Photovoltaic group string series connection number adjusting device and photovoltaic power generation system

Abstract

The utility model provides a photovoltaic group string serial connection number adjusting device and a photovoltaic power generation system, and belongs to the technical field of photovoltaic power generation, the device comprises a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a switch unit, the temperature monitoring unit is used for monitoring the environment temperature under the working condition of a photovoltaic group string to obtain an environment temperature signal, and the direct current voltage acquisition unit is used for acquiring the direct current voltage signal; the direct-current voltage acquisition unit is used for acquiring output voltage signals of the photovoltaic strings, and when the switch unit is in a conducting state, the photovoltaic modules connected with the switch unit in parallel are short-circuited, so that the number of the photovoltaic strings connected in series is reduced; wherein the photovoltaic modules connected in parallel with the switch units are photovoltaic modules capable of adjusting the number of group strings; according to the scheme, the number of the photovoltaic strings connected in series can be automatically, flexibly and accurately adjusted by using the switch unit at different environment temperatures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic power generation, in particular to a photovoltaic string series number adjusting device and a photovoltaic power generation system. BACKGROUND

[0002] The photovoltaic string series number is determined by the lowest temperature under the working condition of the photovoltaic string, the lower the daytime minimum temperature of the photovoltaic plant, the fewer the photovoltaic string series number, the lower the output voltage of the photovoltaic string, and the lower the power generation of the photovoltaic power generation system. The photovoltaic string is in standby state when the minimum temperature occurs throughout the day, so the lowest temperature under the working condition of the photovoltaic string is higher than the minimum temperature throughout the day.

[0003] The extreme low temperature weather accounts for a very small proportion of the year, and the day and night temperature difference is large in the area with rich sunlight resources. At the same time, due to seasonal changes, the sunrise and sunset time will also change constantly, so that the time when the minimum temperature occurs in a day also changes constantly with the seasons. Therefore, adjusting the photovoltaic string series number according to the minimum temperature will lead to a decrease in the power generation of the photovoltaic power generation system.

[0004] Therefore, how to flexibly and accurately adjust the series number of the photovoltaic string becomes a problem to be solved. CONTENT OF THE INVENTION

[0005] The purpose of the present application is to provide a photovoltaic string series number adjusting device, which can solve the problem of how to flexibly and accurately adjust the series number of the photovoltaic string in the prior art.

[0006] In the first aspect, the present application provides a photovoltaic string series number adjusting device, which comprises a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a switching unit.

[0007] The output end of the temperature monitoring unit is connected with the first input end of the control unit, and the temperature monitoring unit is used for monitoring the environmental temperature under the working condition of the photovoltaic string to obtain an environmental temperature signal; the input end of the direct current voltage acquisition unit is connected with the direct current output end of the photovoltaic string, the output end of the direct current voltage acquisition unit is connected with the second input end of the control unit, and the direct current voltage acquisition unit is used for acquiring an output voltage signal of the photovoltaic string.

[0008] In the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at least one place, each switching unit is connected in parallel with at least one photovoltaic component, the control end of the switching unit is connected with the output end of the control unit, and when the switching unit is in the conducting state, the photovoltaic component connected in parallel with the switching unit is short-circuited to reduce the series number of the photovoltaic string; wherein the photovoltaic component connected in parallel with the switching unit is a string number adjusting photovoltaic component.

[0009] In a first possible implementation manner of the first aspect, the group string number adjusting photovoltaic module includes adjacent first, second, third and fourth to-be-adjusted photovoltaic modules; the group string number adjusting photovoltaic module is a second part of a photovoltaic group string, and the remaining photovoltaic modules are a first part of the photovoltaic group string; when the switch unit is in an off state, the to-be-adjusted photovoltaic modules are connected to the first part of the photovoltaic group string.

[0010] In a second possible implementation manner of the first aspect, the control unit includes a main control module and a PWM control module; a first input terminal of the main control module is connected to an output terminal of the temperature monitoring unit, a second input terminal of the main control module is connected to an output terminal of the direct-current voltage acquisition unit, an output terminal of the main control module is connected to an input terminal of the PWM control module, and an output terminal of the PWM control module is connected to a control terminal of the switch unit.

[0011] In a third possible implementation manner of the first aspect, the control unit further includes a limiting module and a signal superposition module; an input terminal of the limiting module is connected to an output terminal of the temperature monitoring unit, an output terminal of the limiting module is connected to a first input terminal of the signal superposition module, a second input terminal of the signal superposition module is connected to an output terminal of the main control module, and an output terminal of the signal superposition module is connected to an input terminal of the PWM control module.

[0012] In a fourth possible implementation manner of the first aspect, the device includes first and second switch units; a control terminal of the first switch unit is connected to a first output terminal of the control unit, a first controlled terminal of the first switch unit is connected to a negative electrode of the first to-be-adjusted photovoltaic module, a second controlled terminal of the first switch unit is connected to a positive electrode of the second to-be-adjusted photovoltaic module, the first switch unit is used to short circuit the first and second to-be-adjusted photovoltaic modules when in a conduction state, or connect the first to-be-adjusted photovoltaic module to the second to-be-adjusted photovoltaic module and connect the third to-be-adjusted photovoltaic module to the fourth to-be-adjusted photovoltaic module when in an off state;

[0013] a control terminal of the second switch unit is connected to a second output terminal of the control unit, a first controlled terminal of the second switch unit is connected to a negative electrode of the third to-be-adjusted photovoltaic module, a second controlled terminal of the second switch unit is connected to a positive electrode of the fourth to-be-adjusted photovoltaic module, the second switch unit is used to short circuit the third and fourth to-be-adjusted photovoltaic modules when in a conduction state, or connect the third and fourth to-be-adjusted photovoltaic modules to the first part of the photovoltaic group string when in an off state; when the third and fourth to-be-adjusted photovoltaic modules are short-circuited, the first and second to-be-adjusted photovoltaic modules are simultaneously disconnected from the first part of the photovoltaic group string.

[0014] In a fifth possible implementation manner of the first aspect, the first switch unit comprises a first switch device and a first diode, and the second switch unit comprises a second switch device and a second diode; a control end of the first switch device is connected with a first output end of the control unit, a first controlled end of the first switch device is connected with a negative electrode of the first photovoltaic module to be adjusted, a second controlled end of the first switch device is connected with an anode of the first diode, a cathode of the first diode is connected with a positive electrode of the second photovoltaic module to be adjusted, and the first diode is configured to prevent current from flowing from the positive electrode of the second photovoltaic module to be adjusted into the negative electrode of the first photovoltaic module to be adjusted;

[0015] a control end of the second switch device is connected with a second output end of the control unit, a first controlled end of the second switch device is connected with a negative electrode of the third photovoltaic module to be adjusted, a second controlled end of the second switch device is connected with an anode of the second diode, a cathode of the second diode is connected with a positive electrode of the fourth photovoltaic module to be adjusted, and the second diode is configured to prevent current from flowing from the positive electrode of the fourth photovoltaic module to be adjusted into the negative electrode of the third photovoltaic module to be adjusted.

[0016] In a sixth possible implementation manner of the first aspect, the device further comprises a signal input unit; an input end of the signal input unit is connected with an output end of the control system, an output end of the signal input unit is connected with a third input end of the control unit, and the signal input unit is configured to input a preset voltage signal output by the control system and output the preset voltage signal to the control unit.

[0017] In a seventh possible implementation manner of the first aspect, the device comprises a control unit, a temperature monitoring unit, a direct-current voltage acquisition unit, and a plurality of switch units; the direct-current voltage acquisition unit comprises a plurality of input ends and a plurality of output ends, the control unit comprises a plurality of second input ends and a plurality of output ends, and there are a plurality of photovoltaic module strings connected with the input ends of the direct-current voltage acquisition unit.

[0018] An output end of the temperature monitoring unit is connected with a first input end of the control unit, the temperature monitoring unit is configured to monitor environmental temperatures under working conditions of the photovoltaic module strings to obtain a plurality of environmental temperature signals; each input end of the direct-current voltage acquisition unit is connected with a direct-current output end of a corresponding photovoltaic module string, and each output end of the direct-current voltage acquisition unit is connected with a corresponding second input end of the control unit, and the direct-current voltage acquisition unit is configured to acquire output voltage signals of the photovoltaic module strings;

[0019] In each photovoltaic module string composed of N photovoltaic modules in positive and negative series, at least one switching unit is arranged, each switching unit is connected in parallel to at least one photovoltaic module, the control end of each switching unit is connected to the corresponding output end of the control unit, and when each switching unit is in a conductive state, the photovoltaic module connected in parallel to the switching unit is short-circuited to reduce the number of series connection of the corresponding photovoltaic module string; wherein the photovoltaic module connected in parallel to each switching unit is the corresponding photovoltaic module to be adjusted.

