Photovoltaic inverter based on electronic switch switching and EL detection method

Abstract

The invention provides a photovoltaic inverter based on electronic switch switching and an EL detection method. The inverter comprises a DC / AC converter, a plurality of MPPT, a bidirectional DC / DC converter and an electronic switch assembly. One end of the DC / AC converter is connected to a power grid, and the other end of the DC / AC converter is connected with each MPPT and the bidirectional DC / DC One end of the bidirectional DC / DC converter is connected with the DC / AC converter, and the other end of the bidirectional DC / DC converter is connected with a photovoltaic module to be detected through an electronic switch module; the electronic switch assembly comprises a plurality of first electronic switches and a plurality of second electronic switches, the plurality of first electronic switches are connected with the MPPT, and the second electronic switches are connected with the bidirectional DC / DC converter. According to the technical scheme provided by the invention, the EL detection of the photovoltaic module is conveniently completed while the normal conversion output of photovoltaic electric energy is realized, an independent EL detection device does not need to be additionally configured, the detection process is simplified, the operation and maintenance cost of the photovoltaic system is reduced, and the detection convenience and the system integration degree are improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic inverter technology, and in particular to a photovoltaic inverter based on electronic switch switching and an EL detection method. Background Technology

[0002] During the operation of a photovoltaic (PV) system, PV modules may develop defects such as microcracks and grid breaks due to manufacturing defects or aging from long-term outdoor use. These defects can affect the power generation efficiency and lifespan of the PV modules. Electroluminescence (EL) testing is an effective method for detecting internal faults in PV modules. However, traditional EL testing requires independent EL testing equipment, which needs to be temporarily connected to the PV system. This is cumbersome and increases the operation and maintenance costs and complexity of the PV system. Therefore, there is an urgent need for a convenient and highly integrated testing solution. Summary of the Invention

[0003] This application provides a photovoltaic inverter based on electronic switch switching and an EL testing method, which at least solves the technical problem that requires temporary connection of the testing equipment to the photovoltaic system, which is cumbersome to operate and increases the operation and maintenance cost and complexity of the photovoltaic system.

[0004] The first aspect of this application proposes a photovoltaic inverter based on electronic switch switching, the photovoltaic inverter comprising: a DC / AC converter, multiple MPPTs, a bidirectional DC / DC converter, and an electronic switch assembly; One end of the DC / AC converter is connected to the power grid, and the other end is connected to each MPPT and bidirectional DC / DC converter. One end of the bidirectional DC / DC converter is connected to the DC / AC converter, and the other end is connected to the photovoltaic module to be tested through an electronic switch assembly. The electronic switch assembly includes a plurality of first electronic switches and a plurality of second electronic switches, wherein the plurality of first electronic switches are connected to the MPPT and the second electronic switches are connected to the bidirectional DC / DC converter.

[0005] Preferably, the DC / AC converter is used for DC power to AC power conversion, converting the photovoltaic DC power transmitted by MPPT into AC power of a preset voltage and frequency, and then transmitting it to the power grid; The DC / AC converter is also used to provide power to the bidirectional DC / DC converter in EL detection mode.

[0006] Furthermore, each of the multiple MPPTs is connected to a string of photovoltaic modules to track the maximum power output point of the photovoltaic modules in real time, ensuring that the photovoltaic modules can output maximum electrical energy under different light and temperature conditions and transmit the electrical energy to the DC / AC converter.

[0007] Furthermore, the bidirectional DC / DC converter is used to assist in adjusting the DC bus voltage between the DC / AC converter and the photovoltaic module when the photovoltaic system is generating electricity normally. The bidirectional DC / DC converter is also used to convert the electrical energy transmitted by the DC / AC converter into the electrical energy required for EL detection during EL detection.

[0008] Furthermore, both the first electronic switch and the second electronic switch employ semiconductor switching devices.

