Control method, inverter and photovoltaic system

Abstract

Disclosed in the present application is a control method, the method comprising: (01) acquiring target operation state information of an output end circuit of a transformer, and determining the operation state of a power grid on the basis of the target operation state information; and (02) when it is determined that the power grid is in the preset operation state, controlling switch transistors in the output end circuit and an input end circuit of the transformer, so as to reduce the target current.

Description

Control method, inverter and photovoltaic system

[0001] Priority information

[0002] This application claims priority and benefits of patent application No. 2023118193493 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 control, and in particular to a control method, an inverter, and a photovoltaic system. Background Art

[0004] During PV system operation, the grid voltage may drop from its rated value to a lower voltage or even to zero due to unexpected factors such as lightning strikes. However, as the grid voltage rises from a lower voltage to its rated value, the inverter's inductor current also increases, potentially damaging the inverter's electronic components due to the excessive inductor current.

[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 control method, an inverter, and a photovoltaic system.

[0007] The present application provides a control method for an inverter, wherein the inverter includes a transformer, an input circuit, and an output circuit. The input circuit and the output circuit each include a switch tube. The transformer is capable of outputting a target current input by a photovoltaic power generation device through the input circuit to a power grid through the output circuit. The method includes:

[0008] Acquiring target operating state information of the output end circuit to determine the operating state of the power grid;

[0009] When the power grid is in a preset operating state, the switch tube is controlled to reduce the target current, wherein when the power grid is in the preset operating state, the voltage peak of the power grid is on an upward trend.

[0010] In the control method provided in the embodiments of this application, the inverter can obtain target operating state information of the transformer's output circuit and determine the grid's operating state based on the target operating state information. If the grid is determined to be in a preset operating state, the inverter controls the switches in the transformer's output and input circuits to reduce the target current.

[0011] In this way, the inverter of the embodiment of the present application can control the switches in the input and output circuits to reduce the target current of the transformer when the grid is in a preset operating state. For example, when the grid voltage rises from a lower voltage to the rated value, the inverter can control the switches in the input and output circuits to reduce the target current of the transformer, thereby ensuring the stable operation of the inverter and photovoltaic system to a certain extent. The embodiment of the present application can also determine the operating state of the grid based on the obtained target operating state information, so that the switches can be adjusted at the appropriate time, ensuring reliable control of the switches.

[0012] In certain embodiments of the present application, when the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes:

[0013] When the power grid is in the preset operating state, obtaining a current value of the target current;

[0014] When the current current value is greater than a preset current value, the switch tube is controlled to reduce the target current, wherein the preset current value includes a minimum value of the target current when the power grid is in the preset operating state.

[0015] In this way, the inverter of the embodiment of the present application can obtain the current current value of the target current when the power grid is in a preset operating state, and control the switch tube when the current current value of the target current is greater than the preset current value, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0016] In certain embodiments of the present application, the target current includes a current primary inductor current of the transformer, the preset current value includes a first current threshold, the first current threshold includes a minimum primary inductor current of the transformer when the power grid is in the preset operating state, and when the current current value is greater than the preset current value, controlling the switch to reduce the target current includes:

[0017] When the current primary inductor current is greater than a first current threshold, the switch tube is controlled to reduce the target current.

[0018] In this way, the inverter of the embodiment of the present application can obtain the current primary inductor current when the power grid is in a preset operating state, and control the switch tube when the current primary inductor current is greater than the first current threshold, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0019] In certain embodiments of the present application, the target current includes a current secondary inductor current of the transformer, the preset current value includes a second current threshold, the second current threshold includes a minimum secondary inductor current of the transformer when the power grid is in the preset operating state, and when the current current value is greater than the preset current value, controlling the switch tube to reduce the target current includes:

[0020] When the current secondary-side inductor current is greater than a second current threshold, the switch tube is controlled to reduce the target current.

[0021] In this way, the inverter of the embodiment of the present application can obtain the current secondary inductor current when the power grid is in a preset operating state, and control the switch tube when the current secondary inductor current is greater than the second current threshold, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0022] In certain embodiments of the present application, when the current current value is greater than a preset current value, controlling the switch tube to reduce the target current includes:

[0023] When the current value is greater than the preset current value, the switch tube is controlled to switch to an off state to reduce the target current.

[0024] In this way, the inverter of the embodiment of the present application can control the switch tubes in the input circuit and the output circuit to switch to the off state when the current current value of the target current is greater than the preset current value, so that the inverter itself is blocked, thereby achieving a reduction in the target current.

[0025] In certain embodiments of the present application, the switch tube can be used to generate a phase-shift modulation signal, and when the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes:

[0026] When the duration of the switch tube being in the off state meets the preset duration, the switch tube is controlled to switch to the on-off state, and the phase-shift modulation signal generated by the switch tube is controlled according to the output end information to reduce the target current.

