Multi-input micro-inverter circuit system and its operation control method

Abstract

The application provides a multi-input micro inverter circuit system and a running control method thereof. The system comprises a multi-path DC side circuit, a switch device corresponding to the DC side circuit, and a secondary side bridge arm circuit. The switch device is arranged on a circuit between the secondary side bridge arm circuit and a capacitor in the DC side circuit. When a first DC side circuit in the multi-path DC side circuit and a corresponding photovoltaic module are connected to the secondary side bridge arm circuit, the switch device corresponding to the first DC side circuit is closed, and the switch device corresponding to a second DC side circuit is disconnected, so as to interrupt a path through which the secondary side bridge arm circuit charges the capacitor in the second DC side circuit. The second DC side circuit is a DC side circuit in the multi-path DC side circuit which is not connected to the secondary side bridge arm circuit. In this way, the DC side circuit which is not connected to the secondary side bridge arm circuit is effectively disconnected from the grid-connected circuit and the secondary side bridge arm circuit, and the risk of damage to components in the DC side circuit which is not connected is eliminated.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, and in particular to a multi-input micro inverter circuit system and its operation control method. Background Technology

[0002] The microinverter topology includes a primary-side bridge arm circuit, a high-voltage frequency converter, and a secondary-side bridge arm circuit. The DC-side circuit, consisting of the primary-side bridge arm circuit and a high-frequency transformer, connects to the photovoltaic (PV) modules, while the secondary-side bridge arm circuit connects to the power grid. The DC-side circuit comprises multiple paths, each connecting to a different PV module. These multiple DC-side circuits share a single secondary-side bridge arm circuit. When one PV module and its corresponding DC-side circuit are connected to the secondary-side bridge arm circuit, while other PV modules and their corresponding DC-side circuits are not connected, a square wave voltage is generated on the unconnected DC-side circuits because they share a single secondary-side bridge arm circuit. This voltage charges the capacitors in the primary-side bridge arm circuits of the unconnected DC-side circuits, and the charging voltage is relatively high, making the components in the unconnected primary-side bridge arm circuits susceptible to overvoltage damage. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a multi-input micro inverter circuit system and its operation control method, so as to avoid the capacitor in the primary side bridge arm circuit of the unconnected DC side circuit being charged when multiple DC side circuits share a single secondary side bridge arm circuit, thereby eliminating the risk of damage to the components in the unconnected primary side bridge arm circuit.

[0004] In a first aspect, embodiments of the present invention provide a multi-input micro-inverter circuit system, comprising: multiple DC-side circuits, switching devices corresponding to the DC-side circuits, and secondary bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary bridge arm circuits are connected to the power grid; all multiple DC-side circuits are connected to the secondary bridge arm circuits; the switching devices are disposed on the circuit between the capacitors in the secondary bridge arm circuits and the DC-side circuits; when the first DC-side circuit and the corresponding photovoltaic module in the multiple DC-side circuits are connected to the secondary bridge arm circuit, the switching device corresponding to the first DC-side circuit is closed, and the switching device corresponding to the second DC-side circuit is opened, thereby interrupting the charging path from the secondary bridge arm circuit to the capacitor in the second DC-side circuit; wherein, the second DC-side circuit is the DC-side circuit in the multiple DC-side circuits that is not connected to the secondary bridge arm circuit.

[0005] Furthermore, the aforementioned switching device is located between the secondary bridge arm circuit and the DC side circuit.

[0006] Furthermore, the aforementioned DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer, which is connected to the input terminal of the secondary-side bridge arm circuit via an inductor; a switching device is disposed between the secondary-side bridge arm circuit and the inductor.

[0007] Furthermore, the aforementioned DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the switching device is located between the secondary-side bridge arm circuit and the high-frequency transformer.

[0008] Furthermore, the aforementioned switching device is located at a designated position within the DC-side circuit.

[0009] Furthermore, the aforementioned DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; the switching device is located between the leading bridge arm and the high-frequency transformer.

[0010] Furthermore, the aforementioned DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; the switching device is located between the lagging bridge arm and the high-frequency transformer.

[0011] Furthermore, the aforementioned DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a capacitor, a leading bridge arm, and a lagging bridge arm connected in parallel; the switching device is disposed between the capacitor and the leading bridge arm, or between the capacitor and the lagging bridge arm.

[0012] Furthermore, when the first DC-side circuit and the corresponding photovoltaic module are connected to the secondary side bridge arm circuit, the capacitor voltage in the second DC-side circuit is zero, and the voltage of the primary side bridge arm circuit in the second DC-side circuit is zero.

[0013] Secondly, embodiments of the present invention provide an operation control method for a multi-input micro-inverter circuit system. This method is applied to a multi-input micro-inverter circuit system. The system includes multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary bridge arm circuits. The DC-side circuits are connected to corresponding photovoltaic modules. The secondary bridge arm circuits are connected to the power grid. All multiple DC-side circuits are connected to the secondary bridge arm circuits. The switching devices are located in the circuit between the capacitors in the secondary bridge arm circuits and the DC-side circuits. The method includes: acquiring the DC-side voltage of the multiple DC-side circuits; determining the first DC-side circuit connected to the secondary bridge arm circuit based on the DC-side voltage; controlling the switching device corresponding to the first DC-side circuit to close, and controlling the switching device corresponding to the second DC-side circuit to open, thereby interrupting the charging path from the secondary bridge arm circuit to the capacitor in the second DC-side circuit; wherein the second DC-side circuit is the DC-side circuit among the multiple DC-side circuits that is not connected to the secondary bridge arm circuit.

