Control methods, controllers and photovoltaic systems

Abstract

This application provides a control method, controller, and photovoltaic system. The method, applied to a photovoltaic system connected to a power grid, includes: determining whether the power grid is in a high-voltage or low-voltage state; when the power grid is in a high-voltage state, adjusting a derating factor according to a first voltage to control the active power output of the photovoltaic system to not exceed a first power limit, wherein the first voltage is the bus voltage of the photovoltaic system, and the derating factor is used to adjust the voltage feedback value of the bus voltage loop, the voltage feedback value decreasing as the derating factor decreases; when the power grid is in a low-voltage state, adjusting the derating factor according to the ratio of the first voltage and a second voltage to control the active power output of the photovoltaic system to not exceed a second power limit, wherein the second voltage is the grid voltage. This application can improve the operational reliability of both the photovoltaic system and the power grid.

Description

Technical Field

[0001] This application relates to the field of photovoltaic control technology, and in particular to a control method, controller and photovoltaic system. Background Technology

[0002] When a photovoltaic (PV) system is connected to the power grid, in some situations, such as excessive nonlinear loads on the lines or excessively high line impedance, the power grid may be in a weak grid state, with poor disturbance immunity. In a weak grid state, if the grid requests the PV system to output active power to support it when the grid voltage is abnormal, the output power may fluctuate due to voltage fluctuations in the PV system, potentially further exacerbating grid disturbances and affecting the operational reliability of both the PV system and the power grid.

[0003] This application provides a control method to ensure the operational reliability of photovoltaic systems and the power grid under weak grid conditions. Summary of the Invention

[0004] This application provides a control method, controller, and photovoltaic system to ensure the reliability of the photovoltaic system and the power grid under weak grid conditions.

[0005] In a first aspect, embodiments of this application provide a control method applied to a photovoltaic system connected to a power grid, comprising:

[0006] To determine whether the power grid is in a high-voltage or low-voltage state, a high-voltage state is when the grid voltage is greater than the grid's rated maximum voltage, and a low-voltage state is when the grid voltage is less than the grid's rated minimum voltage.

[0007] When the power grid is under high voltage, the derating factor is adjusted according to the first voltage to control the active power output of the photovoltaic system to not exceed the first limit power. The first voltage is the bus voltage of the photovoltaic system. The derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases.

[0008] When the power grid is in a low-voltage state, the derating factor is adjusted according to the ratio of the first voltage and the second voltage to control the active power output of the photovoltaic system to not exceed the second limit power, where the second voltage is the grid voltage.

[0009] In one possible implementation, adjusting the derating factor based on the first voltage includes:

[0010] When the first voltage exceeds the preset voltage, the derating factor is reduced until the first voltage does not exceed the preset voltage.

[0011] In one possible implementation, after controlling the reduction factor to decrease, the control method further includes:

[0012] If the power grid returns from a high-voltage state to a normal state, the derating factor is restored to the default value.

[0013] In one possible implementation, adjusting the derating factor based on the ratio of the first voltage to the second voltage includes:

[0014] When the ratio exceeds the preset ratio, the reduction coefficient is controlled to decrease until the ratio does not exceed the preset ratio.

[0015] In one possible implementation, after controlling the reduction factor to decrease, the control method further includes:

[0016] If the power grid returns from a low-voltage state to a normal state, the derating factor is restored to its default value.

[0017] In one possible implementation, determining whether the power grid is in a high-voltage or low-voltage state includes:

[0018] Upon receiving an active power request from the power grid, the system obtains the grid voltage and determines whether the grid is in a high-voltage or low-voltage state based on the grid voltage.

[0019] Secondly, this application provides a control device for use in a photovoltaic system connected to the power grid, comprising:

[0020] The judgment module is used to determine whether the power grid is in a high-voltage state or a low-voltage state. The high-voltage state is the working state in which the power grid voltage is greater than the rated maximum voltage of the power grid, and the low-voltage state is the working state in which the power grid voltage is less than the rated minimum voltage of the power grid.

[0021] The first control module is used to adjust the derating factor according to the first voltage when the power grid is in a high voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power. The first voltage is the bus voltage of the photovoltaic system. The derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases.