[0020] In a second aspect, the embodiments of the present application provide a photovoltaic power generation system, which comprises a photovoltaic module string, an inverter, a box transformer alternating current device, a control system, and the photovoltaic module string series number adjustment device in the first to sixth possible implementation manners of the first aspect;

[0021] The direct current input end of the photovoltaic module string is connected to the output end of the photovoltaic module string series number adjustment device, the direct current output end of the photovoltaic module string is connected to the power supply input end of the inverter and the first input end of the photovoltaic module string series number adjustment device, and the photovoltaic module string is used to provide an output voltage signal to the photovoltaic module string series number adjustment device and output the direct current after adjusting the series number of the photovoltaic module string to the inverter;

[0022] The output end of the inverter is connected to the input end of the box transformer alternating current device, the inverter is used to invert the direct current output by the photovoltaic module string into alternating current and output the alternating current to the box transformer alternating current device, the output end of the box transformer alternating current device is connected to the input end of the power grid, and the box transformer alternating current device is used to collect and boost the alternating current output by the inverter and output the boosted alternating current to the power grid;

[0023] The output end of the control system is connected to the second input end of the photovoltaic module string series number adjustment device, the control system is used to output a preset voltage signal to the photovoltaic module string series number adjustment device, and the photovoltaic module string series number adjustment device is used to adjust the series number of the photovoltaic module string based on the ambient temperature signal under the working condition of the photovoltaic module string, the output voltage signal provided by the photovoltaic module string, and the preset voltage signal.

[0024] In a possible implementation manner of the second aspect, the system comprises a plurality of photovoltaic module strings, an inverter, a box transformer alternating current device, a control system, and the photovoltaic module string series number adjustment device in the seventh possible implementation manner; wherein the photovoltaic module string series number adjustment device comprises a plurality of first input ends, a second input end, and a plurality of output ends, and the inverter comprises a plurality of power supply input ends;

[0025] The direct current input end of each photovoltaic string is connected with the corresponding output end of the photovoltaic string series number adjusting device, the direct current output end of each photovoltaic string is connected with the corresponding power supply input end of the inverter and the corresponding first input end of the photovoltaic string series number adjusting device, and each photovoltaic string is used for providing the corresponding output voltage signal to the photovoltaic string series number adjusting device and outputting the corresponding direct current after adjusting the series number of the photovoltaic string to the inverter;

[0026] The output end of the inverter is connected with the input end of the box transformer alternating current device, the inverter is used for inverting the direct current output by each photovoltaic string into alternating current and outputting the alternating current to the box transformer alternating current device, the output end of the box transformer alternating current device is connected with the input end of the power grid, and the box transformer alternating current device is used for collecting and boosting the alternating current output by the inverter and outputting the boosted alternating current to the power grid;

[0027] The output end of the control system is connected with the second input end of the photovoltaic string series number adjusting device, the control system is used for outputting a preset voltage signal to the photovoltaic string series number adjusting device, and the photovoltaic string series number adjusting device is used for adjusting the series number of each photovoltaic string based on the environmental temperature signal under the working condition of each photovoltaic string, the output voltage signal provided by each photovoltaic string and the preset voltage signal.

[0028] The photovoltaic string series number adjusting device of the photovoltaic string provided in the application comprises a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a switching unit, the temperature monitoring unit obtains an environmental temperature signal by monitoring the environmental temperature under the working condition of the photovoltaic string, the direct current voltage acquisition unit acquires the output voltage signal of the photovoltaic string, and the switching unit adjusts the series number of the photovoltaic string by short-circuiting the photovoltaic assembly connected in parallel with the switching unit. The scheme provided in the application sets the switching unit at least at one place in the photovoltaic string, can automatically and flexibly and accurately adjust the series number of the photovoltaic string at different environmental temperatures by using the switching unit, is not limited by the minimum temperature under the working condition of the photovoltaic string, and has strong usability and practicality.

[0029] Other features and advantages of the application will be described in detail in the following specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0031] Figure 1 is a schematic block diagram of the overall structure of a photovoltaic string series number adjusting device of a photovoltaic string provided in an embodiment of the application;

[0032] Figure 2 is a specific structure schematic diagram of a photovoltaic string series connection number adjustment device of a photovoltaic string provided by an embodiment of the present application;

[0033] Figure 3 is a whole structure schematic diagram of a photovoltaic string series connection number adjustment device of multiple photovoltaic strings provided by an embodiment of the present application;

[0034] Figure 4 is a schematic diagram of a photovoltaic power generation system including a photovoltaic string provided by an embodiment of the present application;

[0035] Figure 5 is a schematic diagram of a photovoltaic power generation system including multiple photovoltaic strings provided by an embodiment of the present application;

[0036] Figure 6 is a step schematic diagram of a photovoltaic string series connection number adjustment method of a photovoltaic string provided by an embodiment of the present application;

[0037] Figure 7 is a step schematic diagram of a photovoltaic string series connection number adjustment method of multiple photovoltaic strings provided by an embodiment of the present application. DETAILED DESCRIPTION

[0038] In the following description, for the purposes of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc. in order to provide a thorough understanding of the embodiments of the application. However, it will be apparent to those skilled in the art that the application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the application with unnecessary detail.

[0039] It should be understood that the term "comprising" when used in this specification and the appended claims, indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0040] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0041] It should also be further understood that the term "and / or" as used herein, in the specification and in the claims, means any one of the items, any combination of the items, or all of the items with reference to a list of items that consists of at least one item.

[0042] As used in the specification and the appended claims, the term "if' can be construed to mean "when" or "upon" or "in response to determining" or "in response to ascertaining," depending on the context. Similarly, the phrase "if it is determined" or "if [a described condition or event] is detected" can be construed to mean "upon determining" or "in response to determining" or "upon [the described condition or event] being detected" or "in response to [the described condition or event] being detected," depending on the context.

[0043] In addition, the terms "first", "second", "third", etc. are used herein only to distinguish one element from another, and do not imply a relative importance.

[0044] The use of the terms "one embodiment", "some embodiments", "an embodiment", "one implementation", "some implementations", "an implementation", etc., in the description above, is not to be construed as indicating that a particular feature is ascribed to only one implementation. For the same reason, the use of terms such as "some", "others", "additional", "another", "one or more", "at least one" or "one or more than one" are not to be construed as indicating that there is one feature selected from the group consisting of one embodiment, some embodiments or one implementation, etc., and not another feature selected from the group consisting of one embodiment, some embodiments or one implementation, etc.

[0045] In the description of the present application, the orientation words such as "upper", "lower", "left", "right" are used without specific indication, which generally refer to the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product is used.

[0046] In the description of the present application, it should be further noted that, unless otherwise explicitly specified and limited, the terms "setting", "mounting", "connecting", "connecting" should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] With the rapid development of the current economy, the global demand for energy is increasing, but the resulting fossil energy shortage and environmental pollution problems are gradually highlighted, so it is urgent to find new energy sources to replace fossil energy, which will become an important means to solve the problems of energy shortage, environmental pollution, etc. Therefore, the use of clean, safe and pollution-free renewable energy is now receiving more and more attention. New energy such as wind energy, solar energy, biomass energy and ocean energy is improving its position in the energy strategy of various countries due to its clean, safe and renewable characteristics. Among them, solar energy has relatively low cost, mature technology and high reliability, and has developed rapidly in recent years and begun to play an important role in energy supply.

[0048] The most important form of solar energy utilization is photovoltaic power generation. For ground-based large-scale photovoltaic power stations, the number of photovoltaic string series in the photovoltaic power generation system is mainly affected by the open circuit voltage Voc of the photovoltaic string, the open circuit voltage temperature coefficient Kv of the photovoltaic string, the maximum DC input voltage Vdcmax allowed by the inverter and the environmental temperature t. In general design, the open circuit voltage Voc of the photovoltaic string, the open circuit voltage temperature coefficient Kv of the photovoltaic string and the maximum DC input voltage Vdcmax allowed by the inverter can be determined according to the manufacturer's data and are fixed values, while the environmental temperature t is a variable quantity, so it becomes an important parameter affecting the number of photovoltaic string series.

[0049] The number of photovoltaic string series refers to the number of series N of photovoltaic modules in each photovoltaic string, which can be calculated according to the following formula:

[0050]

[0051] Wherein, Kv represents the open circuit voltage temperature coefficient of the photovoltaic string, Kv` represents the working voltage temperature coefficient of the photovoltaic string, N represents the number of series of photovoltaic modules (N is rounded), t` represents the minimum temperature under the working condition of the photovoltaic string, t`` represents the maximum temperature under the working condition of the photovoltaic string, Vdcmax represents the maximum DC input voltage allowed by the inverter, Vmppt max represents the maximum value of the MTTP (Maximum Power Point Tracking) voltage of the inverter, Voc represents the open circuit voltage of the photovoltaic string, and Vpm represents the working voltage of the photovoltaic string (i.e. the output voltage of the photovoltaic string or the series voltage of the photovoltaic module).