[0014] Furthermore, the step of determining the first DC-side circuit connected to the secondary bridge arm circuit based on the DC-side voltage includes: determining whether the DC-side voltage of each DC-side circuit is greater than a preset voltage threshold; and determining the DC-side circuit with a DC-side voltage greater than the preset voltage threshold as the first DC-side circuit connected to the secondary bridge arm circuit.

[0015] The above method also includes: identifying DC-side circuits with DC-side voltages less than or equal to a preset voltage threshold as the second DC-side circuit not connected to the secondary bridge arm circuit.

[0016] The embodiments of the present invention bring the following beneficial effects:

[0017] The aforementioned multi-input micro-inverter circuit system and its operation control method include: multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary bridge arm circuits are connected to the power grid; all multiple DC-side circuits are connected to the secondary bridge arm circuits; the switching devices are located on the circuit between the capacitors in the secondary bridge arm circuits and the DC-side circuits; when the first DC-side circuit and the corresponding photovoltaic module in the multiple DC-side circuits are connected to the secondary bridge arm circuit, the switching device corresponding to the first DC-side circuit is closed, and the switching device corresponding to the second DC-side circuit is opened to interrupt the charging path from the secondary bridge arm circuit to the capacitor in the second DC-side circuit; wherein, the second DC-side circuit is the DC-side circuit in the multiple DC-side circuits that is not connected to the secondary bridge arm circuit. In this method, in a multi-input micro-inverter circuit system, by adding a switching device to the circuit between the capacitors in the secondary bridge arm circuit and the DC side circuit, the DC side circuit not connected to the photovoltaic modules is effectively disconnected from the grid circuit and the secondary bridge arm circuit. This avoids the secondary bridge arm circuit charging the capacitors in the DC side circuit not connected to the photovoltaic modules, and eliminates the risk of damage to the components in the DC side circuit not connected to the photovoltaic modules.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram of a single-stage micro inverter topology provided in an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a single-stage dual-path micro-inverter topology provided in an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of a multi-input micro inverter circuit system provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a micro inverter topology with a switching device between the secondary bridge arm circuit and the inductor provided in an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of a micro inverter topology with a switching device between the secondary bridge arm circuit and the high-frequency transformer provided in an embodiment of the present invention;

[0026] Figure 6 A schematic diagram of a micro inverter topology with a switching device between the lead bridge arm and the high-frequency transformer provided in an embodiment of the present invention;

[0027] Figure 7 A schematic diagram of a micro-inverter topology with a switching device between a hysteresis arm and a high-frequency transformer, provided in an embodiment of the present invention;

[0028] Figure 8 A schematic diagram of a micro inverter topology with a switching device disposed between a capacitor and a lead-up arm, provided by an embodiment of the present invention;

[0029] Figure 9 A schematic diagram of another micro-inverter topology provided in an embodiment of the present invention, in which a switching device is disposed between a capacitor and a hysteresis arm;

[0030] Figure 10 A flowchart illustrating an operation control method for a multi-input micro inverter circuit system provided in an embodiment of the present invention;

[0031] Figure 11 A flowchart of another operation control method for a multi-input micro inverter circuit system provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The micro-inverter topology includes a primary-side bridge arm circuit, a high-voltage frequency converter, and a secondary-side bridge arm circuit. The DC-side circuit, consisting of the primary-side bridge arm circuit and the high-frequency transformer, connects to the photovoltaic modules, while the secondary-side bridge arm circuit connects to the power grid. The DC-side circuit can be one or more circuits.

[0034] Figure 1 A single-stage microinverter topology is provided. This microinverter has one DC-side circuit. The primary-side bridge arm circuit of the DC-side circuit adopts an H-bridge circuit, and the secondary-side bridge arm circuit adopts a bidirectional switching circuit. A high-frequency transformer is used to achieve voltage boost and primary-secondary isolation. The output terminal of the secondary-side bridge arm circuit serves as the output terminal of the microinverter, which is connected to the power grid through a filter. The bidirectional switches corresponding to the secondary-side bridge arm circuit in the microinverter, namely S5 and S6, constitute the upper half-bridge arm bidirectional switch, and S7 and S8 constitute the lower half-bridge arm bidirectional switch. When the grid voltage is greater than zero, the secondary-side switches operate in mode one: S5 and S7 act as high-frequency transistors for high-frequency chopping, while S6 and S8 are directly connected. When the grid voltage is less than zero, the secondary-side switches operate in mode two: S6 and S8 act as high-frequency transistors for high-frequency chopping, while S5 and S7 are directly connected.

[0035] The aforementioned microinverter can achieve single-stage grid connection by controlling the outward phase shift angle and the inward phase shift angle of the primary and secondary bridge arms. Here, there are two degrees of freedom: the inward phase shift angle D1 between the two primary bridge arms, and the outward phase shift angle D2 between the primary and secondary bridge arms. Energy transfer can be achieved by controlling D1 and D2. D1 is defined as the angle by which transistor S4 lags transistor S1, and D2 is defined as the angle by which transistors S5 (S8) lag transistor S1.

