Multi-path PV arc discharge detection device, arc discharge detection method and photovoltaic power generation system

Abstract

The embodiment of the invention discloses a multi-path PV arc discharge detection device, an arc discharge detection method and a photovoltaic power generation system. The multi-path PV arcing detection device comprises a current detection assembly which sleeves at least one pair of photovoltaic direct current cables and is used for detecting differential mode signals on the at least one pair of photovoltaic direct current cables; the at least one pair of photovoltaic direct-current cables are two photovoltaic direct-current cables which are connected with the same converter and do not belong to the same photovoltaic string, and comprise a first cable and a second cable; wherein the first cable is obtained by converging like-polarity output ends of n paths of photovoltaic strings; the second cable is formed by converging like-polarity output ends of m paths of photovoltaic strings; n and m are integers greater than or equal to 1; the first cable winds the current detection assembly by i circles in a first direction; the second cable winds the current detection assembly by j circles in a second direction; wherein i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of electric power technology, and relate to but are not limited to a multi-channel PV arc detection device, an arc detection method, and a photovoltaic power generation system. Background Art

[0002] With the development and widespread application of photovoltaic power generation technology, the technical requirements for photovoltaic system power generation are becoming higher and higher. The photovoltaic system is composed of solar photovoltaic panels, photovoltaic DC cables, inverters and other structures. The solar photovoltaic panels are exposed outdoors to collect solar energy and convert it into photoelectricity, thereby realizing photovoltaic power generation. However, photovoltaic cables are prone to DC arc faults, also known as arc faults, when they are aged, affected by the external environment (such as animals biting or sudden changes in the natural environment), or when photovoltaic energy suddenly changes.

[0003] DC arc is a gas discharge phenomenon near the cable, that is, the sparks generated by the current passing through the insulating medium such as air, and at the same time, a transient current is generated in the cable, which can easily damage the circuit components and cause system failure. Therefore, it is necessary to detect arc faults in photovoltaic power generation systems, and promptly cut off the power supply circuit or take other measures to avoid circuit damage.

[0004] However, in addition to the fault current caused by arcing in the DC cable, there are also large common-mode currents or various situations in which the spectrum of other current signals is elevated. These situations are not arcing abnormalities, but will cause great interference to arcing detection, resulting in inaccurate detection. Summary of the invention

[0005] In view of this, embodiments of the present application provide a multi-channel PV (Photovoltaic) arc detection device, an arc detection method, and a photovoltaic power generation system.

[0006] On the one hand, an embodiment of the present application provides a multi-channel PV arc detection device, comprising:

[0007] A current detection component is sleeved on at least one pair of photovoltaic DC cables and is used to detect differential mode signals on the at least one pair of photovoltaic DC cables; the at least one pair of photovoltaic DC cables are two photovoltaic DC cables connected to the same converter and not belonging to the same photovoltaic string, including a first cable and a second cable; wherein the first cable is obtained by merging the same polarity output ends of n photovoltaic strings; the second cable is obtained by merging the same polarity output ends of m photovoltaic strings; both n and m are integers greater than or equal to 1;

[0008] The first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein the first direction is opposite to the second direction; i and j are both integers greater than or equal to 1, and the product of i and n is equal to the product of j and m.

[0009] In some embodiments, the i is the smallest integer such that the product of the i and the n is equal to the product of the j and the m; and / or

[0010] The j is a minimum integer such that the product of the i and the n is equal to the product of the j and the m.

[0011] In some embodiments, the photovoltaic string includes a positive cable and a negative cable; the target cable is formed by the convergence of one or more positive cables or negative cables of the photovoltaic strings; the current of the target cable is the sum of the currents on the converged positive cables or negative cables of the one or more photovoltaic strings; wherein the target cable is the first cable or the second cable.

[0012] In some embodiments, the first cable and the second cable are both obtained by converging the positive cables of the photovoltaic string.

[0013] In some embodiments, the multi-channel PV arc detection device includes: at least two of the current detection components;

[0014] The two photovoltaic DC cables are used as a pair of photovoltaic DC cables and are wound through one current detection component; and the photovoltaic DC cables are both connected to the same converter.

