Method for determining switching frequency of inverter, and inverter and photovoltaic system

Abstract

Disclosed in the present application is a method for determining the switching frequency of an inverter. The method comprises: acquiring input state information of a transformer and output state information of the transformer (01); and on the basis of the input state information and the output state information, determining the switching frequency of a switching transistor, so as to control a target current that is output by the transformer to a power grid (02).

Description

Method for determining switching frequency of inverter, inverter and photovoltaic system

[0001] Priority information

[0002] This application claims priority and benefits of patent application No. 2023118193421 filed with the State Intellectual Property Office of China on December 26, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application relates to the field of inverters, and in particular to a method for determining a switching frequency of an inverter, an inverter, and a photovoltaic system. Background Art

[0004] In a photovoltaic system, an inverter converts the direct current (DC) electricity generated by the PV generator into the alternating current (AC) power required by the grid. However, when the voltage difference between the PV generator and the grid is large, the inverter's overcurrent protection may be triggered, causing the inverter to malfunction.

[0005] Summary of the Invention

[0006] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application provides a method for determining a switching frequency of an inverter, an inverter, and a photovoltaic system.

[0007] An embodiment of the present application provides a method for determining a switching frequency of an inverter. The inverter includes a transformer, a primary bridge arm circuit, and a secondary bridge arm circuit. The primary bridge arm circuit and the secondary bridge arm circuit each include a switching transistor. The transformer receives input from a photovoltaic power generation device through the primary bridge arm circuit, so the transformer outputs current to a power grid through the secondary bridge arm circuit. The method includes:

[0008] Acquiring input status information of the transformer and output status information of the transformer;

[0009] According to the input state information and the output state information, a switching frequency of the switch tube is determined to control a target current output by the transformer to the power grid.

[0010] In the switching frequency determination method of the inverter provided in the embodiment of the present application, the inverter can obtain the input status information and the output status information of the transformer, and determine the switching frequency of the switching tube in the primary bridge arm circuit and the switching frequency of the switching tube in the secondary bridge arm circuit of the inverter based on the input status information and the output status information of the transformer, thereby controlling the target current output by the transformer to the power grid.

[0011] In this way, the embodiments of the present application enable the inverter to determine the switching frequency of the switches in the primary and secondary bridge arm circuits of the transformer based on the input and output state information of the transformer, thereby indirectly controlling the target current related to the switching frequency, so that the target current can be adjusted according to the status of the input and output sides of the transformer. For example, when the voltage of the power grid increases, causing the target current in the inverter to increase accordingly, the inverter can reduce the target current based on the determination of the switching frequency, thereby preventing the electronic components on the output side of the transformer or the inverter from triggering overcurrent protection due to excessive current, or even being damaged. This, to a certain extent, ensures the stable and safe operation of the inverter.

[0012] In certain embodiments of the present application, determining the switching frequency of the switch tube to control the target current output by the transformer to the power grid based on the input state information and the output state information includes:

[0013] determining an operating condition of the transformer according to the input state information and / or the output state information;

[0014] When the transformer is in a preset operating condition, the switching frequency is determined according to the input state information and the output state information to control the target current.

[0015] In this way, the inverter of the embodiment of the present application can adjust the switching frequency of the switching tube to control the target current when it is confirmed that the transformer is in a preset operating condition based on the input status information and / or output status information, so that the switching frequency can be determined at an appropriate time, and the safe operation of the inverter and transformer can be guaranteed.

[0016] In certain embodiments of the present application, the input state information includes an input voltage of the transformer relative to the photovoltaic power generation device, and determining the operating condition of the transformer based on the input state information and / or the output state information includes:

[0017] When the input voltage is less than a first preset threshold, it is determined that the transformer is in the preset operating condition, wherein the first preset threshold includes a maximum value of the output voltage when the transformer is in the preset operating condition.

[0018] In this way, the embodiment of the present application can determine the preset operating condition based on the input voltage of the inverter relative to the photovoltaic power generation device and a predetermined first preset threshold value. The preset operating condition can be reliably determined, thereby ensuring the reliable determination of the switching frequency to a certain extent.

[0019] In certain embodiments of the present application, the input voltage includes a first voltage of the photovoltaic power generation device, the first preset threshold includes a first target threshold, the first target threshold includes a maximum voltage of the photovoltaic power generation device when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and / or the output state information includes:

[0020] When the first voltage is less than the first target threshold, it is determined that the transformer is in the preset operating condition.

[0021] In this way, the embodiment of the present application can determine the preset operating condition according to the first voltage and the first target threshold of the photovoltaic power generation device, so that the preset operating condition can be reliably determined.

[0022] In certain embodiments of the present application, the primary bridge arm circuit includes a first capacitor connected in parallel with the photovoltaic power generation device, the input voltage includes a second voltage of the first capacitor, the first preset threshold includes a second target threshold, the second target threshold includes a maximum voltage of the first capacitor when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and the output state information includes:

[0023] When the second voltage is less than the second target threshold, it is determined that the transformer is in the preset operating condition.

[0024] In this way, the embodiment of the present application can determine the preset operating condition according to the second voltage of the first capacitor and the second target threshold, so that the preset operating condition can be reliably determined.

[0025] In certain embodiments of the present application, the input voltage includes a current primary voltage of the transformer, the first preset threshold includes a third target threshold, the third target threshold includes a maximum primary voltage of the transformer when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and the output state information includes:

[0026] When the current primary voltage is less than the third target threshold, it is determined that the transformer is in the preset operating condition.

[0027] In this way, the embodiment of the present application can determine the preset operating condition according to the current primary voltage of the transformer and the third target threshold, so that the preset operating condition can be reliably determined.

[0028] In certain embodiments of the present application, the output state information includes an input voltage of the transformer relative to the power grid, and determining the operating condition of the transformer based on the input state information and / or the output state information includes:

[0029] When the input voltage is greater than a second preset threshold, it is determined that the transformer is in the preset operating condition, wherein the second preset threshold includes a lowest value of the input voltage when the transformer is in the preset operating condition.

