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: a current detection assembly sleeved on at least one pair of photovoltaic direct-current cables, used for detecting a differential mode signal on the at least one pair of photovoltaic direct-current cables; wherein a pair of the photovoltaic direct-current cables comprises a first cable and a second cable of the same polarity, the direction of the first cable passing through the current detection assembly is opposite to the direction of the second cable passing through the current detection assembly; and the at least one pair of photovoltaic direct-current cables belong to different photovoltaic strings connected to the same MPPT.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the technical field of electric power, and relate to, but are not limited to, an arc detection device, an arc detection method, and a photovoltaic power generation system. BACKGROUND

[0002] With the development and wide application of photovoltaic power generation technology, the technical requirements for the power generation of photovoltaic systems are also becoming higher and higher. A photovoltaic system is composed of a solar photovoltaic panel, a photovoltaic DC cable, an inverter and the like. The solar photovoltaic panel is exposed to the outdoor environment to collect solar energy and convert it into electricity, thereby realizing photovoltaic power generation. However, the photovoltaic cable is prone to DC arc failure, also known as arc failure, in scenarios such as aging, external environmental influences (such as animal gnawing or natural environmental mutations), and photovoltaic energy mutations.

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

[0004] However, in addition to the fault current caused by arc in the DC cable, there is also a large common-mode current or various situations where the spectrum of other current signals is raised. These situations are not arc abnormalities, but they can cause great interference to arc detection, resulting in inaccurate detection. SUMMARY

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

[0006] In one aspect, the present disclosure provides an arc detection device, comprising:

[0007] a current detection assembly, which is sleeved on at least one pair of photovoltaic DC cables, and is configured to detect a differential mode signal on the at least one pair of photovoltaic DC cables; wherein a pair of the photovoltaic DC cables comprises a first cable and a second cable of the same polarity, the direction in which the first cable passes through the current detection assembly is opposite to the direction in which the second cable passes through the current detection assembly; and the at least one pair of photovoltaic DC cables belong to different photovoltaic strings connected to a same MPPT (Maximum Power Point Tracking).

[0008] In some embodiments, the current detection assembly comprises:

[0009] an electromagnetic induction unit, configured to generate an induced magnetic field according to the differential mode signal on the at least one pair of photovoltaic DC cables;

[0010] An induction signal output unit is configured to output a corresponding induction signal based on the induction magnetic field.

[0011] In some embodiments, the arc-drawing detection device further comprises:

[0012] An arc-drawing alarm device is connected to the induction signal output unit and configured to determine, according to the induction signal, whether there is an arc-drawing abnormality on the at least one pair of photovoltaic DC cables and output a corresponding alarm signal.

[0013] In some embodiments, the current detection component comprises a current transformer.

[0014] The electromagnetic induction unit is a magnetic core of the current transformer, and the induction signal output unit is an induction winding of the current transformer; wherein the induction winding is wound on the magnetic core.

[0015] In some embodiments, the magnetic core is a ring-shaped magnetic core, and the first cable and the second cable pass through the ring-shaped magnetic core.

[0016] In some embodiments, the current detection component comprises a Hall sensor.

[0017] The electromagnetic induction unit is a Hall device of the Hall sensor, and the induction signal output unit is a voltage output end connected to the Hall device.

[0018] The Hall sensor further comprises a current source connected across the Hall sensor and configured to generate a current in the Hall device.

[0019] The at least one pair of photovoltaic DC cables is located at adjacent positions of the Hall device, and the Hall device is configured to induce an induction magnetic field generated by the differential mode signal.

[0020] In some embodiments, each photovoltaic string comprises a positive cable and a negative cable; and a pair of the photovoltaic DC cables comprises positive cables of two adjacent photovoltaic strings or negative cables of two adjacent photovoltaic strings.

[0021] In another aspect, the embodiments of the present disclosure provide an arc-drawing detection method applied to any one of the arc-drawing detection devices described above, and the method comprises:

[0022] detecting a differential mode signal on the at least one pair of photovoltaic DC cables; wherein a pair of the photovoltaic DC cables comprises a first cable and a second cable of the same polarity; the at least one pair of photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT; and the first cable and the second cable pass through the current detection component in opposite directions, respectively.