[0027] In this way, the inverter of the embodiment of the present application can control the switch tube to switch to the open and close state when the duration of the switch tube in the off state meets the preset duration, and then perform phase shift modulation through the switch tube in the open and close state to generate a phase shift modulation signal, and enable the target current to be reduced based on the phase shift modulation signal, thereby ensuring that the inverter can not be disconnected from the power grid when the power grid is in the preset state, and the robustness of the inverter is guaranteed.

[0028] In certain embodiments of the present application, when the power grid is in the preset operating state, obtaining the current value of the target current includes:

[0029] When the power grid is in the preset operating state and the switch tube is in the open / closed state, the current value of the target current is obtained.

[0030] In this way, the inverter of the embodiment of the present application can obtain the current current value of the target current when the power grid is in a preset operating state and the switch tube is in the open or closed state, so as to determine whether the switch tube can be switched to the off state. The possibility of triggering overcurrent protection or even damage due to excessive target current when the switch tube is in the open or closed state is reduced to a certain extent, and the safe operation of the switch tube is guaranteed.

[0031] In certain embodiments of the present application, when the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes:

[0032] When the power grid is in the preset operating state, the switching frequency of the switch tube is increased to reduce the target current, wherein the switching frequency and the target current are negatively correlated.

[0033] In this way, the embodiment of the present application can reduce the target current by increasing the switching frequency, so that the reduction of the target current can be performed reliably.

[0034] In certain embodiments of the present application, when the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes:

[0035] When the power grid is in the preset operating state, the switch tube is controlled to switch to the off state to reduce the target current.

[0036] In this way, the inverter according to the embodiment of the present application can control the switch tube to switch to the off state when the power grid is in a preset operating state, so that the target current can be reliably reduced.

[0037] In certain embodiments of the present application, the target operating state information includes a target voltage of the output circuit, and the method further includes:

[0038] When the current voltage value of the target voltage is lower than the preset voltage value and the target voltage shows an upward trend within a preset time period, it is determined that the power grid is in the preset operating state, wherein the preset voltage value includes the lowest value of the target voltage when the power grid is in the preset operating state.

[0039] In this way, the implementation method of the present application can determine the operating status of the power grid based on the target voltage and the preset voltage value, and to a certain extent ensure the reliable determination of the preset operating status.

[0040] 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 above-mentioned control method is implemented.

[0041] An embodiment of the present application provides a photovoltaic system, which includes the inverter described above.

[0042] 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 control method is implemented.

[0043] The inverter, photovoltaic system, and computer-readable storage medium provided in the embodiments of the present application can control the switches in the input and output circuits to reduce the target current of the transformer when the power grid is in a preset operating state. For example, when the power grid voltage rises from a lower voltage to a rated value, the inverter can control the switches in the input and output circuits to reduce the target current of the transformer, thereby ensuring the stable operation of the inverter and photovoltaic system to a certain extent. The embodiments of the present application can also determine the operating state of the power grid based on the obtained target operating state information, so that the switches can be adjusted at the appropriate time, ensuring reliable control of the switches.

[0044] 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

[0045] 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:

[0046] FIG1 is a schematic flow chart of a control method in certain embodiments of the present application;

[0047] FIG2 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0048] FIG3 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0049] FIG4 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0050] FIG5 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0051] FIG6 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0052] FIG7 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0053] FIG8 is a flow chart of a control method in certain embodiments of the present application;

[0054] FIG9 is a flow chart of a control method in certain embodiments of the present application;

[0055] FIG10 is a schematic diagram of an application scenario of certain embodiments of the present application;

[0056] FIG11 is a flow chart of a control method in certain embodiments of the present application;

[0057] FIG12 is a flow chart of a control method in certain embodiments of the present application. DETAILED DESCRIPTION

[0058] 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.

[0059] 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.

[0060] 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 arrays) generate direct current (DC) from solar radiation. The inverter uses an internal transformer to convert the DC into alternating current (AC) with the same voltage and frequency as the grid, and then transmits the AC to the grid, thus completing the conversion of solar radiation into grid power and integrating it into the grid.

[0061] It is understood that when the photovoltaic system is in normal operating conditions, the grid operates at rated voltage. It is also understood that the rated voltage of the grid varies in different regions. For example, in some regions, the grid operates at a rated voltage of approximately 250V, while in other regions, the grid operates at a rated voltage of approximately 100V. Therefore, to maintain the normal operating conditions of the photovoltaic system, the inverter can convert the low-voltage direct current generated by the photovoltaic modules into the corresponding high-voltage alternating current. However, if the grid voltage in the photovoltaic system drops to a lower voltage or even zero due to occasional factors, such as lightning strikes, the inverter can convert the direct current generated by the photovoltaic modules into a lower reactive direct current to maintain the normal operation of itself and the photovoltaic modules, thereby avoiding grid disconnection, until the grid voltage gradually recovers from the lower voltage to the rated value. It is understood that the situation in which the grid voltage in the photovoltaic system is low and the inverter and photovoltaic modules continue to operate can be called a low voltage ride-through (LVRT) condition or a low-voltage ride-through condition.