[0022] The second control module is used to adjust the derating factor according to the ratio of the first voltage and the second voltage when the grid is in a low voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power. The second voltage is the grid voltage.

[0023] Thirdly, embodiments of this application provide a controller, including a memory and a processor. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the steps of the control method as described in the first aspect or any possible implementation of the first aspect.

[0024] Fourthly, embodiments of this application provide a photovoltaic system including the controller described in the third aspect above.

[0025] Fifthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the control method as described in the first aspect or any possible implementation of the first aspect.

[0026] This application provides a control method, controller, and photovoltaic system. When the power grid is under high voltage, the derating factor is adjusted according to the photovoltaic system's bus voltage to reduce the photovoltaic system's output power, ensuring that the photovoltaic system's bus voltage is not raised and avoiding the impact of high active power output on grid stability. When the power grid is under low voltage, the derating factor is adjusted according to the ratio of the bus voltage to the grid voltage to lower the bus voltage, avoiding the impact of high active power output on grid stability and ensuring the operational reliability of both the power grid and the photovoltaic system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the photovoltaic system provided in the embodiments of this application;

[0029] Figure 2 This is a flowchart illustrating the implementation of the control method provided in the embodiments of this application;

[0030] Figure 3 This is a schematic diagram of the control device provided in the embodiments of this application;

[0031] Figure 4 This is a schematic diagram of the controller provided in an embodiment of this application. Detailed Implementation

[0032] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following description will be provided in conjunction with the accompanying drawings and specific embodiments.

[0034] Figure 1This is a schematic diagram of the photovoltaic system provided in the embodiments of this application, as shown below. Figure 1 As shown, a photovoltaic system may include a photovoltaic module, a DC / DC module, and a DC / AC module connected in sequence. The other end of the DC / AC module is connected to the power grid.

[0035] In the embodiments of this application, the DC bus between the DC / DC module and the DC / AC module is the bus of the photovoltaic system, and the connection point between the DC / AC module and the power grid is the grid connection point of the photovoltaic system and the power grid.

[0036] When a photovoltaic (PV) system is connected to the power grid, the grid's resilience is poor in weak grid conditions. When the grid is in an abnormal state, fluctuations in the voltage at the grid connection point can affect the PV system's active power output, potentially exacerbating grid fluctuations and impacting the reliability of both the grid and the PV system.

[0037] This application provides a control method for a photovoltaic system to address the problem of mutual interference between the power grid and the photovoltaic system under weak grid conditions.

[0038] See Figure 2 The diagram illustrates the implementation flowchart of the control method provided in the embodiments of this application. Figure 2 As shown, a control method applied to a photovoltaic system connected to the power grid may include S101 to S103.

[0039] S101 determines whether the power grid is in a high-voltage or low-voltage state. A high-voltage state is when the power grid voltage is greater than the rated maximum voltage of the power grid, and a low-voltage state is when the power grid voltage is less than the rated minimum voltage of the power grid.

[0040] The execution entity in this application embodiment can be the main controller of the photovoltaic system or the controller of the inverter in the photovoltaic system.

[0041] This application embodiment can monitor the voltage of the power grid. When the power grid voltage is greater than the rated maximum voltage, the power grid can be determined to be in a high-voltage state. When the power grid voltage is less than the rated minimum voltage, the power grid can be determined to be in a low-voltage state. When the power grid voltage is less than or equal to the rated maximum voltage and greater than or equal to the rated minimum voltage, the power grid can be determined to be in a normal state. Both high-voltage and low-voltage states are abnormal states of the power grid.

[0042] Optionally, the system can determine in real time whether the power grid is in a high-voltage or low-voltage state. Alternatively, it can determine whether the power grid is in a high-voltage or low-voltage state upon receiving an active power request from the grid. Here, the active power request indicates that the grid is requesting the photovoltaic system to output active power.

[0043] S102, when the power grid is under high voltage, the derating factor is adjusted according to the first voltage to control the active power output of the photovoltaic system to not exceed the first limit power. The first voltage is the bus voltage of the photovoltaic system. The derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases.

