Control method, controller and photovoltaic system

Abstract

The application provides a control method, a controller and a photovoltaic system. The method is applied to a photovoltaic system connected with a power grid, and comprises the following steps: when receiving a positive reactive power request of the power grid, if a voltage of the power grid is greater than a first voltage, a derating coefficient is adjusted according to the voltage of the power grid until the voltage of the power grid is less than or equal to the first voltage, the derating coefficient is used for adjusting an output power of the photovoltaic system, the output power decreases with the decrease of the derating coefficient, and the first voltage is a rated maximum voltage of the power grid; when receiving a negative reactive power request of the power grid, if the voltage of the power grid is less than a second voltage, the derating coefficient is adjusted according to the voltage of the power grid until the voltage of the power grid is greater than or equal to the second voltage, the first voltage is greater than the second voltage, and the second voltage is a rated minimum voltage of the power grid. The application can improve the working stability of the power grid.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic control, and in particular to a control method, a controller and a photovoltaic system. BACKGROUND

[0002] When the photovoltaic system is connected to the power grid, in some cases, for example, when the line has too many nonlinear loads or the line impedance is too high, the power grid may be in a weak grid state, and the power grid has poor disturbance resistance. In the weak grid state, when the grid voltage is abnormal, if the power grid requests the photovoltaic system to output reactive power for support, the grid voltage may continuously rise or continuously drop, affecting the working reliability of the power grid.

[0003] The present application provides a control method to ensure the working reliability of the power grid in the weak grid state. SUMMARY

[0004] The embodiments of the present application provide a control method, a controller and a photovoltaic system to ensure the working reliability of the power grid in the weak grid state.

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

[0006] When receiving a positive reactive power request from the power grid, if the grid voltage is greater than a first voltage, the de-rating coefficient is adjusted according to the grid voltage until the grid voltage is less than or equal to the first voltage, the de-rating coefficient is used to adjust the output power of the photovoltaic system, the output power decreases with the decrease of the de-rating coefficient, and the first voltage is the rated maximum voltage of the power grid.

[0007] When receiving a negative reactive power request from the power grid, if the grid voltage is less than a second voltage, the de-rating coefficient is adjusted according to the grid voltage until the grid voltage is greater than or equal to the second voltage, the first voltage is greater than the second voltage, and the second voltage is the rated minimum voltage of the power grid.

[0008] In a possible implementation, the de-rating coefficient is adjusted according to the grid voltage until the grid voltage is less than or equal to the first voltage, comprising:

[0009] A decrease value of the de-rating coefficient corresponding to the current grid voltage is determined, and the de-rating coefficient is adjusted according to the decrease value to reduce the positive reactive power output of the photovoltaic system until the grid voltage is less than or equal to the first voltage.

[0010] In a possible implementation, after the grid voltage is less than or equal to the first voltage, the control method further comprises:

[0011] The de-rating coefficient is controlled to gradually recover to the default value with a first preset increase value.

[0012] In one possible implementation, the derating factor is reduced based on the grid voltage until the grid voltage is greater than or equal to the second voltage, including:

[0013] Determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the negative reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage.

[0014] In one possible implementation, after the grid voltage is greater than or equal to the second voltage, the control method further includes:

[0015] The reduction factor is gradually restored to the default value by the second preset increase value.

[0016] In one possible implementation, the control method also includes:

[0017] When a reactive power request is received from the power grid, the grid voltage is obtained. The reactive power request can be either a positive or negative reactive power request.

[0018] Secondly, embodiments of this application provide a control device applied to a photovoltaic system connected to the power grid. The control device includes:

[0019] The first control module is used to adjust the derating factor according to the grid voltage when it receives a positive reactive power request from the grid. If the grid voltage is greater than the first voltage, the derating factor is adjusted until the grid voltage is less than or equal to the first voltage. The derating factor is used to adjust the output power of the photovoltaic system. The output power decreases as the derating factor decreases. The first voltage is the rated maximum voltage of the grid.

[0020] The second control module is used to adjust the derating factor according to the grid voltage when it receives a negative reactive power request from the grid. If the grid voltage is less than the second voltage, the first voltage is greater than the second voltage, and the second voltage is the grid's rated minimum voltage.

[0021] 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.

[0022] Fourthly, embodiments of this application provide a photovoltaic system including the controller described in the third aspect above.

