An AFCI self-testing system

Abstract

This application discloses an AFCI self-test system applied to a string photovoltaic system. It includes a controller, a self-test module, multiple measurement modules, and multiple main coils. The controller generates self-test signals and performs fault analysis on feedback signals. Each main coil is adapted to correspond to the current of the photovoltaic modules in each string. The input terminal of the self-test module is electrically connected to the controller to receive self-test signals, and the self-test module applies self-test signals by cooperating with the main coils through its output self-test coil. The output terminals of the measurement modules are all electrically connected to the controller, and each measurement module cooperates with the main coils through its input measurement coil to receive feedback signals from the main coils and send them to the controller. The advantages of this application are: it can realize the AFCI self-test function of a string photovoltaic system, the implementation method is simple, and it can effectively suppress coil interference problems under multiple strings.

Description

Technical Field

[0001] This application relates to the field of inverter technology, and in particular to an AFCI self-test system. Background Technology

[0002] According to safety regulations for AFCI (Arc Fault Interrupter), AFCI requires self-testing. Specifically, an AFCI self-test must be performed when the inverter is first powered on, and grid connection is only permitted after a successful self-test. Simultaneously, to ensure the inverter's operational safety, it is necessary to allow users to perform manual self-tests during inverter operation. If hardware failures such as those in the current transformer (CT) or sampling circuit are detected, the AFCI self-test must be able to issue an alarm. A "self-test failure" fault can only be cleared by performing a second, successful self-test, or by powering down and restarting the inverter; therefore, a hardware self-testing circuit is required to implement the AFCI system's self-testing. However, existing AFCI self-testing solutions are mainly for distributed photovoltaic systems, and there is a lack of AFCI self-testing solutions for string photovoltaic systems. Summary of the Invention

[0003] One objective of this application is to provide an AFCI self-testing system that can solve at least one of the defects in the aforementioned background art.

[0004] To achieve at least one of the above objectives, the technical solution adopted in this application is as follows: an AFCI self-test system applied to a string photovoltaic system; comprising a controller, a self-test module, multiple measurement modules, and multiple main coils; the controller is used to generate self-test signals and perform fault analysis of feedback signals; each of the main coils is adapted to be connected to the current of the photovoltaic modules in each string; the input terminal of the self-test module is electrically connected to the controller to receive the self-test signal, and the self-test module applies the self-test signal by cooperating with the main coil through the self-test coil at its output terminal; the output terminals of the measurement modules are all electrically connected to the controller, and each measurement module cooperates with the main coil through the measurement coil at its input terminal to receive the feedback signal from the main coil and send it to the controller.

[0005] Preferably, the self-test module includes a self-test signal generation unit and a plurality of self-test coils; the input terminal of the self-test signal generation unit is electrically connected to the controller, and the output terminal of the self-test signal generation unit is connected to the first terminal of the self-test coil; the self-test signal generation unit is adapted to amplify the self-test signal output by the controller, and then apply the amplified self-test signal to the main coil through the self-test coil.

[0006] Preferably, the first end of each self-test coil is connected in parallel to the output end of the self-test signal generation unit via a control switch, and the second end of each self-test coil is connected to a constant positive potential; the control switch is signal-connected to the controller so that the control switch is closed or opened under the control of the controller, thereby connecting or disconnecting the self-test coil.

[0007] Preferably, the self-test coils are connected in series, with the first end of the first self-test coil connected to the output of the self-test signal generation unit, and the second end of the last self-test coil connected to a constant positive potential. The output of the self-test signal generation unit is also provided with a control switch, which is signal-connected to the controller so that the control switch is closed or opened under the control of the controller, thereby connecting or disconnecting the self-test coil from the self-test signal generation unit.

