Arc detection device, arc detection method, and photovoltaic power generation system

Abstract

The embodiment of the present disclosure discloses a draw arc detection device, a draw arc detection method and a photovoltaic power generation system. The draw arc detection device comprises at least two current detection components; wherein each current detection component is respectively sleeved on two adjacent photovoltaic direct current cables for detecting the differential mode signal on the two photovoltaic direct current cables; wherein the two photovoltaic direct current cables comprise a first cable and a second cable with the same polarity, the direction of the first cable passing through the current detection component is opposite to the direction of the second cable passing through the current detection component; the two photovoltaic direct current cables belong to different photovoltaic strings connected to the same maximum power point tracking solar controller (MPPT); the first cable sleeved by every two adjacent current detection components is the same cable, and the second cable sleeved by every two adjacent current detection components is different cables.

Description

Technical Field

[0001] This disclosure relates to the field of power technology, and includes, but is not limited to, an arcing detection device, an arcing detection method, and a photovoltaic power generation system. Background Technology

[0002] With the development and widespread application of photovoltaic (PV) power generation technology, the technical requirements for PV systems, such as power output, are becoming increasingly stringent. A PV system consists of solar photovoltaic panels, PV DC cables, and inverters. It utilizes exposed solar panels to collect solar energy and convert it into photovoltaic power, thus generating electricity. However, PV cables are prone to DC arcing faults, also known as arcing faults, under conditions of aging, external environmental influences (such as animal bites or sudden changes in the natural environment), and sudden changes in PV energy.

[0003] A direct current arc is a gas discharge phenomenon near a cable, where current passes through an insulating medium such as air, producing a spark that simultaneously generates a momentary current in the cable. This arc can easily damage circuit components and cause system failure. Therefore, it is necessary to detect arcing faults in photovoltaic power generation systems and promptly disconnect the circuit or take other measures to prevent circuit damage.

[0004] However, in addition to the fault current generated by arcing, DC cables also have large common-mode currents or various other situations where the spectrum of current signals is raised. These situations are not arcing abnormalities, but they can cause significant interference to arcing detection, leading to inaccurate detection. Summary of the Invention

[0005] In view of this, the present disclosure provides an arc detection device, an arc detection method, and a photovoltaic power generation system.

[0006] On one hand, embodiments of this disclosure provide an arc detection device, including:

[0007] At least two current sensing components are provided; each current sensing component is respectively connected to two adjacent photovoltaic DC cables for detecting differential mode signals on the two photovoltaic DC cables; wherein the two photovoltaic DC cables include a first cable and a second cable of the same polarity, the first cable passing through the current sensing component in the opposite direction to the second cable passing through the current sensing component; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT (Maximum Power Point Tracking solar controller);

[0008] The first cable connected to each pair of adjacent current sensing components is the same cable, and the second cable connected to each pair of adjacent current sensing components is a different cable.

[0009] In some embodiments, the first photovoltaic DC cable passes through only one current detection component, the last photovoltaic DC cable passes through only one current detection component, and each of the other photovoltaic DC cables passes through two adjacent current detection components.

[0010] In some embodiments, each of the photovoltaic DC cables passes through an adjacent current sensing component, and the first and last photovoltaic DC cables also pass through one of the current sensing components.

[0011] In some embodiments, the current sensing component includes:

[0012] The electromagnetic induction unit is used to generate an induced magnetic field based on the differential mode signal on the two photovoltaic DC cables;

[0013] The induction signal output unit is used to output a corresponding induction signal based on the induction magnetic field.

[0014] In some embodiments, the arc detection device further includes:

[0015] An arcing alarm device is connected to the sensing signal output unit and is used to determine whether there is an arcing abnormality on the two photovoltaic DC cables based on the sensing signal, and to output a corresponding alarm signal.

[0016] In some embodiments, the current sensing component includes a current transformer and / or a Hall sensor.

[0017] In some embodiments, each photovoltaic string includes a positive cable and a negative cable; the two photovoltaic DC cables are either the positive cables of two adjacent photovoltaic strings or the negative cables of two adjacent photovoltaic strings.

[0018] On the other hand, this disclosure also provides an arc detection method, applied to any of the above-mentioned arc detection devices, the method comprising:

[0019] At least two current detection components are used to detect the differential mode signal on two connected photovoltaic DC cables respectively; wherein, the two photovoltaic DC cables include a first cable and a second cable with the same polarity; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT; the first cable and the second cable pass through the current detection components in opposite directions respectively;

[0020] If at least two adjacent current sensing components detect the differential mode signal indicating an abnormality, it is determined that there is an arcing abnormality on the same photovoltaic DC cable to which the at least two adjacent current sensing components are connected.

