Photovoltaic system, photovoltaic module fault detection method and device

Abstract

The present application provides a photovoltaic system, a photovoltaic module fault detection method and device, and a photovoltaic power generation device. The photovoltaic system includes a photovoltaic module and a photovoltaic power generation device, wherein the photovoltaic power generation device has an input connected to the photovoltaic module and an output connected to the power grid. The photovoltaic power generation device determines the equivalent impedance of the photovoltaic module at at least one measurement frequency based on the output voltage and output current of the photovoltaic module at each of the measurement frequencies, and obtains the impedance deviation of the photovoltaic module at each measurement frequency. If the impedance deviation of the photovoltaic module at each measurement frequency exceeds an impedance deviation threshold, an IV curve scan is performed on the photovoltaic module, and IV curve scan data of the photovoltaic module is obtained. Furthermore, if the deviation between the IV curve scan data of the photovoltaic module and the standard IV curve data exceeds the deviation threshold, a photovoltaic module fault is determined. The present application can effectively reduce fault detection costs and has strong applicability.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a method and device for detecting faults in a photovoltaic system and a photovoltaic module. Background Art

[0002] In recent years, photovoltaic (PV) installed capacity has continued to climb, gradually becoming a mainstream power generation technology. Ensuring the long-term reliable operation of PV systems is a key concern in the industry, making the health status monitoring of PV modules particularly important.

[0003] Currently, fault detection for photovoltaic modules mainly uses the electroluminescence (EL) detection method. This method uses the electroluminescence principle of crystalline silicon to supply power to the photovoltaic module while using a high-resolution near-infrared camera to capture a near-infrared image of the photovoltaic module. The fault can then be determined based on whether the near-infrared image of the photovoltaic module is normal.

[0004] However, these EL detection methods require additional image acquisition equipment and processing systems, such as near-infrared cameras or drones, increasing detection costs. Furthermore, different types of PV panels emit light at different frequencies, requiring different image acquisition equipment, resulting in poor applicability. Summary of the Invention

[0005] The present application provides a photovoltaic system, a photovoltaic module fault detection method, a photovoltaic module fault detection device and a photovoltaic power generation equipment. There is no need to add any detection equipment and systems, nor is there a need to select different detection equipment according to different types of photovoltaic modules. Therefore, it can not only effectively reduce the detection cost, but also effectively cover all photovoltaic systems that require photovoltaic module fault detection, and has strong applicability.

[0006] In a first aspect, the present application provides a photovoltaic system comprising a photovoltaic module and a photovoltaic power generation device, wherein the photovoltaic module is connected to an input terminal of the photovoltaic power generation device, and an output terminal of the photovoltaic power generation device is connected to a power grid. The photovoltaic power generation device determines an equivalent impedance of the photovoltaic module at each of at least one measurement frequency based on an output voltage and an output current of the photovoltaic module at each of the measurement frequencies, and obtains an impedance deviation of the photovoltaic module at each of the measurement frequencies, wherein the impedance deviation of the photovoltaic module at each of the measurement frequencies is the impedance deviation between the equivalent impedance of the photovoltaic module at each of the measurement frequencies and a standard equivalent impedance at each of the measurement frequencies. If an impedance deviation of the photovoltaic module at each of the measurement frequencies exceeds an impedance deviation threshold, an IV curve scan is performed on the photovoltaic module, and IV curve scan data of the photovoltaic module is obtained. Furthermore, if the deviation between the IV curve scan data of the photovoltaic module and the standard IV curve data exceeds the deviation threshold, a photovoltaic module fault is determined. Since the entire fault detection process of photovoltaic modules is completed by the existing photovoltaic power generation equipment in the photovoltaic system, there is no need to add any detection equipment and systems, nor is there a need to select different detection equipment according to different types of photovoltaic modules. Therefore, it can not only effectively reduce the detection cost, but also effectively cover all photovoltaic systems that require photovoltaic module fault detection, and has strong applicability.

[0007] In conjunction with the first aspect, in a first possible implementation, a photovoltaic power generation device generates a first drive signal based on a first reference voltage and an AC measurement signal of at least one measurement frequency, and controls the output voltage of the photovoltaic module based on the first drive signal. The first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid. The photovoltaic power generation device then obtains the output voltage and output current of the photovoltaic module at each of the at least one measurement frequencies under the control of the first drive signal. Furthermore, while supplying power to the grid normally, the output voltage and output current of the photovoltaic module at each of the at least one measurement frequencies can be obtained by superimposing the AC measurement signal of at least one measurement frequency on the output voltage and output current of the photovoltaic module, without affecting the power generation of the photovoltaic system in which the photovoltaic power generation device is located. Furthermore, this implementation obtains the output voltage and output current of the photovoltaic module at each measurement frequency by simultaneously injecting multiple AC measurement signals of different measurement frequencies. Compared to an implementation that injects multiple AC measurement signals of different measurement frequencies in batches, this implementation effectively reduces the workload of the photovoltaic power generation device, improves its operating efficiency, and has strong applicability.

[0008] In conjunction with the first possible implementation of the first aspect, in a second possible implementation, when at least one measurement frequency is less than a frequency threshold, the first reference voltage and the AC measurement signal of at least one measurement frequency are superimposed to obtain a second reference voltage; a first modulation wave is generated based on the second reference voltage and the current output voltage of the photovoltaic module, and a first drive signal is then generated based on the first modulation wave. It will be appreciated that when at least one measurement frequency corresponding to the AC measurement signal is less than the frequency threshold, the closed-loop injection of the AC measurement signal to generate the first drive signal can effectively improve control accuracy.

[0009] In combination with the first possible implementation of the first aspect, in a third possible implementation, when at least one measurement frequency is greater than or equal to the frequency threshold, a second modulation wave is generated based on the first reference voltage and the current output voltage of the photovoltaic module; and the second modulation wave and the AC measurement signal of at least one measurement frequency are superimposed to obtain a third modulation wave, and then the first drive signal is generated based on the third modulation wave. It can be understood that since there is a low-pass filter in the controller inside the photovoltaic power generation device, the method of generating the first drive signal in this embodiment can effectively avoid the high-frequency AC measurement signal (i.e., the AC measurement signal with a frequency greater than or equal to the frequency threshold) being filtered out by the low-pass filter in the controller, thereby ensuring that the complete high-frequency AC measurement signal is retained in the first drive signal.

[0010] In conjunction with the first aspect, in a fourth possible implementation, the photovoltaic power generation device generates a drive signal corresponding to each of the at least one measurement frequency based on a first reference voltage and an AC measurement signal for each of the at least one measurement frequency, and controls the output voltage of the photovoltaic module based on the drive signal corresponding to each of the at least one measurement frequency. The first reference voltage is a reference input voltage of the photovoltaic power generation device when it is supplying power to the grid. Subsequently, the photovoltaic power generation device obtains the output voltage and output current of the photovoltaic module at each of the at least one measurement frequency under the control of the drive signal corresponding to each of the at least one measurement frequency. Since the output voltage and output current of the photovoltaic module at each of the multiple measurement frequencies are calculated by sequentially injecting the AC measurement signal for each measurement frequency, this method is a batch injection (AC measurement signal) method. Compared to a method of centrally injecting multiple AC measurement signals of different measurement frequencies at once, this embodiment does not require any restrictions on the magnitude of each of the multiple measurement frequencies and has strong applicability.

[0011] In combination with the fourth possible implementation of the first aspect, in a fifth possible implementation, when the measurement frequency corresponding to the AC measurement signal is less than the frequency threshold, the photovoltaic power generation device superimposes the first reference voltage and the AC measurement signal of each measurement frequency in at least one measurement frequency to obtain a third reference voltage corresponding to each measurement frequency in at least one measurement frequency; and generates a fourth modulation wave corresponding to each measurement frequency based on the current output voltage of the photovoltaic component and the third reference voltage corresponding to each measurement frequency, and then generates a drive signal corresponding to each measurement frequency based on the fourth modulation wave corresponding to each measurement frequency. When the measurement frequency corresponding to the AC measurement signal is less than the frequency threshold, since the drive signal corresponding to each measurement frequency is generated by injecting the AC measurement signal in a closed loop, the control accuracy can be effectively improved.

[0012] In combination with the fourth possible implementation of the first aspect, in a sixth possible implementation, when the measurement frequency corresponding to the AC measurement signal is greater than or equal to the frequency threshold, the photovoltaic power generation device generates a fifth modulation wave based on the first reference voltage and the current output voltage of the photovoltaic module; and the fifth modulation wave is superimposed with the AC measurement signal of each measurement frequency in at least one measurement frequency to obtain a sixth modulation wave corresponding to each measurement frequency, and then a drive signal corresponding to each measurement frequency is generated based on the sixth modulation wave corresponding to each measurement frequency. Since there is a low-pass filter in the controller inside the photovoltaic power generation device, the method of generating the drive signal corresponding to each high-frequency measurement frequency (i.e., a measurement frequency greater than or equal to the frequency threshold) in this embodiment can effectively avoid the high-frequency AC measurement signal (i.e., an AC measurement signal with a measurement frequency greater than or equal to the frequency threshold) being filtered out by the low-pass filter in the controller, thereby ensuring that the complete high-frequency AC measurement signal is retained in the drive signal corresponding to each high-frequency measurement frequency.

[0013] In combination with the first to sixth possible implementations of the first aspect, in a seventh possible implementation, the photovoltaic power generation device determines the current operating state of the photovoltaic power generation device, and determines a first reference voltage based on the current operating state of the photovoltaic power generation device, where the first reference voltage is a reference input voltage when the photovoltaic power generation device is in a power-limited operating state, or a reference input voltage when the photovoltaic power generation device is in a non-power-limited operating state. It is understandable that the first reference voltage changes with the current operating state of the photovoltaic power generation device (i.e., the power-limited operating state or the non-power-limited operating state), and thus can effectively meet the needs of the photovoltaic power generation device to supply power to the power grid in different operating states, with high flexibility.

[0014] In combination with the first to seventh possible implementations, in an eighth possible implementation, the photovoltaic power generation device performs an IV curve scan on the photovoltaic module if, among the impedance deviations of the photovoltaic module at each measurement frequency, there are m impedance deviations greater than an impedance deviation threshold, and m is greater than a quantity threshold, where the quantity threshold is a positive integer. It will be understood that if the photovoltaic power generation device has multiple impedance deviations greater than the impedance deviation threshold among the multiple impedance deviations, the photovoltaic module is determined to be at risk of failure, and an IV curve scan is then performed on the photovoltaic module at risk of failure. This effectively reduces the number of IV curve scans, thereby reducing power fluctuations during detection and thereby increasing the power generation of the photovoltaic system.