[0008] Preferably, the self-test module includes multiple self-test signal generation units and multiple self-test coils; the input terminal of each self-test signal generation unit is electrically connected to the controller, the output terminal of each self-test signal generation unit is connected to the first terminal of the corresponding self-test coil, and the second terminal of each self-test coil is connected to a constant positive potential; the self-test signal generation unit is adapted to amplify the self-test signal output by the controller, and then apply the amplified self-test signal to the corresponding main coil through the self-test coil connected to it.

[0009] Preferably, the total number of channels in the entire array is N, and the measurement module is configured with N groups, each group including two measurement modules; the self-test module includes a self-test signal generation unit, and the measurement coils corresponding to the input terminals of the two measurement modules in each group are connected to the output terminal of the self-test signal generation unit through a control switch; the control switch is a selection switch, so that the measurement coil of one of the measurement modules in each group is connected to the output terminal of the self-test module through the control switch to serve as the self-test coil, and at this time, the other measurement coil in the same group is connected to its corresponding measurement module through the control switch.

[0010] Preferably, the two measuring coils in each group are defined as the main measuring coil and the auxiliary measuring coil, respectively. Before the string photovoltaic system is powered on normally, the two measuring coils in each group are used as self-test coils in turn for self-testing. During normal operation of the string photovoltaic system after self-testing, the two measuring coils in each group are connected to the corresponding measuring module through the control switch. If the difference between the feedback signals monitored by the two measuring modules in a certain group is greater than a set threshold, the measuring coils corresponding to the two measuring modules in that group are used as self-test coils in turn for self-testing. If the auxiliary measuring coil can collect the self-test signal when the main measuring coil is used as the self-test coil, but the main measuring coil cannot collect the self-test signal when the auxiliary measuring coil is used as the self-test coil, it indicates that the measuring module corresponding to the main measuring coil has failed. In this case, AFCI detection is performed only through the measuring module corresponding to the auxiliary measuring coil, and the controller alarms the measuring module corresponding to the main measuring coil for failure. If the measurement data when the main measuring coil and the auxiliary measuring coil are used as self-test coils in turn are consistent but the overall response is abnormal, it indicates that the two measuring coils have core failures.

[0011] Preferably, the self-test module includes one self-test signal generation unit, the output of which is connected in parallel with the control switch corresponding to each group of measurement coils; or, the self-test module includes N self-test signal generation units, the output of which is connected to the corresponding group of measurement coils via the control switch; wherein, N > 1.

[0012] Preferably, the reference potential of the measuring coil is a positive potential or GND.

[0013] Preferably, the measurement module includes the measurement coil, the filter circuit, and the sampling circuit connected in series.

[0014] Compared with the prior art, the beneficial effects of this application are as follows:

[0015] The technical solution of this application can realize the AFCI self-test function of string photovoltaic system. The implementation method is simple and can effectively suppress coil interference problem under multiple strings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the architecture of an existing string photovoltaic system.

[0017] Figure 2 This is a schematic diagram of the overall structure of this application.

[0018] Figure 3 This is a schematic diagram of the architecture of Embodiment 1 of this application.

[0019] Figure 4 For this application Figure 3 In the architecture shown, the voltage signal v IO v o and v test A schematic diagram of the waveform structure.

[0020] Figure 5 For this application Figure 3 The diagram shows the equivalent circuit structure of the architecture.

[0021] Figure 6 This is a schematic diagram of the architecture of Embodiment 2 of this application.

[0022] Figure 7 This is a schematic diagram of the architecture of Embodiment 3 of this application.

[0023] Figure 8 This is a schematic diagram of the architecture of Embodiment 4 of this application.

[0024] Figure 9 This is a schematic diagram of the architecture of Embodiment 5 of this application.

[0025] Figure 10 For this application Figure 9 The schematic diagram of the main measuring coil serving as a self-test coil in the illustrated embodiment is shown.

[0026] Figure 11 For this application Figure 9 The schematic diagram of the sub-measuring coil serving as a self-test coil in the illustrated embodiment is shown.