[0015] In some embodiments, the multi-channel PV arc detection device further includes: a power control unit;

[0016] The power control unit is used to control the output power of the converter to be reduced to a preset first power when the differential mode signal detected by any of the current detection components indicates the existence of an arcing abnormality, and to restore the output power of the converter to a second power after a preset time period; wherein the second power is the power for the photovoltaic string to operate normally; after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

[0017] On the other hand, an embodiment of the present application provides an arc detection method, comprising:

[0018] A current detection component is used to detect a differential signal on at least one pair of photovoltaic DC cables that are sleeved; the at least one pair of photovoltaic DC cables are two photovoltaic DC cables connected to the same converter and belonging to different photovoltaic strings, including a first cable and a second cable; wherein the first cable is obtained by merging the same polarity output ends of n photovoltaic strings; the second cable is obtained by merging the same polarity output ends of m photovoltaic strings; both n and m are integers greater than or equal to 1; the first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein the first direction is opposite to the second direction; both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m;

[0019] If the current detection component detects that the differential mode signal is greater than or equal to a preset threshold, it is determined that the at least one pair of photovoltaic DC cables that are connected includes at least one photovoltaic string that has an arcing abnormality.

[0020] In some embodiments, the method further comprises:

[0021] If it is determined that the arcing abnormality is detected, controlling the output power of the converter to be reduced to a preset first power;

[0022] After maintaining the first power for a preset period of time, the output power of the converter is restored to the second power, wherein the second power is the power required for the photovoltaic string to operate normally; after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

[0023] On the other hand, an embodiment of the present application provides a photovoltaic power generation system, comprising: any of the above-mentioned multi-channel PV arc detection devices, and a plurality of photovoltaic strings;

[0024] Each photovoltaic string includes a positive cable and a negative cable; the same polarity output ends of n photovoltaic strings converge to form a first cable; the same polarity output ends of m photovoltaic strings converge to form a second cable; the first cable and the second cable serve as a pair of photovoltaic DC cables passing through the multi-channel PV arc detection device; both n and m are integers greater than or equal to 1;

[0025] The first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m;

[0026] The photovoltaic power generation system further includes: at least one converter, and the converter is connected to at least one pair of photovoltaic DC cables.

[0027] In some embodiments, it also includes:

[0028] A bus capacitor connected to the at least one converter;

[0029] An inverter circuit connected to the bus capacitor;

[0030] A power grid is connected to the inverter circuit.

[0031] The multi-channel PV arc detection device provided by the embodiment of the present application winds two photovoltaic DC cables including different photovoltaic strings in opposite directions on the current detection components, and makes the number of turns of the two cables equal to the product of the number of photovoltaic strings they converge. Since the common-mode signals generated on each photovoltaic string are roughly the same, the differential-mode signals are also roughly the same, and the converged cables have multiple common-mode signals and differential-mode signals. Therefore, by setting the number of winding turns as mentioned above, the common-mode signals on the two cables can be offset, so the noise components can be directly and automatically filtered out, and the arc can be quickly detected by detecting the differential-mode signal and the change of the differential-mode signal with very few current detection components. In addition, the device has a simple structure and does not require an additional computing module, so that the noise components in the circuit are directly offset from the hardware structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of a multi-channel PV arc detection device provided in an embodiment of the present application;

[0033] Figure 2 A schematic diagram of the structure of another multi-channel PV arc detection device provided in an embodiment of the present application;

[0034] Figure 3 A schematic diagram of the structure of another multi-channel PV arc detection device provided in an embodiment of the present application;

[0035] Figure 4 A schematic diagram of the structure of a current detection component in a multi-channel PV arc detection device provided in an embodiment of the present application;

[0036] Figure 5 A flow chart of an arc detection method provided in an embodiment of the present application;

[0037] Figure 6 The structure of the photovoltaic power generation system provided in the embodiment of the present application is shown in FIG. Figure 1 ;

[0038] Figure 7 The structure of the photovoltaic power generation system provided in the embodiment of the present application is shown in FIG. Figure 2 . DETAILED DESCRIPTION

[0039] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in a variety of different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of realizing the description of specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items. In the present application embodiment, the terms "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the feature defined as "first", "second", "third", "fourth" can explicitly or implicitly include one or more of the features.

[0041] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly stipulated and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements.

[0042] Arc signals are similar to white noise signals, and their energy is distributed in almost all spectra, showing as the rise of energy in different frequency bands. Since the on-site environment of the photovoltaic system is complex and changeable, there are often multiple devices working simultaneously on the same line, and the frequent on and off of the switching power supply can easily cause the photovoltaic (PV) current signal spectrum energy of the inverter to rise erroneously; the PV on-site irradiation step and PV current mutation can also cause the PV current signal spectrum energy to rise erroneously; the malfunction of other DC switches on the same line can also cause the PV current signal spectrum energy to rise erroneously, which in turn causes the whole machine to falsely report a DC arc fault. How to filter out interference signals and enhance the strength of the arc signal has become the focus of DC arc detection.