[0044] When the grid voltage exceeds the grid's rated maximum voltage, it indicates that the grid is under high voltage. When the grid is under high voltage, the voltage at the grid connection point of the photovoltaic system may be boosted, leading to an increase in the photovoltaic system's bus voltage and affecting its stability. The increased bus voltage, in turn, leads to increased active power output. In weak grid conditions, the grid's immunity to interference is poor, which in turn affects its stability. Ultimately, this results in a decrease in the operational reliability of both the grid and the photovoltaic system.

[0045] When the power grid is under high voltage, the derating factor can be adjusted according to the first voltage to reduce the active power output of the photovoltaic system and avoid excessively high bus voltage of the photovoltaic system.

[0046] The bus voltage of the photovoltaic system is regulated by a bus voltage loop. This loop adjusts the bus voltage based on the voltage feedback value and the given bus voltage to prevent it from becoming too high or too low. When the voltage feedback value increases, the bus voltage increases; when the voltage feedback value decreases, the bus voltage decreases. The bus voltage can be reduced by adjusting the derating factor.

[0047] In practical applications, bus voltage is directly proportional to active power. When bus voltage increases, the active power output of the photovoltaic system increases; when bus voltage decreases, the active power output of the photovoltaic system decreases. Therefore, by adjusting the derating factor, the bus voltage can be adjusted, thereby adjusting the active power output of the photovoltaic system. That is, the active power output of the photovoltaic system decreases as the derating factor decreases.

[0048] In the embodiments of this application, the first voltage is the bus voltage of the photovoltaic system. If the first voltage is too high, it may cause the output active power of the photovoltaic system to be too high. At this time, the derating factor can be adjusted to limit the first voltage, thereby ensuring that the output active power of the photovoltaic system does not exceed the first limit power. The first limit power is the maximum allowable output active power of the photovoltaic system under high grid voltage conditions. Alternatively, the first limit power is a power value that is less than the maximum allowable output active power of the photovoltaic system under high grid voltage conditions.

[0049] S103 When the grid is in a low-voltage state, the derating factor is adjusted according to the ratio of the first voltage and the second voltage to control the active power output of the photovoltaic system to not exceed the second limit power, where the second voltage is the grid voltage.

[0050] In the embodiments of this application, the ratio of the first voltage and the second voltage can be referred to as the voltage differential coefficient. When the grid voltage is less than the grid's rated minimum voltage, it indicates that the grid is under low voltage. When the bus voltage and grid voltage are normal, the voltage differential coefficient is within the normal range. When the grid is under low voltage, the bus voltage will normally also decrease to ensure that the voltage differential coefficient is within the normal range. However, if the voltage differential coefficient increases, it indicates that the bus voltage has increased or remained unchanged, which may lead to an increase in the active power output of the photovoltaic system, thereby disturbing the grid. Grid fluctuations, in turn, affect the stability of the photovoltaic system, ultimately leading to a decrease in the operational reliability of both the grid and the photovoltaic system.

[0051] When the power grid is under low voltage and the voltage drop factor is too high, the derating factor can be adjusted to reduce the bus voltage of the photovoltaic system, thereby ensuring that the active power output of the photovoltaic system does not exceed the second limiting power. The second limiting power is the maximum permissible active power output of the photovoltaic system under low grid voltage conditions. Alternatively, the second limiting power is the power value of the photovoltaic system that is less than the maximum permissible active power output under low grid voltage conditions.

[0052] This application embodiment reduces the output power of the photovoltaic system by adjusting the derating factor based on the bus voltage when the power grid is under high voltage, ensuring that the bus voltage of the photovoltaic system is not raised and avoiding the impact of high active power output on grid stability. When the power grid is under low voltage, the derating factor is adjusted according to the ratio of the bus voltage to the grid voltage to lower the bus voltage, avoiding the impact of high active power output on grid stability and ensuring the operational reliability of the power grid and the photovoltaic system.

[0053] In some embodiments of this application, the "adjusting the derating factor according to the first voltage" in S102 above may include:

[0054] When the first voltage exceeds the preset voltage, the derating factor is reduced until the first voltage does not exceed the preset voltage.

[0055] When the first voltage does not exceed the preset voltage, the derating factor remains unchanged.