[0027] In the diagram: Photovoltaic module 101, DC / DC unit 102, DC / AC unit 103, power grid 104, main coil 200, self-test module 300, self-test coil 301, self-test signal generation unit 302, measurement module 400, measurement coil 401, main measurement coil 4011, auxiliary measurement coil 4012, filter circuit 402, sampling circuit 403, controller 500. Detailed Implementation

[0028] The present application will now be further described in conjunction with specific embodiments. It should be noted that, in the description of this specification, the use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0029] In the description of this application, it should be noted that the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., which indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of this application.

[0030] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0031] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0034] One preferred embodiment of this application, such as Figure 1 and Figure 2 As shown, an AFCI self-test system is applied to a string photovoltaic system; it includes a controller 500, a self-test module 300, multiple measurement modules 400, and multiple main coils 200. The controller 500 is used to generate self-test signals and perform fault analysis on feedback signals. Each main coil 200 can be connected to the current of the photovoltaic module 101 in each string. The input terminal of the self-test module 300 is electrically connected to the controller 500 to receive self-test signals. The self-test module 300 cooperates with the main coils 200 through the self-test coil 301 at its output terminal to apply self-test signals. The output terminals of the measurement modules 400 are all electrically connected to the controller 500. Each measurement module 400 cooperates with the main coils 200 through the measurement coil 401 at its input terminal, thereby receiving feedback signals from the main coils 200 and sending them to the controller 500.

[0035] It should be understood that the specific structure of a string photovoltaic system is well known to those skilled in the art. For ease of understanding, the specific structure of a string photovoltaic system will be briefly described below. Figure 1As shown, the string photovoltaic system mainly includes N photovoltaic modules 101, N DC / DC units 102, and one DC / AC unit 103. Each photovoltaic module 101 is connected in parallel to the DC / AC unit 103 via a corresponding series-connected DC / DC unit 102. The AC side of the DC / AC unit 103 is connected to the power grid 104. The value of N is greater than 1. For ease of understanding, the N photovoltaic modules 101 can be labeled as PV#1 to PV#N, and the N DC / DC units 102 can be labeled as DC / DC#1 to DC / DC#N.

[0036] It is understandable that the number of main coils 200 is set to N, where N is greater than 1. The N main coils 200 are connected in parallel with the output terminals of each photovoltaic module 101, so that the output current of the photovoltaic module 101 can be extracted when the photovoltaic module 101 is working. If the output current of the photovoltaic module 101 changes irregularly, the measurement module 400 can measure the irregular current through the winding formed by the measurement coil 401 set at the input terminal and the main coils 200. Then, the measured irregular current can be converted into a fault signal and sent to the controller 500. After receiving the fault signal, the controller 500 will alarm and control the photovoltaic system to perform corresponding fault isolation actions, such as controlling the DC / DC unit 102 and the DC / AC unit 103 to drive and block.

[0037] The self-test of the AFCI mainly detects whether the main coil 200 and / or the measurement module 400 have malfunctioned. A malfunction in the main coil 200 and / or the measurement module 400 will prevent the AFCI from monitoring the output current waveform of the photovoltaic module 101. Therefore, a self-test module 300 is provided in this embodiment. Simultaneously, a self-test signal can be generated by the controller 500. The function of the self-test module 300 is to amplify the self-test signal generated by the controller 500 and send it to the main coil 200. It should be noted that the self-test signal is an AC signal. The self-test coil 301 of the self-test module 300 also forms a winding with the main coil 200. The main coil 200 can generate a corresponding AC signal through electromagnetic induction and transmit it as a feedback signal to the measurement coil 401. The measurement module 400 can then send the received feedback signal to the controller 500. If the feedback signal received by the controller 500 matches its own generated self-test signal, it indicates that the AFCI self-test system is working normally, i.e., the self-test is complete. Otherwise, it indicates that the AFCI self-test system has malfunctioned, and the type of malfunction can be analyzed based on the feedback signal.