[0015] In combination with the first to eighth possible implementations, in a ninth possible implementation, the photovoltaic power generation device compares the descending phase scan data of the photovoltaic module within the descending phase scan cycle with the ascending phase scan data of the photovoltaic module within the ascending phase scan cycle, and outputs the IV curve scan data of the photovoltaic module based on the comparison result, wherein the descending phase scan cycle and the ascending phase scan cycle constitute the IV curve scan cycle of the photovoltaic module. It is understandable that by comparing the descending phase scan data with the ascending phase scan data, the photovoltaic power generation device obtains the IV curve scan data of the photovoltaic string, which can effectively solve the problem of low accuracy of the IV curve scan results of the photovoltaic module caused by changes in illumination during the IV curve scanning process, thereby improving the accuracy of the IV curve scan results of the photovoltaic module.

[0016] In combination with the first to ninth possible implementations, in a tenth possible implementation, the photovoltaic power generation equipment is a DC / DC converter, the power grid is a DC power grid, the photovoltaic system also includes a DC bus, and the output end of the DC / DC converter is connected to the DC power grid through the DC bus.

[0017] In combination with the first aspect to the ninth possible implementation manner, in the eleventh possible implementation manner, the photovoltaic system also includes an inverter and a DC bus, the photovoltaic power generation equipment is a DC / DC converter, the power grid is an AC power grid, the output end of the DC / DC converter and the input end of the inverter are connected in parallel to the DC bus, and the output end of the inverter is connected to the AC power grid.

[0018] In combination with the first aspect to the ninth possible implementation manner, in a twelfth possible implementation manner, the photovoltaic power generation equipment is an inverter, and the power grid is an AC power grid.

[0019] In a second aspect, the present application provides a fault detection method for a photovoltaic module, wherein an input end of a photovoltaic power generation device is connected to the photovoltaic module, and an output end of the photovoltaic power generation device is connected to a power grid. The method comprises: determining an equivalent impedance of the photovoltaic module at each measurement frequency based on an output voltage and an output current of the photovoltaic module at each measurement frequency, and obtaining an impedance deviation of the photovoltaic module at each measurement frequency, wherein the impedance deviation of the photovoltaic module at each measurement frequency is an impedance deviation between the equivalent impedance of the photovoltaic module at each measurement frequency and a standard equivalent impedance at each measurement frequency; if an impedance deviation of the photovoltaic module at each measurement frequency is greater than an impedance deviation threshold, performing an IV curve scan on the photovoltaic module and obtaining IV curve scan data of the photovoltaic module; and determining that the photovoltaic module is faulty if a deviation between the IV curve scan data of the photovoltaic module and the standard IV curve data is greater than the deviation threshold.

[0020] In conjunction with the second aspect, in a first possible implementation, a first drive signal is generated based on a first reference voltage and an AC measurement signal having at least one measurement frequency, and the output voltage of the photovoltaic module is controlled based on the first drive signal. The first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid. The photovoltaic power generation device then obtains the output voltage and output current of the photovoltaic module at each of the at least one measurement frequency under control of the first drive signal.

[0021] In combination with the first possible implementation of the second aspect, in a second possible implementation, when at least one measurement frequency is less than the frequency threshold, the first reference voltage and the AC measurement signal of at least one measurement frequency are superimposed to obtain a second reference voltage; and a first modulation wave is generated based on the second reference voltage and the current output voltage of the photovoltaic component, and then a first drive signal is generated based on the first modulation wave.

[0022] In combination with the first possible implementation of the second aspect, in a third possible implementation, when at least one measurement frequency is greater than or equal to the frequency threshold, a second modulation wave is generated based on the first reference voltage and the current output voltage of the photovoltaic component; and the second modulation wave and the AC measurement signal of at least one measurement frequency are superimposed to obtain a third modulation wave, and then a first drive signal is generated based on the third modulation wave.

[0023] In conjunction with the second aspect, in a fourth possible implementation, a drive signal corresponding to each of the at least one measurement frequency is generated based on a first reference voltage and an AC measurement signal corresponding to each of the at least one measurement frequency, and the output voltage of the photovoltaic module is controlled based on the drive signal corresponding to each of the at least one measurement frequency. The first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid. Subsequently, the output voltage and output current of the photovoltaic module at each of the at least one measurement frequency are obtained under the control of the drive signal corresponding to each of the at least one measurement frequency.

[0024] In combination with the fourth possible implementation of the second aspect, in a fifth possible implementation, when the measurement frequency corresponding to the AC measurement signal is less than the frequency threshold, the first reference voltage and the AC measurement signal of each measurement frequency in at least one measurement frequency are superimposed to obtain a third reference voltage corresponding to each measurement frequency in at least one measurement frequency; and a fourth modulation wave corresponding to each measurement frequency is generated based on the current output voltage of the photovoltaic component and the third reference voltage corresponding to each measurement frequency, and then a drive signal corresponding to each measurement frequency is generated based on the fourth modulation wave corresponding to each measurement frequency.

[0025] In combination with the fourth possible implementation of the second aspect, in a sixth possible implementation, when the measurement frequency corresponding to the AC measurement signal is greater than or equal to the frequency threshold, a fifth modulation wave is generated based on the first reference voltage and the current output voltage of the photovoltaic component; and the fifth modulation wave and the AC measurement signal of each measurement frequency in at least one measurement frequency are superimposed to obtain a sixth modulation wave corresponding to each measurement frequency, and then a driving signal corresponding to each measurement frequency is generated based on the sixth modulation wave corresponding to each measurement frequency.

[0026] In combination with the first to sixth possible implementations of the second aspect, in the seventh possible implementation, the current working state of the photovoltaic power generation equipment is determined, and a first reference voltage is determined based on the current working state of the photovoltaic power generation equipment. The first reference voltage is the reference input voltage when the photovoltaic power generation equipment is in a power-limited working state, or the reference input voltage when the photovoltaic power generation equipment is in a non-power-limited working state.

[0027] In combination with the second to seventh possible implementations, in an eighth possible implementation, among the impedance deviations of the photovoltaic component at each measurement frequency, there are m impedance deviations greater than the impedance deviation threshold and m is greater than the quantity threshold, then the photovoltaic component is scanned by an IV curve, and the quantity threshold is a positive integer.

[0028] In combination with the second to eighth possible implementations, in a ninth possible implementation, the descending phase scanning data of the photovoltaic module in the descending phase scanning period is compared with the ascending phase scanning data of the photovoltaic module in the ascending phase scanning period, and the IV curve scanning data of the photovoltaic module is output based on the comparison result, wherein the descending phase scanning period and the ascending phase scanning period constitute the IV curve scanning period of the photovoltaic module.

[0029] In a third aspect, the present application provides a photovoltaic module fault detection device, which is located in a photovoltaic power generation device. The device may be a controller in the photovoltaic power generation device, and the device includes:

[0030] an equivalent impedance determination module, configured to determine an equivalent impedance of the photovoltaic assembly at at least one measurement frequency based on an output voltage and an output current of the photovoltaic assembly at at least one measurement frequency;

[0031] An impedance deviation acquisition module is used to obtain the impedance deviation of the photovoltaic module at each measurement frequency, wherein the impedance deviation of the photovoltaic module at each measurement frequency is the impedance deviation between the equivalent impedance of the photovoltaic module at each measurement frequency and the standard equivalent impedance at each measurement frequency;

[0032] An IV curve acquisition module is used to perform an IV curve scan on the photovoltaic module and obtain IV curve scan data of the photovoltaic module when the impedance deviation of the photovoltaic module at each measurement frequency is greater than an impedance deviation threshold.

[0033] The fault determination module is used to determine that the photovoltaic component is faulty when a deviation between the IV curve scan data of the photovoltaic component and the IV curve standard data is greater than a deviation threshold.

[0034] In conjunction with the third aspect, in a first possible implementation manner, the device further includes:

[0035] a control module, configured to generate a first drive signal based on a first reference voltage and an AC measurement signal of at least one measurement frequency, and to control the output voltage of the photovoltaic assembly based on the first drive signal, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid;

[0036] an acquisition module, configured to acquire an output voltage and an output current of the photovoltaic assembly at at least one measurement frequency under the control of a first driving signal;

[0037] In combination with the first possible implementation of the third aspect, in a second possible implementation, the control module includes:

[0038] a first superposition unit, configured to superpose the first reference voltage and an AC measurement signal of at least one measurement frequency to obtain a second reference voltage;

[0039] a first control unit, configured to generate a first modulation wave according to a second reference voltage and a current output voltage of the photovoltaic module;

[0040] The first modulation unit is configured to generate a first driving signal according to a first modulation wave.

[0041] In combination with the first possible implementation manner of the third aspect, in a third possible implementation manner, the control module includes:

[0042] a first control unit, configured to generate a second modulation wave according to the first reference voltage and the current output voltage of the photovoltaic module;

[0043] a second superposition unit, configured to superpose the second modulated wave and an AC measurement signal of at least one measurement frequency to obtain a third modulated wave;

[0044] The first modulation unit is configured to generate a first driving signal according to the third modulation wave.

[0045] In combination with the third aspect, in a fourth possible implementation, the device further includes:

[0046] a control module, configured to generate a drive signal corresponding to each of the at least one measurement frequency based on a first reference voltage and an AC measurement signal of each of the at least one measurement frequency, and to control an output voltage of the photovoltaic assembly based on the drive signal corresponding to each of the at least one measurement frequency, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to a grid;

[0047] The acquisition module is used to acquire the output voltage and output current of the photovoltaic component at each of the at least one measurement frequency under the control of the driving signal corresponding to each of the at least one measurement frequency.

[0048] In combination with the fourth possible implementation manner of the third aspect, in a fifth possible implementation manner, the control module includes:

[0049] a first superposition unit, configured to superpose the first reference voltage and the AC measurement signal of each frequency in the at least one measurement frequency to obtain a third reference voltage corresponding to each measurement frequency in the at least one measurement frequency;

[0050] A first control unit is configured to generate a fourth modulation wave corresponding to each measurement frequency according to a current output voltage of the photovoltaic module and a third reference voltage corresponding to each measurement frequency;

[0051] The first modulation unit is configured to generate a driving signal corresponding to each measurement frequency according to a fourth modulation wave corresponding to each measurement frequency.