[0062] During the period when the PV system recovers from low-voltage operation to normal operation, the inductive current of the transformer in the inverter may rise to a high value, causing the overcurrent protection of electronic components on the secondary side of the inverter, such as the switching diode, to be triggered, or even causing damage to the electronic components due to excessive inductive current.

[0063] Based on the above-mentioned possible problems, please refer to FIG1 . An embodiment of the present application provides a control method for an inverter. The inverter includes a transformer, an input circuit, and an output circuit. The input circuit and the output circuit each include a switching transistor. The transformer can transmit the target current generated by the photovoltaic power generation device through the input circuit to the power grid through the output circuit. The control method includes:

[0064] 01: Obtain the target operating status information of the output circuit to determine the operating status of the power grid;

[0065] 02: When the grid is in a preset operating state, the switch tube is controlled to reduce the target current. When the grid is in the preset operating state, the voltage peak of the grid is on an upward trend.

[0066] An embodiment of the present application provides a control device. The control method of the embodiment of the present application can be implemented by the control device of the embodiment of the present application. Specifically, the control device includes an acquisition module and a control module. The acquisition module acquires target operating state information of the output circuit to determine the operating state of the power grid. The control module is configured to control the switch tube to reduce the target current when the power grid is in a preset operating state, and when the power grid is in the preset operating state, the peak voltage of the power grid is on an upward trend.

[0067] The present application also provides an inverter, comprising a memory and a processor. The inverter position 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 target operating state information of the output circuit to determine the operating state of the power grid; when the power grid is in a preset operating state, the switch tube is controlled to reduce the target current, wherein, when the power grid is in the preset operating state, the voltage peak of the power grid is on an upward trend.

[0068] Specifically, when the inverter in the photovoltaic system performs phase-shift modulation normally and the photovoltaic power generation device is normal, but the power grid enters a low-power condition due to unexpected factors such as lightning strikes, the inductor current corresponding to the transformer may be a higher value.

[0069] To more clearly illustrate the implementation of the present application, please refer to Figures 2, 3 and 4. Figures 2, 3 and 4 are all schematic diagrams of application scenarios of certain implementations of the present application.

[0070] The photovoltaic system shown in Figure 2 includes photovoltaic panels, microinverters, and the power grid. The primary side of the microinverter is connected to the photovoltaic panels via an H-bridge circuit, and the secondary side is connected to the power grid via a bidirectional switch circuit. The primary and secondary sides are isolated by a transformer. The DC power output by the primary photovoltaic panels is boosted by the transformer to generate high-voltage AC power for input to the secondary power grid.

[0071] In the secondary-side bidirectional switch circuit, S5 and S6 form the upper-half bidirectional switch, while S7 and S8 form the lower-half bidirectional switch. When the grid voltage is greater than zero, S5 and S7 perform high-frequency chopping, while S6 and S8 pass directly. When the grid voltage is less than zero, S6 and S8 perform high-frequency chopping, while S5 and S7 pass directly.

[0072] 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 adjusting D1 and D2, the DC power output from the primary can be converted into AC power for the secondary input.

[0073] It should be noted that under the aforementioned low-through operating condition, since the control frequency of D1 and D2 may be lower than the switching frequency of the inverter, for example, the control frequency may be 10 kHz and the switching frequency may be 100 kHz, a situation may occur where the grid voltage at two control moments varies significantly, but D1 and D2 at two control moments do not change, resulting in a higher value of the inverter's inductor current.

[0074] For a clearer explanation, the photovoltaic system shown in FIG2 is equivalent to the circuit shown in FIG3. The photovoltaic power generation device 201 is connected to the power grid 203 through the inductor 202 (ie, the transformer). Then, as shown in FIG4, under normal working conditions, the voltage of the photovoltaic power generation device 201 is shown as the first line segment 301. The voltage is at the maximum value V dc and the minimum value V dc And, the voltage of the grid is shown as the second line segment 302, and the voltage is at the highest value V g1 and the minimum value -V g1 The secondary inductor current may be represented by a third line segment 303 .

[0075] However, during the low-pass recovery period, the phase shift angle remains unchanged within a switching frequency, as shown by the fourth curve 304, and the maximum value V of the voltage of the grid 202 is g1 Increase to V g2 , minimum value -V g1 Down to -V g2 , and the voltage of the photovoltaic power generation device 201 has not changed due to the phase shift angles D1 and D2, so the primary inductor current of the photovoltaic power generation device 201 acting on the inductor 202 remains unchanged as shown by the fifth line segment 305. Correspondingly, since the voltage of the grid 202 is V g1 Increase to V g2 , so the secondary inductor current changes from the third line segment 303 to the sixth line segment 306, that is, from L s1 becomes L s2 At the same time, according to the superposition principle, the current on the inductor 202 increases, resulting in excessive inductor current during the low-voltage wear-through and low-voltage wear-through recovery period, causing the transformer and other components in the inverter to enter overcurrent protection or be damaged.

