Device and system for adjusting and controlling serial connection number of photovoltaic strings

Abstract

The utility model provides a photovoltaic string series connection number adjustment control device and control system, and belongs to the technical field of photovoltaic power generation, and the device comprises a temperature monitoring unit which obtains a temperature signal through monitoring, and a DC voltage collection unit which collects an output voltage signal of a photovoltaic string; the difference superposition unit obtains a first type of difference results, or obtains a second type of difference results while obtaining the first type of difference results, and superposes the first type of difference results and the second type of difference results to obtain superposed signals; the control unit generates a first control signal according to the first-class difference result, or generates a second control signal according to the superposed signal, and controls the corresponding switch unit to be turned on or turned off based on the first control signal or the second control signal; in the photovoltaic group strings, when each switch unit is in a conducting state, the photovoltaic modules connected with the switch units in parallel are short-circuited, so that the number of the photovoltaic group strings connected in series is reduced. According to the scheme, the series connection number of the photovoltaic strings can be flexibly and accurately adjusted.

Description

TECHNICAL FIELD

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

[0002] The photovoltaic string series connection number is determined by the minimum temperature under the working condition of the photovoltaic string, the lower the daytime minimum temperature of the photovoltaic field area, the fewer the photovoltaic string series connection number, the lower the output voltage of the photovoltaic string, and the lower the power generation of the photovoltaic string series connection number adjustment control system. The photovoltaic string is in standby state when the minimum temperature appears all day, so the minimum temperature under the working condition of the photovoltaic string is higher than the minimum temperature all day.

[0003] 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 change, the sunrise and sunset time also changes constantly, so that the time when the minimum temperature appears in a day also changes constantly with the season. Therefore, adjusting the photovoltaic string series connection number according to the minimum temperature will lead to the decrease of the power generation of the photovoltaic string series connection number adjustment control system.

[0004] Therefore, how to flexibly and accurately adjust the series connection 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 connection number adjustment control device, which can solve the problem of how to flexibly and accurately adjust the series connection number of the photovoltaic string in the prior art.

[0006] In a first aspect, the embodiments of the present application provide a photovoltaic string series connection number adjustment control device, which comprises a difference subtraction and superposition unit, a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a switching unit.

[0007] The first output end of the temperature monitoring unit is connected with the first input end of the control unit, the second output end of the temperature monitoring unit is connected with the first input end of the difference subtraction and superposition unit, and the temperature monitoring unit is used for monitoring the environmental temperature under the working condition of the photovoltaic string to obtain a temperature signal.

[0008] The input end of the direct current voltage acquisition unit is connected with the direct current output end of the photovoltaic string, the first output end of the direct current voltage acquisition unit is connected with the second input end of the difference subtraction and superposition unit, the second output end of the direct current voltage acquisition unit is connected with the third input end of the difference subtraction and superposition unit, and the direct current voltage acquisition unit is used for acquiring the output voltage signal of the photovoltaic string.

[0009] A fourth input end of the difference superposition unit is connected with an output end of a control system in the series number adjustment control system, an output end of the difference superposition unit is connected with a second input end of the control unit, the difference superposition unit is used for subtracting the output voltage signal from the preset voltage signal output by the control system to obtain a first type of difference result, or at the same time, subtracting the output voltage signal from the lowest output voltage signal to obtain a second type of difference result, superimposing the first type of difference result and the second type of difference result to obtain a superimposed signal;

[0010] An output end of the control unit is connected with a control end of the switching unit, the control unit is used for generating a first control signal according to the first type of difference result, or generating a second control signal according to the superimposed signal, and controlling the corresponding switching unit to be turned on or turned off based on the first control signal or the second control signal;

[0011] In the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at at least one position, each switching unit is connected in parallel with at least one photovoltaic component, and when each switching unit is in an on state, the photovoltaic component connected in parallel with the switching unit is short-circuited to reduce the series number of the photovoltaic string.

[0012] The photovoltaic component connected in parallel with each switching unit is a string number adjustment photovoltaic component.

[0013] In a possible implementation of the first aspect, the string number adjustment photovoltaic component includes: adjacent first, second, third and fourth to-be-adjusted photovoltaic components.

[0014] The string number adjustment photovoltaic component is a second part of the photovoltaic string, and the remaining photovoltaic components are a first part of the photovoltaic string, and when the switching unit is in an off state, the to-be-adjusted photovoltaic component is connected to the first part of the photovoltaic string.

[0015] In a possible implementation of the first aspect, the difference superposition unit includes: a first difference module, a lowest voltage calculation module, a second difference module and a result superposition module.

[0016] A first input end of the first difference module is connected with a first output end of the direct-current voltage acquisition unit, a second input end of the first difference module is connected with an output end of the control system, and an output end of the first difference module is connected with a first input end of the result superposition module, the first difference module is used for subtracting the output voltage signal from the preset voltage signal to obtain the first type of difference result.

[0017] The first input end of the minimum voltage calculation module is connected with the second output end of the temperature monitoring unit, the second input end of the minimum voltage calculation module is connected with the output end of the control system, the output end of the minimum voltage calculation module is connected with the first input end of the second difference module, and the minimum voltage calculation module is used for calculating the minimum output voltage according to the temperature signal, the preset voltage signal and the equivalent open circuit voltage of the component, so as to obtain the minimum output voltage signal;

[0018] The second input end of the second difference module is connected with the second output end of the direct current voltage acquisition unit, and the output end of the second difference module is connected with the second input end of the result superposition module. The second difference module is used for subtracting the output voltage signal from the minimum output voltage signal to obtain a second type of difference result.

[0019] The output end of the result superposition module is connected with the second input end of the control unit, and the result superposition module is used for superimposing the first type of difference result and the second type of difference result to obtain a superimposed signal.

[0020] In a possible implementation of the first aspect, the control unit comprises a main control module, a limit module, a signal superposition module and a PWM control module.

[0021] The input end of the main control module is connected with the output end of the difference superposition unit, the output end of the main control module is connected with the first input end of the signal superposition module, and the main control module is used for generating a first type of main control signal based on the first type of difference result or generating a second type of main control signal based on the superimposed signal.

[0022] The input end of the limit module is connected with the first input end of the temperature monitoring unit, the output end of the limit module is connected with the second input end of the signal superposition module, and the limit module is used for generating a first limit signal or a second limit signal based on the temperature signal.

[0023] The output end of the signal superposition module is connected with the input end of the PWM control module, the output end of the PWM control module is connected with the control end of each switch unit, and the signal superposition module is used for performing logical operation and superposition on the temperature signal and the first type of main control signal to generate a first type of modulation signal based on the second limit signal, or performing logical operation and superposition on the temperature signal and the second type of main control signal to generate a second type of modulation signal.

[0024] The PWM control module is used for generating a first type of driving signal based on the first type of modulation signal or generating a second type of driving signal based on the second type of modulation signal, and controlling each switch unit to be turned on or turned off based on the first type of driving signal or the second type of driving signal.

[0025] In a possible implementation of the first aspect, the device comprises a first switch unit and a second switch unit.

