CN115514316A

CN115514316A - Anti-interference technology implementation method for photovoltaic module level arc detection

Info

Publication number: CN115514316A
Application number: CN202211229924.XA
Authority: CN
Inventors: 刘溟江; 周国栋; 孔超; 张旭光; 许杰; 周恒乐; 张永
Original assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI; Huaneng Xuzhou Tongshan Wind Power Generation Co ltd; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Current assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI; Huaneng Xuzhou Tongshan Wind Power Generation Co ltd; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Priority date: 2022-10-08
Filing date: 2022-10-08
Publication date: 2022-12-23

Abstract

The invention mainly relates to an anti-interference technology implementation method for photovoltaic module level arc detection. An arc sensor that detects a direct current arc fault is disposed at one or more photovoltaic modules of the battery string. And (3) transmitting the direct current arc fault judgment results corresponding to each battery pack string to the concentrator, and analyzing whether the direct current arc fault judgment results transmitted by the battery pack strings are arc events caused by interference signals by the concentrator: if the arc sensors of all the battery pack strings reflect that the direct current arc fault occurs, the arc event is considered to be caused by interference signals coupled to the battery pack strings; if only the arc sensors of one part of the battery strings reflect that the direct current arc fault occurs, and the arc sensors of the other part of the battery strings do not reflect that the direct current arc fault occurs, the arc events are not considered to be caused by interference signals coupled to the battery strings, and therefore the interference situation of the interference signals on the arc events is discriminated.

Description

Anti-interference technology implementation method for photovoltaic module level arc detection

Technical Field

The invention mainly relates to the field of photovoltaic power generation, in particular to a photovoltaic module-level arc detection anti-interference technology implementation method in a photovoltaic power generation system with a photovoltaic module.

Background

With the shortage of traditional energy sources and the development of electric power technology, photovoltaic power is paid more and more attention, and a photovoltaic power generation system needs to meet safety regulations in electric power application. Arcing is a gas discharge phenomenon, and sparks generated by current flowing through an insulating medium such as air are a manifestation of the gas discharge. Detecting arcs and actively taking countermeasures are key elements in maintaining photovoltaic power generation systems under safe regulations. Although the industry has endeavored to find out the regularity and commonality of the arcing phenomenon in order to find an accurate detection means for the arcing, it is difficult to avoid the current problem that it is difficult to provide a reasonable and strict detection mechanism for the arcing and to design a corresponding accurate detection apparatus in the industry.

Detection of a fault arc is essential. Fault arcs are often caused by non-operational causes such as aged breakdown of line insulation or loose terminals present in electrical lines. The fault arc location absorbs most of the energy generated by the photovoltaic system and converts it into high temperature ionized gas, which obviously burns cables and electrical equipment. A large amount of heat released in a short time during fault arc discharge can ignite other flammable and explosive materials around the photovoltaic system, so that disasters and unexpected power failure accidents in local areas are caused, and property safety and personnel safety threats exist.

The electric arc is divided into a direct current arc and an alternating current arc according to the current property. The well-known alternating current application time is earlier, and alternating current fault arcs exist mature detection methods and commercial products, however, the starting time of a photovoltaic system is later, and the nature characteristics of a direct current arc are different from that of the alternating current, and a typical direct current has no zero-crossing point characteristics like the alternating current, so that the detection means of the alternating current arc cannot be applied to photovoltaic occasions. The variables influencing the electrical properties of the direct current arc are various originally, and the arc is more complicated due to different photovoltaic use environments. It is generally recognized in the industry that it is difficult to establish a mathematical model of a dc arc, and although some arc models are mentioned, these simplified models are usually studied based on some single characteristics or several very limited characteristics of an arc, and in fact, noise inevitably existing in a photovoltaic environment and accidental interference of a power system are very likely to mislead arc detection, which causes erroneous detection results, and dynamically changing illumination intensity and ambient temperature, and a great amount of switching noise are interference sources for misjudgment and missing judgment.

In summary, since the frequency spectrum characteristics of the arc vary widely, it is a difficult task to determine whether there is a real fault arc by simply using the frequency spectrum characteristics: the main reason is that the standard for comparing the fault arc parameter characteristics of the target is not unified at present, and the meaning of establishing the standard arc parameter characteristics is not great; moreover, the actually detected current parameter information is bound to have more or less natural errors, which are the reasons for the failure to detect the arc or the false alarm of the arc.

Disclosure of Invention

The application discloses anti-interference technology implementation method of photovoltaic module level arc detection, by a plurality of battery group cluster parallel connection and every battery group cluster all including a plurality of photovoltaic module of series connection, its characterized in that:

arranging arc sensors at one or more photovoltaic modules of each battery string to detect a direct current arc fault;

and the direct current arc fault judgment results corresponding to each battery pack string are all transmitted to a concentrator, and then the concentrator analyzes whether the arc events are caused by interference signals according to the direct current arc fault judgment results transmitted by the battery pack strings:

if the arc sensors of all the battery pack strings reflect that the direct current arc fault occurs, the arc event is considered to be caused by interference signals coupled to the battery pack strings;

if only the arc sensors of one part of the battery strings reflect that the direct current arc fault occurs, and the arc sensors of the other part of the battery strings do not reflect that the direct current arc fault occurs, the arc events are not considered to be caused by interference signals coupled to the battery strings, and therefore the interference situation of the interference signals on the arc events is discriminated.

The above method is characterized in that: an inverter is supplied by each series of parallel-connected battery cells, one of the sources of the interference signal comprising at least the high-frequency harmonics generated by the inverter during the operating phase.

The method is characterized in that: and the arc sensor configured in the battery pack string sends a direct current arc fault judgment result locally provided by the battery pack string to the concentrator in a power line carrier or wireless communication mode.

The above method is characterized in that: the arc sensor is also integrated with a photovoltaic junction box for connecting individual photovoltaic modules to the battery string.

The method is characterized in that: the arc sensor is also integrated with a shut-off device for removing individual photovoltaic modules from the string or for reconnecting the removed photovoltaic modules into the string.

The method is characterized in that: the arc sensor is also integrated with a power optimizer for setting the photovoltaic module at its maximum power point.

The above method is characterized in that: the arc sensor is also integrated with a voltage converter for performing step-up or step-down voltage conversion of the initial voltage of the photovoltaic module.

The method is characterized in that: the bus is supplied by each battery string, and a switch arranged on the bus is switched to an off state by the concentrator control if an arc event is found not to be caused by interference signals coupled to each battery string.

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

monitoring a dc arc fault at each battery string individually; and

the dc arc faults at each battery string were analyzed centrally:

if a DC arc fault occurs in all of the battery strings, the arc event is considered to be caused by interference signals coupled to the respective battery strings;

if only a portion of the battery strings have a dc arc fault while the remaining other portion of the battery strings have no dc arc fault, then the arcing event is deemed not to have been caused by the interference signal coupled to the respective battery strings.

The method is characterized in that: if the arc event is considered to be caused by the interference signal, the premise is that all the parallel battery strings have direct current arc faults with the same arc characteristics, and the same arc characteristics at least comprise that the arc signals at all the battery strings fall in the same frequency band.

The application also relates to a photovoltaic module-level arc detection method supporting anti-interference, which comprises an implementation method of the anti-interference technology of photovoltaic module-level arc detection, and comprises the following steps: the method aims to discriminate electric arcs and eliminate interference (such as noise inevitably existing in a power generation link and accidental interference on an alternating current side of a direct current side), and further, for example, dynamic change of solar irradiance, temperature difference variable, switching noise and harmonic waves existing in an inversion system in large quantity are all interference sources for misjudgment and missed judgment.

Drawings

In order that the above objects, features and advantages will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to the appended drawings, which are illustrated in the appended drawings.

Fig. 1 shows a photovoltaic module supplying power to a bus in series and an energy collecting device is arranged on the bus.

Fig. 2 is an exemplary schematic diagram of an arc event caused by interference signals coupled to battery strings.

Fig. 3 is a diagram for transmitting the dc arc fault determination result corresponding to each battery string to a concentrator.

Figure 4 is a photovoltaic module configured with a voltage converter to raise or lower the voltage of the photovoltaic module.

FIG. 5 is an exemplary illustration of a source of a DC arc fault from a jamming signal or series or parallel arc.

Fig. 6 is a view of the photovoltaic module connected to a bus bar by a photovoltaic junction box equipped with a data acquisition module.

Fig. 7 shows the connection of the photovoltaic module to the bus bar by means of a shut-off device equipped with a data acquisition module.

Fig. 8 shows the connection of a photovoltaic module to a bus bar by means of a voltage converter equipped with a data acquisition module.