[0036] In a multi-input micro-inverter, multiple DC-side circuits share a single secondary bridge arm circuit. For example, Figure 2 A single-stage dual-path micro-inverter topology is provided. The micro-inverter has two DC-side circuits and is a one-to-two micro-inverter topology. The secondary-side bridge arm circuit of the micro-inverter is composed of a set of bidirectional switches and capacitor bridge arms.

[0037] When photovoltaic module 1 is connected normally, but photovoltaic module 2 is not connected normally, the DC-side circuit connected to photovoltaic module 1 is the first DC-side circuit, and the DC-side circuit corresponding to photovoltaic module 2 is the second DC-side circuit. Since they share the secondary bidirectional switching bridge arm and output filter, even though photovoltaic module 2 is not connected, the secondary voltage of the high-frequency transformer in the second DC-side circuit is the same as the secondary voltage of the high-frequency transformer in the first DC-side circuit, and they are constantly being chopped. In this case, the transformer in the second DC-side circuit will generate a corresponding square wave voltage in its primary bridge arm circuit, and charge the primary capacitor in its circuit through the diode of the primary bridge arm of the second DC-side circuit. The voltage will be pushed up relatively high, which can easily cause overvoltage damage to the components in the primary bridge arm circuit of the second DC-side circuit.

[0038] To address this issue, in multi-input micro-inverter circuits, the input voltage of the unconnected circuits can be controlled to ensure it does not exceed a specified voltage, thereby protecting the unconnected switching transistors and primary-side capacitors from overvoltage damage. However, this method still results in voltage at the unconnected PV (Photovoltaic) ports, and controlling this voltage requires certain resource consumption.

[0039] To address the aforementioned issues, this invention provides a multi-input micro inverter circuit system and its operation control method, which relates to the field of circuit technology.

[0040] To facilitate understanding of this embodiment, a multi-input micro inverter circuit system disclosed in this embodiment of the invention will first be described in detail.

[0041] Figure 3 The diagram shows a schematic of a multi-input micro-inverter circuit system disclosed in this embodiment. The system includes: multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary bridge arm circuits are connected to the power grid; and all multiple DC-side circuits are connected to the secondary bridge arm circuits.

[0042] The switching device in this micro-inverter circuit system is located on the circuit between the secondary bridge arm circuit and the capacitor in the DC side circuit. When the first DC side circuit and the corresponding photovoltaic module in the multiple DC side circuits are connected to the secondary bridge arm circuit, the switching device corresponding to the first DC side circuit is closed, and the switching device corresponding to the second DC side circuit is opened to interrupt the charging path from the secondary bridge arm circuit to the capacitor in the second DC side circuit. The second DC side circuit is the DC side circuit in the multiple DC side circuits that is not connected to the secondary bridge arm circuit.

[0043] The aforementioned photovoltaic module serves as a DC power source, connected to the input terminal of the DC-side circuit. This DC-side circuit includes capacitors and other circuit components, including a primary-side bridge arm circuit and a high-frequency transformer. The primary-side bridge arm circuit can be an H-bridge circuit, containing a switching transistor. This primary-side bridge arm circuit is connected to the high-frequency transformer, which provides voltage boost and primary-secondary isolation. The aforementioned secondary-side bridge arm circuit can be a bidirectional switching circuit, containing a switching transistor and a capacitor.

[0044] The aforementioned first DC-side circuit is the one among the multiple DC-side circuits that can currently perform DC-to-AC conversion. This first DC-side circuit is normally connected to the photovoltaic modules and can achieve grid connection by controlling the outward phase shift angle of the primary and secondary bridge arm circuits and the inward phase shift angle of the primary bridge arm. The aforementioned second DC-side circuit is the DC-side circuit among the multiple DC-side circuits that is not connected to the secondary bridge arm circuit.

[0045] A DC-side circuit not connected to the secondary bridge arm circuit can be understood as a DC-side circuit that does not need to form a path with the secondary bridge arm circuit to perform DC-to-AC conversion among multiple DC-side circuits. This second DC-side circuit is not connected to a DC source; for example, it is not properly connected to the photovoltaic module or the photovoltaic module is completely shaded and cannot work. In this case, the second DC-side circuit is considered a DC-side circuit not connected to the secondary bridge arm circuit.

[0046] The aforementioned switching device is used to control the on / off state of the second DC-side circuit, the first DC-side circuit, and the secondary bridge arm circuit. It should be noted that in the aforementioned micro-inverter circuit system, there can be one or more first and second DC-side circuits, and each DC-side circuit can be equipped with a corresponding switching device.

[0047] Here, the multi-input microinverter circuit system includes: multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary-side bridge arm circuits. The input terminals of the DC-side circuits are connected to the corresponding photovoltaic modules, and the output terminals of the DC-side circuits are connected to the secondary-side bridge arm circuits. The output terminals of each DC-side circuit are connected to the secondary-side bridge arm circuits, and the output terminals of the secondary-side bridge arm circuits are connected to the power grid. The switching devices are located in the circuit between the capacitors in the secondary-side bridge arm circuits and the DC-side circuits. These switching devices can be located in the circuit between the capacitors and other circuit components in the DC-side circuits, in the circuit of other circuit components, or in the circuit between the DC-side circuits and the secondary-side bridge arm circuits. The number of switching devices is unlimited.

