WO2023010955A1 - 光伏系统及其iv扫描方法、装置和汇流箱 - Google Patents

光伏系统及其iv扫描方法、装置和汇流箱 Download PDF

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Publication number
WO2023010955A1
WO2023010955A1 PCT/CN2022/094853 CN2022094853W WO2023010955A1 WO 2023010955 A1 WO2023010955 A1 WO 2023010955A1 CN 2022094853 W CN2022094853 W CN 2022094853W WO 2023010955 A1 WO2023010955 A1 WO 2023010955A1
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Prior art keywords
photovoltaic
string
voltage
scanning
open
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PCT/CN2022/094853
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English (en)
French (fr)
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钱永恒
范纯浆
丁杰
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阳光电源股份有限公司
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30—Electrical components
    • H02S40/34—Electrical components comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present application relates to the technical field of photovoltaic power generation, in particular to a photovoltaic system and its IV scanning method, device and combiner box.
  • the photovoltaic array is the core component of the photovoltaic system. It works in the outdoor environment for a long time. The performance of the photovoltaic array will be affected by the service life and natural environmental factors. It is important to evaluate the power generation capacity and fault test of the photovoltaic modules to improve the power generation of the photovoltaic system. significance.
  • IV scanning technology refers to the use of inverters or IV scanning equipment to sample the output voltage and output current of the battery panel, and then combine the sampling to obtain data such as illuminance and temperature of the photovoltaic array. Judging whether there are abnormal conditions such as shading, damage, and hot spots in photovoltaic modules, and can also be used to analyze the attenuation of battery modules.
  • the present application provides a photovoltaic system and its IV scanning method, device and combiner box to solve the problem that the existing centralized grid-connected system cannot perform IV scanning on a single string and optimize the scanning characteristic curve.
  • an embodiment of the present invention provides a photovoltaic system IV scanning method
  • the photovoltaic system includes an inverter and a combiner box connected to the DC side of the inverter, and the combiner box is connected to m-way photovoltaic groups string, m is a positive integer greater than 1, and the scanning method includes the following steps:
  • the combiner box obtains the open-circuit voltage of each of the photovoltaic strings, and sends the open-circuit voltage of the photovoltaic strings to a preset controller;
  • the inverter determines an initial scanning voltage according to the open-circuit voltage of the group string, and controls the output voltage value of the group string to gradually change from the initial scanning voltage to a preset voltage lower limit value based on a first preset step size;
  • the combiner box acquires the output current value of the photovoltaic string at each string output voltage value, and sends the string output voltage value and the output current value to the preset controller;
  • the preset controller determines a set of scanning sample points for each of the photovoltaic strings according to the open-circuit voltage of the strings, the output voltage value of the strings, and the output current value.
  • said acquiring the open-circuit voltage of said photovoltaic string comprises the following steps:
  • the inverter boosts and regulates the DC bus voltage, so that current flows from the inverter to the photovoltaic string along a first direction;
  • the inverter step-down regulates the DC bus voltage until the current flows from the photovoltaic module to the inverter along a second direction, the second direction is opposite to the first direction;
  • the combiner box determines the DC bus voltage at the moment when the current direction is reversed as the open-circuit voltage of the group string.
  • the step-down regulation of the DC bus voltage by the inverter includes the following steps:
  • the determining the initial scanning voltage according to the open-circuit voltage of the group string includes the following steps:
  • the open-circuit voltages of the photovoltaic strings correspond to the photovoltaic strings one by one;
  • the open-circuit voltages of m group strings are compared, and the maximum value of the open-circuit voltage of the group strings is determined according to the comparison result, and the scanning initial voltage is greater than or equal to the maximum value of the open-circuit voltage of the group strings.
  • the inverter and/or the combiner box start a DC short-circuit mode
  • the combiner box collects the short-circuit current value flowing through the photovoltaic string in DC short-circuit mode, and sends the short-circuit current value to the preset controller;
  • the preset controller adds the short-circuit current value to the set of scan sample points.
  • the scanning start point of the IV scanning curve of the photovoltaic string is the corresponding open circuit voltage of the string.
  • the preset controller includes a combiner box controller, an inverter controller, or any controller in the photovoltaic system except the combiner box controller and the inverter controller.
  • the embodiment of the present invention also provides a photovoltaic system IV scanning device, including: a combiner box, an inverter and a preset controller, the combiner box is connected to m photovoltaic strings, m is a positive value greater than 1 integer;
  • the combiner box is used to obtain the open-circuit voltage of the photovoltaic strings, and send the open-circuit voltage of the photovoltaic strings to the preset controller;
  • the inverter is configured to determine an initial scanning voltage according to the open-circuit voltage of the group string, and control the output voltage value of the group string to gradually change from the initial scanning voltage to a preset voltage lower limit value based on a first preset step size;
  • the combiner box is also used to obtain the output current value of the photovoltaic string at each output voltage value of the string, and send the output voltage value and the output current value of the string to the preset controller;
  • the preset controller is configured to determine a set of scanning sample points for each of the photovoltaic strings according to the open-circuit voltage of the strings, the output voltage value of the strings, and the output current value.
  • the embodiment of the present invention also provides a combiner box, the input side of the combiner box is connected to m photovoltaic strings, the output side of the combiner box is connected to the DC side of the inverter, and the combiner box Including: combiner box controller, current sampling unit and voltage sampling unit;
  • the voltage sampling unit is used to acquire the open-circuit voltage of the photovoltaic string and the output voltage value of the string in scanning mode;
  • the current sampling unit is used to obtain the output current value of the photovoltaic string
  • the combiner box controller is configured to determine a set of scanning sample points for each of the photovoltaic strings according to the open-circuit voltage of the strings, the output voltage value of the strings, and the output current value.
  • an embodiment of the present invention further provides a photovoltaic system, including the above photovoltaic system IV scanning device.
  • the photovoltaic system and its IV scanning device and combiner box provided by the embodiment of the present invention implement the IV scan method, which obtains the open circuit voltage of each photovoltaic string through the combiner box, and sends the open circuit voltage of the string to the preset control Inverter; the MPPT scanning mode is executed by the inverter, the initial voltage of the scan is determined according to the open circuit voltage of the string, and the output voltage value of the string is controlled to gradually change from the initial voltage of the scan to the lower limit value of the preset voltage based on the first preset step size; the combiner box Obtain the output current value flowing through each photovoltaic string at the output voltage value of each string, and send the output voltage value of the string and the corresponding output current value to the preset controller; , string output voltage value and output current value determine the scan sample point set of each photovoltaic string, solve the problem that the existing centralized grid-connected system cannot perform IV scan on a single string, and detect the open circuit of a single string through the combiner box Voltage, as the
  • Fig. 1 is a flow chart of a photovoltaic system IV scanning method provided by Embodiment 1 of the present invention
  • Fig. 2 is a flowchart of another photovoltaic system IV scanning method provided by Embodiment 1 of the present invention.