[0056] When the grid voltage is greater than the grid's rated maximum voltage, the grid voltage is in a high-voltage state. At this time, if the bus voltage exceeds the preset voltage, it indicates that the bus voltage is too high. In this case, the derating factor can be gradually reduced to lower the bus voltage until it does not exceed the preset voltage, thereby controlling the active power output of the photovoltaic system to not exceed the first limit power.

[0057] Optionally, the derating factor can be gradually and linearly reduced until the bus voltage does not exceed the preset voltage. Alternatively, the derating factor can be gradually reduced according to a preset reduction value until the bus voltage does not exceed the preset voltage. The specific choice can be made based on the actual situation.

[0058] In this embodiment, when the first voltage exceeds a preset voltage and the duration of the first voltage exceeding the preset voltage exceeds a first preset duration, the derating factor can be controlled to decrease until the first voltage does not exceed the preset voltage.

[0059] When the first voltage exceeds the preset voltage, but the duration of the first voltage exceeding the preset voltage does not exceed the first preset duration, the derating factor remains unchanged.

[0060] In the embodiments of this application, when the power grid is in a normal state, the derating factor is set to a default value. When the power grid is in a high-voltage state, the derating factor can be controlled to gradually decrease from the default value. The default value can be 1.

[0061] This application embodiment gradually controls the derating factor to decrease when the power grid is under high voltage, thereby reducing the bus voltage and the active power output of the photovoltaic system, and maintaining the stability of the power grid and the photovoltaic system.

[0062] In some embodiments of this application, after controlling the reduction factor to decrease, the control method may further include:

[0063] If the power grid returns from a high-voltage state to a normal state, the derating factor is restored to the default value.

[0064] The normal operating condition is when the grid voltage is not less than the grid's rated minimum voltage and not greater than the grid's rated maximum voltage.

[0065] After the derating factor is reduced, if the power grid returns from a high-voltage state to a normal state, it indicates that the grid voltage has returned to normal. The voltage at the grid connection point between the photovoltaic system and the grid has returned from high voltage to normal voltage. The voltage feedback value of the bus voltage loop decreases. At this time, the derating factor can be gradually increased to the default value to avoid the bus voltage being too low.

[0066] This application embodiment, by adjusting the derating factor back to the default value after the power grid returns to normal, can minimize power grid fluctuations and ensure the operational reliability of both the photovoltaic system and the power grid.

[0067] In some embodiments of this application, the "adjusting the derating factor according to the ratio of the first voltage and the second voltage" in S103 above may include:

[0068] When the ratio exceeds the preset ratio, the reduction coefficient is controlled to decrease until the ratio does not exceed the preset ratio.

[0069] If the ratio does not exceed the preset ratio, the reduction factor remains unchanged.

[0070] When the grid voltage is lower than the grid's rated minimum voltage, the grid voltage is in a low-voltage state. At this time, if the ratio of the bus voltage to the grid voltage exceeds the preset ratio, it indicates that the bus voltage is relatively too high. In this case, the derating factor can be gradually reduced to lower the bus voltage until the ratio of the bus voltage to the grid voltage does not exceed the preset ratio, so as to control the active power output of the photovoltaic system to not exceed the second limit power.

[0071] Optionally, the derating factor can be gradually and linearly reduced until the ratio of the bus voltage to the grid voltage does not exceed a preset value. Alternatively, the derating factor can be gradually reduced according to a preset reduction value until the ratio of the bus voltage to the grid voltage does not exceed a preset value. The specific choice can be made based on the actual situation.

[0072] In this embodiment of the application, when the ratio of the first voltage to the second voltage exceeds a preset ratio and the duration for which the ratio of the first voltage to the second voltage exceeds the preset ratio exceeds a second preset duration, the derating factor is controlled to decrease until the ratio of the first voltage to the second voltage does not exceed the preset ratio.

[0073] When the first voltage exceeds the preset voltage, but the duration of the first voltage exceeding the preset voltage does not exceed the first preset duration, the derating factor remains unchanged.

[0074] This application embodiment gradually controls the derating factor to decrease when the power grid is under low voltage conditions, thereby reducing the bus voltage and the active power output of the photovoltaic system, and maintaining the stability of the power grid and the photovoltaic system.