Fig. 9 shows that information such as voltage, current and arc of the photovoltaic module is sent to the management device by the local device.

FIG. 10 is an exemplary plot of the source of a DC arc fault from a jamming signal and concurrent series-parallel arcs.

Detailed Description

The present invention will be described more fully hereinafter with reference to the accompanying examples, which are intended to illustrate and not to limit the invention, but to cover all those embodiments, which may be learned by those skilled in the art without undue experimentation.

Referring to fig. 1, in an alternative example, in the case of battery strings ST1-STM, M is a positive integer exceeding 1 and a number of tens or more strings are often used in parallel connection under a single inverter of a photovoltaic power plant. The limited number of strings in the figures is merely an illustrative example and does not constitute a specific limitation.

Referring to fig. 1, power is supplied to bus bars B1-B2 by respective parallel battery strings ST 1-STM. An energy management device 100 such as an inverter, a combiner box, or a charger receives electric energy supplied from each battery string from a bus.

With reference to fig. 1, in terms of the management of the components of the photovoltaic module: a plurality of photovoltaic modules P1-PN supply the bus in series and assuming that the bus comprises a positive bus B1 and a negative bus B2, the positive pole of one string of the series of photovoltaic modules P1-PN is coupled to the so-called positive bus B1, and correspondingly the negative pole of the aforesaid string of the series of photovoltaic modules P1-PN is coupled to the so-called negative bus B2. For example, each pv module is equipped with a pv junction box, which in a pv system mainly serves to connect the electrical energy generated by the pv module to external wiring and allows the pv junction box to have bypass diodes in some cases, so that when an abnormality occurs in the pv module, such as a hot spot effect, the abnormal pv module can be bypassed by the bypass diodes of the pv junction box.

Referring to fig. 1, in the field of photovoltaic power generation, a photovoltaic module, that is, a photovoltaic cell, is a core component of power generation, and a solar panel is divided into a monocrystalline silicon cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, and the like in a mainstream technical direction. The number of photovoltaic modules adopted by a large centralized photovoltaic power station is huge, while the number of photovoltaic modules adopted by a small household small power station in a small scale is relatively small. Silicon substrate photovoltaic modules require service lives in the field of up to more than twenty years, so real-time and permanent monitoring of photovoltaic modules is essential. Many internal and external factors cause the photovoltaic module to have low power generation efficiency, and factors such as manufacturing or installation differences between the photovoltaic modules themselves or shading or maximum power tracking adaptability cause the conversion efficiency of the module to be reduced.

Referring to fig. 1, taking a common shadow blocking as an example, if a part of the photovoltaic modules is blocked by clouds or buildings or tree shadows or pollutants and the like, the part of the photovoltaic modules becomes a load by a power supply and does not generate electric energy any more, the local temperature of the photovoltaic modules at a position with a serious hot spot effect is usually higher, even exceeds 150 ℃, so that a local area of the photovoltaic modules is burnt or forms a dark spot, a welding spot is melted, a packaging body is aged, glass is exploded and corroded, and permanent damage such as dark spot, welding spot melting, packaging body aging, glass explosion and corrosion causes great hidden danger to the long-term safety and reliability of the photovoltaic modules, so that it is more important to avoid mismatch between the photovoltaic modules and find and locate faults in time.

Referring to fig. 1, let a photovoltaic module P1 be equipped with a local device J1. In the present embodiment, it is assumed that the local device is a photovoltaic junction box, the positive electrode of the photovoltaic module P1 is connected to the positive bus bar B1 by the local device J1, and the negative electrode of the photovoltaic module P1 is connected to the positive electrode of the photovoltaic module P2 by the local device J1 according to the connection function of the photovoltaic junction box. And similarly, if the local equipment is a photovoltaic junction box, the anode of the photovoltaic component P2 is connected to the cathode of the P1 by the local equipment J2, and according to the connection function of the photovoltaic junction box, the cathode of the photovoltaic component P2 is connected to the anode of the P3 by the local equipment J2. And similarly, if the local device is a photovoltaic junction box, the positive pole of the photovoltaic component P3 is connected to the negative pole of the P2 by the local device J3, and according to the connection function of the photovoltaic junction box, the negative pole of the photovoltaic component P3 is connected to the positive pole of the P4 by the local device J3. By analogy, photovoltaic modules are connected in series to form a string that provides a higher voltage level. A photovoltaic junction box (PV junction box) which is a connector between the photovoltaic module and the bus bar is also called a solar junction box.

Referring to fig. 2, the management device 100 is exemplified by an inverter INVT that can invert the dc power on the bus to the desired ac power, noting that there are many other alternatives to the management device, such as a combiner box or a battery charger that charges a battery. The energy management device is explained by taking an inverter INVT as an example.

Referring to fig. 2, knowledge about inverter INVT: the photovoltaic inverter has the main function of converting direct current emitted by a photovoltaic module into alternating current in a photovoltaic system, and in addition, the inverter also has important functions of detecting the operation state of the module, a power grid and a cable, communicating with the outside, managing a system safety manager and the like.

Referring to fig. 2, in the photovoltaic industry standard NB32004-2013, there are over 100 strict technical parameters for inverters and each parameter is qualified for sale. The method is used for detecting a plurality of items such as protection connection, contact current, power frequency withstand voltage of solid insulation, rated input and output, conversion efficiency, harmonic wave and waveform distortion, power factor, direct current component and alternating current output side overvoltage/undervoltage protection of a photovoltaic grid-connected inverter product.

Referring to fig. 2, the electricity is sine wave alternating current, the direction and the magnitude of the alternating current are changed periodically, for example, the frequency of the alternating current is fifty hertz, the waveform changed according to the frequency is called fundamental wave, more than 97% of the power grid is the fundamental wave, and one part of the power grid is harmonic wave (harmonic wave), which means that the frequency contained in the current is the electric quantity of integral multiple of the fundamental wave, the harmonic wave with the frequency twice the fundamental frequency is called second harmonic wave, the harmonic wave with the frequency three times the fundamental frequency is called third harmonic wave, and the harmonic wave with the frequency n times the fundamental frequency is called n-th harmonic wave. It is further provided that those harmonics with frequencies that are odd multiples of the fundamental frequency, collectively referred to as odd harmonics, and those harmonics with frequencies that are even multiples of the fundamental frequency, collectively referred to as even harmonics.

Referring to fig. 2, the high frequency harmonics bur of the inverter INVT are delivered to the photovoltaic modules in a straight line via a dc bus or a branch line coupled to each photovoltaic module. The broken line in the figure is the transmission path of the harmonic bur. The transfer path of the harmonic bur is illustrated as a string ST1-STM, and is transferred to the photovoltaic modules P1-PN of each string.

Referring to fig. 2, the harmonics (the harmonics bur delivered to the photovoltaic modules P1-PN) are not only useless but also cause serious damage. Most devices are applied to inductive devices, for example, and can only absorb fundamental waves, and higher harmonics can be converted into heat or vibration, so that electric devices are overheated, vibration and noise are generated, insulation is aged, the service life is shortened, and even the devices are burnt out due to faults. During power transfer, harmonics, due to their high frequency, create large impedances that consume power and cause a reduction in the efficiency of power production, transmission and utilization. The harmonic bur is easily confused with the arc.

Referring to fig. 2, harmonic waves (transmitted to the harmonic bur at the P1-PN of the photovoltaic module) may cause local parallel resonance or series resonance of the power system, so that the harmonic content is amplified, and thus devices such as a built-in capacitor are burned out, or devices in certain frequency bands cannot normally work, and the harmonic waves may cause relay protection and automatic cut-off malfunction, so that electric energy metering is disordered. Outside of the power system, harmonics can cause severe interference to communication equipment and electronic equipment.

Referring to fig. 2, the photovoltaic modules P1-PN emit direct current, and after the direct current is changed by the inverter bridge, the magnitude and direction of the voltage and current are changed, but the voltage and current are not pure sine wave alternating current, and the current and voltage are not continuous, and contain a large amount of harmonics and can be changed into pure sine wave alternating current after being processed, which is filtering. The output harmonic of the photovoltaic inverter is divided into two parts, one part is higher harmonic and mainly comes from a modulation mode, and the other part is low harmonic and comes from switch dead zone effect, device parameter drift, sampling error, control parameter mismatching and the like.

Referring to fig. 2, an arc sensor or a fault arc detector (arc fault sensor) for detecting a dc arc fault is disposed at one or more photovoltaic modules P1-PN of each battery string, which belongs to the known art, and any fault arc sensor related to the current technology can be directly used in the present application.

