Anti-interference technology implementation method for cascade arc detection of battery packs

Abstract

This invention mainly relates to an anti-interference technology implementation method for arc detection in battery string cascades. Arc sensors for detecting DC arc faults are arranged at one or more photovoltaic modules in a battery string. The DC arc fault judgment result for each battery string is transmitted to a concentrator. The concentrator analyzes the DC arc fault judgment results transmitted from each battery string to determine whether the arc event is caused by an interference signal: if all arc sensors in all battery strings report a DC arc fault, the arc event is considered to be caused by an interference signal coupled to each battery string; if only some battery string arc sensors report a DC arc fault, while the arc sensors in the remaining battery string arc sensors do not report a DC arc fault, the arc event is considered not to be caused by an interference signal coupled to each battery string, thereby identifying the interference of interference signals on the arc event.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic power generation, and more particularly to a method for implementing an anti-interference technology for detecting an arc in a string of cells in a photovoltaic power generation system containing photovoltaic modules. BACKGROUND

[0002] With the shortage of traditional energy and the development of power technology, photovoltaic power generation has been paid more and more attention. Photovoltaic power generation systems must meet safety specifications in power applications. Arc is a gas discharge phenomenon, and the spark generated when current flows through an insulating medium such as air is a form of gas discharge. Detecting arc and actively taking measures are key elements to maintain photovoltaic power generation systems under safety specifications. Although the industry has tried to find the rules and commonalities of arc phenomena to seek accurate detection means of arc, it is difficult to avoid doubts that it is difficult to give a reasonable and strict detection mechanism for arc and to design a corresponding accurate detection instrument.

[0003] It is necessary to detect fault arc. Non-operational reasons such as aging and damage of line insulation or loose connection terminals in electrical lines often cause fault arc. The fault arc position will absorb most of the energy generated by the photovoltaic system and then convert it into high-temperature ionized gas. This continuous high-temperature gas will obviously burn the cable and electrical equipment. The large amount of heat released in a short time during fault arc discharge will also ignite other flammable and explosive materials near the photovoltaic system, causing local area disasters and unexpected power outages, posing a threat to property safety and personal safety.

[0004] Arcs can be roughly divided into DC arcs and AC arcs according to the nature of the current. The application time of AC is earlier and there are mature detection methods and commercial products for AC fault arc, but photovoltaic systems started relatively late and the essential characteristics of DC arc are different from AC. For example, DC current does not have the zero-crossing feature as AC, so the detection method of AC arc cannot be used in photovoltaic applications. The variables affecting the electrical properties of DC arc are originally diverse, and the different photovoltaic environments further complicate the arc. The industry generally recognizes that it is difficult to establish a mathematical model of DC arc. Although some arc models have been mentioned, these simplified models are usually based on the study of some single characteristics or a few very limited characteristics of the arc. In fact, the noise and occasional disturbances of the power system in the photovoltaic environment can easily mislead arc detection and cause false detection results. Dynamic changes in light intensity and environmental temperature and a large amount of switching noise are all sources of interference that can cause false negatives and false positives.

[0005] In summary, it is difficult to determine whether there is a real arc fault simply from the spectral characteristics of the arc because the spectral characteristics of the arc vary greatly: the main reason is that there is no consensus on the standard of the arc parameter characteristics as a comparison target, and it is not meaningful to establish a standard arc parameter characteristic; moreover, the actual detected current parameter information will inevitably have natural errors, which is the reason for not detecting the arc or false reporting the arc. SUMMARY

[0006] The application discloses an anti-interference technology implementation method for battery string cascade arc detection, wherein a plurality of battery strings are connected in parallel, and each battery string comprises a plurality of photovoltaic assemblies connected in series.

[0007] An arc sensor for detecting a direct-current arc fault is arranged at one or more photovoltaic assemblies of each battery string;

[0008] The direct-current arc fault judgment results of each battery string are transmitted to a concentrator, and the concentrator analyzes whether the arc event is caused by an interference signal according to the direct-current arc fault judgment results transmitted by each battery string:

[0009] If all the arc sensors of the battery strings reflect that a direct-current arc fault occurs, it is considered that the arc event is caused by the interference signal coupled to each battery string;

[0010] If only a part of the arc sensors of the battery strings reflect that a direct-current arc fault occurs, and the arc sensors of the remaining part of the battery strings do not reflect that a direct-current arc fault occurs, it is considered that the arc event is not caused by the interference signal coupled to each battery string, thereby identifying the interference of the interference signal on the arc event.

[0011] The method has the following characteristics: each parallelly connected battery string supplies power to an inverter, and one of the sources of the interference signal at least includes high-frequency harmonics generated by the inverter during the working stage.

[0012] The method has the following characteristics: the arc sensor of the battery string sends the direct-current arc fault judgment result provided by the battery string locally to the concentrator through power line carrier or wireless communication.

[0013] The method has the following characteristics: the arc sensor is integrated with a photovoltaic junction box, and the photovoltaic junction box is used to connect a single photovoltaic assembly to the battery string.

[0014] The method as claimed in the preceding claims, characterized in that the arc sensor is further integrated with a shutdown device for removing a single photovoltaic module from the battery string or for re-integrating a removed photovoltaic module into the battery string.

[0015] The method as claimed in the preceding claims, characterized in that the arc sensor is further integrated with a power optimizer for setting the photovoltaic module at its maximum power point.

[0016] The method as claimed in the preceding claims, characterized in that the arc sensor is further integrated with a voltage converter for performing a step-up voltage conversion or a step-down voltage conversion on the initial voltage of the photovoltaic module.

[0017] The method as claimed in the preceding claims, characterized in that the power supply to the busbar is provided by the individual battery strings, and if the arc event is not caused by the interference signal coupled to the individual battery strings, a switch provided on the busbar is switched to the off state by the concentrator control.

[0018] The application also relates to another anti-interference technology implementation method for battery string level arc detection, wherein a plurality of battery strings are connected in parallel, and each battery string comprises a plurality of photovoltaic modules connected in series, and the method is characterized in that:

[0019] DC arc faults at each battery string are monitored separately; and

[0020] DC arc faults at each battery string are analyzed collectively:

[0021] If all the battery strings have DC arc faults, the arc event is considered to be caused by the interference signal coupled to the individual battery strings;

[0022] If only part of the battery strings have DC arc faults, and the remaining part of the battery strings do not have DC arc faults, the arc event is considered not to be caused by the interference signal coupled to the individual battery strings.

[0023] The method as claimed in the preceding claims, characterized in that if the arc event is considered to be caused by the interference signal, the precondition is that all the parallel battery strings have DC arc faults with the same arc characteristics, and the same arc characteristics at least include that the arc signals at the individual battery strings fall in the same frequency band.

[0024] The application also relates to a battery string level arc detection method supporting anti-interference, which comprises the anti-interference technology implementation method for battery string level arc detection: the purpose is to identify the arc but eliminate the interference (such as eliminating the noise inevitably existing in the power generation link and the occasional interference on the DC side and the AC side), and the dynamic change of sunlight irradiance, temperature difference variable, and a large number of switching noise and harmonics existing in the inverter system are all interference sources of misjudgment and missed judgment. Attached Figure Description

[0025] To make the above-mentioned objectives, features and advantages more apparent and understandable, the specific embodiments are explained in detail below with reference to the accompanying drawings. After reading the following detailed description and referring to the following drawings, the features and advantages of this application will become obvious.

[0026] Figure 1 The photovoltaic modules are connected in series to supply power to the bus, and the bus is equipped with an energy harvesting device.

[0027] Figure 2 This is a schematic diagram illustrating an example of an arcing event caused by interference signals coupled to each battery string.

[0028] Figure 3 It transmits the DC arc fault judgment result corresponding to each battery string to a concentrator.

[0029] Figure 4 The photovoltaic module is equipped with a voltage converter to raise or lower the voltage of the photovoltaic module.

[0030] Figure 5 This is an example illustrating how the source of a DC arc fault can be an interference signal or a series or parallel arc.

[0031] Figure 6 The photovoltaic modules are connected to the busbar through a photovoltaic junction box equipped with a data acquisition module.

[0032] Figure 7 The photovoltaic modules are connected to the busbar via a shutdown device equipped with a data acquisition module.

[0033] Figure 8 The photovoltaic modules are connected to the busbar via a voltage converter equipped with a data acquisition module.

[0034] Figure 9 Information such as voltage, current, and arc of the photovoltaic modules is sent from the local equipment to the management equipment.

