DC / DC branch parallel detection method and device, and photovoltaic inverter

Abstract

The present application relates to a DC / DC branch parallel detection method and device, and a photovoltaic inverter. The parallel detection method comprises: before a photovoltaic inverter is started, detecting input voltages of a plurality of DC / DC branches (S100); selecting a first DC / DC branch from among the plurality of DC / DC branches, and determining second DC / DC branches from among the remaining DC / DC branches, wherein absolute values of differences between the input voltages of the second DC / DC branches and the input voltage of the first DC / DC branch are less than a first preset value (S200); turning on the first DC / DC branch such that the input voltage of the first DC / DC branch decreases, and determining a third DC / DC branch from among the second DC / DC branches, wherein an absolute value of a difference between the input voltage of the third DC / DC branch and the input voltage of the first DC / DC branch is less than a second preset value (S300); determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to a same photovoltaic string (S400); and controlling the third DC / DC branch to perform voltage output along with the first DC / DC branch (S500).

Description

Parallel detection method and device for DC / DC branches and photovoltaic inverter thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311601851.7 filed on November 27, 2023, entitled “Parallel detection method, device and photovoltaic inverter for DC / DC branches”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of circuit parallel detection, and in particular to a parallel detection method and device for DC / DC branches and a photovoltaic inverter thereof. Background Art

[0004] An inverter is a power regulation device composed of semiconductor devices, primarily used to convert direct current (DC) power into alternating current (AC). The photovoltaic input side of a photovoltaic inverter typically has multiple photovoltaic DC / DC branches, each of which can be connected to a separate photovoltaic string.

[0005] With the development of photovoltaic panel technology, the current that a single photovoltaic string can provide is getting larger and larger. It is necessary to connect two or more DC / DC branches in parallel to the same photovoltaic string to reduce the current on the photovoltaic input side. When two DC / DC branches are connected to two different photovoltaic strings separately, the two DC / DC branches need to be controlled separately. When two DC / DC branches are connected in parallel to the same photovoltaic string, the control of one DC / DC branch needs to follow the other DC / DC branch. In actual use, there may be a mix of the above two connection methods. Therefore, it is necessary to determine the connection method of multiple DC / DC branches on the photovoltaic input side of the photovoltaic inverter to determine the control mode. In the related art, the method for determining whether multiple DC / DC branches on the photovoltaic input side are connected in parallel is that the installation engineer manually sets the connection method to parallel or series when installing the photovoltaic panels and photovoltaic inverters on site, and records the connection relationship between the photovoltaic panels and photovoltaic inverters. However, this method increases labor costs and is prone to errors.

[0006] Summary of the Invention

[0007] The present application aims to at least partially solve one of the technical problems existing in the prior art. To this end, the embodiments of the present application provide a parallel detection method and device for DC / DC branches and a photovoltaic inverter thereof.

[0008] In a first aspect, an embodiment of the present application provides a parallel detection method for DC / DC branches, which is applied to a photovoltaic inverter. The photovoltaic inverter includes a processor and multiple DC / DC branches connected thereto. The input end of the DC / DC branch is connected to a photovoltaic string. The method executed by the processor includes:

[0009] Before starting the photovoltaic inverter, detecting input voltages of a plurality of DC / DC branches;

[0010] Selecting a first DC / DC branch from the plurality of DC / DC branches, and determining a second DC / DC branch from the remaining DC / DC branches, wherein the second DC / DC branch satisfies that an absolute value of a difference between an input voltage thereof and an input voltage of the first DC / DC branch is less than a first preset value;

[0011] Turning on the first DC / DC branch to reduce the input voltage of the first DC / DC branch, and determining a third DC / DC branch from the second DC / DC branch, where the third DC / DC branch satisfies the condition that the absolute value of the difference between the input voltage of the third DC / DC branch and the input voltage of the first DC / DC branch is less than a second preset value;

[0012] Determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string; and

[0013] The third DC / DC branch is controlled to follow the first DC / DC branch to output voltage.

[0014] According to some embodiments of the present application, a fourth DC / DC branch is determined from the second DC / DC branch, where the fourth DC / DC branch is another DC / DC branch in the second DC / DC branch except the third DC / DC branch.

[0015] selecting a fifth DC / DC branch from the fourth DC / DC branch, turning on the fifth DC / DC branch to reduce the input voltage of the fifth DC / DC branch, and determining a sixth DC / DC branch from the remaining DC / DC branches of the fourth DC / DC branch, wherein the absolute value of the difference between the input voltage of the sixth DC / DC branch and the input voltage of the fifth DC / DC branch is less than the second preset value;

[0016] Determining that the fifth DC / DC branch and the sixth DC / DC branch are connected in parallel to the same photovoltaic string; and

[0017] The sixth DC / DC branch is controlled to follow the fifth DC / DC branch to output voltage.

[0018] According to some embodiments of the present application, turning on the first DC / DC branch to reduce the input voltage of the first DC / DC branch and determining a third DC / DC branch from the second DC / DC branch includes:

[0019] Turning on the first DC / DC branch and detecting an input voltage of the first DC / DC branch;

[0020] When the input voltage of the first DC / DC branch drops to a first preset voltage, detecting the input voltage of the second DC / DC branch; and

[0021] All the second DC / DC branches are traversed, and if the absolute value of the difference between the input voltage of any second DC / DC branch and the first preset voltage is less than the second preset value, the current second DC / DC branch is determined to be the third DC / DC branch.