  • Fig. 3 is a flow chart of another photovoltaic system IV scanning method provided by Embodiment 1 of the present invention.
  • Fig. 4 is a flow chart of another photovoltaic system IV scanning method provided by Embodiment 1 of the present invention.
  • Fig. 5 is a schematic diagram of an IV scan curve provided by Embodiment 1 of the present invention.
  • Fig. 6 is a schematic structural diagram of a photovoltaic system IV scanning device provided by Embodiment 2 of the present invention.
  • Fig. 7 is a schematic structural view of a combiner box provided in Embodiment 3 of the present invention.
  • Fig. 8 is a schematic structural diagram of a photovoltaic system provided by Embodiment 4 of the present invention.
  • Figure 1 is a flow chart of an IV scanning method for a photovoltaic system provided by Embodiment 1 of the present invention. This embodiment is applicable to the application scenario of a centralized photovoltaic grid-connected power generation system.
  • the IV scanning method can be implemented by a specific IV scanner device or The inverter and the combiner box jointly participate in the realization.
  • the photovoltaic system includes an inverter and n combiner boxes connected to the DC side of the inverter.
  • the combiner boxes are connected to m photovoltaic strings, where m is a positive integer greater than 1.
  • the photovoltaic system IV scanning method specifically includes the following steps:
  • Step S1 The combiner box obtains the open-circuit voltage of each photovoltaic string, and sends the open-circuit voltage of the string to the preset controller.
  • the combiner box can adopt a collection-distributed structure, set up n-channel MPPT controllers, and use each MPPT controller to perform decentralized maximum power point tracking on the DC power generated by m-channel photovoltaic strings, and output it after DC-DC confluence.
  • the open-circuit voltage of a string refers to the maximum open-circuit voltage of a single photovoltaic string, which is different from the maximum open-circuit voltage of a photovoltaic system. It can be used to characterize the power generation capacity of a single photovoltaic module, and it can cooperate with the inverter through the combiner box Function, sampling to obtain the open-circuit voltage of each PV string.
  • Step S2 The inverter determines the initial scanning voltage according to the open-circuit voltage of the group string, and controls the output voltage value of the group string to gradually change from the initial scanning voltage to the lower limit value of the preset voltage based on the first preset step size.
  • the string output voltage value is the working voltage value of the inverter.
  • the inverter works in the IV scan mode, and starts the global MPPT (Maximum Power Point Tracking, maximum power point tracking) scan function, and its working voltage gradually drops from the scan initial voltage to the preset voltage according to the first preset step.
  • a limit value, the preset voltage lower limit value may be an MPP (Maximum Power Point, maximum power point) voltage lower limit value.
  • the first preset step size can be set equal to 1V, that is, during the scanning process, the operating voltage is reduced by 1V every time the voltage regulation interval passes until the output voltage value of the string is less than or equal to the preset voltage lower limit.
  • Step S3 The combiner box obtains the output current value of the photovoltaic string at each output voltage value of the string, and sends the output voltage value and the output current value of the string to the preset controller.
  • the combiner box can be equipped with m-channel current sampling units.
  • the m-channel current sampling units correspond to the m-channel photovoltaic strings. At any string output voltage point, the current sampling unit collects the output of the corresponding photovoltaic string. Therefore, the combiner box can obtain multiple string output voltage values and corresponding output current values of each photovoltaic module through sampling.
  • Step S4 The preset controller determines a set of scanning sample points for each photovoltaic string according to the open circuit voltage of the string, the output voltage value and the output current value of the string.
  • the scan sample point set can be used to draw the IV characteristic curve of a single photovoltaic string, and in the scan sample point set of each photovoltaic string, the maximum value of the string output voltage value can be the string open-circuit voltage.
  • the preset controller may include a combiner box controller, an inverter controller, or any controller in the photovoltaic system except the combiner box controller and the inverter controller.
  • the preset controller can also be connected with the photovoltaic upper computer system, receive the scanning instruction issued by the upper computer system, and send the scanning sample point set or the finally generated IV characteristic curve to the photovoltaic upper computer system for PV modules are monitored online for faults.
  • the inverter After receiving the scan instruction, the inverter starts the global MPPT (Maximum Power Point Tracking, Maximum Power Point Tracking) scan mode, and controls the string output voltage value to gradually decrease from the scan initial voltage according to the first preset step size.
  • the box samples the output current value Ii of each PV string at different string output voltage values Ui, records the corresponding voltage and current points (Ui, Ii), and the inverter judges in real time whether the output voltage value of the string is less than or equal to the preset voltage
  • the lower limit value if the string output voltage value is less than or equal to the preset voltage lower limit value, the inverter ends the global MPPT scanning mode and enters the next working mode.
  • the combiner box sends all the sampled voltage and current points (Ui, Ii) and the open-circuit voltage U0 of each PV string to the preset controller, and the preset controller According to the open-circuit voltage U0 of the strings, the scanning sample point set corresponding to each photovoltaic string is respectively generated to solve the problem that the existing centralized grid-connected system cannot perform IV scanning on a single string, and the open-circuit voltage of a single string is detected through the combiner box.
  • the IV scanning point of a single photovoltaic string optimize the scanning characteristic curve, improve the scanning accuracy, improve the performance prediction accuracy of photovoltaic panels, and help improve the power generation of photovoltaic systems.
  • Fig. 2 is a flow chart of another photovoltaic system IV scanning method provided in Embodiment 1 of the present invention.
  • Fig. 1 exemplarily shows the specific implementation of a method for obtaining the open-circuit voltage of a string method, rather than limiting the above method.
  • obtaining the open-circuit voltage of the photovoltaic string in the above step S1 includes the following steps:
  • Step S101 The inverter boosts and regulates the DC bus voltage, so that the current flows from the inverter to the photovoltaic string along a first direction.
  • the inverter can raise the DC bus voltage to the maximum operating voltage in one step (for example, the maximum operating voltage can be 1500V), and under the action of the maximum operating voltage, the output currents of all photovoltaic strings flow in the first direction .
  • the maximum operating voltage can be 1500V
  • Step S102 The inverter steps down the DC bus voltage until the current flows from the photovoltaic module to the inverter along a second direction, which is opposite to the first direction.
  • the step-down adjustment of the DC bus voltage by the inverter includes: acquiring a second preset step size, wherein the second preset step size includes a preset step-down amplitude; controlling the voltage based on the second preset step size The DC bus voltage is gradually reduced until the current flow direction is reversed.