[0052] To achieve technical and economic optimization, ground photovoltaic power stations generally use the maximum number of photovoltaic string series design, at which time only formula 1 needs to be calculated. Distributed photovoltaic power systems combined with buildings usually do not use the maximum number of photovoltaic string series design, at which time formula 1 and formula 2 need to be considered comprehensively to determine the range of the number of photovoltaic string series.

[0053] From formula 1, when the open circuit voltage Voc of the photovoltaic string, the open circuit voltage temperature coefficient Kv of the photovoltaic string and the maximum DC input voltage Vdcmax allowed by the inverter are fixed, the number of photovoltaic string series N is proportional to the ambient temperature t. Assuming that the system voltage is 1500V, that is, the maximum DC input voltage Vdcmax allowed by the inverter is 1500V, and that the open circuit voltage Voc of the photovoltaic string is 50V, the open circuit voltage temperature coefficient Kv of the photovoltaic string is-0.0026 / ℃, and the ambient temperature t under the working condition of the photovoltaic string is 25℃ under the standard test condition, the number of photovoltaic string series N is calculated to be 30 pieces by formula 1. Table 1 is a table of the number of photovoltaic string series N under different ambient temperatures, and the number of photovoltaic string series N under different ambient temperatures is shown in Table 1.

[0054] Table 1

[0055]

[0056] From Table 1 and the characteristics of the photovoltaic module, it can be seen that the voltage of the photovoltaic module under sunlight will decrease with the increase of the ambient temperature, and the open circuit voltage of the photovoltaic string will decrease with the increase of the ambient temperature under the working condition of the photovoltaic string due to the influence of the open circuit voltage temperature coefficient. Therefore, the open circuit voltage of the photovoltaic string will increase when the ambient temperature decreases. In order to ensure that the inverter can work normally and continuously at the lowest temperature in the local area, the influence of the lowest temperature in the local area on the open circuit voltage of the photovoltaic string should be considered when calculating the working voltage of the photovoltaic string by using the above formula. Therefore, the ambient temperature t should be selected as the lowest temperature under the working condition of the photovoltaic string.

[0057] As can be seen, the number of photovoltaic string series is determined by the lowest temperature under the working condition of the photovoltaic string, the lower the daytime minimum temperature in the photovoltaic plant area, the smaller the number of photovoltaic string series, the lower the output voltage of the photovoltaic string, and the lower the power generation of the photovoltaic power generation system. When the lowest temperature appears throughout the day, the photovoltaic string is in standby state, so the lowest temperature under the working condition of the photovoltaic string is higher than the lowest temperature throughout the day.

[0058] The extreme low temperature weather accounts for a very small proportion in a year, and the diurnal temperature difference is large in the area with rich sunlight resources. At the same time, due to seasonal changes, the time of sunrise and sunset will also change constantly, so that the time when the lowest temperature appears in a day also changes constantly with the seasons. Therefore, adjusting the number of photovoltaic string series according to the lowest temperature will lead to the decrease of the power generation of the photovoltaic power generation system.

[0059] The output voltage of the photovoltaic string (i.e. the input voltage of the inverter) cannot exceed the maximum DC input voltage allowed by the inverter, and the output voltage of the photovoltaic string is generally limited by the inverter. At present, there are few schemes for adjusting the series number of the photovoltaic string, and in the prior art, in order to increase the series number of the photovoltaic string, a voltage switch is arranged at the input end of the inverter. When the output voltage of the photovoltaic string exceeds the maximum DC input voltage allowed by the inverter, the inverter will stop working. This usually causes the inverter to be unable to work in the rated state for a long time, and the ideal efficiency cannot be achieved. Therefore, how to flexibly and accurately adjust the series number of the photovoltaic string becomes a problem to be solved.

[0060] In view of the above defects, the photovoltaic string series number adjusting device provided in the present application comprises a control unit, a temperature monitoring unit, a DC voltage acquisition unit and a switch unit. The temperature monitoring unit obtains an ambient temperature signal by monitoring the ambient temperature under the working condition of the photovoltaic string, the DC voltage acquisition unit acquires an output voltage signal of the photovoltaic string, and the switch unit adjusts the series number of the photovoltaic string by short-circuiting the photovoltaic module connected in parallel thereto. The scheme of the present application sets the switch unit at least at one place in the photovoltaic string, and can automatically, flexibly and accurately adjust the series number of the photovoltaic string under different ambient temperatures by using the switch unit, is not limited by the minimum temperature under the working condition of the photovoltaic string, and has strong ease of use and practicality.

[0061] The overall structure of the photovoltaic string series number adjusting device provided in the embodiments of the present application will be described below through specific embodiments.

[0062] Please refer to Figure 1 , Figure 1 is the overall structure schematic block diagram of the photovoltaic string series number adjusting device 100 of the photovoltaic string 210 provided in the embodiments of the present application. As shown in Figure 1 , the photovoltaic string series number adjusting device 100 comprises a control unit 110, a temperature monitoring unit 120, a DC voltage acquisition unit 130, a first switch unit 142 and a second switch unit 144.

[0063] In one embodiment, an output terminal of the temperature monitoring unit 120 is connected to a first input terminal of the control unit 110, the temperature monitoring unit 120 is configured to obtain an ambient temperature signal T by monitoring the ambient temperature (i.e. the ambient temperature of the photovoltaic plant) under the working condition of the photovoltaic string 210 in real time, and output the ambient temperature signal T to the control unit 110. An input terminal of the direct current voltage acquisition unit 130 is connected to a direct current output terminal (including positive and negative terminals BUS+, BUS-) of the photovoltaic string 210, and an output terminal of the direct current voltage acquisition unit 130 is connected to a second input terminal of the control unit 110. The direct current voltage acquisition unit 130 is configured to acquire an output voltage signal Vdc of the photovoltaic string 210, and provide the output voltage signal Vdc to the control unit 110.

[0064] In some embodiments, the control unit 110 comprises at least one output terminal. In the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged. Each switching unit is connected in parallel to at least one photovoltaic component, and a control terminal of each switching unit is connected to a corresponding output terminal of the control unit 110. When each switching unit is in a conducting state, the photovoltaic component connected in parallel to the switching unit is short-circuited, so as to reduce the number of series connection of the photovoltaic string. The photovoltaic components connected in parallel to each switching unit are the group number adjustment photovoltaic components.

[0065] In some embodiments, the control unit 110 is configured to generate control signals UK1-UKn based on the ambient temperature signal T, the output voltage signal Vdc and a preset voltage signal Vdcmax, and output the control signals UK1-UKn to the control terminals of the switching units. The preset voltage is the maximum direct current input voltage allowed by the inverter, and each control signal UK1-UKn is used to control the corresponding switching unit to be in a conducting state or a non-conducting state.

[0066] In one embodiment, in the photovoltaic string composed of N photovoltaic components in positive and negative series, a first switching unit 142 can be arranged at the photovoltaic components A1 and A2, and the first switching unit 142 is connected in parallel to the photovoltaic components A1 and A2. A second switching unit 144 can also be arranged at the photovoltaic components B1 and B2, and the switching unit 144 is connected in parallel to the photovoltaic components B1 and B2. The control terminals of the first switching unit 142 and the second switching unit 144 are respectively connected to the output terminals of the control unit 110. When the first switching unit 142 and the second switching unit 144 are in a conducting state, the photovoltaic components A1, A2, B1 and B2 are short-circuited, so as to reduce the number of series connection of the photovoltaic string 210. When the photovoltaic components A1, A2, B1 and B2 are short-circuited, a part of the photovoltaic components in the photovoltaic string 210 is removed, so that the number of series connection of the photovoltaic string 210 is reduced. The photovoltaic components A1, A2, B1 and B2 are the group number adjustment photovoltaic components 214.

[0067] In one embodiment, the first output end and the second output end of the control unit 110 are connected to the control ends of the first switch unit 142 and the second switch unit 144 respectively. The control unit 110 is configured to generate control signals UK1 and UK2 based on the ambient temperature signal T, the output voltage signal Vdc and the preset voltage signal Vdcmax, and output the control signals UK1 and UK2 to the control ends of the first switch unit 142 and the second switch unit 144 respectively. The control signals UK1 and UK2 are configured to control the first switch unit 142 and the second switch unit 144 to be turned on or turned off respectively.