[0023] 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.

[0024] The application provides a control method, a controller and a photovoltaic system. When the voltage of the power grid is high, the positive reactive power provided by the photovoltaic system is controlled to be reduced, so as to avoid further increasing the voltage of the power grid. When the voltage of the power grid is low, the negative reactive power provided by the photovoltaic system is controlled to be reduced, so as to avoid further reducing the voltage of the power grid. In this way, the voltage of the power grid can be ensured to be in a normal working range as much as possible, and the reliability of the power grid is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 is a structural schematic diagram of a photovoltaic system provided by an embodiment of the present application;

[0027] Figure 2 is an implementation flowchart of a control method provided by an embodiment of the present application;

[0028] Figure 3 is a structural schematic diagram of a control device provided by an embodiment of the present application;

[0029] Figure 4 is a schematic diagram of a controller provided by an embodiment of the present application. DETAILED DESCRIPTION

[0030] In the following description, specific details such as specific system structures, techniques, etc. are presented in order to thoroughly understand the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits and methods are omitted to avoid unnecessary details that hinder the description of the present application.

[0031] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will be described by specific embodiments in conjunction with the drawings.

[0032] Figure 1 is a structural schematic diagram of a photovoltaic system provided by an embodiment of the present application, as Figure 1 shown, the photovoltaic system can 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 with the power grid.

[0033] In the embodiments of the present application, the DC bus between the DC / DC module and the DC / AC module is a bus of the photovoltaic system, and the connection point between the DC / AC module and the power grid is a grid-connected point of the photovoltaic system and the power grid.

[0034] The photovoltaic system accesses the power grid, and in the case of a weak power grid, the power grid has poor anti-disturbance performance. When the power grid is in an abnormal state, the voltage at the grid-connected point of the photovoltaic system and the power grid fluctuates, which may affect the fluctuation of the active power output by the photovoltaic system, and may further exacerbate the fluctuation of the power grid, thereby affecting the working reliability of the power grid and the working reliability of the photovoltaic system.

[0035] Specifically, when the power grid is in a high-voltage state and the power grid requests positive reactive power from the photovoltaic system, if the photovoltaic system continuously outputs positive reactive power, the voltage of the power grid may be raised, the voltage of the power grid may be raised in the case of a weak power grid, and the voltage of the bus of the photovoltaic system may be raised in turn, thereby affecting the stability of the photovoltaic system itself.

[0036] When the power grid is in a low-voltage state and the power grid requests negative reactive power from the photovoltaic system, if the photovoltaic system continuously outputs negative reactive power, the voltage of the power grid may be lowered, the voltage of the power grid may be lowered in the case of a weak power grid, and the voltage of the bus of the photovoltaic system may be lowered in turn, thereby affecting the stability of the photovoltaic system itself.

[0037] The embodiments of the present application provide a control method of a photovoltaic system to solve the problem of mutual influence between the power grid and the photovoltaic system in the case of a weak power grid, and ensure the stability of the photovoltaic system and the power grid.

[0038] Referring to Figure 2 , a flowchart for implementing the control method provided by the embodiments of the present application is shown. As shown in Figure 2 , a control method applied to a photovoltaic system connected to a power grid can include S101 and S102.

[0039] S101, when receiving a positive reactive power request of the power grid, if the voltage of the power grid is greater than a first voltage, the voltage of the power grid is adjusted to reduce the derating coefficient until the voltage of the power grid is less than or equal to the first voltage, the derating coefficient is used to adjust the output power of the photovoltaic system, the output power decreases with the decrease of the derating coefficient, and the first voltage is the rated maximum voltage of the power grid.

[0040] The execution subject of the embodiments of the present application can be a total controller of the photovoltaic system or a controller of an inverter in the photovoltaic system.

[0041] The embodiments of the present application can detect whether a positive reactive power request of the power grid is received.

[0042] When receiving the positive reactive power request of the power grid, the voltage of the power grid can be obtained, and it is determined whether the voltage of the power grid is greater than a first voltage, wherein the first voltage is the rated maximum voltage of the power grid.

[0043] When the grid voltage is greater than the first voltage, it indicates that the current grid is in a high voltage state. The derating coefficient can be adjusted according to the grid voltage to reduce the positive reactive power output by the photovoltaic system, until the grid voltage is less than or equal to the first voltage, so as to ensure that the grid is in a normal voltage range and avoid continuous voltage rise.