[0009] The second aspect of this application proposes an EL detection method for photovoltaic inverters based on electronic switching, including: Step F1: Obtain the photovoltaic system operation status command. When the EL detection start command is received, the EL detection process is triggered. Step F2: Disconnect the first electronic switch connected to each MPPT, and simultaneously connect the second electronic switch corresponding to the photovoltaic module under test, so that the bidirectional DC / DC converter and the photovoltaic module under test form a closed detection loop; Step F3: Start the bidirectional DC / DC converter to convert the electrical energy transmitted by the DC / AC converter into electrical energy required for EL detection, and deliver it to the photovoltaic module under test through a closed detection loop; Step F4: The photovoltaic module under test generates electroluminescence under electrical excitation. The EL image of the photovoltaic module is acquired by the EL imaging device, and the presence of hidden cracks or grid breakage faults inside the photovoltaic module is determined based on features such as dark spots and cracks in the image. Step F5: After the EL test is completed, control all the connected second electronic switches to disconnect, and then control all the first electronic switches to connect, restoring the power transmission path between the MPPT and the photovoltaic module.

[0010] Preferably, the required parameters are a voltage range of 1-5V and a current range of 10-50mA.

[0011] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects: This application proposes a photovoltaic inverter and EL testing method based on electronic switch switching. The inverter includes a DC / AC converter, multiple MPPTs, a bidirectional DC / DC converter, and an electronic switch assembly. One end of the DC / AC converter is connected to the power grid, and the other end is connected to each MPPT and the bidirectional DC / DC converter. One end of the bidirectional DC / DC converter is connected to the DC / AC converter, and the other end is connected to the photovoltaic module to be tested via the electronic switch assembly. The electronic switch assembly includes multiple first electronic switches and multiple second electronic switches. The multiple first electronic switches are connected to the MPPTs, and the second electronic switches are connected to the bidirectional DC / DC converter. The technical solution proposed in this application can conveniently complete the EL testing of photovoltaic modules while achieving normal photovoltaic power conversion and output, without the need for additional independent EL testing equipment. This simplifies the testing process, reduces the operation and maintenance costs of the photovoltaic system, and improves the convenience of testing and system integration.

[0012] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0013] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart illustrating a photovoltaic inverter based on electronic switch switching according to an embodiment of this application; Figure 2 This is a structural diagram of an EL detection method for a photovoltaic inverter based on electronic switch switching, according to an embodiment of this application. Figure Labels DC / AC converter 1, MPPT 2, bidirectional DC / DC converter 3, electronic switch assembly 4, first electronic switch 4-1, second electronic switch 4-2. Detailed Implementation

[0014] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0015] This application proposes a photovoltaic inverter and EL testing method based on electronic switch switching. The inverter includes a DC / AC converter, multiple MPPTs, a bidirectional DC / DC converter, and an electronic switch assembly. One end of the DC / AC converter is connected to the power grid, and the other end is connected to each MPPT and the bidirectional DC / DC converter. One end of the bidirectional DC / DC converter is connected to the DC / AC converter, and the other end is connected to the photovoltaic module to be tested via the electronic switch assembly. The electronic switch assembly includes multiple first electronic switches and multiple second electronic switches. The multiple first electronic switches are connected to the MPPTs, and the second electronic switches are connected to the bidirectional DC / DC converter. The technical solution proposed in this application can conveniently complete the EL testing of photovoltaic modules while achieving normal photovoltaic power conversion and output, without the need for additional independent EL testing equipment. This simplifies the testing process, reduces the operation and maintenance costs of the photovoltaic system, and improves the convenience of testing and system integration.

[0016] The following description, with reference to the accompanying drawings, illustrates an embodiment of a photovoltaic inverter based on electronic switch switching and an EL detection method.

[0017] Example 1 Figure 1 This is a structural diagram of a photovoltaic inverter based on electronic switching according to an embodiment of this application, as shown below. Figure 1 As shown, the photovoltaic inverter includes: a DC / AC converter 1, multiple maximum power point trackers (MPPTs) 2, a bidirectional DC / DC converter 3, and an electronic switching assembly 4; One end of the DC / AC converter 1 is connected to the power grid, and the other end is connected to each MPPT2 and bidirectional DC / DC converter 3. One end of the bidirectional DC / DC converter 3 is connected to the DC / AC converter 1, and the other end is connected to the photovoltaic module to be tested through the electronic switch assembly 4; The electronic switch assembly 4 includes a plurality of first electronic switches 4-1 and a plurality of second electronic switches 4-2. The plurality of first electronic switches 4-1 are connected to the MPPT2, and the second electronic switches 4-2 are connected to the bidirectional DC / DC converter 3.