[0052] In combination with the fourth possible implementation manner of the third aspect, in a sixth possible implementation manner, the control module includes:

[0053] a first control unit, configured to generate a fifth modulation wave according to the first reference voltage and a current output voltage of the photovoltaic assembly;

[0054] a second superposition unit, configured to superpose the fifth modulation wave and the AC measurement signal of each measurement frequency of at least one measurement frequency to obtain a sixth modulation wave corresponding to each measurement frequency;

[0055] The first modulation unit is configured to generate a driving signal corresponding to each measurement frequency according to a sixth modulation wave corresponding to each measurement frequency.

[0056] In combination with any one of the first possible implementation manner of the third aspect to the sixth possible implementation manner of the third aspect, in a seventh possible implementation manner, the device further includes:

[0057] The first determination module is used to determine the current working state of the photovoltaic power generation equipment and determine a first reference voltage based on the current working state of the photovoltaic power generation equipment. The first reference voltage is a reference input voltage when the photovoltaic power generation equipment is in a power-limited working state, or a reference input voltage when the photovoltaic power generation equipment is in a non-power-limited working state.

[0058] In combination with any one of the third aspect to the seventh possible implementation manner of the third aspect, in an eighth possible implementation manner, the IV curve acquisition module is used to: in the impedance deviation of the photovoltaic component at at least one measurement frequency, there are m impedance deviations greater than the impedance deviation threshold and m is greater than the quantity threshold, then the IV curve scan is performed on the photovoltaic component, and the quantity threshold is a positive integer.

[0059] In combination with any one of the third aspect to the eighth possible implementation manner of the third aspect, in a ninth possible implementation manner, the IV curve acquisition module is used to: compare the descending phase scanning data of the photovoltaic component in the descending phase scanning period with the ascending phase scanning data of the photovoltaic component in the ascending phase scanning period, and output the IV curve scanning data of the photovoltaic component based on the comparison result, wherein the descending phase scanning period and the ascending phase scanning period constitute the IV curve scanning period of the photovoltaic component.

[0060] In a fourth aspect, the present application provides a photovoltaic power generation device, wherein the input end of the photovoltaic power generation device is connected to a photovoltaic module and the output end is connected to a power grid, and the photovoltaic power generation device includes a controller and a power supply circuit. The input end of the power supply circuit is connected to the input end of the photovoltaic power generation device, and the output end of the power supply circuit is connected to the output end of the photovoltaic power generation device, and the power supply circuit is used to convert the input end voltage of the photovoltaic power generation device into the output end voltage of the photovoltaic power generation device; the controller determines the equivalent impedance of the photovoltaic module at each measurement frequency based on the output voltage and output current of the photovoltaic module at each measurement frequency in at least one measurement frequency; obtains the impedance deviation of the photovoltaic module at each measurement frequency, wherein the impedance deviation of the photovoltaic module at each measurement frequency is the impedance deviation between the equivalent impedance of the photovoltaic module at each measurement frequency and the standard equivalent impedance at each measurement frequency; when there is an impedance deviation greater than an impedance deviation threshold in the impedance deviation of the photovoltaic module at each measurement frequency, performs an IV curve scan on the photovoltaic module and obtains IV curve scan data of the photovoltaic module; and determines that the photovoltaic module is faulty when the deviation between the IV curve scan data of the photovoltaic module and the IV curve standard data is greater than the deviation threshold.

[0061] In conjunction with the fourth aspect, in a first possible implementation, a controller generates a first drive signal based on a first reference voltage and an AC measurement signal of at least one measurement frequency, and controls the output voltage of the photovoltaic assembly based on the first drive signal. The first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid. The controller then obtains the output voltage and output current of the photovoltaic assembly at each of the at least one measurement frequency under control of the first drive signal.

[0062] In combination with the first possible implementation of the fourth aspect, in a second possible implementation, when at least one measurement frequency is less than the frequency threshold, the controller superimposes the first reference voltage and the AC measurement signal of at least one measurement frequency to obtain a second reference voltage; and generates a first modulation wave based on the second reference voltage and the current output voltage of the photovoltaic component, and then generates a first drive signal based on the first modulation wave.

[0063] In combination with the first possible implementation of the fourth aspect, in a third possible implementation, when at least one measurement frequency is greater than or equal to the frequency threshold, the controller generates a second modulation wave based on the first reference voltage and the current output voltage of the photovoltaic component; and superimposes the second modulation wave and the AC measurement signal of at least one measurement frequency to obtain a third modulation wave, and then generates a first drive signal based on the third modulation wave.

[0064] In conjunction with the fourth aspect, in a fourth possible implementation, the controller generates a drive signal corresponding to each of the at least one measurement frequency based on a first reference voltage and an AC measurement signal corresponding to each of the at least one measurement frequency, and controls the output voltage of the photovoltaic module based on the drive signal corresponding to each of the at least one measurement frequency. The first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid. The controller then obtains the output voltage and output current of the photovoltaic module at each of the at least one measurement frequency under control of the drive signal corresponding to each of the at least one measurement frequency.

[0065] In combination with the fourth possible implementation of the fourth aspect, in a fifth possible implementation, when the measurement frequency corresponding to the AC measurement signal is less than the frequency threshold, the controller superimposes the first reference voltage and the AC measurement signal of each measurement frequency in at least one measurement frequency to obtain a third reference voltage corresponding to each measurement frequency in at least one measurement frequency; and generates a fourth modulation wave corresponding to each measurement frequency based on the current output voltage of the photovoltaic component and the third reference voltage corresponding to each measurement frequency, and then generates a driving signal corresponding to each measurement frequency based on the fourth modulation wave corresponding to each measurement frequency.

[0066] In combination with the fourth possible implementation of the fourth aspect, in a sixth possible implementation, when the measurement frequency corresponding to the AC measurement signal is greater than or equal to the frequency threshold, the controller generates a fifth modulation wave based on the first reference voltage and the current output voltage of the photovoltaic component; and superimposes the fifth modulation wave and the AC measurement signal of each measurement frequency in at least one measurement frequency to obtain a sixth modulation wave corresponding to each measurement frequency, and then generates a driving signal corresponding to each measurement frequency based on the sixth modulation wave corresponding to each measurement frequency.

[0067] In combination with the first possible implementation to the sixth possible implementation of the fourth aspect, in the seventh possible implementation, the controller determines the current working state of the photovoltaic power generation equipment, and determines a first reference voltage based on the current working state of the photovoltaic power generation equipment. The first reference voltage is the reference input voltage when the photovoltaic power generation equipment is in a power-limited working state, or the reference input voltage when the photovoltaic power generation equipment is in a non-power-limited working state.

[0068] In combination with the fourth to seventh possible implementations, in an eighth possible implementation, if there are m impedance deviations greater than the impedance deviation threshold in the impedance deviation of the photovoltaic component at each measurement frequency and m is greater than the quantity threshold, the controller performs an IV curve scan on the photovoltaic component, and the quantity threshold is a positive integer.

[0069] In combination with the first to eighth possible implementations, in a ninth possible implementation, the controller compares the descending phase scanning data of the photovoltaic module in the descending phase scanning cycle with the ascending phase scanning data of the photovoltaic module in the ascending phase scanning cycle, and outputs the IV curve scanning data of the photovoltaic module based on the comparison result, wherein the descending phase scanning cycle and the ascending phase scanning cycle constitute the IV curve scanning cycle of the photovoltaic module.

[0070] It should be understood that the implementation and beneficial effects of the above-mentioned aspects of the present application can be referenced to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 This is a schematic diagram of the application scenario of the photovoltaic system provided by this application;

[0072] Figure 2 This is a schematic structural diagram of a photovoltaic system provided by this application;

[0073] Figure 3 This is a schematic structural diagram of a photovoltaic module fault detection device provided by the present application;

[0074] Figure 4 This is another structural schematic diagram of the photovoltaic module fault detection device provided by the present application;

[0075] Figure 5 is another structural schematic diagram of the photovoltaic system provided by this application;

[0076] Figure 6 This is another structural schematic diagram of the photovoltaic system provided by this application;

[0077] Figure 7 This is a waveform diagram of the output voltage and output current of a photovoltaic module during the fault detection process provided by the present application;

[0078] Figure 8 is another waveform diagram of the output voltage and output current of the photovoltaic module during the fault detection process provided by the present application;

[0079] Figure 9 is another structural schematic diagram of the photovoltaic system provided by this application;

[0080] Figure 10 is another structural schematic diagram of the photovoltaic system provided by this application;

[0081] Figure 11 This is another structural diagram of the photovoltaic system provided by this application;

[0082] Figure 12 This is another structural diagram of the photovoltaic system provided by this application;

[0083] Figure 13 It is a flow chart of the photovoltaic module fault detection method provided in this application. DETAILED DESCRIPTION

[0084] The photovoltaic system provided in this application is applicable to various application scenarios, such as photovoltaic power supply scenarios and hybrid power supply scenarios. In photovoltaic power supply scenarios, the power supply is photovoltaic modules; in hybrid power supply scenarios, the power supply includes photovoltaic modules and energy storage battery strings. The following uses the photovoltaic power supply scenario as an example for explanation.

[0085] See also Figure 1 , Figure 1 The photovoltaic system provided by this application includes a photovoltaic module and a photovoltaic power generation device. The input end of the photovoltaic power generation device is connected to the photovoltaic module, and the output end is connected to the power grid. In the photovoltaic power supply scenario, the photovoltaic power generation device can be Figure 1 The DC / DC converter shown in the figure can be Figure 1The AC grid shown. The photovoltaic system also includes an inverter, wherein the output of the DC / DC converter is connected to the input of the inverter, and the output of the inverter is connected to the AC grid or household appliances. Optionally, the number of photovoltaic modules connected to the input of the DC / DC converter can be multiple, and multiple photovoltaic modules can be connected in series and / or in parallel to the DC / DC converter. After the photovoltaic system begins operation, the DC / DC converter can convert the DC power generated by the photovoltaic modules connected to its input into DC power with a preset voltage and output the DC power to the inverter. The inverter inverts the DC power output by the DC / DC converter into AC power, thereby providing power to various types of electrical devices such as the AC grid or AC loads (such as household appliances). When the photovoltaic system needs to detect a fault in the photovoltaic module during the process of supplying power to the electrical device, the DC / DC converter determines the equivalent impedance of the photovoltaic module at the first frequency based on the output voltage and output current of the photovoltaic module at the first frequency. When the impedance deviation between the equivalent impedance of the photovoltaic component at the first frequency and the standard equivalent impedance at the first frequency is greater than the impedance deviation threshold, the IV curve (i.e., current-voltage curve) of the photovoltaic component is scanned, and the IV curve scan data of the photovoltaic component is obtained. Then, when the deviation between the IV curve scan data of the photovoltaic component and the IV curve standard data is greater than the deviation threshold, the photovoltaic component fault is determined. Compared with the above-mentioned EL detection method, the fault detection method of the photovoltaic component provided in the present application can be implemented by relying solely on the DC / DC converter connected to the photovoltaic component in the photovoltaic system, without adding any equipment and systems, and without selecting different detection equipment according to different types of photovoltaic components. Therefore, it can not only effectively reduce the detection cost, but also effectively cover various types of photovoltaic systems, such as large photovoltaic systems (i.e., large photovoltaic power stations) and small photovoltaic systems (i.e., residential photovoltaic systems), and has strong applicability. The above is only an example of the application scenario of the photovoltaic system provided in the present application, not an exhaustive list, and the present application does not limit the application scenario.