[0068] In another embodiment, in a photovoltaic string composed of N photovoltaic components connected in positive and negative series, a switch unit can be arranged at each of the photovoltaic components A1, A2, B1 and B2. The four switch units are connected in parallel to the photovoltaic components A1, A2, B1 and B2 respectively, and the control ends of the four switch units are connected to the output ends of the control unit 110. When the four switch units are in the on state, the photovoltaic components A1, A2, B1 and B2 are short-circuited respectively, so as to reduce the number of series connection of the photovoltaic string.

[0069] In another embodiment, in a photovoltaic string composed of N photovoltaic components connected in positive and negative series, a switch unit is arranged at one position. The switch unit is connected in parallel to the four photovoltaic components A1, A2, B1 and B2, and the control end of the switch unit is connected to the output end of the control unit 110.

[0070] It should be noted that, Figure 1 The arrangement of the switch unit in the above embodiment is only one of the many possible arrangements. The number of series connection of the photovoltaic components can also be multiple, which can be adjacent or not adjacent. The specific arrangement can be determined according to the actual application scenario.

[0071] In this embodiment, the temperature monitoring unit 120 obtains the ambient temperature signal T by monitoring the ambient temperature under the working condition of the photovoltaic string 210, the direct current voltage acquisition unit 130 acquires the output voltage signal Vdc of the photovoltaic string 210, and the control unit 110 generates control signals UK1-UKn based on the ambient temperature signal, the output voltage signal Vdc and the preset voltage signal Vdcmax, and controls the corresponding switch units to be turned on based on the control signals UK1-UKn. Each switch unit adjusts the number of series connection of the photovoltaic string 210 by short-circuiting the photovoltaic components connected in parallel thereto.

[0072] The scheme of the embodiment is to set a switching unit at at least one position of the photovoltaic string 210, and the switching unit can be used to automatically and flexibly adjust the series number of the photovoltaic string 210 under different ambient temperatures, and is not limited by the minimum temperature under the working condition of the photovoltaic string 210. Under the premise of meeting the maximum DC input voltage allowed by the inverter, the maximum series number can be ensured, the number of inverters and photovoltaic supports is reduced, the land occupation of the photovoltaic plant is also reduced, and the investment of the photovoltaic project is reduced. In addition, the power generation of the photovoltaic power generation system is increased, the economic performance of the photovoltaic project is improved, and the photovoltaic power generation system has strong usability and practicality.

[0073] The specific structure of the photovoltaic string series number adjusting device 100 provided by the embodiment of the application will be described below through specific embodiments.

[0074] Please refer to Figure 2 , Figure 2 is a specific structure schematic diagram of a photovoltaic string series number adjusting device 100 of a photovoltaic string 210 provided by the embodiment of the application. As Figure 2 indicated, in one embodiment, the string number adjusting photovoltaic component 214 includes adjacent first, second, third and fourth to-be-adjusted photovoltaic components A1, A2, B1 and B2. The string number adjusting photovoltaic component 214 is the second part of the photovoltaic string 210, and the remaining photovoltaic components are the first part of the photovoltaic string 210. When the first and second switching units 142 and 144 are in the off state, the string number adjusting photovoltaic component 214 is connected to the first part 212 of the photovoltaic string 210.

[0075] In another embodiment, the plurality of to-be-adjusted photovoltaic components can also be non-adjacent and can be separated in the photovoltaic string 210. For example, a switching unit is arranged at the first column of photovoltaic components in the photovoltaic string 210, a switching unit is arranged at the middle column of photovoltaic components, and a switching unit is arranged at the last column of photovoltaic components. The three columns of photovoltaic components are the string number adjusting photovoltaic components and are non-adjacent.

[0076] In the embodiment, the plurality of to-be-adjusted photovoltaic components are adjacent, and only one switching unit can be arranged, and only one switching unit can be used to adjust the series number of the photovoltaic string 210, thereby reducing the number of switching units and simplifying

[0077] the circuit structure.

[0078] Please continue to refer to Figure 2In one embodiment, the control unit 110 includes a main control module 112 and a PWM control module 114. A first input of the main control module 112 is connected to an output of the temperature monitoring unit 120. The ambient temperature signal T output by the temperature monitoring unit 120 is input to the control module 112. A second input of the main control module 112 is connected to an output of the DC voltage acquisition unit 130. The output voltage signal Vdc acquired by the DC voltage acquisition unit 130 is input to the main control module 112. The main control module 112 is configured to generate a main control signal U0 based on the ambient temperature signal T, the output voltage signal Vdc, and a preset voltage signal Vdcmax. The output of the main control module 112 is connected to an input of the PWM control module 114. The main control module 112 outputs the main control signal U0 to the PWM control module 114. The first output terminal of the PWM control module 114 is connected to the control terminal of the first switch unit 142 , and the second output terminal of the PWM control module 114 is connected to the control terminal of the second switch unit 144 . The PWM control module 114 outputs the main control signal U0 to the control terminals of the first switch unit 142 and the second switch unit 144 respectively.

[0079] Please continue to see Figure 2 In one embodiment, the control unit 110 further includes: a limit module 116 and a signal superposition module 118. The input end of the limit module 116 is connected to the output end of the temperature monitoring unit 120, the ambient temperature signal T is input to the limit module 116, and the output end of the limit module 116 is connected to the first input end of the signal superposition module 118. The limit module is used to generate a limit signal 0 or 1 based on the ambient temperature signal T, and output the limit signal 0 or 1 to the signal superposition module 118. The second input end of the signal superposition module 118 is connected to the output end of the main control module 112, the main control signal U0 is input to the signal superposition module 118, and the output end of the signal superposition module 118 is connected to the input end of the PWM control module 114. The signal superposition module 118 is used to perform logical operation and superposition on the ambient temperature signal T and the main control signal U0 to generate a modulation signal U1, and output the modulation signal U1 to the PWM control module 114.

[0080] Please continue to see Figure 2 In one embodiment, the PWM control module 114 is configured to generate a drive signal PWM (Pulse Width Modulation) based on the modulation signal U1, and output the drive signal PWM to the control terminals of the first switch unit 142 and the second switch unit 144, respectively. The drive signal PWM is configured to control the first switch unit 142 and the second switch unit 144 to be turned on or off.

[0081] Please continue to see Figure 2In one embodiment, the photovoltaic string series quantity adjustment device 100 comprises a first switch unit 142 and a second switch unit 144. The control end of the first switch unit 142 is connected with the first output end of the control unit 110, the first controlled end of the first switch unit 142 is connected with the negative electrode of the first photovoltaic component to be adjusted A1, and the second controlled end of the first switch unit 142 is connected with the positive electrode of the second photovoltaic component to be adjusted A2. The first switch unit 142 is used to short-circuit the first photovoltaic component to be adjusted A1 and the second photovoltaic component to be adjusted A2 when in the on state, or the first switch unit 142 is used to connect the first photovoltaic component to be adjusted A1 and the second photovoltaic component to be adjusted A2, and connect the third photovoltaic component to be adjusted B1 and the fourth photovoltaic component to be adjusted B2 when in the off state.

[0082] In one embodiment, the control end of the second switch unit 144 is connected with the second output end of the control unit 110, the first controlled end of the second switch unit 144 is connected with the negative electrode of the third photovoltaic component to be adjusted B1, and the second controlled end of the second switch unit 144 is connected with the positive electrode of the fourth photovoltaic component to be adjusted B2. The second switch unit 144 is used to short-circuit the third photovoltaic component to be adjusted B1 and the fourth photovoltaic component to be adjusted B2 when in the on state, or the second switch unit 144 is used to connect the third photovoltaic component to be adjusted B1 and the fourth photovoltaic component to be adjusted B2 with the first part 212 of the photovoltaic string 210 at the same time when in the off state.

[0083] Wherein, when the third photovoltaic component to be adjusted B1 and the fourth photovoltaic component to be adjusted B2 are short-circuited, the first photovoltaic component to be adjusted A1 and the second photovoltaic component to be adjusted A2 are disconnected with the first part 212 of the photovoltaic string 210 at the same time, so that the series quantity of the photovoltaic string 210 is reduced.

[0084] Please continue to see Figure 2 In one embodiment, the first switch unit 142 comprises a first switch device VD1 and a first diode D1, and the second switch unit 144 comprises a second switch device VD2 and a second diode D2. The control end of the first switch device VD1 is connected with the first output end of the control unit 110, the first controlled end of the first switch device VD1 is connected with the negative electrode of the first photovoltaic component to be adjusted A1, and the second controlled end of the first switch device VD1 is connected with the anode of the first diode D1. The cathode of the first diode D1 is connected with the positive electrode of the second photovoltaic component to be adjusted A2, and the first diode D1 is used to prevent the reverse flow of current, i.e. from the second positive electrode of the second photovoltaic component to be adjusted A2 to the negative electrode of the first photovoltaic component to be adjusted A1.