[0035] Figure 10 This is an example diagram illustrating how DC arc faults originate from interference signals and concurrent series and parallel arcs. Detailed Implementation

[0036] The present invention will be clearly and completely described below with reference to various embodiments. The described embodiments are only embodiments used for illustrative purposes and not all embodiments. Based on these embodiments, solutions obtained by those skilled in the art without creative effort are all within the protection scope of the present invention.

[0037] See Figure 1In optional examples, the battery string ST1-STM is taken as an example, M is a positive integer greater than 1, and a large number of battery strings are connected in parallel under a single inverter of a photovoltaic power station. The limited number of battery strings in the figure is only an example for explanation and does not constitute a specific limitation.

[0038] Referring to Figure 1 Each parallel battery string ST1-STM supplies power to the bus B1-B2. The energy management device 100 such as an inverter, a combiner box, or a charger receives power provided by each battery string from the bus.

[0039] Referring to Figure 1 In terms of component management of photovoltaic components: a plurality of photovoltaic components P1-PN supply power to the bus in series, and assuming that the bus includes a positive bus B1 and a negative bus B2, the positive electrode of one battery string of the plurality of photovoltaic components P1-PN in series is coupled to the so-called positive bus B1, and the negative electrode of the aforementioned battery string of the plurality of photovoltaic components P1-PN in series is coupled to the so-called negative bus B2. For example, each photovoltaic component is equipped with a photovoltaic junction box, which mainly functions to connect the power generated by the photovoltaic component to external lines in the photovoltaic system, and allows the photovoltaic junction box to have a bypass diode in some cases, which can bypass the abnormal photovoltaic component through the bypass diode of the photovoltaic junction box when abnormal generation of the photovoltaic component occurs, such as hot spot effect.

[0040] Referring to Figure 1 In the field of photovoltaic power generation, photovoltaic components, i.e. photovoltaic cells, are the core components for power generation. Solar panels are divided into single-crystal silicon cells, polycrystalline silicon solar cells, amorphous silicon solar cells, etc. in the mainstream technical direction. Large-scale centralized photovoltaic power stations use a large number of photovoltaic components, while small-scale distributed household small power stations use relatively few photovoltaic components. Silicon-based photovoltaic components have a service life of more than 20 years in the field, so real-time and long-term monitoring of photovoltaic components is essential. Many internal and external factors can cause low power generation efficiency of photovoltaic components, such as manufacturing differences or installation differences between photovoltaic components themselves or shadow shielding or maximum power tracking adaptation, etc. which can cause a decrease in component conversion efficiency.

[0041] Referring to Figure 1For example, if a part of the photovoltaic module is blocked by clouds or buildings or tree shadows or pollutants and the like, the part of the photovoltaic module will become a load instead of a power source and no longer generate electricity. The local temperature of the photovoltaic module at the location where the hot spot effect is serious is usually high, even exceeding 150 degrees Celsius, thereby causing the local area of the photovoltaic module to burn or form dark spots, the solder to melt, the package to age, the glass to burst, and corrosion and the like, which causes great hidden dangers to the long-term safety and reliability of the photovoltaic module. Therefore, it is particularly important to avoid the mismatch between the photovoltaic modules and it is more important to find and locate the fault in time.

[0042] Referring to Figure 1 , it is assumed that the photovoltaic module P1 is provided with a local device J1. In the present embodiment, it is assumed that the local device is a photovoltaic junction box, and then the positive electrode of the photovoltaic module P1 is connected to the positive bus B1 by the local device J1. According to the connection function of the photovoltaic junction box, the negative electrode of the photovoltaic module P1 is connected to the positive electrode of P2 by the local device J1. Similarly, the positive electrode of the photovoltaic module P2 is connected to the negative electrode of P1 by the local device J2, and the negative electrode of the photovoltaic module P2 is connected to the positive electrode of P3 by the local device J2 according to the connection function of the photovoltaic junction box. Similarly, the positive electrode of the photovoltaic module P3 is connected to the negative electrode of P2 by the local device J3, and the negative electrode of the photovoltaic module P3 is connected to the positive electrode of P4 by the local device J3 according to the connection function of the photovoltaic junction box. In this way, a plurality of photovoltaic modules are connected in series to form a battery string that can provide a higher voltage level. The connector between the photovoltaic module and the bus is also called a photovoltaic junction box (PV junction box).

[0043] Referring to Figure 2 , the management device 100 is taken as an example of an inverter INVT. The inverter INVT can convert the direct current on the bus into alternating current as required. It should be noted that the management device has a plurality of other alternative forms such as a combiner box or a battery charger for charging a battery. The inverter INVT is taken as an example of the energy management device for illustration.

[0044] Referring to Figure 2 , the inverter INVT has the following functions: The photovoltaic inverter mainly functions to convert the direct current generated by the photovoltaic module into alternating current in the photovoltaic system. In addition, the inverter also functions to detect the operating state of the module, the power grid, and the cable, communicate with the outside world, manage the system safety, and the like.

[0045] Referring to Figure 2In the photovoltaic industry standard NB32004-2013, there are more than 100 strict technical parameters for inverters, and each parameter must be qualified to be sold. The protection connection, contact current, power frequency withstand voltage of solid insulation, rated input and output, conversion efficiency, harmonic and waveform distortion, power factor, DC component, and AC output side over / under voltage protection of the photovoltaic grid-connected inverter product are tested.

[0046] Referring to Figure 2 The electricity is a sine wave alternating current, and the direction and size will periodically change. For example, the frequency of the alternating current is fifty hertz, and the waveform changing according to this frequency is called a fundamental wave. More than 97% of the power grid is the fundamental wave, and a part of it is a harmonic wave, which refers to the electric quantity contained in the current with a frequency that is an integer multiple of the fundamental frequency. The harmonic wave with a frequency that is twice the fundamental frequency is called a second harmonic wave, the harmonic wave with a frequency that is three times the fundamental frequency is called a third harmonic wave, and the harmonic wave with a frequency that is n times the fundamental frequency is called an n-th harmonic wave. In addition, it is also stipulated that those harmonic waves with a frequency that is an odd multiple of the fundamental frequency are collectively called odd harmonic waves, and those harmonic waves with a frequency that is an even multiple of the fundamental frequency are collectively called even harmonic waves.

[0047] Referring to Figure 2 The high-frequency harmonic bur of the inverter INVT is transmitted to the photovoltaic components through the DC bus or the branch line coupled to each photovoltaic component. The dashed line in the figure is the transmission path of the harmonic bur. The transmission path of the harmonic bur is taken as an example of the battery string ST1-ST M in the figure, and is transmitted to the photovoltaic components P1-PN of each string.

[0048] Referring to Figure 2 The harmonic wave (the harmonic bur transmitted to the photovoltaic components P1-PN) not only has no use but also causes serious harm. Most devices are applied to inductive devices, for example, and can only absorb the fundamental wave. The high-order harmonic wave will be converted into heat or vibration, causing the electrical equipment to overheat, generate vibration and noise, and age the insulation, shorten the service life, and even cause failure and burnout. In the process of power transmission, the harmonic wave consumes power and reduces the efficiency of power generation, transmission, and utilization due to the high frequency and the generated impedance. The harmonic bur is easy to be confused with the electric arc.

[0049] Referring to Figure 2 The harmonic wave (the harmonic bur transmitted to the photovoltaic components P1-PN) can cause local parallel resonance or series resonance of the power system, amplify the harmonic content, cause the built-in capacitor and other devices to burn out, or some devices in certain frequency bands cannot work normally. The harmonic wave can also cause misoperation of the relay protection and automatic shutdown, and cause disorder of the power metering. For the outside of the power system, the harmonic wave can cause serious interference to the communication equipment and electronic equipment.

[0050] Referring to Figure 2, the photovoltaic components P1-PN emit direct current, after the change of the inverter bridge, the voltage and current size and direction have changed, but it is not pure sine wave alternating current, the current and voltage are not continuous, containing a large number of harmonics and can be processed into pure sine wave alternating current, this process is filtering. The output harmonic of the photovoltaic inverter is divided into two parts, one of which is the high-order harmonic, mainly from the modulation method, and the other is the low-order harmonic, which comes from the switching dead zone effect and device parameter drift, sampling error, control parameter mismatch, etc.

[0051] Referring to Figure 2 , at one or more photovoltaic components P1-PN of each battery string, an arc sensor for detecting direct current arc faults is arranged, the arc sensor or arc fault sensor is a known technology, and any arc fault sensor related to the current technology can be directly used in the present application.

[0052] Referring to Figure 2 , the inverter INVT mainly suppresses harmonics from two aspects of hardware and software. The main purpose is to prevent the harmonic bur at the photovoltaic component P1-PN from being mistaken for an arc fault.

