP3, the drains are connected to the primary side of the corresponding main transformers T0, T1, T2, and T3, and the sources are grounded.
[0043] In a further preferred embodiment, the anodes of thyristors D20 and D21 in the inverter circuit are connected to thyristor drive resistors R53 and R55, respectively, and to the secondary side of each main transformer T0, T1, T2, and T3. The anodes of thyristors D20 and D21 are also grounded through varistor RV5. The cathodes of thyristors D20 and D21 are the output terminals VH+ and VH- of the inverter circuit, respectively, and are connected to the drains of the corresponding secondary MOSFETs QS1 and QS2, respectively, and are also grounded through varistor RV2 and RV4, respectively. The gates of the secondary MOSFETs QS1 and QS2 are connected to the corresponding control terminals GS1 and GS2, and their sources are grounded through secondary current sensing resistors R118, R119, R231, and R233.
[0044] In a more preferred embodiment, a varistor RV1 is connected between the primary and secondary sides of the common-mode inductor L3, a varistor RV3 and a discharge tube are connected between the primary and secondary sides of the common-mode inductor L2, and a fuse F2 is connected between the common-mode inductor L2 and the common-mode inductor L1. Varistors RV7 and RV8 are provided at the output terminal of the filter circuit.
[0045] In the application of this utility model, the rated power of the dual-path low-grid-voltage high-power grid-connected inverter can be 800W or 1000W. Wherein:
[0046] The inductance range of the main transformers T0, T1, T2, and T3 is 2.8uH to 3.2uH, and the turns ratio is 3:10 to 2:7.
[0047] The SiC diodes D1, D2, D30, and D31 have a DC reverse withstand voltage of 1200V and a continuous forward current IF of 9.5A to 15A.
[0048] The thyristor drive resistors R53 and R55 have an accuracy of 1%, a temperature coefficient of 100ppm / ℃, a rated voltage of 400V, and a resistance value of 150Ω~200Ω.
[0049] The off-state peak voltage Vdrm of the thyristors D20 and D21 is 800V, and the on-state RMS current It(rms) is 21A~40A.
[0050] The drain-source voltage of the secondary-side MOSFETs QS1 and QS2 is 650V, and the continuous drain current is 27.8A to 32.8A.
[0051] The maximum switching current of the relay k1 is 15A to 20A, and the coil voltage is 12Vdc.
[0052] The rated voltage of the fuse F2 is 250V, and the rated current is 12.6A to 15A.
[0053] The common-mode inductor L1 is made of MnZn ferrite, with a minimum diameter of 0.81mm and 2UEW enameled wire, and 14 turns; the inductance range is 1.5mH to 2.8mH.
[0054] The common-mode inductor L2 is amorphous, with a minimum diameter of 1.2mm and 2UEW enameled wire, 13 turns; the inductance range is 4mH to 6mH.
[0055] The common-mode inductor L3 is made of MnZn ferrite Minφ1.2mm 2UEW enameled wire with 21 turns; the inductance range is 4mH to 6mH.
[0056] The rated power of this dual-path low-grid-voltage high-power grid-connected inverter can also be 1200W, in which case:
[0057] The inductance range of the main transformers T0, T1, T2, and T3 is 2.8uH to 3.2uH, and the turns ratio is 3:10 to 2:7.
[0058] The SiC diodes D1, D2, D30, and D31 have a DC reverse withstand voltage of 1200V and a continuous forward current IF of 9.5A to 15A.
[0059] The primary-side MOSFETs QP0, QP1, QP2, QP3, QP4, QP5, QP6, and QP7 are all N-channel MOSFETs with a maximum drain current Id = 35A, drain-source voltage Vds = 150V, drain-source resistance Rds(on) = 9.5mΩ, and gate-source voltage Vgs ≤ ±20V.
[0060] The current transformers CT0, CT1, CT2, and CT3 have an inductance of 3mH (L1-3), a minimum DC resistance of 6.5Ω (Min, DCR(1-3), a maximum DC resistance of 0.75mΩ (max, DCR(8-7), and a maximum turns ratio of 125:1 (max, N1:N2).
[0061] The thyristor drive resistors R53 and R55 have an accuracy of 1%, a temperature coefficient of 100ppm / ℃, a rated voltage of 400V, and a resistance value of 150Ω~200Ω.
[0062] The off-state peak voltage Vdrm of the thyristors D20 and D21 is 800V, and the on-state RMS current It(rms) is 40A~80A.