[0085] In one embodiment, the control end of the second switching device VD2 is connected with the second output end of the control unit 110, the first controlled end of the second switching device VD2 is connected with the negative pole of the third photovoltaic module to be regulated B1, and the second controlled end of the second switching device VD2 is connected with the anode of the second diode D2. The cathode of the second diode D2 is connected with the positive pole of the fourth photovoltaic module to be regulated B2, and the second diode D2 is used to prevent the current from flowing reversely, i.e. from the positive pole of the fourth photovoltaic module to be regulated B2 to the negative pole of the third photovoltaic module to be regulated B1. When the second switching device VD2 is turned on, the third photovoltaic module to be regulated B1 and the fourth photovoltaic module to be regulated B2 are short-circuited. Due to the effect of the second diode D2, the current cannot flow reversely, and the first photovoltaic module to be regulated A1, the second photovoltaic module to be regulated A2, the third photovoltaic module to be regulated B1 and the fourth photovoltaic module to be regulated B2 cannot form a loop, so as to be disconnected with the first part 212 of the photovoltaic string 210, and the number of the photovoltaic string 210 in series is reduced.

[0086] The first switching device VD1 and the second switching device VD2 can be IGBTs, which are preferred switching devices due to small volume, controllability, controllable opening and closing, high voltage resistance, high integration of driving circuit and simple control. The control end of the first switching device VD1 and the second switching device VD2 is the gate electrode G, the first controlled end is the collector electrode E, and the second controlled end is the emitter electrode C.

[0087] The emitter electrode C is the second controlled end.

[0088] Please continue to refer to Figure 2 In one embodiment, the photovoltaic string series number regulating device 100 of the plurality of photovoltaic strings 211-21n further comprises a signal input unit 150. The input end of the signal input unit 150 is connected with the output end of the control system 230, and the output end of the signal input unit 150 is connected with the third input end of the control unit 110. The signal input unit 150 is used to input the fixed parameter output by the control system 230, such as the preset voltage signal Vdcmax, and output the preset voltage signal Vdcmax to the control unit 110.

[0089] Please refer to Figure 3 , Figure 3 is the overall structural schematic block diagram of the photovoltaic string series number regulating device 100 of the plurality of photovoltaic strings 211-21n provided by the embodiments of the present application. As Figure 3 shown, the photovoltaic string series number regulating device 100 comprises a control unit 110, a temperature monitoring unit 120, a direct-current voltage acquisition unit 130 and a plurality of switching units 141-14n. The direct-current voltage acquisition unit 130 comprises a plurality of input ends and a plurality of output ends, the control unit 110 comprises a plurality of second input ends and a plurality of output ends, and the photovoltaic strings connected with the input ends of the direct-current voltage acquisition unit 130 are a plurality of photovoltaic strings 211-21n.

[0090] In one embodiment, the output of the temperature monitoring unit 120 is connected to the first input of the control unit 110, the temperature monitoring unit 120 is used to monitor the ambient temperature of each photovoltaic string 211-21n under working condition, and obtain a plurality of ambient temperature signals T1-Tn. The input of the direct current voltage acquisition unit 130 is connected to the direct current output [including positive and negative terminals (BUS1+, BUS1-)-(BUSn+, BUSn-)] of the corresponding photovoltaic string 211-21n, and the output of the direct current voltage acquisition unit 130 is connected to the corresponding second input of the control unit 110. The direct current voltage acquisition unit 130 is used to acquire the output voltage signal VdcS1-VdcSn of each photovoltaic string 211-21n.

[0091] In one embodiment, the output of the control unit 110 is connected to the control end of each switching unit 141-14n. The control unit 110 is used to generate a control signal UK1-UKn based on the ambient temperature signal T1-Tn, the output voltage signal VdcS1-VdcSn and the preset voltage signal Vdcmax, and output the corresponding control signal UK1-UKn to the control end of each switching unit 141-14n. Each control signal UK1-UKn is used to control the corresponding switching unit 141-14n to be turned on or turned off.

[0092] In some embodiments, in each photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at least one place. Each switching unit is connected in parallel to at least one photovoltaic component, and the control end of each switching unit is connected to the corresponding output of the control unit. When each switching unit is in the on state, the photovoltaic component connected in parallel to it is short-circuited, so as to reduce the number of series of the corresponding photovoltaic string. The photovoltaic component connected in parallel to each switching unit is the corresponding photovoltaic component to be adjusted.

[0093] In one embodiment, in the photovoltaic module string 211~21n composed of N photovoltaic modules in positive and negative series, there are provided switching units 141~14n. Each switching unit 141, 142~14(n-1), 14n is connected in parallel to the corresponding photovoltaic modules (A1 and A2), (B1 and B2)~(A1n and A2n), (B1n and B2n), and the control end of each switching unit 141, 142~14(n-1), 14n is connected to the corresponding output end of the control unit 110. When each switching unit 141, 142~14(n-1), 14n is in the on state, the corresponding photovoltaic modules (A1, A2, B1 and B2)~(A1n, A2n, B1n and B2n) are short-circuited to reduce the number of series connections of the corresponding photovoltaic module string 211~21n. Among them, the photovoltaic modules (A1, A2, B1 and B2)~(A1n, A2n, B1n and B2n) are the number of strings of the photovoltaic module string 21111~2111n.

[0094] It should be noted that the specific structure of the photovoltaic module string 210 series number adjustment device 100 of the plurality of photovoltaic module strings is substantially the same as that of the photovoltaic module string 210 series number adjustment device 100 of the one photovoltaic module string, which will not be described here.

[0095] Please refer to Figure 4 , Figure 4 is a schematic block diagram of the photovoltaic power generation system 200 including one photovoltaic module string 210 provided by the embodiment of the present application. As Figure 4 shown, the photovoltaic power generation system 200 includes: a photovoltaic module string 210, an inverter 220, a control system 230, a box transformer AC device 240, and a photovoltaic module string series number adjustment device 100 of one photovoltaic module string 210.

[0096] In one embodiment, the DC input end (including positive and negative terminals VIN+, VIN-) of the photovoltaic module string 210 is connected to the output end of the photovoltaic module string 210 series number adjustment device 100, and the DC output end (including positive and negative terminals BUS+, BUS-) of the photovoltaic module string 210 is connected to the power supply input end (including positive and negative terminals N+, N-) of the inverter 220 and the first input end of the photovoltaic module string 210 series number adjustment device 100. The photovoltaic module string 210 is used to provide an output voltage signal Vdc to the photovoltaic module string 210 series number adjustment device 100 and output the DC power after adjusting the series number of the photovoltaic module string 210 to the inverter 220.

[0097] In one embodiment, the output end of the inverter 220 is connected with the input end of the box transformer AC device 240, the inverter 220 is used to invert the direct current output by the photovoltaic group string 210 into alternating current, and output the alternating current to the box transformer AC device 240. Wherein, the inverter can be a DC-AC converter. The output end of the box transformer AC device 240 is connected with the input end of the power grid, the box transformer AC device 240 is used to collect and boost the alternating current output by the inverter 220, and output the boosted alternating current to the power grid. The output end of the control system 230 is connected with the second input end of the photovoltaic group string 210 series number adjusting device 100, the control system 230 is used to output a preset voltage signal Vdcmax to the photovoltaic group string 210 series number adjusting device 100. The photovoltaic group string 210 series number adjusting device 100 is used to adjust the series number of the photovoltaic group string 210 based on the ambient temperature signal T under the working condition of the photovoltaic group string 210, the output voltage signal Vdc provided by the photovoltaic group string 210 and the preset voltage signal Vdcmax.

[0098] Please refer to Figure 5 , Figure 5 is a schematic block diagram of a photovoltaic power generation system 200 provided by the embodiment of the present application, which includes a plurality of photovoltaic group strings 211-21n. As shown in Figure 5 , the photovoltaic power generation system 200 includes: a plurality of photovoltaic group strings 211-21n, an inverter 220, a control system 230, a box transformer AC device 240 and a photovoltaic group string series number adjusting device 100 of the plurality of photovoltaic group strings 211-21n. Wherein, the photovoltaic group string series number adjusting device 100 includes a plurality of first input ends, a second input end and a plurality of output ends, and the inverter 220 includes a plurality of power supply input ends [including positive and negative terminal (N1+, N1-)~(Nn+, Nn-)].

[0099] In one embodiment, the direct current input end [including positive and negative terminal (VIN1+, VIN1-)~(VINn+, VINn-)] of each photovoltaic group string 211-21n is connected with the corresponding output end of the photovoltaic group string series number adjusting device 100, and the direct current output end [including positive and negative terminal (BUS1+, BUS1-)~(BUSn+, BUSn-)] of each photovoltaic group string 211-21n is connected with the corresponding power supply input end of the inverter 220 and the corresponding first input end of the photovoltaic group string series number adjusting device 100. Each photovoltaic group string 211-21n is used to provide the corresponding output voltage signal VdcS1-VdcSn to the photovoltaic group string series number adjusting device 100 and output the corresponding direct current after adjusting the series number of the photovoltaic group string 211-21n to the inverter 220.