[0021] In another aspect, embodiments of this disclosure also provide a photovoltaic power generation system, including:

[0022] Multiple photovoltaic strings, each photovoltaic string including one positive photovoltaic DC cable and one negative photovoltaic DC cable;

[0023] At least one MPPT, wherein the MPPT is connected to at least two photovoltaic strings;

[0024] Any of the above-mentioned arc detection devices.

[0025] In some embodiments, the photovoltaic power generation system further includes:

[0026] Bus capacitor, connected to at least one MPPT;

[0027] The inverter circuit is connected to the bus capacitor;

[0028] The power grid is connected to the inverter circuit.

[0029] The arcing detection device provided in this embodiment connects a current detection component to two photovoltaic DC cables of different photovoltaic strings connected in the same MPPT (Multi-Pulse Test Device). This allows the current in both cables to pass through the current detection component simultaneously. The current detected by the current detection component is the differential-mode signal of the current in the two photovoltaic DC cables, thus automatically filtering out noise components and retaining only the current generated by arcing, resulting in high detection accuracy. Furthermore, the arcing detection device provided in this embodiment includes at least two current detection components, allowing at least one cable to pass through different current detection components. This facilitates the location of which specific photovoltaic DC cable is experiencing arcing abnormalities, improving detection accuracy and facilitating subsequent processing. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the arc detection device provided in the embodiments of this disclosure;

[0031] Figure 2 This is a schematic diagram of the structure of the current detection component connected to the cable in the arc detection device provided in this embodiment of the disclosure;

[0032] Figure 3 A flowchart of the arc detection method provided in this embodiment of the disclosure;

[0033] Figure 4 A schematic diagram of the structure of a photovoltaic power generation system provided in the embodiments of this disclosure. Figure 1 ;

[0034] Figure 5 A schematic diagram of the structure of a photovoltaic power generation system provided in the embodiments of this disclosure. Figure 2 . Detailed Implementation

[0035] To facilitate understanding of this disclosure, a more complete description will now be given with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein in the specification of this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In embodiments of this application, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include one or more of that feature.

[0037] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can be fixed connections, detachable connections, or integral connections; they can be direct connections or indirect connections through an intermediate medium; and they can be internal connections between two components.

[0038] Arc signals are similar to white noise signals, with energy distributed across almost the entire spectrum, manifesting as energy spikes in different frequency bands. Due to the complex and variable environment of photovoltaic systems, multiple devices often operate simultaneously on the same line. Frequent switching of the power supply can easily cause false spikes in the photovoltaic (PV) current signal spectrum energy of the inverter. Step changes in PV irradiance and sudden changes in PV current can also cause false spikes in the PV current signal spectrum energy. Malfunctions of other DC switches on the same line can also cause false spikes in the PV current signal spectrum energy, leading to false DC arc fault reports for the entire system. Therefore, filtering out interference signals and enhancing the arc signal strength has become a key focus of DC arc detection.

[0039] The causes of DC arcing in photovoltaic systems are highly random, and the location and timing of its occurrence are unpredictable. Factors such as severe weathering of cables, damage to DC lines, aging of electronic components, loose connections, or even animal bites can all lead to arcing faults. These various unpredictable factors make it impossible to accurately establish a mathematical model to directly determine whether a DC arcing fault exists in a photovoltaic system.

[0040] Arcing faults are usually accompanied by sudden fault currents, so current detection can be used to detect arcing faults. However, for photovoltaic DC cables within the same MPPT, there is a large common-mode current. Simply detecting the current of the photovoltaic DC cable cannot eliminate the influence of the common-mode current, which can easily lead to false alarms.

[0041] This disclosure provides an arc detection device, such as... Figure 1 As shown, the arc detection device 100 includes:

[0042] At least two current detection components 110 are provided; each current detection component 110 is respectively connected to two adjacent photovoltaic DC cables 210 for detecting differential mode signals on the two photovoltaic DC cables 210; wherein the two photovoltaic DC cables 210 include a first cable 211 and a second cable 212 of the same polarity, the first cable passes through the current detection component in the opposite direction to the second cable passing through the current detection component; the two photovoltaic DC cables 210 belong to different photovoltaic strings connected to the same MPPT;

[0043] The first cable 211 connected to each two adjacent current detection components 110 is the same cable, and the second cable 212 connected to each two adjacent current detection components 110 is a different cable.