  • the preset step-down amplitude can be set to be less than 0.1V, and the inverter controls the DC bus voltage to reduce the preset step-down amplitude every preset interval until all the branches where the photovoltaic strings are located A reversal of current flow occurs.
  • Step S103 The combiner box determines the DC bus voltage at the moment when the current flow direction is reversed as the open-circuit voltage of the string.
  • the combiner box can sample the output voltage of the combined photovoltaic modules as the DC bus voltage. Before the inverter enters the IV scan mode, the open circuit voltage detection is performed first, and the inverter first raises the DC bus voltage to the maximum operating voltage.
  • the output current of each photovoltaic string sampled by the combiner box is in the first direction (for example, reverse); the inverter controls the DC bus voltage to gradually decrease with the second preset step size, and at the same time, the The output current of each photovoltaic string, in the process of stepping down the DC bus voltage, if the output current of any photovoltaic string is reversed from the first direction to the second direction (for example, the forward direction), that is, the current turns from reverse to forward direction, the combiner box determines that the DC bus voltage at the moment when the current flow reverses is the string open-circuit voltage of the PV string.
  • the first direction for example, reverse
  • the inverter controls the DC bus voltage to gradually decrease with the second preset step size
  • the open-circuit voltage of each photovoltaic string is independently detected through the reversal of the branch current, and it is used as the IV scanning point of a single photovoltaic string to optimize the scan.
  • the characteristic curve can improve the scanning accuracy, improve the performance prediction accuracy of photovoltaic panels, and help improve the power generation of photovoltaic systems.
  • determining the initial scanning voltage according to the open circuit voltage of the group strings includes the following steps: obtaining m group string open circuit voltages of m photovoltaic group strings, and the group string open circuit voltages correspond to the photovoltaic group strings one by one; The voltages are compared, and the maximum value of the open circuit voltage of the group string is determined according to the comparison result, and the initial scanning voltage is greater than or equal to the maximum value of the open circuit voltage of the group string.
  • the open circuit voltage of each photovoltaic group is first detected to obtain m group string open circuit voltages, and the maximum value of the group string open circuit voltage among the m group string open circuit voltages is obtained by comparison.
  • the initial voltage of the inverter setting scan is greater than or equal to the maximum value of the open-circuit voltage of the string.
  • the operating voltage of the inverter gradually decreases, and the IV scan data of all PV strings at the open-circuit voltage point can be obtained. It is beneficial to realize the full curve segment IV scanning of all photovoltaic modules.
  • the inverter may use the maximum operating voltage as the initial scanning voltage, which is not limited.
  • Fig. 3 is a flow chart of another photovoltaic system IV scanning method provided in Embodiment 1 of the present invention.
  • Fig. 1 exemplarily shows that the output voltage value of the string reaches the preset voltage lower limit After the value, an implementation of sample point scanning is performed.
  • Step S301 The inverter and/or the combiner box start the DC short-circuit mode.
  • Step S302 The combiner box collects the short-circuit current value flowing through the photovoltaic string in the DC short-circuit mode, and sends the short-circuit current value to the preset controller.
  • Step S303 The preset controller adds the short-circuit current value to the set of scanning sample points.
  • the inverter can turn off all switches, or the combiner box short-circuits the combiner output side, so that The system enters the DC short-circuit mode, the combiner box collects the short-circuit current value flowing through each photovoltaic string, and the preset controller records the short-circuit current value and the corresponding short-circuit voltage value (which can be defined as 0), and updates and supplements the scanning sample points .
  • the preset voltage lower limit for example, the MPPT lower limit
  • the inverter can turn off all switches, or the combiner box short-circuits the combiner output side, so that The system enters the DC short-circuit mode, the combiner box collects the short-circuit current value flowing through each photovoltaic string, and the preset controller records the short-circuit current value and the corresponding short-circuit voltage value (which can be defined as 0), and updates and supplements the scanning sample points .
  • FIG. 4 is a flow chart of another photovoltaic system IV scanning method provided in Embodiment 1 of the present invention. Referring to Figure 4, after obtaining the scan sample point set of each photovoltaic string, it also includes:
  • Step S5 Perform data fitting according to the scan sample point set to determine the IV scan curve of the photovoltaic string, wherein the scan start point of the IV scan curve of the photovoltaic string is the corresponding open-circuit voltage of the string.
  • the output voltage and output current of the photovoltaic string cannot be measured through sampling, and the open-circuit voltage point of the string recorded by the preset controller (including the open-circuit voltage point of the string) can be used All the voltage and current data (Ui, Ii) between the MPPT lower limit voltage point (including the MPPT lower limit voltage point) are used as the original data for intelligent fitting, and combined with the preset fitting function, the second stage of each PV string is obtained by fitting.
  • IV scan curve The IV scanning curve of the first stage and the IV scanning curve of the second stage of the same photovoltaic string together constitute the IV scanning curve of the photovoltaic string, which is conducive to realizing the IV scanning of the full voltage range and optimizing the scanning characteristic curve.
  • the short-circuit current value and short-circuit voltage value (which can be defined as 0) obtained from the DC bus short-circuit measurement can be imported into the fitting function to correct the fitting curve , optimize the scanning characteristic curve and improve the scanning accuracy.
  • FIG. 5 is a schematic diagram of an IV scan curve provided in Embodiment 1 of the present invention.
  • the open-circuit voltage point of the string is defined as the first scanning sample point (U0, I0)
  • the preset voltage lower limit point is the second scanning sample point (Up, Ip)
  • the DC short-circuit current point is the third scanning sample point sample point (0, Id)
  • the scanning starting point of the IV scanning curve in the first stage is the first scanning sample point (U0, I0)
  • the scanning end point is the second scanning sample point (Up, Ip)
  • the starting point of the two-stage IV scan curve is the second scan sample point (Up, Ip)
  • the end point is the third scan sample point (0, Id).
  • Embodiment 2 of the present invention provides a photovoltaic system IV scanning device.
  • the photovoltaic system IV scanning device provided in the embodiment of the present invention can execute the photovoltaic system IV scanning method provided in any embodiment of the present invention, and has corresponding functional modules for executing the method. and beneficial effects.
  • Fig. 6 is a schematic structural diagram of an IV scanning device for a photovoltaic system provided by Embodiment 2 of the present invention.
  • the photovoltaic system IV scanning device 00 includes: a combiner box 01, an inverter 02, and a preset controller 03.