[0022] According to some embodiments of the present application, an absolute value of a difference between the first preset voltage and an open-circuit voltage of a photovoltaic string corresponding to the first DC / DC branch is greater than a third preset value.

[0023] According to some embodiments of the present application, determining the second DC / DC branch from the remaining DC / DC branches includes:

[0024] detecting an input voltage of the first DC / DC branch; and

[0025] Detecting input voltages of DC / DC branches other than the first DC / DC branch, and determining that the current DC / DC branch is the second DC / DC branch if an absolute value of a difference between the input voltage of any DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value.

[0026] According to some embodiments of the present application, after detecting the input voltages of the plurality of DC / DC branches, the method further includes:

[0027] Determining whether the input voltage of the DC / DC branch is less than a fourth preset value, where the fourth preset value represents a startup voltage of the DC / DC branch; and

[0028] If the input voltage of the DC / DC branch is less than the fourth preset value, a fault reminder is issued.

[0029] According to some embodiments of the present application, the second preset value ranges from 5V to 20V.

[0030] In a second aspect, an embodiment of the present application provides a parallel detection device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the method described in the technical solution of the first aspect above when running the computer program.

[0031] In a third aspect, an embodiment of the present application provides a photovoltaic inverter, comprising a DC / DC branch and the parallel detection device described in the technical solution of the second aspect above, wherein the DC / DC branch is used to connect photovoltaic strings, and the parallel detection device is used to detect the input voltage of the DC / DC branch.

[0032] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions are used to execute the method described in the technical solution of the first aspect above.

[0033] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purposes and other advantages of the present application can be achieved and obtained through the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a flow chart of a parallel detection method for DC / DC branches provided in an embodiment of the present application;

[0035] FIG2 is a schematic structural diagram of a DC / DC branch connected in parallel to a photovoltaic string according to an embodiment of the present application;

[0036] FIG3 is a schematic diagram of a structure in which a plurality of DC / DCs and photovoltaic strings are connected, according to an embodiment of the present application;

[0037] FIG4 is a flow chart of another method for detecting parallel connection of DC / DC branches provided in an embodiment of the present application;

[0038] FIG5 is a flowchart of a method for determining a third DC / DC branch from a second DC / DC branch provided by an embodiment of the present application;

[0039] FIG6 is a flowchart of a method for determining a second DC / DC branch from remaining DC / DC branches provided in an embodiment of the present application;

[0040] FIG7 is a flow chart of a method for determining whether an input voltage of a DC / DC branch is faulty, provided by an embodiment of the present application; and

[0041] FIG8 is a schematic structural diagram of a parallel detection device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementation methods. At the same time, the steps or actions in the method description can also be swapped or adjusted in order in a manner that is obvious to those skilled in the art. Therefore, the various orders in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a necessary order, unless otherwise specified that a certain order must be followed.

[0043] In the description of this application, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The terms "first" and "second" are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or as implicitly specifying the number or order of the technical features indicated.

[0044] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings).

[0045] A photovoltaic inverter is a power conditioning device composed of semiconductor devices, primarily used to convert direct current (DC) power into alternating current (AC). In addition, it maximizes the performance of solar cells and provides system fault protection. The input side of a photovoltaic inverter can connect multiple photovoltaic DC / DC branches. Each photovoltaic DC / DC branch is controlled by a corresponding DC / DC branch, and each DC / DC branch operates independently. With the advancement of photovoltaic panel technology, the current provided by a single photovoltaic string has increased. This necessitates the need for two or more DC / DC branches connected in parallel to the same photovoltaic string. When two DC / DC branches are connected to different photovoltaic strings, they require independent control. When two DC / DC branches are connected in parallel to the same photovoltaic string, the control of one DC / DC branch follows that of the other. In actual use, a mix of the two connection methods is possible. Therefore, it is necessary to determine the connection method for the multiple DC / DC branches on the photovoltaic input side of the photovoltaic inverter to determine the control mode. In related technologies, the method for determining whether multiple DC / DC branches on the photovoltaic input side are connected in parallel is that when installing photovoltaic panels and photovoltaic inverters on site, the installation engineer manually sets multiple DC / DC branches to be connected in parallel to the same photovoltaic string or multiple DC / DC branches to be connected separately to different photovoltaic strings, records the connection relationship between the photovoltaic panels and photovoltaic inverters, and controls the switching of multiple DC / DC branches based on the connection method of the multiple DC / DC branches recorded by the installation engineer. This method requires the installation engineer to manually divide the connection relationship between the DC / DC branches, which increases labor costs, is prone to errors, and can easily cause control confusion or even failure of the DC / DC branches.

[0046] Based on this, the embodiments of the present application provide a parallel detection method and device for DC / DC branches and a photovoltaic inverter thereof, which can automatically detect the input wiring mode of multiple DC / DC branches on the input side of the photovoltaic inverter, reduce labor costs and improve the reliability of the detection results.