Referring to fig. 2, the inverter INVT suppresses harmonics mainly from both hardware and software aspects. The main purpose is to prevent the harmonic bur from being mistaken for a fault arc (arc fault) at the photovoltaic module P1-PN.

Referring to fig. 2, the hardware of the inverter INVT is mainly a filter circuit, and the common filter mode of the inverter includes a combination mode of using an inductor, using an inductor capacitor, or using an inductor capacitor inductor (L, LC, LCL). The inductance is the main characteristic that the current cannot change suddenly, and the discontinuous current of the inverter bridge can be converted into the continuous current by utilizing the characteristic. The capacitance characteristic is that the voltage cannot change suddenly, and the discontinuous voltage of the inverter bridge can be converted into continuous voltage by utilizing the characteristic. The purpose of the hardware circuitry is to prevent the harmonic bur from being mistaken for a faulty arc at the photovoltaic module P1-PN.

Referring to fig. 2, the following aspects are mainly found in the software of the inverter INVT: the switching frequency is improved, the parallel operation harmonic cancellation capability is improved, and the software control technology for eliminating the harmonic is adopted. The purpose of the software control aspect is also to prevent the harmonic bur from being mistaken for a faulty arc at the photovoltaic module P1-PN.

Referring to fig. 2, one of the inverter INVT software, increasing the switching frequency: the higher the switching frequency of the inverter is, the wider the control bandwidth is, the more sufficient the suppression of the current harmonics in a wide range is, and in order 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, and when the pulse width modulation wave modulated and output by the inverter is distorted, the output harmonic waves and the control effect of the inverter are influenced. Increasing the switching frequency and the number of output pwm levels helps to reduce the distortion rate of the pwm waveform.

Referring to fig. 2, the second inverter INVT software, parallel harmonic cancellation capability: the distances between a plurality of group string type inverters in a square matrix and the step-up transformer are different, and the line impedance is different. Line impedance can equivalently change inductance in the grid-connected LCL filter, and different filter parameters can change the phase of harmonic waves. When a plurality of group string type inverters work in parallel, harmonic components are partially eliminated due to phase difference, and the integral harmonic value of the system is reduced.

Referring to fig. 2, the third inverter INVT software, a software control technique for eliminating harmonics: since the inverter uses a high speed digital processor, a very complex algorithm such as a repetitive control current controller algorithm can be used, and the principle is that any periodic signal can be decomposed into the sum of direct current, fundamental wave and each harmonic, and 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 dead-beat and suppressed from disturbance.

Referring to fig. 3, the main reasons for the poor detection capability of the conventional arc detection means are: one or more sets of fault arc parameter characteristics need to be worked out in advance, then the actually detected current parameter information is compared with the fault arc parameter characteristics, if the actually detected current parameter information accords with the fault arc parameter characteristics, a real arc event is considered to occur, otherwise, if the actually detected current parameter information does not accord with the fault arc parameter characteristics, the real arc event is considered not to occur. The biggest defect is that the power system of each scene to be detected is different, and the inverter model of each scene to be detected is also different, so that the traditional fault arc detection means always has detection errors or even errors, and the inherent defects are almost irresistible.

Referring to fig. 3, the inverter INVT primarily suppresses harmonics from the information collection and information processing aspects. The aim is still to prevent the harmonic bur from being mistaken for a faulty arc (arc fault) at the photovoltaic module P1-PN. This embodiment will replace the aforementioned inverter INVT to suppress harmonics mainly from both hardware and software aspects. The starting points are as follows: the inverter can only suppress, but cannot completely filter, all high-frequency harmonics in terms of hardware and software, and as long as the harmonics exist, an arc sensor built in the local device J1 can mistakenly consider that the harmonics bur are arcs (both the harmonics with odd-numbered times of the fundamental frequency and the harmonics with even-numbered times of the fundamental frequency are sources of false triggering).

Referring to fig. 3, the energy management device 100 is omitted but one concentrator 150 is shown. Note that the energy management device is not eliminated from the power generation system, but is intentionally omitted based on the simplicity of the drawing. The purpose of the arc detection method at the photovoltaic module level in this example is to support interference rejection, preventing harmonic bur from being trapped as an arc.

Referring to fig. 3, an arc detection method supporting interference resistance, in which 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: arranging arc sensors (integrated within the local equipment J1) at one or more photovoltaic modules of each battery string that detect a direct current arc fault; the dc arc fault determination results corresponding to each battery string are all transmitted to the concentrator 150, and the concentrator 150 analyzes whether the dc arc fault determination results transmitted by the battery strings are arc events caused by interference signals (such as harmonic bur) and mainly includes two aspects: if the respective arc sensors of all battery strings ST1-STM reflect the occurrence of a DC arc fault, then an arc event (arc events) is deemed to be caused by an interference signal coupled to the respective battery string ST 1-STM; if only the arc sensors of one of the battery strings (e.g., ST1-ST 2) reflect that a local dc arc fault has occurred, and the arc sensors of the other battery string (e.g., STM, etc.) do not reflect that a local dc arc fault has occurred, then the arc events (arc events) are not considered to be caused by interference signals coupled to the respective battery strings ST1-STM, thereby discriminating the interference of the interference signals with the arc events.

Referring to fig. 3, each local device J1-JN of the battery string ST1 sends a dc arc fault determination result generated by each photovoltaic module P1-PN to the concentrator 150.

Referring to fig. 3, each local device J1-JN of the battery string ST2 sends the dc arc fault determination result generated by each photovoltaic module P1-PN to the concentrator 150.

Referring to fig. 3, each local device J1-JN of the battery string STM sends a dc arc fault determination result generated by each photovoltaic module P1-PN to the concentrator 150.

Referring to fig. 3, the photovoltaic module PN is equipped with a local device JN. In this embodiment, if the local device is a photovoltaic junction box, the positive electrode of the photovoltaic module PN is connected to the negative electrode of PN-1 by the local device JN, and the negative electrode of the photovoltaic module PN is connected to the negative bus B2 by the local device JN according to the connection function of the photovoltaic junction box. Therefore, different photovoltaic modules are connected in series, and different local devices are also connected in series, wherein N is a positive integer greater than 1.

Referring to fig. 3, in an alternative embodiment, in which a plurality of battery strings are connected in parallel and each battery string includes a plurality of photovoltaic modules P1 to PN connected in series, each photovoltaic module is configured with a local device that receives its output power, e.g., photovoltaic module P1 is configured with a local device J1 that receives the P1 output power, and further, for example, other photovoltaic modules PN are configured with a local device JN that receives PN output power. A plurality of photovoltaic modules, for example, a plurality of local devices J1 to JN corresponding to P1 to PN under any battery string are connected in series with each other through cables, where the cables are usually conductive cables or called power lines or power supply lines. In the present embodiment, it is set that the positive output terminal of the local device J1 is connected to the positive bus B1 and the negative output terminal of the local device JN is connected to the negative bus B2. After the output power of each photovoltaic module is subjected to power conversion or no power change by the local device corresponding to each photovoltaic module, the output powers of the plurality of photovoltaic modules are converged together and then sent to the energy collecting device mentioned below by the local device connected in series.

Referring to fig. 3, the divided voltage of the first-stage photovoltaic device P1 is V1. The divided voltage output by the similar second-stage photovoltaic module P2 is denoted as V2. And in analogy, the divided voltage output by the Nth-stage photovoltaic module PN is VN. The total bus voltage provided by any group of photovoltaic modules is about V through calculation _BUS Equal to V1+ V2+ V3+ \ 8230VN. The output power of each photovoltaic component is superposed on the bus bar, and the power collected by the bus bar is much higher than that of the single photovoltaic component.

Referring to fig. 3, the local equipment J1 uses a photovoltaic junction box in the present embodiment. Therefore, the partial voltage V1 output by the photovoltaic module P1 to the cable can be represented by the output voltage of the local device J1, and the branch current output by the photovoltaic module P1 to the cable is represented by the current I1 output by the local device J1. The local device JN can also be characterized by the output voltage of the local device JN, for example, the divided voltage VN output by the photovoltaic module PN to the cable can be characterized by the current IN output by the local device JN, which is characteristic of the junction box. Cables are sometimes referred to as busbars.

Referring to fig. 3, IN an alternative embodiment, a plurality of local devices, e.g., J1 to JN, corresponding to a plurality of photovoltaic modules, e.g., P1 to PN, of the battery string are set IN series, the output current of the local device J1 configured by the monitored photovoltaic module P1 represents the branch current I1 supplied by the photovoltaic module P1 to the cable, the output current of the local device J2 configured by the photovoltaic module P2 represents the branch current I2 supplied by the photovoltaic module P2 to the cable, the output current of the local device JN configured by the photovoltaic module PN represents the branch current IN supplied by the photovoltaic module PN to the cable, and so on.

