CN118549766A - Arc detection device, arc detection method and photovoltaic power generation system - Google Patents

Abstract

The embodiments of the present disclosure disclose an arc detection device, an arc detection method and a photovoltaic power generation system. The arc detection device includes: at least two current detection components; wherein each current detection component is respectively sleeved on 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, and the direction in which the first cable passes through the current detection component is opposite to the direction in which the second cable passes through the current detection component; the two photovoltaic DC 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 a different cable.

Description

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

Technical Field

The embodiments of the present disclosure relate to the field of electric power technology, and relate to but are not limited to an arc detection device, an arc detection method, and a photovoltaic power generation system.

Background Art

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.

DC arc is a phenomenon of gas discharge near cables, that is, sparks are generated when current passes through insulating media such as air, and instantaneous current is generated in the cables at the same time, which can easily damage circuit components and cause system failures. 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.

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 they will cause great interference to arcing detection, resulting in inaccurate detection.

Summary of the invention

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

In one aspect, an embodiment of the present disclosure provides an arc detection device, comprising:

At least two current detection components; wherein each current detection component is respectively sleeved on two adjacent photovoltaic DC cables to detect 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, and the direction in which the first cable passes through the current detection component is opposite to the direction in which the second cable passes through the current detection component; the two photovoltaic DC cables belong to different photovoltaic strings connected to the same MPPT (Maximum Power Point Tracking, maximum power point tracking solar controller);

The first cable sleeved between every two adjacent current detection components is the same cable, and the second cables sleeved between every two adjacent current detection components are different cables.

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.

In some embodiments, each of the photovoltaic DC cables passes through adjacent current detection components, and the first photovoltaic DC cable and the last photovoltaic DC cable also pass through one current detection component.

In some embodiments, the current detection component includes:

An electromagnetic induction unit, used for generating an induced magnetic field according to the differential mode signals on the two photovoltaic DC cables;

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

In some embodiments, the arc detection device further includes:

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 two photovoltaic DC cables according to the sensing signal, and output a corresponding alarm signal.

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

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

On the other hand, an embodiment of the present disclosure further provides an arc detection method, which is applied to any of the above-mentioned arc detection devices, and the method includes:

At least two current detection components are used to respectively detect differential mode signals on two connected photovoltaic DC cables; wherein the two photovoltaic DC cables include a first cable and a second cable of 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;

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

In another aspect, the present disclosure also provides a photovoltaic power generation system, comprising:

A plurality of photovoltaic strings, each photovoltaic string comprising a positive photovoltaic DC cable and a negative photovoltaic DC cable;

At least one MPPT, the MPPT connected to at least two photovoltaic strings;

Any of the above arc detection devices.

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

A bus capacitor connected to the at least one MPPT;

An inverter circuit connected to the bus capacitor;

A power grid is connected to the inverter circuit.

The arc detection device provided in the embodiment of the present disclosure is used to sleeve the current detection component on two photovoltaic DC cables of different photovoltaic string groups connected to the same MPPT, so that the currents on the two cables pass through the current detection component at the same time. In this way, the current detected by the current detection component is a differential signal of the currents on the two photovoltaic DC cables, so the noise component can be directly and automatically filtered out, and only the current generated by the arc is retained, so the detection accuracy is high. In addition, the arc detection device provided in the embodiment of the present disclosure includes at least two current detection components, so that at least one cable passes through different current detection components. In this way, it is easy to locate which photovoltaic DC cable has an arcing abnormality, improve the accuracy of detection, and facilitate subsequent processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of an arc detection device provided in an embodiment of the present disclosure;

FIG2 is a schematic diagram of the structure of a current detection component connected to a cable in an arc detection device provided in an embodiment of the present disclosure;

FIG3 is a flow chart of an arc detection method provided by an embodiment of the present disclosure;

FIG4 is a first structural schematic diagram of a photovoltaic power generation system provided by an embodiment of the present disclosure;

FIG. 5 is a second structural schematic diagram of the photovoltaic power generation system provided in an embodiment of the present disclosure.