[0026] The control end of the first switch unit is connected with the first output end of the control unit, the first controlled end of the first switch unit is connected with the negative electrode of the first photovoltaic module to be adjusted, the second controlled end of the first switch unit is connected with the positive electrode of the second photovoltaic module to be adjusted, and the first switch unit is used for short-circuiting the first photovoltaic module to be adjusted and the second photovoltaic module to be adjusted when being in the on state, or connecting the first photovoltaic module to be adjusted and the second photovoltaic module to be adjusted and connecting the third photovoltaic module to be adjusted and the fourth photovoltaic module to be adjusted when being in the off state;

[0027] The control end of the second switch unit is connected with the second output end of the control unit, the first controlled end of the second switch unit is connected with the negative electrode of the third photovoltaic module to be adjusted, the second controlled end of the second switch unit is connected with the positive electrode of the fourth photovoltaic module to be adjusted, and the second switch unit is used for short-circuiting the third photovoltaic module to be adjusted and the fourth photovoltaic module to be adjusted when being in the on state, or connecting the third photovoltaic module to be adjusted and the fourth photovoltaic module to be adjusted with the first part of the photovoltaic string at the same time when being in the off state;

[0028] Wherein, the first photovoltaic module to be adjusted and the second photovoltaic module to be adjusted are disconnected with the first part of the photovoltaic string at the same time when the third photovoltaic module to be adjusted and the fourth photovoltaic module to be adjusted are short-circuited.

[0029] In a possible implementation 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;

[0030] The control end of the first switch device is connected with the first output end of the control unit, the first controlled end of the first switch device is connected with the negative electrode of the first photovoltaic module to be adjusted, the second controlled end of the first switch device is connected with the anode of the first diode, the cathode of the first diode is connected with the positive electrode of the second photovoltaic module to be adjusted, and the first diode is used for preventing 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;

[0031] The control end of the second switch device is connected with the second output end of the control unit, the first controlled end of the second switch device is connected with the negative electrode of the third photovoltaic module to be adjusted, the second controlled end of the second switch device is connected with the anode of the second diode, the cathode of the second diode is connected with the positive electrode of the fourth photovoltaic module to be adjusted, and the second diode is used for preventing 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.

[0032] In a possible implementation of the first aspect, the device further comprises a signal input unit;

[0033] The input end of the signal input unit is connected with the output end of the control system, the output end of the signal input unit is connected with the fourth input end of the difference superposition unit, and the signal input unit is used for inputting the preset voltage signal output by the control system and outputting the preset voltage signal to the difference superposition unit.

[0034] In a possible implementation of the first aspect, the device comprises a difference superposition unit, 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 first output ends and second output ends, the difference superposition unit comprises a plurality of second input ends and third input ends, the control unit comprises a plurality of output ends, and the photovoltaic string connected with the input end of the direct current voltage acquisition unit has a plurality of photovoltaic strings.

[0035] The first output end of the temperature monitoring unit is connected with the first input end of the control unit, and the second output end of the temperature monitoring unit is connected with the first input end of the difference superposition unit; the temperature monitoring unit is used for monitoring the ambient temperature under the working condition of each photovoltaic string to obtain a plurality of temperature signals.

[0036] Each input end of the direct current voltage acquisition unit is connected with the direct current output end of the corresponding photovoltaic string, each first output end of the direct current voltage acquisition unit is connected with each second input end of the difference superposition unit, and each second output end of the direct current voltage acquisition unit is connected with each third input end of the difference superposition unit; the direct current voltage acquisition unit is used for acquiring the output voltage signal of each photovoltaic string.

[0037] The fourth input end and the fifth input end of the difference superposition unit are connected with the output end of the external control system, and the output end of the difference superposition unit is connected with the second input end of the control unit; the difference superposition unit is used for performing difference operation on the output voltage signal of each photovoltaic string and the preset voltage signal to obtain a plurality of first difference results, or simultaneously performing difference operation on each output voltage signal and the lowest output voltage signal to obtain a plurality of second difference results, superimposing each first difference result and each second difference result to obtain a plurality of superimposed signals.

[0038] The output end of the control unit is connected with the control end of the switch unit, and the control unit is used for generating a corresponding first control signal according to each first difference result, or generating a corresponding second control signal according to each superimposed signal, and controlling the corresponding switch unit to be turned on or turned off according to the first control signal and the second control signal.

[0039] 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 with at least one photovoltaic module, and when each switching unit is in an on state, the photovoltaic module connected in parallel with the switching unit is short-circuited to reduce the series number of the corresponding photovoltaic module string; wherein the photovoltaic module connected in parallel with each switching unit is the corresponding number of photovoltaic module adjustment photovoltaic module.

[0040] In a second aspect, the embodiments of the present application provide a photovoltaic module string series number adjustment control system, which comprises a photovoltaic module string, an inverter, a box transformer alternating current device, a control system, and a photovoltaic module string series number adjustment control device.

[0041] The direct current input end of the photovoltaic module string is connected with the output end of the photovoltaic module string series number adjustment control device, the direct current output end of the photovoltaic module string is connected with the power supply input end of the inverter and the first input end of the photovoltaic module string series number adjustment control device, and the photovoltaic module string is used to provide an output voltage signal to the photovoltaic module string series number adjustment control device and output the direct current after adjusting the series number of the photovoltaic module string to the inverter.

[0042] The output end of the inverter is connected with the input end of the box transformer alternating current device, and 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.

[0043] 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 to collect and boost the alternating current output by the inverter and output the boosted alternating current to the power grid.

[0044] The output end of the control system is connected with the second input end of the photovoltaic module string series number adjustment control device, and the control system is used to output a preset voltage signal to the photovoltaic module string series number adjustment control device.

[0045] The photovoltaic module string series number adjustment control 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.

[0046] In a possible implementation 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 a photovoltaic module string series number adjustment control device; wherein the photovoltaic module string series number adjustment control 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.

[0047] The direct current input end of each photovoltaic string is connected with the output end corresponding to the photovoltaic string series number adjusting control device, the direct current output end of each photovoltaic string is connected with the power supply input end corresponding to the inverter and the first input end corresponding to the photovoltaic string series number adjusting control device, and each photovoltaic string is used for providing the corresponding output voltage to the photovoltaic string series number adjusting control device and outputting the corresponding direct current after adjusting the series number of the photovoltaic string to the inverter;

[0048] The output end of the inverter is connected with the input end of the box transformer alternating current device, and the inverter is used for converting the direct current output by each photovoltaic string into alternating current and outputting the alternating current to the box transformer alternating current device;

[0049] 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;

[0050] The output end of the control system is connected with the second input end of the photovoltaic string series number adjusting control device, and the control system is used for outputting a preset voltage signal to the photovoltaic string series number adjusting control device;

[0051] The photovoltaic string series number adjusting control device is used for adjusting the series number of each photovoltaic string based on the ambient temperature signal under the working condition of each photovoltaic string, the output voltage signal provided by each photovoltaic string and the preset voltage signal.

[0052] The temperature monitoring unit in the scheme monitors the ambient temperature under the working condition of the photovoltaic string to obtain a temperature signal, and the direct current voltage acquisition unit acquires the output voltage signal of the photovoltaic string; the difference subtraction and superposition unit subtracts the output voltage signal from the preset voltage signal output by the control system to obtain a first type of difference result, or subtracts the output voltage signal from the lowest output voltage signal at the same time to obtain a second type of difference result, superimposes the first type of difference result and the second type of difference result to obtain a superimposed signal; the control unit generates a first control signal according to the first type of difference result, or generates a second control signal according to the superimposed signal, and controls the corresponding switching unit to be turned on or turned off based on the first control signal or the second control signal; in the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at at least one place, each switching unit is connected in parallel with at least one photovoltaic component, and when each switching unit is in the on state, the photovoltaic component connected in parallel with the switching unit is short-circuited to reduce the series number of the photovoltaic string.

[0053] The scheme sets the switching unit at at least one place in the photovoltaic string, which can automatically and flexibly adjust the series number of the photovoltaic string under different ambient temperatures, is not limited by the lowest temperature under the working condition of the photovoltaic string, has strong ease of use and practicality, and has strong ease of use and practicality.