Referring to fig. 4, if the local device is a voltage converter, for example, each of the multi-stage pv devices P1-PN is configured with a voltage converter, and at the same time, the output power of the voltage converters corresponding to the multi-stage pv devices P1-PN is required to be superimposed on the dc bus and thereby used as the bus power. In this case, the plurality of voltage converters are connected in series with each other. The local device J1, such as a voltage converter, converts the electric energy captured from the corresponding photovoltaic module P1 into its own output power, and the local device J1, such as a voltage converter, further performs processing such as voltage boosting, voltage reducing, or voltage boosting on the initial voltage of the corresponding photovoltaic module P1, and then outputs the initial voltage. The DC/DC converter serving as the voltage converter may be a step-up type voltage converter or a step-up type switching power supply, a step-down type voltage converter or a step-down type switching power supply, a step-up/step-down type voltage converter, or a step-up/step-down type switching power supply. The local device has a voltage regulation function of boosting or reducing voltage. According to the same principle, the remaining other local devices JN such as the voltage converter convert the electric energy extracted from the corresponding photovoltaic module PN into their own output power, and the local devices JN such as the voltage converter further perform the processing of boosting, stepping down, or stepping up and stepping down the initial voltage of the corresponding photovoltaic module PN and then output the initial voltage.

Referring to fig. 4, the local device is a voltage converter that performs voltage conversion on the initial voltage of the component. In the series connection, the partial voltage provided by the first-stage photovoltaic module P1 to the cable is characterized by the output voltage V1 of the local device J1, and the branch current provided by the first-stage photovoltaic module to the cable is characterized by the current I1 output by the local device J1. The output voltage V1 is a voltage output by the converter, i.e., the local device J1, after performing conversion such as voltage boosting or voltage dropping. The local device J1 is in the present example a voltage converter for performing a voltage conversion on the initial voltage of the photovoltaic module P1. In this example, the output voltage V1 may be higher than the initial voltage output by the corresponding photovoltaic module P1 or lower than the initial voltage output by the photovoltaic module P1. A capacitor is often connected between a group of output ends of the voltage converter, that is, the positive output end and the negative output end of the local device J1, so as to ensure that the output voltage of the voltage converter is relatively smooth and reduce ripples. The positive and negative outputs of the local device herein or below may be replaced by the terms first and second output, respectively.

Referring to fig. 4, the local device is a voltage converter that performs up-down conversion on the initial voltage of the component. The partial voltage supplied to the cable by the last photovoltaic module PN IN the series connection is characterized by the output voltage VN of the local device JN and the branch current supplied to the cable by the last photovoltaic module is characterized by the local device JN output current IN. The output voltage VN is a voltage output by the converter, that is, the local device JN, after performing conversion such as voltage boosting or voltage dropping. The local device JN is in this example a voltage converter for performing voltage conversion on the initial voltage of the photovoltaic module PN. The output voltage VN in this example may be either higher than the initial voltage output by the corresponding photovoltaic module PN or lower than the initial voltage output by the photovoltaic module PN.

Referring to fig. 4, assume that the output voltage of the local device J1 is V1. Similarly, assume that the output voltage output by the local device J2 is denoted as V2. And so on, the voltage output by the nth stage local device JN is VN. The total bus voltage provided by any group of photovoltaic modules is about V through calculation _BUS Equal to V1+ V2+ V3+ \ 8230VN. The output power of each photovoltaic module is superposed on the bus bar, and the power collected by the bus bar is much higher than that of the single photovoltaic module.

Referring to fig. 4, the harmonic bur is mixed into each of the output voltages V1 to VN. Therefore, even if the output voltage of the voltage converter is detected to recognize the arc, an erroneous detection result cannot be obtained.

Referring to fig. 5, the energy collecting device used by the management apparatus 100 allows other energy collecting devices, such as a junction box CB or the like that typically collects energy of photovoltaic modules, in addition to the inverter INVT, and also allows various chargers or boost converters or the like that charge storage batteries. The management equipment can raise the voltage level of the bus by using the boost converter, and then carries out inversion conversion on the bus voltage with higher voltage level.

Referring to fig. 5, a plurality of battery strings are connected in parallel and each battery string includes a plurality of photovoltaic modules connected in series by cables, for example, a first battery string illustrated in the upper half of the drawing includes a plurality of photovoltaic modules P1 to PN connected in series by cables, and a second battery string illustrated in the lower half of the drawing includes a plurality of photovoltaic modules P1 to PN connected in series by cables. In practice more parallel battery strings are not shown.

Referring to FIG. 5, the harmonic bur will be mixed into each of the individual photovoltaic modules P1-PN. At the same time, parallel arcs may also occur between different battery strings, for example between battery strings ST1 and ST2, and cause a complexity of arc identification, since the parallel arc 80 and the harmonic bur may exist in the same frequency band. Meanwhile, series arcs may occur at each of the local devices J1 to JN, and the existence of the series arcs, the parallel arcs, and high-frequency harmonics or various interference signals causes arc judgment to be extremely troublesome.

Referring to fig. 6, the data acquisition module is used to acquire one or more items of target data of the photovoltaic module. The target data collected by the data collection module comprise initial voltage and initial current of the photovoltaic module, and output voltage or output current output to the bus by local equipment. The data acquisition module may use a voltage detection module such as a voltage detector VT or a voltage sensor that is commonly used in the industry to detect the initial voltage of the photovoltaic module, and a voltage detection module such as a voltage detector VT or a voltage sensor that is commonly used to detect the output voltage of the local device. The initial current of the photovoltaic module can be detected by using a current detection module such as a current detector CT or a current sensor, and the output current of the local device can be detected by using a current detection module such as a current detector CT or a current sensor. The initial voltage and initial current of the photovoltaic module are delivered to the local device and the output voltage and output current of the local device are delivered to the cable. The data acquisition module may also include a temperature sensor for monitoring the ambient temperature in which the photovoltaic module is located, or an irradiance meter for monitoring the effective irradiance of solar illumination of the ambient environment in which the photovoltaic module is located. The target data may also be referred to as operating parameters, and the data types include, but are not limited to, voltage, current, temperature, output power, effective light radiation, etc. of the photovoltaic module. The branch current provided by each monitored photovoltaic module to the cable is in fact: the output current of the local device configured by the monitored photovoltaic module is representative of the branch current provided by the monitored photovoltaic module to the cable.

Referring to fig. 6, the arc signal belongs to a class of data, so when the data acquisition module is used to acquire one or more target data of the photovoltaic module, the target data includes arc data. In an alternative embodiment, the data acquisition module comprises an arc sensor or a fault arc detector (arc fault sensor). The arc sensor may be integrated with a photovoltaic junction box (e.g. JN) and the photovoltaic junction box (e.g. JN) may then be used to access the photovoltaic module PN to the battery string STM. An arc sensor, not shown, is used to detect an arc condition at the photovoltaic module PN.

Referring to fig. 6, the local devices J1 to JN include the above-mentioned current detector CT or similar current detection module such as a current sensor 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, for example P1, to the cable is measured in any battery string, and since the photovoltaic module P1 is not directly connected to the cable but 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 initial voltage of the photovoltaic module P1 are delivered to the local device J1 and the latter receives the P1 output power. If the branch current IN supplied to the cable by each monitored photovoltaic module, for example PN, is measured IN this battery string, since the photovoltaic module PN is not directly connected to the cable but indirectly connected to the cable through the local device JN, the branch current supplied to the cable by the photovoltaic module PN is represented by the output current IN of the local device JN. The initial current and initial voltage of the photovoltaic module PN are delivered to the local device JN and the latter receives the PN output power

Referring to fig. 6, the local device JN includes a controller IC1. Many types of controllers IC1 currently have their own data acquisition modules that can collect the aforementioned target data. For example, the controller IC1 is also called a microprocessor and allows it to have a function of a temperature sensor or a voltage current detection module. The controller IC1 may be provided with an additional data acquisition module to collect the target data, provided that it does not have a data acquisition module. Usually, the controller IC1 can send out the target data by controlling the communication module CM1 after knowing the parameter information such as the target data. The communication mechanism of the communication module CM1 includes two types of wired communication and wireless communication: for example, all existing wireless communication schemes such as WIFI, ZIGBEE, 433MHZ communication, infrared or bluetooth, etc. can be adopted, and for example, a scheme of power line carrier communication is intentionally adopted. In an alternative embodiment of the present application, the communication module CM1 includes a power line carrier modulator, and the power line carrier modulator is configured to transmit the target data to the data receiving side by means of a power line carrier. A coupling element 10 is shown for coupling a power line carrier emitted by a power line carrier modulator to a bus, the coupling element 10 being, for example, a transformer with a primary secondary winding or, for example, a signal coupler with a coupling coil. The coupling transformer can be used, for example, to transmit a power line carrier to the primary winding and the secondary winding to the bus or bus branch as part of the bus, the carrier being transmitted to the bus by the coupling of the primary and secondary windings. A typical method of using a signal coupler with a magnetic loop and a coupling coil is to pass a bus or a bus branch directly through the magnetic loop of the signal coupler around which the coupling coil is wound, and a power line carrier is transmitted to the coupling coil and is sensed from the power bus, so that contactless signal transmission can be performed. In summary, all signal coupling schemes disclosed in the prior art can be adopted as the coupling element, and injection type inductive coupler technology, cable clamping type inductive coupler technology, switchable full-impedance matching cable clamping type inductive coupler and the like are all alternatives of the application. 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.