[0044] In the embodiments of the present application, the derating coefficient is used to adjust the output power of the photovoltaic system, and the output power of the photovoltaic system decreases with the decrease of the derating coefficient.

[0045] In the embodiments of the present application, the output power of the photovoltaic system can include positive reactive power and negative reactive power, and the output positive reactive power of the photovoltaic system decreases with the decrease of the derating coefficient. The output negative reactive power of the photovoltaic system decreases with the decrease of the derating coefficient.

[0046] In the embodiments of the present application, the value of the derating coefficient to be reduced can be determined according to the current grid voltage in the high voltage state, and the specific value can be pre-calibrated.

[0047] In the embodiments of the present application, when receiving the negative reactive power request of the grid, if the grid voltage is less than or equal to the first voltage, the derating coefficient is kept unchanged, and the output positive reactive power of the photovoltaic system is not adjusted.

[0048] S102, when receiving the negative reactive power request of the grid, if the grid voltage is less than the second voltage, the derating coefficient is adjusted according to the grid voltage, until the grid voltage is greater than or equal to the second voltage, the first voltage is greater than the second voltage, and the second voltage is the rated minimum voltage of the grid.

[0049] The embodiments of the present application can detect whether the negative reactive power request of the grid is received.

[0050] When receiving the negative reactive power request of the grid, the grid voltage can be obtained, and it is judged whether the grid voltage is less than the second voltage, wherein the second voltage is the rated minimum voltage of the grid.

[0051] When the grid voltage is less than the second voltage, it indicates that the current grid is in a low voltage state. The derating coefficient can be adjusted according to the grid voltage to reduce the negative reactive power output by the photovoltaic system, until the grid voltage is greater than or equal to the second voltage, so as to ensure that the grid is in a normal voltage range and avoid continuous voltage drop.

[0052] In the embodiments of the present application, the value of the derating coefficient to be reduced can be determined according to the current grid voltage in the low voltage state, and the specific value can be pre-calibrated.

[0053] In the embodiments of the present application, when receiving the negative reactive power request of the grid, if the grid voltage is greater than or equal to the second voltage, the derating coefficient is kept unchanged, and the output negative reactive power of the photovoltaic system is not adjusted.

[0054] The embodiment of the present application can avoid further lifting of the grid voltage by controlling to reduce the positive reactive power provided by the photovoltaic system when the grid voltage is high. The embodiment of the present application can avoid further lowering of the grid voltage by controlling to reduce the negative reactive power provided by the photovoltaic system when the grid voltage is low. In this way, the grid voltage can be ensured to be in the normal working range as much as possible, and the reliability of the grid operation can be ensured.

[0055] In some embodiments of the present application, the "adjusting the derating coefficient according to the grid voltage until the grid voltage is less than or equal to the first voltage" in S101 can include:

[0056] determining a reduction value of the derating coefficient corresponding to the current grid voltage, and adjusting the derating coefficient according to the reduction value to reduce the positive reactive power output by the photovoltaic system until the grid voltage is less than or equal to the first voltage.

[0057] In the embodiments of the present application, the grid voltage in the high-voltage state of the grid can correspond to a reduction value of the derating coefficient. Each time a grid voltage is reached, the adjustment coefficient is controlled to be reduced according to the reduction value to reduce the positive reactive power output by the photovoltaic system until the grid voltage is less than or equal to the first voltage, and the grid voltage is restored to the normal voltage range.

[0058] For example, the default value of the derating coefficient is 1, the first voltage is 824V, and the positive reactive power output by the photovoltaic system is P.

[0059] When the current grid voltage is 840V, it indicates that the current grid is in a high-voltage state, and the reduction value of the derating coefficient is 0.1. At this time, the derating coefficient can be changed from the default value 1 to 0.9, and the positive reactive power output by the photovoltaic system is adjusted to 0.9P to reduce the grid voltage.

[0060] When the current grid voltage is reduced from 840V to 835V, the reduction value of the derating coefficient is 0.1, the derating coefficient can be adjusted from 0.9 to 0.8, and the positive reactive power output by the photovoltaic system is adjusted to 0.8P to reduce the grid voltage.