[0018] It should be noted that both the first electronic switch 4-1 and the second electronic switch 4-2 are semiconductor switching devices, including but not limited to MOSFET (metal-oxide-semiconductor field-effect transistor) and IGBT (insulated gate bipolar transistor), which have fast switching characteristics and a switching response time of no more than 10ms, enabling rapid switching between power generation and detection modes.

[0019] In this embodiment of the disclosure, the DC / AC converter 1 is used for DC power to AC power conversion, converting the photovoltaic DC power transmitted by MPPT2 into AC power of a preset voltage and frequency, and then transmitting it to the power grid; The DC / AC converter 1 is also used to provide stable power support for the bidirectional DC / DC converter 3 in EL detection mode.

[0020] In this embodiment of the disclosure, the plurality of MPPT2 are respectively connected to a string of photovoltaic modules, which are used to track the maximum power output point of the photovoltaic modules in real time, ensuring that the photovoltaic modules can output maximum electrical energy under different light and temperature conditions, and transmit the electrical energy to the DC / AC converter 1.

[0021] In this embodiment of the disclosure, the bidirectional DC / DC converter 3 is used to assist in adjusting the DC bus voltage between the DC / AC converter 1 and the photovoltaic module when the photovoltaic system is generating electricity normally; The bidirectional DC / DC converter 3 is also used to convert the electrical energy transmitted by the DC / AC converter 1 into the electrical energy required for EL detection during EL detection.

[0022] The photovoltaic modules connected to the bidirectional DC / DC converter 3 do not require connection via electronic switches.

[0023] The photovoltaic inverter proposed in this embodiment has the following advantages: 1. High degree of integration, no additional equipment required: The power supply unit (bidirectional DC / DC converter) and switching unit (electronic switch assembly) required for EL detection are integrated with the traditional photovoltaic inverter, eliminating the need to purchase independent EL detection equipment, reducing the number of photovoltaic system devices and reducing the space occupied by the equipment, which is especially suitable for rooftop photovoltaic systems with limited installation space.

[0024] 2. Convenient testing operation and significantly improved efficiency: Through the automatic switching of electronic switch components, "one-click start testing" is achieved, without the need to disassemble or connect photovoltaic module lines. The testing time for a single module string can be shortened from 30 minutes in the traditional method to less than 5 minutes, greatly improving testing efficiency. At the same time, it supports batch testing of multiple modules. Modules that are not tested during the testing process can generate electricity normally, reducing power generation losses due to downtime.

[0025] 3. Significant cost advantages and reduced maintenance burden: It eliminates the purchase cost of independent EL testing equipment (the unit price of traditional equipment is about RMB 50,000 to 200,000), while reducing labor operation costs; the failure rate of electronic switch components and bidirectional DC / DC converters is low, and the maintenance cost is far lower than that of independent testing equipment, resulting in significant long-term economic benefits in operation and maintenance.

[0026] 4. Strong safety and compatibility: The electronic switch assembly has a built-in overcurrent protection function, which can avoid damage to the assembly due to overcurrent during the detection process; the bidirectional DC / DC converter supports a wide range of power regulation and can be adapted to different types of photovoltaic modules such as monocrystalline silicon, polycrystalline silicon, and thin film, as well as different specifications of module strings such as 12V, 24V, and 48V, making it widely applicable.

[0027] 5. Data-driven management and intelligent operation and maintenance: It can be linked with a remote monitoring platform to realize remote control of EL testing, image uploading and fault alarm, and generate digital test reports, so that operation and maintenance personnel can keep abreast of the status of photovoltaic modules in real time, achieve precise operation and maintenance, and reduce the time for troubleshooting.

[0028] In summary, the photovoltaic inverter based on electronic switch switching proposed in this embodiment integrates the EL detection function with the photovoltaic inverter design. By switching the electronic switch component and regulating the power of the bidirectional DC / DC converter, it realizes flexible switching between normal power generation and EL detection of the photovoltaic system. It eliminates the need for additional independent EL detection equipment, simplifies the detection process, and reduces operation and maintenance costs and system risks.