[0086] The following combination Figures 2 to 12 The working principles of the photovoltaic system and photovoltaic power generation equipment provided in this application are illustrated.

[0087] See also Figure 2 , Figure 2 This is a schematic diagram of the structure of the photovoltaic system provided by this application. Figure 2As shown, the photovoltaic system 1 includes a photovoltaic module 10 and a photovoltaic power generation device 11. The input end of the photovoltaic power generation device 11 is connected to the photovoltaic module 10, and the output end is connected to the power grid. The photovoltaic power generation device 11 includes a power supply circuit 111 and a controller 112. The input end of the power supply circuit 111 is connected to the input end of the photovoltaic power generation device 11, and the output end of the power supply circuit 111 is connected to the output end of the photovoltaic power generation device 11. The power supply circuit 111 is used to convert the input end voltage of the photovoltaic power generation device 11 to the output end voltage of the photovoltaic power generation device 11. Exemplarily, when the photovoltaic power generation device 11 needs to supply power to the power grid, the photovoltaic power generation device 11 controls the power supply circuit 111 to convert the output voltage of the photovoltaic module 10 into the output voltage of the photovoltaic power generation device 11 when supplying power to the power grid.

[0088] In an optional embodiment, when the photovoltaic power generation device 11 needs to perform fault detection on the photovoltaic module 10, the controller 112 determines the equivalent impedance of the photovoltaic module 10 at each measurement frequency based on the output voltage and output current of the photovoltaic module 10 at each measurement frequency, and calculates the impedance deviation between the equivalent impedance of the photovoltaic module 10 at each measurement frequency and the standard equivalent impedance at each measurement frequency to obtain the impedance deviation of the photovoltaic module 10 at each measurement frequency. If the impedance deviation of the photovoltaic module 10 at each measurement frequency is greater than an impedance deviation threshold, the controller 112 performs an IV curve scan on the photovoltaic module 10 and obtains IV curve scan data of the photovoltaic module 10. If the deviation between the IV curve scan data of the photovoltaic module and the standard IV curve data is greater than the deviation threshold, the controller 112 determines that the photovoltaic module 10 is faulty.

[0089] The controller 112 provided in this application may be a fault detection device for the photovoltaic module 10. For ease of description, see Figure 3 , Figure 3 This is a schematic diagram of the structure of the photovoltaic module fault detection device provided by this application. Figure 3 As shown, the fault detection device includes an equivalent impedance determination module 1121 , an impedance deviation acquisition module 1122 , an IV curve acquisition module 1123 and a fault determination module 1124 .

[0090] Specifically, when it is necessary to perform fault detection on the photovoltaic assembly 10, the equivalent impedance determination module 1121 determines the equivalent impedance of the photovoltaic assembly 10 based on the n measurement frequencies (ie, ω1, ..., ω n ) in each measurement frequency ω j The output voltage v(ω j ) and output current i(ω j ), calculate the photovoltaic module 10 at each measurement frequency ω j The equivalent impedance Z(ω j )=v(ωj ) / i(ω j ), and the photovoltaic module 10 is set at each measurement frequency ω j The equivalent impedance Z(ω j ) is output to the impedance deviation acquisition module 1122. Wherein, 1≤j≤n, n is a positive integer. The impedance deviation acquisition module 1122 calculates the impedance deviation of the photovoltaic module 10 at each measurement frequency ω j The equivalent impedance Z(ω j ) and at each measurement frequency ω j The standard equivalent impedance Z REF (ω j ), and the impedance deviation between the photovoltaic module 10 and the measured frequency ω is obtained. j Impedance deviation ΔZ(ω j )=|Z(ω j )-Z REF (ω j )|, and each measurement frequency ω j Impedance deviation ΔZ(ω j ) is output to the IV curve acquisition module 1123. The IV curve acquisition module 1123 determines each measurement frequency ω j Impedance deviation ΔZ(ω j ), that is, ΔZ(ω1),..., ΔZ(ω n ), whether there is an impedance deviation greater than the impedance deviation threshold Z among the n impedance deviations TH If an impedance deviation exists, the IV curve acquisition module 1123 generates an IV curve scanning drive signal and outputs the IV curve scanning drive signal to the power supply circuit 111, so that the power supply circuit 111 controls the output voltage of the photovoltaic module 10 under the control of the IV curve scanning drive signal, thereby completing the IV curve scanning of the photovoltaic module 10 and outputting the acquired IV curve scanning data of the photovoltaic module 10 to the fault determination module 1124. The fault determination module 1124 compares the IV curve scanning data of the photovoltaic module 10 with the IV curve standard data to obtain the detection result of the photovoltaic module 10. Specifically, if the deviation between the IV curve scanning data of the photovoltaic module 10 and the IV curve standard data is greater than the deviation threshold, the fault determination module 1124 determines that the photovoltaic module 10 is faulty; otherwise, the photovoltaic module 10 is determined to be healthy.

[0091] Further, see Figure 4 , Figure 4 This is another structural diagram of the photovoltaic module fault detection device provided by this application. Figure 4As shown, the photovoltaic module fault detection device further includes a control module 1125, an acquisition module 1126, and a first determination module 1127. The control module 1125 includes a first superposition unit 11251, a first control unit 11252, a first modulation unit 11253, a second superposition unit 11254, and a measurement signal generation and position selection unit 11255. The acquisition module 1126 includes a sampling unit 11261 and a first filtering unit 11262. The IV curve acquisition module 1123 includes a judgment unit 11231, a second control unit 11232, a second modulation unit 11233, a second filtering unit 11264, and an IV curve data generation unit 11265. It should be noted that the second control unit 11232 and the first control unit 11252 can be the same control unit or two different control units; and the second modulation unit 11233 and the first modulation unit 11253 can be the same modulation unit or two different modulation units, and this application does not impose any restrictions on this.

[0092] In an optional embodiment, the control module 1125 generates a voltage according to the first reference voltage V ref1 and n measurement frequencies (i.e. ω1, ..., ω n ) generates a first driving signal based on the AC measurement signal, and controls the output voltage of the photovoltaic assembly 10 according to the first driving signal, wherein the first reference voltage V ref1 is the reference input voltage of the photovoltaic power generation device 11 in the state of supplying power to the grid. Then, the acquisition module 1126 acquires the measurement frequency ω of each of the n measurement frequencies of the photovoltaic component 10 under the control of the first drive signal. j The output voltage v(ω j ) and output current i(ω j ).

[0093] Specifically, when the photovoltaic power generation device 11 needs to perform fault detection on the photovoltaic module 10, the sampling unit 11261 collects the port voltage and port current of the photovoltaic module 10 in real time or at a preset frequency, that is, the voltage and current of the port connecting the photovoltaic module 10 and the power supply circuit 111, obtains the current output voltage v(t1) and current output current i(t1) of the photovoltaic module 10, and inputs the collected v(t1) and i(t1) into the first determination module 1127. The first determination module 1127 determines the current working state of the photovoltaic power generation device 11 (that is, the non-power limited working state or the power limited working state), and determines the first reference voltage V based on the current working state of the photovoltaic power generation device 11, the current output voltage v(t1) and the current output current i(t1) of the photovoltaic module 10. ref1 and the first reference voltage V ref1Output to the first superposition unit 11251. Wherein, when the photovoltaic power generation device 11 is in the non-power-limited working state, the photovoltaic power generation device 11 performs maximum power point tracking (MPPT) to maximize the output power, and when the photovoltaic power generation device 11 is in the power-limited working state, the photovoltaic power generation device 11 actively limits the output power. The first reference voltage V ref1 is the reference input voltage of the photovoltaic power generation device 11 when supplying power to the grid. In other words, the average output voltage of the photovoltaic component 10 can be maintained equal to V ref1 In this way, the normal power generation operation of the photovoltaic system 1 is maintained.

[0094] At the same time, the measurement signal generation and position selection unit 11255 generates a measurement signal based on the n measurement frequencies and the measurement frequency ω in the n measurement frequencies. j The corresponding AC measurement signal amplitude A k Generate AC measurement signals of n measurement frequencies, and select the superposition unit of the AC measurement signals of n measurement frequencies (i.e., the first superposition unit 11251 or the second superposition unit 11254) according to the n measurement frequencies, and then output the AC measurement signals of n measurement frequencies to the first superposition unit 11251 or the second superposition unit 11254.

[0095] Specifically, when n measured frequencies are all less than the frequency threshold ω b In the case of n measurement frequencies, the measurement signal generation and position selection unit 11255 determines the superposition unit of the AC measurement signals of n measurement frequencies as the first superposition unit 11251, and outputs the AC measurement signals of n measurement frequencies to the first superposition unit 11251. This method is called a closed-loop injection (AC measurement signal) method; when the n measurement frequencies are all greater than or equal to the frequency threshold ω b In the case of , the measurement signal generation and position selection unit 11255 determines the superposition unit of the AC measurement signals of n measurement frequencies as the second superposition unit 11254, and outputs the AC measurement signals of n measurement frequencies to the second superposition unit 11254. This method is called open-loop injection (AC measurement signal) method. b The typical selection range is 1 / 10 to 1 / 5 of the switching frequency of the power supply circuit 111, and the measurement frequency corresponding to the injected AC measurement signal is not higher than 1 / 2 of the switching frequency of the power supply circuit 111. For example, the switching frequency of the power supply circuit 111 is 40kHz, and the frequency threshold ω b It is 1 / 10 of the switching frequency of the power supply circuit 111, that is, 4 kHz.