[0053] Referring to Figure 2 , the hardware of the inverter INVT is mainly a filter circuit, and the commonly used filtering methods of the inverter include using inductance or using inductance-capacitance or using inductance-capacitance-inductance (L, LC, LCL) combination mode. The main characteristic of inductance is that the current cannot be suddenly changed, and by using this characteristic, the discontinuous current of the inverter bridge can be converted into continuous current. The characteristic of the capacitor is that the voltage cannot be suddenly changed, and by using this characteristic, the discontinuous voltage of the inverter bridge can be converted into continuous voltage. The purpose of the hardware circuit is to prevent the harmonic bur at the photovoltaic component P1-PN from being mistaken for an arc fault.

[0054] Referring to Figure 2 , the software of the inverter INVT mainly includes the following aspects: improving the switching frequency, the harmonic cancellation ability of the parallel machine, and the software control technology for eliminating harmonics. The purpose of the software control is also to prevent the harmonic bur at the photovoltaic component P1-PN from being mistaken for an arc fault.

[0055] Referring to Figure 3, one of the inverter INVT software, improve the switching frequency: the higher the switching frequency of the inverter, the wider the control bandwidth for the full range of current harmonic suppression, to ensure stability, the control bandwidth of the inverter is usually about one tenth of the switching frequency. The output voltage in the inverter control algorithm is a sine wave, when the output pulse width modulation wave is distorted after the inverter modulation, it will affect the output harmonic and control effect of the inverter. Improving the switching frequency and the number of output pulse width modulation level can help reduce the distortion rate of pulse width modulation waveform.

[0056] See Figure 3 , the second inverter INVT software, and the harmonic cancellation ability: a square matrix of multiple groups of series inverters is different from the distance of the step-up transformer, and the line impedance will be different. The line impedance will change the inductance in the grid-connected LCL filter. Different filter parameters will change the phase of the harmonic. When multiple groups of series inverters work in parallel, the harmonic components will be partially cancelled due to the difference in phase, reducing the overall harmonic value of the system.

[0057] See Figure 3 , the third inverter INVT software, software control technology to eliminate harmonics: due to the use of high-speed digital processors in inverters, very complex algorithms such as repetitive current controller algorithms can be used. The principle is that any periodic signal can be decomposed into the sum of direct current, fundamental wave and each harmonic. As long as infinite gain is added to the forward channel of the control system at these frequencies, the command at these frequencies can be tracked without static error and disturbance suppression.

[0058] See Figure 3 , the main reason for the poor detection ability of traditional arc detection means: a set or multiple sets of fault arc parameter characteristics need to be developed first, and then the actual detected current parameter information is compared with the fault arc parameter characteristics. If the actual detected current parameter information meets the fault arc parameter characteristics, it is considered that a real arc event has occurred, otherwise, if the actual detected current parameter information does not meet the fault arc parameter characteristics, it is considered that a real arc event has not occurred. The biggest disadvantage is that each power system to be tested is different, and each inverter model to be tested is different, so the traditional fault arc detection means always has detection errors or even errors, which are almost irresistible.

[0059] See Figure 3, the inverter INVT mainly suppresses harmonics from the information collection and information processing aspects. The purpose is still to prevent the harmonics bur from being mistaken as arc fault at the photovoltaic modules P1-PN. This embodiment will replace the aforementioned inverter INVT which mainly suppresses harmonics from the hardware and software aspects. The starting point is that the inverter suppresses harmonics from the hardware and software aspects can only suppress, but cannot completely filter out all high-frequency harmonics. As long as there are harmonics, it will cause the arc sensor built-in in the local device J1 to mistakenly think that the harmonics bur is an arc (those harmonics with frequency of odd multiples of the fundamental frequency and those harmonics with frequency of even multiples of the fundamental frequency are the source of false triggering).

[0060] Referring to Figure 3 , the energy management device 100 is omitted in the figure but a concentrator 150 is given. Note that the energy management device is not removed from the power generation system, but is intentionally omitted based on the simplicity of the drawing. The purpose of the arc detection method of the battery string cascade in this example is to support anti-interference and prevent harmonics bur from being captured as an arc.

[0061] Referring to Figure 3 , the arc detection method supporting anti-interference, a plurality of battery strings ST1-STM are connected in parallel and each battery string includes a plurality of photovoltaic modules P1-PN connected in series, wherein: an arc sensor (integrated in the local device J1) for detecting direct current arc fault is arranged at one or more photovoltaic modules of each battery string; the direct current arc fault judgment result corresponding to each battery string is transmitted to the concentrator 150, and the concentrator 150 analyzes whether the arc event is caused by the interference signal (such as harmonics bur) according to the direct current arc fault judgment result transmitted by each battery string, and mainly in two aspects: if all the arc sensors of the battery strings ST1-STM reflect that a direct current arc fault occurs, it is considered that the arc event is caused by the interference signal coupled to each battery string ST1-STM; if only a part of the arc sensors of the battery strings (such as ST1-ST2) reflect that a direct current arc fault occurs locally, and the arc sensors of the remaining part of the battery strings (such as STM, etc.) do not reflect that a direct current arc fault occurs locally, it is considered that the arc event is not caused by the interference signal coupled to each battery string ST1-STM, thereby distinguishing the interference of the interference signal to the arc event.

[0062] Referring to Figure 3 , each local device J1-JN of the battery string ST1 transmits the direct current arc fault judgment result of each photovoltaic module P1-PN to the concentrator 150.

[0063] Referring to Figure 3The local devices J1-JN of each battery string ST2 send the DC arc fault detection results of the respective photovoltaic modules P1-PN to the concentrator 150.

[0064] Referring to Figure 3 The local devices J1-JN of each battery string STM send the DC arc fault detection results of the respective photovoltaic modules P1-PN to the concentrator 150.

[0065] Referring to Figure 3 The photovoltaic module PN is equipped with a local device JN. In this embodiment, it is assumed that the local device is a photovoltaic junction box. The positive pole of the photovoltaic module PN is connected to the negative pole of PN-1 by the local device JN, and the negative pole of the photovoltaic module PN is connected to the negative bus B2 according to the connection function of the photovoltaic junction box. In this way, it can be known that different photovoltaic modules are in series and different local devices are also in series, where N is a positive integer greater than 1.

[0066] Referring to Figure 4 In an optional embodiment, a plurality of battery strings can be connected in parallel, and each battery string includes a plurality of photovoltaic modules P1-PN connected in series. Each photovoltaic module is configured with a local device receiving its output power. For example, the photovoltaic module P1 is configured with a local device J1 receiving the output power of P1, and other photovoltaic modules PN are configured with a local device JN receiving the output power of PN. The plurality of local devices J1-JN corresponding to the plurality of photovoltaic modules P1-PN under any battery string are connected in series by cables. The cables are usually conductive cables or power lines or power supply lines, etc. In this embodiment, the positive output end of the local device J1 is connected to the positive bus B1, and the negative output end of the local device JN is connected to the negative bus B2. The output power of each photovoltaic module is converted by its corresponding local device or not converted, and the output power of the plurality of photovoltaic modules is aggregated together and sent to the energy collection device mentioned below by the series-connected local devices.

[0067] Referring to Figure 4 The voltage of the first-stage photovoltaic module P1 is V1. Similarly, the voltage of the second-stage photovoltaic module P2 is V2. In this way, the voltage of the Nth-stage photovoltaic module PN is VN. The total bus voltage provided by any group of photovoltaic modules is approximately V BUS which is equal to V1+V2+V3+…VN. The output power of each multi-stage photovoltaic module is superimposed on the bus, and the power collected by the bus is much higher than that of a single photovoltaic module.

[0068] Referring to Figure 4The local device J1 is a photovoltaic junction box in this embodiment. The partial voltage V1 outputted by the photovoltaic assembly P1 to the cable can be characterized by the output voltage of the local device J1, and the branch current outputted by the photovoltaic assembly P1 to the cable can be characterized by the output current I1 of the local device J1. The same is true for the local device JN. For example, the partial voltage VN outputted by the photovoltaic assembly PN to the cable can be characterized by the output voltage of the local device JN, and the branch current outputted by the photovoltaic assembly PN to the cable can be characterized by the output current IN of the local device JN, which is the characteristic of the junction box. The cable is sometimes referred to as a busbar.

[0069] Referring to Figure 4 In an optional embodiment, a plurality of local devices J1-JN corresponding to a plurality of photovoltaic assemblies P1-PN of a battery string are connected in series, the output current of the local device J1 configured by the monitored photovoltaic assembly P1 characterizes the branch current I1 supplied by the photovoltaic assembly P1 to the cable, the output current of the local device J2 configured by the photovoltaic assembly P2 characterizes the branch current I2 supplied by the photovoltaic assembly P2 to the cable, the output current of the local device JN configured by the photovoltaic assembly PN characterizes the branch current IN supplied by the photovoltaic assembly PN to the cable, and so on.