[0061] When the current grid voltage is reduced from 835V to 830V, the reduction value of the derating coefficient is 0.1, the derating coefficient can be adjusted from 0.8 to 0.7, and the positive reactive power output by the photovoltaic system is adjusted to 0.7P to reduce the grid voltage.

[0062] When the current grid voltage is reduced from 930V to 825V, the reduction value of the derating coefficient is 0.1, and the derating coefficient can be adjusted from 0.7 to 0.6.

[0063] The embodiment of the present application can gradually adjust the derating coefficient to gradually reduce the positive reactive power output by the photovoltaic system when the grid is in a high-voltage state, thereby ensuring that the grid voltage slowly decreases, avoiding large fluctuations in the grid voltage, and ensuring the stability of the grid operation.

[0064] In some embodiments of the present application, after the grid voltage is less than or equal to the first voltage, the control method further comprises:

[0065] The derating coefficient is gradually restored to the default value at a first preset increase value.

[0066] After the grid is in a high voltage state, the grid voltage is gradually controlled to be below the first voltage by adjusting the derating coefficient according to the grid voltage.

[0067] After detecting that the current grid voltage is less than or equal to the first voltage, the derating coefficient can be controlled to gradually restore to the default value at a first preset increase value, so that the output of the photovoltaic system positive reactive power meets the request of the grid.

[0068] In embodiments of the present application, the first preset increase value can be determined according to actual conditions. For example, the default value of the derating coefficient is 1, the reduced derating coefficient is 0.6, and the first preset increase value is 0.1. The derating coefficient can be controlled to increase by 0.1 every interval of the first preset time length until it increases to the default value 1.

[0069] In embodiments of the present application, after the grid voltage is reduced to below the first voltage, the derating coefficient can be adjusted to gradually increase to ensure that the grid voltage is stable around the first voltage, avoid large fluctuations in the grid voltage, and ensure the stability of the grid operation.

[0070] In some embodiments of the present application, the "derating coefficient is adjusted according to the grid voltage until the grid voltage is greater than or equal to the second voltage" in S102 can include:

[0071] A decrease value of the derating coefficient corresponding to the current grid voltage is determined, and the derating coefficient is adjusted according to the decrease value to reduce the negative reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage.

[0072] In embodiments of the present application, the grid voltage in a low voltage state of the grid can correspond to a decrease value of the derating coefficient. Every time a grid voltage is reached, the adjustment coefficient is controlled to decrease according to the decrease value to reduce the positive reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage and returns to the normal voltage range.

[0073] For example, the default value of the derating coefficient is 1, the second voltage is 776V, and the output of the photovoltaic system negative reactive power is P.

[0074] When the current grid voltage is 760V, it indicates that the current grid is in a low voltage state, and the decrease value of the derating coefficient is 0.1. At this time, the derating coefficient can be changed from the default value 1 to 0.9, and the adjustment of the photovoltaic system output negative reactive power is changed to 0.9P to reduce the grid voltage.

[0075] When the current grid voltage is increased from 760V to 765V, the decrease value of the derating coefficient is 0.1, the derating coefficient can be adjusted from 0.9 to 0.8, and the photovoltaic system is adjusted to output positive reactive power of 0.8P to reduce the grid voltage.

[0076] When the current grid voltage is increased from 765V to 770V, the decrease value of the derating coefficient is 0.1, the derating coefficient can be adjusted from 0.8 to 0.7, and the photovoltaic system is adjusted to output positive reactive power of 0.7P to reduce the grid voltage.

[0077] When the current grid voltage is increased from 770V to 775V, the decrease value of the derating coefficient is 0.1, and the derating coefficient can be adjusted from 0.7 to 0.6.

[0078] The embodiment of the application gradually adjusts the derating coefficient to gradually reduce the output negative reactive power of the photovoltaic system when the grid voltage is low, thereby gradually increasing the grid voltage and avoiding large fluctuations in the grid voltage, thereby ensuring the stability of the grid.

[0079] In some embodiments of the application, after the grid voltage is greater than or equal to the second voltage, the control method further comprises:

[0080] The derating coefficient is gradually restored to the default value with a second preset increase value.

[0081] After the grid is in a low voltage state, the derating coefficient is adjusted according to the grid voltage to gradually control the grid voltage to be above the second voltage.