[0054] Other features and advantages of the embodiments of the present application will be described in detail in the following specific embodiments section. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present 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 present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0056] Figure 1 is a schematic block diagram of a photovoltaic string series number adjustment control device of a photovoltaic string provided by the embodiments of the present application;

[0057] Figure 2 is a schematic block diagram of a specific structure of a photovoltaic string series number adjustment control device of a photovoltaic string provided by the embodiments of the present application;

[0058] Figure 3 is a schematic block diagram of a specific structure of a photovoltaic string series number adjustment control device of a photovoltaic string provided by the embodiments of the present application;

[0059] Figure 4 is a schematic block diagram of an overall structure of a photovoltaic string series number adjustment control device of a plurality of photovoltaic strings provided by the embodiments of the present application;

[0060] Figure 5 is a schematic block diagram of a photovoltaic string series number adjustment control system including a photovoltaic string provided by the embodiments of the present application;

[0061] Figure 6 is a schematic block diagram of a photovoltaic string series number adjustment control system including a plurality of photovoltaic strings provided by the embodiments of the present application. DETAILED DESCRIPTION

[0062] In the following description, specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art will understand that the present application can be practiced without these specific details. In other instances, well-known systems, devices, circuits, and methods have not been described in detail so as not to obscure the description of the present application.

[0063] It should be understood that the terms "comprises", "comprising", "includes", "including", "has", "having", "contains" and "containing", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0064] It should also be understood that the terms used in the specification and the appended claims are intended to describe certain embodiments and do not intentionally limit the application. As used in the 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.

[0065] It will be further understood that the terms "and / or", as used in the specification and the appended claims, as used in the specification and the appended claims, means any one of the associated listed items or a combination of any of the associated listed items.

[0066] As used in the specification and the appended claims, the term "if' can be construed to mean "when" or "once" or "in response to determining" or "in response to detecting" 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 "once it is determined" or "in response to determining" or "once [the described condition or event] is detected" or "in response to detecting [the described condition or event]," depending on the context.

[0067] 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.

[0068] The use of the terms "a" and "an" and "the" and "said" herein is intended to include the plural, unless the context clearly indicates otherwise. For example, the terms "a" and "an" and "the" and "said" are open, which means that there is at least one of the features, integers, steps, operations, elements, and / or components being referred to. In the disclosure provided herein, relational terms such as "first" and "second" and the like can be used solely to distinguish one entity or action from another entity or action without necessarily implying any relative importance or order.

[0069] In the present specification, the orientation words such as "up", "down", "left", "right" are used generally based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship commonly used when the product of the application is used, unless otherwise specified.

[0070] In the present application, it should be noted that unless specifically defined and limited, the terms "set", "install", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between 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.

[0071] With the rapid development of the current economy, the global demand for energy is increasing day by day, but the resulting fossil energy shortage and environmental pollution problems have gradually emerged, 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. Wind energy, solar energy, biomass energy, ocean energy and other new energy sources have the characteristics of being clean, safe and renewable, and their position in the energy strategy of various countries is constantly improving. 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.

[0072] 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 string series series number adjustment control 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 and other parameters. 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.

[0073] The number of photovoltaic string series refers to the number of photovoltaic modules in series N in each photovoltaic string, which can be calculated according to the following formula:

[0074] (Formula 1)

[0075] (Formula 2)

[0076] 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 the photovoltaic module (N is an integer), T' represents the lowest temperature under the working condition of the photovoltaic string, T'' represents the highest temperature under the working condition of the photovoltaic string, Vdcmax represents the maximum DC input voltage allowed by the inverter, Vmpptmax represents the maximum value of the MPPT (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).

[0077] In order to achieve the technical and economic optimization, the ground photovoltaic power station generally adopts the maximum photovoltaic string series number design, at this time only formula 1 needs to be calculated. The distributed photovoltaic string series number adjustment and control system combined with buildings generally does not use the maximum photovoltaic string series number design, at this time formula 1 and formula 2 need to be considered comprehensively to obtain the range of the photovoltaic string series number.

[0078] 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 photovoltaic string series number N is proportional to the environmental temperature T. Assuming that the system voltage is 1500V, i.e. the maximum DC input voltage Vdcmax allowed by the inverter is 1500V, with reference to the parameters of a certain brand of photovoltaic module, under the standard test condition, 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 environmental temperature T under the working condition of the photovoltaic string is 25℃, the photovoltaic string series number N is calculated to be 30 pieces by formula 1. Table 1 is a table of the values of the photovoltaic string series number N under different environmental temperatures, and the photovoltaic string series number N under different environmental temperatures is shown in Table 1.

[0079] From Table 1 and the characteristics of the photovoltaic module, the voltage of the photovoltaic module under sunlight will decrease with the increase of the environmental temperature, and the open-circuit voltage of the photovoltaic string will decrease with the increase of the environmental 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 with the decrease of the environmental temperature. In order to ensure that the inverter can work normally and continuously at the local minimum temperature, the influence of the local minimum temperature 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 environmental temperature T should be selected as the lowest temperature under the working condition of the photovoltaic string.

[0080] Table 1

[0081] Serial number T Voc Kv Equivalent open circuit voltage Voc' of the photovoltaic string Vdcmax N N rounded 1 45 50 -0.0026 47.4 1500 31.65 30 2 40 50 -0.0026 48.05 1500 31.22 30 3 35 50 -0.0026 48.7 1500 30.80 30 4 30 50 -0.0026 49.35 1500 30.40 30 5 25 50 -0.0026 50 1500 30.00 30 6 20 50 -0.0026 50.65 1500 29.62 28 7 15 50 -0.0026 51.3 1500 29.24 28 8 10 50 -0.0026 51.95 1500 28.87 28 9 5 50 -0.0026 52.6 1500 28.52 28 10 0 50 -0.0026 53.25 1500 28.17 28 11 -5 50 -0.0026 53.9 1500 27.83 26 12 -10 50 -0.0026 54.55 1500 27.50 26 13 -15 50 -0.0026 55.2 1500 27.17 26 14 -20 50 -0.0026 55.85 1500 26.86 26 15 -25 50 -0.0026 56.5 1500 26.55 26 16 -30 50 -0.0026 57.15 1500 26.25 26

[0082] Therefore, the number of photovoltaic string series is determined by the lowest temperature under the working condition of the photovoltaic string, the lower the lowest daytime temperature of the photovoltaic field 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 string series number adjustment control system. The photovoltaic string is in standby state when the lowest temperature appears all day, so the lowest temperature under the working condition of the photovoltaic string is higher than the lowest temperature all day.

[0083] The extreme low temperature weather accounts for a small proportion in a year, and the day and night temperature difference is large in the area rich in sunlight resources. At the same time, due to seasonal change, the sunrise and sunset time also changes constantly, so that the time of the lowest temperature in a day also changes constantly with the season. 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 string series number adjustment control system.

[0084] 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 not many schemes to adjust the number of photovoltaic string series, and in the prior art, in order to increase the number of photovoltaic string series, 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 leads to that the inverter cannot work in the rated state for a long time, and the ideal efficiency cannot be achieved. Therefore, how to flexibly and accurately adjust the number of photovoltaic string series becomes a problem to be solved.