Referring to fig. 6, regarding wired communication and wireless communication, considering that the geographic environment of the photovoltaic module is a relatively harsh location such as a building roof or a desert zone or a suburban mountain, wireless communication generally incurs high overhead cost and is also inferior in reliability of durability, and after all, the general life of the photovoltaic module is as long as more than twenty years, so that the use of power line carriers for communication between the master node and the slave node and between the slave node and the slave node is a preferable option. The frequencies of the power line carrier signals that are allowed to be sent out by different local devices are also different, but wireless communication is also an option.

Referring to fig. 6, concentrator 150, which includes controller IC2 and communication module CM2, also allows for the inclusion of a mating carrier signal coupling element 20 for inducing a power line carrier signal from the bus, noting that the local device is sending and loading a power line carrier signal onto the bus or cable at the photovoltaic module, while the concentrator is sensing and capturing the power line carrier signal from the cable back to the concentrator. The communication module and the coupling element are sometimes integrated, as they comprise any of the types of rogowski air coil sensors or high frequency sensors, codecs or shunts, etc. It is worth clarifying that the local device is also the same as the concentrator described above: the wireless communication device has a data receiving function of wired or wireless communication. The same is true of the concentrator, as well as the local devices mentioned above: the wireless communication device has a data transmission function of wired or wireless communication. For example, when the concentrator actively polls different local devices and requires that the local devices receive polling signals, it is necessary to return target data collected and stored by the concentrator to the concentrator, and the concentrator is equivalent to a master node and the local devices are equivalent to slave nodes. The local device is illustrated and described in this example with the photovoltaic junction box as an optional example, although the wired and wireless communication functions provided in the local device and the concentrator are also applicable to this example.

Referring to fig. 6, the concentrator 150 may be integrated directly inside the energy management device 100. The concentrator 150 may be provided separately without being integrated with the energy management device 100.

Referring to fig. 6, the concentrator 150 has a current detection module such as the conventional current detector CT or current sensor mentioned above to detect the string current IS of the battery string. The string current is a current flowing through the battery string, and is also a current flowing through each of the photovoltaic modules P1 to PN or a current flowing through each of the local devices J1 to JN.

Referring to fig. 6, after the concentrator 150 and the local devices J1 to JN establish a communication mechanism, the branch current provided by each photovoltaic module to the cable is sent to the concentrator 150 by the local device configured with the branch current, and one of the core tasks of the concentrator 150 determines whether a fault, such as an arc fault, occurs at each photovoltaic module.

Referring to fig. 6, this example is a photovoltaic junction box. The photovoltaic junction box may be replaced with a shutdown device that disconnects the photovoltaic module from the cable or reconnects the disconnected photovoltaic module to the cable, the photovoltaic junction box may be replaced with a power optimizer that sets the photovoltaic module at a maximum power point, or the photovoltaic junction box may be replaced with a voltage converter that performs voltage conversion on an initial voltage of the photovoltaic module. The solution of fig. 6 is applicable to the examples of fig. 7 to 8.

Referring to fig. 7, in a shutdown apparatus supporting rapid shutdown management of a photovoltaic module, a local device JN, such as a shutdown apparatus, which can control whether the photovoltaic module is shutdown or not, is taken as an example. The shutdown management goal that the local device JN, such as the circuit of the shutdown apparatus, is expected to achieve is to determine whether it is necessary to shutdown the photovoltaic module in time: photovoltaic systems installed or built into buildings must include a quick shut-off function, reducing the risk of electrical shock to emergency personnel. Although the component shutdown device is described by taking as an example a component shutdown device that implements a shutdown function, in fact, the component shutdown device functionally integrates at least a data acquisition function and a component shutdown function. Explanation on the component shutdown function: the local device JN, such as a shutdown device, may disconnect the corresponding photovoltaic module PN from the cable and not supply power to the bus bar, and the local device JN, such as a shutdown device, may restore the disconnected photovoltaic module PN to the cable and supply power to the bus bar again. For example, a positive output of native device J1 is connected to positive bus B1 and a negative output of native device JN is connected to negative bus B2. And the positive output end of the latter local device in the plurality of series-connected local devices is connected to the negative output end of the adjacent former local device, or the positive output end of the latter local device in the plurality of stages of local devices is connected to the negative output end of the adjacent former local device, so that the plurality of local devices are connected in series to form a battery string. Each photovoltaic module in the battery string is configured with a local device receiving the output power thereof, for example, any one photovoltaic module PN in the battery string is configured with a local device JN receiving the output power of the photovoltaic module PN, and a plurality of local devices corresponding to the plurality of photovoltaic modules P1 to PN in any battery string are connected in series with each other, for example, J1 to JN in series, through cables. The connection relationships of the local devices here apply to the examples of fig. 1-6.

Referring to fig. 7, the arc sensor may be integrated with a shut-off device (e.g., JN) and the shut-off device is then used to remove individual photovoltaic modules PN from the string STM or to reconnect the removed photovoltaic modules PN back into the string STM. An arc sensor, not shown, is used to detect an arc at the photovoltaic module.

Referring to fig. 7, a bypass diode or a complementary switch may be disposed between the positive output terminal (first output terminal) and the negative output terminal (second output terminal) of the native device JN. The complementary switch is a switch complementary to switch S1: if switch S1 is on then its complementary switch is turned off and switch S1 is off then its complementary switch is turned on. The meaning of arranging the bypass diode or the complementary switch is to prevent the battery string from forming an open circuit at the local device JN. The bypass diode or the complementary switch of the local device JN is switched on if the photovoltaic module PN is switched off. If the photovoltaic module PN is restored to the cable or to the battery string, the bypass diode or the complementary switch is turned off.

Referring to fig. 7, the local device JN may set a switch S1 between the negative electrode of the photovoltaic module PN and the conductive cable or may alternatively set 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 collection module, if the target data are found to be abnormal, the local device JN can be controlled by the controller IC1 to turn off the photovoltaic module PN, for example, the controller IC1 is used for operating to turn off the switch S1, and the controller IC1 can drive or control the switch S1 to turn off no matter whether the initial voltage or the initial current of the photovoltaic module is abnormal or the output voltage or the output current of the cable output by the local device is abnormal. 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 turn-off instruction, the local device will actively drive or control the switch S1 to turn off when receiving such an instruction. Meanwhile, 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 turn-off or turn-on of the shutdown switch S1 of the photovoltaic module configuration to control whether the photovoltaic module P1 is turned off or not. And so on, other optional examples also support shutdown management, such as the local device J2 supporting the rapid shutdown of the pv module P2 is used to operate the shutdown switch S1 of the pv module configuration to turn off or on to control whether the pv module P2 is turned off or not. The local device is illustrated as an optional example in this example as a shutdown device, although the wired communication function and the wireless communication function of the local device and the concentrator described above are also applicable to this example, and both the local device and the concentrator have the bidirectional communication capability. The shutdown device removes the photovoltaic module from the battery string or restores the photovoltaic module in the removed state to be connected to the battery string again.