[0048] When the DC-side circuit is normally connected to the photovoltaic modules, and grid connection can be achieved by controlling the outward phase shift angle of the primary-side bridge arm circuit and the inward phase shift angle of the primary-side bridge arm circuit, this DC-side circuit is the first DC-side circuit. When the DC-side circuit is not connected to a DC source, for example, if it is not normally connected to the photovoltaic modules or the photovoltaic modules are completely shaded and cannot work, this DC-side circuit is the second DC-side circuit, which is not connected to the secondary-side bridge arm circuit.

[0049] Here, when the first DC-side circuit and the corresponding photovoltaic module in the multi-channel DC-side circuit are connected to the secondary-side bridge arm circuit, closing the switch device corresponding to the first DC-side circuit and opening the switch device corresponding to the second DC-side circuit can disconnect the line through which the secondary-side voltage is coupled to the primary-side voltage of the second DC-side circuit and charges the primary-side capacitor of the second DC-side circuit through the primary-side H-bridge, that is, interrupt the path of the secondary-side bridge arm circuit to charge the capacitor in the second DC-side circuit.

[0050] This method avoids charging the capacitors in the unconnected DC side circuit from the secondary bridge arm circuit, eliminating the risk of damage to components in the unconnected DC side circuit, as well as the risk of damage to components in the unconnected primary bridge arm circuit.

[0051] The aforementioned multi-input micro-inverter circuit system includes: multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary bridge arm circuits are connected to the power grid; all multiple DC-side circuits are connected to the secondary bridge arm circuits; the switching devices are located in the circuit between the capacitors in the secondary bridge arm circuits and the DC-side circuits; when the first DC-side circuit and the corresponding photovoltaic module in the multiple DC-side circuits are connected to the secondary bridge arm circuit, the switching device corresponding to the first DC-side circuit is closed, and the switching device corresponding to the second DC-side circuit is opened, thereby interrupting the charging path from the secondary bridge arm circuit to the capacitor in the second DC-side circuit; wherein, the second DC-side circuit is the DC-side circuit in the multiple DC-side circuits that is not connected to the secondary bridge arm circuit. In this method, in a multi-input micro-inverter circuit system, by adding a switching device to the circuit between the capacitors in the secondary bridge arm circuit and the DC side circuit, the DC side circuit not connected to the secondary bridge arm circuit is effectively disconnected from the grid circuit and the secondary bridge arm circuit. This avoids the secondary bridge arm circuit charging the capacitors in the unconnected DC side circuit and eliminates the risk of damage to the components in the unconnected DC side circuit.

[0052] In one embodiment, the switching device is located between the secondary bridge arm circuit and the DC side circuit.

[0053] Here, the DC side circuit also includes the primary side bridge arm circuit and the high-frequency transformer. The primary side bridge arm circuit is connected to the high-frequency transformer, and the high-frequency transformer can be connected to the secondary side bridge arm circuit through an inductor. The switching device is located between the secondary side bridge arm circuit and the DC side circuit.

[0054] In one embodiment, the DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer, the high-frequency transformer being connected to the input terminal of the secondary-side bridge arm circuit via an inductor; a switching device is disposed between the secondary-side bridge arm circuit and the inductor.

[0055] The primary side bridge arm circuit described above can be an H-bridge circuit, while the secondary side bridge arm circuit uses a bidirectional switching circuit. The secondary side bridge arm circuit includes a bidirectional switch and a capacitor bridge arm.

[0056] For example, taking a one-to-two micro-inverter topology as an example, the topology of a micro-inverter is as follows: Figure 4 As shown, the primary side bridge arm of the DC-side circuit adopts an H-bridge circuit. Each H-bridge circuit includes four switching transistors. The primary side bridge arm circuit is connected to the high-frequency transformer, which is connected to the high-frequency transformer through an inductor L. k The input terminal of the secondary bridge arm circuit is connected, and the output terminal of the secondary bridge arm circuit is connected to the power grid through a filter.

[0057] When photovoltaic module 1 is connected and photovoltaic module 2 is not properly connected, the DC-side circuit connected to photovoltaic module 1 is the first DC-side circuit, and the DC-side circuit corresponding to photovoltaic module 2 is the second DC-side circuit. Scut1 and Scut2 are the switching devices corresponding to the first DC-side circuit and the second DC-side circuit, respectively, and the switching devices are located between the secondary bridge arm circuit and the inductor. By executing the operation of closing Scut1 and opening Scut2, the high-frequency transformer of the primary H-bridge of the second DC-side circuit and the bidirectional switch of the first DC-side circuit are disconnected from the secondary bridge arm circuit, interrupting the influence of the secondary voltage on the second DC-side circuit when the first DC-side circuit is connected to the grid.

[0058] Of course, once photovoltaic module 2 is connected, Scut2 can be closed to ensure that the second DC side circuit can operate normally after the photovoltaic module.

[0059] Without loss of generality, when there are more DC-side circuits, each DC-side circuit can be equipped with a switching device. Assuming there are n DC-side circuits, n switching devices need to be added, named Scut1, Scut2, ..., Scutn respectively.

[0060] In another embodiment, the DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the switching device is disposed between the secondary-side bridge arm circuit and the high-frequency transformer.