[0023] determine whether there is arc abnormality according to the differential mode signal;

[0024] output an alarm signal if there is arc abnormality.

[0025] In another aspect, the present disclosure provides a photovoltaic power generation system, comprising:

[0026] a plurality of photovoltaic strings, each of which comprises a positive photovoltaic DC cable and a negative photovoltaic DC cable;

[0027] at least one MPPT connected to at least two photovoltaic strings;

[0028] at least one arc detection device as described above.

[0029] In some embodiments, the photovoltaic power generation system further comprises:

[0030] a bus capacitor connected to the at least one MPPT;

[0031] an inverter circuit connected to the bus capacitor;

[0032] a power grid connected to the inverter circuit.

[0033] The arc detection device provided by the present disclosure has the current detection assembly sleeved on the two photovoltaic DC cables of different photovoltaic string groups connected by the same MPPT, so that the currents on the two cables pass through the current detection assembly at the same time. Thus, the current detected by the current detection assembly is the differential mode signal of the currents on the two photovoltaic DC cables, and therefore the noise component can be automatically filtered out directly, and only the current generated by arc is retained, so that the detection accuracy is high. Moreover, the device has a simple structure and does not require an additional calculation module, so that the common mode component in the circuit is directly canceled from the hardware structure. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 a structural diagram of the arc detection device provided by the present disclosure;

[0035] Figure 2 a structural diagram of the current detection assembly in the arc detection device provided by the present disclosure;

[0036] Figure 3 a flowchart of the arc detection method provided by the present disclosure;

[0037] Figure 4 a structural diagram of the photovoltaic power generation system provided by the present disclosure Figure 1 ;

[0038] Figure 5 a structural diagram of the photovoltaic power generation system provided by the present disclosureFigure 2 . DETAILED DESCRIPTION

[0039] For the purpose of promoting the understanding of the present disclosure, the present disclosure will be more fully described by referring to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be realized in various 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 disclosure more thorough and comprehensive.

[0040] 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 in the description of the present disclosure herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. In the embodiments of the present disclosure, the terms "first", "second", "third", "fourth" are only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", "third", "fourth" can be explicitly or implicitly included one or more of the features.

[0041] In the description of the embodiments of the present disclosure, it should be noted that unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements.

[0042] The arc signal is similar to the white noise signal, and its energy is almost distributed in all frequency spectrums, showing the lifting of energy in different frequency bands. Because the on-site environment of the photovoltaic system is complex and changeable, multiple devices often work at the same time on the same line, and the frequent on-off of the switching power supply is easy to cause false lifting of the spectrum energy of the photovoltaic (PV) current signal of the inverter; the PV current mutation caused by the irradiation step of the photovoltaic site will also cause false lifting of the spectrum energy of the PV current signal; the false action of other direct current switches on the same line will also cause false lifting of the spectrum energy of the PV current signal, and further cause the whole machine to falsely report a direct current arc fault. How to filter out the interference signal and enhance the arc signal strength has become the key of the direct current arc detection.

[0043] The embodiments of the present disclosure provide an arc detection device, as shown in Figure 1 The arc detection device 100 includes:

[0044] The current detection assembly 110 is sleeved on the at least one pair of photovoltaic DC cables 210, and is configured to detect a differential mode signal on the at least one pair of photovoltaic DC cables 210; wherein one pair of the photovoltaic DC cables 210 includes a first cable 211 and a second cable 212 of the same polarity, the first cable 211 passes through the current detection assembly 110 in a direction opposite to that of the second cable 212; and the at least one pair of photovoltaic DC cables 210 belong to different photovoltaic strings connected to the same MPPT.

[0045] The arc detection assembly 110 can be used to detect the DC current, and is sleeved on the photovoltaic DC cable 210 to detect the current signal flowing through the photovoltaic DC cable 210. Here, the DC cables of different photovoltaic strings in the same MPPT are grouped, and each group can include a pair of photovoltaic DC cables 210, i.e., the first cable 211 and the second cable 212 of the same polarity in different photovoltaic strings connected to the same MPPT pass through the current detection assembly in opposite directions.