[0047] 1 , which is a flow chart of a method for detecting parallel connection of DC / DC branches according to an embodiment of the present application, including steps S100 to S500 . Specifically,

[0048] Step S100: Before starting the photovoltaic inverter, detecting the input voltages of multiple DC / DC branches;

[0049] Step S200: selecting a first DC / DC branch from the plurality of DC / DC branches, and determining a second DC / DC branch from the remaining DC / DC branches, wherein the second DC / DC branch satisfies that the absolute value of the difference between the input voltage of the second DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value;

[0050] Step S300: turning on the first DC / DC branch to reduce the input voltage of the first DC / DC branch, and determining a third DC / DC branch from the second DC / DC branch, where the third DC / DC branch satisfies the condition that the absolute value of the difference between the input voltage of the third DC / DC branch and the input voltage of the first DC / DC branch is less than a second preset value;

[0051] Step S400: Determine that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string;

[0052] Step S500: controlling the third DC / DC branch to follow the first DC / DC branch to output voltage.

[0053] In some embodiments of the present application, a parallel detection method for DC / DC branches includes first detecting the input voltages of multiple DC / DC branches before starting the photovoltaic inverter to ensure that the input voltage of each DC / DC branch meets its own start-up voltage, selecting any one DC / DC branch from the multiple DC / DC branches as the first DC / DC branch, and confirming among the remaining DC / DC branches that the DC / DC branch whose input voltage has an absolute value of a difference with the input voltage of the first DC / DC branch is less than a first preset difference is the second DC / DC branch, and preliminarily determining that the first DC / DC branch and the second DC / DC branch whose input voltage difference has an absolute value less than the first preset difference may be connected in parallel to the same photovoltaic string, or the first DC / DC branch and the second DC / DC branch are respectively connected to two photovoltaic strings with similar open-circuit voltages.

[0054] In order to determine the control mode of each DC / DC branch, it is necessary to further detect the connection relationship between the first DC / DC branch and the second DC / DC branch. The first DC / DC branch is turned on to cause the input voltage of the first DC / DC branch to decrease. A DC / DC branch whose input voltage follows the decrease and whose input voltage has an absolute value less than a second preset value than the input voltage of the first DC / DC branch is identified from the second DC / DC branch and is determined to be the third DC / DC branch. Because the absolute value of the input voltage difference between the first DC / DC branch and the third DC / DC branch is less than the first preset difference, the connection relationship between the first DC / DC branch and the third DC / DC branch is determined to be parallel to the same photovoltaic string, and the third DC / DC branch is controlled to follow the first DC / DC branch in voltage output.

[0055] In the present application, multiple DC / DC branches are automatically detected and screened according to the input voltage, and then the input voltage of the first DC / DC branch is reduced to determine that the DC / DC branch whose input voltage follows the change of the first DC / DC branch and the absolute value of the difference between the input voltage of the first DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value is the third DC / DC branch, thereby determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string. There is no need for installation engineers to manually divide and record the connection relationship between photovoltaic panels and photovoltaic inverters when installing photovoltaic panels and photovoltaic inverters, which saves labor costs and improves the reliability of parallel detection results.

[0056] It should be noted that in energy management systems, the following control of two parallel DC / DC branches is typically implemented through a master-slave control approach. One DC / DC branch serves as the master controller, and the other as the slave controller. The master controller controls the output voltage, while the slave controller adjusts its output voltage based on the master's output voltage, maintaining consistency with that of the master. Specifically, the master controller obtains output voltage information through a feedback circuit and performs control. The slave controller compares the master's output voltage with its own output voltage to adjust its own output voltage to maintain consistency with that of the master. This following control method ensures that the output voltages of the parallel DC / DC branches are consistent, improving the stability and reliability of the photovoltaic inverter. In practical applications, following control typically requires consideration of multiple factors, such as the selection of the master and slave controllers, the design of the control algorithm, and the design of the feedback circuit, to ensure the stability and accuracy of following control.

[0057] It is understood that the first DC / DC branch acts as a master controller, and the third DC / DC branch acts as a slave controller, following the output voltage of the first DC / DC branch to adjust its own output voltage to maintain consistency with the output voltage of the first DC / DC branch. The processor outputs a PWM waveform to control the output voltage of the first DC / DC branch, and then the output voltage of the third DC / DC branch follows the output voltage of the first DC / DC branch to adjust its own output voltage so that the output voltage of the third DC / DC branch is consistent with the output voltage of the first DC / DC branch, thereby achieving the voltage output of the third DC / DC branch following the first DC / DC branch.

[0058] It should be noted that in some embodiments of the present application, the parallel detection method of the DC / DC branch described above determines that the other DC / DC branches in the second DC / DC branch except the third DC / DC branch are not connected in parallel to the same photovoltaic string as the first DC / DC branch. Therefore, the processor separately controls the other DC / DC branches in the second DC / DC branch except the third DC / DC branch.