[0030] In this way, the embodiment of the present application can determine the preset operating condition based on the output voltage of the inverter relative to the grid and a predetermined second preset threshold value. The preset operating condition can be reliably determined, thereby ensuring the reliable determination of the switching frequency to a certain extent.

[0031] In certain embodiments of the present application, the output voltage includes a third voltage of the grid, the second preset threshold includes a fourth target threshold, the fourth target threshold includes a minimum voltage of the grid when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and / or the output state information includes:

[0032] When the third voltage is greater than the fourth target threshold, it is determined that the transformer is in the preset operating condition.

[0033] In this way, the embodiment of the present application can determine the preset operating condition according to the third voltage of the power grid and the fourth target threshold, so that the preset operating condition can be reliably determined.

[0034] In certain embodiments of the present application, the secondary bridge arm circuit includes a second capacitor connected in parallel with the power grid, the input voltage includes a fourth voltage of the second capacitor, the second preset threshold includes a fifth target threshold, the fifth target threshold includes a minimum voltage of the second capacitor when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and the output state information includes:

[0035] When the fourth voltage is greater than the fifth target threshold, it is determined that the transformer is in the preset operating condition.

[0036] In this way, the embodiment of the present application can determine the preset operating condition according to the fourth voltage and the fifth target threshold of the transformer, so that the preset operating condition can be reliably determined.

[0037] In certain embodiments of the present application, the input voltage includes a current secondary voltage of the transformer, the second preset threshold includes a sixth target threshold, the sixth target threshold includes a minimum secondary voltage of the transformer when the transformer is in the preset operating condition, and determining the operating condition of the transformer based on the input state information and the output state information includes:

[0038] When the current secondary voltage is greater than the sixth target threshold, it is determined that the transformer is in the preset operating condition.

[0039] In this way, the embodiment of the present application can determine the preset operating condition according to the current secondary voltage of the transformer and the sixth target threshold, so that the preset operating condition can be reliably determined.

[0040] In certain embodiments of the present application, the input voltage includes the input voltage of the transformer relative to the photovoltaic power generation device, the output state information includes the input voltage of the transformer relative to the power grid, and determining the operating condition of the transformer based on the input state information and / or the output state information includes:

[0041] When the input voltage is less than a third preset threshold and greater than a fourth preset threshold, it is determined that the transformer is in the preset operating condition, wherein the third preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition, and the fourth preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0042] In this way, the inverter of the embodiment of the present application can determine the operating condition of the transformer based on the input voltage of the transformer relative to the photovoltaic power generation device, the output voltage relative to the power grid, and the pre-set third preset threshold and fourth preset threshold, so that the operating condition of the transformer can be reliably determined.

[0043] In certain embodiments of the present application, when the transformer is in a preset operating condition, determining the switching frequency to control the target current according to the input state information and the output state information includes:

[0044] When the transformer is in a preset operating condition, determining a difference between the output voltage and the input voltage;

[0045] The switching frequency is determined according to a quotient of the difference and a preset current value to control the target current.

[0046] In this way, the implementation mode of the present application can determine the switching frequency of each switching tube in the primary bridge arm circuit and the secondary bridge arm circuit based on the output voltage and the difference between the output voltage and the preset current value, so that the switching frequency can be reliably determined.

[0047] An embodiment of the present application provides an inverter, including a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the switching frequency determination method of the inverter is implemented.

[0048] An embodiment of the present application provides a photovoltaic system including the above-mentioned inverter.

[0049] The embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by one or more processors, the above-mentioned method for determining the switching frequency of the inverter is implemented.

[0050] In this way, the inverter, photovoltaic system, and computer-readable storage medium provided by the embodiments of the present application can determine the switching frequency of the switching tubes in the primary bridge arm circuit and the secondary bridge arm circuit of the transformer based on the input state information and output state information of the transformer, thereby indirectly controlling the target current related to the switching frequency, so that the target current can be adjusted according to the state of the input side and output side of the transformer. For example, when the voltage of the power grid increases, causing the target current in the inverter to increase accordingly, the inverter can reduce the target current based on the determination of the switching frequency, thereby avoiding the electronic devices on the output side of the transformer or the output side of the inverter from triggering overcurrent protection due to excessive current, or even damage, thereby ensuring the stable and safe operation of the inverter to a certain extent.

[0051] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0053] FIG1 is a flow chart of a method for determining a switching frequency of an inverter in certain embodiments of the present application;

[0054] FIG2 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0055] FIG3 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0056] FIG4 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0057] FIG5 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0058] FIG6 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0059] FIG7 is a flow chart of a method for determining a switching frequency of an inverter in certain embodiments of the present application;

[0060] FIG8 is a flow chart of a method for determining a switching frequency of an inverter in certain embodiments of the present application;

[0061] FIG9 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0062] FIG10 is a flow chart of a method for determining a switching frequency of an inverter in certain embodiments of the present application;

[0063] FIG11 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0064] FIG12 is a flow chart of a method for determining a switching frequency of an inverter in certain embodiments of the present application. DETAILED DESCRIPTION

[0065] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0066] A photovoltaic system is a power generation system that converts solar radiation into electricity. Solar radiation is clean, safe, and renewable, so the power generation process of a photovoltaic system causes minimal environmental pollution and has minimal impact on the surrounding ecosystem.

[0067] Furthermore, based on the relationship between photovoltaic systems and power systems, photovoltaic systems can be divided into standalone photovoltaic systems and grid-connected photovoltaic systems. In a grid-connected photovoltaic system, photovoltaic modules (or photovoltaic power generation devices) generate direct current (DC) from solar radiation. The inverter uses phase-shift modulation to convert this DC into alternating current (AC) with the same phase frequency as the grid voltage, and then transmits the AC to the grid, thus completing the conversion of solar radiation into grid power.

[0068] Furthermore, in the process of the inverter performing phase-shift modulation based on the two variables of the inner phase-shift angle and the outer phase-shift angle to realize the current conversion function, the degrees of freedom corresponding to the phase-shift modulation only include the inner phase-shift angle and the outer phase-shift angle. Therefore, there are fewer degrees of freedom corresponding to the phase-shift modulation, making it difficult to reliably control the size of the AC power output by the inverter. For example, if the inverter outputs too high a current to the power grid, the inverter will operate abnormally, thereby triggering the overcurrent protection of the inverter, and the inverter will not be able to operate normally.