[0070] Referring to Figure 4 Suppose the local device is a voltage converter, for example, a voltage converter is configured for each of the multi-stage photovoltaic assemblies P1-PN, and meanwhile the output power of the plurality of voltage converters corresponding to the multi-stage photovoltaic assemblies P1-PN is required to be superimposed on the DC busbar and thereby serve as the busbar power. At this time, the plurality of voltage converters are connected in series with each other. The local device J1, such as a voltage converter, converts the electrical energy extracted from the photovoltaic assembly P1 corresponding thereto into its own output power, and the local device J1, such as a voltage converter, also performs voltage boosting, voltage bucking, or voltage buck-boosting, etc. on the initial voltage of the photovoltaic assembly P1 corresponding thereto before outputting. The voltage converter, i.e. the DC / DC converter, can be a voltage converter of the boost type or a boost-type switching power supply, a voltage converter of the buck type or a buck-type switching power supply, or a voltage converter of the buck-boost type or a buck-boost-type switching power supply. The local device has voltage regulation functions of boosting or bucking. By the same token, the remaining other local devices JN, such as voltage converters, convert the electrical energy extracted from the photovoltaic assembly PN corresponding thereto into their own output power, and the local devices JN, such as voltage converters, also perform voltage boosting, voltage bucking, or voltage buck-boosting, etc. on the initial voltage of the photovoltaic assembly PN corresponding thereto before outputting.

[0071] Referring to Figure 5The local device is a voltage converter that performs voltage conversion on the initial voltage of the component. In the series relationship, the partial voltage provided by the first-stage photovoltaic component P1 to the cable is represented by the output voltage V1 of the local device J1, and the branch current provided by the first-stage photovoltaic component to the cable is represented by the output current I1 of the local device J1. The output voltage V1 is the voltage output by the converter, i.e., the local device J1, after performing conversion such as voltage boosting or voltage dropping. In this example, the local device J1 is a voltage converter that performs voltage conversion on the initial voltage of the photovoltaic component P1. In this example, the output voltage V1 can be higher than or lower than the initial voltage output by the corresponding photovoltaic component P1. A set of output terminals of the voltage converter, i.e., the positive output terminal and the negative output terminal of the local device J1, are often connected with a capacitor to ensure that the output voltage of the voltage converter is relatively smooth and the ripple is reduced. The local device or the positive output terminal and the negative output terminal of the local device below can be replaced by the terms first output terminal and second output terminal, respectively.

[0072] Referring to Figure 5 The local device is a voltage converter that performs voltage conversion on the initial voltage of the component. In the series relationship, the partial voltage provided by the first-stage photovoltaic component P1 to the cable is represented by the output voltage V1 of the local device J1, and the branch current provided by the first-stage photovoltaic component to the cable is represented by the output current I1 of the local device J1. The output voltage V1 is the voltage output by the converter, i.e., the local device J1, after performing conversion such as voltage boosting or voltage dropping. In this example, the local device J1 is a voltage converter that performs voltage conversion on the initial voltage of the photovoltaic component P1. In this example, the output voltage V1 can be higher than or lower than the initial voltage output by the corresponding photovoltaic component P1. A set of output terminals of the voltage converter, i.e., the positive output terminal and the negative output terminal of the local device J1, are often connected with a capacitor to ensure that the output voltage of the voltage converter is relatively smooth and the ripple is reduced. The local device or the positive output terminal and the negative output terminal of the local device below can be replaced by the terms first output terminal and second output terminal, respectively.

[0073] Referring to Figure 5 It is assumed that the output voltage of the local device J1 is V1. Similarly, it is assumed that the output voltage output by the local device J2 is V2. In this way, the output voltage of the Nth-stage local device JN is VN. The total bus voltage that can be provided by any set of photovoltaic components is approximately V BUS which is equal to V1+V2+V3+…VN. The output power of each of the multi-stage photovoltaic components is superimposed on the bus, and the power collected by the bus is much higher than that of a single photovoltaic component.

[0074] Referring to Figure 6 The harmonic bur will be mixed into each of the output voltages V1 to VN. Therefore, even if the output voltage of the voltage converter is detected to identify the arc, an incorrect detection result can be obtained.

[0075] Referring to Figure 6The energy collection devices used by the management device 100, in addition to the inverter INVT, can also be other energy collection devices, such as a combiner box CB that typically collects energy from photovoltaic modules, and the like, and can also be various chargers or boost converters that charge storage batteries, and the like. The management device can use a boost converter to raise the voltage level of the bus, and then invert the bus voltage at the higher voltage level.

[0076] Referring to Figure 6 The multiple strings of batteries are connected in parallel and each string includes multiple photovoltaic modules connected in series by cables, such as the first string ST1 shown in the upper half of the figure that includes multiple photovoltaic modules P1-PN connected in series by cables, and the second string ST2 shown in the lower half of the figure that includes multiple photovoltaic modules P1-PN connected in series by cables. Many more parallel strings of batteries are not shown in the figure.

[0077] Referring to Figure 6 The harmonic bur can mix into each of the photovoltaic modules P1-PN. At the same time, parallel arcs can occur between different strings of batteries, such as between the strings ST1 and ST2, and cause complexity in arc recognition because the parallel arc 80 and the harmonic bur can be at the same frequency. At the same time, series arcs can occur at each of the locations of the local devices J1-JN, and without doubt, the presence of series and parallel arcs and high frequency harmonics or various interference signals, causes arc recognition to be extremely difficult.

[0078] Referring to Figure 6The data acquisition module is configured to acquire one or more target data of the PV module. The target data acquired by the data acquisition module can include, for example, the initial voltage and the initial current of the PV module, the output voltage or the output current of the local device output to the busbar. The data acquisition module can use a voltage detection module such as a voltage detector VT or a voltage sensor to detect the initial voltage of the PV module, and use a voltage detection module such as a voltage detector VT or a voltage sensor to detect the output voltage of the local device. The data acquisition module can use a current detection module such as a current detector CT or a current sensor to detect the initial current of the PV module, and use a current detection module such as a current detector CT or a current sensor to detect the output current of the local device. The initial voltage and the initial current of the PV module are delivered to the local device, and the output voltage and the output current of the local device are delivered to the cable. The data acquisition module can also include a temperature sensor for monitoring the ambient temperature of the PV module, or a light radiation meter for monitoring the effective illumination of the sunlight in the surrounding environment of the PV module. The target data can also be referred to as working parameters, and the data types thereof include, but are not limited to, the voltage, the current, the temperature, the output power, the effective light radiation, and the like of the PV module. The branch current provided by each monitored PV module to the cable is actually the output current of the local device configured by the monitored PV module, which represents the branch current provided by the monitored PV module to the cable.

[0079] Referring to Figure 6 The arc signal is a type of data, and thus the data acquisition module is configured to acquire one or more target data of the PV module, and the target data includes the arc data. In an optional embodiment, the data acquisition module includes an arc sensor or an arc fault sensor. The arc sensor can be integrated with the PV junction box (e.g., JN), and the PV junction box (e.g., JN) can be used to connect the PV module PN to the battery string STM. The arc sensor, which is not shown, is configured to detect the arc condition at the PV module PN.