[0059] It should be noted that in some embodiments of the present application, in order to ensure that the sampling error of the input voltage of the DC / DC branch is as small as possible, the value range of the first preset value is set to 5V to 20V, and a DC / DC branch whose absolute value of the difference between the input voltage of the first DC / DC branch and the input voltage of the first DC / DC branch is between 5V and 20V is selected from multiple DC / DC branches and determined as the second DC / DC branch. Since the difference in input voltage between the first DC / DC branch and the second DC / DC branch is 5V to 20V and is relatively small, it is preliminarily determined that the first DC / DC branch and the second DC / DC branch are connected in parallel to the same photovoltaic string or are connected to two photovoltaic strings with similar open-circuit voltages. Those skilled in the art can set the size of the first preset value according to actual conditions, and the embodiments of the present application do not limit the value range of the first preset value.

[0060] It should be noted that in some embodiments of the present application, to ensure that the sampling error of the DC / DC branch input voltage is as small as possible, the second preset value is in the range of 5V to 20V. By setting the second preset value in the range of 5V to 20V, after the voltage of the first DC / DC branch is gradually reduced, a DC / DC branch is selected from the second DC / DC branch whose absolute value of the input voltage difference with the first DC / DC branch is between 5V and 20V, and is determined as the third DC / DC branch. Because the second preset value is between 5V and 20V, i.e., the absolute value of the input voltage difference between the first DC / DC branch and the third DC / DC branch is small, the first DC / DC branch and the third DC / DC branch are determined to be connected in parallel to the same PV string.

[0061] Referring to FIG. 2 , FIG. 2 is a schematic diagram of a structure in which a DC / DC branch is connected in parallel to a photovoltaic string, according to an embodiment of the present application. In some embodiments of the present application, if two DC / DC branches are provided on the input side of a photovoltaic inverter, a method for detecting the parallel connection of the DC / DC branches includes, before starting the photovoltaic inverter, first detecting the input voltages of the two DC / DC branches, then determining whether the absolute value of the difference between the input voltages of the two DC / DC branches is within a range of 5V to 20V. If the absolute value of the difference between the input voltages of the two DC / DC branches is greater than 20V, it is preliminarily determined that the two DC / DC branches are not connected in parallel to the same photovoltaic string, the photovoltaic inverter is started, and the two DC / DC branches are controlled separately. If the absolute value of the difference between the input voltages of the two DC / DC branches is between 5V and 20V, the connection relationship of the two DC / DC branches is further distinguished. Open any one of the DC / DC branches and gradually reduce its input voltage. At this time, it is determined again whether the absolute value of the difference between the input voltages of the two DC / DC branches is less than 5V to 20V. If the difference between the input voltages of the two DC / DC branches is greater than 20V, it is determined that the two DC / DC branches are not connected in parallel to the same photovoltaic string. The photovoltaic inverter is started and the two DC / DC branches are controlled separately. If the absolute value of the difference between the input voltages of the two DC / DC branches is between 5V and 20V, the photovoltaic inverter is started and enters the parallel control mode. The two DC / DC branches include a first DC / DC branch and a second DC / DC branch. The parallel control mode satisfies that the control of the second DC / DC branch follows the control of the first DC / DC branch.

[0062] The first DC / DC branch acts as the master controller, while the second DC / DC branch acts as a slave controller, following the output voltage of the first DC / DC branch to adjust its own output voltage to maintain consistency with the output voltage of the first DC / DC branch. The first DC / DC branch is responsible for controlling the output voltage. The processor outputs a PWM waveform to control the output voltage of the first DC / DC branch. The output voltage of the second DC / DC branch then follows the output voltage of the first DC / DC branch, adjusting its own output voltage to match the output voltage of the first DC / DC branch. This allows the second DC / DC branch to follow the output voltage of the first DC / DC branch.

[0063] Referring to Figure 3, Figure 3 is a structural schematic diagram of a plurality of DC / DCs and photovoltaic string connections provided by an embodiment of the present application. In some embodiments of the present application, if a plurality of DC / DC branches are provided on the input side of the photovoltaic inverter, for example, 10 DC / DC branches are provided on the input side of the photovoltaic inverter, which are numbered from the first DC / DC branch to the tenth DC / DC branch respectively, the parallel detection method of the DC / DC branches includes, before the photovoltaic inverter is turned on, detecting the input voltages of the first DC / DC branch to the tenth DC / DC branch, and judging whether the absolute value of the difference between the input voltages of any two DC / DC branches in the 10 DC / DC branches or the absolute value of the difference between the input voltages of any multiple DC / DC branches is less than a first preset value, if the absolute value of the difference between the input voltage of the first DC / DC branch and the input voltages of the second DC / DC branch to the fifth DC / DC branch are both less than the first preset value, and the input voltage of the first DC / DC branch is less than the input voltage of the sixth DC / DC branch to the tenth DC / DC The absolute value of the difference in the input voltages of the branches is greater than a first preset value. Since the first preset value is set within a range of 5V to 20V, the sampling error of the DC / DC branch input voltage is minimized. Therefore, it can be determined that the first DC / DC branch and the second to fifth DC / DC branches may be connected in parallel to the same photovoltaic string or are connected to two photovoltaic strings with similar open-circuit voltages. The sixth to tenth DC / DC branches are not connected in parallel to the same photovoltaic string as the first DC / DC branch. Therefore, the sixth to tenth DC / DC branches are controlled separately.

