Micro inverter and photovoltaic system
By using multiple primary H-bridge circuits and single secondary bridge arm circuits in the micro inverter, combined with a polarity inversion circuit composed of diodes and switch tubes, the problem of large size and high cost of the micro inverter is solved, and the effect of cost reduction and volume reduction is achieved.
Patent Information
- Application Number
- CN202420413514.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-04
- Publication Date
- 2025-04-11
- Estimated Expiration
- 2034-03-04
AI Technical Summary
The existing micro inverters are large in size and high in cost, which limits their promotion and application.
Multiple primary H-bridge circuits are used as inputs, single secondary bridge arm circuits and polarity inversion circuits are used as outputs. The polarity inversion circuits are composed of a combination of diodes and switch tubes, and a half-control device diode is used to replace the full-control device to reduce costs.
The cost of micro inverters is effectively reduced. At the same time, due to the use of technologies such as resonant capacitors and insulated gate bipolar transistors, the volume of micro inverters has also been reduced.
Smart Images
Figure CN222750337U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of new energy, and in particular relates to a micro inverter and a photovoltaic system. Background Art
[0002] With the development of new energy power generation technology, the continuous maturity of photovoltaic power generation technology, and the continuous expansion of the application scope of photovoltaic power generation, inverters have gradually developed in the direction of miniaturization and high power density, and micro inverters have therefore emerged.
[0003] The micro inverter may include at least one primary H-bridge circuit and a primary winding, and each primary winding is connected to a corresponding photovoltaic array panel via the primary H-bridge circuit. The micro inverter may be connected to the grid by controlling the internal and external phase shift angles of the primary H-bridge circuit and the secondary bridge arm circuit.
[0004] However, the current micro inverters are large in size and high in cost, which is not conducive to the promotion of micro inverters. Utility Model Content
[0005] The utility model provides a micro inverter, aiming to solve the problem of high cost of micro transformer.
[0006] The utility model is implemented as follows: a micro inverter, the micro inverter comprises a secondary bridge arm circuit, a polarity reversal circuit, a plurality of primary H-bridge circuits and a plurality of transformers, the polarity reversal circuit comprises a first diode, a second diode, a first switch tube and a second switch tube;
[0007] The input ends of the multiple primary H-bridge circuits are connected to the multiple photovoltaic array panels one by one, the output ends of the multiple primary H-bridge circuits are connected to the primary windings of the multiple transformers one by one, and the secondary windings of the respective transformers are connected to the input ends of the secondary bridge arm circuits;
[0008] The positive output end of the secondary bridge arm circuit is connected to the anode of the first diode and the anode of the second diode, the cathode of the first diode and the first end of the first switch tube are connected to one end of the power grid, the cathode of the second diode and the first end of the second switch tube are connected to the other end of the power grid, and the second end of the first switch tube and the second end of the second switch tube are connected to the negative output end of the secondary bridge arm circuit.
[0009] Furthermore, the secondary bridge arm circuit includes a switch bridge arm and a capacitor bridge arm connected in parallel;
[0010] The midpoint of the switch bridge arm is connected to the same-name end of the secondary winding of each transformer, and the midpoint of the capacitor bridge arm is connected to the opposite-name end of the secondary winding of each transformer;
[0011] The first end of the switch bridge arm and the first end of the capacitor bridge arm are the positive output end of the secondary bridge arm circuit, and the second end of the switch bridge arm and the second end of the capacitor bridge arm are the negative output end of the secondary bridge arm circuit.
[0012] Furthermore, the switch bridge arm includes a third switch tube and a fourth switch tube connected in series, and the capacitor bridge arm includes a first resonant capacitor and a second resonant capacitor connected in series.
[0013] Furthermore, the capacitance of the first resonant capacitor is equal to that of the second resonant capacitor.
[0014] Furthermore, the third switch tube and the fourth switch tube are insulated gate bipolar transistors or metal-oxide semiconductor field effect transistors.
[0015] Furthermore, the micro-inverter further includes a plurality of supporting capacitors;
[0016] The multiple supporting capacitors are connected in parallel with the multiple primary H-bridge circuits in a one-to-one correspondence.
[0017] Furthermore, the micro inverter further includes a filter capacitor;
[0018] The filter capacitor is connected between the positive output terminal and the negative output terminal of the secondary bridge arm circuit.