[0085] In view of the above defects, the present application provides a photovoltaic string series number adjustment control device, a temperature monitoring unit monitors the environmental temperature under the working condition of the photovoltaic string, obtains a temperature signal, and a DC voltage acquisition unit acquires an output voltage signal of the photovoltaic string; a difference subtraction unit subtracts the output voltage signal from a preset voltage signal output by the control system to obtain a first type of difference subtraction result, or subtracts the output voltage signal from a minimum output voltage signal at the same time to obtain a second type of difference subtraction result, and superimposes the first type of difference subtraction result and the second type of difference subtraction result to obtain a superimposed signal; a control unit generates a first control signal according to the first type of difference subtraction result, or generates a second control signal according to the superimposed signal, and controls the corresponding switching unit to be turned on or turned off based on the first control signal or the second control signal; in the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at at least one place, each switching unit is connected in parallel with at least one photovoltaic component, and when each switching unit is in the on state, the photovoltaic component connected in parallel with the switching unit is short-circuited, so as to reduce the number of photovoltaic string series.

[0086] The application is characterized in that the switch unit is arranged at least at one position in the photovoltaic string, and the switch unit is used to automatically and flexibly and accurately adjust the series number of the photovoltaic string under different ambient temperatures, and is not limited by the minimum temperature under the working condition of the photovoltaic string, and has strong usability and practicality.

[0087] The overall structure of the photovoltaic string series number adjustment and control device provided by the application is described below through specific examples.

[0088] Please refer to Figure 1 , Figure 1 is a schematic block diagram of the photovoltaic string series number adjustment and control device 100 provided by the application. As Figure 1 shown, the photovoltaic string series number adjustment and control device 100 comprises a difference subtraction and superposition unit 150, a control unit 110, a temperature monitoring unit 120, a direct-current voltage acquisition unit 130, a first switch unit 142 and a second switch unit 144.

[0089] The first output end of the temperature monitoring unit 120 is connected with the first input end of the control unit 110, and the second output end of the temperature monitoring unit 120 is connected with the first input end of the difference subtraction and superposition unit 150. The temperature monitoring unit 120 is used to obtain an ambient temperature signal T by monitoring the ambient temperature (i.e. the ambient temperature of the photovoltaic field area) under the working condition of the photovoltaic string 210 in real time, and output the ambient temperature signal T to the control unit 110.

[0090] The input end of the direct-current voltage acquisition unit 130 is connected with the direct-current output end (including the positive and negative terminals BUS+, BUS-) of the photovoltaic string 210, the first output end of the direct-current voltage acquisition unit 130 is connected with the second input end of the difference subtraction and superposition unit 150, and the second output end of the direct-current voltage acquisition unit 130 is connected with the third input end of the difference subtraction and superposition unit 150. The direct-current voltage acquisition unit 130 is used to acquire the output voltage signal Vdc of the photovoltaic string 210, and provide the output voltage signal Vdc to the control unit 110.

[0091] The fourth input end of the difference subtraction and superposition unit 150 is connected with the output end of the control system 230 in the photovoltaic string series number adjustment and control system 200, and the output end of the difference subtraction and superposition unit 150 is connected with the second input end of the control unit 110. The difference subtraction and superposition unit 150 is used to subtract the output voltage signal from the preset voltage signal output by the control system 230 to obtain a first type of difference result, or subtract the output voltage signal from the minimum output voltage signal to obtain a second type of difference result at the same time, superimpose the first type of difference result and the second type of difference result to obtain a superimposed signal.

[0092] The preset voltage is the maximum direct-current input voltage Vdcmax allowed by the inverter.

[0093] The output end of the control unit 110 is connected with the control end of the switch unit, the control unit 110 is used for generating a first control signal according to the first difference result, or generating a second control signal according to the superposition signal, and controlling the corresponding switch unit to be turned on or turned off based on the first control signal or the second control signal.

[0094] In some embodiments, the control unit 110 includes at least one output end. In the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switch unit is arranged. Each switch unit is connected in parallel with at least one photovoltaic component, and the control end of each switch unit is connected with the corresponding output end of the control unit 110. When each switch unit is in the on state, the photovoltaic component connected in parallel with it is short-circuited, so as to reduce the number of series of the photovoltaic string. Among them, the photovoltaic components connected in parallel with each switch unit are the corresponding group number adjustment photovoltaic components.

[0095] It should be noted that from Table 1, the maximum number of series of the photovoltaic string is 30, and the minimum number of series is 26. Therefore, N can be set to 30, and there can be 4 photovoltaic components to be adjusted. The number of N and the number of photovoltaic components to be adjusted can be determined according to the specific situation in the actual application scene, which is not limited here, but only N is 30 and 4 photovoltaic components to be adjusted are introduced to the scheme of the present application.

[0096] In one embodiment, in the photovoltaic string composed of 30 photovoltaic components in positive and negative series, a first switch unit 142 can be arranged at photovoltaic components A1 and A2, and the first switch unit 142 is connected in parallel with the photovoltaic components A1 and A2; a second switch unit 144 can also be arranged at photovoltaic components B1 and B2, and the switch unit 144 is connected in parallel with the photovoltaic components B1 and B2, and the control ends of the first switch unit 142 and the second switch unit 144 are respectively connected with the output end of the control unit 110.

[0097] When the first switch unit 142 and the second switch unit 144 are in the on state, the photovoltaic components A1, A2, B1 and B2 are short-circuited, so as to reduce the number of series 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 reduced, so that the number of series of the photovoltaic string 210 is reduced. Among them, the photovoltaic components A1, A2, B1 and B2 are the group number adjustment photovoltaic components 214.

[0098] 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 the first control signal UK1 or UK2 according to the first difference result, or generate the second control signal UK1 or UK2 according to the superposition signal, and control the corresponding switch unit to be turned on or turned off based on the first control signal or the second control signal.

[0099] In another embodiment, in a photovoltaic string composed of 30 photovoltaic components in positive and negative series, one switch unit is 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.

[0100] In another embodiment, in a photovoltaic string composed of 30 photovoltaic components in positive and negative series, one switch unit is 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.

[0101] The scheme of the embodiment can automatically and flexibly adjust the number of series connection of the photovoltaic string 210 at different ambient temperatures by using the switch unit, 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 number of series connection can be ensured, the number of inverters and photovoltaic supports is reduced, and the area occupied by the photovoltaic field is also reduced, so that the investment of the photovoltaic project is reduced. In addition, the power generation of the series connection number adjustment control system of the photovoltaic component is increased, the economic performance of the photovoltaic project is improved, and the scheme has strong usability and practicality.

[0102] Please continue to refer to Figure 1 According to one embodiment of the present application, the series number adjustment photovoltaic component 214 includes adjacent first to be adjusted photovoltaic component A1, second to be adjusted photovoltaic component A2, third to be adjusted photovoltaic component B1 and fourth to be adjusted photovoltaic component B2.

[0103] The series number adjustment 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 switch unit is in the off state, the to-be-adjusted photovoltaic component is connected to the first part of the photovoltaic string 210.

[0104] It should be noted that, Figure 1The setting mode of the switch unit is only one of many, and there can be many setting modes. The to-be-adjusted photovoltaic modules can also be multiple, adjacent or not adjacent, which will not be listed here, and can be determined according to the specific situation in the actual application scene.

[0105] In one embodiment, when the first switch unit 142 and the second switch unit 144 are in the off state, the to-be-adjusted photovoltaic module 214 in the group string number is connected to the first part 212 of the photovoltaic group string 210 to increase the reduced series number of the photovoltaic group string 210, which can also be understood as reducing the reduced series number of the photovoltaic group string 210. For example, the series number of the original photovoltaic group string 210 is reduced by 4, and the series number of the photovoltaic group string 210 is reduced by 2 now, so the reduced series number of the photovoltaic group string 210 is reduced by 4. However, the series number N of the overall photovoltaic group string 210 does not increase, but in some cases, the to-be-adjusted photovoltaic module connected to the first part 212 of the photovoltaic group string 210 needs to be increased, such as the original to-be-adjusted photovoltaic module connected to the first part 212 of the photovoltaic group string 210 is 2, and now 2 to-be-adjusted photovoltaic modules connected to the first part 212 of the photovoltaic group string 210 need to be added.