[0064] The first DC / DC branch is turned on to reduce its voltage, and the input voltages of the second through fifth DC / DC branches are detected. If the absolute value of the difference between the input voltage of the first DC / DC branch and the input voltages of the second and third DC / DC branches is less than a second preset value, and if the absolute value of the difference between the input voltage of the first DC / DC branch and the input voltages of the fourth and fifth DC / DC branches is greater than the second preset value, it is determined that the first DC / DC branch, the fourth DC / DC branch, and the fifth DC / DC branch are connected to different photovoltaic strings. Therefore, the first DC / DC branch is used as the master controller, and the second and third DC / DC branches are used as slave controllers. The second and third DC / DC branches are controlled to follow the first DC / DC branch in voltage output, and the fourth and fifth DC / DC branches are controlled to output voltages separately.

[0065] In some embodiments of the present application, after determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string, the photovoltaic inverter is started to convert the DC power generated by the photovoltaic string into AC power for household or industrial use. After confirming that any two or more DC / DC branches are connected in parallel to the same photovoltaic string, the present application starts any two or more DC / DC branches connected in parallel to the same photovoltaic string to perform power conversion, which can timely convert the DC power generated by the photovoltaic string into AC power for household or industrial use, thereby improving the power conversion efficiency; at the same time, it can perform overload protection, short-circuit protection and other measures on the power to ensure the safe operation of the photovoltaic power generation system.

[0066] In addition, in the embodiments of the present application, it is not necessary to determine the connection relationship between all DC / DC branches on the input side of the photovoltaic inverter before starting the DC / DC branch, which effectively avoids the sudden start-up of multiple DC / DC branches on the input side of the photovoltaic inverter, resulting in excessive load, easy short circuit, and inability to convert the electrical energy stored in the photovoltaic string in time.

[0067] The inverter can also refer to FIG4 , which is a flow chart of another DC / DC branch parallel detection method provided by an embodiment of the present application, including steps S600 to S900 , specifically,

[0068] Step S600: determining a fourth DC / DC branch from the second DC / DC branch, where the fourth DC / DC branch is the other DC / DC branch in the second DC / DC branch except the third DC / DC branch;

[0069] Step S700: selecting a fifth DC / DC branch from the fourth DC / DC branch, turning on the fifth DC / DC branch to reduce the input voltage of the fifth DC / DC branch, and determining a sixth DC / DC branch from the remaining DC / DC branches of the fourth DC / DC branch, where the sixth DC / DC branch satisfies a condition that the absolute value of the difference between the input voltage of the sixth DC / DC branch and the input voltage of the fifth DC / DC branch is less than a second preset value;

[0070] Step S800: Determine that the fifth DC / DC branch and the sixth DC / DC branch are connected in parallel to the same photovoltaic string;

[0071] Step S900: controlling the sixth DC / DC branch to follow the fifth DC / DC branch to output voltage.

[0072] In some embodiments of the present application, the parallel detection method for DC / DC branches further includes selecting the remaining DC / DC branches excluding the second DC / DC branch from the second DC / DC branch as a fourth DC / DC branch, arbitrarily selecting a DC / DC branch from the fourth DC / DC branch as a fifth DC / DC branch, and detecting the DC / DC branches in the fourth DC / DC branch that are connected in parallel with the fifth DC / DC branch to the same photovoltaic string. Specifically, the fifth DC / DC branch is enabled to gradually decrease the input voltage of the fifth DC / DC branch, and a DC / DC branch from the fourth DC / DC branch whose input voltage follows that of the fifth DC / DC branch and whose absolute value of the difference between its input voltage and the input voltage of the fifth DC / DC branch is less than a second preset value is selected as the sixth DC / DC branch. Since the absolute value of the difference between the input voltages of the fifth DC / DC branch and the sixth DC / DC branch is smaller than the second preset value, it is determined that the fifth DC / DC branch and the sixth DC / DC branch are connected in parallel to the same photovoltaic string, and the sixth DC / DC branch is controlled to follow the fifth DC / DC branch for voltage output.

[0073] In some embodiments of the present application, the fifth DC / DC branch serves as a master controller, and the sixth DC / DC branch serves as a slave controller, following the output voltage of the fifth DC / DC branch to adjust its own output voltage to maintain consistency with the output voltage of the fifth DC / DC branch. The fifth DC / DC branch is responsible for controlling the output voltage, and the processor outputs a PWM waveform to control the output voltage of the fifth DC / DC branch. The output voltage of the sixth DC / DC branch then follows the output voltage of the fifth DC / DC branch to adjust its own output voltage, so that the output voltage of the sixth DC / DC branch is consistent with the output voltage of the fifth DC / DC branch, thereby achieving the voltage output of the sixth DC / DC branch following the fifth DC / DC branch.

[0074] After the fourth DC / DC branch is determined, multiple DC / DC branches are automatically detected and screened according to the input voltage, and then the input voltage of the fifth DC / DC branch is reduced to determine that the DC / DC branch whose input voltage follows the change and the absolute value of the difference with the input voltage of the fifth DC / DC branch is less than the first preset value is the sixth DC / DC branch, thereby determining that the fifth DC / DC branch and the sixth DC / DC branch are connected in parallel to the same photovoltaic string. There is no need for installation engineers to manually divide and record the connection relationship between the photovoltaic panels and the photovoltaic inverter when installing the photovoltaic panels and the photovoltaic inverter, which saves labor costs and improves the reliability of the parallel detection results.