[0076] Based on the above background, the embodiments of the present application provide a control method applicable to an inverter. Specifically, the inverter can use the target operating state information of the output circuit of the transformer to determine whether the power grid meets the state under the low voltage ride-through condition. When it is determined that the power grid is in a preset operating state, that is, when it is determined that the voltage peak of the power grid is on an upward trend, and thus when it is determined that the power grid state matches the voltage ride-through condition or the low voltage ride-through recovery condition, the inverter can control the switching tubes in the output circuit of the transformer and the switching tubes in the input circuit, thereby reducing the inductive current of the transformer, that is, the target current input to the transformer by the photovoltaic power generation device through the input circuit and output to the power grid by the transformer through the output circuit.

[0077] It is understood that the inverter in the embodiments of the present application may refer to the aforementioned 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.

[0078] It is also understood that the specific structure of the inverter in the embodiments of the present application, or in other words, the input circuit, output circuit, transformer, and switch tube in the inverter in the embodiments of the present application can be configured according to actual conditions. For example, in one example, the circuit structure with the transformer to the left and the photovoltaic module to the right (i.e., an H-bridge circuit) in FIG2 is the input circuit, while the circuit structure with the transformer to the right and the grid to the left (i.e., a bidirectional switch circuit) is the output circuit, and the switch tubes can be S1 to S8 in FIG2. Furthermore, the target current in the embodiments of the present application can be understood as the inductor current of the transformer.

[0079] It is understandable that, in addition to being applicable to the inverter in the scenario shown in FIG2 , the embodiments of the present application can also be applied to inverters of other structures or topologies. For example, please refer to FIG5 , FIG6 and FIG7 . Specifically, as shown in FIG5 , the input circuit of the transformer in the embodiment of the present application can be a half-bridge structure, and the output circuit of the transformer can be a bidirectional switch circuit structure. As shown in FIG6 , the input circuit in the embodiment of the present application can be an H-bridge structure, and the output circuit can be a full-bridge structure. As shown in FIG7 , the input circuit in the embodiment of the present application can be a half-bridge circuit structure, and the output circuit can be a full-bridge structure.

[0080] Furthermore, the target operating state information of the output-end circuit can be understood as information that can characterize the operating state of each component of the output-end circuit.

[0081] Furthermore, when it is determined based on the target operating status information that the power grid is in a preset operating state, or in other words, during the period when the photovoltaic system recovers from a low-voltage operating condition to a normal operating condition, the target current or inductor current of the transformer may increase. Therefore, in order to avoid excessive input current of the power grid, which may cause damage to its own electronic devices such as switching tubes, the inverter of the embodiment of the present application can control the switching tubes in the input circuit and the output circuit (such as S1 to S8 in Figure 2) to reduce the target inverter.

[0082] It is understood that the specific method for controlling the switch tube can be configured according to actual circumstances. For example, in some embodiments, when the grid is determined to be in a preset operating state, the inverter can trigger a blocking function based on internal hardware and pre-programmed firmware to stop the switch tube from operating, thereby reducing the target current to zero.

[0083] In summary, the inverter of the embodiment of the present application can control the switches in the input and output circuits to reduce the target current of the transformer when the grid is in a preset operating state. For example, when the grid voltage rises from a lower voltage to the rated value, the inverter can control the switches in the input and output circuits to reduce the target current of the transformer, thereby ensuring the stable operation of the inverter and photovoltaic system to a certain extent. The embodiment of the present application can also determine the operating state of the grid based on the obtained target operating state information, so that the switches can be adjusted at the appropriate time, ensuring reliable control of the switches.

[0084] In addition, in certain embodiments of the present application, when the power grid is in a preset operating state, the voltage peak of the power grid is on an upward trend, and the voltage peak of the power grid is less than a rated value.

[0085] Please refer to FIG8 . In certain embodiments of the present application, step 02 includes:

[0086] 020: When the power grid is in a preset operating state, obtain the current value of the target current;

[0087] 021: When the current value is greater than the preset current value, control the switch tube to reduce the target current, wherein the preset current value includes the minimum value of the target current when the power grid is in a preset operating state.

[0088] The control module of the embodiment of the present application is also used to obtain the current current value of the target current when the power grid is in a preset operating state, and to control the switch tube to reduce the target current when the current current value is greater than the preset current value. The preset current value includes the minimum value of the target current when the power grid is in the preset operating state.

[0089] The processor of the embodiment of the present application is also used to obtain the current current value of the target current when the power grid is in a preset operating state, and to control the switch tube to reduce the target current when the current current value is greater than the preset current value. The preset current value includes the minimum value of the target current when the power grid is in the preset operating state.

