CN115308549A - Arc detection method, electronic device and inverter - Google Patents
Arc detection method, electronic device and inverter Download PDFInfo
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- CN115308549A CN115308549A CN202210980696.3A CN202210980696A CN115308549A CN 115308549 A CN115308549 A CN 115308549A CN 202210980696 A CN202210980696 A CN 202210980696A CN 115308549 A CN115308549 A CN 115308549A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/54—Testing for continuity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/72—Testing of electric windings
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
The invention discloses an arc detection method, electronic equipment and an inverter, wherein the method comprises the following steps: judging whether the output voltage of a photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system; stopping arc detection if the output voltage of the photovoltaic string of the photovoltaic system is adjusted; when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string; according to the arc detection result is determined according to the arc characteristic value, the problem that arc detection is inaccurate due to the fact that an arc detection function is started during IV scanning is solved, the accuracy of arc detection is improved during IV scanning through the technical scheme, and then protection of a photovoltaic system on the arc is improved.
Description
Technical Field
The invention relates to the technical field of arc detection, in particular to an arc detection method, electronic equipment and an inverter.
Background
With the increasing use amount of photovoltaic energy in power system scenes, the frequency of fire accidents caused by direct current arcs is increased. Electric arcs are gas discharge phenomena, and once fault electric arcs occur in a photovoltaic system, serious safety accidents can be caused if effective protection is not adopted. Therefore, in practical application, by configuring the direct current arc detection device, the time domain and frequency domain characteristic signals are extracted to perform analysis processing, and whether the arc occurs is further judged, so that corresponding protection is performed. Meanwhile, an IV scanning technology is usually adopted for testing the photovoltaic module, current and voltage data in the operation process of the photovoltaic module are obtained through the IV scanning technology, and then the health state of the photovoltaic module is analyzed according to the current and voltage data.
At present, when an arc detection function is started during the IV scanning period, if sudden changes of voltage and current occur during the IV scanning period, interference is generated on time domain and frequency domain characteristics of arc detection, and the arc detection is inaccurate.
Disclosure of Invention
The embodiment of the application provides an arc detection method, electronic equipment and an inverter, and aims to solve the problem that arc detection is inaccurate when an arc detection function is started during IV scanning.
The embodiment of the application provides an arc detection method, which comprises the following steps:
judging whether the output voltage of a photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system;
stopping arc detection if the output voltage of the photovoltaic string of the photovoltaic system is adjusted;
when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string;
and determining an arc detection result according to the arc characteristic value.
Optionally, during the IV scan of the photovoltaic system, the step of determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted includes:
acquiring the output voltage of the photovoltaic string during the IV scanning executed by an IV scanning device of the photovoltaic system;
judging whether the output voltage of the photovoltaic string reaches a preset voltage or not;
and if the output voltage of the photovoltaic group string does not reach the preset voltage, determining that the output voltage of the photovoltaic group string needs to be adjusted.
Optionally, the step of stopping the arc detection when the output voltage of the photovoltaic string of the photovoltaic system is adjusted includes:
and if the output voltage of the photovoltaic group string of the photovoltaic system is adjusted, sending a voltage adjusting signal to an arc detection device of the photovoltaic system so as to control the arc detection device to stop arc detection.
Optionally, when the output current of the photovoltaic string satisfies a preset condition, the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string includes:
acquiring output current corresponding to the output voltage of each photovoltaic string within a preset time length for stopping the arc detection, wherein the preset time length is less than the voltage adjustment period of the photovoltaic strings;
judging whether the output current is in a preset current range or not;
and if so, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string.
Optionally, when the output current of the photovoltaic string satisfies a preset condition, the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string includes:
and after a preset time length, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string, wherein the preset time length is less than the voltage regulation period of the photovoltaic string.
Optionally, a difference between the photovoltaic string voltage adjustment period and the preset time period is an arc detection time period during which the output voltage of the photovoltaic string is adjusted once during the IV scanning period.
Optionally, the method further comprises:
detecting whether the IV scan is performed;
and if so, executing the step of judging whether the output voltage of the photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system.
Optionally, after the step of determining the arc detection result according to the arc characteristic value, the method further includes:
and when the arc detection result indicates that an arc fault occurs, controlling the inverter to be switched off.
Optionally, after the step of determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted during the IV scan of the photovoltaic system, the method includes:
if the output voltage of the photovoltaic string does not need to be adjusted, determining a scanning sample set of the photovoltaic string according to the output voltage of the photovoltaic string, the output current of the photovoltaic string and the open-circuit voltage of the photovoltaic string;
an IV scan curve is generated from the scan sample set.
Optionally, the determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string comprises:
performing fast Fourier analysis on the output voltage of the photovoltaic string, the output current and the open-circuit voltage of the photovoltaic string to obtain an analysis result;
acquiring arc characteristics, wherein the arc characteristics comprise at least one of a mean value, a root mean square value, a variance and a kurtosis;
and calculating the arc characteristic value corresponding to the arc characteristic according to the characteristic calculation mode of the arc characteristic based on the analysis result.