[0075] In some embodiments of the present application,

[0076] 5 , which is a flowchart of a method for determining a third DC / DC branch from a second DC / DC branch according to an embodiment of the present application, includes steps S310 to S330. Specifically,

[0077] Step S310: turning on the first DC / DC branch and detecting the input voltage of the first DC / DC branch;

[0078] Step S320: When the input voltage of the first DC / DC branch drops to a first preset voltage, detecting the input voltage of the second DC / DC branch;

[0079] Step S330: traverse all second DC / DC branches, and if the absolute value of the difference between the input voltage of any second DC / DC branch and the first preset voltage is smaller than the second preset value, determine that the current second DC / DC branch is the third DC / DC branch.

[0080] In some embodiments of the present application, a method for determining a third DC / DC branch from a second DC / DC branch includes starting a first DC / DC branch, gradually decreasing the input voltage of the first DC / DC branch, and when the input voltage of the first DC / DC branch drops to a first preset voltage, detecting the input voltage of the second DC / DC branch. The input voltages of all second DC / DC branches are sequentially traversed, and if the absolute value of the difference between the input voltage of any second DC / DC branch and the first preset voltage is less than a second preset value, the current second DC / DC branch is determined to be the third DC / DC branch, and the first DC / DC branch and the third DC / DC branch are determined to be connected in parallel to the same photovoltaic string.

[0081] It should be noted that in some embodiments of the present application, the absolute value of the difference between the first preset voltage and the open-circuit voltage of the photovoltaic string corresponding to the first DC / DC branch is greater than a third preset value, and the value range of the third preset value should be significantly greater than the value range of the first preset value. In the embodiment of the present application, since the value range of the first preset value is 5V to 20V, the value range of the third preset value can be set to 30V to 55V. Reducing the voltage of the first DC / DC branch to a value where the absolute value of the difference with the open-circuit voltage of the photovoltaic string corresponding to the first DC / DC branch is greater than 30V to 55V helps to clearly distinguish whether the first DC / DC branch is performing a step-down operation, thereby enabling more accurate and automatic detection of the DC / DC branch that follows the voltage change of the first DC / DC branch, and determining whether the DC / DC branch whose input voltage has an absolute value difference with the input voltage of the first DC / DC branch is between 5V and 20V is the third DC / DC branch, thereby determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string.

[0082] By automatically detecting and traversing all the second DC / DC branches in sequence, and determining the DC / DC branch where the absolute value of the difference between the current input voltage and the first preset voltage is less than the second preset value as the third DC / DC branch, there is no need for installation engineers to manually divide and record the connection relationship between the photovoltaic panels and the photovoltaic inverter when installing the photovoltaic panels and the photovoltaic inverter, which saves labor costs and improves the reliability of the parallel detection results.

[0083] 6 , which is a flowchart of a method for determining a second DC / DC branch from the remaining DC / DC branches according to an embodiment of the present application, including steps S210 to S220 . Specifically,

[0084] Step S210: detecting the input voltage of the first DC / DC branch;

[0085] Step S220: Detecting the input voltages of the other DC / DC branches except the first DC / DC branch. If the absolute value of the difference between the input voltage of any DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value, determining that the current DC / DC branch is the second DC / DC branch.

[0086] In some embodiments of the present application, a method for determining a second DC / DC branch from the remaining DC / DC branches includes detecting the input voltage of the first DC / DC branch, detecting the input voltages of multiple DC / DC branches other than the first DC / DC branch, determining the voltage difference between the input voltage of the first DC / DC branch and the input voltages of multiple DC / DC branches other than the first DC / DC branch, and determining that the current DC / DC branch is the second DC / DC branch if the absolute value of the difference between the input voltage of any DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value. Since, in the embodiments of the present application, the first preset value ranges from 5V to 20V, the sampling error of the input voltage of the second DC / DC branch is ensured to be as small as possible, thereby improving the reliability of the parallel detection result. Therefore, it can be preliminarily determined that the first DC / DC branch and the second DC / DC branch may be connected in parallel to the same photovoltaic string, or that the first DC / DC branch and the second DC / DC branch are respectively connected to two photovoltaic strings with similar open-circuit voltages.

[0087] 7 , which is a flowchart of a method for determining whether an input voltage of a DC / DC branch is faulty according to an embodiment of the present application, including steps S100 to S120 . Specifically,

[0088] Step S100: detecting input voltages of multiple DC / DC branches;

[0089] Step S110: determining whether the input voltage of the DC / DC branch is less than a fourth preset value, where the fourth preset value represents a startup voltage of the DC / DC branch;

[0090] Step S120: If the input voltage of the DC / DC branch is less than a fourth preset value, a fault reminder is issued.