[0043] The present application embodiment provides a multi-channel PV arc detection device, such as Figure 1 As shown, the multi-channel PV arc detection device 100 includes:

[0044] The current detection component 110 is sleeved on at least one pair of photovoltaic DC cables 210 and is used to detect the differential mode signal on the at least one pair of photovoltaic DC cables 210; the at least one pair of photovoltaic DC cables 210 are two photovoltaic DC cables 210 connected to the same converter and belonging to different photovoltaic strings, including a first cable 211 and a second cable 212; wherein the first cable 211 is obtained by converging the same polarity output ends of n photovoltaic strings PV1; the second cable 212 is obtained by converging the same polarity output ends of m photovoltaic strings PV2; both n and m are integers greater than or equal to 1;

[0045] The first cable 211 is wound around the current detection component 110i in a first direction; the second cable 212 is wound around the current detection component 110j in a second direction; wherein the first direction is opposite to the second direction; the i and the j are both integers greater than or equal to 1, and the product of the i and the n is equal to the product of the j and the m.

[0046] The current detection component 110 can be used to realize DC current detection. When it is sleeved on the photovoltaic DC cable 210, it can detect the current signal flowing through the photovoltaic DC cable 210. Here, the converter can be a maximum power point tracking solar controller (Maximum Power Point Tracking, MPPT), an inverter or a converter, etc., which is used to realize the processing of photogenerated current in a solar photovoltaic system. Multiple photovoltaic DC cables connected to the same converter are grouped, and each group can include a pair of photovoltaic DC cables 210, that is, the first cable 211 and the second cable 212 connecting different photovoltaic strings of the same converter are used as a pair of DC cables to simultaneously pass through the current detection component in reverse phase.

[0047] In some embodiments, the photovoltaic string includes a positive cable and a negative cable; the target cable is formed by the convergence of the positive cables or negative cables of one or more of the photovoltaic strings; the current of the target cable is the sum of the currents on the positive cables or negative cables of the converged one or more photovoltaic strings; wherein the target cable is the first cable or the second cable.

[0048] Specifically, the first cable 211 can be obtained by converging the positive (or negative) DC cables of n photovoltaic strings, and the second cable can be obtained by converging the positive (or negative) DC cables of m photovoltaic strings. n can be 1 or a positive integer greater than 1, and m can be a positive integer 1 or greater than 1. Exemplarily, the first cable 211 includes only the positive DC cable of one photovoltaic string; and the second cable 212 is obtained by converging the positive DC cables of two photovoltaic strings, that is, n=1, and m=2. In this way, the photovoltaic current intensity on the first cable 211 (the photovoltaic current to be transmitted by a normal photovoltaic string) is the photovoltaic current intensity of the positive DC cable of one photovoltaic string, while the current intensity on the second cable 212 is the photovoltaic current intensity of the positive DC cables of two photovoltaic strings, that is, twice the photovoltaic current intensity on the first cable 211. Since the DC cables of each photovoltaic string are interfered by the common mode signal, the strength of the common mode signal on the second cable 212 is twice that of the common mode signal on the first cable 211 .

[0049] Therefore, in the embodiment of the present application, the common-mode signal and the photocurrent on the pair of photovoltaic DC cables are at the same magnitude and almost equal by winding the first cable 211 and the second cable 212 around the same current detection component 110 in different numbers of turns. For example, in the above example, when n=1 and m=2, the first cable 211 can be wound i=2 times, and the second cable 212 can pass directly in the opposite direction, that is, j=1 times, or the first cable 211 can be wound i=4 times, and the second cable 212 can be wound j=2 times in the opposite direction; for another example, Figure 1 As shown, n=3 and m=2, wherein the positive cables PV1, PV2 and PV3 of the three photovoltaic strings are converged to obtain the first cable 211, and the negative cables PV4 and PV5 of the two photovoltaic strings are converged to obtain the second cable 212. At this time, the first cable 211 can be wound i=2 times, and the second cable 212 can be wound j=3 times to ensure that the number of turns of the first cable 211 and the second cable 212 is equal to the product of the number of converged photovoltaic strings. In some embodiments, i is the smallest integer that satisfies the condition that the product of i and n is equal to the product of j and m; and / or j is the smallest integer that satisfies the condition that the product of i and n is equal to the product of j and m. In this way, the number of turns is minimized, which is easy to implement and saves cable length.