[0069] Based on the above-mentioned problems, please refer to FIG1 . An embodiment of the present application provides a method for determining the switching frequency of an inverter. The inverter includes a transformer, a primary bridge arm circuit, and a secondary bridge arm circuit. The primary bridge arm circuit and the secondary bridge arm circuit each include a switching transistor. The transformer receives input from a photovoltaic power generation device through the primary bridge arm circuit, so the transformer outputs current to the grid through the secondary bridge arm circuit. Based on this, the above-mentioned switching frequency determination method includes:

[0070] 01: Get the input status information and output status information of the transformer;

[0071] 02: Based on the input state information and output state information, determine the switching frequency of the switch tube to control the target current output by the transformer to the grid.

[0072] An embodiment of the present application provides a switching frequency determination device for an inverter. The switching frequency determination method of the inverter of the embodiment of the present application can be implemented by the switching frequency determination device of the inverter of the embodiment of the present application. Specifically, the switching frequency determination device includes an acquisition module and a determination module. The acquisition module is used to obtain input status information of the transformer and output status information of the transformer. The determination module is used to determine the switching frequency of the switching tube based on the input status information and the output status information to control the target current output by the transformer to the power grid.

[0073] The present application also provides an inverter comprising a memory and a processor. The inverter switching frequency determination method of the present application can be implemented by the inverter of the present application. Specifically, the memory stores a computer program, and the processor is configured to obtain input status information and output status information of the transformer; based on the input status information and the output status information, determine the switching frequency of the switch to control the target current output by the transformer to the power grid.

[0074] Specifically, the inverter according to the embodiments of the present application can obtain transformer input and output status information during operation to confirm the operating status of the transformer's input and output sides, and thus the operating status of the photovoltaic power generation device and the power grid. Furthermore, the inverter can determine or set the inverter's switching frequency based on the input and output status information, thereby adjusting the target current accordingly.

[0075] Among them, it can be understood that the inverter in the embodiment of the present application may refer to a micro inverter, or may refer to a centralized inverter, a string inverter, a distributed inverter, etc. The type of inverter can be set according to actual conditions. To more clearly illustrate the embodiment of the present application, please refer to Figure 2, which is a schematic diagram of the application scenario in certain embodiments of the present application. As shown in Figure 2, the inverter in the embodiment of the present application may be a single-stage micro inverter shown in Figure 2. In addition, the primary side of the single-stage micro inverter is connected to the photovoltaic module through an H-bridge circuit, and the secondary side is connected to the power grid through a bidirectional switching circuit, and the primary and secondary sides are isolated by a transformer. The DC power output by the photovoltaic module on the primary side is boosted by a transformer to obtain high-voltage AC power for input to the power grid on the secondary side.

[0076] Furthermore, within the secondary-side bidirectional switch circuit, S5 and S6 form the upper-half bridge arm bidirectional switch, while S7 and S8 form the lower-half bridge arm bidirectional switch. When the grid voltage is greater than zero, S5 and S7 perform high-frequency chopping, while S6 and S8 are directly connected. When the grid voltage is less than zero, S6 and S8 perform high-frequency chopping, while S5 and S7 are directly connected.

[0077] Furthermore, in the primary H-bridge circuit and the secondary bidirectional switch circuit, the angle by which S4 lags S1 can be understood as the inner phase shift angle D1 between the two primary bridge arms, and the angle by which S5 or S8 lags S1 can be understood as the outer phase shift angle D2 between the primary and secondary bridge arms. Furthermore, by modulating D1 and D2, the DC power output from the primary is converted to AC power for the secondary input.

[0078] It is understood that the photovoltaic power generation device in the embodiments of the present application can be understood as a device or system that can generate or output electrical energy from solar radiation, such as the photovoltaic module in Figure 1. Accordingly, as shown in Figure 2, the power grid in the embodiments of the present application can be understood as a device or system that can receive electrical energy input. Furthermore, the H-bridge circuit in Figure 2 can be understood as the primary bridge arm circuit, and the bidirectional switch circuit can be understood as the secondary bridge arm circuit.

[0079] It can also be understood that the inverter of the embodiment of the present application can be applied to other situations in addition to the topology or structure shown in Figure 2. For example, please refer to Figures 3, 4 and 5. Specifically, as shown in Figure 3, the primary bridge arm circuit in the embodiment of the present application can be a half-bridge structure, and the secondary bridge arm circuit is a bidirectional switch circuit structure. As shown in Figure 4, the primary bridge arm circuit in the embodiment of the present application can be an H-bridge structure, and the secondary bridge arm circuit is a full-bridge structure. As shown in Figure 5, the primary bridge arm circuit in the embodiment of the present application can be a half-bridge circuit structure, and the secondary bridge arm circuit is a full-bridge structure.

[0080] Furthermore, transformer input status information can be understood as information that characterizes the operating status of various components on the transformer's input side, including various types of information that characterizes the operating status of photovoltaic power generation devices. Transformer output status information can be understood as information that characterizes the operating status of various components on the transformer's output side, including various types of information that characterizes the operating status of the power grid. It is understood that the specific content of the input status information and output status information can be set based on actual circumstances.

[0081] It should also be noted that, according to the circuit structure and functional settings of the inverter, the inverter and the transformer can be equivalent to an inductor to a certain extent. Further, please refer to Figure 6, which is a schematic diagram of the application scenario of certain embodiments of the present application. That is, the electric energy output by the photovoltaic power generation device 201 is converted into a corresponding secondary inductor current through the inductor 202, and the secondary inductor current is input to the power grid 203. Therefore, the secondary inductor current is related to the photovoltaic power generation device 201 and the power grid 203, or in other words, the current input to the power grid, that is, the target current, is related to the voltage and current of the photovoltaic power generation device 201, and is also related to the voltage and current of the power grid 203.