[0046] In some embodiments, each of the photovoltaic strings includes a positive cable and a negative cable; and the pair of photovoltaic DC cables are positive cables of two adjacent photovoltaic strings or negative cables of two adjacent photovoltaic strings.

[0047] It can be understood that the cause of the DC arc of the photovoltaic system is random, and the position and time of occurrence are unpredictable. Factors such as serious weathering of cable lines, damage of DC lines, aging of electronic components, loose connection contacts, or biting of animals can cause arc fault to occur. Various accidental factors make it impossible to accurately establish a mathematical model to directly determine whether the photovoltaic system has a DC arc fault.

[0048] The arc fault is usually accompanied by a sudden fault current, so the arc fault can be detected by current detection. However, for each photovoltaic branch cable of the same MPPT, there is a large common mode current, and pure current detection of the photovoltaic DC cable cannot exclude the influence of the common mode current, thereby easily causing false alarms.

[0049] Therefore, in the above scheme, by passing the photovoltaic DC cables 210 in pairs and in opposite directions through the current detection assembly 110, the detection of the differential mode signal is realized, which can effectively exclude the influence of the common mode signal.

[0050] It is worth noting that the current detection component 110 is sleeved on the plurality of photovoltaic DC cables 210 and cannot detect the current on each cable, nor does it affect the normal transmission of the current on each cable, but directly senses the differential mode signal in the photovoltaic DC cables 210. Compared with the way of calculating the differential mode signal by detecting the current on each DC cable respectively, the scheme provided by the embodiment of the application is easy to implement, simple and flexible, suitable for various structures of photovoltaic systems, does not require complex circuit connection, has low cost, and is convenient for adjusting and changing the layout of the cables.

[0051] In addition, since the generation of the arc signal has randomness, even if the arc occurs in the two photovoltaic DC cables at the same time, at least the existence of the arc abnormality in the photovoltaic DC cables can be detected through the above scheme, and therefore the detection accuracy is effectively improved.

[0052] In some embodiments, as shown in Figure 2 The current detection component 110 includes:

[0053] The electromagnetic induction unit 111 is configured to generate an induced magnetic field according to the differential mode signal on the at least one pair of photovoltaic DC cables 210 (for example, the first cable 211 and the second cable 212 as shown in Figure 1

[0054] The induced signal output unit 112 is configured to output a corresponding induced signal based on the induced magnetic field.

[0055] Since the electromagnetic induction unit can sense the magnetic field and the change of the magnetic field generated by the change of the current, 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 (that is, the induced current) through the induced magnetic field.

[0056] In this way, the induced signal indicates that there is a differential mode signal (or the differential mode signal is large enough) between the photovoltaic DC cables 210 to which the current detection component 110 is sleeved, and it can be judged whether there is an arc abnormality in the photovoltaic DC cables to which the current detection component 110 is sleeved.

[0057] It can be understood that if a current detection component is sleeved on only one pair of photovoltaic DC cables, when the differential mode signal (or the differential mode signal is large enough) is detected, it indicates that there is an arc abnormality in the two photovoltaic DC cables, so that the specific position of the arc occurrence can be more easily judged.

[0058] In some embodiments, the arc detection device further includes:

[0059] ​An arc alarm device is connected to the induction signal output unit, and is configured to determine whether an arc abnormality exists on the at least one pair of photovoltaic DC cables according to the induction signal, and output a corresponding alarm signal.

[0060] For example, when the differential mode signal detected by the current detection assembly is greater than a certain threshold, it can be considered that an arc abnormality exists, and then the arc alarm device can alarm or cut off the circuit, etc.

[0061] For example, the arc alarm device can be an alarm device of an acoustic, light or electrical signal, or a device that sends an alarm indication signal to a related computer system through computer instructions, or a switching device including a circuit breaker, etc.

[0062] In this way, the arc alarm device of the current detection assembly described above can achieve a rapid response to the arc abnormality, so that other processing systems or personnel can timely process the arc abnormality.

[0063] In some embodiments, the current detection assembly includes a current transformer.