[0090] Specifically, in order to ensure reliable control of the switch tube in the embodiment of the present application, after obtaining the current current value of the target current, it can be determined whether the switch tube needs to be controlled based on the size of the current current value and the preset current value.

[0091] The preset current value is a priori knowledge, which is determined in advance through experiments to obtain the minimum value of the inductor current or the target current when the grid is in a low-breakdown recovery condition.

[0092] Furthermore, when the current value of the target current is greater than the preset current value, the inverter can control the switch tubes of the input circuit and the output circuit.

[0093] In this way, the inverter of the embodiment of the present application can obtain the current current value of the target current when the power grid is in a preset operating state, and control the switch tube when the current current value of the target current is greater than the preset current value, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0094] In certain embodiments of the present application, the target current includes the current primary inductance current of the transformer, the preset current value includes a first current threshold, and the first current threshold includes the minimum primary inductance current of the transformer when the grid is in a preset operating state. Furthermore, step 021 includes:

[0095] When the current primary inductor current is greater than the first current threshold, the switch tube is controlled to reduce the target current.

[0096] The control module in the embodiment of the present application is further configured to control the switch tube to reduce the target current when the current primary inductor current is greater than a first current threshold.

[0097] The processor in the embodiment of the present application is further configured to control the switch tube to reduce the target current when the current primary inductor current is greater than a first current threshold.

[0098] Specifically, the embodiment of the present application can determine that the devices in the inverter may be damaged due to excessively high target current when the current primary inductor current is greater than a pre-set first current threshold. Therefore, the inverter can control the switching tubes of the input circuit and the output circuit when the current primary inductor current is greater than the first current threshold.

[0099] The first current threshold is a priori knowledge, which is determined in advance through experiments to obtain the minimum value of the primary inductor current when the grid is in a low-breakdown recovery condition.

[0100] Furthermore, the primary inductor current in the embodiment of the present application can be understood as the primary input current of the transformer. In one example, the primary inductor current is i in FIG. p .

[0101] In this way, the inverter of the embodiment of the present application can obtain the current primary inductor current when the power grid is in a preset operating state, and control the switch tube when the current primary inductor current is greater than the first current threshold, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0102] In certain embodiments of the present application, the target current includes the current primary inductance current of the transformer, the preset current value includes a first current threshold, and the first current threshold includes the minimum primary inductance current of the transformer when the grid is in a preset operating state. Furthermore, step 021 includes:

[0103] When the current primary inductor current is greater than the first current threshold, the switch tube is controlled to reduce the target current.

[0104] The control module in the embodiment of the present application is further configured to control the switch tube to reduce the target current when the current primary inductor current is greater than a first current threshold.

[0105] The processor in the embodiment of the present application is further configured to control the switch tube to reduce the target current when the current primary inductor current is greater than a first current threshold.

[0106] Specifically, the implementation manner of the present application can determine that the devices in the inverter may be damaged due to excessively high target current when the current secondary inductor current is greater than a pre-set second current threshold. Therefore, the inverter can control the switching tubes of the input circuit and the output circuit when the current secondary inductor current is greater than the second current threshold.

[0107] The second current threshold is a priori knowledge, which is determined in advance through experiments to obtain the minimum value of the secondary inductor current when the grid is in a low-breakdown recovery condition.

[0108] Furthermore, the secondary inductor current in the embodiment of the present application can be understood as the secondary input current of the transformer. In one example, the secondary inductor current is i in FIG. s .

[0109] In this way, the inverter of the embodiment of the present application can obtain the current secondary inductor current when the power grid is in a preset operating state, and control the switch tube when the current secondary inductor current is greater than the second current threshold, so that the switch tube can be controlled at a reasonable time to a certain extent.

[0110] In certain embodiments of the present application, step 021 includes:

[0111] When the current value is greater than the preset current value, the switch tube is controlled to switch to the off state to reduce the target current.

[0112] The control module of the embodiment of the present application is further configured to control the switch tube to switch to an off state to reduce the target current when the current current value is greater than a preset current value.

[0113] The processor of the embodiment of the present application is also used to control the switch tube to switch to the off state to reduce the target current when the current current value is greater than the preset current value.

[0114] Specifically, the implementation method of the present application is to avoid the inductor current or target current being too high, which may cause damage to the components in the inverter or trigger overcurrent protection. Therefore, when it is confirmed that the current current value of the target current is greater than the preset current value, all switching tubes in the input circuit and the output current can be controlled to enter the off state.

[0115] It should be noted that when all the switching tubes in the input circuit and the output current enter the off state, the inverter can be considered to have entered the wave-blocking mode, so the sum of the current of the primary winding and the current of the secondary winding of the transformer can be 0, or in other words, the primary inductor current and the secondary inductor current can be 0, thereby achieving a reduction in the target current.