[0106] In another embodiment, the multiple to-be-adjusted photovoltaic modules can also be not adjacent, and can be separated in the photovoltaic group string 210. For example, a switch unit is arranged at the first column of photovoltaic modules in the photovoltaic group string 210, a switch unit is arranged at the middle column of photovoltaic modules, and a switch unit is arranged at the last column of photovoltaic modules. The three columns of photovoltaic modules are group string number adjustment photovoltaic modules and are not adjacent.

[0107] In this embodiment, the multiple to-be-adjusted photovoltaic modules are adjacent, and only one switch unit can be arranged, and only one switch unit can be used to adjust the series number of the photovoltaic group string 210, thereby reducing the number of switch units and simplifying the circuit structure.

[0108] The specific structure of the photovoltaic group string series number adjustment control device 100 provided in the embodiments of the present application will be introduced below through specific embodiments.

[0109] Please refer to Figure 2 , Figure 2 is a specific structure schematic diagram of a photovoltaic group string series number adjustment control device 100 of a photovoltaic group string 210 provided in the embodiments of the present application. As Figure 2 shown, in one embodiment, the difference superposition unit 150 includes a first difference module 152, a lowest voltage calculation module 154, a second difference module 156, and a result superposition module 158.

[0110] The first input end of the first difference module 152 is connected with the first output end of the direct current voltage acquisition unit 130, the second input end of the first difference module 152 is connected with the output end of the control system 230, and the output end of the first difference module 152 is connected with the first input end of the result superposition module 158. The first difference module 152 is used for subtracting the output voltage signal Vdc from the preset voltage signal Vdcmax to obtain a first difference result.

[0111] The first input end of the lowest voltage calculation module 154 is connected with the second output end of the temperature monitoring unit 120, the second input end of the lowest voltage calculation module 154 is connected with the output end of the control system 230, and the output end of the lowest voltage calculation module 154 is connected with the first input end of the second difference module 156. The lowest voltage calculation module 154 is used for calculating a lowest output voltage according to the temperature signal T, the preset voltage signal Vdcmax and the component equivalent open circuit voltage Voc', to obtain a lowest output voltage signal Vdc'.

[0112] The second input end of the second difference module 156 is connected with the second output end of the direct current voltage acquisition unit 130, and the output end of the second difference module 156 is connected with the second input end of the result superposition module 158. The second difference module 156 is used for subtracting the output voltage signal Vdc from the lowest output voltage signal Vdc' to obtain a second difference result.

[0113] The output end of the result superposition module 158 is connected with the second input end of the control unit 110, and the result superposition module 158 is used for superimposing the first difference result and the second difference result to obtain a superimposed signal.

[0114] Please refer to Figure 3 , Figure 3 is a specific structure schematic block diagram of a photovoltaic string series number adjustment control device 100 of a photovoltaic string 210 provided by the embodiment of the application. As Figure 3 shown, in one embodiment, the first difference module 152 obtains a first difference result by Vdc-Vdcmax. The lowest voltage calculation module 154 obtains a lowest output voltage signal Vdc' = Vdcmax-2Voc', and Voc' is a component equivalent open circuit voltage, ], represents a component open circuit voltage temperature coefficient.

[0115] The second difference module 156 obtains a second difference result by Vdc-Vdc', and the result superposition module 158 superimposes the first difference result and the second difference result to obtain a superimposed signal.

[0116] Please continue to refer to Figure 2According to an embodiment of the present application, the control unit 110 comprises a main control module 112, a limiting module 116, a signal superposition module 118 and a PWM (Pulse Width Modulation) control module 114.

[0117] The input end of the main control module 112 is connected with the output end of the difference superposition unit 150, and the output end of the main control module 112 is connected with the first input end of the signal superposition module 118. The main control module 112 is used for generating a first type of main control signal based on a first type of difference result, or generating a second type of main control signal based on a superposition signal.

[0118] The input end of the limiting module 116 is connected with the first input end of the temperature monitoring unit 120, and the output end of the limiting module 116 is connected with the second input end of the signal superposition module 118. The limiting module 116 is used for generating a first limiting signal 0 or a second limiting signal 1 based on a temperature signal T.

[0119] The output end of the signal superposition module 118 is connected with the input end of the PWM control module 114, and the output end of the PWM control module 114 is connected with the control end of each switch unit. The signal superposition module 118 is used for performing logical operation superposition on the temperature signal and the first type of main control signal to generate a first type of modulation signal according to the second limiting signal 1, or performing logical operation superposition on the temperature signal and the second type of main control signal to generate a second type of modulation signal.

[0120] The PWM control module 114 is used for generating a first type of driving signal based on the first type of modulation signal, or generating a second type of driving signal based on the second type of modulation signal, and controlling each switch unit to be turned on or turned off based on the first type of driving signal or the second type of driving signal.

[0121] Please continue to refer to Figure 3 The main control module 112 is a PI (proportional integral) controller. The limiting module 116 outputs a limiting signal 0 or 1 by judging whether the temperature is greater than 25℃. When the temperature is greater than 25℃, the limiting module 116 outputs the limiting signal 0; when the temperature is less than or equal to 25℃, the limiting module 116 outputs the limiting signal 1. The PWM control module 114 is a PWM generator.

[0122] Please continue to refer to Figure 1According to an embodiment of the present application, the 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 to the first output end of the control unit 110, the first controlled end of the first switch unit 142 is connected to the negative pole of the first photovoltaic module A1 to be regulated, and the second controlled end of the first switch unit 142 is connected to the positive pole of the second photovoltaic module A2 to be regulated.

[0123] In some embodiments, the first switch unit 142 is configured to short-circuit the first photovoltaic module A1 to be regulated and the second photovoltaic module A2 to be regulated when in the on state, or to connect the first photovoltaic module A1 to be regulated and the second photovoltaic module A2 to be regulated, and to connect the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated when in the off state.

[0124] In some embodiments, the second switch unit 144 is configured to short-circuit the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated when in the on state, or to connect the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated to the first part of the photovoltaic string 210 when in the off state.

[0125] In some embodiments, the second switch unit 144 is configured to short-circuit the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated when in the on state, or to connect the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated to the first part of the photovoltaic string 210 when in the off state.

[0126] In some embodiments, the second switch unit 144 is configured to short-circuit the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated when in the on state, or to connect the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated to the first part of the photovoltaic string 210 when in the off state.

[0127] Please continue to see Figure 2 According to an embodiment of the present application, 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.

[0128] In some embodiments, the first switch device VD1 is configured to short-circuit the first photovoltaic module A1 to be regulated and the second photovoltaic module A2 to be regulated when in the on state, or to connect the first photovoltaic module A1 to be regulated and the second photovoltaic module A2 to be regulated, and to connect the third photovoltaic module B1 to be regulated and the fourth photovoltaic module B2 to be regulated when in the off state.

[0129] The first diode D1 is configured to prevent reverse current flow, i.e. from the positive pole of the second photovoltaic module A2 to be regulated to the negative pole of the first photovoltaic module A1 to be regulated.

[0130] 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 B1 to be regulated, the second controlled end of the second switching device VD2 is connected with the anode of the second diode D2, and the cathode of the second diode D2 is connected with the positive pole of the fourth photovoltaic module to be regulated.

[0131] The second diode D2 is used to prevent the current from flowing in reverse, i.e., from the positive pole of the fourth photovoltaic module B2 to be regulated to the negative pole of the third photovoltaic module B1 to be regulated.