[0038] There are various specific structures for the self-test module 300 to achieve the above functions, and there are also various specific architectures for the AFCI self-test system based on different self-test modules 300. For ease of understanding, five specific embodiments will be described in detail below.

[0039] Example 1:

[0040] like Figure 3 As shown, the number of measurement modules 400 is N; the self-test module 300 includes a self-test signal generation unit 302 and N self-test coils 301. The input terminal of the self-test signal generation unit 302 is electrically connected to the controller 500, and can thus receive the self-test signal v output by the controller 500. IO And amplify it. The output terminal of the self-test signal generation unit 302 is connected to the first terminal of the self-test coil 301, so that the self-test signal generation unit 302 can amplify the self-test signal v o The self-test signal is applied to the main coil 200 through the self-test coil 301. Each measurement module 400 cooperates with the corresponding main coil 200 through the measurement coil 401 at the input end to collect the self-test signal and send it as a feedback signal to the controller 500.

[0041] It is understood that the self-test signal generation unit 302 can employ a power amplifier circuit; the specific structure is well known to those skilled in the art, and therefore will not be described in detail here. Figure 4 As shown, the self-test signal v output by controller 500 IO It is an AC signal that varies frequently between 0 and 1; since the power supply voltage connected to the self-test signal generation unit 302 is V cc Then the self-test signal v IO The self-test signal v is amplified after passing through the self-test signal generation unit 302. o In V cc The change occurs between GND and the self-test signal; that is, the self-test signal v output by the self-test signal generation unit 302. o The value is not negative. In this embodiment, N self-test coils 301 are connected in parallel to the output terminal of the self-test signal generation unit 302 through the first terminal. If the second terminal of the self-test coil 301 is grounded, i.e. connected to GND, then the AC change of the self-test coil 301 will also be non-negative, which may lead to magnetic circuit saturation of the coil.

[0042] Therefore, in this embodiment, the second terminal of the self-test coil 301 can be connected to a constant positive potential, assuming that the positive potential is V. + Then the signal v output by the self-test coil 301 to the main coil 200 test The range of variation is (V cc -V + V + -V ccThat is, the output signal v of the self-test coil 301. test These are positive and negative alternating components, thus achieving positive and negative cancellation of the magnetic circuit. It should be noted that, to completely avoid magnetic circuit saturation, the output signal v of the self-test coil 301 needs to be guaranteed. test The amplitude is the same in both positive and negative directions, that is, the positive potential V + The value of V is cc / 2. For example... Figure 4 As shown, based on the value of the positive potential at the second terminal of the self-test coil 301, the output signal v of the self-test coil 301 is... test In +V cc / 2 and -V cc The variation is between / 2.

[0043] In this embodiment, as Figure 3 As shown, the first end of each self-test coil 301 is connected in parallel to the output end of the self-test signal generation unit 302 via a control switch S. The control switch S is signal-connected to the controller 500 so that the control switch S is closed or opened under the control of the controller 500, thereby connecting or disconnecting the self-test coil 301.

[0044] It should be understood that the control switch S can be a relay or other controllable switch, which can be selected according to the actual needs of those skilled in the art. During the AFCI self-test phase, the control switch S is closed, ensuring that the self-test coil 301 can be stably connected to the self-test signal generation unit 302 to receive the self-test signal v. o The control switch S is open during the normal AFCI detection phase, mainly to prevent coupling between the self-test coil 301 and the main coil 200, which would affect the measurement results.

[0045] Specifically, such as Figure 5 As shown, Figure 3 The diagram shows the equivalent circuit structure of the architecture. As can be seen from the diagram, if there is no control switch S or all control switches S are closed, the self-test coil 301 will interact with the corresponding main coil 200. Since all self-test coils 301 are directly connected in parallel, mutual coupling will occur among them, which will then act on the main coil 200, affecting the measurement result of the measuring coil 401. Therefore, the presence of control switch S can effectively prevent this coupling from occurring.