In addition, to achieve the above object, the present invention also provides an electronic device including: a memory, a processor and an arc detection program stored on the memory and executable on the processor, the arc detection program when executed by the processor implementing the steps of the arc detection method described above.
In addition, in order to achieve the above object, the present invention further provides an inverter, wherein the inverter comprises an arc detection device, an IV scanning device and an electronic device, and the arc detection device and the IV scanning device are connected in communication.
Optionally, the arc detection means and the IV scanning means are provided integrally.
According to the technical scheme of the arc detection method, the electronic device and the inverter, whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted or not is judged during the IV scanning period of the photovoltaic system, if yes, arc detection is stopped, and when the output current of the photovoltaic string meets the preset condition, the arc characteristic value is determined according to the output voltage of the photovoltaic string and the output current of the photovoltaic string, and then the arc detection result is determined according to the arc characteristic value. Whether the IV scanning device works or not is judged by detecting whether the output voltage of the photovoltaic group string of the photovoltaic system occurs or not during the IV scanning, when the IV scanning device works, the arc detection function is shielded, and the arc fault is normally detected and identified after the output current of the photovoltaic group string of the photovoltaic system is stably tracked and adjusted, so that the problem of inaccurate arc detection caused by the interference of the output voltage and the output current mutation of the photovoltaic group string on the arc detection during the IV scanning is solved, the accuracy of the arc detection is improved, and the protection of the photovoltaic system on the arc is further improved.
Drawings
Fig. 1 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an inverter according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an electronic device according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of a first embodiment of the arc detection method of the present invention;
FIG. 5 is a schematic flow chart illustrating arc fault detection during an IV scan according to the present invention;
FIG. 6 is a schematic flow chart illustrating an arc detection function performed according to the IV scan voltage adjustment signal according to the present invention;
fig. 7 is a schematic diagram illustrating a relationship between a photovoltaic string voltage adjustment period and a preset time period according to the present invention.
The objects, features, and advantages of the present application are further described in connection with the embodiments, with reference to the accompanying drawings, which are a single embodiment and are not intended to be a complete description of the invention.
Detailed Description
The method and the device aim to solve the problem that arc detection is inaccurate due to interference of sudden change of the output voltage and the output current of the photovoltaic string on the arc detection during the IV scanning. The application provides an arc detection method, which is characterized in that whether the output voltage of a photovoltaic group string of a photovoltaic system is adjusted or not is judged during the IV scanning period of the photovoltaic system, if the output voltage of the photovoltaic group string of the photovoltaic system is adjusted, arc detection is stopped, and when the output current of the photovoltaic group string meets a preset condition, an arc characteristic value is determined according to the output voltage of the photovoltaic group string and the output current of the photovoltaic group string, and then an arc detection result is determined according to the arc characteristic value. Whether the IV scanning device works or not is judged by detecting whether the output voltage of the photovoltaic group string of the photovoltaic system occurs or not during the IV scanning, when the IV scanning device works, the arc detection function is shielded, and the arc fault is normally detected and identified after the output current of the photovoltaic group string of the photovoltaic system is stably tracked and adjusted, so that the accuracy of arc detection is improved, and the protection of the photovoltaic system on the arc is further improved.
In order to better understand the above technical solution, exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As shown in fig. 1, fig. 1 is a schematic structural diagram of a photovoltaic system according to an embodiment of the present invention. The photovoltaic system at least comprises one photovoltaic string (PV), and each photovoltaic string at least comprises one photovoltaic module, an inverter, a power grid and a load. Wherein the inverter is connected to the grid and to the optional load. Optionally, when each photovoltaic string includes a plurality of photovoltaic modules, the photovoltaic modules are connected in series.
Optionally, a combiner box may be further included between the photovoltaic string and the inverter, and the combiner box connects the m-way photovoltaic strings. The combiner box is used for acquiring the open-circuit voltage of the photovoltaic string and sending the open-circuit voltage of the photovoltaic string to the electronic equipment; the inverter is used for determining a scanning initial voltage according to the open-circuit voltage of the photovoltaic string, and controlling the output voltage of the photovoltaic string to gradually change from the scanning initial voltage to a lower limit value of a preset voltage based on a first preset step length.
Optionally, the combiner box is further configured to obtain an output current of each photovoltaic string at the output voltage of each photovoltaic string, and send the output voltage of each photovoltaic string and the output current of each photovoltaic string to the electronic device. Optionally, the electronic device is configured to determine the scan sample set for each photovoltaic string based on an open circuit voltage of the photovoltaic string, an output voltage of the photovoltaic string, and an output current of the photovoltaic string.
Those skilled in the art will appreciate that the configuration of the photovoltaic system shown in fig. 1 is not intended to be limiting of the photovoltaic system, and may include more or fewer components than shown, or some components may be combined, or a different arrangement of components.
As shown in fig. 2, fig. 2 is a schematic structural diagram of the inverter of the present application. An arc detection device and an IV scanning device are arranged in the inverter and are in communication connection. Optionally, an electronic device capable of storing programs, variables and supporting information interaction is further included in the inverter. The electronic device is connected with the arc detection device and the IV scanning device respectively. Optionally, the arc detection device and the IV scanning device may also be integrated in the same device, which is connected to the electronic device. Alternatively, the electronic device may be provided integrally with the inverter.