[0080] Referring to Figure 6The local devices J1 to JN comprise a current detection module, such as the current detector CT or a current sensor mentioned above, to detect the output current of the photovoltaic module or the local device. For example, the branch current I1 provided by each monitored photovoltaic module, such as P1, to the cable is measured in any string of cells. Since the photovoltaic module P1 is not directly connected to the cable but is indirectly connected to the cable through the local device J1, the branch current provided by the photovoltaic module P1 to the cable is represented by the output current I1 of the local device J1. The initial current and the initial voltage of the photovoltaic module P1 are delivered to the local device J1 and the output power of P1 is received by the local device J1. For another example, the branch current IN provided by each monitored photovoltaic module, such as PN, to the cable is measured in the string of cells. Since the photovoltaic module PN is not directly connected to the cable but is indirectly connected to the cable through the local device JN, the branch current provided by the photovoltaic module PN to the cable is represented by the output current IN of the local device JN. The initial current and the initial voltage of the photovoltaic module PN are delivered to the local device JN and the output power of PN is received by the local device JN

[0081] Referring to Figure 6The local device JN includes a controller IC1. Currently, many types of controllers IC1 are equipped with data acquisition modules that can collect the aforementioned target data. For example, the controller IC1 is also called a microprocessor and allows it to be equipped with temperature sensors or voltage and current detection modules, etc. If the controller IC1 does not have a data acquisition module, an additional data acquisition module can be configured for it to collect target data. Generally, after the controller IC1 learns the parameter information such as target data, it can send the target data out through the control of the communication module CM1. The communication mechanism of the communication module CM1 includes two types of wired communication and wireless communication: for example, WIFI, ZIGBEE, 433MHZ communication, and infrared or Bluetooth, etc. all existing wireless communication solutions, and for example, deliberately adopt the power line carrier communication solution. In the optional embodiment of the present application, the communication module CM1 in the figure includes a power line carrier modulator, which transmits the target data to the data receiver in the form of a power line carrier. The coupling element 10 in the figure couples the power line carrier modulator to the busbar, for example, a transformer with a primary and secondary winding or a signal coupler with a coupling coil. For example, the method of using the coupling transformer can deliver the power line carrier to the primary winding, and the secondary winding is connected to the busbar or busbar branch as part of the busbar, and the carrier is transmitted to the busbar through the coupling of the primary and secondary windings. For example, the typical use method of the signal coupler with a magnetic ring and a coupling coil can directly pass the busbar or busbar branch through the magnetic ring with the coupling coil, and the power line carrier is delivered to the coupling coil and can be inductively coupled from the power supply busbar to implement non-contact signal transmission. In summary, the coupling element can use all signal coupling solutions disclosed in the prior art, such as injection inductive coupler technology, cable clamping inductive coupler technology, and switchable full impedance matching cable clamping inductive coupler. The general principle is that the controller delivers the target data to the communication module, and the communication module transmits the target data to the data receiver through wired or wireless means.

[0082] Referring to Figure 6 As for wired communication and wireless communication, considering that the photovoltaic assembly is located in a relatively harsh location such as the roof of a building or a desert or a wild mountainous area, wireless communication usually brings higher additional cost and is at a disadvantage in terms of long-term reliability. After all, the general service life of photovoltaic assemblies is more than twenty years, so the communication between the master node and the slave node and between the slave nodes adopts power line carrier. Different local devices allow different frequencies of power line carrier signals, but wireless communication is also an option.

[0083] Referring to Figure 6, concentrator 150 comprises a controller IC2 and a communication module CM2, and also allows a carrier signal coupling element 20 to be provided for sensing the power line carrier signal from the busbar, noting that the local device is to transmit and load the power line carrier signal onto the busbar or cable at the photovoltaic module, while the concentrator is to sense and capture the power line carrier signal returned from the cable to the concentrator. The communication module and the coupling element are sometimes integrated together, such as they comprise any one of the types of a Rogowski coil sensor or a high-frequency sensor, a codec or a shunt, etc. It is worth clarifying that the local device also has the data receiving function of wired or wireless communication as the concentrator. Likewise, the concentrator also has the data transmitting function of wired or wireless communication as the local device. For example, the concentrator actively polls different local devices and requires each local device to return the target data collected and saved by itself to the concentrator when the local device receives the polling signal, and the concentrator is equivalent to a master node while each local device is equivalent to a slave node. The local device is explained and described in the photovoltaic junction box as an optional example in this example, and of course the wired communication function and the wireless communication function of the local device and the concentrator mentioned above are also applicable to this example.

[0084] Referring to Figure 6 , concentrator 150 can be directly integrated inside energy management device 100. Concentrator 150 can also be separately provided without being integrated with energy management device 100.

[0085] Referring to Figure 7 to Figure 8 , concentrator 150 has the current detection module mentioned above, such as a conventional current detector CT or a current sensor, etc., to detect the string current IS of the battery string. The string current is the current flowing through the battery string and is also the current flowing through each photovoltaic module P1 to PN or the current flowing through each local device J1 to JN.

[0086] Referring to Figure 7 , after concentrator 150 and each local device J1 to JN establish a communication mechanism, the branch current provided by each photovoltaic module to the cable is transmitted by the local device configured for the photovoltaic module to concentrator 150, and one of the core tasks of concentrator 150 is to determine whether a fault, such as an arc fault, occurs at each photovoltaic module.

[0087] Referring to Figure 1-6 , this example is taken as an example of a photovoltaic junction box. The photovoltaic junction box can be replaced by a shutdown device that disconnects the photovoltaic module from the cable or restores the photovoltaic module in a disconnected state to the cable, the photovoltaic junction box can be replaced by a power optimizer that sets the photovoltaic module at the maximum power point, and the photovoltaic junction box can be replaced by a voltage converter that can perform voltage conversion on the initial voltage of the photovoltaic module. Figure 7 The technical solutions of the application are applicable to Figure 7 the example.

[0088] Referring to Figure 7 In the context of a shutdown device supporting fast shutdown management of a photovoltaic module, a local device JN, such as a shutdown device, is used to control whether a photovoltaic module is shutdown or not as shown in the figure. The shutdown management goal of the circuit of the local device JN, such as a shutdown device, is to determine whether it is necessary to timely shutdown a photovoltaic module: a photovoltaic system installed or built-in a building must include a fast shutdown function to reduce the risk of electric shock to emergency personnel. Although the component shutdown device is described as an example of a component shutdown device that implements a shutdown function, in fact the component shutdown device at least integrates a data acquisition function and a component shutdown function in function. Explanation of the component shutdown function: the local device JN, such as a shutdown device, can disconnect the photovoltaic module PN corresponding to it from the cable and stop supplying power to the bus, or the local device JN, such as a shutdown device, or the photovoltaic module PN in the disconnected state is restored to access the cable and supply power to the bus again. For example, the positive output end of the local device J1 is connected to the positive bus B1, and the negative output end of the local device JN is connected to the negative bus B2. And the positive output end of the last local device in the series of local devices is connected to the negative output end of the adjacent previous local device, or the positive output end of the last local device in the multi-stage local device is connected to the negative output end of the adjacent previous local device, thereby connecting a plurality of local devices in series to form a battery string. Each photovoltaic module in the battery string is configured with a local device that receives its output power, for example, any photovoltaic module PN in the battery string is configured with a local device JN that receives its PN output power, and a plurality of photovoltaic modules P1 to PN under any battery string correspond to a plurality of local devices connected in series through a cable, for example, J1 to JN in series. The connection relationship of the local device here is applicable Figure 7 to the example.

[0089] Referring to Figure 8 The arc sensor can be integrated with the shutdown device (such as JN), and at this time the shutdown device is used to remove the single photovoltaic module PN from the battery string STM, or the photovoltaic module PN in the removed state is restored to access the battery string STM. The unillustrated arc sensor is used to detect the arc at the photovoltaic module.

[0090] Referring to Figure 8A bypass diode or a complementary switch can be arranged between the positive output (first output) and the negative output (second output) of the local device JN. The complementary switch is a switch that is complementary to switch S1: if switch S1 is on, then its complementary switch is off and if switch S1 is off, then its complementary switch is on. The purpose of arranging a bypass diode or a complementary switch is to prevent the battery string from being open-circuited at the local device JN. If the photovoltaic module PN is disconnected, the bypass diode or the complementary switch of the local device JN is turned on. If the photovoltaic module PN is reconnected to the cable or said to be reconnected to the battery string, the bypass diode or the complementary switch is turned off.

[0091] Referring to Figure 8 The local device JN sets a switch S1 between the negative electrode of the photovoltaic module PN and the conductive cable or alternatively sets a switch S1 between the positive electrode of the photovoltaic module PN and the conductive cable. The local device JN collects one or more target data of the photovoltaic module through the data acquisition module, and if the target data is found to be abnormal, the controller IC1 can be controlled to shut down the photovoltaic module PN, for example, the controller IC1 operates to turn off the switch S1, whether the initial voltage or the initial current of the photovoltaic module is abnormal or the output voltage or the output current of the local device to the cable is abnormal, the controller IC1 can drive or control the switch S1 to be turned off. Based on the communication mechanism established between the local device and the management device, if the instruction sent by the concentrator 150 to the local device JN includes a shutdown instruction, the local device will also actively drive or control the switch S1 to be turned off when receiving such an instruction. At the same time, in other optional embodiments, shutdown management is also supported, for example, the local device J1 supporting fast shutdown of the photovoltaic module P1 is used to operate the off or on of the shutdown switch S1 configured for the photovoltaic module to control whether the photovoltaic module P1 is shut down. By analogy, other optional examples also support shutdown management, for example, the local device J2 supporting fast shutdown of the photovoltaic module P2 is used to operate the off or on of the shutdown switch S1 configured for the photovoltaic module to control whether the photovoltaic module P2 is shut down. The local device in this example is explained as an optional example of a shutdown device, of course, the wired communication function and the wireless communication function of the local device and the concentrator provided in the foregoing are also applicable to this example, and the local device and the concentrator both have bidirectional communication capability. The shutdown device removes the photovoltaic module from the battery string or re-connects the photovoltaic module in the removed state to the battery string.