[0029] Based on the aforementioned photovoltaic inverter, this embodiment also proposes an EL detection method for photovoltaic inverters based on electronic switch switching, such as... Figure 2 As shown, the method includes: Step F1: Obtain the photovoltaic system operation status command. When the EL detection start command is received, the EL detection process is triggered. Step F2: Disconnect the first electronic switch connected to each MPPT, and simultaneously connect the second electronic switch corresponding to the photovoltaic module under test, so that the bidirectional DC / DC converter and the photovoltaic module under test form a closed detection loop; Step F3: Start the bidirectional DC / DC converter to convert the electrical energy transmitted by the DC / AC converter into electrical energy required for EL detection, and deliver it to the photovoltaic module under test through a closed detection loop; Step F4: The photovoltaic module under test generates electroluminescence under electrical excitation. The EL image of the photovoltaic module is acquired by the EL imaging device, and the presence of hidden cracks or grid breakage faults inside the photovoltaic module is determined based on features such as dark spots and cracks in the image. Step F5: After the EL test is completed, control all the connected second electronic switches to disconnect, and then control all the first electronic switches to connect, restoring the power transmission path between the MPPT and the photovoltaic module.

[0030] It should be noted that the required parameters are a voltage range of 1-5V and a current range of 10-50mA.

[0031] The specific implementation steps are as follows: 1. Mode determination and command triggering The main controller of the photovoltaic inverter receives operation commands issued by the user in real time (such as through a remote monitoring platform or local operation panel). When the command is "EL detection start", the main controller first collects the current operating parameters of the photovoltaic system (such as DC bus voltage, grid voltage, and photovoltaic module output current). If the parameters are within the safe range (such as DC bus voltage stable at 300-800V, grid voltage fluctuation ≤±5%), the EL detection process is triggered; if the parameters are abnormal, an alarm signal is issued, and the detection is restarted after the fault is cleared.

[0032] 2. The first electronic switch is disconnected, cutting off the power generation path. The main controller sends a "disconnect" signal to the drive circuits of all first electronic switches. The drive circuits output a drive voltage to turn off the MOSFETs of the first electronic switches, cutting off the power transmission path between the MPPT and the photovoltaic module. At this time, the photovoltaic module stops supplying power to the DC / AC converter, preventing the high voltage and large current of normal power generation from interfering with the low voltage excitation signal detected by the EL. The main controller detects the loop current of the first electronic switches through the current sampling module. After confirming that all first electronic switches are disconnected (loop current ≤ 0.1mA), it proceeds to the next step.

[0033] 3. The second electronic switch is turned on, establishing the detection circuit. The main controller sends an "on" signal to the corresponding second electronic switch drive circuit based on the serial number of the photovoltaic module to be tested (e.g., the user specifies testing the 2nd or 3rd string of photovoltaic modules). The drive circuit then controls the MOSFET of the second electronic switch to turn on, forming a closed detection loop between the output of the bidirectional DC / DC converter and the positive and negative terminals of the photovoltaic module under test. The main controller detects the voltage across the second electronic switch through a voltage sampling module. Once the detection loop is confirmed to be open (voltage ≤ 0.5V), the power supply phase begins.

[0034] 4. Start-up and power regulation of bidirectional DC / DC converter The main controller sends a "detection mode start" command to the bidirectional DC / DC converter. After receiving the command, the converter's control chip starts the internal power conversion program: First, the high-voltage DC power (e.g., 600V) transmitted by the DC / AC converter is stepped down through the Buck topology, and the duty cycle of the IGBT switching transistor is adjusted (e.g., 5%) to output a DC voltage of 1-5V. Then, the current feedback module monitors the detection loop current in real time and adjusts the output current to 10-50mA to ensure that the output power parameters meet the EL detection requirements (different types of photovoltaic modules can be adapted through preset parameters of the main controller, such as setting the voltage of monocrystalline silicon modules to 2V and the current to 30mA, and setting the voltage of polycrystalline silicon modules to 1.8V and the current to 25mA).

[0035] 5. EL Image Acquisition and Fault Diagnosis After the bidirectional DC / DC converter output power stabilizes (parameter fluctuation ≤ ±2%), the main controller sends a "collection start" signal to the external EL imaging device. The imaging device (such as an infrared camera with a resolution of 1280×960) is aimed at the photovoltaic module under test and collects the EL emission image of the module. The image data is transmitted to the main controller or remote monitoring platform through a communication interface (such as Ethernet, RS485). The image is analyzed by an image recognition algorithm: if there are no obvious dark spots or cracks in the image, it is determined that the photovoltaic module has no internal faults; if there are irregular dark spots (which may be hidden cracks) or linear dark lines (which may be broken grids), the fault location and fault type are marked, and a test report is generated.