[0091] In some embodiments of the present application, a method for determining whether a fault exists in the input voltage of a DC / DC branch includes, before starting the photovoltaic inverter, first detecting the input voltages of a plurality of DC / DC branches, and determining whether the input voltage of the DC / DC branch is less than a fourth preset value, wherein the fourth preset value represents the startup voltage of the DC / DC branch. When the input voltage of the DC / DC branch is less than the fourth preset value, a fault reminder is issued to warn that the current DC / DC branch does not meet the startup conditions. By first determining the voltages of a plurality of DC / DC branches before starting the photovoltaic inverter, it is ensured that the input voltage of each DC / DC branch meets its own startup voltage, thereby effectively avoiding damage to the photovoltaic inverter, thereby implementing measures such as overload protection and short-circuit protection for electrical energy, and ensuring the safe operation of the photovoltaic power generation system.

[0092] Referring to Figure 8, Figure 8 is a structural diagram of a parallel detection device 1000 provided in an embodiment of the present application, including a processor 1001, which can be implemented using a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, etc., for executing relevant programs to implement a parallel detection method for a DC / DC branch provided in an embodiment of the present application; a memory 1002, which can be implemented in the form of a read-only memory 1002 (Read Only Memory, ROM), a static storage device, a dynamic storage device, or a random access memory 1002 (Random Access Memory, RAM). The memory 1002 can store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 1002, and the processor 1001 calls and executes the method of the embodiments of this application; the input / output interface 1003 is used to realize information input and output; the communication interface 1004 is used to realize communication interaction between this device and other devices, and communication can be realized through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.); the bus transmits information between the various components of the device (such as the processor 1001, memory 1002, input / output interface 1003 and communication interface 1004); wherein the processor 1001, memory 1002, input / output interface 1003 and communication interface 1004 realize communication connection with each other within the device through the bus.

[0093] The embodiments of the present application also provide a photovoltaic inverter, which includes a DC / DC branch and the parallel detection device described in the above embodiments, wherein the DC / DC branch is used to connect photovoltaic strings, and the parallel detection device is used to detect the input voltage of the DC / DC branch. A photovoltaic inverter is a power adjustment device composed of semiconductor devices, which is mainly used to convert direct current power into alternating current. In addition, the photovoltaic inverter also has the function of maximizing the performance of solar cells and the system fault protection function. The photovoltaic inverter can isolate and protect the electrical energy stored in the photovoltaic strings to prevent the electrical energy from causing harm to the human body and equipment. At the same time, the photovoltaic inverter can also take measures such as overload protection and short-circuit protection for the electrical energy to ensure the safe operation of the photovoltaic power generation system.

[0094] The photovoltaic inverter provided by the embodiment of the present application includes a parallel detection device, which is used to detect the connection relationship of the DC / DC branch on the input side of the photovoltaic inverter. The DC / DC branch parallel detection method provided by the embodiment of the present application includes automatically detecting and screening multiple DC / DC branches according to the input voltage, selecting a first DC / DC branch, and selecting a DC / DC branch from the remaining DC / DC branches whose absolute value of the difference between the input voltage and the voltage of the first DC / DC branch is less than a first preset value as the second DC / DC branch, then reducing the input voltage of the first DC / DC branch to determine from the second DC / DC branch that the input voltage follows the change of the first DC / DC branch and the absolute value of the difference between the input voltage of the first DC / DC branch and the input voltage of the first DC / DC branch is less than a second preset value as the third DC / DC branch, thereby determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string, turning on the first DC / DC branch, and controlling the third DC / DC branch to follow the third DC / DC branch for voltage output.

[0095] After determining that the first DC / DC branch and the third DC / DC branch are connected in parallel, the connection relationship of the remaining DC / DC branches in the second DC / DC branch, excluding the third DC / DC branch, is further determined. Specifically, a DC / DC branch excluding the third DC / DC branch is randomly selected from the second DC / DC branch as the fourth DC / DC branch, and a DC / DC branch is randomly selected from the fourth DC / DC branch as the fifth DC / DC branch. The fifth DC / DC branch is enabled, and the input voltage of the fifth DC / DC branch is gradually reduced to a second preset voltage, wherein the absolute value of the difference between the second preset voltage and the open-circuit voltage of the corresponding photovoltaic string is greater than the third preset value. A DC / DC branch is determined from the remaining DC / DC branches of the fourth DC / DC branch, and the DC / DC branch whose voltage follows the change of the fifth DC / DC branch and whose absolute value of the difference between the input voltage of the fifth DC / DC branch and the input voltage of the fifth DC / DC branch is less than the second preset value is determined as the sixth DC / DC branch. The fifth DC / DC branch and the sixth DC / DC branch are then connected in parallel to the same photovoltaic string. The fifth DC / DC branch is turned on, and the sixth DC / DC branch is controlled to follow the fifth DC / DC branch in outputting voltage. The parallel detection method provided in the embodiments of the present application eliminates the need for installation engineers to manually divide and record the connection relationship between the photovoltaic panels and the photovoltaic inverter when installing the photovoltaic panels and the photovoltaic inverter, thereby saving labor costs and improving the reliability of the parallel detection results.