  • the combiner box 01 is connected to m-path photovoltaic strings, and the m-path photovoltaic strings PV include the first photovoltaic string PV1, the second The second photovoltaic string PV2, ..., the mth photovoltaic string PVm, m is a positive integer greater than 1;
  • the combiner box 01 is used to obtain the open circuit voltage of the photovoltaic string, and send the open circuit voltage of the photovoltaic string to A preset controller;
  • an inverter 02 configured to determine an initial scanning voltage according to the open-circuit voltage of the group string, and control the output voltage value of the group string to gradually change from the initial scanning voltage to the lower limit value of the preset voltage based on the first preset step size;
  • the combiner box 01 is also used to obtain the output current value of the photovoltaic string at the output voltage value of each string, and send
  • the preset controller can be integrated with the combiner box controller or the inverter controller, or any controller in the photovoltaic system except the combiner box controller and the inverter controller can be used.
  • the inverter 02 is also used for step-up regulation of the DC bus voltage, so that the current flows from the inverter to the photovoltaic string along the first direction, and step-down regulation of the DC bus voltage until the current follows the second direction.
  • the two directions flow from the photovoltaic module to the inverter, and the second direction is opposite to the first direction;
  • the combiner box 01 is also used to determine the DC bus voltage at the moment of current flow reversal as the open circuit voltage of the string.
  • step-down regulating the DC bus voltage includes: obtaining a second preset step size, and controlling the DC bus voltage to gradually decrease based on the second preset step size.
  • the initial scan voltage is determined according to the open-circuit voltage of the group strings, including: obtaining m open-circuit voltages of the photovoltaic group strings of m paths, and the open-circuit voltages of the group strings are in one-to-one correspondence with the photovoltaic group strings; Comparing, determining the maximum value of the open-circuit voltage of the group string according to the comparison result, and the initial scanning voltage is greater than or equal to the maximum value of the open-circuit voltage of the group string.
  • the inverter and/or the combiner box starts the DC short-circuit mode; the combiner box collects the short-circuit current value flowing through the photovoltaic string in the DC short-circuit mode, and The short-circuit current value is sent to the preset controller; the preset controller adds the short-circuit current value to the set of scan sample points.
  • the preset controller is also used to perform data fitting according to the scan sample point set after obtaining the scan sample point set of each photovoltaic string, and determine the IV scan curve of the photovoltaic string, wherein, the PV string The scan start point of the IV scan curve is the corresponding string open circuit voltage.
  • the photovoltaic system IV scanning device implements the IV scanning method, which obtains the open-circuit voltage of each photovoltaic string through the combiner box, and sends the open-circuit voltage of the photovoltaic string to the preset controller;
  • the MPPT scan mode is executed by the inverter, the initial voltage of the scan is determined according to the open-circuit voltage of the string, and the output voltage value of the string is controlled to gradually change from the initial voltage of the scan to the lower limit of the preset voltage based on the first preset step length;
  • the output voltage value of each string obtains the output current value of each photovoltaic string, and sends the output voltage value of the string and the corresponding output current value to the preset controller;
  • the voltage value and output current value determine the scanning sample point set of each photovoltaic string, which solves the problem that the existing centralized grid-connected system cannot perform IV scanning on a single string, and detects the open circuit voltage of a single string through the combiner box as a single The IV scanning
  • Embodiment 3 of the present invention provides a combiner box.
  • An input side of the combiner box is connected to m photovoltaic strings, and an output side of the combiner box is connected to a DC side of an inverter.
  • Fig. 7 is a schematic structural diagram of a combiner box provided by Embodiment 3 of the present invention.
  • the combiner box 01 includes: a combiner box controller 101, a current sampling unit 102, and a voltage sampling unit 103, wherein the voltage sampling unit 103 is used to obtain the open circuit voltage of the photovoltaic string and the scan mode The output voltage value of the group string under; the current sampling unit 102 is used to obtain the output current value of the photovoltaic group string; the combiner box controller 101 is used to determine each The scan sample point set of the PV string.
  • the combiner box can be a collection-distributing combiner box.
  • a multi-channel MPPT controller is set, and the MPPT controller is used to perform decentralized maximum power point tracking on the direct current generated by the m-channel photovoltaic strings. After DC-DC conversion, the current is output to the DC side of the inverter.
  • the combiner box 01 is also used to determine the DC bus voltage at the moment of current flow reversal as the open-circuit voltage of the group string, and the inverter 02 can be used to boost and regulate the DC bus voltage so that the current flows from the inverter to the inverter in the first direction.
  • the inverter flows to the photovoltaic string, and the DC bus voltage is step-down adjusted until the current flows from the photovoltaic module to the inverter along the second direction, which is opposite to the first direction, and the detection of current flow reversal is realized.
  • the combiner box provided by the embodiment of the present invention is equipped with a voltage and current detection function, and detects the open circuit voltage of a single photovoltaic string according to the current reversal, optimizes the scanning characteristic curve, improves the scanning accuracy, and improves the performance prediction accuracy of photovoltaic panels. It is beneficial to increase the power generation of the photovoltaic system.
  • Fig. 8 is a schematic structural diagram of a photovoltaic system provided by Embodiment 4 of the present invention, and the photovoltaic system may be a centralized photovoltaic power generation system.
  • the photovoltaic system 100 includes the aforementioned photovoltaic system IV scanning device 00 .
  • a photovoltaic system IV scanning device is installed, and an IV scanning method is executed.
  • the open-circuit voltage of each photovoltaic string is obtained through the combiner box, and the open-circuit voltage of the string is sent to the preset controller.