[0046] In this embodiment, the measurement module 400 has various specific structures. For ease of understanding, one of these structures will be described in detail below. Figure 3As shown, the measurement module 400 includes a measurement coil 401, a filter circuit 402, and a sampling circuit 403 connected in series. After acquiring the signal from the main coil 200, the measurement coil 401 obtains a feedback signal. This feedback signal undergoes ripple filtering by the filter circuit 402, and finally, the sampling circuit 403 transforms the feedback signal into a corresponding fault signal. For example, if a waveform change is detected in the feedback signal, the sampling circuit 403 can output a high-level fault signal to the controller 500; otherwise, it outputs a low-level normal signal to the controller 500. The specific structural types of the filter circuit 402 and the sampling circuit 403 are well-known to those skilled in the art and can be selected according to actual needs; for example, the filter circuit 402 can be an RC circuit.

[0047] In this embodiment, the controller 500 can be of various types, such as DSP and MCU. In this embodiment, a DSP is preferred for the controller 500. Figure 3 As shown, the controller 500 is connected to the output side of the sampling circuit 403 of the measurement module 400 via an ADC port; the controller 500 is connected to the input terminal of the self-test signal generation unit 302 via an IO port; the controller 500 is also connected to a drive circuit for driving the control switch S to close or open via an IO port. Since there are N measurement modules 400, the controller 500 also has N corresponding ADC ports, which can be defined as ADC#1 to ADC#N respectively.

[0048] Example 2:

[0049] like Figure 6 As shown, the difference between this embodiment and Embodiment 1 is that the second end of the measuring coil 401 is connected to the self-test coil 301. That is, the reference potential of the measuring coil 401 is a positive potential; more preferably, the reference potential of the measuring coil 401 is V. cc / 2. It is understandable that by limiting the reference potential of the measuring coil 401 to V... cc / 2, so that the measuring voltage of the measuring coil 401 is V cc The voltage fluctuates around 2 / 2, but remains positive, so the sampling circuit 403 of the measurement module 400 no longer needs DC boosting to perform the corresponding encoding. However, in the scheme of Embodiment 1, the reference potential of the measurement coil 401 is GND, causing the measured voltage to fluctuate around GND, resulting in both positive and negative values. Therefore, the sampling circuit 403 needs DC boosting before it can perform the corresponding encoding. Thus, the scheme of Embodiment 2 effectively reduces the design difficulty of the sampling circuit 403.

[0050] It should be noted that the measuring coil 401 may not be connected to the second terminal of the self-test coil 301, and the reference potential of the measuring coil 401 can be directly limited to a positive potential.

[0051] Example 3:

[0052] like Figure 7 As shown, the difference between this embodiment and Embodiment 1 is that the self-test module 300 includes N self-test signal generation units 302 and N self-test coils 301. The input terminal of each self-test signal generation unit 302 is electrically connected to the controller 500, the output terminal of each self-test signal generation unit 302 is connected to the first terminal of the corresponding self-test coil 301, and the second terminal of each self-test coil 301 is connected to a constant positive potential. The self-test signal generation unit 302 is adapted to amplify the self-test signal output by the controller 500, and then apply the amplified self-test signal to the corresponding main coil 200 through the self-test coil 301 connected to it.

[0053] It is understood that, compared with Embodiment 2, this embodiment expands the self-test signal generation unit 302 from one to N; that is, each string is equipped with a corresponding self-test signal generation unit 302. In this way, there will be no parallel connection between the N self-test coils 301, so the use of control switch S can be avoided.

[0054] It should be understood that, in this embodiment, the reference potential of the measuring coil 401 can be a positive potential V. cc / 2, or GND can be used.