Optionally, the inverter is further configured to boost regulate the dc bus voltage such that current flows from the inverter to the string of photovoltaic strings in a first direction, and to buck regulate the dc bus voltage until current flows from the photovoltaic module to the inverter in a second direction, the second direction being opposite to the first direction; the combiner box is also used for determining the voltage of the direct current bus at the moment when the current flows to the reverse side as the open-circuit voltage of the photovoltaic string.
Optionally, after the string output voltage value reaches the lower limit value of the preset voltage, the inverter and/or the combiner box starts a direct-current short-circuit mode; the combiner box collects short-circuit current flowing through the photovoltaic string in a direct-current short-circuit mode and sends the short-circuit current to the electronic equipment; the electronics add a short circuit current value to the scan sample set.
Optionally, the electronic device is further configured to, after obtaining the scanning sample set of each photovoltaic string, perform data fitting according to the scanning sample set, and determine an IV scanning curve of the photovoltaic string, where a scanning starting point of the IV scanning curve of the photovoltaic string is an open-circuit voltage of the corresponding photovoltaic string.
Those skilled in the art will appreciate that the configuration of the inverter shown in fig. 2 does not constitute a limitation of the inverter, and may include more or fewer components than shown, or some components in combination, or a different arrangement of components.
As shown in fig. 3, fig. 3 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
As shown in fig. 3, the electronic device may include: a processor 1001, e.g. a CPU, a memory 1005, a user interface 1003, a network interface 1004, a communication bus 1002. The communication bus 1002 is used to implement connection communication among these components. The user interface 1003 may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wired interface, a wireless interface (e.g., WI-FI interface). The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001 described previously.
Those skilled in the art will appreciate that the configuration of the electronic device shown in fig. 3 does not constitute a limitation of the electronic device and may include more or fewer components than shown, or some components may be combined, or a different arrangement of components.
As shown in fig. 3, a memory 1005, which is a storage medium, may include therein an operating system, a network communication module, a user interface module, and an arc detection program. Among other things, the operating system is a program that manages and controls the hardware and software resources of the electronic device, the operation of the arc detection program, and other software or programs.
In the electronic device shown in fig. 3, the user interface 1003 is mainly used for connecting a terminal and communicating data with the terminal; the network interface 1004 is mainly used for a background server and is in data communication with the background server; processor 1001 may be used to invoke an arc detection program stored in memory 1005.
In this embodiment, the electronic device includes: a memory 1005, a processor 1001, and an arc detection program stored on the memory and executable on the processor, wherein:
when the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are performed:
judging whether the output voltage of a photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system;
stopping arc detection if the output voltage of the photovoltaic string of the photovoltaic system is adjusted;
when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string;
and determining an arc detection result according to the arc characteristic value.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
acquiring the output voltage of the photovoltaic string during the IV scanning executed by an IV scanning device of the photovoltaic system;
judging whether the output voltage of the photovoltaic string reaches a preset voltage or not;
and if the output voltage of the photovoltaic group string does not reach the preset voltage, determining that the output voltage of the photovoltaic group string needs to be adjusted.
And if the output voltage of the photovoltaic string of the photovoltaic system is adjusted, sending a voltage adjusting signal to an arc detection device of the photovoltaic system so as to control the arc detection device to stop arc detection.
When the processor 1001 invokes the arc detection program stored in the memory 1005, the following operations are also performed:
acquiring output current corresponding to the output voltage of each photovoltaic string within a preset time length for stopping the arc detection, wherein the preset time length is less than the voltage regulation period of the photovoltaic strings;
judging whether the output current is in a preset current range or not;
and if so, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
and after a preset time length, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string, wherein the preset time length is less than the voltage regulation period of the photovoltaic string.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
and the difference value between the photovoltaic group string voltage adjustment period and the preset time length is the arc detection time length of the photovoltaic group string output voltage adjustment once in the IV scanning period.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
detecting whether the IV scan is performed;
and if so, executing the step of judging whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
and when the arc detection result indicates that an arc fault occurs, controlling the inverter to be switched off.
When the processor 1001 calls the arc detection program stored in the memory 1005, the following operations are also performed:
if the output voltage of the photovoltaic string does not need to be adjusted, determining a scanning sample set of the photovoltaic string according to the output voltage of the photovoltaic string, the output current of the photovoltaic string and the open-circuit voltage of the photovoltaic string;
an IV scan curve is generated from the scan sample set.
When the processor 1001 invokes the arc detection program stored in the memory 1005, the following operations are also performed:
performing fast Fourier analysis on the output voltage of the photovoltaic string, the output current and the open-circuit voltage of the photovoltaic string to obtain an analysis result;
acquiring arc characteristics, wherein the arc characteristics comprise at least one of a mean value, a root mean square value, a variance and a kurtosis;
and calculating the arc characteristic value corresponding to the arc characteristic according to the characteristic calculation mode of the arc characteristic based on the analysis result.