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Abstract

本申请公开了一种光伏系统及其IV扫描方法、装置和汇流箱，该扫描方法包括：汇流箱获取光伏组串的组串开路电压，并将组串开路电压发送至预设控制器；逆变器根据组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值；汇流箱在每个组串输出电压值获取流经光伏组串的输出电流值，并将组串输出电压值及输出电流值发送至预设控制器；预设控制器根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集。本发明实施例通过光伏组串的组串开路电压及输出电流值实现单个光伏组串的IV扫描功能，有利于提高扫描精度，提升光伏电池板性能预测准确性。

Description

光伏系统及其IV扫描方法、装置和汇流箱
本申请要求于2021年08月04日提交中国专利局、申请号为202110890554.3、发明名称为“光伏系统及其IV扫描方法、装置和汇流箱”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及光伏发电技术领域，特别涉及一种光伏系统及其IV扫描方法、装置和汇流箱。
背景技术
光伏阵列是光伏系统的核心部件，其长期工作于室外环境，光伏阵列的性能会受到使用年限、自然环境因素的影响，对光伏组件进行发电能力评估和故障测试，对提升光伏系统发电量具有重要意义。
目前，光伏组件的测试通常采用IV扫描技术，IV扫描技术是指采用逆变器或者IV扫描设备对电池板的输出电压和输出电流进行采样，再结合采样得到光伏阵列的光照度、温度等数据，判断光伏组件是否存在遮挡、损坏、热斑等异常情况，还可用于分析电池组件的衰减等情况。
但是，现有的IV扫描技术仅在组串式逆变器上实现，对于集中式光伏发电系统而言，其无法监控到每一路光伏组串的运行情况，导致IV扫描结果不准确，影响光伏电池板的性能评估结果。
发明内容
本申请提供一种光伏系统及其IV扫描方法、装置和汇流箱，以解决现有的集中并网系统无法对单个组串进行IV扫描的问题，优化扫描特性曲线。
第一方面，本发明实施例提供了一种光伏系统IV扫描方法，所述光伏系统包括逆变器及与所述逆变器的直流侧连接的汇流箱，所述汇流箱连接m路光伏组串，m为大于1的正整数，所述扫描方法包括以下步骤：
所述汇流箱获取每个所述光伏组串的组串开路电压，并将所述组串开路电压发送至预设控制器；
所述逆变器根据所述组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从所述扫描初始电压逐步变化至预设电压下限值；
所述汇流箱在每个所述组串输出电压值获取所述光伏组串的输出电流值， 并将所述组串输出电压值及所述输出电流值发送至所述预设控制器；
所述预设控制器根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
可选地，所述获取所述光伏组串的组串开路电压，包括以下步骤：
所述逆变器对直流母线电压进行升压调节，以使电流沿第一方向从所述逆变器流向所述光伏组串；
所述逆变器对所述直流母线电压进行降压调节，直至电流沿第二方向从所述光伏组件流向所述逆变器，所述第二方向与所述第一方向相反；
所述汇流箱将电流流向翻转时刻的直流母线电压确定为所述组串开路电压。
可选地，所述逆变器对所述直流母线电压进行降压调节，包括以下步骤：
获取第二预设步长；
基于所述第二预设步长控制所述直流母线电压逐步降低。
可选地，所述根据所述组串开路电压确定扫描初始电压，包括以下步骤：
获取m路所述光伏组串的m个所述组串开路电压，所述组串开路电压与所述光伏组串一一对应；
对m个所述组串开路电压进行比较，根据比较结果确定所述组串开路电压最大值，所述扫描初始电压大于或者等于所述组串开路电压最大值。
可选地，在所述组串输出电压值达到所述预设电压下限值之后，还包括：
所述逆变器和/或所述汇流箱启动直流短路模式；
所述汇流箱采集直流短路模式下流经所述光伏组串的短路电流值，并将所述短路电流值发送至所述预设控制器；
所述预设控制器将所述短路电流值添加至所述扫描样本点集。
可选地，在得到每个所述光伏组串的扫描样本点集之后，还包括以下步骤：
根据所述扫描样本点集进行数据拟合，确定所述光伏组串的IV扫描曲线；
所述光伏组串的所述IV扫描曲线的扫描起始点为对应的所述组串开路电压。
可选地，所述预设控制器包括汇流箱控制器、逆变器控制器或者所述光伏系统中除所述汇流箱控制器及所述逆变器控制器之外的任一控制器。
第二方面，本发明实施例还提供了一种光伏系统IV扫描装置，包括：汇流箱、逆变器和预设控制器，所述汇流箱连接m路光伏组串，m为大于1的正整数；
所述汇流箱，用于获取所述光伏组串的组串开路电压，并将所述组串开路电压发送至所述预设控制器；
所述逆变器，用于根据所述组串开路电压确定扫描初始电压，并基于第一预设步长控制组串输出电压值从所述扫描初始电压逐步变化至预设电压下限值；
所述汇流箱，还用于在每个所述组串输出电压值获取所述光伏组串的输出电流值，并将所述组串输出电压值及所述输出电流值发送至所述预设控制器；
所述预设控制器，用于根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
第三方面，本发明实施例还提供了一种汇流箱，所述汇流箱的输入侧连接m路光伏组串，所述汇流箱的输出侧与逆变器的直流侧连接，所述汇流箱包括：汇流箱控制器、电流采样单元和电压采样单元；
所述电压采样单元，用于获取所述光伏组串的组串开路电压，及扫描模式下的组串输出电压值；
所述电流采样单元，用于获取所述光伏组串的输出电流值；
所述汇流箱控制器，用于根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
第四方面，本发明实施例还提供了一种光伏系统，包括上述光伏系统IV扫描装置。
本发明实施例提供的光伏系统及其IV扫描装置和汇流箱，执行IV扫描方法，该方法通过汇流箱获取每个光伏组串的组串开路电压，并将组串开路电压发送至预设控制器；通过逆变器执行MPPT扫描模式，根据组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值；汇流箱在每个组串输出电压值获取流经每个光伏组串的输出电流值，并将组串输出电压值及对应的输出电流值发送至预设控制器；预设控制器根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集，解决现有的集中并网系统无法对单个组串进行IV扫描的问 题，通过汇流箱检测单个组串的开路电压，作为单个光伏组串的IV扫描点，优化扫描特性曲线，提高扫描精度，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图示出的结构获得其他的附图。
图1是本发明实施例一提供的一种光伏系统IV扫描方法的流程图；
图2是本发明实施例一提供的另一种光伏系统IV扫描方法的流程图；