[0096] It should be noted that during closed-loop injection, the AC measurement signal amplitude is a non-increasing function of the measurement frequency. For example, when injecting AC measurement signals of a first measurement frequency ω1 and a second measurement frequency ω2 using closed-loop injection, if ω2 is greater than ω1, then A2 is not greater than A1, where A1 is the AC measurement signal amplitude corresponding to the first measurement frequency ω1, and A2 is the AC measurement signal amplitude corresponding to the second measurement frequency ω2. This prevents the detection current from further increasing as the detection frequency increases, thereby endangering the safety of photovoltaic system 1, thereby improving the safety of photovoltaic system 1.

[0097] In an optional embodiment, when the measurement signal generation and position selection unit 11255 outputs the AC measurement signals of n measurement frequencies to the first superposition unit 11251, the first superposition unit 11251 generates the first reference voltage V ref1 The second reference voltage V is obtained by superimposing the AC measurement signals of n measurement frequencies. ref2 and the second reference voltage V ref2 Output to the first control unit 11252. The first control unit 11252 outputs the second reference voltage V ref2 The first modulation wave is generated by combining the current output voltage v(t1) of the photovoltaic module 10 and the first modulation wave, and the first modulation wave is output to the second superposition unit 11254. The second superposition unit 11254 outputs the first modulation wave to the first modulation unit 11253. The first modulation unit 11253 generates a first driving signal according to the first modulation wave.

[0098] In another optional embodiment, when the measurement signal generation and position selection unit 11255 outputs the AC measurement signals of n measurement frequencies to the second superposition unit 11254, the first superposition unit 11251 outputs the first reference voltage V to the first control unit 11252. ref1 The first control unit 11252 generates a first reference voltage V ref1 The second modulation wave is generated by combining the current output voltage v(t1) of the photovoltaic module 10 and the current output voltage v(t1) of the photovoltaic module 10, and the second modulation wave is output to the second superposition unit 11254. The second superposition unit 11254 superimposes the second modulation wave with the AC measurement signals of the n measurement frequencies to obtain a third modulation wave, and outputs the third modulation wave to the first modulation unit 11253. The first modulation unit 11253 generates a first drive signal based on the third modulation wave.

[0099] Afterwards, the first modulation unit 11253 outputs the generated first drive signal to the power supply circuit 111. The first drive signal is used to control the switching state of the semiconductor switch device in the power supply circuit 111, thereby generating an AC measurement signal at the port voltage of the photovoltaic module 10, while maintaining the average output voltage of the photovoltaic module 10 equal to the first reference voltage V ref1 .

[0100] The sampling unit 11261 collects the output voltage and output current of the photovoltaic module 10 within a preset time interval under the control of the first driving signal, and outputs the output voltage and output current of the photovoltaic module 10 within the preset time interval to the first filtering unit 11262. The first filtering unit 11262 generates the output voltage and output current of the photovoltaic module 10 within the preset time interval based on the measurement frequency ω of each of the n measurement frequencies. j , perform frequency domain filtering on the output voltage and output current of the photovoltaic module 10 within the preset time interval, and obtain the output voltage and output current of the photovoltaic module 10 at each measurement frequency ω in the n measurement frequencies. j The output voltage v(ω j ) and output current i(ω j ), and the photovoltaic component 10 is measured at each measurement frequency ω in n measurement frequencies j The output voltage v(ω j ) and output current i(ω j ) is output to the equivalent impedance determination module 1121.

[0101] It can be understood that when it is necessary to obtain the output voltage and output current of the photovoltaic component 10 at each measurement frequency in multiple different frequency measurements, it can be achieved by injecting multiple AC measurement signals of different measurement frequencies at one time. Compared with the method of injecting multiple AC measurement signals of different measurement frequencies in batches, it can effectively reduce the workload of the fault measurement device and improve the working efficiency of the fault detection device.

[0102] In another optional embodiment, the control module 1125 respectively ref1 and the AC measurement signal of each measurement frequency in the n measurement frequencies to generate the AC measurement signal of each measurement frequency in the n measurement frequencies ω j The corresponding driving signal, and according to each measurement frequency ω in the n measurement frequencies j The corresponding driving signal controls the output voltage of the photovoltaic assembly 10, wherein the first reference voltage V ref1 is the reference input voltage of the photovoltaic power generation device 10 when it is supplying power to the grid. Then, the acquisition module 1126 acquires the reference input voltage of each measurement frequency ω in the n measurement frequencies. j Under the control of the corresponding driving signal, the photovoltaic component 10 measures the frequency ω at each of the n measurement frequencies. j The output voltage v(ω j ) and output current i(ω j ).

[0103] In this embodiment, the photovoltaic assembly 10 measures the frequency ω of each of the n measurement frequencies. j The output voltage v(ω j ) and output current i(ω j) is obtained in the same way. For ease of understanding, the following takes the first measurement frequency ω1 as an example for introduction.

[0104] Specifically, when the photovoltaic power generation device 11 needs to perform fault detection on the photovoltaic module 10, the sampling unit 11261 collects the port voltage and port current of the photovoltaic module 10 in real time or at a preset frequency, that is, the voltage and current of the port connecting the photovoltaic module 10 and the power supply circuit 111, obtains the current output voltage v(t1) and current output current i(t1) of the photovoltaic module 10, and inputs the collected v(t1) and i(t1) into the first determination module 1127. The first determination module 1127 determines the current working state of the photovoltaic power generation device 11, and determines the first reference voltage V based on the current working state of the photovoltaic power generation device 11, the current output voltage v(t1) and the current output current i(t1) of the photovoltaic module 10. ref1 and the first reference voltage V ref1 Output to the first superposition unit 11251.

[0105] At the same time, the measurement signal generation and position selection unit 11255 generates an AC measurement signal of the first measurement frequency ω1 based on the first measurement frequency ω1 and the AC measurement signal amplitude A1 corresponding to the first measurement frequency ω1, and selects the superposition unit of the AC measurement signal of the first measurement frequency ω1 (i.e., the first superposition unit 11251 or the second superposition unit 11254) based on the first measurement frequency ω1, and then outputs the AC measurement signal of the first measurement frequency ω1 to the first superposition unit 11251 or the second superposition unit 11254.

[0106] Specifically, when the first measurement frequency ω1 is less than the frequency threshold ω b In the case of ω1, the measurement signal generation and position selection unit 11255 determines the superposition unit of the AC measurement signal of the first measurement frequency ω1 as the first superposition unit 11251, and outputs the AC measurement signal of the first measurement frequency ω1 to the first superposition unit 11251. This method is called a closed-loop injection (AC measurement signal) method; when the first measurement frequency ω1 is greater than or equal to the frequency threshold ω b In this case, the measurement signal generation and position selection unit 11255 determines the superposition unit of the AC measurement signal of the first measurement frequency ω1 as the second superposition unit 11254, and outputs the AC measurement signal of the first measurement frequency ω1 to the second superposition unit 11254. This method is called open-loop injection (AC measurement signal) method.

[0107] In an optional embodiment, when the measurement signal generation and position selection unit 11255 outputs the AC measurement signal of the first measurement frequency ω1 to the first superposition unit 11251, the first superposition unit 11251 generates the first reference voltage V ref1The third reference voltage V corresponding to the first measurement frequency ω1 is obtained by superimposing the AC measurement signal of the first measurement frequency ω1. ref31 and the third reference voltage V corresponding to the first measurement frequency ω1 ref31 Output to the first control unit 11252. The first control unit 11252 outputs the third reference voltage V corresponding to the first measurement frequency ω1. ref31 The fourth modulation wave corresponding to the first measurement frequency ω1 is generated based on the current output voltage v(t1) of the photovoltaic module 10, and the fourth modulation wave corresponding to the first measurement frequency ω1 is output to the second superposition unit 11254. The second superposition unit 11254 outputs the fourth modulation wave corresponding to the first measurement frequency ω1 to the first modulation unit 11253. The first modulation unit 11253 generates a driving signal corresponding to the first measurement frequency ω1 based on the fourth modulation wave corresponding to the first measurement frequency ω1.

[0108] In another optional embodiment, when the measurement signal generation and position selection unit 11255 outputs the AC measurement signal of the first measurement frequency ω1 to the second superposition unit 11254, the first superposition unit 11251 outputs the first reference voltage V to the first control unit 11252. ref1 The first control unit 11252 generates a first reference voltage V ref1 and the current output voltage v(t1) of photovoltaic module 10 to generate a fifth modulated wave, and output the fifth modulated wave to second superposition unit 11254. Second superposition unit 11254 superposes the fifth modulated wave with the AC measurement signal of the first measurement frequency ω1 to obtain a sixth modulated wave corresponding to the first measurement frequency ω1, and outputs the sixth modulated wave corresponding to the first measurement frequency ω1 to first modulation unit 11253. First modulation unit 11253 generates a drive signal corresponding to the first measurement frequency ω1 based on the sixth modulated wave corresponding to the first measurement frequency ω1.

[0109] Afterwards, the first modulation unit 11253 outputs the driving signal corresponding to the generated first measurement frequency ω1 to the power supply circuit 111. The driving signal corresponding to the first measurement frequency ω1 is used to control the switching state of the semiconductor switching device in the power supply circuit 111, thereby generating an AC measurement signal at the port voltage of the photovoltaic module 10, while maintaining the average output voltage of the photovoltaic module 10 equal to the first reference voltage V ref1 .

[0110] Sampling unit 11261 collects the output voltage and output current of photovoltaic module 10 during a first time interval Δt1 under control of a drive signal corresponding to a first measurement frequency ω1, and outputs the output voltage and output current of photovoltaic module 10 during the first time interval Δt1 to first filtering unit 11262. First filtering unit 11262 performs frequency-domain filtering on the output voltage and output current of photovoltaic module 10 during the first time interval Δt1 based on the first measurement frequency ω1, thereby obtaining the output voltage v(ω1) and output current i(ω1) of photovoltaic module 10 at the first measurement frequency ω1.

[0111] Furthermore, the photovoltaic module fault detection device can obtain the fault of each measurement frequency ω of the photovoltaic module 10 in the n measurement frequencies based on the above method through the control module 1125 and the acquisition module 1126. j The output voltage v(ω j ) and output current i(ω j ). Then, the first filtering unit 11262 obtains the photovoltaic component 10 at each measurement frequency ω in the n measurement frequencies. j The output voltage v(ω j ) and output current i(ω j ) is output to the equivalent impedance determination module 1121.

[0112] Since the output voltage and output current of the photovoltaic module 10 at each of the above-mentioned multiple measurement frequencies are calculated by sequentially injecting the AC measurement signal of each measurement frequency, this method is a batch injection (AC measurement signal) method.