[0116] In this way, the inverter of the embodiment of the present application can control the switch tubes in the input circuit and the output circuit to switch to the off state when the current current value of the target current is greater than the preset current value, so that the inverter itself is blocked, thereby achieving a reduction in the target current.

[0117] In some embodiments of the present application, the switch tube can be used to generate a phase-shift modulation signal, and step 021 includes:

[0118] When the duration of the switch tube being in the off state meets the preset duration, the switch tube is controlled to switch to the on-off state, and the phase-shift modulation signal generated by the switch tube is controlled according to the output end information to reduce the target current.

[0119] The control module of the embodiment of the present application is also used to control the switch tube to switch to the open and close state when the duration of the switch tube in the off state meets the preset duration, and control the phase shift modulation signal generated by the switch tube according to the output end information to reduce the target current.

[0120] The processor of the embodiment of the present application is also used to control the switch tube to switch to the open and close state when the duration of the switch tube in the off state meets the preset duration, and control the phase-shift modulation signal generated by the switch tube according to the output end information to reduce the target current.

[0121] Specifically, to prevent the inverter from being disconnected from the power grid, or in other words, to prevent the inverter from being disconnected from the grid, the inverter can control each switch in the input circuit and the output circuit to switch to an on-off state when each switch is in an off state for a certain period of time, so that the switch can operate normally. Specifically, when each switch is in an on-off state, the inverter of the embodiment of the present application can control the opening and closing of each switch to achieve phase-shift modulation.

[0122] Therefore, the inverter can control each switch tube to generate a corresponding phase-shift modulation signal, thereby reducing the target current due to the phase-shift modulation signal.

[0123] Optionally, in certain embodiments of the present application, the inverter may obtain the voltages on both sides of the grid and the voltages on both sides of the photovoltaic power generation device to control each switch tube to generate a phase-shift modulation signal.

[0124] In this way, the inverter of the embodiment of the present application can control the switch tube to switch to the open and close state when the duration of the switch tube in the off state meets the preset duration, and then perform phase shift modulation through the switch tube in the open and close state to generate a phase shift modulation signal, and enable the target current to be reduced based on the phase shift modulation signal, thereby ensuring that the inverter can not be disconnected from the power grid when the power grid is in the preset state, and the robustness of the inverter is guaranteed.

[0125] In certain embodiments of the present application, step 021 includes:

[0126] When the power grid is in a preset operating state and the switch tube is in an open or closed state, the current value of the target current is obtained.

[0127] The control module of the embodiment of the present application is also used to obtain the current value of the target current when the power grid is in a preset operating state and the switch tube is in an open or closed state.

[0128] The processor of the embodiment of the present application is also used to obtain the current value of the target current when the power grid is in a preset operating state and the switch tube is in an open or closed state.

[0129] To more clearly illustrate the embodiments of the present application, please refer to FIG9 , which is a flow chart of a control method in certain embodiments of the present application.

[0130] That is, as shown in FIG9 , when the inverter determines that the grid is in a preset state, the current value of the target current may be obtained to determine whether the current current value is higher than the preset current value.

[0131] If so, the inverter can control each switch tube in the input circuit and the output circuit to enter the off state to block the wave.

[0132] When the switch tube maintains the off state for a predetermined time period, the inverter can control each switch tube in the input circuit and the output circuit to enter the on-off state to release the wave blocking, and then perform phase shift modulation to generate the wave.

[0133] After completing the phase shift modulation, the inverter can determine whether the current state of the grid is the preset state. If so, the current current value of the target current is obtained again to determine whether the current current value is higher than the preset current value. If not, the process ends.

[0134] Optionally, in certain embodiments of the present application, the inverter may be controlled in a manner as shown in FIG9 so that the change in the inductor current or the target current is as shown in FIG10 , which is a schematic diagram of an application scenario in certain embodiments of the present application.

[0135] In this way, the inverter of the embodiment of the present application can obtain the current current value of the target current when the power grid is in a preset operating state and the switch tube is in the open or closed state, so as to determine whether the switch tube can be switched to the off state. The possibility of triggering overcurrent protection or even damage due to excessive target current when the switch tube is in the open or closed state is reduced to a certain extent, and the safe operation of the switch tube is guaranteed.

[0136] In certain embodiments of the present application, step 021 includes:

[0137] When the power grid is in a preset operating state, the switching frequency of the switch tube is increased to reduce the target current, wherein the switching frequency and the target current are negatively correlated.

[0138] The control module of the embodiment of the present application is also used to increase the switching frequency of the switch tube to reduce the target current when the power grid is in a preset operating state, and the switching frequency and the target current are negatively correlated.

[0139] The processor of the embodiment of the present application is also used to increase the switching frequency of the switch tube to reduce the target current when the power grid is in a preset operating state, and the switching frequency and the target current are negatively correlated.

[0140] Specifically, based on prior knowledge, it is determined that the switching frequency of the switch tube is negatively correlated with the target current, so the inverter can reduce the target current by increasing the switching frequency of the switch tube.