图3是本发明实施例一提供的又一种光伏系统IV扫描方法的流程图；
图4是本发明实施例一提供的又一种光伏系统IV扫描方法的流程图；
图5是本发明实施例一提供的一种IV扫描曲线的曲线示意图；
图6是本发明实施例二提供了一种光伏系统IV扫描装置的结构示意图；
图7是本发明实施例三提供的一种汇流箱的结构示意图；
图8是本发明实施例四提供的一种光伏系统的结构示意图。
具体实施方式
下面结合附图和实施例对本发明作进一步的详细说明。可以理解的是，此处所描述的具体实施例仅仅用于解释本发明，而非对本发明的限定。另外还需要说明的是，为了便于描述，附图中仅示出了与本发明相关的部分而非全部结构。
实施例一
图1是本发明实施例一提供的一种光伏系统IV扫描方法的流程图，本实施例可适用于集中式光伏并网发电系统的应用场景，该IV扫描方法可由特定的IV扫描仪设备或者逆变器与汇流箱共同参与实现。
在本实施例中，光伏系统包括逆变器及与逆变器的直流侧连接的n个汇流箱，汇流箱连接m路光伏组串，m为大于1的正整数。
如图1所示，该光伏系统IV扫描方法，具体包括以下步骤：
步骤S1：汇流箱获取每个光伏组串的组串开路电压，并将组串开路电压发送至预设控制器。
其中，汇流箱可采用集散式结构，设置n路MPPT控制器，采用每个MPPT控制器对m路光伏组串发出的直流电进行分散的最大功率点跟踪，经DC-DC汇流后输出。
在本步骤中，组串开路电压是指单个光伏组串的最大开路电压，其不同于光伏系统的最大开路电压，可用于表征单个光伏组件的发电能力，可通过汇流箱与逆变器相互配合作用，采样得到每个光伏组串的组串开路电压。
步骤S2：逆变器根据组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值。
其中，组串输出电压值即为逆变器的工作电压值。
在本步骤中，逆变器工作在IV扫描模式，并启动全局MPPT(MaximumPowerPointTracking，最大功率点跟踪)扫描功能，其工作电压按照第一预设步长从扫描初始电压逐渐下降至预设电压下限值，该预设电压下限值可为MPP(MaximumPowerPoint，最大功率点)电压下限值。
示例性地，可设置第一预设步长等于1V，即言，在扫描过程中，每经过调压间隔时间，将其工作电压减小1V，直至组串输出电压值小于或者等于预设电压下限值。
步骤S3：汇流箱在每个组串输出电压值获取光伏组串的输出电流值，并将组串输出电压值及输出电流值发送至预设控制器。
在本步骤中，汇流箱可设置m路电流采样单元，m路电流采样单元与m路光伏组串一一对应，在任一组串输出电压值点，电流采样单元采集对应的光伏组串的输出电流值，由此，汇流箱可通过采样得到每个光伏组件的多个组串输出电压值及其对应的输出电流值。
步骤S4：预设控制器根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集。
其中，该扫描样本点集可用于绘制单个光伏组串的IV特性曲线，在每个光伏组串的扫描样本点集中，组串输出电压值中的最大值可为组串开路电压。
可选地，预设控制器可包括汇流箱控制器、逆变器控制器或者光伏系统中 除汇流箱控制器及逆变器控制器之外的任一控制器。
可选地，预设控制器还可与光伏上位机系统连接，接收上位机系统下发的扫描指令，并将扫描样本点集或者最终生成的IV特性曲线发送至光伏上位机系统，用于对光伏组件进行在线故障监控。
具体地，逆变器在接收到扫描指令之后，启动全局MPPT(MaximumPowerPointTracking，最大功率点跟踪)扫描模式，控制组串输出电压值按照第一预设步长从扫描初始电压逐渐下降，同时，汇流箱采样在不同组串输出电压值Ui每个光伏组串的输出电流值Ii，记录对应的电压电流点(Ui，Ii)，逆变器实时判断组串输出电压值是否小于或者等于预设电压下限值，若组串输出电压值小于或者等于预设电压下限值，则逆变器结束全局MPPT扫描模式，进入下一工作模式。在逆变器结束全局MPPT扫描模式之后，汇流箱将采样到的所有电压电流点(Ui，Ii)及每个光伏组串对应的组串开路电压U0发送至预设控制器，预设控制器根据组串开路电压U0分别生成每个光伏组串对应的扫描样本点集，解决现有的集中并网系统无法对单个组串进行IV扫描的问题，通过汇流箱检测单个组串的开路电压，作为单个光伏组串的IV扫描点，优化扫描特性曲线，提高扫描精度，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
可选地，图2是本发明实施例一提供的另一种光伏系统IV扫描方法的流程图，在图1的基础上，示例性地示出一种获取组串开路电压的方法的具体实施方式，而非对上述方法的限定。
参考图2所示，上述步骤S1中获取光伏组串的组串开路电压，包括以下步骤：
步骤S101：逆变器对直流母线电压进行升压调节，以使电流沿第一方向从逆变器流向光伏组串。
在本步骤中，逆变器可一步将直流母线电压抬升至最大工作电压(例如，最大工作电压可为1500V)，在最大工作电压作用下，所有光伏组串的输出电流流向均为第一方向。
步骤S102：逆变器对直流母线电压进行降压调节，直至电流沿第二方向从光伏组件流向逆变器，第二方向与第一方向相反。
在本步骤中，各个光伏组串的性能不统一，会造成每个光伏组串的组串开路电压差异，逆变器可控制直流母线电压逐步下降，实现不同光伏组串所在的支路电流分步翻转。
可选地，逆变器对直流母线电压进行降压调节，包括：获取第二预设步长，其中，第二预设步长包括预设降压幅值；基于第二预设步长控制直流母线电压逐步降低，直至电流流向发生翻转。
在本实施例中，可设置预设降压幅值小于0.1V，逆变器每间隔预设间隔时间，控制直流母线电压减少预设降压幅值，直至所有光伏组串所在的支路均发生电流流向翻转。
步骤S103：汇流箱将电流流向翻转时刻的直流母线电压确定为组串开路电压。
具体地，汇流箱可采样光伏组件汇流后的输出电压作为直流母线电压，在逆变器进入IV扫描模式之前，先执行开路电压检测，逆变器先抬升直流母线电压至最大工作电压，此时，汇流箱采样到的每个光伏组串的输出电流流向均为第一方向(例如为反向)；逆变器以第二预设步长控制直流母线电压逐步降低，同时，汇流箱采样每个光伏组串的输出电流，在直流母线电压降压过程中，若任一路光伏组串的输出电流从第一方向翻转为第二方向(例如为正向)，即电流从反向转为正向，则汇流箱判定电流流向翻转时刻的直流母线电压为该路光伏组串的组串开路电压。
需要说明的是，在对直流母线电压进行降压调节的过程中，第二预设步长的降压幅值越小，采样得到的组串开路电压精度越高。
由此，本发明实施例通过逆变器与汇流箱相互配合，通过支路电流翻转对各个光伏组串的组串开路电压进行独立检测，将其作为单个光伏组串的IV扫描点，优化扫描特性曲线，提高扫描精度，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
可选地，根据组串开路电压确定扫描初始电压，包括以下步骤：获取m路光伏组串的m个组串开路电压，组串开路电压与光伏组串一一对应；对m个组串开路电压进行比较，根据比较结果确定组串开路电压最大值，扫描初始电压大于或者等于组串开路电压最大值。