[0061] For example, taking a one-to-two micro-inverter topology as an example, the topology of a micro-inverter is as follows: Figure 5As shown, the primary side bridge arm circuit adopts an H-bridge circuit, and the secondary side bridge arm circuit adopts a bidirectional switching circuit, which includes a bidirectional switch and a capacitor bridge arm. The output of the secondary side bridge arm circuit is connected to the power grid through a filter.

[0062] When the DC side circuit of the primary H-bridge 1 in the diagram is normally connected to the photovoltaic module, and the DC side circuit of the primary H-bridge 2 is not normally connected to the photovoltaic module, the DC side circuit corresponding to the primary H-bridge 1 is the first DC side circuit, and the DC side circuit corresponding to the primary H-bridge 2 is the second DC side circuit. Scut1 and Scut2 are the switching devices corresponding to the first DC side circuit and the second DC side circuit, respectively. The switching device is located between the secondary bridge arm circuit and the high-frequency transformer, that is, on the lower side of the secondary bridge arm circuit. By executing the operation of closing Scut1 and opening Scut2, the bidirectional switch between the primary H-bridge of the second DC side circuit and the high-frequency transformer of the first DC side circuit, as well as the secondary bridge arm circuit, can be disconnected, interrupting the influence of the secondary voltage on the second DC side circuit when the first DC side circuit is connected to the grid.

[0063] Of course, after the photovoltaic module 2 is connected to the second DC side circuit, Scut2 can be closed to ensure that the second DC side circuit can be connected to the grid normally after the photovoltaic module.

[0064] Without loss of generality, when there are more DC-side circuits, each DC-side circuit can be equipped with a switching device. Assuming there are n DC-side circuits, n switching devices need to be added, named Scut1, Scut2, ..., Scutn respectively.

[0065] In one configuration, the switching device is located at a designated position within the DC-side circuit.

[0066] The specified location is between the primary arm of the DC-side circuit and the high-frequency transformer, or between the capacitor of the DC-side circuit and the primary arm.

[0067] In one embodiment, the DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; and a switching device is disposed between the leading bridge arm and the high-frequency transformer.

[0068] For example, taking a one-to-two micro-inverter topology as an example, the topology of a micro-inverter is as follows: Figure 6 As shown, the primary side bridge arm of the DC-side circuit adopts an H-bridge circuit. Each H-bridge circuit includes four switching transistors: S1 and S4. S1 and S2 form the leading bridge arm, and S3 and S4 are connected in series to form the lagging bridge arm. The leading and lagging bridge arms are connected in parallel. The primary side bridge arm circuit is connected to the high-frequency transformer, which is connected through an inductor L. kThe input terminal of the secondary bridge arm circuit is connected. The secondary bridge arm circuit adopts a bidirectional switching circuit, which includes a bidirectional switch and a capacitor bridge arm. The output terminal of the secondary bridge arm circuit is connected to the power grid through a filter.

[0069] When photovoltaic module 1 is connected and photovoltaic module 2 is not properly connected, the DC-side circuit connected to photovoltaic module 1 is the first DC-side circuit, and the DC-side circuit corresponding to photovoltaic module 2 is the second DC-side circuit. Scut1 and Scut2 are the switching devices corresponding to the first DC-side circuit and the second DC-side circuit, respectively. The switching devices are located between S1 and the high-frequency transformer, that is, on the upper side of the primary-side bridge arm circuit. By executing the operation of closing Scut1 and opening Scut2, the bidirectional switch between the primary-side H-bridge of the second DC-side circuit and the high-frequency transformer of the first DC-side circuit, as well as the secondary-side bridge arm circuit, can be disconnected, interrupting the influence of the secondary-side voltage on the second DC-side circuit when the first DC-side circuit is connected to the grid.

[0070] Of course, after the photovoltaic module 2 is connected to the second DC side circuit, Scut2 can be closed to ensure that the second DC side circuit can be connected to the grid normally after the photovoltaic module.

[0071] Without loss of generality, when there are more DC-side circuits, each DC-side circuit can be equipped with a switching device. Assuming there are n circuits, n switching devices need to be added, named Scut1, Scut2, ..., Scutn respectively.

[0072] In another embodiment, the DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; the switching device is disposed between the lagging bridge arm and the high-frequency transformer.

[0073] For example, taking a one-to-two micro-inverter topology as an example, the topology of a micro-inverter is as follows: Figure 7 As shown, the primary side bridge arm of the DC-side circuit adopts an H-bridge circuit. Each H-bridge circuit includes four switching transistors: S1 and S4. S1 and S2 form the leading bridge arm, and S3 and S4 are connected in series to form the lagging bridge arm. The leading and lagging bridge arms are connected in parallel. The primary side bridge arm circuit is connected to the high-frequency transformer, which is connected through an inductor L. k The input terminal of the secondary bridge arm circuit is connected, and the output terminal of the secondary bridge arm circuit is connected to the power grid through a filter.