[0082] At the same time, based on the interaction between the inverter and the inductor, the target current is also related to the switching frequency of the switches used to implement phase-shift modulation in the inverter. For example, in the structure shown in Figure 2, the target current is related to the switching frequency of S1 through S8 in the primary and secondary bridge arms. Furthermore, higher switching frequencies result in lower target currents, while lower switching frequencies result in higher target currents.

[0083] Therefore, the inverter of the embodiment of the present application can determine or set the switching frequency of the inverter according to the input status information of the photovoltaic power generation device and the output status information of the power grid, so that when the target current is too high due to the operating status of the photovoltaic power generation device and the power grid, it can be reduced according to the increase of the switching frequency, or when the target current is too low due to the operating status of the photovoltaic power generation device and the power grid, it can be increased according to the reduction of the switching frequency.

[0084] It can be understood that compared to the situation where the switching frequency is fixed, the inverter of the embodiment of the present application can indirectly control the target current related to the switching frequency through the switching frequency that is dynamically set by the input status information of the photovoltaic power generation device and the output status information of the power grid, so that the target current can be adjusted according to the actual situation, avoiding the situation where the target current is only determined by the photovoltaic power generation device and the power grid, or only determined by the aforementioned phase shift angles D1 and D2, which may cause the target current to be too high and trigger the overcurrent protection of the electronic device, or even damage the electronic device.

[0085] It is also understandable that the method of adjusting the switching frequency of the inverter can be set according to actual conditions, such as based on analog regulation and digital regulation.

[0086] In summary, the embodiments of the present application enable the inverter to determine the switching frequency of the switches in the primary and secondary bridge arm circuits of the transformer based on the input and output state information of the transformer, thereby indirectly controlling the target current related to the switching frequency, so that the target current can be adjusted according to the status of the input and output sides of the transformer. For example, when the voltage of the power grid increases, causing the target current in the inverter to increase accordingly, the inverter can reduce the target current based on the determination of the switching frequency, thereby preventing the electronic components on the output side of the transformer or the inverter from triggering overcurrent protection due to excessive current, or even being damaged. This, to a certain extent, ensures the stable and safe operation of the inverter.

[0087] Furthermore, it is understood that when the switching frequency is fixed, the target current can only be determined by the aforementioned phase shift angles D1 and D2. However, in the embodiments of the present application, the target current can be determined not only by the aforementioned phase shift angles D1 and D2 but also by the switching frequency, thereby enabling more accurate control or adjustment of the target current.

[0088] Furthermore, because the target current can be changed by the switching frequency, when the target current is at a higher value due to the operating state of the power grid and / or the photovoltaic power generation device, such as when the power grid voltage is higher than 250V, the inverter can adjust the switching frequency to maintain the target current within the rated range, thereby ensuring stable operation of the inverter and enabling the inverter to operate in a wider range of operating states. For example, before the implementation of the present application, the inverter can operate when the power grid voltage is in the range of [200V, 250V], but after the implementation of the present application, the inverter can operate when the power grid voltage is in the range of [180V, 287V].

[0089] Furthermore, it is also understood that the inverter according to the embodiments of the present application may obtain input status information and output status information once at the end of each AC power cycle to perform a subsequent switching frequency determination operation. Alternatively, the inverter may obtain input status information and output status information once every predetermined time interval, such as 5 seconds, to perform a subsequent switching frequency determination operation.

[0090] Please refer to FIG. 7 . In certain embodiments of the present application, step 02 includes:

[0091] 020: Determine the operating condition of the transformer according to the input status information and / or the output status information;

[0092] 021: When the transformer is in a preset operating condition, the switching frequency is determined according to the input state information and the output state information to control the target current.

[0093] The determination module of the embodiment of the present application is also used to determine the operating condition of the transformer based on the input status information and / or output status information; when the transformer is in a preset operating condition, the switching frequency is determined based on the input status information and the output status information to control the target current.

[0094] The processor of the embodiment of the present application is also used to determine the operating condition of the transformer based on the input status information and / or output status information; when the transformer is in a preset operating condition, the switching frequency is determined based on the input status information and the output status information to control the target current.

[0095] Specifically, the inverter of the embodiment of the present application ensures that the switching frequency can be adjusted at the appropriate time. Therefore, when the input status information and output status information of the transformer are obtained, it can be confirmed whether the current operating condition of the transformer will affect the electronic devices on the output side of the transformer, that is, whether the transformer is in the preset operating condition.

[0096] Furthermore, if it is confirmed based on the input status information and / or output status information that the transformer is not in the preset operating condition, it means that the target current transmitted by the transformer to the grid through the secondary bridge arm circuit is not a high value, and therefore the various devices in the secondary bridge arm circuit can operate normally.

[0097] Conversely, if the transformer is confirmed to be in a preset operating condition based on the input status information and / or the output status information, this indicates that the target current transmitted by the transformer to the grid through the secondary bridge arm circuit is a relatively high value. Consequently, the various components in the secondary bridge arm circuit may trigger overcurrent protection due to the high target current, or even be damaged. Therefore, the inverter according to the embodiments of the present application can adjust the switching frequency based on the input status information and the output status information to reduce the target current when the transformer is in the preset operating condition, thereby enabling the various components in the secondary bridge arm circuit to operate normally.

[0098] In this way, the inverter of the embodiment of the present application can adjust the switching frequency of the switching tube to control the target current when it is confirmed that the transformer is in a preset operating condition based on the input status information and / or output status information, so that the switching frequency can be determined at an appropriate time, and the safe operation of the inverter and transformer can be guaranteed.

[0099] In certain embodiments of the present application, the input state information includes the input voltage of the transformer relative to the photovoltaic power generation device, and step 020 includes:

[0100] When the input voltage is less than a first preset threshold, it is determined that the transformer is in a preset operating condition, wherein the first preset threshold includes a maximum value of the output voltage when the transformer is in the preset operating condition.

[0101] The determination module of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is less than a first preset threshold, wherein the first preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition.

[0102] The processor of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is less than a first preset threshold, wherein the first preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition.

[0103] Specifically, the inverter of the embodiment of the present application can determine whether the operating condition of the inverter is a preset operating condition based on the voltage on the input side of the inverter, or in other words, determine the operating condition of the inverter based on the input voltage of the inverter relative to the photovoltaic power generation device and a predetermined first preset threshold.