Referring to fig. 7, the concentrator 150 reads the target data of each of the photovoltaic modules P1 to PN, such as the voltage supplied to the cable and the branch current supplied to the cable, by: the concentrator 150 polls the series of local devices J1-JN corresponding to the photovoltaic modules P1-PN in sequence, and when the concentrator 150 polls any local device, such as JN, the queried local device, such as JN, needs to return the target data of the corresponding photovoltaic module PN to the concentrator 150. This data reading mode is now described by way of example: when the controller IC2 of the concentrator 150 queries the local device, such as J1, the controller IC1 of the queried local device, such as J1, needs to return the target data of the photovoltaic module P1 to the controller IC2. Continuing by way of example, this manner of data reading: when the controller IC2 of the concentrator 150 queries a local device such as J2, the controller IC1 of the queried local device such as J2 needs to return the target data of the photovoltaic module P2 to the controller IC2. In summary, such data reading can be considered as: the controllers configured by the concentrator, i.e., the master node, poll the respective local devices, i.e., the controllers configured by the slave nodes, in turn, and when the concentrator polls any one of the local devices, the controller of the queried local device returns target data of a corresponding one of the photovoltaic modules, such as a voltage to the cable and a branch current to the cable, to the controller configured by the concentrator. To avoid confusion, the controller of a local device may be referred to as a first controller and its communication module may be referred to as a first communication module, while the controller of the concentrator may be referred to as a second controller and its communication module may be referred to as a second communication module. Other alternatives to the controller are: a field programmable gate array or a complex programmable logic device or a field programmable analog gate array or a semi-custom ASIC or processor or microprocessor or digital signal processor or integrated circuit or a software firmware program stored in a memory, etc. The polling data reading method is also applicable to a shutdown device, a power optimizer, a voltage converter and the like besides the illustrated photovoltaic junction box.

Referring to fig. 8, each of the pv modules P1-PN is configured with a voltage converter, which is also called a switching regulator and is most commonly represented by switching power supply circuit topologies such as buck converter, boost converter, buck-boost converter, etc. The controller IC1 of the local device JN is usually designed as a driving chip, and the controller drives a voltage converter or a converting circuit to convert the input voltage drawn from the photovoltaic module P1 into an output voltage, the voltage converter is also called a power stage circuit, the controller IC1 is also called a power controller, and the controller IC1 is most commonly a power management controller or a power management chip for managing the switching power supply in the industry. This example allows the local device to simply perform a basic step-down conversion or step-up conversion on the initial voltage of the photovoltaic module, for example, the output voltage of the local device is regarded as the partial voltage of the output of the photovoltaic module to the bus, and the initial voltage of the photovoltaic module is transmitted to the local device, and the output voltage of the local device is the voltage obtained by stepping-down or stepping-up the initial voltage of the photovoltaic module. The local device does not need power optimization at this time.

Referring to fig. 8, the arc sensor is integrated with a voltage converter (e.g., JN) and the voltage converter at this time is used to perform a step-up voltage conversion or a step-down voltage conversion on the initial voltage of the photovoltaic module PN. An arc sensor, not shown, is used to detect an arc at the photovoltaic module.

With reference to fig. 8, the issues of concern in distributed or centralized photovoltaic power plants are: shadow occlusion causes a mismatch among numerous photovoltaic modules. The problem is that the battery output characteristics of the photovoltaic module are represented by the fact that the output voltage and the output current are closely related to external factors such as light intensity and ambient temperature, and the uncertainty of the external factors causes the corresponding voltages of the maximum output power and the maximum power point to change along with the change of the external factors. For example, the power output by the photovoltaic module has randomness and severe fluctuation, and the random uncontrollable characteristic has high probability of causing great impact on the power grid and may also cause negative influence on the operation of some important loads. Based on these doubts, achieving maximum power point tracking of photovoltaic modules in consideration of external factors is a core goal of the industry to maximize energy and revenue.

Referring to fig. 8, the principle and features of a conventional MPPT method for power optimization: for example, in the early output power control for photovoltaic modules, a Voltage feedback method Constant Voltage Tracking is mainly used, and the Tracking method ignores the influence of temperature on the open-circuit Voltage of the solar cell, so that an open-circuit Voltage method and a short-circuit current method are proposed, and the common property of the open-circuit Voltage method and the short-circuit current method is basically very similar to the maximum power point. In order to more accurately capture the maximum power point, a disturbance observation method, a duty ratio disturbance method, a conductance increment method and the like are proposed. The principle of the disturbance observation method is that the current array power is measured, then a small voltage component disturbance is added to the original output voltage, the output power changes, the changed power is measured, the power before and after the change is compared, the direction of the power change can be known, if the power is increased, the original disturbance is continuously used, and if the power is decreased, the original disturbance direction is changed. The duty ratio disturbance working principle is as follows: the interface between the photovoltaic array and the load generally adopts a voltage converter controlled by a pulse width modulation signal, so that the input and output relationship of the converter can be adjusted by adjusting the duty ratio of the pulse width modulation signal, and the function of impedance matching is realized, and therefore, the magnitude of the duty ratio substantially determines the magnitude of the output power of the photovoltaic cell. The incremental conductance method is a special way to the disturbance observation method, the biggest difference is only in the logical judgment formula and the measurement parameters, although the incremental conductance method still changes the output voltage of the photovoltaic cell to reach the maximum power point, the logical judgment formula is modified to reduce the oscillation phenomenon near the maximum power point, so that the incremental conductance method is suitable for the climate with instantaneous change of the sunlight intensity and the temperature. Practical measurement methods, fuzzy logic methods, power mathematical models, intermittent scanning tracking methods, optimal gradient methods or three-point gravity center comparison methods and the like belong to the most popular maximum power point tracking methods. Therefore, the MPPT algorithm used in the photovoltaic energy industry is diversified, and repeated description is omitted in the application.

Referring to fig. 8, each of the pv modules P1-PN is configured with a voltage converter, but the voltage converter is not only simple voltage conversion but also has a power optimization function, and is also called an optimizer. Each power optimizer is used to set the initial current and initial voltage of the photovoltaic module corresponding thereto at the maximum power point. For example, a local device J1 such as a power optimizer is shown to set the corresponding pv module P1 at the maximum power point, a local device J2 such as a power optimizer is shown to set the corresponding pv module P2 at the maximum power point, and a local device JN such as a power optimizer is shown to set the corresponding pv module PN at the maximum power point. The power optimizer performs a power optimization function on the photovoltaic module, and in this example, the controller IC1 of the local device JN may be configured to operate the power optimizer to perform voltage conversion actions such as voltage boosting, voltage dropping, or voltage boosting, so as to set the initial current and the initial voltage of the photovoltaic module, that is, the input voltage and the input current of the local device, to the maximum power point of the photovoltaic module PN. The local equipment may also be provided with power management functions to maximize the efficiency of the photovoltaic module.

Referring to fig. 8, the power optimizer is a dc-to-dc converter, which is also a single component level battery maximum power tracking device. After the single component is optimized to the maximum power by the power optimizer, the collected total power is transmitted to the inverter to be converted from direct current to alternating current, and then the converted total power is supplied to local use or is directly connected to the grid. The inverter may typically be a pure inverter device without maximum power tracking or an inverter device equipped with two-stage maximum power tracking. The main topology of mainstream power optimizers is, for example, conventional BUCK or BOOST or BUCK-BOOST or CUK circuit architectures.

Referring to fig. 8, the arc sensor is integrated with a power optimizer (e.g., JN) and the power optimizer is then used to set the photovoltaic module PN at its maximum power point. An arc sensor, not illustrated, is used to detect an arc at the photovoltaic module.

Referring to fig. 9, the photovoltaic modules P1-PN supply power to the bus in series, and the dc arc fault determination results are collected at each of the photovoltaic modules P1-PN. The local device J1 of the photovoltaic module P1 collects the dc arc fault determination result thereof, the local device J2 of the photovoltaic module P2 collects the dc arc fault determination result thereof, and so on, it can be known that the local device JN of the photovoltaic module PN collects the dc arc fault determination result thereof.

Referring to fig. 9, the local device J1 sends the dc arc fault determination result at the photovoltaic module P1, which is collected by the arc sensor at the photovoltaic module P1, to the concentrator 150.

Referring to fig. 9, the local device J2 sends the dc arc fault determination result at the photovoltaic module P2, which is collected by the arc sensor at the photovoltaic module P2, to the concentrator 150.

Referring to fig. 9, the local device JN sends the dc arc fault determination result at the photovoltaic module PN, which is collected by the arc sensor at the photovoltaic module PN, to the concentrator 150.

Referring to fig. 9, after the concentrator 150 knows the dc arc fault determination result at each photovoltaic module, the concentrator can analyze whether the dc arc fault determination result is an arc event caused by an interference signal according to the dc arc fault determination result transmitted by each battery string ST 1-STM: if the arc sensors of all the battery pack strings reflect that the direct current arc fault occurs, the arc event is considered to be caused by interference signals coupled to the battery pack strings; if only the arc sensors of one part of the battery strings reflect that the direct current arc fault occurs, and the arc sensors of the other part of the battery strings do not reflect that the direct current arc fault occurs, the arc event is not caused by interference signals coupled to the battery strings, and therefore the interference situation of the interference signals (such as high-frequency harmonic bur) to the arc event is screened.