[0044] For each current detection component 110, a pair of photovoltaic DC cables 210 with the same polarity and opposite directions can pass through the current detection component 110. This pair of photovoltaic DC cables 210 refers to the first cable 211 and the second cable 212 mentioned above. The arc detection component 110 can be used to realize DC current detection. It is sleeved on the photovoltaic DC cable 210 and can detect the current signal flowing through the photovoltaic DC cable 210.

[0045] The current detection component 110, which is connected to the two photovoltaic DC cables 210, does not detect the current in each cable, nor does it affect the normal transmission of current in each cable. Instead, it directly senses the differential mode signal in these photovoltaic DC cables 210. In other words, by passing the two photovoltaic DC cables 210 through the current detection component 110 in reverse order, the detection of the current differential mode signal can be achieved, effectively eliminating the influence of the common mode signal.

[0046] Therefore, compared to the method of determining the differential mode signal by calculating the current on each DC cable separately, the solution provided in this application is easy to implement, simple and flexible, applicable to the structure of various photovoltaic systems, requires no complex circuit connections, is low in cost, and is easy to adjust and change the cable layout.

[0047] Furthermore, since this scheme directly eliminates the influence of common-mode signals, there is no possibility of common-mode interference remaining due to calculation errors. Additionally, because the generation of arcing signals is random, even if arcing occurs simultaneously on two photovoltaic DC cables, the above scheme can at least detect the presence of arcing anomalies on these photovoltaic DC cables, thus effectively improving the accuracy of detection.

[0048] In some embodiments, each photovoltaic string includes a positive cable and a negative cable; the two photovoltaic DC cables are either the positive cables of two adjacent photovoltaic strings or the negative cables of two adjacent photovoltaic strings.

[0049] The aforementioned arc detection device includes multiple current detection components. These current detection components can be sequentially connected to the photovoltaic DC cable corresponding to the same MPPT, and every two adjacent current detection components are connected to the same photovoltaic DC cable. For example, as shown... Figure 2 As shown, one MPPT corresponds to three photovoltaic strings. The positive cable in each photovoltaic string is used for arc detection and is represented by cable PV1+, cable PV2+, and cable PV3+, respectively. Thus, the arc detection device can include two current detection components. Current detection component 111 is connected to cables PV1+ and PV2+, respectively, and current detection component 112 is connected to cables PV2+ and PV3+, respectively. That is, cable PV2+ is simultaneously connected to different current detection components. For current detection component 111, cable PV1+ belongs to the second cable and cable PV2+ belongs to the first cable; for current detection component 112, cable PV2+ belongs to the first cable and cable PV3+ belongs to the second cable.

[0050] Thus, when an arcing abnormality occurs on cable PV1+, only current detection component 111 can detect a sufficiently large differential mode signal; when an arcing abnormality occurs on cable PV2+, both current detection component 111 and current detection component 112 can detect a sufficiently large differential mode signal; and when an arcing abnormality occurs on cable PV3+, only current detection component 112 can detect a sufficiently large differential mode signal.

[0051] In other words, this method can not only determine that each photovoltaic string corresponding to the same MPPT has experienced arcing abnormality, but also identify the specific cable where the arcing abnormality occurred, thus facilitating subsequent abnormality handling.

[0052] In some embodiments, the first photovoltaic DC cable passes through only one current detection component, the last photovoltaic DC cable passes through only one current detection component, and each of the other photovoltaic DC cables passes through two adjacent current detection components.

[0053] In some embodiments, each of the photovoltaic DC cables passes through an adjacent current sensing component, and the first and last photovoltaic DC cables also pass through one of the current sensing components.

[0054] This provides two implementation methods for connecting current sensing components to different photovoltaic DC cables: the case of n-1 current sensing components for n photovoltaic DC cables, and the case of n current sensing components for n photovoltaic DC cables.

[0055] The first scenario is the case of three cables and two current detection components as illustrated in the above examples. This allows for the location of arcing anomalies, but in this case, only one current detection component is used for both the first and last cables, which may lead to false alarms.

[0056] The second scenario involves adding an additional current detection component to the first scenario. This component detects the differential mode signal between the first and last photovoltaic DC cables. With two current detection components for each photovoltaic DC cable, the occurrence of arcing anomalies can be more accurately determined, along with the specific cable location where the anomaly is occurring, further reducing the possibility of false alarms.

[0057] In some embodiments, the current sensing component includes:

[0058] An electromagnetic induction unit is used to generate an induced magnetic field based on the differential mode signal on two photovoltaic DC cables.

[0059] The induction signal output unit is used to output a corresponding induction signal based on the induction magnetic field.