The technical solution of the present application will be developed by way of examples.
A first embodiment.
As shown in fig. 4, in a first embodiment of the present application, an arc detection method of the present application is applied to an electronic device of an inverter, and includes the steps of:
step S110, during the IV scanning period of the photovoltaic system, determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted.
In this embodiment, during the IV scan of the photovoltaic system, the arc detection function is executed or the arc detection is stopped for a preset duration according to whether the output voltage of the photovoltaic string is adjusted. During the IV scanning period, if the group string voltage is adjusted according to the preset step length, the arc detection function is stopped for the preset time length, after the group string current is stabilized, the arc detection function is started for normal detection, and the influence of voltage and current mutation on time domain and frequency domain characteristic signals of arc detection is prevented. If the inverter does not perform the IV scan, the arc detection function is performed normally.
Wherein IV data for the photovoltaic module is generated during an IV scan of the photovoltaic system; the IV data refer to current-voltage data of the photovoltaic module in the operation process, and the IV data can directly reflect the health state of the photovoltaic module, so the IV scanning function for acquiring the IV data of the photovoltaic module is an important technology for evaluating the power generation capacity and diagnosing faults of the photovoltaic system. The specific process is as follows: the inverter dynamically changes the load of the photovoltaic module, scanning is started from the open-circuit voltage (namely the maximum voltage) of the photovoltaic module until the voltage of the photovoltaic module approaches zero voltage, a group of two-dimensional arrays of different voltages and currents is obtained, an IV curve is constructed according to discrete data in all the two-dimensional arrays, and characteristic identification is carried out through the IV curve to judge whether the photovoltaic module is shielded, damaged or subjected to abnormal conditions such as hot spots.
In this embodiment, during the IV scan of the photovoltaic system, in the voltage adjustment period of each photovoltaic group string, the output voltage of each photovoltaic group string of the photovoltaic system is adjusted according to the preset step length, that is, the output voltage of each photovoltaic group string of the photovoltaic system is gradually adjusted from the open-circuit voltage to the preset voltage according to the preset step length. Because a plurality of paths of photovoltaic string exist in the photovoltaic system, the open-circuit voltage of each path of photovoltaic string can be obtained; determining the maximum value of the open-circuit voltage in each open-circuit voltage, and determining an initial scanning voltage according to the maximum value of the open-circuit voltage, wherein the initial scanning voltage is greater than or equal to the maximum value of the open-circuit voltage, so that the output voltage of a photovoltaic group string of the photovoltaic system is gradually adjusted from the initial scanning voltage to a preset voltage according to a preset step length.
Optionally, during the IV scan of the photovoltaic system, the step of determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted includes:
step S111, acquiring output voltage of the photovoltaic group string during the IV scanning executed by an IV scanning device of the photovoltaic system;
step S112, judging whether the output voltage of the photovoltaic string reaches a preset voltage or not;
step S113, if the output voltage of the photovoltaic string does not reach the preset voltage, determining that the output voltage of the photovoltaic string needs to be adjusted.
In this embodiment, the IV scan is a function performed by the electronic device controlling the IV scanning apparatus of the photovoltaic system. During the IV scan performed by the IV scan apparatus of the photovoltaic system, the output voltage of the photovoltaic string is gradually adjusted from the open-circuit voltage to the preset voltage. The preset voltage may be set according to an actual condition, for example, the preset voltage may be zero voltage; all the voltages between the open-circuit voltage and the zero voltage can also be divided into a plurality of voltage intervals according to actual conditions, and the preset voltage can be a voltage lower limit value of a certain voltage interval.
Optionally, during the IV scanning performed by the IV scanning apparatus of the photovoltaic system, the electronic device may obtain the output voltage of the photovoltaic string in real time, and determine the relationship between the output voltage of the photovoltaic string and the preset voltage. Wherein, the relation between the output voltage of judging this photovoltaic group cluster and presetting the voltage can be: when the difference value between the output voltage and the preset voltage is greater than 0, the output voltage does not reach the preset voltage; and when the difference value between the output voltage and the preset voltage is less than 0, the output voltage reaches the preset voltage.
Optionally, when the output voltage of the photovoltaic string does not reach the preset voltage, it is determined that the output voltage of the photovoltaic string still needs to be adjusted, and at this time, the output voltage of the photovoltaic string is continuously adjusted based on the preset step length. Optionally, when the output voltage of the photovoltaic string reaches the preset voltage, it is determined that the output voltage of the photovoltaic string does not need to be adjusted, and a current and voltage sudden change condition does not exist at this time, and a normal arc detection function can be executed at this time.
Optionally, a photovoltaic string voltage adjustment period may be further set, and voltage adjustment is performed in each photovoltaic string voltage adjustment period. At each voltage adjustment, timing is started, for example, the initial timing is when the open circuit voltage is scanned. And after the timing is finished, restarting a new photovoltaic group string voltage adjustment period, and adjusting the voltage downwards. Therefore, it may be that the arc detection is stopped at each photovoltaic string voltage adjustment period, i.e. voltage adjustment start timing.