[0074] When photovoltaic module 1 is connected and photovoltaic module 2 is not properly connected, the DC-side circuit connected to photovoltaic module 1 is the first DC-side circuit, and the DC-side circuit corresponding to photovoltaic module 2 is the second DC-side circuit. Scut1 and Scut2 are the switching devices corresponding to the first and second DC-side circuits, respectively. The switching devices are located between S4 and the high-frequency transformer, that is, on the lower side of the primary-side bridge arm circuit. By executing the operation of closing Scut1 and opening Scut2, the bidirectional switch between the primary-side H-bridge of the second DC-side circuit and the high-frequency transformer of the first DC-side circuit, as well as the secondary-side bridge arm circuit, can be disconnected, interrupting the influence of the secondary-side voltage on the second DC-side circuit when the first DC-side circuit is connected to the grid.

[0075] Of course, after the photovoltaic module 2 is connected to the second DC side circuit, Scut2 can be closed to ensure that the second DC side circuit can be connected to the grid normally after the photovoltaic module.

[0076] Without loss of generality, when there are more DC-side circuits, each DC-side circuit can be equipped with a switching device. Assuming there are n circuits, n switching devices need to be added, named Scut1, Scut2, ..., Scutn respectively.

[0077] Another approach is that the DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a capacitor, a leading bridge arm, and a lagging bridge arm connected in parallel; the switching device is located between the capacitor and the leading bridge arm, or between the capacitor and the lagging bridge arm.

[0078] The aforementioned switching device can be located between the capacitor and the leading arm, or between the capacitor and the lagging arm.

[0079] For example, taking a one-to-two micro-inverter topology as an example, the topology of a micro-inverter is as follows: Figure 8 As shown, the primary side bridge arm of the DC-side circuit adopts an H-bridge circuit. Each H-bridge circuit includes four switching transistors: S1 and S4. S1 and S2 form the leading bridge arm, and S3 and S4 are connected in series to form the lagging bridge arm. The leading and lagging bridge arms are connected in parallel. The primary side bridge arm circuit is connected to the high-frequency transformer, which is connected through an inductor L. k The input terminal of the secondary bridge arm circuit is connected, and the output terminal of the secondary bridge arm circuit is connected to the power grid through a filter.

[0080] When photovoltaic module 1 is connected and photovoltaic module 2 is not properly connected, the DC-side circuit connected to photovoltaic module 1 is the first DC-side circuit, and the DC-side circuit corresponding to photovoltaic module 2 is the second DC-side circuit. Scut1 and Scut2 are the switching devices corresponding to the first and second DC-side circuits, respectively. The switching devices are located between S1 and the capacitor in the DC-side circuit, as shown in the figure. The switching devices are placed between the capacitor and the upper connection circuit of the primary side bridge arm. By executing the operation of closing Scut1 and opening Scut2, the bidirectional switch between the primary H-bridge of the second DC-side circuit and the high-frequency transformer of the first DC-side circuit, as well as the secondary side bridge arm circuit, can be disconnected, interrupting the influence of the secondary side voltage on the second DC-side circuit when the first DC-side circuit is connected to the grid.

[0081] In another example, such as Figure 9 As shown, the switching device can also be located between the capacitor and the hysteresis bridge arm, that is, the lower connection circuit between the capacitor and the primary side bridge arm in the figure. By executing the Scut1 closing and Scut2 opening operation, the bidirectional switch between the primary side H bridge of the second DC side circuit and the transformer of the first DC side circuit, as well as the secondary side bridge arm circuit, can be disconnected, interrupting the influence of the secondary side voltage on the second DC side circuit when the first DC side circuit is connected to the grid.

[0082] Of course, after the photovoltaic module 2 is connected to the second DC side circuit, Scut2 can be closed to ensure that the second DC side circuit can be connected to the grid normally after the photovoltaic module.

[0083] Without loss of generality, when there are more DC-side circuits, each DC-side circuit can be equipped with a switching device. Assuming there are n DC-side circuits, n switching devices need to be added, named Scut1, Scut2, ..., Scutn respectively.

[0084] The above method, by adding a switching device to the circuit, selectively disconnects the transformer and primary-side H-bridge of the unconnected photovoltaic modules from the grid-connected circuit and the secondary-side bridge arm circuit by determining the current connection status. This prevents the secondary-side voltage from coupling to the primary-side voltage of the DC-side circuit without photovoltaic modules and from charging the primary-side capacitor through the primary-side H-bridge, ensuring that there is no voltage on the primary-side input side of the DC-side circuit without photovoltaic modules, thus eliminating the risk of damage to the components of the DC-side circuit without photovoltaic modules. Compared with the prior art, which reduces the DC-side voltage of the DC-side circuit without photovoltaic modules by regulation, this method reduces resource loss and increases power generation.

[0085] In one embodiment, when the first DC-side circuit and the corresponding photovoltaic module are connected to the secondary side bridge arm circuit, the capacitor voltage in the second DC-side circuit is zero, and the voltage of the primary side bridge arm circuit in the second DC-side circuit is zero.

[0086] In actual implementation, the main controller, such as the core controller MCU, can automatically control the closing and opening states of the switching device to control the connection and disconnection of the second DC side circuit with the first DC side circuit and the secondary bridge arm circuit.

[0087] When the first DC-side circuit and the corresponding photovoltaic module are connected to the secondary bridge arm circuit, the core controller MCU automatically closes the switch device corresponding to the first DC-side circuit and opens the switch device corresponding to the second DC-side circuit, so that the capacitor voltage in the second DC-side circuit is zero and the voltage of the primary bridge arm circuit in the second DC-side circuit is zero.