[0064] The electromagnetic induction unit is a magnetic core of the current transformer, and the induction signal output unit is an induction winding of the current transformer; wherein the induction winding is wound on the magnetic core.

[0065] The current transformer is a commonly used current detection device using electromagnetic principles. The device can have a magnetic core sleeved on a cable. When a current change occurs on the cable, an induction magnetic field is generated. Since the induction winding is also wound on the magnetic core, based on the principle of electromagnetic induction, the induction magnetic field can also generate a corresponding induction current on the induction winding. In this way, the current generated on the cable can be calculated by detecting the induction current.

[0066] In the embodiments of the present application, since the cables sleeved in the magnetic core pass through in opposite directions in pairs, the common mode signal is cancelled, so that no induction magnetic field is generated. Only when the arc abnormality generates a differential mode signal, an induction magnetic field is generated on the magnetic core, and then an induction current is generated on the induction winding.

[0067] In this way, the presence or absence of an arc abnormality can be directly determined by detecting the induction current.

[0068] In some embodiments, the magnetic core is a ring-shaped magnetic core, and the first cable and the second cable pass through the ring-shaped magnetic core.

[0069] In some embodiments, the current detection assembly includes a Hall sensor.

[0070] The electromagnetic induction unit is a Hall device of the Hall sensor, and the induction signal output unit is a voltage output end connected to the Hall device.

[0071] The Hall sensor further comprises a current source connected across the Hall sensor for generating a current in the Hall device.

[0072] The at least one pair of photovoltaic DC cables is located adjacent to the Hall device, and the Hall device is used to sense an induced magnetic field generated by the differential mode signal.

[0073] The Hall sensor can detect the current by using the Hall effect. The Hall effect is an electromagnetic effect, specifically, when a solid conductor is placed in a magnetic field and passed by a current, the electric charge carriers in the conductor are deflected to one side by the Lorentz force, and then a Hall voltage is generated.

[0074] Since the arc signal generated on the above photovoltaic DC cable is a transient current signal, a corresponding magnetic field is generated. By using the Hall sensor to detect the magnetic field generated by the differential mode signal of the pair of photovoltaic DC cables, the detection of the differential mode signal can be realized.

[0075] Therefore, the Hall device can be placed adjacent to the at least one pair of photovoltaic DC cables, specifically, the Hall device can be arranged on a fixed ring and sleeved on the at least one pair of photovoltaic DC cables, so as to be located in the range of the magnetic field generated by the photovoltaic DC cables.

[0076] By using the current source, a current can be applied to one direction of the Hall device, and the voltage in the other direction can reflect the size of the magnetic field generated by the differential mode signal. Therefore, by detecting the voltage, the detection of the differential mode signal can be realized.

[0077] Based on the same inventive concept, the disclosure provides a method for detecting an arc, applied to any one of the arc detection devices, as shown in the above embodiments, the method comprises: Figure 3 The method comprises:

[0078] Step S101, detecting a differential mode signal on the at least one pair of photovoltaic DC cables; wherein a pair of the photovoltaic DC cables comprises a first cable and a second cable with the same polarity; the at least one pair of photovoltaic DC cables belongs to different photovoltaic strings connected to the same MPPT; the first cable and the second cable pass through the current detection assembly in opposite directions, respectively;

[0079] Step S102, determining whether there is an arc abnormality according to the differential mode signal;

[0080] Step S103, if there is an arc abnormality, outputting an alarm signal.

[0081] One of the implementation methods of the arc-drawing detection device is provided, that is, the current detection assembly in the arc-drawing detection device is used to directly detect the differential mode signal on the photovoltaic DC cables sleeved on the current detection assembly. The differential mode signal can be used to reflect whether there is an arc-drawing abnormality on the cables.

[0082] Exemplarily, a threshold value can be set. When the differential mode signal is greater than the threshold value, it is determined that there is an arc-drawing abnormality on the photovoltaic DC cables, and a corresponding alarm signal can be output for subsequent processing.

[0083] In this way, the arc-drawing detection device provided by the embodiments of the present application can simply and quickly detect whether there is an arc-drawing abnormality, and can effectively reduce false alarms caused by common mode interference, thereby improving the accuracy of arc-drawing detection.