According to the technical scheme, during the IV scanning period executed by the IV scanning device of the photovoltaic system, the electronic equipment in the inverter acquires the output voltage of the photovoltaic group string, whether the output voltage of the photovoltaic group string reaches the preset voltage or not is judged, and when the output voltage of the photovoltaic group string does not reach the preset voltage, the technical scheme that the output voltage of the photovoltaic group string needs to be adjusted is determined, so that the voltage adjusting state of the photovoltaic group string is monitored in real time, and the IV scanning device can normally perform the IV scanning function.
Step S120, if the output voltage of the photovoltaic string of the photovoltaic system is adjusted, stopping the arc detection.
In this embodiment, arc detection may be performed simultaneously during the IV scan of the photovoltaic system, and when the output voltage of the photovoltaic string of the photovoltaic system is adjusted, sudden changes of the output voltage and the output current of the photovoltaic string may occur, and the sudden changes of the output voltage and the output current may cause an inaccurate arc detection result, so that the arc detection function needs to be stopped when the output voltage of the photovoltaic string of the photovoltaic system is adjusted. Optionally, the IV scan function may continue while the arc detection function is stopped.
Optionally, if the output voltage of the photovoltaic string of the photovoltaic system is adjusted, a voltage adjustment signal is sent to an arc detection device of the photovoltaic system to control the arc detection device to stop arc detection. Wherein, the IV scanning device and the arc detection device have a communication connection function. Optionally, the IV scanning device may synchronize the IV scan command and the voltage adjustment signal to the arc detection device when the output voltage of the photovoltaic string of the photovoltaic system is adjusted, so that the arc detection device stops the arc detection after receiving the voltage adjustment signal and the IV scan command. Optionally, when the output voltage of the photovoltaic string of the photovoltaic system is adjusted, the IV scanning device sends an IV scanning instruction and a voltage adjustment signal to the electronic device; after receiving the IV scanning instruction and the voltage adjustment signal sent by the IV scanning device, the electronic device generates an arc detection stop signal, and forwards the arc detection stop signal to the arc detection device, thereby controlling the arc detection device to stop arc detection.
According to the technical scheme, the arc detection function is stopped when the output voltage of the photovoltaic string of the photovoltaic system is detected to be adjusted, so that the phenomenon that the arc detection result is inaccurate due to sudden change of the output voltage and the output current of the photovoltaic string when the output voltage of the photovoltaic string of the photovoltaic system is adjusted is avoided.
Step S130, when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string.
In this embodiment, after stopping the arc detection function, it is further determined whether the output current of the photovoltaic string satisfies the preset condition, and the arc detection is resumed only when the output current of the photovoltaic string satisfies the preset condition. If the output current of the photovoltaic string does not meet the preset condition all the time, the arc detection can be resumed only when the preset condition is waited to be met. The output current of the photovoltaic string satisfies a preset condition, which means that the output current of the photovoltaic string is stable, that is, no sudden change occurs. If the output current of the photovoltaic string does not meet the preset condition, that is, the output current of the photovoltaic string is unstable, the situation that the output current changes suddenly in the process of adjusting the output voltage of the photovoltaic string is shown. The arc detection is mainly to extract time domain and frequency domain characteristic signals, namely arc characteristic values, from the IV data (namely the output voltage of the photovoltaic string and the output current of the photovoltaic string) generated in the IV scanning period, and then analyze and process the signals so as to judge whether the arc occurs.
Optionally, when the output current of the photovoltaic string satisfies a preset condition, the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string includes:
step S131, acquiring output current corresponding to the output voltage of each photovoltaic string within a preset time length for stopping the arc detection, wherein the preset time length is less than the voltage adjustment period of the photovoltaic strings;
step S132, judging whether the output current is in a preset current range;
and step S133, if yes, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string.
In this embodiment, specifically, refer to fig. 7, where the preset time period is a photovoltaic string current tracking adjustment time period, that is, a time period for performing current stability detection. The preset time length is less than the voltage adjustment period of the photovoltaic string, and the difference value between the voltage adjustment period of the photovoltaic string and the preset time length is the arc detection time length of once adjustment of the output voltage of the photovoltaic string in the IV scanning period. The preset time is determined by the speed of tracking and adjusting the current of the photovoltaic string stably after the output voltage of the photovoltaic string is adjusted, and the faster the current of the photovoltaic string is adjusted, the shorter the preset time is. Under the condition that the requirement of the total scanning duration of the IV scanning function is met, the arc identification capability of the arc detection function is stronger in the photovoltaic group string voltage adjustment period.
Optionally, after the arc detection is stopped, the output current corresponding to the output voltage of the photovoltaic string at each moment within the preset time period for stopping the arc detection may be obtained. If the output current of the photovoltaic string is within the preset current range at each moment within the preset time, it indicates that the output current of the photovoltaic string is stable, and then arc detection can be started, that is, the arc characteristic value is determined according to the output voltage of the photovoltaic string and the output current of the photovoltaic string. If the continuous output current of the photovoltaic string is not within the preset current range within the preset time, the output current of the photovoltaic string is unstable, and at the moment, arc detection cannot be started.