[0088] This approach avoids the secondary-side bridge arm circuit charging the capacitors in the DC-side circuit that are not connected to photovoltaic modules in a multi-input micro-inverter circuit system, thus eliminating the risk of damage to components in the unconnected primary-side bridge arm circuit.

[0089] Based on the aforementioned multi-input micro-inverter circuit system, a detailed description of the operation control method for a multi-input micro-inverter circuit system disclosed in this embodiment of the invention is provided. This control method is applied to the aforementioned multi-input micro-inverter circuit system, which includes multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary-side bridge arm circuits. The DC-side circuits are connected to corresponding photovoltaic modules; the secondary-side bridge arm circuits are connected to the power grid; all multiple DC-side circuits are connected to the secondary-side bridge arm circuits; the switching devices are located in the circuit between the capacitors in the secondary-side bridge arm circuits and the DC-side circuits; for example... Figure 10 As shown, the method includes the following steps:

[0090] Step S1002: Collect the DC-side voltage of the multiple DC-side circuits;

[0091] The DC-side voltage of each DC-side circuit can be detected and collected before the micro-inverter is connected to the grid.

[0092] Step S1004: Based on the DC-side voltage, determine the first DC-side circuit connected to the secondary bridge arm circuit;

[0093] The aforementioned first DC-side circuit is the DC-side circuit currently performing DC-to-AC conversion among multiple DC-side circuits. The first DC-side circuit is normally connected to the photovoltaic module and can achieve grid connection by controlling the phase shift angle of the primary side bridge arm circuit, the secondary side bridge arm circuit, and the phase shift angle of the primary side bridge arm.

[0094] Here, the first DC-side circuit can be determined by comparing the collected DC-side voltages with a preset voltage threshold. For example, the DC-side circuit with a DC-side voltage greater than the preset voltage threshold is determined as the first DC-side circuit connected to the secondary bridge arm circuit.

[0095] Step S1006: Control the switch device corresponding to the first DC side to close, and control the switch device corresponding to the second DC side circuit to open, so as to interrupt the charging path of the secondary bridge arm circuit to the capacitor in the second DC side circuit.

[0096] The aforementioned second DC-side circuit can be understood as a DC-side circuit in a multi-channel DC-side circuit that does not need to participate in the DC-to-AC conversion. This second DC-side circuit is not connected to a DC source, for example, it is not normally connected to the photovoltaic module or the photovoltaic module is completely shaded and cannot work. In this case, the second DC-side circuit belongs to the DC-side circuit that is not connected to the secondary bridge arm circuit.

[0097] By controlling the closing of the switch device corresponding to the first DC side and the opening of the switch device corresponding to the second DC side circuit, the circuit between the second DC side circuit and the first DC side circuit and the secondary bridge arm circuit is disconnected, interrupting the charging path from the secondary bridge arm circuit to the capacitor in the second DC side circuit.

[0098] The above-described operation control method for a multi-input micro-inverter circuit involves acquiring the DC-side voltages of multiple DC-side circuits; determining the first DC-side circuit connected to the secondary bridge arm circuit based on the DC-side voltages; controlling the closing of the switch corresponding to the first DC-side circuit and the opening of the switch corresponding to the second DC-side circuit to interrupt the charging path from the secondary bridge arm circuit to the capacitor in the second DC-side circuit; wherein, the second DC-side circuit is the DC-side circuit among the multiple DC-side circuits that is not connected to the secondary bridge arm circuit. In this method, by determining the first DC-side circuit connected to the secondary bridge arm circuit and the second DC-side circuit not connected to the secondary bridge arm circuit based on the DC-side voltages, and by controlling the closing of the switch corresponding to the first DC-side circuit and the opening of the switch corresponding to the second DC-side circuit, the DC-side circuit not connected to the photovoltaic module is effectively disconnected from the grid-connected circuit and the secondary bridge arm circuit, preventing the secondary bridge arm circuit from charging the capacitor in the DC-side circuit not connected to the photovoltaic module and eliminating the risk of damage to the components in the DC-side circuit not connected to the photovoltaic module.

[0099] The following embodiments provide specific implementations for determining the first DC-side circuit.

[0100] Specifically, it is determined whether the DC-side voltage of each DC-side circuit is greater than a preset voltage threshold; the DC-side circuit with a DC-side voltage greater than the preset voltage threshold is identified as the first DC-side circuit connected to the secondary bridge arm circuit.

[0101] In this method, the DC-side voltage of each DC-side circuit is compared with a preset voltage threshold to determine whether the DC-side voltage of each DC-side circuit is greater than the preset voltage threshold; the DC-side circuit with a DC-side voltage greater than the preset voltage threshold is identified as the first DC-side circuit connected to the secondary bridge arm circuit.

[0102] The following embodiments provide specific implementations for determining the second DC-side circuit.

[0103] A DC-side circuit whose DC-side voltage is less than or equal to a preset voltage threshold is identified as the second DC-side circuit that is not connected to the secondary bridge arm circuit.

[0104] In this method, the DC-side voltage of each DC-side circuit is compared with a preset voltage threshold, and the DC-side circuit with a DC-side voltage less than or equal to the preset voltage threshold is identified as the second DC-side circuit that is not connected to the secondary bridge arm circuit.