[0082] After detecting that the current grid voltage is greater than or equal to the second voltage, the derating coefficient can be gradually restored to the default value with a second preset increase value, so that the output negative reactive power of the photovoltaic system meets the request of the grid.

[0083] In the embodiment of the application, the second preset increase value can be determined according to actual conditions. For example, the default value of the derating coefficient is 1, the reduced derating coefficient is 0.6, and the second preset increase value is 0.1. The derating coefficient can be controlled to increase by 0.1 every second preset time interval until it increases to the default value 1.

[0084] The embodiment of the application can adjust the derating coefficient to gradually increase after the grid voltage is increased to above the second voltage, so as to ensure that the grid voltage is stable around the second voltage, avoid large fluctuations in the grid voltage, and ensure the stability of the grid.

[0085] In some embodiments of the application, the control method further comprises:

[0086] Upon receiving a reactive power request from the grid, the grid voltage is obtained, and the reactive power request includes a positive reactive power request or a negative reactive power request.

[0087] The power grid can send a positive reactive power request signal to the photovoltaic system when positive reactive power support is needed. After receiving the positive reactive power request signal, the photovoltaic system can obtain the current voltage of the power grid to determine the working state of the current power grid.

[0088] The power grid can send a negative reactive power request signal to the photovoltaic system when negative reactive power support is needed. After receiving the negative reactive power request signal, the photovoltaic system can obtain the current voltage of the power grid to determine the working state of the current power grid.

[0089] In some embodiments of the present application, after the derating coefficient is adjusted according to the voltage of the power grid, the control method can further comprise:

[0090] If the duration of adjusting the derating coefficient exceeds the preset maximum duration, an alarm signal is output, and the alarm signal is used to indicate that the adjustment of the derating coefficient is invalid.

[0091] The embodiments of the present application judge whether the adjustment is valid by monitoring the duration of adjusting the derating coefficient, and when the adjustment exceeds the duration, an alarm signal is sent to remind the staff, thereby ensuring the working reliability of the photovoltaic system to a certain extent.

[0092] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0093] The following is a device embodiment of the present application. For details not described in detail, reference can be made to the corresponding method embodiments described above.

[0094] Figure 3 The structure of the control device provided by the embodiments of the present application is shown. For ease of illustration, only the parts related to the embodiments of the present application are shown, and the details are as follows:

[0095] As Figure 3 The control device 20 applied to the photovoltaic system connected with the power grid can include:

[0096] The first control module 201 is configured to, when receiving a positive reactive power request from the power grid, if the voltage of the power grid is greater than a first voltage, adjust the derating coefficient according to the voltage of the power grid until the voltage of the power grid is less than or equal to the first voltage, the derating coefficient is used to adjust the output power of the photovoltaic system, the output power decreases with the decrease of the derating coefficient, and the first voltage is the rated maximum voltage of the power grid.

[0097] The second control module 202 is used to, when receiving a negative reactive power request from the power grid, adjust the derating factor according to the power grid voltage if the power grid voltage is less than the second voltage, until the power grid voltage is greater than or equal to the second voltage, the first voltage is greater than the second voltage, and the second voltage is the rated minimum voltage of the power grid.

[0098] In some embodiments of this application, the first control module 201 is further configured to determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the positive reactive power output of the photovoltaic system until the grid voltage is less than or equal to the first voltage.

[0099] In some embodiments of this application, the first control module 201 is further configured to control the derating factor to gradually recover to the default value by a first preset increment after the grid voltage is less than or equal to the first voltage.

[0100] In some embodiments of this application, the second control module 202 is further configured to determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the negative reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage.

[0101] In some embodiments of this application, the second control module 202 is further configured to control the derating factor to gradually recover to the default value by a second preset increment after the grid voltage is greater than or equal to the second voltage.

[0102] In some embodiments of this application, the control device 20 may further include:

[0103] The third control module is used to obtain the grid voltage when a reactive power request is received from the grid. The reactive power request can be either a positive reactive power request or a negative reactive power request.

[0104] 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.

[0105] For example, the computer program 302 can be divided into one or more modules / units, one or more modules / units are stored in the memory 301 and executed by the processor 300 to complete the present application. One or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the computer program 302 in the controller 30.