[0036] 6. Detection circuit disconnection and power generation mode restoration After EL image acquisition is complete, the main controller sends a "stop" command to the bidirectional DC / DC converter, causing the converter to stop power output. Subsequently, it sends a "disconnect" signal to all connected second electronic switches, cutting off the detection circuit. Once the main controller confirms the detection circuit current is zero via the current sampling module, it enters the power generation mode recovery phase. The main controller then sends a "connect" signal to all first electronic switches, controlling them to conduct and restoring the power transmission path between the MPPT and the photovoltaic modules. The MPPT activates its maximum power point tracking function, and the photovoltaic modules resume power delivery to the DC / AC converter. The DC / AC converter converts the DC power into AC power and supplies it to the grid, returning the photovoltaic system to normal power generation mode. The main controller records the EL detection time, detected module number, fault condition, and other information, storing it in local memory or uploading it to the cloud platform for future maintenance and retrieval.

[0037] In summary, the EL testing method for photovoltaic inverters based on electronic switch switching proposed in this embodiment can conveniently complete the EL testing of photovoltaic modules while achieving normal photovoltaic power conversion and output. It does not require additional independent EL testing equipment, simplifies the testing process, reduces the operation and maintenance cost of photovoltaic systems, and improves the convenience of testing and system integration.

[0038] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0039] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0040] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A photovoltaic inverter based on electronic switching, characterized in that, The photovoltaic inverter includes: a DC / AC converter, multiple MPPTs, a bidirectional DC / DC converter, and an electronic switching assembly; One end of the DC / AC converter is connected to the power grid, and the other end is connected to each MPPT and bidirectional DC / DC converter. One end of the bidirectional DC / DC converter is connected to the DC / AC converter, and the other end is connected to the photovoltaic module to be tested through an electronic switch assembly. The electronic switch assembly includes a plurality of first electronic switches and a plurality of second electronic switches, wherein the plurality of first electronic switches are connected to the MPPT and the second electronic switches are connected to the bidirectional DC / DC converter.

2. The photovoltaic inverter as described in claim 1, characterized in that, The DC / AC converter is used for DC power to AC power conversion, converting the photovoltaic DC power transmitted by MPPT into AC power with a preset voltage and frequency, and then transmitting it to the power grid. The DC / AC converter is also used to provide power to the bidirectional DC / DC converter in EL detection mode.

3. The photovoltaic inverter as described in claim 2, characterized in that, Each of the multiple MPPTs is connected to a string of photovoltaic modules, which is used to track the maximum power output point of the photovoltaic modules in real time, ensuring that the photovoltaic modules can output maximum power under different light and temperature conditions, and transmit the power to the DC / AC converter.

4. The photovoltaic inverter as described in claim 3, characterized in that, The bidirectional DC / DC converter is used to assist in adjusting the DC bus voltage between the DC / AC converter and the photovoltaic module when the photovoltaic system is generating electricity normally. The bidirectional DC / DC converter is also used to convert the electrical energy transmitted by the DC / AC converter into the electrical energy required for EL detection during EL detection.

5. The photovoltaic inverter as described in claim 4, characterized in that, Both the first electronic switch and the second electronic switch are semiconductor switching devices.

6. An EL detection method based on any one of the photovoltaic inverters described in claims 1-5, characterized in that, The method includes: Step F1: Obtain the photovoltaic system operation status command. When the EL detection start command is received, the EL detection process is triggered. Step F2: Disconnect the first electronic switch connected to each MPPT, and simultaneously connect the second electronic switch corresponding to the photovoltaic module under test, so that the bidirectional DC / DC converter and the photovoltaic module under test form a closed detection loop; Step F3: Start the bidirectional DC / DC converter to convert the electrical energy transmitted by the DC / AC converter into electrical energy required for EL detection, and deliver it to the photovoltaic module under test through a closed detection loop; Step F4: The photovoltaic module under test generates electroluminescence under electrical excitation. The EL image of the photovoltaic module is acquired by the EL imaging device, and the presence of hidden cracks or grid breakage faults inside the photovoltaic module is determined based on features such as dark spots and cracks in the image. Step F5: After the EL test is completed, control all the connected second electronic switches to disconnect, and then control all the first electronic switches to connect, restoring the power transmission path between the MPPT and the photovoltaic module.

7. The method as described in claim 6, characterized in that, The required parameters are a voltage range of 1-5V and a current range of 10-50mA.

Images