[0105] In a specific embodiment, such as Figure 11 As shown, the operation control steps of a multi-input micro-inverter circuit system are described:

[0106] Before each DC-side circuit of the microinverter system is connected to the grid, it is determined whether the DC-side voltage Vpv of each DC-side circuit is greater than a preset voltage threshold, such as 20V. If Vpvn is less than or equal to the preset voltage threshold, it is determined that the DC-side circuit (i.e., the component in the figure) is not connected to the secondary bridge arm circuit, and the switching device of the DC-side circuit is disconnected. If Vpvn is greater than the preset voltage threshold, it is determined that the DC-side circuit is connected to the secondary bridge arm circuit, and the switching device of the DC-side circuit is closed, and the DC-side circuit is then put into subsequent grid-connected operation.

[0107] The above method effectively disconnects the DC-side circuit that is not connected to the secondary bridge arm circuit from the grid-connected circuit and the secondary bridge arm circuit through the switching device of the DC-side circuit. This ensures that the secondary voltage of the normally grid-connected circuit will not affect the primary capacitor voltage of the unconnected circuit, thereby eliminating the risk of voltage and overvoltage on the primary side of the unconnected circuit. Compared with the current method of controlling the DC-side voltage by controlling the H-bridge of the unconnected circuit, this method also reduces losses and increases power generation.

[0108] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0109] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0110] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0111] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-input micro inverter circuit system, characterized in that, The system includes: multiple DC-side circuits, switching devices corresponding to the DC-side circuits, and secondary bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary bridge arm circuits are connected to the power grid; and all of the multiple DC-side circuits are connected to the secondary bridge arm circuits. The switching device is located in the circuit between the capacitor in the secondary bridge arm circuit and the DC side circuit; When the first DC side circuit and the corresponding photovoltaic module in the multi-channel DC side circuit are connected to the secondary side bridge arm circuit, the switch device corresponding to the first DC side circuit is closed and the switch device corresponding to the second DC side circuit is opened to interrupt the charging path of the secondary side bridge arm circuit to the capacitor in the second DC side circuit. The second DC-side circuit is the DC-side circuit in the multi-channel DC-side circuit that is not connected to the secondary bridge arm circuit.

2. The system according to claim 1, characterized in that, The switching device is located between the secondary bridge arm circuit and the DC side circuit.

3. The system according to claim 2, characterized in that, The DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer. The high-frequency transformer is connected to the input terminal of the secondary-side bridge arm circuit through an inductor. The switching device is located between the secondary-side bridge arm circuit and the inductor.

4. The system according to claim 2, characterized in that, The DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the switching device is located between the secondary-side bridge arm circuit and the high-frequency transformer.

5. The system according to claim 1, characterized in that, The switching device is located at a designated position within the DC-side circuit.

6. The system according to claim 5, characterized in that, The DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; the switching device is disposed between the leading bridge arm and the high-frequency transformer.

7. The system according to claim 5, characterized in that, The DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a leading bridge arm and a lagging bridge arm connected in parallel; the switching device is located between the lagging bridge arm and the high-frequency transformer.

8. The system according to claim 5, characterized in that, The DC-side circuit includes a primary-side bridge arm circuit and a high-frequency transformer; the primary-side bridge arm circuit includes a capacitor, a leading bridge arm, and a lagging bridge arm connected in parallel; the switching device is disposed between the capacitor and the leading bridge arm, or between the capacitor and the lagging bridge arm.

9. The system according to claim 1, characterized in that, When the first DC-side circuit and the corresponding photovoltaic module are connected to the secondary side bridge arm circuit, the capacitor voltage in the second DC-side circuit is zero, and the voltage of the primary side bridge arm circuit in the second DC-side circuit is zero.

10. A method for operating and controlling a multi-input micro-inverter circuit system, characterized in that, The method is applied to a multi-input micro-inverter circuit system; the system includes multiple DC-side circuits, corresponding switching devices for the DC-side circuits, and secondary-side bridge arm circuits; the DC-side circuits are connected to corresponding photovoltaic modules; the secondary-side bridge arm circuits are connected to the power grid; all the multiple DC-side circuits are connected to the secondary-side bridge arm circuits; the switching devices are located in the circuit between the capacitors in the secondary-side bridge arm circuits and the DC-side circuits; the method includes: Collect the DC-side voltage of multiple DC-side circuits; Based on the DC-side voltage, determine the first DC-side circuit connected to the secondary bridge arm circuit; The switch corresponding to the first DC side is closed, and the switch corresponding to the second DC side circuit is opened, so as to interrupt the charging path of the secondary bridge arm circuit to the capacitor in the second DC side circuit. The second DC-side circuit is the DC-side circuit in the multi-channel DC-side circuit that is not connected to the secondary bridge arm circuit.

11. The method according to claim 10, characterized in that, The step of determining the first DC-side circuit connected to the secondary bridge arm circuit based on the DC-side voltage includes: Determine whether the DC-side voltage of each DC-side circuit is greater than a preset voltage threshold. A DC-side circuit whose DC-side voltage is greater than a preset voltage threshold is identified as the first DC-side circuit connected to the secondary bridge arm circuit.

12. The method according to claim 11, characterized in that, The method further includes: A DC-side circuit whose DC-side voltage is less than or equal to a preset voltage threshold is identified as a second DC-side circuit that is not connected to the secondary bridge arm circuit.

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