[0055] Example 4:

[0056] like Figure 8 As shown, the difference between this embodiment and Embodiment 1 is that the N self-test coils 301 included in the self-test module 300 are connected in series, that is, the first self-test coil 301 is connected to the first end of the next self-test coil 301 through its second end. Among them, the first end of the first self-test coil 301 is connected to the output end of the self-test signal generation unit 302, and the second end of the last self-test coil 301 is connected to a constant positive potential.

[0057] At this time, it is only necessary to set a control switch S at the output end of the self-test signal generation unit 302. The control switch S is connected to the controller 500 so that the control switch S is closed or opened under the control of the controller 500, thereby connecting or disconnecting all the self-test coils 301 connected in series with the self-test signal generation unit 302.

[0058] It is understandable that the positive potential connected to the second terminal of the self-test coil 301 at the end is preferably V. cc / 2. For the reference potential of measuring coil 401, a positive potential V can be used. cc / 2, or GND can be used.

[0059] Example 5:

[0060] like Figure 9 As shown, the difference between this embodiment and Embodiment 1 is that the measurement module 400 is provided in N groups, with each group including two measurement modules 400. The self-test module 300 includes a self-test signal generation unit 302. The measurement coils 401 corresponding to the input terminals of the two measurement modules 400 in each group are connected to the output terminal of the self-test signal generation unit 302 through a control switch S. The control switch S is a selection switch, so that the measurement coil 401 of one of the measurement modules 400 in each group is connected to the output terminal of the self-test module 300 through the control switch S to serve as the self-test coil 301. At this time, the other measurement coil 401 in the same group is connected to its corresponding measurement module 400 through the control switch S.

[0061] Understandably, the measurement coils 401 corresponding to the two measurement modules 400 in each group can be defined as the main measurement coil 4011 and the auxiliary measurement coil 4012, respectively. Both the main measurement coil 4011 and the auxiliary measurement coil 4012 are equipped with control switches S. When the main measurement coil 4011 serves as the self-test coil 301 of the self-test module 300, the control switch S on the main measurement coil 4011 can be closed at the output terminal of the self-test signal generation unit 302; simultaneously, the control switch S on the auxiliary measurement coil 4012 can be closed at its corresponding measurement module 300. This achieves redundancy between the two measurement modules 400 in each group, thereby improving the stability during normal AFCI measurement; that is, if one measurement module 400 in each group fails, AFCI testing can continue through the other measurement module 400. Furthermore, by switching the control switch S, the measurement module 400 can switch between measurement and self-test functions, thus simplifying the self-test architecture while ensuring system measurement stability.

[0062] It should be noted that when the measuring coil 401 is used as the self-test coil 301, the control switch S corresponding to the measuring coil 401 disconnects the measuring coil 401 from the measuring module 400. At this time, the filter circuit 402 and the sampling circuit 403 corresponding to the measuring module 400 are both in an open circuit state.

[0063] In this embodiment, the redundancy replacement process for the two measurement modules 400 in each group in case of a fault is as follows: before the string photovoltaic system is powered on normally, such as... Figure 10 and Figure 11As shown, the two measuring coils 401 in each group are used as self-testing coils 301 in turn for self-testing. If both self-testing coils 301 can complete the self-test, it means that the two measuring modules 400 are working normally at this time.

[0064] During normal operation of the string photovoltaic system after self-testing, the two measuring coils 401 of each group are connected to the corresponding measuring module 400 through the control switch S. If the difference between the feedback signals monitored by the two measuring modules 400 of a certain group is greater than the set threshold, the specific value of the threshold can be selected by the person skilled in the art according to the actual needs. The measuring coils 401 corresponding to the two measuring modules 400 of the group take turns as self-testing coils 301 for self-testing.