[0104] The first preset threshold is a priori knowledge. In other words, the first preset threshold includes the highest value of the input voltage collected or previously acquired when the inverter is in a preset operating condition. Therefore, if the input voltage is less than the first preset threshold, it can be determined that the transformer is in the preset operating condition.

[0105] In this way, the embodiment of the present application can determine the preset operating condition based on the input voltage of the inverter relative to the photovoltaic power generation device and a predetermined first preset threshold value. The preset operating condition can be reliably determined, thereby ensuring the reliable determination of the switching frequency to a certain extent.

[0106] In certain embodiments of the present application, the input voltage includes a first voltage of the photovoltaic power generation device, the first preset threshold includes a first target threshold, the first target threshold includes a maximum voltage of the photovoltaic power generation device when the transformer is in a preset operating condition, and determining the operating condition of the transformer according to the input state information and / or the output state information includes:

[0107] When the first voltage is less than the first target threshold, it is determined that the transformer is in a preset operating condition.

[0108] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the first voltage is less than a first target threshold.

[0109] The processor of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the first voltage is less than a first target threshold.

[0110] To more clearly illustrate the embodiments of the present application, please refer to Figures 2 to 5. Specifically, the inverter can determine whether the transformer operating condition is a preset operating condition based on the voltage across the photovoltaic module (i.e., photovoltaic power generation device) in Figures 2 to 5 and a predetermined first target threshold. The first target threshold can be a value greater than 34V, such as 40V.

[0111] Furthermore, the inverter of the embodiment of the present application can determine that the transformer is in a preset operating condition when the voltage on both sides of the photovoltaic module is less than a preset first target threshold, or in other words, when the first voltage is less than the first target threshold.

[0112] In this way, the embodiment of the present application can determine the preset operating condition according to the first voltage and the first target threshold of the photovoltaic power generation device, so that the preset operating condition can be reliably determined.

[0113] In certain embodiments of the present application, the primary bridge arm circuit includes a first capacitor connected in parallel with the photovoltaic power generation device, the input voltage includes the second voltage of the first capacitor, the first preset threshold includes the second target threshold, and step 020 includes:

[0114] When the second voltage is less than the second target threshold, it is determined that the transformer is in a preset operating condition.

[0115] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the second voltage is less than a second target threshold.

[0116] The processor of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the second voltage is less than a second target threshold.

[0117] To more clearly illustrate the embodiment of the present application, please refer to FIG. 2 to FIG. 5 , that is, the inverter can be based on the capacitor C in FIG. 2 to FIG. 5 bus The voltage across the first capacitor and a predetermined second target threshold value are used to determine whether the operating condition of the transformer is the preset operating condition. The second target threshold value may be a value greater than 34V, such as 40V.

[0118] Furthermore, the inverter of the embodiment of the present application can determine that the transformer is in a preset operating condition when the voltage across the first capacitor is less than a preset second target threshold, or in other words, when the second voltage is less than the second target threshold.

[0119] In this way, the embodiment of the present application can determine the preset operating condition according to the second voltage of the first capacitor and the second target threshold, so that the preset operating condition can be reliably determined.

[0120] In certain embodiments of the present application, the input voltage includes a current primary voltage of the transformer, the first preset threshold includes a third target threshold, the third target threshold includes a maximum primary voltage of the transformer when the transformer is in a preset operating condition, and step 020 includes:

[0121] When the current primary voltage is less than the third target threshold, it is determined that the transformer is in a preset operating condition.

[0122] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the current primary voltage is less than a third target threshold.

[0123] The processor of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the current primary voltage is less than a third target threshold.

[0124] To more clearly illustrate the embodiment of the present application, please refer to FIG. 2 to FIG. 5 , that is, the inverter can be based on the v in FIG. 2 to FIG. 5 p , and a predetermined third target threshold value, to determine whether the operating condition of the transformer is the preset operating condition. Wherein, the second target threshold value can be a value greater than 34V, such as 40V.

[0125] And, the inverter of the embodiment of the present application can be p When the voltage is less than the preset third target threshold, or in other words, when the current primary voltage is less than the third target threshold, it is determined that the transformer is in a preset operating condition.

[0126] In this way, the embodiment of the present application can determine the preset operating condition according to the current primary voltage of the transformer and the third target threshold, so that the preset operating condition can be reliably determined.

[0127] In certain embodiments of the present application, the output state information includes the input voltage of the transformer relative to the grid, and step 020 includes:

[0128] When the input voltage is greater than a second preset threshold, it is determined that the transformer is in a preset operating condition, wherein the second preset threshold includes a lowest value of the input voltage when the transformer is in the preset operating condition.

[0129] The determination module of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is greater than a second preset threshold, wherein the second preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0130] The processor of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is greater than a second preset threshold, wherein the second preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0131] Specifically, the inverter of the embodiment of the present application can determine whether the operating condition of the inverter is a preset operating condition based on the voltage on the output side (or secondary side) of the inverter, or in other words, determine the operating condition of the inverter based on the input voltage of the inverter relative to the power grid and a predetermined second preset threshold.

[0132] The second preset threshold is a priori knowledge, or in other words, it includes the lowest value of the input voltage when the inverter is in a preset operating condition, which has been previously collected or gathered. Therefore, if the input voltage is greater than the second preset threshold, the transformer can be determined to be in the preset operating condition.

[0133] In this way, the embodiment of the present application can determine the preset operating condition based on the output voltage of the inverter relative to the grid and a predetermined second preset threshold value. The preset operating condition can be reliably determined, thereby ensuring the reliable determination of the switching frequency to a certain extent.

[0134] In certain embodiments of the present application, the output voltage includes a third voltage of the grid, the second preset threshold includes a fourth target threshold, the fourth target threshold includes a minimum voltage of the grid when the transformer is in a preset operating condition, and step 020 includes:

[0135] When the third voltage is greater than the fourth target threshold, it is determined that the transformer is in a preset operating condition.

[0136] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the third voltage is greater than a fourth target threshold.