[0075] In some embodiments of this application, after controlling the reduction factor to decrease, the control method further includes:

[0076] If the power grid returns from a low-voltage state to a normal state, the derating factor is restored to its default value.

[0077] After the derating factor is reduced, if the power grid returns to normal from a low-voltage state, the derating factor can be gradually increased to the default value to ensure that the ratio of the bus voltage to the grid voltage does not exceed the preset ratio.

[0078] This application embodiment, by adjusting the derating factor back to the default value after the power grid returns to normal, can minimize power grid fluctuations and ensure the operational reliability of both the photovoltaic system and the power grid.

[0079] In some embodiments of this application, the "determining whether the power grid is in a high-voltage or low-voltage state" in S101 above may include:

[0080] Upon receiving an active power request from the power grid, the system obtains the grid voltage and determines whether the grid is in a high-voltage or low-voltage state based on the grid voltage.

[0081] When no active power request is received from the power grid, the grid voltage is not acquired and the power grid operating status is not determined.

[0082] When the power grid needs the active power from the photovoltaic (PV) system, it can send an active power request to the PV system. Upon receiving the active power request, the PV system can obtain the grid voltage and determine the current operating status of the grid.

[0083] When the grid voltage is greater than the grid's rated maximum voltage, the grid is considered to be in a high-voltage state. When the grid voltage is less than the grid's rated minimum voltage, the grid is considered to be in a low-voltage state.

[0084] In this embodiment, the corresponding control logic is executed only when a power request is received from the power grid, so as to maintain the stability of the power grid and the photovoltaic system and avoid mutual interference between the photovoltaic system and the power grid under weak grid conditions.

[0085] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0086] The following are device embodiments of this application. For details not described in detail, please refer to the corresponding method embodiments described above.

[0087] Figure 3 A schematic diagram of the control device provided in an embodiment of this application is shown. For ease of explanation, only the parts related to the embodiment of this application are shown, and are described in detail below:

[0088] like Figure 3 As shown, the control device 20 is applied to a photovoltaic system connected to the power grid. The control device includes:

[0089] The judgment module 201 is used to determine whether the power grid is in a high-voltage state or a low-voltage state. The high-voltage state is the working state in which the power grid voltage is greater than the rated maximum voltage of the power grid, and the low-voltage state is the working state in which the power grid voltage is less than the rated minimum voltage of the power grid.

[0090] The first control module 202 is used to adjust the derating factor according to the first voltage when the power grid is in a high voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power. The first voltage is the bus voltage of the photovoltaic system, and the derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases.

[0091] The second control module 203 is used to adjust the derating factor according to the ratio of the first voltage and the second voltage when the power grid is in a low-voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power. The second voltage is the grid voltage. It may include:

[0092] In some embodiments of this application, the first control module 202 is further configured to control the derating factor to decrease when the first voltage exceeds the preset voltage, until the first voltage does not exceed the preset voltage.

[0093] In some embodiments of this application, the control device 20 may further include:

[0094] The third control module is used to restore the derating factor to its default value if the power grid returns from a high-voltage state to a normal state after the derating factor is reduced.

[0095] In some embodiments of this application, the second control module 203 is further configured to control the reduction coefficient to decrease when the ratio exceeds a preset ratio, until the ratio does not exceed the preset ratio.

[0096] In some embodiments of this application, the control device 20 may further include:

[0097] The fourth control module is used to restore the derating factor to its default value if the power grid returns from a low-voltage state to a normal state after the derating factor has been reduced.

[0098] In some embodiments of this application, the judgment module 201 is further configured to obtain the grid voltage when receiving an active power request from the grid, and determine whether the grid is in a high-voltage state or a low-voltage state based on the grid voltage.

[0099] Figure 4 This is a schematic diagram of the controller provided in an embodiment of this application. Figure 4 As shown, the controller 30 in this embodiment includes a processor 300 and a memory 301, wherein the memory 301 stores a computer program 302 that can run on the processor 300. When the processor 300 executes the computer program 302, it implements the steps in the various control method embodiments described above. Alternatively, when the processor 300 executes the computer program 302, it implements the functions of each module / unit in the various device embodiments described above.