[0065] like Figure 10 As shown, if the main measuring coil 4011 is used as the self-test coil 301, the auxiliary measuring coil 4012 can acquire the self-test signal; while when... Figure 11 As shown, when the secondary measuring coil 4012 acts as the self-test coil 301, the primary measuring coil 4011 cannot acquire a self-test signal, indicating that the measuring module 400 corresponding to the primary measuring coil 4011 has malfunctioned. In this case, AFCI detection is only performed through the measuring module 400 corresponding to the secondary measuring coil 4012, and the controller 500 alarms the primary measuring coil 4011's corresponding measuring module 400 for malfunction. If the measurement data of the primary measuring coil 4011 and the secondary measuring coil 4012 alternately acting as the self-test coil 301 are consistent but the overall response is abnormal, it indicates that the two measuring coils 401 have a magnetic core fault, such as magnetic core saturation, demagnetization, or other abnormalities.

[0066] Understandably, compared to the four embodiments mentioned above, this embodiment can prevent AFCI sampling faults without introducing other signals. Other signals are only introduced for fault location when a sampling fault is likely to occur, providing relatively accurate fault location capabilities while minimizing the impact of introducing self-test signals during system operation.

[0067] In this embodiment, as Figure 9 As shown, a positive potential, preferably V, can be connected to the output terminal of the self-test signal generation unit 302. cc / 2. Regarding the reference potential of the measuring coil 401, considering that the measuring coil 401 needs to be used as a self-test coil 301, and when used as a self-test coil 301, the self-test coil 301 will be connected to the positive potential connected to the output terminal of the self-test signal generation unit 302. In order to avoid mutual interference between the reference potential of the measuring coil 401 and the positive potential of the output terminal of the self-test signal generation unit 302, the reference potential of the measuring coil 401 is preferably GND.

[0068] In this embodiment, as Figures 9 to 11As shown, the self-test module 300 includes a self-test signal generation unit 302. The output of the self-test signal generation unit 302 can be connected in parallel with the control switch S corresponding to each group of measuring coils 401. Of course, the self-test module 300 may also include N self-test signal generation units 302, and the output of each self-test signal generation unit 302 can be connected to the corresponding group of measuring coils 401 through the control switch S.

[0069] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. An AFCI self-testing system, applied to a string photovoltaic system, characterized in that, include: Controller; The controller is used to generate self-test signals and perform fault analysis on feedback signals; Multiple main coils; Each of the main coils is adapted to correspond to the current connected to the photovoltaic modules in each string; Self-test module; The input terminal of the self-test module is electrically connected to the controller to receive the self-test signal, and the self-test module applies the self-test signal by cooperating with the main coil through the self-test coil at the output terminal. as well as Multiple measurement modules are provided; the output terminals of each measurement module are electrically connected to the controller, and each measurement module cooperates with the main coil through the measurement coil at its input terminal, thereby receiving the feedback signal from the main coil and sending it to the controller. The self-test module includes a self-test signal generation unit and multiple self-test coils; the input terminal of the self-test signal generation unit is electrically connected to the controller, and the output terminal of the self-test signal generation unit is connected to the first terminal of the self-test coil. The self-test signal generation unit is adapted to amplify the self-test signal output by the controller, and then apply the amplified self-test signal to the main coil through the self-test coil.

2. The AFCI self-testing system as described in claim 1, characterized in that, The first end of each self-test coil is connected in parallel to the output end of the self-test signal generation unit via a control switch, and the second end of each self-test coil is connected to a constant positive potential; The control switch is signal-connected to the controller so that the control switch can be closed or opened under the control of the controller, thereby connecting or disconnecting the self-test coil.

3. The AFCI self-testing system as described in claim 1, characterized in that, The self-test coils are connected in series in sequence. The first end of the first self-test coil is connected to the output end of the self-test signal generation unit, and the second end of the last self-test coil is connected to a constant positive potential. The output terminal of the self-test signal generation unit is also provided with a control switch. The control switch is connected to the controller so that the control switch is closed or opened under the control of the controller, thereby connecting or disconnecting the self-test coil from the self-test signal generation unit.