[0141] Optionally, in certain embodiments of the present application, the increase in switching frequency may refer to the following formula, namely:

[0142] Where, f s represents the switching frequency of the inverter, i L Indicates the preset current value, u g Indicates the output voltage converted to the primary side through the transformer turns ratio, u dc Indicates the input voltage.

[0143] It is understood that the input voltage in the embodiment of the present application can be the voltage on both sides of the photovoltaic module (corresponding to the photovoltaic power generation device) in Figure 2 and Figures 5 to 7, or the capacitor C bus The voltage on both sides can also be v in Figure 2 and Figures 5 to 7 p .

[0144] Correspondingly, the output voltage in the embodiment of the present application can be the voltage on both sides of the grid in FIG2 and FIG5 to 7, or the voltage on both sides of the capacitor C1 and / or C2, or v in FIG2 and FIG5 to 7. s .

[0145] Also, when the output voltage is the voltage on both sides of the grid, the inverter can obtain the output voltage by collecting the instantaneous value of the voltage on both sides of the grid, or by collecting the maximum value that the fundamental voltage of the grid can reach in one cycle to obtain the output voltage.

[0146] 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.

[0147] 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.

[0148] It is understood that after obtaining a target switching frequency value using the above formula, the inverter can increase the switching frequency to the target value, thereby reducing the target current to a preset current value. It is understood that the preset current value includes the maximum value of the target current when the grid is not in a preset operating state.

[0149] Optionally, in certain embodiments of the present application, please refer to FIG11 for details, which is a flow chart of the control method in certain embodiments of the present application. That is, the inverter of the embodiment of the present application can control or increase the switching frequency of the switch tube when it detects that the power grid is in a preset state, thereby reducing the target current. Furthermore, after completing the control of the switching frequency, the inverter can detect whether the power grid is in a normal operating state. If so, the switching frequency is restored to the state before the power grid entered the preset operating state. Otherwise, the switching frequency is controlled according to the actual situation.

[0150] Optionally, in certain embodiments of the present application, the inverter may increase the switching frequency to reduce the target current, so that the target current changes as shown in FIG10 .

[0151] In this way, the embodiment of the present application can reduce the target current by increasing the switching frequency, so that the reduction of the target current can be performed reliably.

[0152] In certain embodiments of the present application, step 021 includes:

[0153] When the grid is in a preset operating state, the switch tube is controlled to switch to the off state to reduce the target current.

[0154] The control module of the embodiment of the present application is also used to control the switch tube to switch to the off state to reduce the target current when the power grid is in a preset operating state.

[0155] The processor in the embodiment of the present application is also used to control the switch tube to switch to the off state to reduce the target current when the power grid is in a preset operating state.

[0156] To more clearly illustrate the embodiments of the present application, please refer to Figure 12, which is a flow chart illustrating a control method in certain embodiments of the present application. Specifically, to avoid damage to components in the inverter or overcurrent protection, the embodiments of the present application, when determining that the power grid is in a preset operating state, control each switch in the input circuit and the output circuit to switch to the off state to achieve inverter blocking, thereby reducing the target current.

[0157] Furthermore, when it is confirmed that the power grid is in a normal operating state, each switch tube in the input circuit and the output circuit is controlled to switch to an open or closed state to release the inverter blocking wave.

[0158] Optionally, in certain embodiments of the present application, the inverter can control the switch tube to switch to the off state when the grid is in a preset operating state, and control the switch tube to switch to the open and close state when the grid is in a normal operating state, so that the target current changes as shown in Figure 10.

[0159] In this way, the inverter according to the embodiment of the present application can control the switch tube to switch to the off state when the power grid is in a preset operating state, so that the target current can be reliably reduced.

[0160] In certain embodiments of the present application, the target operating state information includes a target voltage of the output circuit, and the control method further includes:

[0161] When the current voltage value of the target voltage is lower than the preset voltage value and the target voltage shows an upward trend within a preset time period, it is determined that the power grid is in a preset operating state, wherein the preset voltage value includes the lowest value of the target voltage when the power grid is in the preset operating state.

[0162] The control device of the embodiment of the present application further includes a determination module. The determination module is configured to determine that the power grid is in a preset operating state when a current target voltage value is lower than a preset voltage value and the target voltage shows an upward trend within a preset time period, wherein the preset voltage value includes a minimum value of the target voltage when the power grid is in the preset operating state.

[0163] The processor of the embodiment of the present application is also used to determine that the power grid is in a preset operating state when the current voltage value of the target voltage is lower than the preset voltage value and the target voltage shows an upward trend within a preset time period, wherein the preset voltage value includes the lowest value of the target voltage when the power grid is in the preset operating state.

[0164] To more clearly illustrate the embodiment of the present application, please refer to FIG2 and FIG5 to 7. That is, the target voltage in the embodiment of the present application can be the voltage on both sides of the grid, or the voltage on both sides of the capacitor C1 and / or C2, or v s .