[0132] It should be noted that due to the effect of the second diode D2, the current cannot flow in reverse, and the first photovoltaic module A1 to be regulated, the second photovoltaic module A2 to be regulated, the third photovoltaic module B1 to be regulated, and the fourth photovoltaic module B2 to be regulated cannot form a loop, so they are disconnected from the first part 212 of the photovoltaic string 210, and the number of series connection of the photovoltaic string 210 is reduced.

[0133] In the embodiment, the first switching device VD1 and the second switching device VD2 can be IGBTs. IGBTs have small volume, are controllable, can be turned on and off, have high withstand voltage, have high integration of driving circuit, and are easy to control, so they are preferred switching devices. 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.

[0134] Please continue to refer to Figure 2 According to one embodiment of the present application, the device 100 further comprises a signal input unit 160. The input end of the signal input unit 160 is connected with the output end of the control system 230, and the output end of the signal input unit 160 is connected with the fourth input end of the difference superposition unit 150. The signal input unit 160 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 difference superposition unit 150.

[0135] Please refer to Figure 4 , Figure 4 is a schematic block diagram of the overall structure of the photovoltaic string series connection number regulation and control device 100 of the plurality of photovoltaic strings 210 provided by the embodiment of the present application. As Figure 3 shown, the device 100 comprises a difference superposition unit 150, a control unit 110, a temperature monitoring unit 120, a direct-current voltage acquisition unit 130, and a plurality of switching units 141-14n.

[0136] The DC voltage acquisition unit 130 includes a plurality of input terminals and a plurality of first output terminals and second output terminals, the difference superposition unit 150 includes a plurality of second input terminals and third input terminals, and the control unit 110 includes a plurality of output terminals. The photovoltaic strings 210 connected to the input terminals of the DC voltage acquisition unit 130 are a plurality of photovoltaic strings 211-21n.

[0137] In one embodiment, the output terminal of the temperature monitoring unit 120 is connected to the first input terminal of the control unit 110, and the temperature monitoring unit 120 is configured to monitor the ambient temperature of each photovoltaic string 211-21n under working conditions to obtain a plurality of ambient temperature signals T1-Tn.

[0138] In one embodiment, the DC output terminal [including positive and negative terminal (BUS1+, BUS1-) to (BUSn+, BUSn-)] of each photovoltaic string 211-21n corresponding to each input terminal of the DC voltage acquisition unit 130 is connected, each first output terminal of the DC voltage acquisition unit 130 is connected to each second input terminal of the difference superposition unit 150, and each second output terminal of the DC voltage acquisition unit 130 is connected to each third input terminal of the difference superposition unit 150. The DC voltage acquisition unit 130 is configured to acquire the output voltage signals VdcS1-VdcSn of each photovoltaic string 211-21n.

[0139] In one embodiment, the fourth input terminal and the fifth input terminal of the difference superposition unit 150 are connected to the output terminal of the external control system, and the output terminal of the difference superposition unit 150 is connected to the second input terminal of the control unit 110. The difference superposition unit 150 is configured to perform difference operation on the output voltage signals VdcS1-VdcSn of each photovoltaic string 211-21n and the preset voltage signal Vdcmax to obtain a plurality of first difference results.

[0140] In another embodiment, the difference superposition unit 150 is further configured to perform difference operation on each output voltage signal and the lowest output voltage signal to obtain a plurality of second difference results at the same time as obtaining the first difference results, and to superimpose each first difference result and each second difference result to obtain a plurality of superimposed signals.

[0141] In some embodiments, the output terminal of the control unit 110 is connected to the control terminal of each switching unit 141-14n. The control unit 110 is configured to generate a corresponding first control signal according to each first difference result, or to generate a corresponding second control signal according to each superimposed signal, and to control the corresponding switching unit to be turned on or turned off according to the first control signal and the second control signal.

[0142] In some embodiments, in each photovoltaic module string 211~21n composed of N photovoltaic modules in positive and negative series, at least one switching unit is arranged. Each switching unit is connected in parallel with at least one photovoltaic module, and the control end of each switching unit is connected with the corresponding output end of the control unit 110. When each switching unit is in the on state, the photovoltaic module connected in parallel with the switching unit is short-circuited, so as to reduce the number of series connection of the corresponding photovoltaic module string 211~21n. The photovoltaic module connected in parallel with each switching unit is the number-of-strings-adjustable photovoltaic module.

[0143] In one embodiment, in the photovoltaic module string 211~21n composed of N photovoltaic modules in positive and negative series, the switching unit 141~14n is arranged. Each switching unit 141, 142~14(n-1), 14n is connected in parallel with the corresponding photovoltaic module (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 with the corresponding output end of the control unit 110.

[0144] When each switching unit 141, 142~14(n-1), 14n is in the on state, the corresponding photovoltaic module (A1, A2, B1 and B2)~(A1n, A2n, B1n and B2n) is short-circuited, so as to reduce the number of series connection of the corresponding photovoltaic module string 211~21n. The photovoltaic module (A1, A2, B1 and B2)~(A1n, A2n, B1n and B2n) is the number-of-strings-adjustable photovoltaic module 21111~2111n.

[0145] It should be noted that the specific structure of the photovoltaic module string series number adjustment and control device 100 of the plurality of photovoltaic module strings 211~21n is substantially the same as that of the photovoltaic module string series number adjustment and control device 100 of one photovoltaic module string 210, which will not be described here.

[0146] Please refer to Figure 5 , Figure 5 is a schematic block diagram of the photovoltaic module string series number adjustment and control system 200 including one photovoltaic module string 210 provided by the embodiments of the present application. As Figure 5 shown, the system 200 includes: the photovoltaic module string 210, the inverter 220, the box transformer AC device 240, the control system 230, and the photovoltaic module string series number adjustment and control device 100.

[0147] In an embodiment, the DC input end (including positive and negative terminals VIN+, VIN-) of the photovoltaic string 210 is connected with the output end of the series number adjusting device 100, and the DC output end (including positive and negative terminals BUS+, BUS-) of the photovoltaic string 210 is connected with the power supply input end (including positive and negative terminals N+, N-) of the inverter 220 and the first input end of the series number adjusting device 100.

[0148] The photovoltaic string 210 is configured to provide an output voltage signal Vdc to the series number adjusting device 100 of the photovoltaic string 210, and output the DC power after adjusting the series number of the photovoltaic string 210 to the inverter 220.

[0149] In an embodiment, the output end of the inverter 220 is connected with the input end of the box transformer AC device 240, and the inverter 220 is configured to invert the DC power output by the photovoltaic string 210 into AC power and output the AC power to the box transformer AC device 240. The inverter can be a DC-AC converter.

[0150] It should be noted that the product model of the inverter 220 is different, the number of MPPTs is different, and the number of photovoltaic strings connectable by the inverter 220 is also different.

[0151] In an embodiment, the input end of the box transformer AC device 240 is connected with the output end of the inverter 220, and 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 configured to collect and boost the AC power output by the inverter 220 and output the boosted AC power to the power grid.

[0152] In an embodiment, the output end of the control system 230 is connected with the second input end of the series number adjusting device 100 of the photovoltaic string 210, and the control system 230 is configured to output a preset voltage signal Vdcmax to the series number adjusting device 100 of the photovoltaic string 210. The series number adjusting control device 100 of the photovoltaic string is configured to adjust the series number of the photovoltaic string 210 based on the ambient temperature signal T under the working condition of the photovoltaic string 210, the output voltage signal Vdc provided by the photovoltaic string 210, and the preset voltage signal Vdcmax.