Wherein, the preset current range can be set according to actual conditions.
Optionally, the output currents corresponding to the output voltages of all the photovoltaic strings from the open-circuit voltage to the zero voltage may be determined, that is, the preset current range may be a current interval corresponding to the output current corresponding to the open-circuit voltage to the output current corresponding to the zero voltage, and then it is determined whether the output current corresponding to the output voltage of each photovoltaic string is within the preset current range. Optionally, after the output voltage between the open-circuit voltage and the zero voltage is divided into a plurality of interval voltages according to actual conditions, each interval voltage corresponds to an interval current, the interval current can be determined according to the interval voltage where the output voltage of the current photovoltaic string is located, the interval current is further determined as a preset current range, and whether the output current corresponding to the output voltage of each photovoltaic string is located in the preset current range is further determined.
Optionally, the average value of the output current may be calculated according to the output current corresponding to the output voltage of each photovoltaic string within the preset duration for stopping the arc detection, and it is determined whether the average value of the output current is within the preset current range, if so, the arc detection is performed, that is, the arc characteristic value is determined according to the output voltage and the output current of the photovoltaic string.
According to the technical scheme, whether the output current corresponding to the output voltage of each photovoltaic group string is in the preset current range or not is judged within the preset time for stopping the arc detection, and the arc detection is only carried out if the output current is in the preset current range, so that the arc detection error report caused by the sudden change of the current and the voltage is avoided, and the protection of the photovoltaic system on the arc is further improved. Meanwhile, the arc fault can be normally detected and identified during the IV scanning period by setting the preset time length and the photovoltaic group string voltage adjustment period, so that the arc starting missing detection during the IV scanning period is prevented.
Optionally, when the output current of the photovoltaic string satisfies a preset condition, the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string includes:
step S231, after a preset time period, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string, where the preset time period is less than a photovoltaic string voltage adjustment period.
In this embodiment, the preset time duration is less than the photovoltaic string voltage adjustment period, and the difference between the photovoltaic string voltage adjustment period and the preset time duration is the arc detection time duration of once adjusting the output voltage of the photovoltaic string during the IV scanning period. Optionally, after the preset time period, automatically determining that the output current is within the preset current range, and starting to perform arc detection, that is, after the preset time period, determining an arc characteristic value according to the output voltage and the output current of the photovoltaic string.
According to the technical scheme, the arc characteristic value is determined according to the output voltage and the output current of the photovoltaic string after the preset time, so that arc detection misinformation caused by current and voltage mutation is avoided, and the protection of the photovoltaic system on the arc is improved. Meanwhile, the arc fault can be normally detected and identified during the IV scanning period by setting the preset time length and the photovoltaic group string voltage adjustment period, so that the arc starting missing detection during the IV scanning period is prevented.
Optionally, the electronic device performs arc detection when the output current of the photovoltaic string satisfies a preset condition. In the process of arc detection, a built-in program of the arc detection device performs fast Fourier analysis on the acquired signals and extracts arc characteristics. The arc characteristic includes, but is not limited to, at least one of a mean value, a root mean square value, a variance, and a kurtosis, for example, the arc characteristic may be only the mean value, or the mean value and the peak value, or the mean value, the root mean square value, the variance, and the kurtosis. And each arc characteristic has a corresponding characteristic calculation mode, and the corresponding characteristic calculation mode can be set for each arc characteristic according to actual conditions. Specifically, the specific process of arc detection may be: performing fast Fourier analysis on the output voltage of the photovoltaic string, the output current and the open-circuit voltage of the photovoltaic string to obtain an analysis result; acquiring arc characteristics, wherein the arc characteristics comprise at least one of a mean value, a root mean square value, a variance and a kurtosis; and calculating to obtain an arc characteristic value corresponding to the arc characteristic according to the characteristic calculation mode of the arc characteristic based on the analysis result. Because the output voltage, the output current and the open-circuit voltage of the photovoltaic string are analyzed and the corresponding arc characteristic values are extracted in the mode, the final arc detection result is more accurate.
And step S140, determining an arc detection result according to the arc characteristic value.
In the present embodiment, after the arc characteristic value is determined according to the above manner, the arc detection result may be further determined according to the arc characteristic value. Wherein the arc detection result comprises the occurrence of arc fault and the non-occurrence of arc fault. Alternatively, the arc detection result may also be the corresponding output voltage and output current within a preset period range of the occurrence of the arc.
Optionally, the arc characteristic value may be compared with a preset threshold, and if the arc characteristic value is greater than the preset threshold, it is determined that an arc occurs; and if the arc characteristic value is less than or equal to the preset threshold value, judging that no arc occurs. Optionally, a corresponding preset threshold may be set for each arc characteristic value according to an actual situation, when there are a plurality of arc characteristic values, it is determined that an arc occurs only when all arc characteristic values are greater than the corresponding preset threshold, otherwise, no arc occurs. Optionally, a corresponding weight and a corresponding preset threshold may be set for each arc characteristic value, when there are multiple arc characteristic values, the arc characteristic value greater than the corresponding preset threshold is extracted, and a final calculation result is calculated by combining the corresponding weight, and when the calculation result does not satisfy a preset condition, it is determined that an arc occurs, where the preset condition may be set according to an actual situation. The determination of the arc detection result according to the arc characteristic value is not limited to the above manner, and the arc detection result may also be determined according to a specific application scenario and according to a specific rule set according to a specific requirement.