[0113] It should be noted that when injecting AC measurement signals of different measurement frequencies in batches, the open-loop injection method and the closed-loop injection method cannot be performed at the same time, that is, in the process of injecting an AC measurement signal once, the superposition unit of the AC measurement signal can only select one of the first superposition unit 11251 and the second superposition unit 11254.

[0114] It can be understood that when it is necessary to obtain the output voltage and output current of the photovoltaic component 10 at each measurement frequency in multiple different frequency measurements, it can be achieved by injecting multiple AC measurement signals of different frequencies in batches. Compared with the method of injecting multiple AC measurement signals of different measurement frequencies at one time, this embodiment does not need to limit the size of each measurement frequency in the multiple measurement frequencies, and has strong applicability.

[0115] Then, the equivalent impedance determination module 1121 determines the equivalent impedance of the photovoltaic component 10 based on the respective measurement frequencies ω among the n measurement frequencies. j The output voltage v(ω j ) and output current i(ω j ), calculate the photovoltaic module 10 at each measurement frequency ω jThe equivalent impedance Z(ω j )=v(ω j ) / i(ω j ), and the photovoltaic module 10 is set at each measurement frequency ω j The equivalent impedance Z(ω j ) is output to the impedance deviation acquisition module 1122.

[0116] It can be understood that the fault detection device of the photovoltaic module can realize the injection of the AC measurement signal to the photovoltaic module 10 on the basis of supplying power to the power grid through the control module 1125 and the power supply circuit 111, and then realize the measurement of the equivalent impedance of the photovoltaic module 10 through the acquisition module 1126 and the equivalent impedance determination module 1121. Therefore, when the equivalent impedance of the photovoltaic module 10 is measured, it does not affect the power generation of the photovoltaic system 1. In addition, due to the limited voltage and current levels of the impedance analyzer used in the offline photovoltaic module impedance measurement method, it is impossible to take into account the voltage and current levels of the scenes of large photovoltaic systems (i.e., large photovoltaic power stations) and small photovoltaic systems (i.e., residential photovoltaic systems). The present application can realize the measurement of the equivalent impedance of the photovoltaic module through the photovoltaic power generation equipment connected to the photovoltaic module in the photovoltaic system. Therefore, compared with the offline photovoltaic module impedance measurement method, the present application does not need to add hardware equipment, and can also take into account the voltage and current levels of the corresponding scenes of all photovoltaic systems, and has strong applicability.

[0117] The impedance deviation acquisition module 1122 calculates the impedance deviation of the photovoltaic module 10 at each measurement frequency ω j The equivalent impedance Z(ω j ) and at each measurement frequency ω j The standard equivalent impedance Z REF (ω j ), and the impedance deviation between the photovoltaic module 10 and the measured frequency ω is obtained. j Impedance deviation ΔZ(ω j )=|Z(ω j )-Z REF (ω j )|, and each measurement frequency ω j Impedance deviation ΔZ(ω j ) is output to the judgment unit 11231.

[0118] The judgment unit 11231 judges each measurement frequency ω j Impedance deviation ΔZ(ω j ), that is, ΔZ(ω1),..., ΔZ(ω n), whether any of the n impedance deviations is greater than an impedance deviation threshold. If not, judgment unit 11231 determines that photovoltaic module 10 is healthy. If so, judgment unit 11231 determines that photovoltaic module 10 is at risk of failure and sends an IV curve scanning instruction to second control unit 11232.

[0119] In an optional embodiment, if any one of the n impedance deviations is greater than the impedance deviation threshold, the judgment unit 11231 determines that there is a failure risk in the photovoltaic module 10. It will be appreciated that the photovoltaic module fault detection device can determine that there is a failure risk in the photovoltaic module 10 based on an impedance deviation greater than the impedance deviation threshold, thereby expanding the range of photovoltaic modules at risk of failure and effectively improving the accuracy of fault detection.

[0120] In another optional embodiment, if m impedance deviations are greater than the impedance deviation threshold among the n impedance deviations, and m is greater than a quantity threshold, judgment unit 11231 determines that there is a failure risk in photovoltaic module 10, where the quantity threshold is a positive integer. It is understood that if multiple impedance deviations are greater than the impedance deviation threshold among the n impedance deviations, the photovoltaic module fault detection device determines that there is a failure risk in photovoltaic module 10, and then performs an IV curve scan on the photovoltaic module at risk of failure. This effectively reduces the number of IV curve scans, thereby reducing power fluctuations during detection and thereby increasing the power generation of photovoltaic system 1.

[0121] Based on the IV curve scanning instruction, the second control unit 11232 generates a scanning modulation wave according to the scanning reference voltage and the current output voltage v(t1) of the photovoltaic module 10, and outputs the scanning modulation wave to the second modulation unit 11233. The second modulation unit 11233 generates an IV curve scanning drive signal based on the scanning modulation wave, and outputs the IV curve scanning drive signal to the power supply circuit 111. Under the control of the IV curve scanning drive signal, the power supply circuit 111 controls the output voltage of the photovoltaic module 10, thereby completing the IV curve scanning of the photovoltaic module 10. The acquired IV curve scanning data of the photovoltaic module 10 is then output to the fault determination module 1124. The fault determination module 1124 compares the IV curve scanning data of the photovoltaic module 10 with the IV curve standard data to obtain a detection result for the photovoltaic module 10.

[0122] It should be noted that the photovoltaic module fault detection device in this application has different ways of obtaining the output voltage and output current of the photovoltaic module at each measurement frequency. Specifically, the output voltage and output current of the photovoltaic module at each measurement frequency can be obtained directly by the fault detection device from other devices with the photovoltaic module equivalent impedance measurement function, or can be obtained through control measurement by the fault detection device. This application does not impose any restrictions on this.

[0123] In an embodiment of the present application, the fault detection device of photovoltaic module 10 performs an IV curve scan on photovoltaic module 10 upon determining that a deviation impedance greater than an impedance deviation threshold exists among n impedance deviations of photovoltaic module 10. The device then determines whether photovoltaic module 10 is faulty based on the IV curve scan data obtained from the scan. Because the entire fault detection process for photovoltaic module 10 is performed by the photovoltaic power generation equipment 11 already in photovoltaic system 1, no additional detection equipment or systems are required, nor is it necessary to select different detection equipment for different types of photovoltaic modules. This not only effectively reduces detection costs but also effectively covers all photovoltaic systems requiring photovoltaic module fault detection, resulting in strong applicability. Furthermore, compared to fault detection methods based on multiple IV curve scans, this embodiment performs an IV curve scan on photovoltaic module 10 only when a deviation impedance greater than an impedance deviation threshold exists among n impedance deviations of photovoltaic module 10. This effectively reduces the number of IV curve scans, thereby effectively reducing power fluctuations during detection and thereby increasing the power generation of photovoltaic system 1.

[0124] For the convenience of introduction, the following introduces the fault detection method of photovoltaic modules by taking the method of injecting AC measurement signals of two different measurement frequencies (i.e., the AC measurement signal of the first measurement frequency ω1 and the AC measurement signal of the second measurement frequency ω2) in batches as an example.

[0125] See also Figure 5 , Figure 5 This is another schematic diagram of the photovoltaic system provided by this application. Figure 5 As shown, the photovoltaic system 1 includes a photovoltaic module 10, a DC / DC converter and a DC bus (i.e., a positive DC bus BUS+ and a negative DC bus BUS-). The photovoltaic module 10 is connected to the two input terminals i11+ and i11- of the DC / DC converter, and the two output terminals o11+ and o11- of the DC / DC converter are connected to the DC grid through the DC bus. Figure 5 In the photovoltaic system 1 shown, the photovoltaic power generation device 11 provided in this application is a DC / DC converter, which includes a power supply circuit 111 and a controller 112. The two input terminals i111+ and i111- of the power supply circuit 111 are respectively connected to the two input terminals i11+ and i11- of the DC / DC converter, and the two output terminals o111+ and o111- of the power supply circuit 111 are respectively connected to the two output terminals o11+ and o11- of the DC / DC converter. The power supply circuit 111 can be a Boost circuit, a Buck circuit, or a Buck-Boost circuit.

[0126] Furthermore, for the convenience of description, the following description is made by taking the power supply circuit 111 as a Boost circuit as an example. Figure 6 , Figure 6 This is another schematic diagram of the structure of the photovoltaic system provided by this application. Figure 6 As shown, the power supply circuit 111 is a Boost circuit composed of capacitors C1, C2, an inductor L, a switch tube Q and a diode D. Figure 6 The photovoltaic module fault detection device shown is Figure 5 The controller 112 shown corresponds to .

[0127] In an optional embodiment, after the photovoltaic system 1 starts working, the DC / DC converter performs MPPT to maximize the output power. At this time, the DC / DC converter is in a non-power-limited working state. When it is necessary to perform fault detection on the photovoltaic assembly 10, the first determination module 1127 obtains the current output voltage v(t1) and the current output current i(t1) of the photovoltaic assembly 10 through the sampling unit 11261, and calculates the current output power of the photovoltaic assembly 10. When the current output power of the photovoltaic assembly 10 is less than or equal to the maximum output power of the DC / DC converter, the first determination module 1127 determines that the current working state of the DC / DC converter is a non-power-limited working state, and changes the output power of the photovoltaic assembly 10 by changing the voltage of the connection port between the photovoltaic assembly 10 and the power supply circuit 111 (i.e., the output voltage of the photovoltaic assembly 10), and determines the output voltage of the photovoltaic assembly 10 corresponding to the maximum value among the multiple changed output powers of the photovoltaic assembly 10 as the first reference voltage V ref1 .

[0128] In another optional embodiment, after the photovoltaic system 1 starts working, the DC / DC converter is in a power-limited working state according to the received power-limiting instruction. When it is necessary to perform fault detection on the photovoltaic component 10, the first determination module 1127 obtains the current output voltage v(t1) and the current output current i(t1) of the photovoltaic component 10 through the sampling unit 11261, and calculates the current output power of the photovoltaic component 10. When the current output power of the photovoltaic component 10 is greater than the maximum output power of the DC / DC converter, the first determination module 1127 determines that the current working state of the DC / DC converter is a power-limited working state. The first determination module 1127 determines that the current working state of the DC / DC converter is a power-limited working state according to the current output power P of the photovoltaic component 10 and the reference output power P ref , the output power error ΔP=P ref -P, and output the output power error ΔP to the power controller in the first determination module 1127, such as a proportional integral (PI) controller. The power controller outputs a first reference voltage V according to the output power error ΔP. ref1 .