[0063] The drain-source voltage of the secondary-side MOSFETs QS1 and QS2 is 650V, and the continuous drain current is 49A to 78A.
[0064] The maximum switching current of the relay k1 is 15A to 20A, and the coil voltage is 12Vdc.
[0065] The rated voltage of the fuse F2 is 250V, and the rated current is 15A to 20A.
[0066] The resistance values of the secondary current sensing resistors R231, R118, R233, and R119 are 20mR.
[0067] The rated voltage of varistors RV1, RV2, RV3, RV4, RV7, and RV8 is 175VAC, the rated power is 99J, and the rated current is 6KA.
[0068] The rated voltage of the varistor RV5 is 300VAC, the rated power is 175J, and the rated current is 6KA.
[0069] The common-mode inductor L1 is made of MnZn ferrite, with a minimum diameter of 0.81mm and 2UEW enameled wire, and 14 turns; the inductance range is 1.5mH to 2.8mH.
[0070] The common-mode inductor L2 is amorphous, with a minimum diameter of 1.2mm and 2UEW enameled wire, 13 turns; the inductance range is 4mH to 6mH.
[0071] The common-mode inductor L3 is made of MnZn ferrite Minφ1.2mm 2UEW enameled wire with 21 turns; the inductance range is 4mH to 6mH.
[0072] This utility model discloses a dual-path, low-grid-voltage, high-power grid-connected inverter, comprising a flyback circuit, an inverter circuit, a relay, and a filter circuit. It uses four main transformers connected to photovoltaic modules via corresponding current transformers. The secondary windings of each main transformer are connected to the inverter circuit via corresponding SiC diodes. The output of the inverter circuit is connected to the filter circuit via relay k1. The filter circuit includes three common-mode inductors connected in sequence. This provides a high-power grid-connected inverter suitable for low-grid-voltage environments with rated power reaching 800W, 1000W, and 1200W.
[0073] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be considered illustrative rather than restrictive.
Claims
1. A two-way low grid voltage high power grid-connected inverter, comprising a flyback circuit, an inverter circuit, a relay and a filter circuit, the input end of the flyback circuit being connected to a photovoltaic module, the flyback circuit comprising a plurality of main transformers, the output of the filter circuit being connected to an alternating current grid, characterized in that, The four main transformers T0, T1, T2 and T3 are connected to the photovoltaic assembly through the corresponding current transformers CT0, CT1, CT2 and CT3, and the primary side of each main transformer T0, T1, T2 and T3 is also connected to the corresponding control unit; the secondary side of each main transformer T0, T1, T2 and T3 is connected to the inverter circuit through the corresponding SiC diode D1, D2, D30 and D31, the inverter circuit includes two thyristors D20 and D21 and the corresponding secondary side MOS tubes QS1 and QS2, the node between the thyristors D20 and D21 and the secondary side MOS tubes QS1 and QS2 is the output end of the inverter circuit, the output end of the inverter circuit is connected to the filter circuit through the relay k1, and the filter circuit includes three common mode inductors L3, L2 and L1 connected in sequence, and each common mode inductor L3, L2 and L1 is connected with a filter capacitor between the primary side and the secondary side.
2. The dual-path low-mains-voltage high-power grid-tied inverter according to claim 1, characterized in that, Each control unit includes two parallel primary side MOS tubes QP0, QP1, QP2, QP3, QP4, QP5, QP6 and QP7, the gates of the two parallel primary side MOS tubes are connected to the control signals GP0, GP1, GP2 and GP3, the drains are connected to the primary side of the corresponding main transformer T0, T1, T2 and T3, and the sources are grounded.
3. The two-path low-mains-voltage high-power grid-tied inverter according to claim 2, characterized in that, The anodes of the thyristors D20 and D21 in the inverter circuit are connected to the thyristor drive resistors R53 and R55, and are connected to the secondary side of each main transformer T0, T1, T2 and T3; the cathodes of the thyristors D20 and D21 are the output ends VH+ and VH- of the inverter circuit, and are connected to the drains of the corresponding secondary side MOS tubes QS1 and QS2, and are also connected to the ground through the voltage-dependent resistors RV2 and RV4; the gates of the secondary side MOS tubes QS1 and QS2 are connected to the corresponding control ends GS1 and GS2, and the sources are connected to the ground through the secondary side current detection resistors R118, R119, R231 and R233.