Optionally, when the arc fault occurs as a result of the arc detection, the inverter is controlled to be turned off. The inverter is stopped in a fault mode, an arc fault is reported, and line inspection is carried out by maintenance personnel so as to avoid major safety accidents.
According to the technical scheme, whether the output voltage of the photovoltaic group string of the photovoltaic system is adjusted or not is judged during the IV scanning period of the photovoltaic system, if the output voltage of the photovoltaic group string of the photovoltaic system is adjusted, arc detection is stopped, when the output current of the photovoltaic group string meets a preset condition, an arc characteristic value is determined according to the output voltage of the photovoltaic group string and the output current of the photovoltaic group string, and then an arc detection result is determined according to the arc characteristic value. Whether the IV scanning device works or not is judged by detecting whether the output voltage of the photovoltaic group string of the photovoltaic system occurs or not during the IV scanning, when the IV scanning device works, the arc detection function is shielded, and the arc fault is normally detected and identified after the output current of the photovoltaic group string of the photovoltaic system is stably tracked and adjusted, so that the problem of inaccurate arc detection caused by the interference of the output voltage and the output current mutation of the photovoltaic group string on the arc detection during the IV scanning is solved, the accuracy of the arc detection is improved, and the protection of the photovoltaic system on the arc is further improved.
A second embodiment.
Based on the first embodiment, before step S110, in the second embodiment of the present application, the arc detection method of the present application includes the following steps:
step S310, detecting whether the IV scanning is executed;
if yes, executing step S110, and during the IV scanning period of the photovoltaic system, determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted;
step S120, if the output voltage of the photovoltaic string of the photovoltaic system is adjusted, stopping arc detection;
step S130, when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string;
and step S140, determining an arc detection result according to the arc characteristic value.
In the embodiment, during the grid connection of the inverter, the arc detection device takes the direct-current side alternating-current signal of the inverter in real time; if the inverter does not perform the IV scan function, the arc detection function is normally performed. If the inverter needs to execute an IV scanning function, determining an initial scanning voltage by using the open-circuit voltage, downwards adjusting the output voltage of the photovoltaic string according to a preset step length after the voltage adjustment period of the photovoltaic string, and simultaneously transmitting an IV scanning instruction and a voltage adjustment signal to an arc detection device by using an IV scanning device; and after the arc detection device receives the voltage adjustment signal, stopping arc detection for a preset time, and after the output current of the photovoltaic string is adjusted and stabilized, performing arc detection.
Alternatively, it may also be redetected whether the IV scan is performed when it is detected that no arc has occurred. Enabling normal IV scanning of all photovoltaic strings of the photovoltaic system and improving arc accuracy during IV scanning.
Specifically, referring to fig. 5, parameter initialization is performed first. Then, whether to execute IV scanning is detected;
if the IV scan is executed, the arc detection function is executed according to the IV scan voltage change signal. And judging whether an arc occurs, if so, indicating that an arc fault is detected, and if not, re-detecting whether to execute the IV scanning.
If the IV scan is not performed, the arc detection function is normally performed. And judging whether an arc occurs, if so, indicating that an arc fault is detected, and if not, re-detecting whether to execute the IV scanning.
Referring to fig. 6, fig. 6 is a schematic flow chart illustrating the arc detection function performed according to the IV scan voltage adjustment signal. Specifically, the process is as follows: an IV scan is performed first, with the initial voltage determined by the open circuit voltage. Then, when the voltage regulation period of the photovoltaic string is reached, voltage regulation is carried out according to a preset step length; then, stopping arc detection for a preset time length, and waiting for the current to be stable; then, when the current is stabilized, an arc detection function is performed. When the arc detection function is executed, returning to the step of executing voltage adjustment according to a preset step length when the voltage adjustment period of the photovoltaic string is reached; and finally, if the output voltage of the photovoltaic group string is smaller than the lower limit value of the preset voltage, ending the IV scanning.
According to the technical scheme, whether the IV scanning is executed or not is detected, and the arc detection function is executed according to the IV scanning voltage change signal when the IV scanning is executed, so that the problem of inaccurate arc detection caused by interference of the output voltage and the output current mutation of the photovoltaic string on the arc detection during the IV scanning is solved, the accuracy of the arc detection is improved, and the protection of the photovoltaic system on the arc is further improved.
A third embodiment.
After the first implementation step S110, in a third embodiment of the present application, the arc detection method of the present application includes the following steps:
step S110, judging whether the output voltage of a photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system;
step S410, if the output voltage of the photovoltaic string does not need to be adjusted, determining a scanning sample set of the photovoltaic string according to the output voltage of the photovoltaic string, the output current of the photovoltaic string and the open-circuit voltage of the photovoltaic string;
step S420, an IV scan curve is generated according to the scan sample set.