[0019] Furthermore, the micro inverter further includes a plurality of decoupling inductors;
[0020] The multiple decoupling inductors are connected in series with the primary windings of the multiple transformers in a one-to-one correspondence, or the multiple decoupling inductors are connected in series with the secondary windings of the multiple transformers in a one-to-one correspondence, or the decoupling inductors are leakage inductors of the corresponding transformers.
[0021] The utility model also provides a photovoltaic system, characterized in that the photovoltaic system comprises the micro inverter as described in any one of the above items.
[0022] Furthermore, the photovoltaic system further comprises a plurality of photovoltaic array panels;
[0023] The plurality of array boards are connected to the input ends of the plurality of primary H-bridge circuits of the micro inverter in a one-to-one correspondence.
[0024] According to the technical solution of the utility model, the micro inverter adopts a multi-channel primary H-bridge circuit as input, a single secondary bridge arm circuit and a polarity reversal circuit as output, wherein the polarity reversal circuit is composed of a combination of a diode and a switch tube. Since the cost of the diode of the semi-controlled device is low, compared with the fully-controlled device, the technical solution of the present application can effectively reduce the cost of the micro inverter. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 This is a circuit structure diagram of an embodiment of a micro inverter provided by the utility model.
[0026] Figure 2 This is a schematic diagram of the circuit structure of an embodiment of a micro inverter provided by the utility model.
[0027] Figure 3 It is a circuit structure schematic diagram of another embodiment of the micro inverter provided by the utility model. DETAILED DESCRIPTION
[0028] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.
[0029] According to the technical solution of the utility model, the inverter adopts a multi-channel primary H-bridge circuit as input, a single secondary bridge arm circuit and a polarity reversal circuit as output, wherein the polarity reversal circuit is composed of a combination of a diode and a switch tube. Since the cost of the diode of the semi-controlled device is low, compared with the fully controlled device, the technical solution of the present application can effectively reduce the cost of the micro inverter.
[0030] Embodiment 1
[0031] Reference Figure 1 A micro inverter includes a secondary bridge arm circuit 20, a polarity reversal circuit 30, a plurality of primary H-bridge circuits 10 and a plurality of transformers, wherein the polarity reversal circuit 30 includes two bridge arms connected in parallel, each bridge arm is composed of a diode and a switch tube connected in series, such as Figure 1 The polarity reversal circuit 30 shown is composed of a first diode D1, a second diode D2, a first switch tube S1 and a second switch tube S2; wherein, the input ends of the multiple primary H-bridge circuits 10 are connected to the multiple photovoltaic array panels PV1~PVn in a one-to-one correspondence, and the output ends of the multiple primary H-bridge circuits 10 are connected to the primary windings of the multiple transformers in a one-to-one correspondence, and the secondary winding of each transformer is connected to the input end of the secondary bridge arm circuit 20; and the positive output end of the secondary bridge arm circuit 20 is connected to the positive electrode of the first diode D1 and the positive electrode of the second diode D2 of the polarity reversal circuit 30, the negative electrode of the first diode D1 and the first end of the first switch tube S1 are connected to one end of the power grid AC, the negative electrode of the second diode D2 and the first end of the second switch tube S2 are connected to the other end of the power grid AC, and the second end of the first switch tube S1 and the second end of the second switch tube S2 are connected to the negative output end of the secondary bridge arm circuit 20.
[0032] The transformer of the present application is used to achieve electrical isolation between the primary side and the secondary side. The turns ratio of the primary winding to the secondary winding of each transformer is 1:n.
[0033] The polarity reversal circuit 30 is used to convert a 100 Hz half-sine wave into a 50 Hz alternating current. The polarity reversal circuit 30 is composed of a diode and a switch device. Using a diode to replace a full-control device can effectively reduce the cost of the micro inverter.
[0034] Each primary side H-bridge circuit of the micro inverter of the present application is independently configured.
[0035] The micro inverter also includes a plurality of supporting capacitors, which play a role in voltage stabilization. Figure 1 As shown, the micro inverter further includes support capacitors Cbus1 to Cbusn, each of which is connected in parallel with a corresponding photovoltaic array panel, or each of which is connected in parallel with a corresponding primary H-bridge circuit.
[0036] The micro inverter further includes a filter capacitor, which is connected between the positive output terminal and the negative output terminal of the secondary bridge arm circuit 20 to play a filtering and voltage stabilizing role.