Referring to fig. 9, the concentrator 150 includes a cut-off switch S2 disposed on the cable, and the cut-off switch S2 may be disposed on the positive bus bar or the negative bus bar. The concentrator 150 can control the cut-off switch S2 to be turned off so that the cable can be immediately disconnected. The concentrator 150 includes a controller IC2, and the controller IC2 analyzes and determines the dc arc fault determination result transmitted by each battery string to analyze whether the dc arc fault is an arc event caused by an interference signal, and supplies power to the bus from each battery string, and if the dc arc fault determination result is not caused by the interference signal coupled to each battery string, the concentrator controls to switch a switch (e.g., a disconnecting switch S2) disposed on the bus to an off state. Controller IC2 determines that the arc event is not caused by coupling to a jamming signal at the respective battery string, but is a real arc, and controller IC2 may drive switch S2 to turn off, for example using a microprocessor.

Referring to fig. 9, the accidents of arcing and firing caused by poor contact, aging, short circuit and the like are more and more frequent, and detection of visible direct current arc faults is increasingly important in photovoltaic systems. Once a photovoltaic system has a direct current arc fault, the fault arc of the system has a stable combustion environment because zero crossing point protection is not provided and the photovoltaic module generates continuous energy under the irradiation of sunlight. If measures are not timely and effectively taken, high temperature phenomena of more than thousands of degrees can be generated, fire disasters can be caused, and certain substances are melted and even evaporated to generate a large amount of toxic gases, so that the life safety of people is endangered, and the social economy is greatly lost.

Referring to fig. 9, dividing the arc according to the nature of the current can be roughly divided into a direct current arc and an alternating current arc. The well-known alternating current application time is earlier, and alternating current fault arcs exist mature detection methods and commercial products, however, the starting time of a photovoltaic system is later, and the nature characteristics of a direct current arc are different from that of alternating current, and a zero-crossing point characteristic exists in a typical situation that direct current does not have alternating current, so that the alternating current arc detection means cannot be applied to photovoltaic occasions. The method and the device detect real direct current arc faults existing in the photovoltaic system so as to avoid serious accidents such as fire disasters caused by fault arcs.

Referring to fig. 9, it is noted that an arc event is not necessarily a highly dangerous dc arc fault. Actions such as plugging and unplugging switches or motor rotation can cause arcing in electrical power systems, but such arcing does not persist but is transient and can also slightly affect the normal operation of the systems and equipment, which is referred to as a good arc. Besides normal electric arcs, electric arcs which are caused by short circuit of lines, insulation aging, poor contact of the lines and the like, can continuously burn and are easy to ignite surrounding inflammable substances are called bad arcs and direct-current fault arcs. Plug switches or motor rotation also belong to interference signals.

Referring to fig. 9, for example, a positive output terminal of the local device J1 is connected to the positive bus B1 and a negative output terminal of the local device JN is connected to the negative bus B2, and a positive output terminal of a subsequent local device in the plurality of local devices connected in series is connected to a negative output terminal of an adjacent previous local device, or a positive output terminal of a subsequent local device in the plurality of local devices is connected to a negative output terminal of an adjacent previous local device, thereby connecting the plurality of local devices in series to form a battery string. Each photovoltaic module in the battery string is configured with a local device receiving the output power thereof, for example, any one photovoltaic module PN in the battery string is configured with a local device JN receiving the output power of the photovoltaic module PN, and a plurality of local devices corresponding to the plurality of photovoltaic modules P1 to PN in any battery string are connected in series with each other, for example, J1 to JN in series, through cables.

Referring to fig. 9, each photovoltaic module PN is provided with a local device JN for collecting arc information thereof, and a concentrator 150 is provided on the bus bar or cable at least for collecting arc conditions of the respective battery strings. Communication is established between the local equipment and the concentrator, and the local direct current arc fault condition of each photovoltaic module JN is sent to the concentrator by the local equipment configured for each photovoltaic module JN, and the concentrator 150 judges whether a real fault occurs at the battery string ST 1-STM. It is determined whether an arc event is caused by an interfering signal coupled to each battery string or is caused by a non-interfering signal.

Referring to fig. 9, the local device JN includes a first controller IC1 and a first communication module CM1 and the concentrator 150 includes a second controller IC2 and a second communication module CM2; and the first controller IC1 of the local device JN transmits the arc fault result of the corresponding photovoltaic module PN to the management device 100 using the assorted first communication module CM 1. The second controller IC2 of the concentrator receives the arc fault results for each battery string by the second communication module CM2 and determines whether a fault has occurred at each battery string by the second controller. The mode of communication between the local device JN and the concentrator 150 includes at least power line carrier communication, wireless communication, or the like.

Referring to fig. 3, if it is preliminarily considered that an arc event is caused by an interference signal (harmonic bur, inter-harmonic generated by plugging and unplugging a switch, rotation of a motor, or load fluctuation), it is established on the premise that the following conditions need to be satisfied: i.e. further confirming that the arc event is indeed caused by a disturbing signal, is that all parallel battery strings ST1-STM have dc arc faults with the same arc characteristics, i.e. the same arc characteristics at least including the arc frequency of the arc signal or dc arc fault at the respective battery string ST1-STM falling in the same one of the frequency bands.

Referring to fig. 2, the interference signal also includes illumination-related inter-harmonic components generated by the inverter on the bus side: the random variation of the illumination will cause the dc voltage of the photovoltaic output to fluctuate randomly, or the bus voltage to fluctuate randomly, and at this time, complex inter-harmonic components may be generated on both the dc side and the ac side through the interaction of the ac side and the dc side of the inverter.

Referring to fig. 2, the interference signal further includes a bus side harmonic component caused by maximum power point tracking of the inverter: in the stage of implementing Maximum Power Point Tracking (MPPT) by the inverter, the direct-current voltage instruction of the inverter needs to be controlled and continuously adjusted to expect to obtain the maximum power output of the bus side, so that the voltage fluctuation of the direct-current side of the inverter is caused. In this case, the maximum power point tracking operation of the inverter generates inter-harmonic components on the dc side and the ac side.

Referring to fig. 3, in an alternative embodiment, a photovoltaic module-level arc detection method supporting immunity to interference, is comprised of a plurality of battery strings connected in parallel and each battery string including a plurality of photovoltaic modules connected in series: monitoring a dc arc fault at each battery string individually (i.e. monitoring the respective arc conditions of ST1 to STM separately); the dc arc faults at each battery string are analyzed collectively (i.e., the arc conditions of ST1 to STM, respectively, are analyzed collectively): if all battery strings have a dc arc fault, then the arc event is considered to be caused by an interference signal coupled to each battery string, i.e., it is not a true arc; if only a portion of the battery strings (e.g., ST1/ST 2) have dc arc faults and another portion of the battery strings (e.g., STM) remain without dc arc faults, then the arc event is deemed not to be caused by coupling to the interference signal at the respective battery strings, but rather to be a true fault arc.

Referring to fig. 3, in an alternative embodiment, if an arc event is considered to be caused by an interference signal, the precondition is that all parallel battery strings have dc arc faults with the same arc characteristics, which requires the same arc characteristics to at least include that the arc signals at each battery string fall in the same frequency band.

Referring to fig. 10, if the respective arc sensors of all of the battery strings (e.g., ST1-ST2 and STM) reflect the occurrence of a dc arc fault, it is particularly the case that some erroneous determination of an arc event will occur if the arc event is directly interpreted without discrimination as being caused by some interference signal coupled to the respective battery string. Such as where dc arc faults at certain strings (e.g., ST1-ST 2) do originate from certain interfering signals, but where dc arc faults at certain strings (e.g., STMs) are true arcs local to the photovoltaic modules, determining that an arc event is caused by an interfering signal coupled to each string can be misbiased. This is a difficult problem, although not ubiquitous, but is subject to random occurrences.