[0096] The DC / DC branch on the input side of the photovoltaic inverter accurately determines the connection relationship between different DC / DC branches through the above-mentioned DC / DC branch parallel detection method of this application, thereby accurately controlling the startup of each DC / DC branch, so that the photovoltaic inverter converts DC power into AC power for household or industrial use.

[0097] Those skilled in the art will appreciate that all or some of the steps and systems in the method disclosed above can be implemented as software, firmware, hardware, and appropriate combinations thereof. Some physical components or all physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, and the computer-readable medium can include a computer-readable storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer-readable storage medium is included in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data) and is volatile and non-volatile, removable, and non-removable. Computer-readable storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory, or other memory technology, CD-ROM, digital versatile disks (DVD), or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, as is well known to those skilled in the art, communication media typically embodies computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0098] The above is a specific description of some implementations of the present application, but the present application is not limited to the above-mentioned implementation methods. Technical personnel familiar with the art can also make various equivalent modifications or substitutions without violating the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present application.

Claims

1. A parallel detection method for DC / DC branches, applied to a photovoltaic inverter, wherein the photovoltaic inverter includes a processor and a plurality of DC / DC branches connected thereto, the input end of the DC / DC branch is connected to a photovoltaic string, and the method executed by the processor includes: Before the photovoltaic inverter is started, detecting input voltages of a plurality of DC / DC branches; Selecting a first DC / DC branch from a plurality of DC / DC branches, and determining a second DC / DC branch from the remaining DC / DC branches, wherein the second DC / DC branch satisfies that an absolute value of a difference between an input voltage of the second DC / DC branch and an input voltage of the first DC / DC branch is less than a first preset value; The first DC / DC branch is turned on to reduce the input voltage of the first DC / DC branch, and a third DC / DC branch is determined from the second DC / DC branch, where the third DC / DC branch satisfies that the absolute value of the difference between the input voltage of the third DC / DC branch and the input voltage of the first DC / DC branch is less than a second preset value; Determining that the first DC / DC branch and the third DC / DC branch are connected in parallel to the same photovoltaic string; as well as The third DC / DC branch is controlled to follow the first DC / DC branch to output voltage.

2. The parallel detection method of DC / DC branches according to claim 1, further comprising: Determine a fourth DC / DC branch from the second DC / DC branch, the fourth DC / DC branch being other DC / DC branches in the second DC / DC branch except the third DC / DC branch; Select a fifth DC / DC branch from the fourth DC / DC branch, turn on the fifth DC / DC branch to reduce the input voltage of the fifth DC / DC branch, and determine a sixth DC / DC branch from the remaining DC / DC branches of the fourth DC / DC branch, wherein the sixth DC / DC branch satisfies that the absolute value of the difference between the input voltage of the sixth DC / DC branch and the input voltage of the fifth DC / DC branch is less than the second preset value; Determining that the fifth DC / DC branch and the sixth DC / DC branch are connected in parallel to the same photovoltaic string; as well as The sixth DC / DC branch is controlled to follow the fifth DC / DC branch to output voltage.

3. The parallel detection method of DC / DC branches according to claim 1 or 2, wherein: The step of starting the first DC / DC branch to reduce the input voltage of the first DC / DC branch and determining a third DC / DC branch from the second DC / DC branch includes: Turning on the first DC / DC branch and detecting an input voltage of the first DC / DC branch; When the input voltage of the first DC / DC branch drops to a first preset voltage, detecting the input voltage of the second DC / DC branch; and All the second DC / DC branches are traversed, and if the absolute value of the difference between the input voltage of any second DC / DC branch and the first preset voltage is less than the second preset value, it is determined that the current second DC / DC branch is the third DC / DC branch.

4. The parallel detection method of DC / DC branches according to claim 3, wherein: An absolute value of a difference between the first preset voltage and an open-circuit voltage of a photovoltaic string corresponding to the first DC / DC branch is greater than a third preset value.

5. The parallel detection method of DC / DC branches according to any one of claims 1 to 4, wherein: Determining the second DC / DC branch from the remaining DC / DC branches includes: detecting an input voltage of the first DC / DC branch; and Detect input voltages of other DC / DC branches except the first DC / DC branch, and if the absolute value of the difference between the input voltage of any DC / DC branch and the input voltage of the first DC / DC branch is less than a first preset value, determine that the current DC / DC branch is the second DC / DC branch.

6. The parallel detection method of DC / DC branches according to any one of claims 1 to 5, after detecting the input voltages of the plurality of DC / DC branches, further comprising: Determining whether the input voltage of the DC / DC branch is less than a fourth preset value, where the fourth preset value represents a startup voltage of the DC / DC branch; as well as If the input voltage of the DC / DC branch is less than the fourth preset value, a fault reminder is issued.

7. The parallel detection method of DC / DC branches according to any one of claims 1 to 6, wherein: The second preset value ranges from 5V to 20V.

8. A parallel detection device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the method according to any one of claims 1 to 7 when executing the computer program.

9. A photovoltaic inverter, comprising a DC / DC branch and the parallel detection device according to claim 8, wherein the DC / DC branch is used to connect photovoltaic strings, and the parallel detection device is used to detect the input voltage of the DC / DC branch.

10. A computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions are used to execute the method according to any one of claims 1 to 7.

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