[0050] Furthermore, by passing the first cable 211 and the second cable 212 through the current detection component in a positive and negative direction, the common mode signal is offset, thereby removing the common mode interference from the physical structure without affecting the normal photocurrent transmission of the cable.

[0051] In some embodiments, the first cable 211 and the second cable 212 are both obtained by the convergence of the positive cables of the photovoltaic strings. The first cable 211 is a positive DC cable of one photovoltaic string, or a convergence of positive DC cables of multiple photovoltaic strings; and the second cable 212 is also a positive DC cable of one photovoltaic string, or a convergence of positive DC cables of multiple photovoltaic strings. Then, by passing through the current detection component 110 in the above manner, the common mode signal and the photogenerated current (differential mode signal) are both offset in the current signal finally detected by the current detection component 110, and the differential mode current generated by the arc can be detected only when an arc abnormality occurs. Exemplarily, the current on the positive DC cable of each photovoltaic string is I0, then the current of the first cable 211 passing through the current detection component 110 is I1=(n*i)*I0, and the current of the second cable 212 is I2=-(m*j)*(I0)=-(m*j)*I0. According to the winding rules in the above scheme, (n*i)=(m*j). Therefore, I1 and I2 are equal in magnitude and opposite in direction. The total current detected by the current detection component 110 is offset, so that the current signal detected by the current detection component 110 is less than the predetermined threshold value It1. If an arcing abnormality occurs on any cable, a current greater than the predetermined threshold value It1 will be detected.

[0052] If the first cable 211 and the second cable 212 are cables with different polarities, for example, the first cable 211 is a positive DC cable of a photovoltaic string, or a combination of positive DC cables of multiple photovoltaic strings; and the second cable 212 is a negative DC cable of a photovoltaic string, or a combination of negative DC cables of multiple photovoltaic strings, then the common mode signal is offset in the current signal finally detected by the current detection component 110 by the above method, and the photocurrent is the least common multiple of the currents on the two cables. In other words, since the current polarities of the two photovoltaic DC cables are opposite, and the directions of passing through the current detection component 110 are also opposite, the two currents are superimposed and doubled. Exemplarily, the current on the positive DC cable of each photovoltaic string is I0, and the current on the negative DC cable is -I0. Then the current of the first cable 211 passing through the current detection component 110 is I1=(n*i)*I0, and the current of the second cable 212 is I2=-(m*j)*(-I0)=(m*j)*I0. According to the winding rules in the above scheme, (n*i)=(m*j). Therefore, the above I1 is equal to I2, and the current detected on the current detection component 110 is approximately 2I1 (i.e. 2I2). When an arcing abnormality occurs, the detected current does not have a common mode signal, and an arcing algorithm is performed to identify the arcing abnormality. Specifically, if n=2, m=3, the number of winding coils is i=3, j=2, and the current on the positive DC cable of each photovoltaic string is I0, then the current detection component 110 detects a current of approximately 6I0 when no arcing abnormality occurs. When the detected current is I and |I-6I0|≥It2, it is determined that an arcing abnormality is detected.

[0053] Thus, compared with the method of detecting the current on each photovoltaic DC cable separately and then determining the differential signal by differential calculation, the above scheme of the embodiment of the present application does not require an additional calculation module. In addition, the cable winding method in the embodiment of the present application can be applied to various photovoltaic string convergence situations by designing the cable winding method, reducing the number of current detection components 110, facilitating implementation, being simple and flexible, and being applicable to the structure of various photovoltaic systems, without the need for complex circuit connection, having low cost and facilitating adjustment and change of cable layout.

[0054] Moreover, since the scheme directly eliminates the influence of common-mode signals, there is no situation where common-mode interference still exists due to calculation errors. In addition, since the generation of arcing signals is random, even if arcing occurs in two photovoltaic DC cables at the same time, the above scheme can at least detect the presence of arcing anomalies on these photovoltaic DC cables, thus effectively improving the accuracy of detection.

[0055] In some embodiments, Figure 2As shown, the multi-channel PV arc detection device 100 includes: at least two current detection components 110;

[0056] The two photovoltaic DC cables 210 as the pair of photovoltaic DC cables 210 are wound through one current detection component 110; and the photovoltaic DC cables 210 are both connected to the same converter.