Referring to fig. 10, in an alternative example, if the arc sensors of all the battery strings reflect that the dc arc fault occurs, the time interval during which the inverter performs maximum power optimization MPPT needs to be shortened at the inverter, so that the voltage ratio of the disturbance signal to the bus voltage is forced to bounce frequently at the stage when the inverter performs maximum power optimization, and if a situation occurs again that "the arc sensors of a part of the battery strings reflect that the dc arc fault occurs and the arc sensors of the other part of the battery strings do not reflect that the dc arc fault occurs", the situation that the arc event is caused by the disturbance signal coupled to each battery string is eliminated, and instead, the dc arc faults at some battery strings (e.g., ST1-ST 2) are considered to be actually caused by the so-called disturbance signal, but at the same time that the dc arc faults at other battery strings (e.g., STMs) are true arcs of the photovoltaic module (non-false, true dc fault arcs). Note that dc arc fault determinations from interfering signals tend to be false, non-true dc fault arcs. On the contrary, if the situation that the arc sensors of a part of the battery strings reflect that the direct current arc fault occurs and the arc sensors of the other part of the battery strings do not reflect that the direct current arc fault occurs does not occur at this time, it is finally confirmed that the arc event is caused by the interference signal coupled to each battery string, and not the real arc locally occurring at the photovoltaic module. The moment of identification of whether this analysis is an arc event caused by a disturbance signal is only present in the transient in which the inverter performs maximum power optimization. Such a transient occurs, for example, during a time when the inverter performs maximum power optimization to regulate the bus voltage and bus current. That is to say that the inverter performs a maximum power optimization is a prerequisite for analyzing whether it is an arc event caused by a disturbance signal.

Referring to fig. 10, in an alternative example, if a dc arc fault occurs in all the strings, the time interval for the inverter to perform maximum power optimization MPPT needs to be shortened at the inverter, so that the voltage ratio of the disturbance signal to the bus voltage is forced to bounce frequently at the stage of the inverter performing maximum power optimization, and if a situation occurs again that "only part of the strings has a dc arc fault and the rest of the strings has no dc arc fault", the situation that the arc event is caused by the disturbance signal coupled to each string is eliminated, and instead, the dc arc faults (e.g., ST1-ST 2) at some strings are actually caused by the so-called disturbance signal, but at the same time, the dc arc faults (e.g., STMs) at other strings are real arcs (non-false, real dc fault arcs) occurring locally at the photovoltaic module. At this time, if the situation that only part of the battery strings have direct current arc faults and the rest of the other battery strings have no direct current arc faults does not occur, it is finally confirmed that the arc events are caused by interference signals coupled to the respective battery strings and are not real arcs locally occurring on the photovoltaic module.

Referring to fig. 10, in an alternative example, if the arc sensors of all the battery strings reflect that the dc arc fault occurs, the inverter is made to change the amplitude of the bus voltage greatly when performing the maximum power optimization MPPT, and the voltage ratio of the interference signal to the bus voltage is guided to make a sharp jump at the stage of performing the maximum power optimization by the inverter, and if a situation occurs again that "the arc sensors of a part of the battery strings reflect that the dc arc fault occurs and the arc sensors of the other part of the battery strings do not reflect that the dc arc fault occurs", the arc event is excluded from being caused by the interference signal coupled to each battery string, and it is considered that instead the dc arc fault at some battery strings (e.g., ST1-ST 2) actually originates from the so-called interference signal, but at the same time the dc arc fault at other battery strings (e.g., STM) is a true arc (non-false, true dc fault arc) occurring locally in the photovoltaic module. If, on the contrary, no "the arc sensors of a part of the battery strings reflect that the dc arc fault occurs, and the arc sensors of the other part of the battery strings do not reflect that the dc arc fault occurs", it is finally confirmed that the arc event is caused by the interference signal coupled to each battery string, rather than the real arc locally occurring at the photovoltaic module.

Referring to fig. 10, in an alternative example, if all the strings have dc arc faults, the inverter is enabled to adjust the amplitude of the bus voltage greatly when performing maximum power optimization MPPT, and the voltage ratio of the interference signal to the bus voltage is guided to jump sharply at the stage when the inverter performs maximum power optimization, and if a situation that "only part of the strings have dc arc faults and the rest of the strings have no dc arc faults" occurs again, the situation that the arc events are caused by the interference signals coupled to the strings is eliminated, and instead, the dc arc faults (e.g., ST1-ST 2) at some strings are actually caused by the interference signals, but at the same time, the dc arc faults (e.g., STMs) at other strings are real arcs (non-false, real dc arcs) occurring locally at the photovoltaic modules. If, on the other hand, there is no "dc arc fault only in a portion of the strings, while there is no dc arc fault in the remaining portion of the strings", it is finally confirmed that the arc event is caused by coupling to a disturbance signal at the respective string, rather than a real arc occurring locally at the photovoltaic module.

Referring to fig. 10, in an alternative example, the time interval of the maximum power optimization MPPT performed by the compression inverter or the amplitude of the bus voltage greatly adjusted by the inverter when performing the maximum power optimization MPPT is set, based on these conditions, if it is further required that "the arc sensor is further integrated with a power optimizer for setting the photovoltaic module at its maximum power point", in the phase of the maximum power optimization performed by the inverter, the output voltage of the power optimizer is forced to follow the adaptive fluctuation and flicker of the inverter when performing the maximum power optimization, so as to further increase the frequency of the bounce of the voltage ratio of the interference signal to the bus voltage in the phase of the maximum power optimization performed by the inverter, or to increase the frequency of the bounce of the voltage ratio of the interference signal to the bus voltage in the phase of the maximum power optimization performed by the inverter. This is useful for analyzing whether an arc event is caused by a disturbing signal.

Referring to fig. 10, based on the monitored pressure of the arc, it is necessary to establish a reasonable monitoring and management mechanism by which component-level arc data can be extracted from the component boards and fed back to the owner or user. Real-time parameters such as voltage and current, electric arc, power and ambient temperature of the photovoltaic modules need to be monitored in time, and particularly abnormal conditions such as electric arc or fault of the modules need to be monitored in time, so that monitoring data information can provide a basis for improving and optimizing each photovoltaic module, and the fault or aged modules can be quickly positioned and repaired in time. Communication problems with photovoltaic module monitoring systems are involved whether attempts are made to achieve active control of the battery module by an external device or to send parameter information of the battery module locally to the external device. The intelligent management of the photovoltaic module comprises safety management, turn-off management, output power management and the like of the photovoltaic module besides conventional working parameter monitoring.

With reference to fig. 10, and in summary, it can be known that the present application claims to use an arc detection method supporting anti-interference at the photovoltaic module level to discriminate the interference situation of the interference signal to the arc event, and unlike the conventional scheme, the present application focuses on eliminating the interference of the interference signal to the arc identification, and avoids misunderstanding the plausible false arc as a real arc. The core of the application is to realize a photovoltaic module-level arc detection method supporting anti-interference, and the application achieves an anti-interference technology realization method for photovoltaic module-level arc detection, which are the subject matters or subjects of the application.

While the above specification concludes with claims defining the preferred embodiments of the invention that are presented in conjunction with the specific embodiments disclosed, it is not intended to limit the invention to the specific embodiments disclosed. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. An anti-interference technology implementation method for photovoltaic module level arc detection is characterized in that a plurality of battery strings are connected in series and parallel, each battery string comprises a plurality of photovoltaic modules connected in series, and the method comprises the following steps:

2. The method of claim 1, wherein:

an inverter is supplied by each series of parallel-connected battery cells, one of the sources of the interference signals comprising at least the high-frequency harmonics generated by the inverter during the operating phase.

3. The method of claim 1, wherein:

and the arc sensor configured in the battery pack string sends a direct current arc fault judgment result locally provided by the battery pack string to the concentrator in a power line carrier or wireless communication mode.

4. The method of claim 1, wherein:

the arc sensor is also 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 also integrated with a shut-off device for removing individual photovoltaic modules from the string or for restoring a removed photovoltaic module back into the string.

6. The method of claim 1, wherein:

the arc sensor is also integrated with a power optimizer for setting the photovoltaic module at its maximum power point.

7. The method of claim 1, wherein:

the arc sensor is also integrated with a voltage converter for performing step-up or step-down voltage conversion of the initial voltage of the photovoltaic module.

8. The method of claim 1, wherein:

the bus is supplied with power from each battery string, and a switch disposed on the bus is switched to an off state by the concentrator control if an arc event is found not to be caused by an interference signal coupled to each battery string.

9. The utility model provides a photovoltaic module level arc detection's anti-jamming technique implementation method, by a plurality of batteries group series parallel connection and every battery group string all includes a plurality of photovoltaic module of series connection, its characterized in that:

monitoring a dc arc fault at each battery string individually; and

the dc arc faults at each battery string were analyzed centrally:

if a DC arc fault occurs in all battery strings, then the arc event is considered to be caused by interference signals coupled to the respective battery strings;

10. The method of claim 1, wherein:

if the arc event is considered to be caused by the interference signal, it is assumed 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 each battery string fall in the same frequency band.