[0106] The controller 30 can be a controller of a photovoltaic system or a controller of an inverter. The controller 30 can include, but is not limited to, the processor 300, the memory 301. Those skilled in the art can understand that the controller 30 can further include other components, for example, the controller can further include an input / output device, a network access device, a bus, etc. Figure 4 The controller 30 is only an example and does not constitute a limitation on the controller 30, and can include more or fewer components than the illustration, or combine certain components, or different components, for example, the controller can also include an input / output device, a network access device, a bus, etc.

[0107] The processor 300 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0108] The memory 301 can be an internal storage unit of the controller 30, for example, a hard disk or a memory of the controller 30. The memory 301 can also be an external storage device of the controller 30, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the memory 301 can include both the internal storage unit and the external storage device 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.

[0109] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the application. The specific working process of the unit and module in the above system can refer to the corresponding process in the foregoing method embodiment, which will not be repeated here.

[0110] The embodiment of the application also provides a photovoltaic system comprising the controller 30 as above.

[0111] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0112] Those of ordinary skill in the art can appreciate that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. A person 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 the application.

[0113] In the embodiments provided in the present 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 only schematic, for example, the division of modules or units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed each other can be indirect coupling or communication connection through some interface, device or unit, which can be electrical, mechanical or other forms.

[0114] The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, i.e. may be located in one place, or may be distributed on multiple network units. Part or all of the units may be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0115] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present alone, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0116] If the integrated module / unit is realized in the form of 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 above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the processor executes the computer program, the steps of each control method embodiment can be realized. The computer program includes computer program code, which can be in the form of source code, object code, executable file or some intermediate form, etc. The computer readable medium can include any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0117] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A control method, characterized in that, Photovoltaic systems connected to the power grid include: When a positive reactive power request is received from the grid, if the grid voltage is greater than the first voltage, the derating factor is reduced according to the grid voltage until the grid voltage is less than or equal to the first voltage. The derating factor is used to adjust the output power of the photovoltaic system. The output power decreases as the derating factor decreases. The first voltage is the rated maximum voltage of the grid. When a negative reactive power request is received from the power grid, if the grid voltage is less than the second voltage, the derating factor is reduced according to the grid voltage until the grid voltage is greater than or equal to the second voltage. The first voltage is greater than the second voltage, and the second voltage is the grid's rated minimum voltage. The step of reducing the derating factor according to the grid voltage until the grid voltage is less than or equal to the first voltage includes: Determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the positive reactive power output of the photovoltaic system until the grid voltage is less than or equal to the first voltage; The step of reducing the derating factor according to the grid voltage until the grid voltage is greater than or equal to the second voltage includes: Determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the negative reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage.

2. The control method according to claim 1, characterized in that, After the grid voltage is less than or equal to the first voltage, the control method further includes: The reduction coefficient is controlled to gradually recover to the default value by a first preset increase value.

3. The control method according to claim 1, characterized in that, After the grid voltage is greater than or equal to the second voltage, the control method further includes: The reduction coefficient is controlled to gradually recover to the default value by a second preset increase value.

4. The control method according to any one of claims 1 to 3, characterized in that, The control method further includes: Upon receiving a reactive power request from the power grid, the grid voltage is obtained, and the reactive power request includes either a positive reactive power request or a negative reactive power request.

5. A control device, characterized in that, The control device, applied to a photovoltaic system connected to the power grid, includes: The first control module is used to, when receiving a positive reactive power request from the grid, if the grid voltage is greater than a first voltage, reduce the derating factor according to the grid voltage until the grid voltage is less than or equal to the first voltage. The derating factor is used to adjust the output power of the photovoltaic system. The output power decreases as the derating factor decreases. The first voltage is the rated maximum voltage of the grid. The second control module is used to, when receiving a negative reactive power request from the power grid, adjust the derating factor according to the power grid voltage if the power grid voltage is less than the second voltage, until the power grid voltage is greater than or equal to the second voltage, wherein the first voltage is greater than the second voltage and the second voltage is the rated minimum voltage of the power grid. The first control module is further configured to determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the positive reactive power output of the photovoltaic system until the grid voltage is less than or equal to the first voltage. The second control module is also used to determine the reduction value of the derating factor corresponding to the current grid voltage, and adjust the derating factor according to the reduction value to reduce the negative reactive power output of the photovoltaic system until the grid voltage is greater than or equal to the second voltage.

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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