4. The AFCI self-testing system as described in claim 1, characterized in that, The self-test module includes multiple self-test signal generation units and multiple self-test coils; the input terminal of each self-test signal generation unit is electrically connected to the controller, the output terminal of each self-test signal generation unit is connected to the first terminal of the corresponding self-test coil, and the second terminal of each self-test coil is connected to a constant positive potential. The self-test signal generation unit is adapted to amplify the self-test signal output by the controller, and then apply the amplified self-test signal to the corresponding main coil through the self-test coil connected to it.

5. The AFCI self-testing system as described in any one of claims 1-4, characterized in that, The reference potential of the measuring coil is a positive potential or GND.

6. The AFCI self-testing system as described in any one of claims 1-4, characterized in that, The measurement module includes a measurement coil, a filter circuit, and a sampling circuit connected in series.

7. An AFCI self-testing system, applied to a string photovoltaic system, characterized in that, include: Controller; The controller is used to generate self-test signals and perform fault analysis on feedback signals; Multiple main coils; Each of the main coils is adapted to correspond to the current connected to the photovoltaic modules in each string; Self-test module; The input terminal of the self-test module is electrically connected to the controller to receive the self-test signal, and the self-test module applies the self-test signal by cooperating with the main coil through the self-test coil at the output terminal. as well as Multiple measurement modules are provided; the output terminals of each measurement module are electrically connected to the controller, and each measurement module cooperates with the main coil through the measurement coil at its input terminal, thereby receiving the feedback signal from the main coil and sending it to the controller. The total number of channels in the series is N, and the measurement module is set up with N groups, each group including two measurement modules; the self-test module includes a self-test signal generation unit, and the measurement coils corresponding to the input terminals of the two measurement modules in each group are connected to the output terminal of the self-test signal generation unit through a control switch; The control switch is a selection switch, so that the measurement coil of one of the measurement modules in each group is connected to the output terminal of the self-test module through the control switch to serve as the self-test coil. At this time, the other measurement coil in the same group is connected to its corresponding measurement module through the control switch.

8. The AFCI self-test system as described in claim 7, characterized in that, The two measuring coils in each group are defined as the main measuring coil and the auxiliary measuring coil, respectively. Before the string photovoltaic system is powered on normally, the two measuring coils of each group are used as self-test coils in turn for self-testing; during normal operation of the string photovoltaic system after the self-test is completed, the two measuring coils of each group are connected to the corresponding measuring module through the control switch; If the difference between the feedback signals monitored by the two measurement modules in a certain group is greater than a set threshold, the measurement coils corresponding to the two measurement modules in that group will take turns as the self-test coils for self-testing. If the main measuring coil is used as the self-test coil, the secondary measuring coil can collect the self-test signal. However, if the secondary measuring coil is used as the self-test coil, the main measuring coil cannot collect the self-test signal. This indicates that the measuring module corresponding to the main measuring coil has malfunctioned. In this case, AFCI detection is performed only through the measuring module corresponding to the secondary measuring coil, and the controller alarms the main measuring coil for malfunction. If the measurement data of the main measuring coil and the auxiliary measuring coil are consistent when they take turns as the self-test coil, but the overall response is abnormal, it indicates that the two measuring coils have a magnetic core fault.

9. The AFCI self-test system as described in claim 7, characterized in that, The self-test module includes a self-test signal generation unit, and the output terminal of the self-test signal generation unit is connected in parallel with the control switch corresponding to each group of measurement coils. Alternatively, the self-test module includes N self-test signal generation units, and the output terminal of each self-test signal generation unit is connected to the corresponding group of measurement coils through the control switch; wherein, N>1.

10. The AFCI self-testing system as described in any one of claims 7-9, characterized in that, The reference potential of the measuring coil is a positive potential or GND.

11. The AFCI self-testing system as described in any one of claims 7-9, characterized in that, The measurement module includes a measurement coil, a filter circuit, and a sampling circuit connected in series.

Images