[0092] Referring to Figure 8The concentrator 150 reads the target data of each photovoltaic module P1-PN such as voltage fed to the cable and branch current fed to the cable in the following way: the concentrator 150 polls the series of local devices J1-JN in turn, and when the concentrator 150 polls any one local device such as JN, the polled local device such as JN returns the target data of the corresponding photovoltaic module PN to the concentrator 150. Now take an example to illustrate this data reading method: when the controller IC2 of the concentrator 150 polls the local device such as J1, the controller IC1 of the polled local device such as J1 returns the target data of the photovoltaic module P1 to the controller IC2. Continue to take an example to illustrate this data reading method: when the controller IC2 of the concentrator 150 polls the local device such as J2, the controller IC1 of the polled local device such as J2 returns the target data of the photovoltaic module P2 to the controller IC2. In general, this data reading can be considered as: the controller configured by the concentrator, i.e. the master node, polls the controller configured by each local device, i.e. the slave node, in turn, and when the concentrator polls any one local device, the controller of the polled local device returns the target data of the corresponding photovoltaic module such as voltage fed to the cable and branch current fed to the cable to the controller configured by the concentrator. In order to avoid confusion, the controller of the local device can be called the first controller, and its communication module can be called the first communication module, while the controller of the concentrator can be called the second controller, and its communication module can be called the second communication module. Other alternatives of the controller are: field programmable logic gate array or complex programmable logic device or field programmable analog gate array or semi-custom ASIC or processor or microprocessor or digital signal processor or integrated circuit or software firmware program stored in memory, etc. The aforementioned polling data reading method is applicable not only to the photovoltaic junction box shown in the figure, but also to the shutdown device or power optimizer or voltage converter, etc.

[0093] Referring to Figure 8Each photovoltaic (PV) module in the P1-PN series is equipped with a voltage converter, also known as a switching regulator, and is most commonly found in switching power supply circuit topologies such as buck converters, boost converters, and buck-boost converters. The controller IC1 of the local device JN is often designed as a driver chip. The controller drives the voltage converter or conversion circuit to convert the input voltage drawn from the PV module P1 into an output voltage. The voltage converter is also called a power stage circuit, and the controller IC1 is also called a power controller. The most common applications of controller IC1 in the industry are various power management controllers or power management chips that manage switching power supplies. This example allows the local device to simply perform basic buck or boost conversion on the initial voltage of the PV module. For example, the output voltage of the local device can be considered as the voltage supplied by the PV module to the bus, while the initial voltage of the PV module is supplied to the local device, and the output voltage of the local device is the voltage obtained by bucking or boosting the initial voltage of the PV module. In this case, the local device does not require power optimization.

[0094] See Figure 8 The arc sensor is integrated with a voltage converter (such as JN), which is used to perform boost or buck voltage conversion on the initial voltage of the photovoltaic module PN. An arc sensor (not shown) is used to detect arcs at the photovoltaic module.

[0095] See Figure 8 A significant concern in distributed or centralized photovoltaic (PV) power plants is the mismatch between numerous PV modules caused by shading. Another issue is that the output characteristics of PV modules, particularly their output voltage and current, are closely related to external factors such as light intensity and ambient temperature. The uncertainty of these external factors causes the maximum output power and the voltage corresponding to the maximum power point to change accordingly. For example, the power output of PV modules exhibits randomness and significant fluctuations. This random and uncontrollable characteristic has a high probability of causing substantial impacts on the power grid and potentially negatively affecting the operation of critical loads. Based on these concerns, achieving maximum power point tracking (MPPT) for PV modules while considering external factors is a core objective for the industry in maximizing energy efficiency and profitability.

[0096] See Figure 9The principles and characteristics of commonly used MPPT methods for power optimization: Early methods for controlling the output power of photovoltaic modules primarily utilized Constant Voltage Tracking (CVT). This tracking method ignores the influence of temperature on the open-circuit voltage of solar cells, leading to the development of open-circuit voltage and short-circuit current methods. These methods essentially approximate the maximum power point (MPP). To more accurately capture the MPP, perturbation-observation, duty cycle perturbation, and even incremental conductance methods have been proposed. The perturbation-observation method measures the current array power and then adds a small voltage component perturbation to the original output voltage. The output power changes, and by measuring the changed power and comparing the magnitudes before and after the change, the direction of the power change can be determined. If the power increases, the original perturbation is continued; if it decreases, the original perturbation direction is changed. The duty cycle perturbation method works as follows: The interface between the photovoltaic array and the load typically uses a voltage converter controlled by a pulse width modulation (PWM) signal. Adjusting the duty cycle of the PWM signal regulates the input-output relationship of the converter, achieving impedance matching. Therefore, the duty cycle essentially determines the output power of the photovoltaic cells. The incremental conductance method and the aforementioned perturbation observation method can be considered to achieve the same goal through different means. The biggest difference lies only in the logic judgment formula and measurement parameters. Although the incremental conductance method still aims to achieve the maximum power point by changing the output voltage of the photovoltaic cell, it reduces the oscillation phenomenon near the maximum power point by modifying the logic judgment formula, making it adaptable to climates with rapidly changing solar intensity and temperature. Actual measurement methods, fuzzy logic methods, power mathematical models, intermittent scanning tracking methods, and optimal gradient methods or three-point centroid comparison methods are less commonly used maximum power point tracking methods. From this, it can be seen that the so-called MPPT algorithms used in the photovoltaic energy industry are diverse, which will not be repeated in this application.

[0097] See Figure 9Each photovoltaic (PV) module in the P1-PN series is equipped with a voltage converter. However, this voltage converter is not just a simple voltage converter; it also has power optimization capabilities and is therefore called an optimizer. Each power optimizer sets the initial current and initial voltage of its corresponding PV module at the maximum power point (MPP). For example, in the diagram, a local device J1's power optimizer sets its corresponding PV module P1 at the MPP; similarly, a local device J2's power optimizer sets its corresponding PV module P2 at the MPP; and a local device JN's power optimizer sets its corresponding PV module PN at the MPP. The power optimizer optimizes the power of the PV modules. In this example, the controller IC1 of the local device JN can be used to operate the power optimizer to perform voltage conversion actions such as boost, buck, or buck-boost, with the aim of setting the initial current and initial voltage of the PV modules—that is, the input voltage and input current of the local device—to the maximum power point of PV module PN. Therefore, the local device can also have power management functions to maximize the power generation efficiency of the PV modules.

[0098] See Figure 9 A power optimizer is a DC-to-DC voltage converter and also a single-module-level battery maximum power point tracking (MPPT) device. After optimizing the maximum power of a single module, the power optimizer transfers the total power to the inverter for DC-to-AC conversion, which then supplies power for local use or direct grid connection. The inverter can typically be a pure inverter without MPPT or an inverter equipped with two levels of MPPT. Mainstream power optimizers commonly use conventional BUCK, BOOST, BUCK-BOOST, or CUK circuit architectures.

[0099] See Figure 9 The arc sensor is integrated with a power optimizer (such as JN), which is used to set the PN of the photovoltaic module at its maximum power point. An arc sensor, not shown, is used to detect arcs at the photovoltaic module.

[0100] See Figure 9 Photovoltaic modules P1-PN are connected in series to supply power to the bus. The DC arc fault diagnosis result is collected at each photovoltaic module in P1-PN. The DC arc fault diagnosis result for photovoltaic module P1 is collected by local device J1, for photovoltaic module P2 by local device J2, and so on. Therefore, the DC arc fault diagnosis result for photovoltaic module PN is collected by local device JN.

[0101] See Figure 9 The local device J1 sends the DC arc fault judgment result of the photovoltaic module P1 collected by the arc sensor at the photovoltaic module P1 to the concentrator 150.

[0102] See Figure 9 The local device J2 sends the DC arc fault judgment result of the photovoltaic module P2 collected by the arc sensor at the photovoltaic module P2 to the concentrator 150.

[0103] See Figure 9 The local device JN sends the DC arc fault judgment result at the PN of the photovoltaic module, collected by the arc sensor at the PN of the photovoltaic module, to the concentrator 150.