[0057] The same MPPT can be connected to multiple photovoltaic DC cables 210, and one or more photovoltaic DC cables 210 can be obtained by converging positive cables of multiple photovoltaic strings. Since two photovoltaic DC cables 210 pass through one current detection component 110, when the same converter is connected to multiple photovoltaic DC cables, two or more current detection components 110 are required.

[0058] Figure 2 The situation of 4 groups of photovoltaic strings is shown, among which 3 photovoltaic strings PV1, PV2 and PV3 are integrated as the first cable 211 of the first current detection component 110, that is, n=2; 2 photovoltaic strings PV4 and PV5 are integrated as the second cable 212 of the first current detection component 110, that is, m=2; and the first cable 211 is wound around 2 times, that is, i=2, and the second cable 212 is wound around 3 times in the opposite direction, that is, j=3; 1 photovoltaic string PV6 is directly used as the first cable 211 of the second current detection component 110, that is, n=1; 2 photovoltaic strings PV7 and PV8 are integrated as the second cable 212 of the second current detection component 110, that is, m=2; and the first cable 211 is wound around 2 times, that is, i=2, and the second cable 212 is directly passed through in the opposite direction, that is, j=1.

[0059] In one embodiment, the two photovoltaic DC cables 210 may be adjacent cables or non-adjacent cables. That is, if the number of photovoltaic DC cables 210 connected to the same converter is an even number, they may be divided into multiple groups, with each group of two connected to a current detection component 110. In this way, when the number of photovoltaic DC cables 210 connected to the same converter is N, the number of current detection components 110 is N / 2. Of course, if the number of photovoltaic DC cables 210 connected to the same converter is an odd number, another current detection component 110 may be added, and the extra one may be passed through the current detection component 110 as a pair with any other photovoltaic DC cable 210.

[0060] In another embodiment, each two adjacent photovoltaic DC cables 210 may pass through a current detection component 110, that is, the same photovoltaic DC cable 210 may pass through two adjacent current detection components 110. In this way, when the number of photovoltaic DC cables 210 connected to the same converter is N, the number of current detection components 110 is N-1. In addition, a current detection component 110 may be added on this basis, and the first photovoltaic DC cable 210 and the last photovoltaic DC cable 210 may pass through the current detection component 110, and the number of current detection components 110 is N at this time.

[0061] For example, Figure 3 As shown, each photovoltaic DC cable 210 except the first and last one passes through two adjacent current detection components 110, so that the specific cable that produces the arcing anomaly can be located more accurately. Figure 3 The situation of three groups of photovoltaic strings is shown, in which the three photovoltaic strings PV1, PV2 and PV3 are combined as the first cable 211 of the first current detection component 110; the two photovoltaic strings PV4 and PV5 are combined as the second cable 212 of the first current detection component 110; at this time n=3, m=2. In addition, the first cable 211 is wound 2 times, and the second cable 212 is wound 3 times in the opposite direction. At the same time, the combined flow of the above two photovoltaic strings PV4 and PV5 is also used as the first cable 211 of the second current detection component 110, at this time n=2; one photovoltaic string PV6 is directly used as the second cable 212 of the second current detection component 110, that is, m=3, therefore, the first cable 211 obtained by the combined flow of PV4 and PV5 directly passes through the second current detection component 110, that is, i=1; the second cable 212 of the second current detection component 110 passes through by winding 2 times in the opposite direction, that is, j=2.

[0062] In another embodiment, there are 4 photovoltaic DC cables (including photovoltaic DC cables obtained by converging multiple photovoltaic strings), the first and second cables pass through the first current detection component 110, the second and third cables pass through the second current detection component 110, and the third and fourth cables pass through the third current detection component 110. In this way, when the first current detection component 110 detects an arcing signal and the other two current detection components 110 do not detect it, it means that an arcing abnormality has occurred on the first photovoltaic DC cable; when the first and second current detection components 110 both detect an arcing signal and the third one does not detect it, it means that an arcing abnormality has occurred on the second photovoltaic DC cable; when the second and third current detection components 110 both detect an arcing signal and the first one does not detect it, it means that an arcing abnormality has occurred on the third photovoltaic DC cable; when the third current detection component 110 detects an arcing signal and the other two current detection components 110 do not detect it, it means that an arcing abnormality has occurred on the fourth photovoltaic DC cable. In this way, the arcing anomaly can be accurately located in each photovoltaic DC cable.