[0084] Based on the same inventive concept, the embodiments of the present disclosure provide a photovoltaic power generation system, as shown in the accompanying drawings, the photovoltaic power generation system 400 comprises: Figure 4

[0085] a plurality of photovoltaic strings 410, each photovoltaic string 410 comprising a positive photovoltaic DC cable 411 and a negative photovoltaic DC cable 412;

[0086] at least one MPPT 420, the MPPT 420 being connected to at least two photovoltaic strings 410;

[0087] at least one arc-drawing detection device 100 as described above.

[0088] In some embodiments, as shown in the accompanying drawings, the photovoltaic power generation system 400 further comprises: Figure 5

[0089] a bus capacitor 430 connected to the at least one MPPT 420;

[0090] an inverter circuit 440 connected to the bus capacitor 430;

[0091] a power grid 450 connected to the inverter circuit 440.

[0092] ​​It should be understood that any reference to an "embodiment" or "one embodiment" or "an embodiment" of the application herein means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that the sequence of steps in the above-described processes is not meant to be limiting, and that the sequence of steps can be determined by the function and inherent logic of the steps, and should not be construed as limiting the embodiments of the application. The sequence of the above-described embodiments of the application is only for description, and does not represent the advantages or disadvantages of the embodiments.

[0093] It should be noted that, as used herein, the terms "includes," "including," or any variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements is not limited to those elements, but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the phrase "comprising a... " does not exclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0094] The above description is merely illustrative of the application, and the scope of the application is not limited thereto. Any modifications and replacements of the application that are apparent to those skilled in the art within the technical scope of the application are intended to be covered by the scope of the application.

Claims

1. An arc draw detection device, characterized by, include: A current sensing component is sleeved on at least one pair of photovoltaic DC cables for detecting differential mode signals on the at least one pair of photovoltaic DC cables; wherein, the pair of photovoltaic DC cables includes 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 at least one pair of photovoltaic DC cables belong to different photovoltaic strings connected to the same maximum power point tracking solar controller (MPPT).

2. The apparatus of claim 1, wherein, 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 at least one pair of photovoltaic DC cables; The induction signal output unit is used to output a corresponding induction signal based on the induction magnetic field.

3. The apparatus of claim 2, wherein, 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 at least one pair of photovoltaic DC cables based on the sensing signal, and to output a corresponding alarm signal.

4. The apparatus of claim 2, wherein, The current detection component includes: a current transformer; The electromagnetic induction unit is the magnetic core of the current transformer, and the induction signal output unit is the induction winding of the current transformer; wherein, the induction winding is wound around the magnetic core.

5. The apparatus of claim 4, wherein, The magnetic core is a toroidal core, and the first cable and the second cable pass through the toroidal core.

6. The apparatus of claim 2, wherein, The current detection component includes: a Hall sensor; The electromagnetic induction unit is the Hall device of the Hall sensor, and the induction signal output unit is the voltage output terminal connected to the Hall device. The Hall sensor also includes a current source connected to both ends of the Hall sensor to generate the current in the Hall device; The at least one pair of photovoltaic DC cables are located adjacent to the Hall device, which is used to sense the induced magnetic field generated by the differential mode signal.

7. The apparatus of any one of claims 1 to 6, wherein, Each of the photovoltaic strings includes a positive cable and a negative cable; a pair of photovoltaic DC cables can be either the positive cable of two adjacent photovoltaic strings or the negative cable of two adjacent photovoltaic strings.

8. An arc draw detection method, characterized by, Applied to the arc detection device as described in any one of claims 1 to 7, the method comprises: Detect differential mode signals on at least one pair of photovoltaic DC cables; wherein, one pair of photovoltaic DC cables includes a first cable and a second cable with the same polarity; the at least one pair of 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 component in opposite directions respectively; Based on the differential mode signal, determine whether there is an arcing abnormality; If an arcing abnormality is detected, an alarm signal will be output.

9. A photovoltaic power system, characterized by, 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; At least one arc detection device as described in any one of claims 1 to 7.

10. The photovoltaic power system of claim 9, wherein, 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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