[0104] See Figure 9 After the concentrator 150 learns the DC arc fault judgment result at each photovoltaic module, it can analyze whether the arc event is caused by interference signals based on the DC arc fault judgment results transmitted by each battery string ST1-STM: if the arc sensors of all battery strings report a DC arc fault, the arc event is considered to be caused by interference signals coupled to each battery string; if only the arc sensors of some battery strings report a DC arc fault, while the arc sensors of the remaining battery strings do not report a DC arc fault, the arc event is considered not to be caused by interference signals coupled to each battery string, thereby identifying the interference of interference signals (such as high-frequency harmonics) on the arc event.

[0105] See Figure 9 The concentrator 150 includes a circuit breaker S2 disposed on the cable. The circuit breaker S2 can be disposed on either the positive or negative busbar. The concentrator 150 can control the circuit breaker S2 to turn off, thereby immediately disconnecting the cable. The concentrator 150 includes a controller IC2, which analyzes and judges the DC arc fault judgment results transmitted by each battery string to determine whether the arc event is caused by interference signals. Each battery string supplies power to the busbar. If it is found that the arc event is not caused by interference signals coupled to each battery string, the concentrator controls the switch (such as the circuit breaker S2) on the busbar to switch to the off state. If the controller IC2 determines that the arc event is not caused by interference signals coupled to each battery string, but is a real arc, the controller IC2, for example, using a microprocessor, can drive the switch S2 to turn off.

[0106] See Figure 9Accidents caused by arcing and fires due to poor contact, aging, and short circuits are becoming increasingly frequent, highlighting the growing importance of DC arc fault detection in photovoltaic systems. DC arc faults are a major culprit in electrical fires. Once a DC arc fault occurs in a photovoltaic system, the lack of zero-crossing protection and the continuous energy generated by the photovoltaic modules under sunlight create a stable combustion environment for the fault arc. If timely and effective measures are not taken, temperatures exceeding several thousand degrees Celsius can occur, leading to fires. Some substances may melt or even evaporate, producing large amounts of toxic gases, endangering human life and causing significant economic losses.

[0107] See Figure 9 Based on the nature of the current, electric arcs can be broadly classified into direct current (DC) arcs and alternating current (AC) arcs. AC arcs are well-known and have been used for a longer period, with mature detection methods and commercially available products for AC fault arcs. However, photovoltaic (PV) systems are relatively new, and the inherent characteristics of DC arcs differ significantly from those of AC arcs. For example, DC current does not exhibit the zero-crossing characteristic of AC current. Therefore, AC arc detection methods cannot be applied to PV applications. This application aims to detect genuine DC arc faults in PV systems to prevent serious accidents such as fires caused by faulty arcs.

[0108] See Figure 9 It's important to note that arcing events are not necessarily high-risk DC arc faults. For example, actions such as plugging and unplugging switches or rotating motors can cause arcs in the power system. However, these arcs are transient and may only slightly affect the normal operation of the system and equipment; these are called good arcs, or normal arcs. Arcs caused by factors other than normal arcs, such as short circuits, insulation aging, or poor wiring connections, that can burn continuously and easily ignite surrounding flammable materials, are called bad arcs, or DC fault arcs. Pluging and unplugging switches or rotating motors also constitute interference signals.

[0109] See Figure 3 For example, suppose the positive output terminal of local device J1 is connected to the positive bus B1, and the negative output terminal of local device JN is connected to the negative bus B2. Also, in a series of local devices, the positive output terminal of the next local device can be connected to the negative output terminal of the adjacent preceding local device. Alternatively, in a multi-level local device series, the positive output terminal of the next level local device can be connected to the negative output terminal of the adjacent preceding local device. This allows multiple local devices to be connected in series to form a battery string. Each photovoltaic module in the battery string is equipped with a local device to receive its output power. For example, any photovoltaic module PN in the battery string is equipped with a local device JN to receive its output power. Multiple photovoltaic modules P1 to PN in any battery string, and their corresponding local devices, are connected in series via cables, for example, J1 to JN.

[0110] SeeFigure 2 Each photovoltaic module PN is equipped with a local device JN for collecting its arc information. At least one concentrator 150 is configured on the bus or cable to collect arc information from each battery string. Communication is established between the local device and the concentrator. The local DC arc fault information of each photovoltaic module JN is sent to the concentrator by its configured local device, and the concentrator 150 determines whether a real fault has occurred at the battery string ST1-STM. It determines whether the arc event is caused by interference signals coupled to each battery string or by non-interference signals.

[0111] See Figure 2 The local device JN includes a first controller IC1 and a first communication module CM1, while the concentrator 150 includes a second controller IC2 and a second communication module CM2. The first controller IC1 of the local device JN uses the corresponding first communication module CM1 to send the arc fault results of the corresponding photovoltaic module PN to the management device 100. The second controller IC2 of the concentrator receives the arc fault results of each battery string via the second communication module CM2, and determines whether a fault has occurred at each battery string. The communication modes between the local device JN and the concentrator 150 include at least power line carrier communication or wireless communication.

[0112] See Figure 3 If it is initially believed that the arcing event is caused by interference signals (harmonic bur, plugging and unplugging switches, motor rotation or load fluctuations), the premise for its validity is that the following conditions must be met: that is, the premise for further confirmation that the arcing event is indeed caused by interference signals is that all parallel battery string ST1-STMs have DC arcing faults with the same arcing characteristics. The so-called same arcing characteristics at least include that the arcing signal or the arcing frequency of the DC arcing fault at each battery string ST1-STM falls in the same frequency band.

[0113] See Figure 3 Interference signals also include interharmonic components related to sunlight generated by the inverter on the bus side: random changes in sunlight will cause random fluctuations in the DC voltage output of the photovoltaic system, or random fluctuations in the bus voltage. At this time, through the interaction between the AC and DC sides of the inverter, complex interharmonic components may be generated on both the DC and AC sides.

[0114] See Figure 10 The interference signals also include bus-side harmonic components caused by the inverter's maximum power point tracking (MPPT): During the MPPT phase, the inverter's DC voltage command needs to be continuously adjusted to achieve maximum power output on the bus side, resulting in DC-side voltage fluctuations. At this time, the inverter's MPPT operation generates interharmonic components on both the DC and AC sides.

[0115] See Figure 10 In an optional embodiment, a battery string-level arc detection method supporting interference resistance is provided, comprising multiple battery strings connected in parallel, with each battery string including multiple photovoltaic modules connected in series: DC arc faults at each battery string are monitored individually (i.e., the arc conditions of ST1 to STM are monitored separately); DC arc faults at each battery string are analyzed centrally (i.e., the arc conditions of ST1 to STM are analyzed uniformly): if DC arc faults occur in all battery strings, the arc event is considered to be caused by interference signals coupled to each battery string, i.e., it is not a real arc; if only some battery strings (e.g., ST1 / ST2) experience DC arc faults, and the remaining battery strings (e.g., STM) do not experience DC arc faults, the arc event is considered not to be caused by interference signals coupled to each battery string, but a real fault arc.

[0116] See Figure 10 In an optional embodiment, if the arcing event is considered to be caused by an interference signal, the prerequisite is that all parallel battery strings have experienced DC arcing faults with the same arcing characteristics, requiring that the same arcing characteristics include at least that the arcing signals at each battery string fall in the same frequency band.

[0117] See Figure 10 If the arc sensors of all battery strings (e.g., ST1-ST2 and STM) report DC arcing faults, a special case arises: if the arcing event is indiscriminately assumed to be caused by interference signals coupled to each battery string, errors in arcing event determination will occur. For example, while the DC arcing fault at some battery strings (e.g., ST1-ST2) may indeed originate from interference signals, the DC arcing fault at other battery strings (e.g., STM) may be a genuine arcing event originating from the photovoltaic module itself. In such a case, determining that the arcing event is caused by interference signals coupled to each battery string would be biased. Although this situation is not universal, it is prone to occur randomly, posing a challenging problem.

[0118] See Figure 10In an optional example, if the arc sensors of all battery strings report a DC arc fault, the time interval for the inverter to perform Maximum Power Optimization (MPPT) needs to be compressed at the inverter. This forces the voltage ratio of the interference signal relative to the bus voltage to bounce frequently during the inverter's MPPT phase. If, in this case, the arc sensors of some battery strings report a DC arc fault while those of the remaining battery strings do not, then the possibility that the arc event is caused by interference signals coupled to each battery string is ruled out. Instead, it is considered that the DC arc faults at some battery strings (e.g., ST1-ST2) do indeed originate from the so-called interference signal, while the DC arc faults at other battery strings (e.g., STM) are real arcs occurring locally within the photovoltaic modules (not spurious, but genuine DC arc faults). Note that the judgment result of a DC arc fault originating from an interference signal is often a spurious, non-genuine DC arc fault. Conversely, if the situation does not occur where "the arc sensors of some battery strings report a DC arc fault, while the arc sensors of the remaining battery strings do not report a DC arc fault," then it is ultimately confirmed that the arc event is caused by interference signals coupled to each battery string, rather than a real arc occurring locally within the photovoltaic module. This analysis of whether an arc event is caused by interference signals only exists during the transient state of the inverter performing maximum power optimization. This transient state, for example, occurs at the moment when the inverter adjusts the bus voltage and bus current during maximum power optimization. In other words, the inverter performing maximum power optimization is a prerequisite for analyzing whether an arc event is caused by interference signals.