[0063] In some embodiments, the multi-channel PV arc detection device further includes: a power control unit;

[0064] The power control unit is used to control the output power of the converter to be reduced to a preset first power when the differential mode signal detected by any of the current detection components indicates the existence of an arcing abnormality, and to restore the output power of the converter to a second power after a preset time period; wherein the second power is the power for the photovoltaic string to operate normally; and after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

[0065] It is understandable that after the output power of the converter is reduced, it is not enough to maintain the arcing, so the arcing anomaly can be eliminated. In this way, the faulty photovoltaic strings can be quickly disconnected without having to check them one by one, reducing the impact of the arcing on the entire machine.

[0066] Furthermore, since the photovoltaic string that produces the abnormal arc cannot work normally due to the fault, when the output power of the converter is reduced, the faulty photovoltaic string eliminates the arc, but the photovoltaic string cannot restore the normal working voltage after restoring the output power of the converter, that is, it cannot provide sufficient output power. In other words, at this time, the electrical connection between the photovoltaic string and the converter is close to the disconnected state, thereby achieving automatic "decoupling". In this way, other photovoltaic strings may quickly resume normal operation, while the faulty photovoltaic string is automatically "decoupled", so that the normal operation of other photovoltaic strings can be quickly restored without being affected by the faulty photovoltaic string.

[0067] The power detection unit is used to obtain the power of each photovoltaic string through a power detection device or a voltage / current detection device of each photovoltaic string after the power is restored to the second power, if the faulty photovoltaic string needs to be located;

[0068] When the power of a certain photovoltaic string is less than a preset power threshold, the photovoltaic string can be determined as the photovoltaic string that generates the arc abnormality, or the photovoltaic string with the smallest detected power can be determined as the photovoltaic string that generates the arc abnormality.

[0069] Therefore, after the whole machine reduces the power to the first power for a period of time, the whole machine power can be restored to the second power. It can be understood that restoring power is to power on the whole machine again, but because a certain photovoltaic string (the location where the arcing abnormality occurred before) still has an abnormality, the photovoltaic string cannot be restored to normal working power, while other photovoltaic strings can be restored to normal working power. Therefore, the second power at this time may be slightly lower than the power of the whole machine when it is in normal operation, and the second power is lower than the maximum output power of the whole machine when it is in normal operation.

[0070] In a photovoltaic power generation system, each photovoltaic string may include a power detection unit that can monitor the output power of the photovoltaic string in real time. When the power of the entire machine is restored to the second power, the power detection unit of each photovoltaic string can detect whether the power of the photovoltaic string is within a normal operating range. If the power is low, for example, lower than a preset threshold, the photovoltaic string is determined to be abnormal, thereby achieving accurate positioning of the photovoltaic string with abnormal arcing.

[0071] In some embodiments, Figure 4 As shown, the current detection component 110 includes:

[0072] The electromagnetic induction unit 111 is used to generate an electromagnetic induction signal according to the at least one pair of photovoltaic DC cables 210 (such as Figure 1 The differential mode signal on the first cable 211 and the second cable 212) shown generates an induced magnetic field;

[0073] The induction signal output unit 112 is used to output a corresponding induction signal based on the induction magnetic field.

[0074] Since the electromagnetic induction unit can sense the magnetic field and magnetic field changes generated by current changes, the electromagnetic induction unit can directly generate a corresponding induced magnetic field through the current of the differential mode signal, and then the induced signal output unit can output the corresponding induced signal, that is, the induced current, through the induced magnetic field.

[0075] In this way, the sensing signal indicates that there is a differential signal (or the differential signal is large enough) between the photovoltaic DC cables 210 connected to the current detection component 110, and then it can be determined whether there is an arcing abnormality in the photovoltaic DC cables 210 connected to the current detection component 110.

[0076] In some embodiments, the multi-channel PV arc detection device further includes:

[0077] The arcing alarm device is connected to the sensing signal output unit and is used to determine whether there is an arcing abnormality on the at least one pair of photovoltaic DC cables according to the sensing signal, and output a corresponding alarm signal.

[0078] For example, when the differential mode signal detected by the current detection component is greater than a certain threshold, it can be considered that an arcing abnormality exists, and an arcing alarm device can be used to give an alarm or cut off the circuit.

[0079] Exemplarily, the arcing alarm device may be an alarm device of sound, light or electric signal, or a device that sends an alarm indication signal to a related computer system through a computer instruction, or a switching device including a circuit cut-off device.

[0080] In addition, the arcing alarm device can also use the method in the above embodiment to perform the operation of reducing the power of the whole machine, and restore the power of the whole machine after a period of time, and then search for one photovoltaic string whose power is significantly lower than other photovoltaic strings, so as to locate the specific location where the arcing abnormality occurs.