[0100] For example, computer program 302 may be divided into one or more modules / units, one or more of which are stored in memory 301 and executed by processor 300 to complete this application. One or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 302 in controller 30.

[0101] Controller 30 can be the controller of a photovoltaic system or the controller of an inverter. Controller 30 may include, but is not limited to, a processor 300 and a memory 301. Those skilled in the art will understand that... Figure 4This is merely an example of controller 30 and does not constitute a limitation on controller 30. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0102] The processor 300 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0103] The memory 301 can be an internal storage unit of the controller 30, such as a hard disk or RAM of the controller 30. The memory 301 can also be an external storage device of the controller 30, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 30. Furthermore, the memory 301 can include both internal and external storage units of the controller 30. The memory 301 is used to store computer programs and other programs and data required by the controller. The memory 301 can also be used to temporarily store data that has been output or will be output.

[0104] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0105] This application also provides a photovoltaic system, including the controller 30 described above.

[0106] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0107] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0108] In the embodiments provided in this application, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0109] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0110] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0111] If an integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various control method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0112] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A control method, characterized in that, Photovoltaic systems connected to the power grid include: To determine whether the power grid is in a high-voltage or low-voltage state, a high-voltage state is when the grid voltage is greater than the grid's rated maximum voltage, and a low-voltage state is when the grid voltage is less than the grid's rated minimum voltage. When the power grid is under high voltage, the derating factor is adjusted according to the first voltage to control the active power output of the photovoltaic system to not exceed the first limit power. The first voltage is the bus voltage of the photovoltaic system. The derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases. When the power grid is in a low-voltage state, the derating factor is adjusted according to the ratio of the first voltage and the second voltage to control the active power output of the photovoltaic system to not exceed the second limit power, where the second voltage is the grid voltage; The adjustment of the derating factor based on the first voltage includes: When the first voltage exceeds the preset voltage, the derating factor is controlled to decrease until the first voltage does not exceed the preset voltage; The adjustment of the derating factor based on the ratio of the first voltage and the second voltage includes: When the ratio exceeds a preset ratio, the derating coefficient is controlled to decrease until the ratio does not exceed the preset ratio.

2. The control method according to claim 1, characterized in that, After controlling the reduction factor to decrease, the control method further includes: If the power grid returns from a high-voltage state to a normal state, the derating factor is restored to its default value.

3. The control method according to claim 1, characterized in that, After controlling the reduction factor to decrease, the control method further includes: If the power grid returns from a low-voltage state to a normal state, the derating factor is restored to its default value.

4. The control method according to any one of claims 1 to 3, characterized in that, The determination of whether the power grid is in a high-voltage or low-voltage state includes: Upon receiving an active power request from the power grid, the grid voltage is obtained, and the grid voltage is used to determine whether the grid is in a high-voltage or low-voltage state.

5. A control device, characterized in that, The control device, applied to a photovoltaic system connected to the power grid, includes: The judgment module is used to determine whether the power grid is in a high-voltage state or a low-voltage state. The high-voltage state is the working state in which the power grid voltage is greater than the rated maximum voltage of the power grid, and the low-voltage state is the working state in which the power grid voltage is less than the rated minimum voltage of the power grid. The first control module is used to adjust the derating factor according to the first voltage when the power grid is in a high voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power. The first voltage is the bus voltage of the photovoltaic system, and the derating factor is used to adjust the voltage feedback value of the bus voltage loop. The voltage feedback value decreases as the derating factor decreases. The second control module is used to adjust the derating factor according to the ratio of the first voltage and the second voltage when the power grid is in a low voltage state, so as to control the active power output of the photovoltaic system to not exceed the limit power, wherein the second voltage is the grid voltage; The first control module includes: When the first voltage exceeds the preset voltage, the derating factor is controlled to decrease until the first voltage does not exceed the preset voltage; The second control module includes: When the ratio exceeds a preset ratio, the derating coefficient is controlled to decrease until the ratio does not exceed the preset ratio.

6. A controller comprising a memory and a processor, wherein the memory stores a computer program executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the control method as described in any one of claims 1 to 4 above.

7. A photovoltaic system, characterized in that, Includes the controller as described in claim 6.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the control method as described in any one of claims 1 to 4 above.

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