具体地，在组串开路电压检测阶段，先对各个光伏组串的开路电压进行检测，得到m个组串开路电压，通过比较取得m个组串开路电压中的组串开路电压最大值，逆变器设置扫描初始电压大于或者等于组串开路电压最大值，在逆变器进入IV扫描模式之后，逆变器的工作电压逐步下降，可得到所有光伏组串在开路电压点的IV扫描数据，有利于实现所有光伏组件的全曲线段IV扫描。
可选地，逆变器可将最大工作电压作为扫描初始电压，对此不作限制。
可选地，图3是本发明实施例一提供的又一种光伏系统IV扫描方法的流程图，在图1的基础上，示例性地给出了组串输出电压值达到预设电压下限值之后，进行样本点扫描的一种实施方式。
如图3所示，在组串输出电压值达到预设电压下限值之后，还包括：
步骤S301：逆变器和/或汇流箱启动直流短路模式。
步骤S302：汇流箱采集直流短路模式下流经光伏组串的短路电流值，并将短路电流值发送至预设控制器。
步骤S303：预设控制器将短路电流值添加至扫描样本点集。
具体地，在组串输出电压低于预设电压下限值(例如为MPPT下限值)之后，逆变器可将所有开关管均关闭，或者，汇流箱对汇流输出侧进行短路，以使系统进入直流短路模式，汇流箱采集流经每个光伏组串的短路电流值，预设控制器记录该短路电流值及对应的短路电压值(可定义为0)，对扫描样本点进行更新补充。
需要说明的是，在直流短路模式下，系统的散热及耐流值均需保留较大的设计裕量，避免直流短路模式造成系统元件过流损毁。
可选地，图4是本发明实施例一提供的又一种光伏系统IV扫描方法的流程图。参考图4所示，在得到每个光伏组串的扫描样本点集之后，还包括：
步骤S5：根据扫描样本点集进行数据拟合，确定光伏组串的IV扫描曲线，其中，光伏组串的IV扫描曲线的扫描起始点为对应的组串开路电压。
具体地，在组串输出电压低于预设电压下限值之前，记录预设控制器记录的组串开路电压点(含组串开路电压点)至MPPT下限电压点(含MPPT下限电压点)之间的所有电压电流数据(Ui，Ii)作为扫描样本点，绘制第一阶段的IV扫描曲线。在组串输出电压低于预设电压下限值之后，光伏组串的输出电 压和输出电流无法通过采样测量，可采用预设控制器记录的组串开路电压点(含组串开路电压点)至MPPT下限电压点(含MPPT下限电压点)之间的所有电压电流数据(Ui，Ii)作为智能拟合的原始数据，结合预设拟合函数，拟合得到各个光伏组串第二阶段的IV扫描曲线。同一光伏组串的第一阶段的IV扫描曲线与第二阶段的IV扫描曲线共同构成该光伏组串的IV扫描曲线，有利于实现全电压范围的IV扫描，优化扫描特性曲线。
可选地，在对第二阶段的IV扫描曲线进行拟合时，可将直流母线短路测量得到的短路电流值及短路电压值(可定义为0)导入拟合函数，对拟合曲线进行修正，优化扫描特性曲线，提高扫描精度。
可选地，图5是本发明实施例一提供的一种IV扫描曲线的曲线示意图。
结合图5所示，若定义组串开路电压点为第一扫描样本点(U0，I0)，预设电压下限点为第二扫描样本点(Up，Ip)，直流短路电流点为第三扫描样本点(0，Id)，则第一阶段的IV扫描曲线的扫描起点为第一扫描样本点(U0，I0)，扫描终点为第二扫描样本点(Up，Ip)；拟合得到的第二阶段的IV扫描曲线的起点为第二扫描样本点(Up，Ip)，终点为第三扫描样本点(0，Id)。
实施例二
本发明实施例二提供了一种光伏系统IV扫描装置，本发明实施例所提供的光伏系统IV扫描装置可执行本发明任意实施例所提供的光伏系统IV扫描方法，具备执行方法相应的功能模块和有益效果。
图6是本发明实施例二提供了一种光伏系统IV扫描装置的结构示意图。
该光伏系统IV扫描装置00包括：汇流箱01、逆变器02和预设控制器03，汇流箱01连接m路光伏组串，m路光伏组串PV包括第一路光伏组串PV1、第二路光伏组串PV2，……，第m路光伏组串PVm，m为大于1的正整数；汇流箱01，用于获取光伏组串的组串开路电压，并将组串开路电压发送至预设控制器；逆变器02，用于根据组串开路电压确定扫描初始电压，并基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值；汇流箱01，还用于在每个组串输出电压值获取光伏组串的输出电流值，并将组串输出电压值及输出电流值发送至预设控制器；预设控制器03，用于根据组串开路电压、组串 输出电压值及输出电流值确定每个光伏组串的扫描样本点集。
可选地，预设控制器可与汇流箱控制器或者逆变器控制器集成设置，或者可采用光伏系统中除汇流箱控制器及逆变器控制器之外的任一控制器。
可选地，逆变器02还用于对直流母线电压进行升压调节，以使电流沿第一方向从逆变器流向光伏组串，及对直流母线电压进行降压调节，直至电流沿第二方向从光伏组件流向逆变器，第二方向与第一方向相反；汇流箱01还用于将电流流向翻转时刻的直流母线电压确定为组串开路电压。
可选地，对直流母线电压进行降压调节，包括：获取第二预设步长，并基于第二预设步长控制直流母线电压逐步降低。
可选地，根据组串开路电压确定扫描初始电压，包括：获取m路光伏组串的m个组串开路电压，组串开路电压与光伏组串一一对应；对m个组串开路电压进行比较，根据比较结果确定组串开路电压最大值，扫描初始电压大于或者等于组串开路电压最大值。
可选地，在组串输出电压值达到预设电压下限值之后，逆变器和/或汇流箱启动直流短路模式；汇流箱采集直流短路模式下流经光伏组串的短路电流值，并将短路电流值发送至预设控制器；预设控制器将短路电流值添加至扫描样本点集。
可选地，预设控制器还用于在得到每个光伏组串的扫描样本点集之后，根据扫描样本点集进行数据拟合，确定光伏组串的IV扫描曲线，其中，光伏组串的IV扫描曲线的扫描起始点为对应的组串开路电压。
由此，本发明实施例提供的光伏系统IV扫描装置，执行IV扫描方法，该方法通过汇流箱获取每个光伏组串的组串开路电压，并将组串开路电压发送至预设控制器；通过逆变器执行MPPT扫描模式，根据组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值；汇流箱在每个组串输出电压值获取每个光伏组串的输出电流值，并将组串输出电压值及对应的输出电流值发送至预设控制器；预设控制器根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集，解决现有的集中并网系统无法对单个组串进行IV扫描的问题，通过汇流箱检测单个组串的开路电压，作为单个光伏组串的IV扫描点，有利于优化扫描特 性曲线，提高扫描精度，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
实施例三
本发明实施例三提供了一种汇流箱，该汇流箱的输入侧连接m路光伏组串，该汇流箱的输出侧与逆变器的直流侧连接。
图7是本发明实施例三提供的一种汇流箱的结构示意图。
如图7所示，该汇流箱01包括：汇流箱控制器101、电流采样单元102和电压采样单元103，其中，电压采样单元103，用于获取光伏组串的组串开路电压，及扫描模式下的组串输出电压值；电流采样单元102，用于获取光伏组串的输出电流值；汇流箱控制器101，用于根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集。