[0137] The processor of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the third voltage is greater than a fourth target threshold.

[0138] To more clearly illustrate the embodiments of the present application, please refer to Figures 2 to 5 . Specifically, the inverter can determine whether the transformer operating condition is a preset operating condition based on the voltages across the grid in Figures 2 to 5 and a predetermined fourth target threshold. The fourth target threshold can be a value less than 287V, such as 280V.

[0139] Furthermore, the inverter of the embodiment of the present application can determine that the transformer is in a preset operating condition when the voltage on both sides of the grid is greater than a preset fourth target threshold, or in other words, when the third voltage is greater than the fourth target threshold.

[0140] Additionally, it should be noted that the third voltage can be understood as the instantaneous voltage value on both sides of the grid, collected by the inverter when receiving the instruction to obtain output status information. Alternatively, the third voltage can also be understood as the highest value that the grid fundamental voltage can reach within a cycle, collected by the inverter when receiving the instruction to obtain output status information.

[0141] In this way, the embodiment of the present application can determine the preset operating condition according to the third voltage of the power grid and the fourth target threshold, so that the preset operating condition can be reliably determined.

[0142] In certain embodiments of the present application, the secondary bridge arm circuit includes a second capacitor connected in parallel with the grid, the input voltage includes a fourth voltage of the second capacitor, the second preset threshold includes a fifth target threshold, the fifth target threshold includes a minimum voltage of the second capacitor when the transformer is in a preset operating condition, and determining the operating condition of the transformer based on the input state information and the output state information includes:

[0143] When the fourth voltage is greater than the fifth target threshold, it is determined that the transformer is in a preset operating condition.

[0144] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the fourth voltage is greater than a fifth target threshold.

[0145] The processor in the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the fourth voltage is greater than a fifth target threshold.

[0146] To more clearly illustrate the implementation of the present application, please refer to Figures 2 and 3. That is, the inverter can determine whether the operating condition of the transformer is the preset operating condition based on the voltage on both sides of capacitors C1 and / or C2 in Figures 2 and 3, and a predetermined fifth target threshold.

[0147] Furthermore, when the fourth voltage is the voltage across capacitors C1 or C2, the fifth target threshold value may be a value less than half of 287 V, such as 140 V. Furthermore, when the fourth voltage is the voltage across capacitors C1 and C2, the fifth target threshold value may be a value less than 287 V, such as 280 V.

[0148] Furthermore, the inverter of the embodiment of the present application can determine that the transformer is in a preset operating condition when the voltage across either capacitor C1 or C2 is greater than a preset fifth target threshold, or in other words, when the fourth voltage is greater than the fifth target threshold.

[0149] In this way, the embodiment of the present application can determine the preset operating condition according to the fourth voltage and the fifth target threshold of the transformer, so that the preset operating condition can be reliably determined.

[0150] In certain embodiments of the present application, the input voltage includes a current secondary voltage of the transformer, the second preset threshold includes a sixth target threshold, the sixth target threshold includes a minimum secondary voltage of the transformer when the transformer is in a preset operating condition, and determining the operating condition of the transformer according to the input state information and the output state information includes:

[0151] When the current secondary voltage is greater than the sixth target threshold, it is determined that the transformer is in a preset operating condition.

[0152] The determination module of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the current secondary voltage is greater than a sixth target threshold.

[0153] The processor of the embodiment of the present application is further configured to determine that the transformer is in a preset operating condition when the current secondary voltage is greater than a sixth target threshold.

[0154] To more clearly illustrate the embodiment of the present application, please refer to FIG. 2 to FIG. 5 , that is, the inverter can be based on the v in FIG. 2 to FIG. 5 s , and a predetermined sixth target threshold value, to determine whether the operating condition of the transformer is the preset operating condition. The sixth target threshold value may be a value less than 287V, such as 280V.

[0155] And, the inverter of the embodiment of the present application can be s When the voltage is greater than the preset sixth target threshold, or in other words, when the current secondary voltage is greater than the sixth target threshold, it is determined that the transformer is in the preset operating condition.

[0156] In this way, the embodiment of the present application can determine the preset operating condition according to the current secondary voltage of the transformer and the sixth target threshold, so that the preset operating condition can be reliably determined.

[0157] In certain embodiments of the present application, the input voltage includes the input voltage of the transformer relative to the photovoltaic power generation device, and the output state information includes the input voltage of the transformer relative to the power grid. Step 020 includes:

[0158] When the input voltage is less than a third preset threshold and the input voltage is greater than a fourth preset threshold, it is determined that the transformer is in a preset operating condition, wherein the third preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition, and the fourth preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0159] The determination module of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is less than a third preset threshold and the input voltage is greater than a fourth preset threshold, wherein the third preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition, and the fourth preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0160] The processor of the embodiment of the present application is also used to determine that the transformer is in a preset operating condition when the input voltage is less than a third preset threshold and the input voltage is greater than a fourth preset threshold, wherein the third preset threshold includes the highest value of the output voltage when the transformer is in the preset operating condition, and the fourth preset threshold includes the lowest value of the input voltage when the transformer is in the preset operating condition.

[0161] To more clearly illustrate the embodiment of the present application, please refer to Figures 2 to 5. That is, the input voltage in the embodiment of the present application can be the voltage (corresponding to the first voltage) on both sides of the photovoltaic module (corresponding to the photovoltaic power generation device) in Figures 2 to 5, or the capacitor C in Figures 2 to 5. bus The voltage on both sides of the capacitor (corresponding to the second voltage) can also be the voltage V in Figures 2 to 5. p (corresponding to the current primary voltage).

[0162] Correspondingly, the output voltage in the embodiment of the present application can be the voltage on both sides of the grid in Figures 2 to 5 (corresponding to the third voltage), or the voltage on both sides of the capacitor C1 and / or C2 (corresponding to the second capacitor) in Figures 2 to 3 (corresponding to the fourth voltage), or v in Figures 2 to 5. s (corresponding to the current secondary voltage).

[0163] Furthermore, the third preset threshold and the fourth preset threshold in the implementation manner of the present application can be set according to actual conditions.