[0153] Please refer to Figure 6 , Figure 6 is a schematic block diagram of the series number adjusting control system 200 of the photovoltaic string including a plurality of photovoltaic strings 211-21n provided by the embodiment of the present application. As Figure 6As shown, the photovoltaic string series number adjustment control system 200 comprises: a plurality of photovoltaic strings 211~21n, an inverter 220, a control system 230, a box transformer AC device 240, and a photovoltaic string series number adjustment control device 100 of the plurality of photovoltaic strings 211~21n.

[0154] The photovoltaic string series number adjustment control device 100 comprises: a plurality of first input terminals, a second input terminal, and a plurality of output terminals, and the inverter 220 comprises a plurality of power input terminals [including positive and negative terminal (N1+, N1-)~(Nn+, Nn-)].

[0155] In an embodiment, the DC input terminals [including positive and negative terminal (VIN1+, VIN1-)~(VINn+, VINn-)] of each photovoltaic string 211~21n are connected to the corresponding output terminals of the photovoltaic string series number adjustment control device 100, and the DC output terminals [including positive and negative terminal (BUS1+, BUS1-)~(BUSn+, BUSn-)] of each photovoltaic string 211~21n are connected to the corresponding power input terminals of the inverter 220 and the corresponding first input terminals of the photovoltaic string series number adjustment control device 100.

[0156] Each photovoltaic string 211~21n is configured to provide a corresponding output voltage signal VdcS1~VdcSn to the photovoltaic string series number adjustment control device 100 and output a corresponding DC power after adjusting the series number of the photovoltaic string 211~21n to the inverter 220.

[0157] In an embodiment, the output terminals of the inverter 220 are connected to the input terminals of the box transformer AC device 240, and the inverter 220 is configured to invert the DC power output by each photovoltaic string 211~21n into AC power and output the AC power to the box transformer AC device 240. The output terminals of the box transformer AC device 240 are connected to the input terminals of the power grid, and the box transformer AC device 240 is configured to collect and boost the AC power output by the inverter 220 and output the boosted AC power to the power grid.

[0158] In an embodiment, the output terminals of the control system 230 are connected to the second input terminals of the photovoltaic string series number adjustment control device 100, and the control system 230 is configured to output a preset voltage signal Vdcmax to the photovoltaic string series number adjustment control device 100. The photovoltaic string series number adjustment control device 100 is configured to adjust the series number of each photovoltaic string 211~21n based on the ambient temperature signals T1~Tn under the working conditions of each photovoltaic string 211~21n, the output voltage signals VdcS1~VdcSn provided by each photovoltaic string 211~21n, and the preset voltage signal Vdcmax.

[0159] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0160] 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 refer to the relevant description of other embodiments.

[0161] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; 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 still 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 number adjustment control device, characterized by, The device comprises a difference superposition unit, a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a switching unit; The first output end of the temperature monitoring unit is connected with the first input end of the control unit, the second output end of the temperature monitoring unit is connected with the first input end of the difference superposition unit, and the temperature monitoring unit is used for monitoring the ambient temperature under the working condition of the photovoltaic string to obtain a 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 first output end of the direct current voltage acquisition unit is connected with the second input end of the difference superposition unit, the second output end of the direct current voltage acquisition unit is connected with the third input end of the difference superposition unit, and the direct current voltage acquisition unit is used for acquiring the output voltage signal of the photovoltaic string; The fourth input end of the difference superposition unit is connected with the output end of the control system in the series quantity adjustment control system of the photovoltaic string, the output end of the difference superposition unit is connected with the second input end of the control unit, the difference superposition unit is used for subtracting the output voltage signal from the preset voltage signal output by the control system to obtain a first difference result, or subtracting the output voltage signal from the lowest output voltage signal to obtain a second difference result at the same time when the first difference result is obtained, superimposing the first difference result and the second difference result to obtain a superimposed signal; The output end of the control unit is connected with the control end of the switching unit, the control unit is used for generating a first control signal according to the first difference result or generating a second control signal according to the superimposed signal, and controlling the corresponding switching unit to be turned on or turned off based on the first control signal and the second control signal; In the photovoltaic string composed of N photovoltaic components in positive and negative series, at least one switching unit is arranged at at least one place, each switching unit is connected in parallel with at least one photovoltaic component, and when each switching unit is in the on state, the photovoltaic component connected in parallel with the switching unit is short-circuited to reduce the series quantity of the photovoltaic string; The photovoltaic component connected in parallel with each switching unit is a string quantity adjustment photovoltaic component.

2. The photovoltaic string series number adjustment control device according to claim 1, characterized by, The string quantity adjustment photovoltaic component comprises adjacent first, second, third and fourth to-be-adjusted photovoltaic components; The string quantity adjustment photovoltaic component is a second part of the photovoltaic string, the remaining photovoltaic components are a first part of the photovoltaic string, and when the switching unit is in the off state, the to-be-adjusted photovoltaic component is connected with the first part of the photovoltaic string.

3. The photovoltaic string string number regulation control device according to claim 1, wherein, The difference superposition unit comprises a first difference module, a lowest voltage calculation module, a second difference module and a result superposition module. The first input end of the first difference module is connected with the first output end of the direct current voltage acquisition unit, the second input end of the first difference module is connected with the output end of the control system, the output end of the first difference module is connected with the first input end of the result superposition module, and the first difference module is used for subtracting the output voltage signal from the preset voltage signal to obtain the first type of difference result; The first input end of the lowest voltage calculation module is connected with the second output end of the temperature monitoring unit, the second input end of the lowest voltage calculation module is connected with the output end of the control system, the output end of the lowest voltage calculation module is connected with the first input end of the second difference module, and the lowest voltage calculation module is used for calculating the lowest output voltage according to the temperature signal, the preset voltage signal and the equivalent open circuit voltage of the component to obtain the lowest output voltage signal; The second input end of the second difference module is connected with the second output end of the direct current voltage acquisition unit, and the output end of the second difference module is connected with the second input end of the result superposition module. The second difference module is used for subtracting the output voltage signal from the lowest output voltage signal to obtain the second type of difference result. The output end of the result superposition module is connected with the second input end of the control unit, and the result superposition module is used for superimposing the first type of difference result and the second type of difference result to obtain the superimposed signal.

4. The photovoltaic string string count regulation control device of claim 1, wherein, The control unit comprises a main control module, a limiting module, a signal superposition module and a PWM control module. The input end of the main control module is connected with the output end of the difference superposition unit, the output end of the main control module is connected with the first input end of the signal superposition module, and the main control module is used for generating a first type of main control signal based on the first type of difference result or generating a second type of main control signal based on the superimposed signal. The input end of the limiting module is connected with the first input end of the temperature monitoring unit, the output end of the limiting module is connected with the second input end of the signal superposition module, and the limiting module is used for generating a first limiting signal or a second limiting signal based on the temperature signal. The output end of the signal superposition module is connected with the input end of the PWM control module, the output end of the PWM control module is connected with the control end of each switch unit, the signal superposition module is used for performing logical operation superposition on the temperature signal and the first type of main control signal to generate a first type of modulation signal according to the second limiting signal, or performing logical operation superposition on the temperature signal and the second type of main control signal to generate a second type of modulation signal. The PWM control module is used for generating a first type of driving signal based on the first type of modulation signal or generating a second type of driving signal based on the second type of modulation signal, and controlling each switch unit to be turned on or turned off based on the first type of driving signal or the second type of driving signal.