[0100] In one embodiment, the output end of the inverter 220 is connected with the input end of the box transformer AC device 240, the inverter 220 is used to invert the direct current output by each photovoltaic string 211-21n into alternating current, and output the alternating current to the box transformer AC device 240. The output end of the box transformer AC device 240 is connected with the input end of the power grid, and the box transformer AC device 240 is used to collect and boost the alternating current output by the inverter 220, and output the boosted alternating current to the power grid.

[0101] In one embodiment, the output end of the control system 230 is connected with the second input end of the photovoltaic string series number adjusting device 100, and the control system 230 is used to output a preset voltage signal Vdcmax to the photovoltaic string series number adjusting device 100. The photovoltaic string series number adjusting device 100 is used to adjust the series number of each photovoltaic string 211-21n based on the ambient temperature signal T1-Tn under the working condition of each photovoltaic string 211-21n, the output voltage signal VdcS1-VdcSn provided by each photovoltaic string 211-21n, and the preset voltage signal Vdcmax.

[0102] It should be noted that the product model of the inverter 220 is different, the number of MPPT (Maximum Power Point Tracking) is different, and the number of photovoltaic strings that can be connected by the inverter 220 is also different.

[0103] Please refer to Figure 6 , Figure 6 is a step schematic diagram of a photovoltaic string series number adjusting method of a photovoltaic string 210 provided by the embodiment of the present application. The method is realized based on a photovoltaic string series number adjusting device 100 of a photovoltaic string 210, and in combination with Figure 1 and Figure 6 , the method can include the following steps:

[0104] S601, based on the temperature monitoring unit 120, the ambient temperature under the working condition of the photovoltaic string 210 is monitored to obtain an ambient temperature signal T.

[0105] In one embodiment, after the temperature monitoring unit 120 monitors the ambient temperature signal T, the ambient temperature signal T is output to the control unit 110.

[0106] S602, based on the direct current voltage acquisition unit 130, the output voltage signal Vdc of the photovoltaic string 210 is acquired.

[0107] In one embodiment, after the direct current voltage acquisition unit 130 acquires the output voltage signal Vdc, the output voltage signal Vdc is provided to the control unit 110.

[0108] S603, generating control signals UK1-UKn based on the control unit according to the ambient temperature signal T, the output voltage signal Vdc and the preset voltage signal Vdcmax, and outputting corresponding control signals UK1-UKn to the control end of each switching unit, each control signal UK1-UKn being used to control the corresponding switching unit to be turned on or turned off.

[0109] In one embodiment, the control unit 110 generates control signals UK1 and UK2 based on the ambient temperature signal T, the output voltage signal Vdc and the preset voltage signal Vdcmax, and outputs the control signals UK1 and UK2 to the control end of the first switching unit 142 and the second switching unit 144, respectively, the control signals UK1 and UK2 being used to control the first switching unit 142 and the second switching unit 144 to be turned on or turned off, respectively.

[0110] S604, when each switching unit is in the on state, short-circuiting the photovoltaic module connected in parallel with it to reduce the number of series connections of the photovoltaic module string; wherein the photovoltaic module connected in parallel with each switching unit is the corresponding number of group string adjustment photovoltaic module.

[0111] In one embodiment, when the first switching unit 142 and the second switching unit 144 are in the on state, the photovoltaic modules A1, A2, B1 and B2 are short-circuited to reduce the number of series connections of the photovoltaic module string 210; wherein the photovoltaic modules A1, A2, B1 and B2 are the group string number adjustment photovoltaic module 214.

[0112] As shown in Figure 2 The control unit 110 includes a main control module 112, a PWM control module 114, a limit module 116 and a signal superposition module 118. The photovoltaic module string series connection number adjustment device 100 includes a first switching unit 142 and a second switching unit 144, and the group string number adjustment photovoltaic module includes adjacent first to-be-adjusted photovoltaic module A1, second to-be-adjusted photovoltaic module A2, third to-be-adjusted photovoltaic module B1 and fourth to-be-adjusted photovoltaic module B2. The group string number adjustment photovoltaic module 214 is the second part of the photovoltaic module string 210, and the remaining photovoltaic modules are the first part of the photovoltaic module string 210. When the first switching unit 142 and the second switching unit 144 are in the off state, the group string number adjustment photovoltaic module 214 is connected to the first part 212 of the photovoltaic module string 210. The photovoltaic module string series connection number adjustment device 100 further includes a signal input unit 150.

[0113] According to an embodiment of the present application, the control unit 110 generates the control signal U based on the ambient temperature signal T, the output voltage signal Vdc and the preset voltage signal Vdcmax, and when each switching unit is in the on state, the photovoltaic module connected in parallel therewith is short-circuited to reduce the number of series connections of the photovoltaic string, and when each switching unit is in the off state, the number of series connections is adjusted to connect the photovoltaic module 214 to the first part of the photovoltaic string 210, which can include the following steps:

[0114] It should be noted that, under standard test conditions, the test temperature is 25℃, the STC (Standard Test Condition) irradiance is 1000W / m 2 , the number of series connections of the photovoltaic string 210 is N0, at this time, the first switching unit 142 and the second switching unit 144 are both in the off state, the first to-be-adjusted photovoltaic module A1 is connected to the second to-be-adjusted photovoltaic module A2, the third to-be-adjusted photovoltaic module B1 is connected to the fourth to-be-adjusted photovoltaic module B2, and the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2 are simultaneously connected to the first part of the photovoltaic string 210.

[0115] In one embodiment, when the first ambient temperature t1 is less than the standard test temperature 25℃: the main control module 112 compares the first output voltage Vdc1 with the first preset voltage Vdc-max1 (the maximum direct current voltage allowed by the inverter) input by the signal input unit 150 to obtain a first comparison result, which is the absolute value of the difference between the first output voltage Vdc1 and the first preset voltage Vdc-max1. The main control module 112 generates a first main control signal U01 based on the first comparison result, and the limiting module 116 generates a first limiting signal based on the first ambient temperature signal, which is a binary number 1. The signal superposition module 118 performs logical operation and superposition on the first main control signal U01 and the first limiting signal to generate a first modulation signal U11, and the amplitude of the first modulation signal U11 is 1. The PWM control module 114 generates a first drive signal PWM1 (binary number 1) according to the first modulation signal U11, and outputs the first drive signal PWM1 to the control end of the first switching unit 142 and the control end of the second switching unit 144. The PWM control module 114 drives the first switching unit 142 to be on according to the first drive signal PWM1 to short-circuit the first to-be-adjusted photovoltaic module A1 and the second to-be-adjusted photovoltaic module A2, and drives the second switching unit 144 to be off according to the first drive signal PWM1 to simultaneously connect the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2 to the first part of the photovoltaic string 210. At this time, the number of series connections of the photovoltaic string 210 is N1, and N1

[0116] In one embodiment, when the second ambient temperature t2 is less than the first ambient temperature t1: the control unit 110 generates a second control signal based on the second output voltage Vdc2 and the first preset voltage Vdc-max1, and outputs the second control signal to the control end of the first switch unit 142 and the control end of the second switch unit 144. The control unit 110 controls the first switch unit 142 to be off based on the second control signal, and controls the second switch unit 144 to be on based on the second control signal, so as to short-circuit the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2. Wherein, when the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2 are short-circuited, the first to-be-adjusted photovoltaic module A1 and the second to-be-adjusted photovoltaic module A2 are simultaneously disconnected from the first part of the photovoltaic module string 210. At this time, the number of series connection of the photovoltaic module string 210 is N2, N2

[0117] Specifically, when t2

[0118] According to an embodiment of the present application, the control unit 110 generates the control signal U based on the ambient temperature signal T, the output voltage signal Vdc and the preset voltage Vdc-max signal Vdcmax, and shorts the photovoltaic module connected in parallel with each switching unit when the switching unit is in the on state, and adjusts the number of strings to connect the photovoltaic module 214 to the first part of the photovoltaic string 210 when the switching unit is in the off state, which can further include the following steps:

[0119] In one embodiment, when the third ambient temperature t3 is greater than the second ambient temperature t2: the equivalent open circuit voltage Vdc` of the photovoltaic string 210 is reduced due to the influence of the open circuit voltage temperature coefficient Kv of the photovoltaic string 210. The main control module 112 compares the third output voltage Vdc3 with the second preset voltage Vdc-max2 to obtain a third comparison result. If the third comparison result is that the third output voltage Vdc3 is less than the second preset voltage Vdc-max2 (the difference between the first preset voltage Vdc-max1 and twice the equivalent open circuit voltage Vdc` of the photovoltaic string 210, i.e. Vdc-max2 = Vdc-max1 - 2 x Vdc`, and Vdc-max2 can also be understood as the minimum DC input voltage allowed by the inverter), the main control module 112 generates a third main control signal U03 based on the absolute value of the difference between the third output voltage Vdc3 and the second preset voltage Vdc-max2, and the limit module 116 generates a third limit signal based on the third ambient temperature signal, the third limit signal being a binary number 1. The signal superposition module 118 performs logical operation and superposition on the third main control signal U03 and the third limit signal to generate a third modulation signal U13, and the amplitude of the third modulation signal U13 is 1. The PWM control module 114 generates a third drive signal PWM3 (binary number 1) based on the third modulation signal U13, and outputs the third drive signal PWM3 to the control end of the first switching unit 142 and the control end of the second switching unit 144. The PWM control module 114 drives the first switching unit 142 to be on based on the third drive signal PWM3 to short the first to be adjusted photovoltaic module A1 and the second to be adjusted photovoltaic module A2, and drives the second switching unit 144 to be off based on the third drive signal to connect the third to be adjusted photovoltaic module B1 and the fourth to be adjusted photovoltaic module B2 to the first part of the photovoltaic string 210. At this time, the number of series connections of the photovoltaic string 210 is N3, N3 = N1.

[0120] In one embodiment, when the fourth ambient temperature t4 is greater than or equal to the standard test temperature 25℃: the control unit 110 generates the fourth control signal based on the fourth output voltage Vdc4 and the second preset voltage Vdc-max2, and outputs the fourth control signal to the control end of the first switch unit 142 and the control end of the second switch unit 144. The control unit 110 controls the first switch unit 142 and the second switch unit 144 to be off based on the fourth control signal, so as to connect the first to-be-adjusted photovoltaic module A1, the second to-be-adjusted photovoltaic module A2, the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2 to the first part of the photovoltaic string 210. At this time, the number of series connection of the photovoltaic string 210 is N4, N4=N0.

[0121] Specifically, when t4≥25℃: the equivalent open circuit voltage Vdc' of the photovoltaic string 210 decreases due to the influence of the open circuit voltage temperature coefficient Kv of the photovoltaic string 210. The main control module 112 compares the fourth output voltage Vdc4 with the second preset voltage Vdc-max2 to obtain a fourth comparison result. If the fourth comparison result is that the fourth output voltage Vdc4 is less than the second preset voltage Vdc-max2, the main control module 112 generates a fourth main control signal U04 based on the absolute value of the difference between the fourth output voltage Vdc4 and the second preset voltage Vdc-max2, and the limiting module 116 generates a fourth limiting signal based on the fourth ambient temperature signal, the fourth limiting signal being a binary number 0. The signal superposition module 118 performs logical operation and superposition on the fourth main control signal U04 and the fourth limiting signal to generate a fourth modulation signal U14, the amplitude of the fourth modulation signal U14 being 0. The PWM control module 114 generates a fourth driving signal PWM4 (binary number 0) based on the fourth modulation signal U14, and outputs the fourth driving signal PWM4 to the control end of the first switch unit 142 and the control end of the second switch unit 144. The control unit 110 drives the first switch unit 142 and the second switch unit 144 to be off based on the fourth driving signal PWM4, so as to connect the first to-be-adjusted photovoltaic module A1, the second to-be-adjusted photovoltaic module A2, the third to-be-adjusted photovoltaic module B1 and the fourth to-be-adjusted photovoltaic module B2 to the first part of the photovoltaic string 210. At this time, the number of series connection of the photovoltaic string 210 is N4, N4=N0.

[0122] Please refer to Figure 7 , Figure 7 is a schematic diagram of the steps of the method for adjusting the number of series connection of the plurality of photovoltaic strings 211-21n provided by the embodiments of the present application. The method is implemented based on the device 100 for adjusting the number of series connection of the plurality of photovoltaic strings 211-21n, as shown in Figure 7 , the method can include the following steps:

[0123] S701, monitoring the ambient temperature of each photovoltaic string 211-21n under working condition by the temperature monitoring unit 120, obtaining a plurality of ambient temperature signals T1-Tn.

[0124] S702, collecting the output voltage signals VdcS1-VdcSn of each photovoltaic string 211-21n by the DC voltage collection unit 130.

[0125] S703, generating the control signals UK1-UKn according to the ambient temperature signals T1-Tn, the output voltage signals VdcS1-VdcSn and the preset voltage signal Vdcmax by the control unit 110, and outputting the corresponding control signals UK1-UKn to the control end of each switching unit, each control signal UK1-UKn being used to control the corresponding switching unit to be turned on or turned off.

[0126] S704, short-circuiting the photovoltaic module in parallel with each switching unit when the switching unit is in the on state, so as to reduce the series number of the corresponding photovoltaic string 211-21n; wherein the photovoltaic module in parallel with each switching unit is the corresponding number of string adjustment photovoltaic module.

[0127] It should be noted that the specific implementation process of the photovoltaic string series number adjustment method of the plurality of photovoltaic strings 211-21n is substantially the same as that of the photovoltaic string series number adjustment method of the photovoltaic string 210, which will not be described here.

[0128] The photovoltaic string series quantity adjusting device 100 and method provided by the embodiment of the present application can adjust the series quantity of one photovoltaic string 210 or the series quantity of multiple photovoltaic strings 211-21n. When the series quantity of one photovoltaic string 210 is adjusted, the temperature monitoring unit 120 obtains an ambient temperature signal T by monitoring the ambient temperature under the working condition of the photovoltaic string 210, the direct current voltage acquisition unit 130 acquires an output voltage signal Vdc of the photovoltaic string 210, the control unit 110 generates control signals UK1-UKn based on the ambient temperature signal T, the output voltage signal Vdc and a preset voltage signal Vdcmax, controls the corresponding switching unit to be turned on or turned off based on the control signals UK1-UKn, and each switching unit adjusts the series quantity of the photovoltaic string 210 by short-circuiting the photovoltaic module connected in parallel therewith. When the series quantity of multiple photovoltaic strings 211-21n is adjusted, the temperature monitoring unit 120 obtains multiple ambient temperature signals T1-Tn by monitoring the ambient temperature under the working condition of each photovoltaic string 211-21n, the direct current voltage acquisition unit 130 acquires output voltage signals VdcS1-VdcSn of each photovoltaic string 211-21n, the control unit 110 generates control signals UK1-UKn based on the ambient temperature signals T1-Tn, the output voltage signals VdcS1-VdcSn and the preset voltage signal Vdcmax, controls each switching unit to be turned on or turned off based on each control signal UK1-UKn, and each switching unit adjusts the series quantity of the corresponding photovoltaic string 211-21n by connecting or disconnecting the photovoltaic module connected in parallel therewith and the first part 212 of the corresponding photovoltaic string 211-21n.

[0129] The scheme of the embodiment of the present application sets the switching unit at least at one place in each photovoltaic string 211-21n, can automatically and flexibly adjust the series quantity of the corresponding photovoltaic string 211-21n at different ambient temperatures by using each switching unit, and is not limited by the minimum temperature under the working condition of the photovoltaic string 211-21n. Under the premise of meeting the maximum direct current input voltage allowed by the inverter, the maximum series quantity can be ensured, the number of inverters and photovoltaic supports is reduced, the floor area of the photovoltaic plant is also reduced, and the investment of the photovoltaic project is reduced. In addition, the power generation of the photovoltaic power generation system 200 is increased, the economic performance of the photovoltaic project is improved, and the scheme has strong usability and practicality.

[0130] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, 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 embodiment of the present application.

[0131] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in a certain embodiment can be referred to the relevant description of other embodiments.

[0132] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some technical features can be replaced by equivalents; 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 photovoltaic string series quantity adjustment device, characterized in that: The device comprises: a control unit, a temperature monitoring unit, a DC voltage acquisition unit and a switch unit; The output end of the temperature monitoring unit is connected to the first input end of the control unit, and the temperature monitoring unit is used to monitor the ambient temperature under the working conditions of the photovoltaic strings to obtain an ambient temperature signal; The input end of the DC voltage acquisition unit is connected to the DC output end of the photovoltaic string, the output end of the DC voltage acquisition unit is connected to the second input end of the control unit, and the DC voltage acquisition unit is used to acquire the output voltage signal of the photovoltaic string; In a photovoltaic string consisting of N photovoltaic modules connected in series, the switch unit is provided at at least one location. Each switch unit is connected in parallel to at least one photovoltaic module. The control end of the switch unit is connected to the output end of the control unit. When the switch unit is in the conducting state, the photovoltaic module connected in parallel is short-circuited to reduce the number of photovoltaic strings connected in series. The photovoltaic assembly connected in parallel with the switch unit is a string quantity adjustment photovoltaic assembly.