[0164] For example, in some embodiments, the third preset threshold value ranges from [32V, 36V], and the fourth preset threshold value ranges from [285V, 289V]. In other embodiments, the third preset threshold value is 34V, and the fourth preset threshold value is 287V.

[0165] Thus, the embodiments of the present application can determine whether the operating condition of the transformer is a preset operating condition based on the acquired input voltage and output voltage, the third preset threshold corresponding to the input voltage, and the fourth preset threshold corresponding to the output voltage. It can be understood that compared to the method of determining the operating condition based solely on the operating status information of the output or input side of the transformer, the method of determining the transformer operating condition based on both the input voltage and the output voltage in the embodiments of the present application has higher accuracy.

[0166] In this way, the inverter of the embodiment of the present application can determine the operating condition of the transformer based on the input voltage of the transformer relative to the photovoltaic power generation device, the output voltage relative to the power grid, and the pre-set third preset threshold and fourth preset threshold, so that the operating condition of the transformer can be reliably determined.

[0167] Please refer to the figure. In some embodiments of the present application, step 021 includes:

[0168] 0210: Determine the difference between the output voltage and the input voltage when the transformer is in a preset operating condition;

[0169] 0211: According to the quotient of the difference and the preset current value, the switching frequency is determined to control the target current.

[0170] The determination module of the embodiment of the present application is also used to determine the difference between the output voltage and the input voltage when the transformer is in a preset operating condition; and determine the switching frequency to control the target current based on the quotient of the difference and the preset current value.

[0171] The processor of the embodiment of the present application is also used to determine the difference between the output voltage and the input voltage when the transformer is in a preset operating condition; and determine the switching frequency to control the target current based on the quotient of the difference and the preset current value.

[0172] To more clearly illustrate the implementation of this application, please refer to the following formula:

[0173] Where, f s represents the switching frequency of the inverter, i L Indicates the preset current value, u p Indicates the output voltage converted to the primary side through the transformer turns ratio, u dc Indicates the input voltage.

[0174] It is understood that the input voltage in the embodiment of the present application can be the voltage (corresponding to the first voltage) on both sides of the photovoltaic module (corresponding to the photovoltaic power generation device) in Figures 2 to 5, or the capacitor C in Figures 2 to 5. bus The voltage on both sides of the capacitor (corresponding to the second voltage) can also be the voltage V in Figures 2 to 5. p (corresponding to the current primary voltage).

[0175] Correspondingly, the output voltage in the embodiment of the present application can be the voltage on both sides of the grid in Figures 2 to 5 (corresponding to the third voltage), or the voltage on both sides of the capacitor C1 and / or C2 (corresponding to the second capacitor) in Figures 2 to 3 (corresponding to the fourth voltage), or v in Figures 2 to 5. s (corresponding to the current secondary voltage).

[0176] Furthermore, when the output voltage is the voltage on both sides of the grid, that is, the third voltage, the inverter can obtain the third voltage by collecting the instantaneous values ​​of the voltage on both sides of the grid, or by collecting the highest value that the fundamental voltage of the grid can reach within one cycle to obtain the third voltage.

[0177] In addition, when the output voltage is the voltage across capacitor C1 or C2, the voltage across capacitor C1 or C2 can be multiplied by 2, that is, double the value of the voltage across capacitor C1 or C2 can be used as the output voltage to be substituted into the above formula.

[0178] Correspondingly, when the output voltage is the voltage across the capacitors C1 and C2 , the voltage across the capacitors C1 and C2 can be directly substituted into the above formula.

[0179] In this way, the implementation mode of the present application can determine the switching frequency of each switching tube in the primary bridge arm circuit and the secondary bridge arm circuit based on the output voltage and the difference between the output voltage and the preset current value, so that the switching frequency can be reliably determined.

[0180] Optionally, please refer to Figures 9 and 10. Figure 9 is a schematic diagram of an application scenario of certain embodiments of the present application, and Figure 10 is a flow chart of a method for determining the switching frequency of an inverter in certain embodiments of the present application. p Indicates the fundamental voltage peak value of the power grid, which is also the third voltage. dc Indicates the first voltage of the photovoltaic power generation device. p_max represents the fourth preset threshold, u dc_th Indicates the third preset threshold.

[0181] Therefore, as shown in FIG9 and FIG10, the inverter of the embodiment of the present application can be dc <u dc_th andu p >u p_max In the case of u p and u dc In the case of region 2 in FIG. 9 , the current switching frequency of the inverter is determined and updated according to the third voltage and the first voltage, thereby reducing the target current delivered by the transformer to the grid, or in other words, reducing the voltage on both sides of the grid.

[0182] In contrast, in u dc ≥u dc_th or u p ≤u p_max In the case of u p and u dc When the inverter does not fall into area 2 in FIG. 9 , the inverter may maintain the current switching frequency unchanged, thereby completing the update of the current switching frequency.

[0183] It can be understood that the specific value of the first preset threshold and the specific value of the second preset threshold can be set according to actual conditions.

[0184] For example, in some embodiments, the third preset threshold value ranges from [32V, 36V], and the fourth preset threshold value ranges from [285V, 289V]. In other embodiments, the first preset threshold value is 34V, and the second preset threshold value is 287V.

[0185] Optionally, in certain embodiments of the present application, please refer to FIG11 and FIG12, FIG11 is a schematic diagram of an application scenario of certain embodiments of the present application, and FIG12 is a flow chart of a method for determining the switching frequency of an inverter in certain embodiments of the present application. t Indicates the current instantaneous voltage of the power grid, which is also the third voltage. dc Indicates the first voltage of the photovoltaic power generation device. t_max represents the fourth preset threshold, u dc_th Indicates the third preset threshold.

[0186] Therefore, as shown in Figures 11 and 12, assuming u dc <u dc_th Established, then: in |u t |>u t_max When satisfied, that is, it is u t or -u t In the case of falling into area 4 in FIG11 , the current switching frequency of the inverter is determined and updated according to the first voltage and the third voltage to reduce the target current delivered by the transformer to the grid, or in other words, to reduce the voltage on both sides of the grid; conversely, in |u t |≤u t_max When satisfied, that is, it is u t or -u t When falling into area 3 in FIG11 , the inverter can maintain the current switching frequency unchanged, thereby completing the update of the current switching frequency.