[0060] Since the electromagnetic induction unit can sense the magnetic field generated by the change of current and the change of magnetic field, the electromagnetic induction unit can directly generate the 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, i.e., induced current, through the induced magnetic field.

[0061] Thus, the sensed signal indicates that there is a differential mode signal (or the differential mode signal is large enough) between the two photovoltaic DC cables connected to the current sensing component, which can then be used to determine whether there is an arcing abnormality in the two photovoltaic DC cables connected to the current sensing component.

[0062] In some embodiments, the arc detection device further includes:

[0063] An arcing alarm device is connected to the sensing signal output unit and is used to determine whether there is an arcing abnormality on the two photovoltaic DC cables based on the sensing signal, and to output a corresponding alarm signal.

[0064] For example, when the differential mode signal detected by the current detection component is greater than a certain threshold, it can be considered that there is an arcing abnormality, and then the arcing alarm device can be used to alarm or cut off the circuit.

[0065] For example, the arcing alarm device can be an alarm device with sound, light or electrical signals, or a device that sends an alarm indication signal to a relevant computer system through computer instructions, or a switching device including circuit cutting off.

[0066] Thus, the arcing alarm device of the aforementioned current detection component can achieve a rapid response to arcing anomalies, so that other processing systems or personnel can promptly handle the arcing anomalies.

[0067] In some embodiments, the current sensing component includes a current transformer and / or a Hall sensor.

[0068] A current transformer is a commonly used current detection device that utilizes electromagnetic principles. This device involves attaching a magnetic core to a cable. When a change in current occurs in the cable, an induced magnetic field is generated. Since an induction winding is also wound around the magnetic core, based on the principle of electromagnetic induction, the induced magnetic field also generates a corresponding induced current in the induction winding. Thus, the current flowing through the cable can be calculated by detecting the induced current.

[0069] In this embodiment, since the cables connected in the magnetic core pass through in pairs in opposite directions, the common-mode signal is canceled out, thus no induced magnetic field is generated. Only when an arcing abnormality generates a differential-mode signal will an induced magnetic field be generated on the magnetic core, thereby generating an induced current in the induction winding.

[0070] In this way, the presence of arcing abnormalities can be directly determined by detecting the induced current.

[0071] Hall sensors can detect current using the Hall effect. The Hall effect is an electromagnetic effect; specifically, when a solid conductor is placed in a magnetic field and a current flows through it, the charge carriers in the conductor are deflected to one side by the Lorentz force, thus generating a Hall voltage.

[0072] Since the arcing signal generated on the aforementioned photovoltaic DC cable is an instantaneous current signal, it will produce a corresponding magnetic field. The differential mode signal generated by the differential mode signal of the paired photovoltaic DC cables can be detected using a Hall effect sensor.

[0073] Therefore, the Hall device can be placed in an adjacent position to at least one pair of photovoltaic DC cables. Specifically, the Hall device can be set on a fixed ring and sleeved on at least one pair of photovoltaic DC cables, so that it is located within the range of the magnetic field generated by the photovoltaic DC cables.

[0074] By using a current source, a current can be applied to one direction of the Hall device, and the voltage in the other direction reflects the magnitude of the magnetic field generated by the differential-mode signal. Therefore, the differential-mode signal can be detected by detecting this voltage.

[0075] Based on the same inventive concept, this disclosure also provides an arc detection method, applicable to any of the above-mentioned arc detection devices, such as... Figure 3 As shown, the method includes:

[0076] Step S101: Use at least two current detection components to detect the differential mode signal on the two connected photovoltaic DC cables respectively; wherein, the two photovoltaic DC cables include a first cable and a second cable with the same polarity; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT; the first cable and the second cable pass through the current detection components in opposite directions respectively;

[0077] Step S102: If at least two adjacent current detection components detect the differential mode signal indicating an abnormality, it is determined that there is an arcing abnormality on the same photovoltaic DC cable connected to the at least two adjacent current detection components.

[0078] This section provides one method for implementing the aforementioned arc detection device: directly detecting the differential mode signal on the two photovoltaic DC cables connected to the current detection component within the device. This differential mode signal can be used to indicate whether an arcing abnormality exists on these two cables.

[0079] For example, a threshold can be set. When the differential signal is greater than the threshold, it is determined that there is an arcing abnormality on the two photovoltaic DC cables, and a corresponding alarm signal can be output for subsequent processing.