4. The two-phase low-mains-voltage high-power grid-tie inverter according to claim 3, characterized in that The common mode inductor L3 is connected with a voltage-dependent resistor RV1 between the primary side and the secondary side, the common mode inductor L2 is connected with a voltage-dependent resistor RV3 and a discharge tube between the primary side and the secondary side, and the common mode inductor L2 is connected with a fuse F2 between the common mode inductor L2 and the common mode inductor L1.
5. The two-phase low-mains-voltage high-power grid-tie inverter according to claim 4, characterized in that, The rated power of the inverter is 800W or 1000W, The inductance range of the main transformer T0, T1, T2 and T3 is 2.8uH-3.2uH, and the turns ratio is 3:10-2:7; The DC reverse withstand voltage of the SiC diode D1, D2, D30 and D31 is 1200V, and the continuous forward current IF is 9.5A-15A; The accuracy of the thyristor drive resistor R53 and R55 is 1%, the temperature coefficient is 100ppm / ℃, the rated voltage is 400V, and the resistance value is 150Ω-200Ω; The off-state peak voltage Vdrm of the thyristor D20 and D21 is 800V, and the on-state RMS current It(rms) is 21A-40A; The drain-source voltage of the secondary MOS tube QS1 and QS2 is 650V, and the continuous drain current is 27.8A-32.8A; The maximum switching current of the relay k1 is 15A-20A, and the coil voltage is 12Vdc; The rated voltage of the fuse F2 is 250V, and the rated current is 12.6A-15A; The common mode inductor L1 is MnZn ferrite, Minφ0.81mm 2UEW enameled wire, and the number of turns is 14 turns; the inductance range is 1.5mH-2.8mH; The common mode inductor L2 is amorphous, Minφ1.2mm 2UEW enameled wire, and the number of turns is 13 turns; the inductance range is 4mH-6mH; The common mode inductor L3 is MnZn ferrite Minφ1.2mm 2UEW enameled wire, and the number of turns is 21 turns; the inductance range is 4mH-6mH.
6. The two-path low-mains-voltage high-power grid-tied inverter according to claim 4, characterized in that, The rated power of the inverter is 1200W, The inductance range of the main transformer T0, T1, T2, T3 is 2.8uH-3.2uH, and the turn ratio is 3:10-2:7; The DC reverse withstand voltage of the SiC diode D1, D2, D30, D31 is 1200V, and the continuous forward current IF is 9.5A-15A; The original side MOS tube QP0, QP1, QP2, QP3, QP4, QP5, QP6, QP7 are all N-channel MOS tubes, with maximum drain current Id=35A, drain-source voltage Vds=150V, drain-source resistance Rds(on)=9.5mΩ, and gate-source voltage Vgs≤±20V; The current transformer CT0, CT1, CT2, CT3: L(1-3) inductance value 3mH, minimum DC resistance Min,DCR(1-3):6.5Ω, maximum DC resistance max,DCR(8-7):0.75mΩ, maximum turn ratio max,N1:N2=125:1; The precision of the thyristor drive resistor R53, R55 is 1%, the temperature coefficient is 100ppm / ℃, the rated voltage is 400V, and the resistance value is 150Ω-200Ω; The off-state peak voltage Vdrm of the thyristor D20, D21 is 800V, and the on-state RMS current It(rms) is 40A-80A; The drain-source voltage of the secondary MOS tube QS1 and QS2 is 650V, and the continuous drain current is 49A-78A; The maximum switching current of the relay k1 is 15A-20A, and the coil voltage is 12Vdc; The rated voltage of the fuse F2 is 250V, and the rated current is 15A-20A; The resistance value of the secondary current detection resistor R231, R118, R233, R119 is 20mR; The rated voltage of the pressure sensitive resistor RV1, RV2, RV3, RV4 is 175VAC, the rated power is 99J, and the rated current is 6KA; The common mode inductor L1 is MnZn ferrite, Minφ0.81mm 2UEW enameled wire, and the number of turns is 14 turns; the inductance range is 1.5mH-2.8mH; The common mode inductance L2 is amorphous, Minφ1.2mm 2UEW enameled wire, and the number of turns is 13; the inductance range is 4mH-6mH. The common mode inductance L3 is MnZn ferrite Minφ1.2mm 2UEW enameled wire, and the number of turns is 21; the inductance range is 4mH-6mH.