[0187] It can be understood that the specific value of the third preset threshold and the specific value of the fourth preset threshold can be set according to actual conditions.

[0188] For example, in some embodiments, the third preset threshold value ranges from [32V, 36V], and the fourth preset threshold value ranges from [285V, 289V]. In other embodiments, the third preset threshold value is 34V, and the fourth preset threshold value is 287V.

[0189] An embodiment of the present application further provides a photovoltaic system, which includes the above-mentioned inverter.

[0190] In the description of this specification, the descriptions with reference to the terms "particularly", "further", "particularly", "understandably", etc. are intended to mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms are not intended to refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0191] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present application belong.

[0192] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for determining the switching frequency of an inverter, characterized in that, The inverter includes a transformer, a primary bridge arm circuit, and a secondary bridge arm circuit. The primary bridge arm circuit and the secondary bridge arm circuit each include a switching tube. The transformer receives the input from the photovoltaic power generation device through the primary bridge arm circuit, and thus the transformer outputs current to the power grid through the secondary bridge arm circuit. The method includes: Obtaining input state information of the transformer and output state information of the transformer; Determining a switching frequency of the switching tube according to the input state information and the output state information to control a target current output by the transformer to the power grid.

2. The method according to claim 1, wherein The determining the switching frequency of the switching tube according to the input state information and the output state information to control the target current output by the transformer to the power grid includes: Determining an operating condition of the transformer according to the input state information and / or the output state information; When the transformer is in a preset operating condition, determining the switching frequency according to the input state information and the output state information to control the target current.

3. The method according to claim 2, wherein The input state information includes an input voltage of the transformer relative to the photovoltaic power generation device. The determining the operating condition of the transformer according to the input state information and / or the output state information includes: When the input voltage is less than a first preset threshold, determining that the transformer is in the preset operating condition, where the first preset threshold includes a maximum value of the output voltage when the transformer is in the preset operating condition.

4. The method according to claim 3, characterized in that The input voltage includes a first voltage of the photovoltaic power generation device, the first preset threshold includes a first target threshold, and the first target threshold includes a maximum voltage of the photovoltaic power generation device when the transformer is in the preset operating condition. The determining the operating condition of the transformer according to the input state information and / or the output state information includes: When the first voltage is less than the first target threshold, determining that the transformer is in the preset operating condition.

5. The method according to claim 3, characterized in that, The primary bridge arm circuit includes a first capacitor connected in parallel with the photovoltaic power generation device. The input voltage includes a second voltage of the first capacitor, the first preset threshold includes a second target threshold, and the second target threshold includes a maximum voltage of the first capacitor when the transformer is in the preset operating condition. The determining the operating condition of the transformer according to the input state information and the output state information includes: When the second voltage is less than the second target threshold, determining that the transformer is in the preset operating condition.

6. The method according to claim 3, wherein The input voltage includes a current primary voltage of the transformer, the first preset threshold includes a third target threshold, and the third target threshold includes a maximum primary voltage of the transformer when the transformer is in the preset operating condition. The determining the operating condition of the transformer according to the input state information and the output state information includes: When the current primary voltage is less than the third target threshold, determining that the transformer is in the preset operating condition.

7. The method according to claim 2, wherein The output status information includes the input voltage of the transformer relative to the power grid. Determining the operating condition of the transformer according to the input status information and / or the output status information includes: When the input voltage is greater than a second preset threshold, it is determined that the transformer is in the preset operating condition, where the second preset threshold includes the minimum value of the input voltage when the transformer is in the preset operating condition.

8. The method according to claim 7, characterized in that The output voltage includes a third voltage of the power grid. The second preset threshold includes a fourth target threshold, and the fourth target threshold includes the minimum voltage of the power grid when the transformer is in the preset operating condition. Determining the operating condition of the transformer according to the input status information and / or the output status information includes: When the third voltage is greater than the fourth target threshold, it is determined that the transformer is in the preset operating condition.

9. The method according to claim 7, wherein The secondary side bridge arm circuit includes a second capacitor connected in parallel with the power grid. The input voltage includes a fourth voltage of the second capacitor. The second preset threshold includes a fifth target threshold, and the fifth target threshold includes the minimum voltage of the second capacitor when the transformer is in the preset operating condition. Determining the operating condition of the transformer according to the input status information and the output status information includes: When the fourth voltage is greater than the fifth target threshold, it is determined that the transformer is in the preset operating condition.

10. The method according to claim 7, characterized in that, The input voltage includes the current secondary side voltage of the transformer. The second preset threshold includes a sixth target threshold, and the sixth target threshold includes the minimum secondary side voltage of the transformer when the transformer is in the preset operating condition. Determining the operating condition of the transformer according to the input status information and the output status information includes: When the current secondary side voltage is greater than the sixth target threshold, it is determined that the transformer is in the preset operating condition.

11. The method according to claim 2, wherein The input voltage includes the input voltage of the transformer relative to the photovoltaic power generation device. The output status information includes the input voltage of the transformer relative to the power grid. Determining the operating condition of the transformer according to the input status information and / or the output status information includes: When the input voltage is less than a third preset threshold and greater than a fourth preset threshold, it is determined that the transformer is in the preset operating condition, where the third preset threshold includes the maximum value of the output voltage when the transformer is in the preset operating condition, and the fourth preset threshold includes the minimum value of the input voltage when the transformer is in the preset operating condition.

12. The method according to claim 11, wherein When the transformer is in the preset operating condition, determining the switching frequency according to the input status information and the output status information to control the target current includes: When the transformer is in the preset operating condition, determining the difference between the output voltage and the input voltage; Determining the switching frequency to control the target current according to the quotient of the difference and a preset current value.

13. An inverter, characterized in that, It includes a memory and a processor. A computer program is stored in the memory. When the computer program is executed by the processor, the method according to any one of claims 1-12 is implemented.

14. A photovoltaic system, characterized in that, It includes the inverter according to claim 13.

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