[0165] Therefore, in the embodiment of the present application, when the target voltage is lower than the preset voltage value and it is determined that the target voltage continues to rise for a period of time, it can be determined that the power grid is in the preset operating state. The preset voltage value may include the rated voltage of the power grid.

[0166] It is understandable that when the target voltage is the voltage across C1 or the voltage across C2, the preset voltage value may be half of the rated voltage of the grid.

[0167] In this way, the implementation method of the present application can determine the operating status of the power grid based on the target voltage and the preset voltage value, and to a certain extent ensure the reliable determination of the preset operating status.

[0168] Optionally, in certain embodiments of the present application, the inverter can determine whether the grid is in a preset operating state by the voltage on the power generation side. Taking Figure 2 and Figures 5 to 7 as examples, the voltage on the power generation side can be the voltage on both sides of the photovoltaic module (corresponding to the photovoltaic power generation device), or it can be the voltage on the capacitor C bus The voltage on both sides can also be v in Figure 2 and Figures 5 to 7 p Furthermore, when the voltage on the power generation side is greater than a preset value, the inverter may consider the current operating state of the power grid to be the preset operating state.

[0169] An embodiment of the present application further provides a photovoltaic system, which includes the above-mentioned inverter.

[0170] The embodiments of the present application further provide a computer-readable storage medium storing a computer program, which implements the above-mentioned control method when the computer program is executed by one or more processors.

[0171] 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.

[0172] 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.

[0173] 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 control method for an inverter, characterized in that: The inverter includes a transformer, an input circuit, and an output circuit. The input circuit and the output circuit each include a switch tube. The transformer can output the target current input by the photovoltaic power generation device through the input circuit to the power grid through the output circuit. The method includes: Acquiring target operating state information of the output end circuit to determine the operating state of the power grid; When the power grid is in a preset operating state, the switch tube is controlled to reduce the target current, wherein when the power grid is in the preset operating state, the voltage peak of the power grid is on an upward trend.

2. The method according to claim 1, characterized in that When the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes: When the power grid is in the preset operating state, obtaining a current value of the target current; When the current current value is greater than a preset current value, the switch tube is controlled to reduce the target current, wherein the preset current value includes a minimum value of the target current when the power grid is in the preset operating state.

3. The method according to claim 2, characterized in that The target current includes the current primary inductance current of the transformer, the preset current value includes a first current threshold, the first current threshold includes the minimum primary inductance current of the transformer when the power grid is in the preset operating state, and when the current current value is greater than the preset current value, controlling the switch tube to reduce the target current includes: When the current primary inductor current is greater than a first current threshold, the switch tube is controlled to reduce the target current.

4. The method according to claim 2, characterized in that The target current includes a current secondary inductor current of the transformer, the preset current value includes a second current threshold, the second current threshold includes a minimum secondary inductor current of the transformer when the power grid is in the preset operating state, and when the current current value is greater than the preset current value, controlling the switch to reduce the target current includes: When the current secondary-side inductor current is greater than a second current threshold, the switch tube is controlled to reduce the target current.

5. The method according to claim 2, characterized in that When the current current value is greater than the preset current value, controlling the switch tube to reduce the target current includes: When the current value is greater than the preset current value, the switch tube is controlled to switch to an off state to reduce the target current.

6. The method according to claim 5, characterized in that The switch tube can be used to generate a phase-shift modulation signal, and when the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes: When the duration of the switch tube being in the off state meets the preset duration, the switch tube is controlled to switch to the on-off state, and the phase-shift modulation signal generated by the switch tube is controlled according to the output end information to reduce the target current.

7. The method according to claim 6, characterized in that The step of obtaining the current value of the target current when the power grid is in the preset operating state includes: When the power grid is in the preset operating state and the switch tube is in the open / closed state, the current value of the target current is obtained.

8. The method according to claim 1, characterized in that When the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes: When the power grid is in the preset operating state, the switching frequency of the switch tube is increased to reduce the target current, wherein the switching frequency and the target current are negatively correlated.

9. The method according to claim 1, characterized in that When the power grid is in a preset operating state, controlling the switch tube to reduce the target current includes: When the power grid is in the preset operating state, the switch tube is controlled to switch to the off state to reduce the target current.

10. The method according to claim 1, characterized in that The target operating state information includes a target voltage of the output circuit, and the method further includes: When the current voltage value of the target voltage is lower than the preset voltage value and the target voltage shows an upward trend within a preset time period, it is determined that the power grid is in the preset operating state, wherein the preset voltage value includes the lowest value of the target voltage when the power grid is in the preset operating state.

11. An inverter, characterized in that: The method comprises 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 method according to any one of claims 1 to 10 is implemented.

12. A photovoltaic system, characterized in that: The photovoltaic system includes the inverter according to claim 11.

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