[0081] In this way, the arcing alarm device of the current detection component can achieve a quick response to the arcing abnormality, so that other processing systems or personnel can perform relevant processing on the arcing abnormality in a timely manner.

[0082] In some embodiments, the current detection component includes: a current transformer and / or a Hall sensor.

[0083] Based on the same inventive concept, the present application embodiment provides an arc detection method, such as Figure 5 As shown, the method includes:

[0084] Step S101, using a current detection component to detect a differential signal on at least one pair of photovoltaic DC cables that are sleeved; the at least one pair of photovoltaic DC cables are two photovoltaic DC cables that are connected to the same converter and do not belong to the same photovoltaic string, including a first cable and a second cable; wherein the first cable is obtained by converging the same polarity output ends of n photovoltaic strings; the second cable is obtained by converging the same polarity output ends of m photovoltaic strings; both n and m are integers greater than or equal to 1; the first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein the first direction is opposite to the second direction; both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m;

[0085] Step S102: If the current detection component detects that the differential mode signal is greater than or equal to a preset threshold, it is determined that the at least one pair of photovoltaic DC cables connected includes at least one photovoltaic string that has an arcing abnormality.

[0086] Here, one of the implementation methods for the specific application of the above-mentioned multi-channel PV arc detection device is provided, that is, using the current detection component in the multi-channel PV arc detection device to directly detect the current signal on each photovoltaic DC cable sleeved on the current detection component. The magnitude of the current signal can be used to reflect whether there is an arc abnormality on these cables.

[0087] Exemplarily, a threshold value may be set, and when the current signal is greater than the threshold value, it is determined that an arcing anomaly exists on the photovoltaic DC cables, and a corresponding alarm signal may be output for subsequent processing.

[0088] In this way, by utilizing the multi-channel PV arc detection device provided in the embodiment of the present application, it is possible to simply and quickly detect whether there is an arc abnormality, and can effectively reduce false alarms caused by common mode interference, thereby improving the accuracy of arc detection.

[0089] In some embodiments, the method further comprises:

[0090] If it is determined that the arcing abnormality is detected, the output power of the converter is controlled to be reduced to a preset first power;

[0091] After maintaining the first power for a preset period of time, the output power of the converter is restored to the second power, wherein the second power is the power required for the photovoltaic string to operate normally; after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

[0092] The above method has the same inventive concept as the multi-channel PV arc detection device provided in the embodiment of the present application. Its specific implementation method can refer to the relevant description of any embodiment of the multi-channel PV arc detection device, which will not be repeated here.

[0093] Based on the same inventive concept, the embodiment of the present application provides a photovoltaic power generation system, such as Figure 6 As shown, the photovoltaic power generation system 300 includes: a multi-channel PV arc detection device 100 in any of the above embodiments, a plurality of photovoltaic strings 310, and a plurality of solar panels 311 respectively connected to different photovoltaic strings 310;

[0094] Each photovoltaic string 310 includes a positive photovoltaic DC cable PV+ and a negative photovoltaic DC cable PV-; n photovoltaic strings 310 are converged to form a first cable 211; m photovoltaic strings 310 are converged to form a second cable 212; both n and m are integers greater than or equal to 1;

[0095] The first cable 211 is wound around the current detection component 110i in a first direction; the second cable 212 is wound around the current detection component 110j in a second direction; wherein both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m; Figure 4 The winding method of the first cable 211 and the second cable 212 is not shown in the figure, and reference may be made to the above Figure 1 .

[0096] The photovoltaic power generation system 300 further includes: at least one MPPT 320, and the MPPT 320 is connected to at least one pair of photovoltaic DC cables.

[0097] In some embodiments, Figure 7 As shown, the photovoltaic power generation system 300 further includes:

[0098] A bus capacitor 330 connected to the at least one MPPT 320;

[0099] An inverter circuit 340 connected to the bus capacitor 330;

[0100] The power grid 350 is connected to the inverter circuit 340 .

[0101] The above-mentioned photovoltaic power generation system has the same inventive concept as the multi-channel PV arc detection device involved in any embodiment of the present application. Its specific implementation method can be understood by referring to the description in any embodiment of the above-mentioned multi-channel PV arc detection device, and will not be repeated here.

[0102] It should be understood that "some embodiments", "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiments are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned sequence numbers of the embodiments of the present application are for description only and do not represent the advantages and disadvantages of the embodiments.