[0129] It can be understood that the first reference voltage V ref1 Corresponding to the current working state of the DC / DC converter, the first reference voltage V ref1 This does not correspond to the current working state of the DC / DC converter, resulting in the inability to meet the requirement of the DC / DC converter to normally supply power to the grid in different working states. Therefore, the stability of the photovoltaic system 1 can be improved, and the applicability is strong.

[0130] The first determining module 1127 determines the first reference voltage V ref1 After that, the first reference voltage V ref1 Output to the first superposition unit 11251.

[0131] At the same time, the measurement signal generation and position selection unit 11255 generates an AC measurement signal of the first measurement frequency ω1 according to the first measurement frequency ω1 and the first amplitude A1. Assume that the first measurement frequency ω1 is less than the frequency threshold ω b , the measurement signal generation and position selection unit 11255 determines that the first superposition unit 11251 is the superposition unit of the AC measurement signal of the first measurement frequency ω1, and outputs the AC measurement signal of the first measurement frequency ω1 to the first superposition unit 11251.

[0132] The first superimposing unit 11251 adds the first reference voltage V ref1 The third reference voltage V corresponding to the first measurement frequency ω1 is obtained by superimposing the AC measurement signal of the first measurement frequency ω1. ref31 and the third reference voltage V corresponding to the first measurement frequency ω1 ref31 Output to the first control unit 11252. The first control unit 11252 outputs the third reference voltage V corresponding to the first measurement frequency ω1. ref31 The first control unit 11252 generates a fourth modulated wave corresponding to the first measurement frequency ω1 based on the current output voltage v(t1) of the photovoltaic module 10, and outputs the fourth modulated wave corresponding to the first measurement frequency ω1 to the second superposition unit 11254. The first control unit 11252 herein may be a voltage controller, such as a PI regulator. The second superposition unit 11254 outputs the fourth modulated wave corresponding to the first measurement frequency ω1 to the first modulation unit 11253. The first modulation unit 11253 generates a drive signal (e.g., a square wave) corresponding to the first measurement frequency ω1 based on the fourth modulated wave corresponding to the first measurement frequency ω1. The first modulation unit 11253 herein may be a pulse width modulation (PWM) unit.

[0133] Afterwards, the first modulation unit 11253 outputs the driving signal corresponding to the generated first measurement frequency ω1 to the switch tube Q in the power supply circuit 111. The driving signal corresponding to the first measurement frequency ω1 is used to control the conduction time of the switch tube Q, thereby generating an AC measurement signal of the first measurement frequency ω1 at the output voltage of the photovoltaic module 10, while maintaining the average value of the output voltage of the photovoltaic module 10 equal to the first reference voltage V ref1 .

[0134] The sampling unit 11261 collects the output voltage and output current of the photovoltaic module 10 during a first time interval Δt1 under the control of the driving signal corresponding to the first measurement frequency ω1, and outputs the output voltage and output current of the photovoltaic module 10 during the first time interval Δt1 to the first filtering unit 11262. The first filtering unit 11262 performs a discrete Fourier transform (DFT) on the output voltage and output current of the photovoltaic module 10 during the first time interval Δt1 based on the first measurement frequency ω1, thereby obtaining the output voltage v(ω1) and output current i(ω1) of the photovoltaic module 10 at the first measurement frequency ω1, and outputs the output voltage v(ω1) and output current i(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 to the equivalent impedance determination module 1121. The equivalent impedance determination module 1121 calculates the equivalent impedance Z(ω1)=v(ω1) / i(ω1) of the photovoltaic component 10 at the first measurement frequency ω1 based on the output voltage v(ω1) and output current i(ω1) of the photovoltaic component 10 at the first measurement frequency ω1, and outputs the equivalent impedance Z(ω1) of the photovoltaic component 10 at the first measurement frequency ω1 to the impedance deviation acquisition module 1122.

[0135] Afterwards, the measurement signal generation and position selection unit 11255 generates an AC measurement signal of the second measurement frequency ω2 according to the second measurement frequency ω2 and the second amplitude A2. Assume that the second measurement frequency ω2 is greater than the frequency threshold ω b , the measurement signal generation and position selection unit 11255 determines that the second superposition unit 11254 is the superposition unit of the AC measurement signal of the second measurement frequency ω2, and outputs the AC measurement signal of the second measurement frequency ω2 to the second superposition unit 11254.

[0136] The first superimposing unit 11251 outputs the first reference voltage V to the first control unit 11252 ref1 The first control unit 11252 generates a first reference voltage V ref1and the current output voltage v(t1) of the photovoltaic module 10 to generate a fifth modulated wave, and output the fifth modulated wave to the second superposition unit 11254. The second superposition unit 11254 superimposes the fifth modulated wave and the AC measurement signal of the second measurement frequency ω2 to obtain a sixth modulated wave corresponding to the second measurement frequency ω2, and outputs the sixth modulated wave corresponding to the second measurement frequency ω2 to the first modulation unit 11253. The first modulation unit 11253 generates a drive signal corresponding to the second measurement frequency ω2 based on the sixth modulated wave corresponding to the second measurement frequency ω2.

[0137] Afterwards, the first modulation unit 11253 outputs the driving signal corresponding to the generated second measurement frequency ω2 to the switch tube Q in the power supply circuit 111. The driving signal corresponding to the second measurement frequency ω2 is used to control the conduction time of the switch tube Q, thereby generating an AC measurement signal of the second measurement frequency ω2 at the output voltage of the photovoltaic component 10, while maintaining the average value of the output voltage of the photovoltaic component 10 equal to the first reference voltage V ref1 .

[0138] Sampling unit 11261 collects the output voltage and output current of photovoltaic module 10 during the second time interval Δt2 under the control of the driving signal corresponding to the second measurement frequency ω2, and outputs the output voltage and output current of photovoltaic module 10 during the second time interval Δt2 to first filtering unit 11262. First filtering unit 11262 performs a DFT on the output voltage and output current of photovoltaic module 10 during the second time interval Δt2 based on the second measurement frequency ω2, thereby obtaining the output voltage v(ω2) and output current i(ω2) of photovoltaic module 10 at the second measurement frequency ω2, and outputs the output voltage v(ω2) and output current i(ω2) of photovoltaic module 10 at the second measurement frequency ω2 to equivalent impedance determination module 1121. The equivalent impedance determination module 1121 calculates the equivalent impedance Z(ω2)=v(ω2) / i(ω2) of the photovoltaic component 10 at the second measurement frequency ω2 based on the output voltage v(ω2) and output current i(ω2) of the photovoltaic component 10 at the second measurement frequency ω2, and outputs the equivalent impedance Z(ω2) of the photovoltaic component 10 at the second measurement frequency ω2 to the impedance deviation acquisition module 1122.

[0139] The impedance deviation acquisition module 1122 calculates the impedance deviation ΔZ(ω1)=|Z(ω1)-Z at the first measurement frequency ω1 of the photovoltaic component 10 based on the equivalent impedance Z(ω1) of the photovoltaic component 10 at the first measurement frequency ω1 and the equivalent impedance Z(ω2) at the second measurement frequency ω2. REF (ω1)| and the impedance deviation ΔZ(ω2) at the second measurement frequency ω2 = |Z(ω2)-Z REF(ω2)|, and output the equivalent impedance Z(ω1) of the first measurement frequency ω1 and the equivalent impedance Z(ω2) of the second measurement frequency ω2 to the judgment unit 11231. REF (ω1) is the standard equivalent impedance of the photovoltaic module 10 at the first measurement frequency ω1, Z REF (ω2) is the standard equivalent impedance of the photovoltaic assembly 10 at the second measurement frequency ω2.

[0140] The judgment unit 11231 judges whether there is an impedance deviation ΔZ(ω1) greater than the impedance deviation threshold Z in the first measurement frequency ω1 and the impedance deviation ΔZ(ω2) of the second measurement frequency ω2. TH If the impedance deviation does not exist, the judgment unit 11231 determines that the photovoltaic component 10 is healthy. Otherwise, the judgment unit 11231 determines that the photovoltaic component 10 has a failure risk. TH Or ΔZ(ω2)>Z TH In the case of ΔZ(ω1)>Z TH And ΔZ(ω2)>Z TH In the case of , the judgment unit 11231 determines that the photovoltaic component 10 has a failure risk.

[0141] When the judgment unit 11231 determines that there is a risk of failure in the photovoltaic module 10, it sends an IV curve scanning instruction to the second control unit 11232. Based on the IV curve scanning instruction, the second control unit 11232 generates a scanning modulation wave according to the scanning reference voltage and the current output voltage v(t1) of the photovoltaic module 10, and outputs the scanning modulation wave to the second modulation unit 11233. The second modulation unit 11233 generates an IV curve scanning drive signal based on the scanning modulation wave, and outputs the IV curve scanning drive signal to the power supply circuit 111, so that the power supply circuit 111 controls the output voltage of the photovoltaic module 10 from the first reference voltage V under the control of the IV curve scanning drive signal. ref1 The voltage changes from the open circuit voltage to the short circuit voltage according to the preset decreasing rule, and then gradually increases from the short circuit voltage to the open circuit voltage according to the preset increasing rule, and finally changes from the open circuit voltage to the first reference voltage V ref1 The preset drop rule may be at least one of a voltage drop rule with a fixed voltage difference, a parabolic voltage drop rule, or a voltage drop rule with a fixed duty cycle change rate, and the preset drop rule is completely opposite to the preset rise rule.

[0142] At the same time, sampling unit 11261 obtains the output voltage of photovoltaic module 10 and the output current corresponding to the output voltage during the falling phase scanning period to obtain falling phase sampling data of photovoltaic module 10, and obtains the output voltage of photovoltaic module 10 and the output current corresponding to the output voltage during the rising phase scanning period to obtain rising phase sampling data of photovoltaic module 10, and outputs the falling phase sampling data and rising phase sampling data of photovoltaic module 10 to second filtering unit 11264. The falling phase scanning period is the time period corresponding to the process in which the output voltage of photovoltaic module 10 gradually decreases from the open-circuit voltage to the short-circuit voltage, and the rising phase scanning period is the time period corresponding to the process in which the output voltage of photovoltaic module 10 gradually increases from the short-circuit voltage to the open-circuit voltage. The sum of the falling phase scanning period and the rising phase scanning period is the IV curve scanning period of photovoltaic module 10.