DETAILED DESCRIPTION

In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many 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 disclosure more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and/or" used herein includes any and all combinations of one or more related listed items. In the embodiments of the present application, 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 number of indicated technical features. Thus, the features defined as "first", "second", "third", "fourth" can explicitly or implicitly include one or more of the features.

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.

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.

The causes of DC arc in photovoltaic system are highly random, and the location and time of occurrence are unpredictable. Severe weathering of cable lines, damage of DC lines, aging of electronic components, loose connection contacts, or animal bites can all lead to arcing failures. Various accidental factors make it impossible to accurately establish a mathematical model to directly determine whether there is a DC arc fault in the photovoltaic system.

Arc faults are usually accompanied by sudden fault currents, so arc faults can be detected by current detection. However, for each photovoltaic branch cable of 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 cause false alarms.

The present disclosure provides an arc detection device, as shown in FIG1 , wherein the arc detection device 100 includes:

At least two current detection components 110; wherein each current detection component 110 is respectively sleeved on two adjacent photovoltaic DC cables 210, and is used to detect 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, and the direction in which the first cable passes through the current detection component is opposite to the direction in which the second cable passes through the current detection component; the two photovoltaic DC cables 210 belong to different photovoltaic strings connected to the same MPPT;

The first cable 211 sleeved between every two adjacent current detection components 110 is the same cable, and the second cables 212 sleeved between every two adjacent current detection components 110 are different cables.

For each current detection assembly 110, a pair of photovoltaic DC cables 210 with the same polarity and opposite directions can pass through the current detection assembly 110, and the pair of photovoltaic DC cables 210 is the first cable 211 and the second cable 212. The arc detection assembly 110 can be used to realize DC current detection, and it is sleeved on the photovoltaic DC cable 210, so that the current signal flowing through the photovoltaic DC cable 210 can be detected.

The current detection component 110 here is sleeved on the two 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 these photovoltaic DC cables 210. In other words, by passing the two photovoltaic DC cables 210 through the current detection component 110 in the opposite direction, the detection of the current differential mode signal is realized, which can effectively eliminate the influence of the common mode signal.

In this way, compared with the method of determining the differential signal by differential calculation of the current on each DC cable separately, the solution provided by the embodiment of the present application is easy to implement, simple and flexible, suitable for the structure of various photovoltaic systems, does not require complex circuit connections, is low in cost and easy to adjust and change the layout of the cables.

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, thereby effectively improving the accuracy of detection.

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

The arc detection device includes a plurality of current detection components, which can be sequentially connected to the photovoltaic DC cables corresponding to the same MPPT, and every two adjacent current detection components are connected to the same photovoltaic DC cable. For example, as shown in FIG2, one MPPT corresponds to three groups of photovoltaic strings, and the positive cables in each group of photovoltaic strings are used for arc detection, which are represented by cable PV1+, cable PV2+ and cable PV3+ respectively. In this way, the arc detection device can include two current detection components, wherein the current detection component 111 is respectively connected to the cable PV1+ and the cable PV2+, and the current detection component 112 is respectively connected to the cable PV2+ and the cable PV3+. In other words, the cable PV2+ is simultaneously connected to different current detection components. For the current detection component 111, the cable PV1+ belongs to the second cable, and the cable PV2+ belongs to the first cable. For the current detection component 112, the cable PV2+ belongs to the first cable, and the cable PV2+ belongs to the second cable.

In this way, when an arcing abnormality occurs on cable PV1+, only the current detection component 111 can detect a sufficiently large differential mode signal; when an arcing abnormality occurs on cable PV2+, both the current detection component 111 and the current detection component 112 can detect a sufficiently large differential mode signal; when an arcing abnormality occurs on cable PV3+, only the current detection component 112 can detect a sufficiently large differential mode signal.

In other words, this method can not only determine whether arcing anomalies have occurred in each photovoltaic string corresponding to the same MPPT, but also determine the specific cable where the arcing anomaly has occurred, thereby facilitating subsequent anomaly handling.

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.

In some embodiments, each of the photovoltaic DC cables passes through adjacent current detection components, and the first photovoltaic DC cable and the last photovoltaic DC cable also pass through one current detection component.