[0119] See Figure 10 In an optional example, if DC arcing faults occur in all battery strings, the time interval for the inverter to perform Maximum Power Optimization (MPPT) needs to be compressed at the inverter. This forces the voltage ratio of the interference signal relative to the bus voltage to frequently bounce during the inverter's MPPT phase. If, in this case, only some battery strings experience DC arcing faults while the remaining battery strings do not, then the possibility that the arcing event is caused by interference signals coupled to each battery string is ruled out. Instead, it is considered that the DC arcing faults at some battery strings (e.g., ST1-ST2) do indeed originate from the so-called interference signals, while the DC arcing faults at other battery strings (e.g., STM) are real arcs occurring locally within the photovoltaic modules (not spurious, real DC fault arcs). If, in this case, the possibility that only some battery strings experience DC arcing faults while the remaining battery strings do not, then it is ultimately confirmed that the arcing event is caused by interference signals coupled to each battery string, rather than real arcs occurring locally within the photovoltaic modules.

[0120] See Figure 10 In an optional example, if the arc sensors of all battery strings report a DC arc fault, the inverter will significantly change the amplitude of the bus voltage during the maximum power optimization (MPPT) process. This will cause the voltage ratio of the interference signal relative to the bus voltage to jump sharply during the maximum power optimization phase. If, in this case, "the arc sensors of some battery strings report a DC arc fault, while the arc sensors of the remaining battery strings do not report a DC arc fault," then the possibility that the arc event is caused by interference signals coupled to each battery string is ruled out. Instead, it is considered that the DC arc faults at some battery strings (e.g., ST1-ST2) do indeed originate from the so-called interference signal, while the DC arc faults at other battery strings (e.g., STM) are real arcs occurring locally in the photovoltaic modules (not spurious, real DC fault arcs). Conversely, if the situation does not occur where "the arc sensors of some battery strings report a DC arc fault, while the arc sensors of the remaining battery strings do not report a DC arc fault," then it is ultimately confirmed that the arc event is caused by interference signals coupled to each battery string, rather than a real arc occurring locally on the photovoltaic module.

[0121] See Figure 10 In an optional example, if all battery strings experience DC arcing faults, the inverter significantly adjusts the bus voltage amplitude during Maximum Power Optimization (MPPT). This causes a sharp jump in the voltage ratio of the interference signal relative to the bus voltage during the MPPT phase. If, in this case, only some battery strings experience DC arcing faults while the remaining strings do not, it rules out the possibility that the arcing event is caused by interference signals coupled to each battery string. Instead, it is assumed that some battery strings (e.g., ST1-ST2) do indeed originate from the so-called interference signal, while others (e.g., STM) are genuine arcs occurring locally within the photovoltaic modules (not spurious, real DC fault arcs). Conversely, if the scenario of "only some battery strings experiencing DC arcing faults while the remaining strings do not" does not occur, it is ultimately confirmed that the arcing event is caused by interference signals coupled to each battery string, rather than genuine arcs occurring locally within the photovoltaic modules.

[0122] See ​In optional examples, the time interval for the compressor to perform maximum power optimization (MPPT) or the magnitude of the bus voltage adjustment during MPPT execution can be considered. Based on these conditions, if further requirements dictate that "the arc sensor is also integrated with a power optimizer used to set the photovoltaic modules at their maximum power point," then during the inverter's MPPT execution phase, the power optimizer's output voltage is forced to adaptively fluctuate and flicker, further aggravating the frequency or severity of the jumps in the voltage ratio of the interference signal relative to the bus voltage during MPPT. This is highly useful for analyzing whether an arc event is caused by an interference signal.

[0123] See ​ Given the monitoring pressure related to electric arcs, it is necessary to establish a reasonable monitoring and management mechanism. This mechanism can extract module-level electric arc data from the module panels and feed the data back to the owner or user. For example, real-time parameters such as the voltage, current, electric arc, power, and ambient temperature of the photovoltaic module need to be monitored promptly, especially abnormal conditions such as electric arcs or faults. This monitoring data can provide a basis for improving and optimizing each photovoltaic module, and faulty or aging modules can be quickly located and repaired. Whether attempting to achieve active control of the battery modules by external devices or transmitting battery module parameter information from the module itself to external devices, communication issues are involved in the photovoltaic module monitoring system. Intelligent management of photovoltaic modules includes not only conventional monitoring of operating parameters but also safety management, shutdown management, and output power management.

[0124] See ​ In summary, this application proposes a battery pack cascade arc detection method that supports interference resistance to identify the interference of interference signals on arc events. Unlike traditional solutions, this application focuses on eliminating the obstruction of interference signals to arc identification, avoiding mistaking false arcs for real arcs. The core of this application is to implement a battery pack cascade arc detection method that supports interference resistance; this application achieves an implementation method for interference resistance technology in battery pack cascade arc detection. These are the main points or themes of this application.

[0125] The foregoing description and accompanying drawings have provided typical embodiments of specific structures for specific implementations. The above application content presents existing preferred embodiments, but these are not intended to be limiting. Various changes and modifications will undoubtedly be apparent to those skilled in the art after reading the foregoing description. Therefore, the appended claims should be considered as covering all changes and modifications that encompass the true intent and scope of the invention. Any and all equivalent scopes and contents within the scope of the claims should be considered to still fall within the intent and scope of the invention.

Claims

1. A method for implementing an anti-interference technique for detecting an arc event in a battery string, wherein a plurality of battery strings are connected in parallel, and each battery string comprises a plurality of photovoltaic modules connected in series, the method comprising: arranging an arc sensor for detecting a DC arc fault at one or more photovoltaic modules of each battery string; transmitting a result of a DC arc fault judgment of each battery string to a concentrator; and analyzing, by the concentrator, whether the arc event is caused by an interference signal based on the results of the DC arc fault judgment transmitted by the battery strings, wherein: if all the arc sensors of the battery strings reflect that a DC arc fault occurs, the arc event is considered to be caused by the interference signal coupled to each battery string; and if only a part of the arc sensors of the battery strings reflect that a DC arc fault occurs, the arc event is considered not to be caused by the interference signal coupled to each battery string, thereby identifying the interference of the interference signal on the arc event.

2. The method of claim 1, wherein: one of the sources of the interference signal comprises high-frequency harmonics generated by an inverter during an operation phase.

3. The method of claim 1, wherein: the arc sensor of the battery string transmits the result of the DC arc fault judgment provided by the battery string locally to the concentrator through power line carrier or wireless communication.

4. The method of claim 1, wherein: the arc sensor is integrated with a photovoltaic junction box for connecting a single photovoltaic module to the battery string.

5. The method of claim 1, wherein: the arc sensor is integrated with a shutoff device for removing a single photovoltaic module from the battery string or restoring the removed photovoltaic module to the battery string.

6. The method of claim 1, wherein: the arc sensor is integrated with a power optimizer for setting the photovoltaic module at a maximum power point.

7. The method of claim 1, wherein: the arc sensor is integrated with a voltage converter for performing a step-up voltage conversion or a step-down voltage conversion on an initial voltage of the photovoltaic module.

8. The method of claim 1, wherein: each battery string supplies power to a bus, and if the arc event is not caused by the interference signal coupled to each battery string, a switch provided on the bus is controlled by the concentrator to switch to an off state.

9. A method for implementing an anti-interference technique for detecting an arc event in a battery string, wherein a plurality of battery strings are connected in parallel, and each battery string comprises a plurality of photovoltaic modules connected in series, the method comprising: individually monitoring a DC arc fault at each battery string; and centrally analyzing the DC arc fault at each battery string. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ If a DC arc fault has occurred in all of the battery strings, the arc event is considered to be caused by an interference signal coupled at each of the battery strings; If a DC arc fault has occurred in only some of the battery strings, and a DC arc fault has not occurred in the remaining other battery strings, the arc event is not considered to be caused by an interference signal coupled at each of the battery strings.

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