5. The photovoltaic string string number regulation control device according to claim 2, wherein, The device comprises a first switch unit and a second switch unit. The control end of the first switch unit is connected with the first output end of the control unit, the first controlled end of the first switch unit is connected with the negative electrode of the first photovoltaic module to be regulated, the second controlled end of the first switch unit is connected with the positive electrode of the second photovoltaic module to be regulated, and the first switch unit is used for short-circuiting the first photovoltaic module to be regulated and the second photovoltaic module to be regulated when being in the on state, or connecting the first photovoltaic module to be regulated and the second photovoltaic module to be regulated and connecting the third photovoltaic module to be regulated and the fourth photovoltaic module to be regulated when being in the off state; The control end of the second switch unit is connected with the second output end of the control unit, the first controlled end of the second switch unit is connected with the negative electrode of the third photovoltaic module to be regulated, and the second controlled end of the second switch unit is connected with the positive electrode of the fourth photovoltaic module to be regulated, and the second switch unit is used for short-circuiting the third photovoltaic module to be regulated and the fourth photovoltaic module to be regulated when being in the on state, or connecting the third photovoltaic module to be regulated and the fourth photovoltaic module to be regulated to the first part of the photovoltaic string when being in the off state; Wherein, when the third photovoltaic module to be regulated and the fourth photovoltaic module to be regulated are short-circuited, the first photovoltaic module to be regulated and the second photovoltaic module to be regulated are disconnected from the first part of the photovoltaic string at the same time.

6. The photovoltaic string string count regulation control device of claim 5, wherein, 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; The control end of the first switch device is connected with the first output end of the control unit, the first controlled end of the first switch device is connected with the negative electrode of the first photovoltaic module to be regulated, the second controlled end of the first switch device is connected with the anode of the first diode, the cathode of the first diode is connected with the positive electrode of the second photovoltaic module to be regulated, and the first diode is used for preventing current from flowing from the positive electrode of the second photovoltaic module to be regulated into the negative electrode of the first photovoltaic module to be regulated; The control end of the second switch device is connected with the second output end of the control unit, the first controlled end of the second switch device is connected with the negative electrode of the third photovoltaic module to be regulated, the second controlled end of the second switch device is connected with the anode of the second diode, the cathode of the second diode is connected with the positive electrode of the fourth photovoltaic module to be regulated, and the second diode is used for preventing current from flowing from the positive electrode of the fourth photovoltaic module to be regulated into the negative electrode of the third photovoltaic module to be regulated.

7. The photovoltaic string string count regulation control device of claim 1, wherein, The device further comprises a signal input unit; The input end of the signal input unit is connected with the output end of the control system, the output end of the signal input unit is connected with the fourth input end of the difference superposition unit, and the signal input unit is used for inputting a preset voltage signal output by the control system and outputting the preset voltage signal to the difference superposition unit.

8. The photovoltaic string string number regulation control device according to any one of claims 1-7, characterized in that, The device comprises a difference superposition unit, a control unit, a temperature monitoring unit, a direct current voltage acquisition unit and a plurality of switch units; wherein the direct current voltage acquisition unit comprises a plurality of input ends and a plurality of first output ends and second output ends, the difference superposition unit comprises a plurality of second input ends and third input ends, the control unit comprises a plurality of output ends, and a plurality of photovoltaic module strings are connected to the input ends of the direct current voltage acquisition unit; The first output end of the temperature monitoring unit is connected to the first input end of the control unit, the second output end of the temperature monitoring unit is connected to the first input end of the difference superposition unit, and the temperature monitoring unit is used for monitoring the ambient temperature under the working condition of each photovoltaic module string to obtain a plurality of temperature signals; Each input end of the direct current voltage acquisition unit is connected to the direct current output end of the corresponding photovoltaic module string, each first output end of the direct current voltage acquisition unit is connected to each second input end of the difference superposition unit, each second output end of the direct current voltage acquisition unit is connected to each third input end of the difference superposition unit, and the direct current voltage acquisition unit is used for acquiring the output voltage signal of each photovoltaic module string; The fourth input end and the fifth input end of the difference superposition unit are connected to the output end of the external control system, the output end of the difference superposition unit is connected to the second input end of the control unit, the difference superposition unit is used for subtracting each output voltage signal of the photovoltaic module string from the preset voltage signal to obtain a plurality of first difference results, or simultaneously subtracting each output voltage signal from the lowest output voltage signal to obtain a plurality of second difference results, superimposing each first difference result and each second difference result to obtain a plurality of superimposed signals; The output end of the control unit is connected to the control end of the switch unit, the control unit is used for generating a corresponding first control signal according to each first difference result, or generating a corresponding second control signal according to each superimposed signal, and controlling the corresponding switch unit to be turned on or turned off according to the first control signal and the second control signal; In each photovoltaic module string composed of N photovoltaic modules in positive and negative series, at least one switch unit is arranged at at least one position, each switch unit is connected in parallel to at least one photovoltaic module, and when each switch unit is in an on state, the photovoltaic module connected in parallel thereto 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 switch unit is a corresponding number of string adjustment photovoltaic module.

9. A photovoltaic string string series quantity adjustment control system, characterized by, The system comprises a photovoltaic module string, an inverter, an AC device of a box transformer, a control system and the photovoltaic module string series number adjustment control device of any one of claims 1-7. The DC input end of the photovoltaic string is connected with the output end of the photovoltaic string series number adjusting control device, the DC output end of the photovoltaic string is connected with the power supply input end of the inverter and the first input end of the photovoltaic string series number adjusting control device, and the photovoltaic string is used for providing an output voltage signal to the photovoltaic string series number adjusting control device and outputting the DC power after adjusting the series number of the photovoltaic string to the inverter; The output end of the inverter is connected with the input end of the box transformer AC device, and the inverter is used for converting the DC power output by the photovoltaic string into AC power and outputting the AC power to the box transformer AC device; The output end of the box transformer AC device is connected with the input end of the power grid, and the box transformer AC device is used for collecting and boosting the AC power output by the inverter and outputting the boosted AC power to the power grid; The output end of the control system is connected with the second input end of the photovoltaic string series number adjusting control device, and the control system is used for outputting a preset voltage signal to the photovoltaic string series number adjusting control device; The photovoltaic string series number adjusting control device is used for adjusting the series number of the photovoltaic string based on the ambient temperature signal under the working condition of the photovoltaic string, the output voltage signal provided by the photovoltaic string and the preset voltage signal.

10. The photovoltaic string string count regulation control system of claim 9, wherein, The system comprises a plurality of photovoltaic strings, an inverter, a box transformer AC device, a control system and the photovoltaic string series number adjusting control device of claim 8, wherein the photovoltaic string series number adjusting control 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; The DC input end of each photovoltaic string is connected with the corresponding output end of the photovoltaic string series number adjusting control device, the DC 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 control device, and each photovoltaic string is used for providing a corresponding output voltage to the photovoltaic string series number adjusting control device and outputting the corresponding DC power after adjusting the series number of the photovoltaic string to the inverter; The output end of the inverter is connected with the input end of the box transformer AC device, and the inverter is used for converting the DC power output by each photovoltaic string into AC power and outputting the AC power to the box transformer AC device; The output end of the box transformer AC device is connected with the input end of the power grid, and the box transformer AC device is used for collecting and boosting the AC power output by the inverter and outputting the boosted AC power to the power grid; The output end of the control system is connected with the second input end of the photovoltaic string series number adjusting control device, and the control system is used for outputting a preset voltage signal to the photovoltaic string series number adjusting control device; The photovoltaic string series number adjusting control device is used for adjusting the series number of each photovoltaic string based on the ambient temperature signal under the working condition of each photovoltaic string, the output voltage signal provided by each photovoltaic string and the preset voltage signal.

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