Two implementation methods of connecting the current detection component with different photovoltaic DC cables are provided here, namely, the case where n photovoltaic DC cables correspond to n-1 current detection components, and the case where n photovoltaic DC cables correspond to n current detection components.

The first case is the case of three cables and two current detection components as exemplified in the above embodiment. The location of the arcing anomaly can be achieved, but in this case, both the first cable and the last cable have only one current detection component for detection, which may result in false alarms.

The second case is to add an additional current detection component based on the first case to detect the differential mode signal on the first photovoltaic DC cable and the last photovoltaic DC cable. In this way, each photovoltaic DC cable has two current detection components for detection respectively, so that it can more accurately determine whether an arcing abnormality occurs and determine the specific cable location where the arcing abnormality occurs, further reducing the possibility of false alarms.

In some embodiments, the current detection component includes:

An electromagnetic induction unit, used for generating an induced magnetic field according to differential mode signals on two photovoltaic DC cables;

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

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.

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

In some embodiments, the arc detection device further includes:

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 two photovoltaic DC cables according to the sensing signal, and output a corresponding alarm signal.

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.

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.

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

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

A current transformer is a commonly used current detection device that uses the electromagnetic principle. The device can put a magnetic core on a cable. When the current in the cable changes, an induced magnetic field will be generated. Since an induction winding is also wound around the magnetic core, based on the principle of electromagnetic induction, the induced magnetic field can also generate a corresponding induced current on the induction winding. In this way, the current generated on the cable can be inferred by detecting the induced current.

In the embodiment of the present application, since the cables sleeved in the magnetic core are passed in pairs in opposite directions, the common mode signal is offset, so that no induced magnetic field is generated. Only when the arcing abnormality generates a differential mode signal, an induced magnetic field is generated on the magnetic core, and then an induced current is generated on the induction winding.

In this way, it is possible to directly determine whether there is an arcing abnormality by detecting the induced current.

Hall sensors can detect current using the Hall effect, which is an electromagnetic effect. Specifically, when a solid conductor is placed in a magnetic field and current passes through it, the charge carriers in the conductor are deflected to one side by the Lorentz force, which then generates a Hall voltage.

Since the arcing signal generated on the photovoltaic DC cable is an instantaneous current signal, a corresponding magnetic field is generated. The magnetic field generated by the differential mode signal of the paired photovoltaic DC cables can be detected by using a Hall sensor to detect the differential mode signal.

Therefore, the Hall device can be placed adjacent 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 within the range of the magnetic field generated by the photovoltaic DC cables.

By using a current source, a current can be applied to one direction of the Hall device, and the voltage in the other direction can reflect the magnitude of the magnetic field generated by the differential signal. Therefore, the differential signal can be detected by detecting the voltage.

Based on the same inventive concept, the embodiment of the present disclosure further provides an arc detection method, which is applied to any of the above arc detection devices. As shown in FIG3 , the method includes:

Step S101, using at least two current detection components to respectively detect differential mode signals on two connected photovoltaic DC cables; wherein the two photovoltaic DC cables include a first cable and a second cable of 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;

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

Here, one of the implementation methods for the specific application of the arc detection device is provided, that is, using the current detection component in the arc detection device to directly detect the differential mode signal on the two photovoltaic DC cables sleeved on the current detection component. This differential mode signal can be used to reflect whether there is an arc abnormality on the two cables.

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

Furthermore, since two adjacent current detection components are connected to the same photovoltaic DC cable, when an abnormal arc occurs in a photovoltaic DC cable, the two current detection components through which it passes will detect the abnormal arc. In this way, the specific cable with the abnormal arc can be accurately located.

It can be seen that by utilizing the 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, effectively reduce false alarms caused by common mode interference, and determine the specific cable where the arc abnormality occurs, thereby improving the accuracy of arc detection.

Based on the same inventive concept, the embodiment of the present disclosure further provides a photovoltaic power generation system, as shown in FIG4 , the photovoltaic power generation system 400 includes:

A plurality of photovoltaic strings 410, each photovoltaic string 410 includes a positive photovoltaic DC cable 411 and a negative photovoltaic DC cable 412;

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

Any of the arc detection devices 100 described above.