本实施例中，汇流箱可为集散式汇流箱，在集散式汇流箱中，设置多路MPPT控制器，采用MPPT控制器对m路光伏组串发出的直流电进行分散的最大功率点跟踪，经DC-DC变换后汇流输出至逆变器的直流侧。
可选地，汇流箱01还用于将电流流向翻转时刻的直流母线电压确定为组串开路电压，可采用逆变器02对直流母线电压进行升压调节，以使电流沿第一方向从逆变器流向光伏组串，及对直流母线电压进行降压调节，直至电流沿第二方向从光伏组件流向逆变器，第二方向与第一方向相反，实现电流流向翻转检测。
由此，本发明实施例提供的汇流箱，配置电压电流检测功能，并根据电流翻转检测单个光伏组串的开路电压，优化扫描特性曲线，提高扫描精度，，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
实施例四
图8是本发明实施例四提供的一种光伏系统的结构示意图，该光伏系统可为集中式光伏发电系统。
如图8所示，该光伏系统100包括上述光伏系统IV扫描装置00。
本发明实施例提供的光伏系统，设置光伏系统IV扫描装置，执行IV扫描方 法，该方法通过汇流箱获取每个光伏组串的组串开路电压，并将组串开路电压发送至预设控制器；通过逆变器执行MPPT扫描模式，根据组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从扫描初始电压逐步变化至预设电压下限值；汇流箱在每个组串输出电压值获取每个光伏组串的输出电流值，并将组串输出电压值及对应的输出电流值发送至预设控制器；预设控制器根据组串开路电压、组串输出电压值及输出电流值确定每个光伏组串的扫描样本点集，解决现有的集中并网系统无法对单个组串进行IV扫描的问题，通过汇流箱检测单个组串的开路电压，作为单个光伏组串的IV扫描点，优化扫描特性曲线，提高扫描精度，提升光伏电池板性能预测准确性，有利于提高光伏系统发电量。
注意，上述仅为本发明的较佳实施例及所运用技术原理。本领域技术人员会理解，本发明不限于这里所述的特定实施例，对本领域技术人员来说能够进行各种明显的变化、重新调整和替代而不会脱离本发明的保护范围。因此，虽然通过以上实施例对本发明进行了较为详细的说明，但是本发明不仅仅限于以上实施例，在不脱离本发明构思的情况下，还可以包括更多其他等效实施例，而本发明的范围由所附的权利要求范围决定。

Claims (10)

  1. 一种光伏系统IV扫描方法，所述光伏系统包括逆变器及与所述逆变器的直流侧连接的汇流箱，所述汇流箱连接m路光伏组串，m为大于1的正整数，其特征在于，所述扫描方法包括以下步骤：
    所述汇流箱获取所述光伏组串的组串开路电压，并将所述组串开路电压发送至预设控制器；
    所述逆变器根据所述组串开路电压确定扫描初始电压，基于第一预设步长控制组串输出电压值从所述扫描初始电压逐步变化至预设电压下限值；
    所述汇流箱在每个所述组串输出电压值获取所述光伏组串的输出电流值，并将所述组串输出电压值及所述输出电流值发送至所述预设控制器；
    所述预设控制器根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
  2. 根据权利要求1所述的光伏系统IV扫描方法，其特征在于，所述获取所述光伏组串的组串开路电压，包括以下步骤：
    所述逆变器对直流母线电压进行升压调节，以使电流沿第一方向从所述逆变器流向所述光伏组串；
    所述逆变器对所述直流母线电压进行降压调节，直至电流沿第二方向从所述光伏组件流向所述逆变器，所述第二方向与所述第一方向相反；
    所述汇流箱将电流流向翻转时刻的直流母线电压确定为所述组串开路电压。
  3. 根据权利要求2所述的光伏系统IV扫描方法，其特征在于，所述逆变器对所述直流母线电压进行降压调节，包括：
    获取第二预设步长；
    基于所述第二预设步长控制所述直流母线电压逐步降低。
  4. 根据权利要求1所述的光伏系统IV扫描方法，其特征在于，所述根据所述组串开路电压确定扫描初始电压，包括以下步骤：
    获取m路所述光伏组串的m个所述组串开路电压，所述组串开路电压与所述光伏组串一一对应；
    对m个所述组串开路电压进行比较，根据比较结果确定所述组串开路电压最大值，所述扫描初始电压大于或者等于所述组串开路电压最大值。
  5. 根据权利要求1所述的光伏系统IV扫描方法，其特征在于，在所述组串输出电压值达到所述预设电压下限值之后，还包括：
    所述逆变器和/或所述汇流箱启动直流短路模式；
    所述汇流箱采集直流短路模式下流经所述光伏组串的短路电流值，并将所述短路电流值发送至所述预设控制器；
    所述预设控制器将所述短路电流值添加至所述扫描样本点集。
  6. 根据权利要求1所述的光伏系统IV扫描方法，其特征在于，在得到每个所述光伏组串的扫描样本点集之后，还包括以下步骤：
    根据所述扫描样本点集进行数据拟合，确定所述光伏组串的IV扫描曲线；
    所述光伏组串的所述IV扫描曲线的扫描起始点为对应的所述组串开路电压。
  7. 根据权利要求1所述的光伏系统IV扫描方法，其特征在于，所述预设控制器包括汇流箱控制器、逆变器控制器或者所述光伏系统中除所述汇流箱控制器及所述逆变器控制器之外的任一控制器。
  8. 一种光伏系统IV扫描装置，其特征在于，包括：汇流箱、逆变器和预设控制器，所述汇流箱连接m路光伏组串，m为大于1的正整数；
    所述汇流箱，用于获取所述光伏组串的组串开路电压，并将所述组串开路电压发送至所述预设控制器；
    所述逆变器，用于根据所述组串开路电压确定扫描初始电压，并基于第一预设步长控制组串输出电压值从所述扫描初始电压逐步变化至预设电压下限值；
    所述汇流箱，还用于在每个所述组串输出电压值获取所述光伏组串的输出电流值，并将所述组串输出电压值及所述输出电流值发送至所述预设控制器；
    所述预设控制器，用于根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
  9. 一种汇流箱，所述汇流箱的输入侧连接m路光伏组串，所述汇流箱的输出侧与逆变器的直流侧连接，其特征在于，所述汇流箱包括：汇流箱控制器、 电流采样单元和电压采样单元；
    所述电压采样单元，用于获取所述光伏组串的组串开路电压，及扫描模式下的组串输出电压值；
    所述电流采样单元，用于获取所述光伏组串的输出电流值；
    所述汇流箱控制器，用于根据所述组串开路电压、所述组串输出电压值及所述输出电流值确定每个所述光伏组串的扫描样本点集。
  10. 一种光伏系统，其特征在于，包括权利要求8所述的光伏系统IV扫描装置。
PCT/CN2022/094853 2021-08-04 2022-05-25 光伏系统及其iv扫描方法、装置和汇流箱 WO2023010955A1 (zh)

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