[0037] The micro inverter also includes a plurality of decoupling inductors, which can be connected in series with the primary windings of the plurality of transformers one by one, or can be connected in series with the secondary windings of the plurality of transformers one by one. Furthermore, the decoupling inductors can be physical inductors or leakage inductors of transformers.
[0038] In order to facilitate understanding of the technical concept of the present application, the following description is made by taking an example where the number of photovoltaic array panels, the number of primary H-bridge circuits and the number of transformers are two respectively.
[0039] Embodiment 2
[0040] Reference Figure 2 The micro inverter includes a secondary bridge arm circuit, a polarity reversal circuit, a first primary H-bridge circuit, a second primary H-bridge circuit, a first supporting capacitor Cbus1, a second supporting capacitor Cbus2, and a filter capacitor C3.
[0041] The first primary H-bridge circuit includes switch tubes SS1, SS2, SS3 and SS4. The midpoints of switch tubes SS1 and SS2 are connected to the same-name ends of the primary windings of the corresponding transformers; the midpoints of switch tubes SS3 and SS4 are connected to the opposite-name ends of the primary windings of the corresponding transformers.
[0042] The second primary H-bridge circuit includes switch tubes SS5, SS6, SS7 and SS8. The midpoints of switch tubes SS5 and SS6 are connected to the same-name ends of the primary windings of the corresponding transformers; the midpoints of switch tubes SS7 and SS8 are connected to the opposite-name ends of the primary windings of the corresponding transformers.
[0043] The first supporting capacitor Cbus1 is connected in parallel with the first photovoltaic array panel PV1 , and the second supporting capacitor Cbus2 is connected in parallel with the second photovoltaic array panel PV2 .
[0044] The secondary bridge arm circuit includes a switch bridge arm and a capacitor bridge arm in parallel. The switch bridge arm is formed by two switch tubes in series, and the capacitor bridge arm is formed by two resonant capacitors in series. The two resonant capacitors have the same capacitance. By utilizing the small size of the resonant capacitor, the size of the micro inverter can be effectively reduced.
[0045] The polarity reversal circuit includes a first diode D1, a second diode D2, a first switch tube S1 and a second switch tube S2.
[0046] Among them, the midpoint of the switch bridge arm of the secondary bridge arm circuit is connected to the same-name end of the secondary winding of each transformer, and the midpoint of the capacitor bridge arm is connected to the opposite-name end of the secondary winding of each transformer; the first end of the switch bridge arm and the first end of the capacitor bridge arm are the positive output end of the secondary bridge arm circuit 20, connected to the positive electrode of the first diode D1 and the positive electrode of the second diode D2 of the polarity reversal circuit 30, and the second end of the switch bridge arm and the second end of the capacitor bridge arm are the negative output end of the secondary bridge arm circuit, connected to the second end of the first switch tube S1 and the second end of the second switch tube S2 of the polarity reversal circuit 30. The cathode of the first diode D1 of the polarity reversal circuit 30 and the first end of the first switch tube S1 are connected to one end of the power grid AC, and the cathode of the second diode D2 and the first end of the second switch tube S2 are connected to the other end of the power grid AC. The filter capacitor C3 is connected between the positive output end and the negative output end of the secondary bridge arm circuit 20.
[0047] The third switch tube and the fourth switch tube of the secondary bridge arm circuit 20 may be insulated gate bipolar transistors or metal-oxide semiconductor field effect transistors, and may be specifically configured according to actual needs.
[0048] The switch tube in the switch bridge arm of the polarity reversal circuit 30 may be an insulated gate bipolar transistor or a metal-oxide semiconductor field effect transistor, and may be specifically configured according to actual needs.
[0049] It can be understood that the technical solution of the present application is also applicable to single-stage micro-inverters, such as Figure 3 The single-stage micro inverter shown includes a single photovoltaic array panel, a single primary H-bridge circuit, a single transformer, a secondary bridge arm circuit, and a polarity reversal circuit.
[0050] This application detects the grid-side voltage and the current flowing through the inductor, and obtains the expression of the inductor current based on the grid-side voltage, frequency and phase shift angle according to the corresponding formula. Then, closed-loop control is performed based on the inductor current to achieve variable frequency control, which can reduce current stress and power loss in the process; and the topology can be used to detect the current zero point to achieve the control of the primary and secondary duty cycles; and the addition of the resonant cavity in this application can make the waveform of the inductor current tend to be a sine wave, thereby reducing the resonance distortion rate and improving the efficiency of the micro inverter.