In this embodiment, when the output voltage of the photovoltaic system does not need to be adjusted, the scanning sample set of each photovoltaic group string is determined according to the open-circuit voltage of the photovoltaic group string, the output voltage of the photovoltaic group string, and the current of the photovoltaic group string, an IV scanning curve corresponding to each photovoltaic group string is drawn, and the IV scanning is ended. And then, the characteristic identification is carried out through the IV curve to judge whether the photovoltaic module is shielded, damaged or subjected to abnormal conditions such as hot spots.
According to the technical scheme, due to the adoption of the technical means for generating the IV scanning curve when the output voltage of the photovoltaic group string does not need to be adjusted, the abnormity judgment of the photovoltaic module can be carried out through the IV scanning curve, and therefore the safe maintenance of the photovoltaic system is realized.
While a logical order is shown in the flow chart, in some cases, the steps shown or described may be performed in an order different than presented herein.
Claims (13)
1. An arc detection method, comprising:
judging whether the output voltage of a photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system;
stopping arc detection if the output voltage of the photovoltaic string of the photovoltaic system is adjusted;
when the output current of the photovoltaic string meets a preset condition, determining an arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string;
and determining an arc detection result according to the arc characteristic value.
2. The arc detection method of claim 1, wherein the step of determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted during the IV scan of the photovoltaic system comprises:
acquiring the output voltage of the photovoltaic group string during the IV scanning of an IV scanning device of the photovoltaic system;
judging whether the output voltage of the photovoltaic string reaches a preset voltage or not;
and if the output voltage of the photovoltaic group string does not reach the preset voltage, determining that the output voltage of the photovoltaic group string needs to be adjusted.
3. The arc detection method of claim 1, wherein the step of stopping arc detection if the output voltage of the photovoltaic string of the photovoltaic system is adjusted comprises:
and if the output voltage of the photovoltaic group string of the photovoltaic system is adjusted, sending a voltage adjusting signal to an arc detection device of the photovoltaic system so as to control the arc detection device to stop arc detection.
4. The arc detection method according to claim 1, wherein the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string when the output current of the photovoltaic string satisfies a preset condition comprises:
acquiring output current corresponding to the output voltage of each photovoltaic string within a preset time length for stopping the arc detection, wherein the preset time length is less than the voltage regulation period of the photovoltaic strings;
judging whether the output current is in a preset current range or not;
and if so, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string.
5. The arc detection method of claim 1, wherein the step of determining the arc characteristic value according to the output voltage of the photovoltaic string and the output current of the photovoltaic string when the output current of the photovoltaic string satisfies a preset condition comprises:
and after a preset time length, determining the arc characteristic value according to the output voltage and the output current of the photovoltaic string, wherein the preset time length is less than the voltage regulation period of the photovoltaic string.
6. The arc detection method of claim 4 or 5, wherein the difference between the photovoltaic string voltage adjustment period and the preset duration is an arc detection duration during which the output voltage of the photovoltaic string is adjusted once during the IV scan.
7. The arc detection method of claim 1, further comprising:
detecting whether the IV scan is performed;
and if so, executing the step of judging whether the output voltage of the photovoltaic group string of the photovoltaic system is adjusted or not during the IV scanning period of the photovoltaic system.
8. The arc detection method of claim 1, wherein said step of determining an arc detection result based on said arc signature value is followed by the step of:
and when the arc detection result indicates that an arc fault occurs, controlling the inverter to be switched off.
9. The arc detection method of claim 1, wherein said step of determining whether the output voltage of the photovoltaic string of the photovoltaic system is adjusted during the IV scan of the photovoltaic system is followed by:
if the output voltage of the photovoltaic string does not need to be adjusted, determining a scanning sample set of the photovoltaic string according to the output voltage of the photovoltaic string, the output current of the photovoltaic string and the open-circuit voltage of the photovoltaic string;
an IV scan curve is generated from the scan sample set.
10. The arc detection method of claim 1, wherein said determining an arc signature from the output voltage of the string of photovoltaic strings and the output current of the string of photovoltaic strings comprises:
performing fast Fourier analysis on the output voltage of the photovoltaic string, the output current and the open-circuit voltage of the photovoltaic string to obtain an analysis result;
acquiring arc characteristics, wherein the arc characteristics comprise at least one of a mean value, a root mean square value, a variance and a kurtosis;
and calculating the arc characteristic value corresponding to the arc characteristic according to the characteristic calculation mode of the arc characteristic based on the analysis result.
11. An electronic device, characterized in that the electronic device comprises: memory, a processor and an arc detection program stored on the memory and executable on the processor, the arc detection program when executed by the processor implementing the steps of the arc detection method as claimed in any one of claims 1-10.
12. An inverter, characterized in that the inverter comprises an arc detection device, an IV scanning device and an electronic apparatus according to claim 11, the arc detection device and the IV scanning device being communicatively connected.
13. The inverter of claim 12, wherein the arc detection means and the IV scanning means are provided integrally.
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