[0080] Furthermore, since adjacent current detection components are connected to the same photovoltaic DC cable, when an arcing anomaly occurs in one of the photovoltaic DC cables, both current detection components passing through it will detect the arcing anomaly. This allows for accurate identification of which specific cable experienced the arcing anomaly.

[0081] As can be seen, by using the arcing detection device provided in this application embodiment, the presence of arcing abnormality can be detected simply and quickly, effectively reducing false alarms caused by common-mode interference, and the specific cable where the arcing abnormality occurs can be identified, thereby improving the accuracy of arcing detection.

[0082] Based on the same inventive concept, this disclosure also provides a photovoltaic power generation system, such as... Figure 4 As shown, the photovoltaic power generation system 400 includes:

[0083] Multiple photovoltaic strings 410, each photovoltaic string 410 includes one positive photovoltaic DC cable 411 and one negative photovoltaic DC cable 412;

[0084] At least one MPPT 420, wherein the MPPT 420 is connected to at least two photovoltaic strings 410;

[0085] Any of the above-mentioned arc detection devices 100.

[0086] In some embodiments, such as Figure 5 As shown, the photovoltaic power generation system 400 also includes:

[0087] Bus capacitor 430 is connected to at least one MPPT 420;

[0088] Inverter circuit 440 is connected to bus capacitor 430;

[0089] The power grid 450 is connected to the inverter circuit 440.

[0090] It should be understood that the phrases "some embodiments," "one embodiment," or "an embodiment" throughout the specification mean that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this disclosure. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this disclosure, the sequence numbers of the above-described processes do not imply a sequential 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 this disclosure. The sequence numbers of the above-described embodiments are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0091] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0092] The above description is merely an embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure.

Claims

1. An arc detection device, characterized in that, include: At least two current sensing components are provided; each current sensing component is respectively connected to two adjacent photovoltaic DC cables for detecting differential mode signals on the two photovoltaic DC cables; wherein the two photovoltaic DC cables include a first cable and a second cable of the same polarity, the first cable passing through the current sensing component in the opposite direction to the second cable passing through the current sensing component; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same maximum power point tracking solar controller (MPPT); The current detection component includes: An electromagnetic induction unit is used to generate an induced magnetic field based on the differential mode signal on the two photovoltaic DC cables; an induction signal output unit is used to output a corresponding induction signal based on the induced magnetic field. The first cable connected to each pair of adjacent current sensing components is the same cable, and the second cable connected to each pair of adjacent current sensing components is a different cable.

2. The apparatus according to claim 1, characterized in that, The first photovoltaic DC cable passes through only one current detection component, the last photovoltaic DC cable passes through only one current detection component, and each of the other photovoltaic DC cables passes through two adjacent current detection components.

3. The apparatus according to claim 1, characterized in that, Each of the photovoltaic DC cables passes through an adjacent current detection component, and the first and last photovoltaic DC cables also pass through a current detection component.

4. The apparatus according to claim 1, characterized in that, The arc detection device further includes: An arcing alarm device is connected to the sensing signal output unit and is used to determine whether there is an arcing abnormality on the two photovoltaic DC cables based on the sensing signal, and to output a corresponding alarm signal.

5. The apparatus according to claim 3, characterized in that, The current detection component includes: a current transformer and / or a Hall sensor.

6. The apparatus according to any one of claims 1 to 5, characterized in that, Each photovoltaic string includes a positive cable and a negative cable; the two photovoltaic DC cables are either the positive cables of two adjacent photovoltaic strings or the negative cables of two adjacent photovoltaic strings.

7. A method for detecting arcing, characterized in that, The method, applied to the arc detection device as described in any one of claims 1 to 6, comprises: At least two current detection components are used to detect the differential mode signal on two connected photovoltaic DC cables respectively; wherein, the two photovoltaic DC cables include a first cable and a second cable with the same polarity; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT; the first cable and the second cable pass through the current detection components in opposite directions respectively; If at least two adjacent current sensing components detect the differential mode signal indicating an abnormality, it is determined that there is an arcing abnormality on the same photovoltaic DC cable to which the at least two adjacent current sensing components are connected.

8. A photovoltaic power generation system, characterized in that, include: Multiple photovoltaic strings, each photovoltaic string including one positive photovoltaic DC cable and one negative photovoltaic DC cable; At least one MPPT, wherein the MPPT is connected to at least two photovoltaic strings; The arc detection device as described in any one of claims 1 to 6.

9. The photovoltaic power generation system according to claim 8, characterized in that, Also includes: Bus capacitor, connected to at least one MPPT; The inverter circuit is connected to the bus capacitor; The power grid is connected to the inverter circuit.

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