2. The photovoltaic string series quantity adjustment device according to claim 1, characterized in that: The photovoltaic assembly for adjusting the number of strings includes a first photovoltaic assembly to be adjusted, a second photovoltaic assembly to be adjusted, a third photovoltaic assembly to be adjusted, and a fourth photovoltaic assembly to be adjusted, which are adjacent to each other; The photovoltaic components for adjusting the number of strings are the second part of the photovoltaic string, and the remaining photovoltaic components are the first part of the photovoltaic string. When the switch unit is in the off state, the photovoltaic components to be adjusted are connected to the first part of the photovoltaic string.

3. The photovoltaic string series quantity adjustment device according to claim 1, characterized in that: The control unit includes: a main control module and a PWM control module; The first input end of the main control module is connected to the output end of the temperature monitoring unit, the second input end of the main control module is connected to the output end of the DC voltage acquisition unit, the output end of the main control module is connected to the input end of the PWM control module, and the output end of the PWM control module is connected to the control end of the switch unit.

4. The photovoltaic string series quantity adjustment device according to claim 3, characterized in that: The control unit further includes: a limit module and a signal superposition module; The input end of the limit module is connected to the output end of the temperature monitoring unit, the output end of the limit module is connected to the first input end of the signal superposition module, the second input end of the signal superposition module is connected to the output end of the main control module, and the output end of the signal superposition module is connected to the input end of the PWM control module.

5. The photovoltaic string series quantity adjustment device according to claim 2, characterized in that: The device comprises: a first switch unit and a second switch unit; The control end of the first switch unit is connected to the first output end of the control unit, the first controlled end of the first switch unit is connected to the negative electrode of the first photovoltaic component to be regulated, and the second controlled end of the first switch unit is connected to the positive electrode of the second photovoltaic component to be regulated. The first switch unit is used to short-circuit the first photovoltaic component to be regulated and the second photovoltaic component to be regulated when it is in the on state, or to connect the first photovoltaic component to be regulated with the second photovoltaic component to be regulated, and to connect the third photovoltaic component to be regulated with the fourth photovoltaic component to be regulated when it is in the off state; The control end of the second switch unit is connected to the second output end of the control unit, the first controlled end of the second switch unit is connected to the negative electrode of the third photovoltaic assembly to be regulated, and the second controlled end of the second switch unit is connected to the positive electrode of the fourth photovoltaic assembly to be regulated. The second switch unit is used to short-circuit the third photovoltaic assembly to be regulated and the fourth photovoltaic assembly to be regulated when in the on state, or to connect the third photovoltaic assembly to be regulated and the fourth photovoltaic assembly to be regulated to the first part of the photovoltaic string at the same time when in the off state; Wherein, when the third photovoltaic assembly to be adjusted and the fourth photovoltaic assembly to be adjusted are short-circuited, the first photovoltaic assembly to be adjusted and the second photovoltaic assembly to be adjusted are simultaneously disconnected from the first part of the photovoltaic string.

6. The photovoltaic string series quantity adjustment device according to claim 5, characterized in that: The first switch unit includes: a first switch device and a first diode, and the second switch unit includes: a second switch device and a second diode; The control end of the first switching device is connected to the first output end of the control unit, the first controlled end of the first switching device is connected to the negative electrode of the first photovoltaic component to be regulated, the second controlled end of the first switching device is connected to the anode of the first diode, the cathode of the first diode is connected to the positive electrode of the second photovoltaic component to be regulated, and the first diode is used to prevent current from flowing from the positive electrode of the second photovoltaic component to be regulated to the negative electrode of the first photovoltaic component to be regulated; The control end of the second switching device is connected to the second output end of the control unit, the first controlled end of the second switching device is connected to the negative electrode of the third photovoltaic component to be regulated, the second controlled end of the second switching device is connected to the anode of the second diode, the cathode of the second diode is connected to the positive electrode of the fourth photovoltaic component to be regulated, and the second diode is used to prevent current from flowing from the positive electrode of the fourth photovoltaic component to be regulated to the negative electrode of the third photovoltaic component to be regulated.

7. The photovoltaic string series quantity adjustment device according to claim 1, characterized in that: The device further comprises a signal input unit; The input end of the signal input unit is connected to the output end of the control system, and the output end of the signal input unit is connected to the third input end of the control unit. The signal input unit is used to input the preset voltage signal output by the control system and output the preset voltage signal to the control unit.

8. The photovoltaic string series quantity adjustment device according to any one of claims 1 to 7, characterized in that: The device includes: a control unit, a temperature monitoring unit, a DC voltage acquisition unit, and multiple switch units; wherein the DC voltage acquisition unit includes multiple input terminals and multiple output terminals, the control unit includes multiple second input terminals and multiple output terminals, and there are multiple photovoltaic strings connected to the input terminals of the DC voltage acquisition unit; The output end of the temperature monitoring unit is connected to the first input end of the control unit, and the temperature monitoring unit is used to monitor the ambient temperature of each photovoltaic string under working conditions to obtain multiple ambient temperature signals; Each input terminal of the DC voltage acquisition unit is connected to the DC output terminal of the corresponding photovoltaic string, and each output terminal of the DC voltage acquisition unit is connected to the corresponding second input terminal of the control unit. The DC voltage acquisition unit is used to collect the output voltage signal of each photovoltaic string; In each photovoltaic string consisting of N photovoltaic modules connected in series, the switch unit is provided at least at one location. Each switch unit is connected in parallel to at least one photovoltaic module. The control end of each switch unit is connected to the corresponding output end of the control unit. When each switch unit is in the on state, the photovoltaic module connected in parallel with it is short-circuited to reduce the number of series connections of the corresponding photovoltaic string. The photovoltaic components connected in parallel with each switch unit are corresponding photovoltaic components to be adjusted.

9. A photovoltaic power generation system, characterized in that: The system comprises: a photovoltaic string, an inverter, a box-type transformer AC device, a control system, and a photovoltaic string series quantity adjustment device according to any one of claims 1 to 7; The DC input end of the photovoltaic string is connected to the output end of the photovoltaic string series quantity adjustment device, and the DC output end of the photovoltaic string is connected to the power supply input end of the inverter and the first input end of the photovoltaic string series quantity adjustment device. The photovoltaic string is used to provide an output voltage signal to the photovoltaic string series quantity adjustment device and output DC power after adjusting the number of photovoltaic strings in series to the inverter; The output of the inverter is connected to the input of the box-type transformer AC device. The inverter is used to convert the DC power output by the photovoltaic strings into AC power and output the AC power to the box-type transformer AC device. The output end of the box-type AC device is connected to the input end of the power grid. The box-type AC device is used to collect and boost the AC power output by the inverter and output the boosted AC power to the power grid. The output end of the control system is connected to the second input end of the photovoltaic string series quantity adjustment device, and the control system is used to output a preset voltage signal to the photovoltaic string series quantity adjustment device; The photovoltaic string series number adjustment device is used to adjust the number of photovoltaic strings connected in series based on the ambient temperature signal under the working conditions of the photovoltaic strings, the output voltage signal provided by the photovoltaic strings, and the preset voltage signal.

10. The photovoltaic power generation system according to claim 9, characterized in that: The system includes: multiple photovoltaic strings, an inverter, a box-type transformer AC device, a control system, and a photovoltaic string series quantity adjustment device; wherein the photovoltaic string series quantity adjustment device includes multiple first input terminals, second input terminals, and multiple output terminals, and the inverter includes multiple power supply input terminals; The DC input end of each photovoltaic string is connected to the corresponding output end of the photovoltaic string series quantity adjustment device, and the DC output end of each photovoltaic string is connected to the corresponding power supply input end of the inverter and the corresponding first input end of the photovoltaic string series quantity adjustment device. Each photovoltaic string is used to provide a corresponding output voltage signal to the photovoltaic string series quantity adjustment device and output the corresponding DC power after adjusting the number of photovoltaic strings in series to the inverter; The output of the inverter is connected to the input of the box-type transformer AC device. The inverter is used to convert the DC power output by each photovoltaic string into AC power and output the AC power to the box-type transformer AC device. The output end of the box-type AC device is connected to the input end of the power grid. The box-type AC device is used to collect and boost the AC power output by the inverter and output the boosted AC power to the power grid. The output end of the control system is connected to the second input end of the photovoltaic string series quantity adjustment device, and the control system is used to output a preset voltage signal to the photovoltaic string series quantity adjustment device; The photovoltaic string series number adjustment device is used to adjust the number of photovoltaic strings connected in series based on the ambient temperature signal under the working conditions of each photovoltaic string, the output voltage signal provided by each photovoltaic string, and the preset voltage signal.

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