[0051] Furthermore, the capacitor bridge arm of the secondary bridge arm circuit of the micro-inverter of the present application is composed of two resonant capacitors connected in series. The small size of the resonant capacitor can be used to effectively reduce the size of the micro-inverter; and the polarity reversal circuit of the micro-inverter is composed of a combination of a diode and a switch tube. The semi-controlled device diode is used to replace the fully controlled device, which can effectively reduce the cost of the micro-inverter. With this arrangement, the micro-inverter of the present application has the advantages of small size and low cost.
[0052] The utility model also provides a photovoltaic system, which includes a micro-inverter as described in any of the above items. The detailed structure of the micro-inverter can refer to the above embodiment, which will not be repeated here; it can be understood that since the above micro-inverter is used in the photovoltaic system of the utility model, the embodiment of the photovoltaic system of the utility model includes all technical solutions of all embodiments of the above micro-inverter, and the technical effects achieved are also exactly the same, which will not be repeated here.
[0053] The photovoltaic system also includes a plurality of photovoltaic array panels; the plurality of array panels are connected to the input ends of the plurality of primary H-bridge circuits of the micro-inverter in a one-to-one correspondence.
[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A micro inverter, characterized in that: The micro inverter includes a secondary bridge arm circuit, a polarity reversal circuit, a plurality of primary H-bridge circuits and a plurality of transformers, and the polarity reversal circuit includes a first diode, a second diode, a first switch tube and a second switch tube; The input ends of the multiple primary H-bridge circuits are connected to the multiple photovoltaic array panels one by one, the output ends of the multiple primary H-bridge circuits are connected to the primary windings of the multiple transformers one by one, and the secondary windings of the respective transformers are connected to the input ends of the secondary bridge arm circuits; The positive output end of the secondary bridge arm circuit is connected to the anode of the first diode and the anode of the second diode, the cathode of the first diode and the first end of the first switch tube are connected to one end of the power grid, the cathode of the second diode and the first end of the second switch tube are connected to the other end of the power grid, and the second end of the first switch tube and the second end of the second switch tube are connected to the negative output end of the secondary bridge arm circuit.
2. The micro inverter according to claim 1, characterized in that: The secondary bridge arm circuit comprises a switch bridge arm and a capacitor bridge arm connected in parallel; The midpoint of the switch bridge arm is connected to the same-name end of the secondary winding of each transformer, and the midpoint of the capacitor bridge arm is connected to the opposite-name end of the secondary winding of each transformer; The first end of the switch bridge arm and the first end of the capacitor bridge arm are the positive output end of the secondary bridge arm circuit, and the second end of the switch bridge arm and the second end of the capacitor bridge arm are the negative output end of the secondary bridge arm circuit.
3. The micro inverter according to claim 2, characterized in that: The switch bridge arm includes a third switch tube and a fourth switch tube connected in series, and the capacitor bridge arm includes a first resonant capacitor and a second resonant capacitor connected in series.
4. The micro inverter according to claim 3, characterized in that: The capacitance of the first resonant capacitor is equal to that of the second resonant capacitor.
5. The micro inverter according to claim 3, characterized in that: The third switch tube and the fourth switch tube are insulated gate bipolar transistors or metal-oxide semiconductor field effect transistors.
6. The micro inverter according to claim 1, characterized in that: The micro-inverter also includes a plurality of supporting capacitors; The multiple supporting capacitors are connected in parallel with the multiple primary H-bridge circuits in a one-to-one correspondence.
7. The micro inverter according to claim 1, characterized in that: The micro inverter also includes a filter capacitor; The filter capacitor is connected between the positive output terminal and the negative output terminal of the secondary bridge arm circuit.
8. The micro inverter according to any one of claims 1 to 7, characterized in that: The micro inverter further includes a plurality of decoupling inductors; The multiple decoupling inductors are connected in series with the primary windings of the multiple transformers in a one-to-one correspondence, or the multiple decoupling inductors are connected in series with the secondary windings of the multiple transformers in a one-to-one correspondence, or the decoupling inductors are leakage inductors of the corresponding transformers.
9. A photovoltaic system, characterized in that: The photovoltaic system comprises the micro-inverter according to any one of claims 1-8.
10. The photovoltaic system according to claim 9, characterized in that: The photovoltaic system also includes a plurality of photovoltaic array panels; The plurality of array boards are connected to the input ends of the plurality of primary H-bridge circuits of the micro inverter in a one-to-one correspondence.