[0103] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0104] The above is only an implementation method of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A multi-channel PV multi-channel PV arc detection device, characterized in that: include: A current detection component is sleeved on at least one pair of photovoltaic DC cables and is used to detect differential mode signals on the at least one pair of photovoltaic DC cables; the at least one pair of photovoltaic DC cables are two photovoltaic DC cables connected to the same converter and not belonging to the same photovoltaic string, including a first cable and a second cable; wherein the first cable is obtained by merging the same polarity output ends of n photovoltaic strings; the second cable is obtained by merging the same polarity output ends of m photovoltaic strings; both n and m are integers greater than or equal to 1; The first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein the first direction is opposite to the second direction; i and j are both integers greater than or equal to 1, and the product of i and n is equal to the product of j and m.

2. The multi-channel PV arc detection device according to claim 1, characterized in that: The i is the smallest integer such that the product of the i and the n is equal to the product of the j and the m; and / or The j is a minimum integer such that the product of the i and the n is equal to the product of the j and the m.

3. The multi-channel PV arc detection device according to claim 1, characterized in that: The photovoltaic string includes a positive cable and a negative cable; the target cable is formed by the convergence of one or more positive cables or negative cables of the photovoltaic strings; the current of the target cable is the sum of the currents on the converged positive cables or negative cables of the one or more photovoltaic strings; wherein the target cable is the first cable or the second cable.

4. The multi-channel PV arc detection device according to claim 3, characterized in that: The first cable and the second cable are both obtained by converging the positive cables of the photovoltaic string.

5. The multi-channel PV arc detection device according to claim 1, characterized in that: Also includes: at least two of the current detection components; The two photovoltaic DC cables are used as a pair of photovoltaic DC cables and are wound through one current detection component; and the photovoltaic DC cables are both connected to the same converter.

6. The multi-channel PV arc detection device according to any one of claims 1 to 5, characterized in that: Also includes: Power control unit; The power control unit is used to control the output power of the converter to be reduced to a preset first power when the differential mode signal detected by any of the current detection components indicates the existence of an arcing abnormality, and to restore the output power to a second power after a preset time period; wherein the second power is the power for the photovoltaic string to operate normally; after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

7. An arc detection method, characterized in that: The method comprises: A current detection component is used to detect a differential signal on at least one pair of photovoltaic DC cables that are sleeved; the at least one pair of photovoltaic DC cables are two photovoltaic DC cables that are connected to the same converter and do not belong to the same photovoltaic string, including a first cable and a second cable; wherein the first cable is obtained by merging the same polarity output ends of n photovoltaic strings; the second cable is obtained by merging the same polarity output ends of m photovoltaic strings; both n and m are integers greater than or equal to 1; the first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein the first direction is opposite to the second direction; both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m; If the current detection component detects that the differential mode signal is greater than or equal to a preset threshold, it is determined that the at least one pair of photovoltaic DC cables that are connected includes at least one photovoltaic string that has an arcing abnormality.

8. The method according to claim 7, characterized in that The method further comprises: If it is determined that the arcing abnormality is detected, controlling the output power of the converter to be reduced to a preset first power; After maintaining the first power for a preset period of time, the output power of the converter is restored to the second power, wherein the second power is the power required for the photovoltaic string to operate normally; after the output power of the converter is restored to the second power, the output power of the photovoltaic string that produces the arcing abnormality is less than the normal output power of the photovoltaic string.

9. A photovoltaic power generation system, characterized in that: include: A multi-channel PV arc detection device and a plurality of photovoltaic strings as claimed in any one of claims 1 to 7; Each photovoltaic string includes a positive cable and a negative cable; the same polarity output ends of n photovoltaic strings converge to form a first cable; the same polarity output ends of m photovoltaic strings converge to form a second cable; the first cable and the second cable serve as a pair of photovoltaic DC cables passing through the multi-channel PV arc detection device; both n and m are integers greater than or equal to 1; The first cable is wound around the current detection component i times in a first direction; the second cable is wound around the current detection component j times in a second direction; wherein both i and j are integers greater than or equal to 1, and the product of i and n is equal to the product of j and m; The photovoltaic power generation system further includes: at least one converter, and the converter is connected to at least one pair of photovoltaic DC cables.

10. The photovoltaic power generation system according to claim 9, characterized in that: Also includes: A bus capacitor connected to the at least one converter; An inverter circuit connected to the bus capacitor; A power grid is connected to the inverter circuit.

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