In some embodiments, as shown in FIG5 , the photovoltaic power generation system 400 further includes:

A bus capacitor 430 connected to the at least one MPPT 420;

An inverter circuit 440 connected to the bus capacitor 430;

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

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 disclosure. 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 may be combined in one or more embodiments in any suitable manner. It should be understood that in the various embodiments of the present disclosure, the size of the serial numbers 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 disclosure. The serial numbers of the embodiments of the present disclosure are for description only and do not represent the advantages and disadvantages of the embodiments.

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.

The above description is only an implementation mode of the present disclosure, but the protection scope of the present disclosure 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 disclosure, which should be included in the protection scope of the present disclosure.

Claims (10)

1. An arc discharge detection apparatus, comprising:

At least two current sensing components; each current detection component is sleeved on two adjacent paths of photovoltaic direct current cables respectively and is used for detecting differential mode signals on the two paths of photovoltaic direct current cables; the two paths of photovoltaic direct-current cables comprise a first cable and a second cable which are of the same polarity, and 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; the two paths of photovoltaic direct current cables belong to different photovoltaic group strings connected with the same Maximum Power Point Tracking (MPPT) of the solar controller;

the first cables sleeved by every two adjacent current detection assemblies are the same cable, and the second cables sleeved by every two adjacent current detection assemblies are different cables.

2. The apparatus of claim 1, wherein a first one of said photovoltaic dc cables passes through only one of said current sensing assemblies, a last one of said photovoltaic dc cables passes through only one of said current sensing assemblies, and each of said other photovoltaic dc cables passes through each of said adjacent two of said current sensing assemblies.

3. The apparatus of claim 1, wherein each of said photovoltaic dc cables passes through an adjacent one of said current sensing assemblies, and wherein a first of said photovoltaic dc cables and a last of said photovoltaic dc cables also pass through one of said current sensing assemblies.

4. The apparatus of claim 1, wherein the current detection assembly comprises:

The electromagnetic induction unit is used for generating an induction magnetic field according to differential mode signals on the two paths of photovoltaic direct-current cables;

And the induction signal output unit is used for outputting a corresponding induction signal based on the induction magnetic field.

5. The apparatus of claim 4, wherein the arcing detection apparatus further comprises:

And the arc discharge alarm device is connected with the induction signal output unit and is used for determining whether arc discharge abnormality exists on the two paths of photovoltaic direct current cables according to the induction signals and outputting corresponding alarm signals.

6. The apparatus of claim 3, wherein the current detection assembly comprises: current transformers and/or hall sensors.

7. The apparatus of any one of claims 1 to 6, wherein each of the photovoltaic strings comprises a positive cable and a negative cable; the two paths of photovoltaic direct current cables are positive cables of two adjacent photovoltaic group strings or negative cables of two adjacent photovoltaic group strings.

8. A method of detecting arc discharge, characterized by being applied to the arc discharge detecting apparatus according to any one of claims 1 to 7, the method comprising:

Respectively detecting differential mode signals on the two sleeved photovoltaic direct current cables by using at least two current detection assemblies; the two paths of photovoltaic direct current cables comprise a first cable and a second cable with the same polarity; the two paths of photovoltaic direct current cables belong to different photovoltaic group strings connected with the same MPPT; the first cable and the second cable respectively pass through the current detection assembly along opposite directions;

If at least two adjacent current detection assemblies detect the differential mode signal indicating abnormality, determining that arc discharge abnormality exists on the same path of photovoltaic direct current cable sleeved by the at least two adjacent current detection assemblies.

9. A photovoltaic power generation system, comprising:

Each photovoltaic group string comprises a positive photovoltaic direct current cable and a negative photovoltaic direct current cable;

At least one MPPT, the MPPT connects at least two photovoltaic strings;

the arc discharge detection apparatus according to any one of claims 1 to 7.

10. The photovoltaic power generation system of claim 9, further comprising:

the bus capacitor is connected with the at least one MPPT;

the inverter circuit is connected with the bus capacitor;

and the power grid is connected with the inverter circuit.