[0143] The second filtering unit 11264 performs low-pass filtering on the falling phase sampling data and the rising phase sampling data of the photovoltaic component 10, retains the DC part of the above scanning data, thereby obtaining the falling phase scanning data and the rising phase scanning data of the photovoltaic component 10, and outputs the falling phase scanning data and the rising phase scanning data of the photovoltaic component 10 to the IV curve data generation unit 11265.

[0144] The IV curve data generating unit 11265 compares the descending phase scanning data of the photovoltaic module 10 during the descending phase scanning period with the ascending phase scanning data of the photovoltaic module 10 during the ascending phase scanning period, and outputs the IV curve scanning data of the photovoltaic module 10 based on the comparison result. The IV curve scanning data of the photovoltaic module 10 may be the descending phase scanning data of the photovoltaic module 10 or the ascending phase scanning data of the photovoltaic module 10, or may be characteristic values ​​of the IV curve of the photovoltaic module 10 (e.g., the curvature value or second-order derivative value at any point on the IV curve).

[0145] In an optional embodiment, the IV curve data generating unit 11265 obtains K descending phase scanning data P from the descending phase scanning data of the photovoltaic assembly 10. 11 (v 11 ,i 11 ), P 11 (v 12 ,i 12 ),……,P 1K (v 1K ,i 1K ), and obtain K rising phase scanning data P corresponding to the output voltage values ​​in the K falling phase scanning data from the rising phase scanning data of the photovoltaic module 10 21 (v 21 ,i 21 ), P21 (v 22 ,i 22 ),……,P 2K (v 2K ,i 2K ), and calculate I1=(i 11 ,i 12 ,……,i 1K ) and I2=(i 21 ,i 22 ,……,i 2K ) Correlation coefficient between the two sets of data. Wherein, K is a positive integer, usually 32. If the correlation coefficient between the two sets of data is less than the preset correlation coefficient threshold, the IV curve data generation unit 11265 sends a message that the IV curve scan of the string has failed. If the correlation coefficient between the two sets of data is greater than or equal to the preset correlation coefficient threshold, the IV curve data generation unit 11265 determines the K descending phase scan data as the IV curve scan data of the photovoltaic module 10, or the IV curve data generation unit 11265 draws the IV curve of the photovoltaic module 10 based on the K descending phase scan data, calculates the characteristic value of the IV curve of the photovoltaic module 10, and determines the characteristic value of the IV curve of the photovoltaic module 10 as the IV curve scan data of the photovoltaic module 10. It can be understood that the fault detection device obtains the IV curve scan data of the photovoltaic module 10 by comparing the descending phase scan data and the ascending phase scan data, which can effectively solve the problem of low accuracy of the IV curve scan result of the photovoltaic module due to changes in light during the IV curve scanning process, thereby improving the accuracy of the IV curve scan result of the photovoltaic module.

[0146] Afterwards, the IV curve data generation unit 11265 outputs the IV curve scan data of the photovoltaic module 10 to the fault determination module 1124. The fault determination module 1124 compares the IV curve scan data of the photovoltaic module 10 with the IV curve standard data to obtain a test result for the photovoltaic module 10. If the IV curve scan data of the photovoltaic module 10 is falling phase scan data, the IV curve standard data includes a standard output voltage value and a standard output current value corresponding to the standard output voltage, and the standard output voltage value is the same as the output voltage value in the falling phase scan data. If the IV curve scan data of the photovoltaic module 10 is rising phase scan data, the IV curve standard data includes a standard output voltage value and a standard output current value corresponding to the standard output voltage, and the standard output voltage value is the same as the output voltage value in the rising phase scan data.

[0147] In an alternative embodiment, when the IV curve data of the photovoltaic module 10 comprises K falling phase scan data, the fault determination module 1124 calculates the absolute value of the difference between the output current value in each falling phase scan data and the standard output current value corresponding to the same standard output voltage value as the output voltage value in each falling phase scan data, thereby obtaining K current deviation values. If any of the K current deviation values ​​is greater than a current deviation threshold, a fault is determined in the photovoltaic module 10.

[0148] In another alternative embodiment, when the IV curve data of PV module 10 is a curvature value at any point on the IV curve, fault determination module 1124 calculates the absolute value of the difference between the curvature value at any point on the IV curve and a standard curvature value (i.e., the IV curve standard data) to obtain a curvature deviation value. If the curvature deviation value is greater than a deviation threshold, fault determination module 1124 determines that PV module 10 is faulty.

[0149] In the embodiment of the present application, the fault detection device of the photovoltaic module 10 performs an IV curve scan on the photovoltaic module 10 when it determines that one of the two impedance deviations of the photovoltaic module 10 has a deviation impedance greater than an impedance deviation threshold. The device then determines whether the photovoltaic module 10 is faulty based on the IV curve scan data obtained from the scan. Because the entire fault detection process for the photovoltaic module 10 is performed by the existing DC / DC converter in the photovoltaic system 1, no additional detection equipment or systems are required, nor is it necessary to select different detection equipment for different types of photovoltaic modules. This not only effectively reduces detection costs but also effectively covers all photovoltaic systems requiring photovoltaic module fault detection, resulting in strong applicability. Furthermore, compared to fault detection methods based on multiple IV curve scans, this embodiment performs an IV curve scan on the photovoltaic module 10 only when one of the two impedance deviations of the photovoltaic module 10 has a deviation impedance greater than the impedance deviation threshold. This effectively reduces the number of IV curve scans, thereby effectively reducing power fluctuations during detection and thereby increasing the power generation of the photovoltaic system 1. Compared with the method of fault detection based on the equivalent impedance of the photovoltaic module, the present application determines whether the photovoltaic module is faulty based on the equivalent impedance of the photovoltaic module and the IV curve scanning result, thereby effectively improving the fault detection accuracy.

[0150] Furthermore, in order to better understand Figure 5 and Figure 6 The corresponding embodiment is shown below in conjunction with the waveforms of the output voltage and output current of the photovoltaic module during the fault detection process. Figure 5 and Figure 6 The corresponding embodiments are supplemented.

[0151] See Figure 7 , Figure 7It is a schematic waveform diagram of the output voltage and output current of a photovoltaic module during the fault detection provided by this application. As Figure 7 shown, when 0 < t < T1, after the DC / DC converter starts to operate, a first reference voltage V ref1 is determined according to the current operating state of the DC / DC converter, and the output voltage v(t) of the photovoltaic module 10 is maintained at the first reference voltage V ref1 . During this period, the DC / DC converter is in the normal power generation operating state.

[0152] At time T1, the DC / DC converter enters the first impedance measurement period (i.e., the period corresponding to T1 to T2), and performs the first equivalent impedance measurement of the photovoltaic module 10. The conduction duration of the switching transistor Q is controlled according to the driving signal corresponding to the first measurement frequency ω1 to inject an AC measurement signal with the first measurement frequency ω1 into the photovoltaic module 10. The output voltage v(t) and output current i(t) of the photovoltaic module 10 during the first time interval Δt1 under the control of the driving signal corresponding to the first measurement frequency ω1 are recorded. After the output voltage v(t) and output current i(t) of the photovoltaic module 10 during the first time interval Δt1 are recorded, the DC / DC converter stops injecting the AC measurement signal with the first measurement frequency ω1 into the photovoltaic module 10 and resumes the normal power generation operating state (i.e., ensuring that the output voltage v(t) of the photovoltaic module 10 is maintained at the first reference voltage V ref1 ), and the equivalent impedance Z(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 is calculated according to the output voltage v(t) and output current i(t) of the photovoltaic module 10 during the first time interval Δt1.

[0153] At time T2, the DC / DC converter enters the second impedance measurement period (i.e., the period corresponding to T2 to T3), and performs the second equivalent impedance measurement of the photovoltaic module 10. The conduction duration of the switching transistor Q is controlled according to the driving signal corresponding to the second measurement frequency ω2 to inject an AC measurement signal with the second measurement frequency ω2 into the photovoltaic module 10. The output voltage v(t) and output current i(t) of the photovoltaic module 10 during the second time interval Δt2 under the control of the driving signal corresponding to the second measurement frequency ω2 are recorded. After the output voltage v(t) and output current i(t) of the photovoltaic module 10 during the second time interval Δt2 are recorded, the DC / DC converter stops injecting the AC measurement signal with the second measurement frequency ω2 into the photovoltaic module 10 and resumes the normal power generation operating state, and the equivalent impedance Z(ω2) of the photovoltaic module 10 at the second measurement frequency ω2 is calculated according to the output voltage v(t) and output current i(t) of the photovoltaic module 10 during the second time interval Δt2.

[0154] At time T3, the DC / DC converter enters the impedance deviation calculation and judgment period (i.e., the time period corresponding to T3 to T4), and calculates the impedance deviation ΔZ(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 and the impedance deviation ΔZ(ω2) at the second measurement frequency ω2 respectively according to the equivalent impedance Z(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 and the equivalent impedance Z(ω2) at the second measurement frequency ω2. And when ΔZ(ω1) is less than or equal to the impedance deviation threshold Z TH and ΔZ(ω2) is less than or equal to the impedance deviation threshold Z TH the DC / DC converter determines that the photovoltaic module 10 is healthy. Meanwhile, the DC / DC converter remains in the normal power generation operation state during the entire impedance deviation calculation and judgment period.

[0155] After time T4, that is, after completing the fault detection of the photovoltaic module 10 and determining that the photovoltaic module 10 is healthy, the DC / DC converter is in the normal power generation operation state.

[0156] Further, in the case where a fault risk of the photovoltaic module is determined in the impedance deviation calculation and judgment stage, the DC / DC converter needs to perform an IV curve scan on the photovoltaic module. Please refer to Figure 8 , Figure 8 which is another waveform diagram of the output voltage and output current of the photovoltaic module during the fault detection provided by this application. As Figure 8 shown, from 0 < t < T1, the DC / DC converter is in the normal power generation operation state. At time T1, the DC / DC converter enters the first impedance measurement period (i.e., the time period corresponding to T1 to T2), performs the first equivalent impedance measurement of the photovoltaic module 10, and calculates the equivalent impedance Z(ω1) of the photovoltaic module 10 at the first measurement frequency ω1. After time T2, the DC / DC converter enters the second impedance measurement period (i.e., the time period corresponding to T2 to T3) to perform the second equivalent impedance measurement of the photovoltaic module 10, and calculates the equivalent impedance Z(ω2) of the photovoltaic module 10 at the second measurement frequency ω2. Here, Figure 8 the specific description of the period from 0 to T3 in Figure 7 [[ID=?]]Please refer to the corresponding part of the description in

[0157] At time T3, the DC / DC converter enters the impedance deviation calculation and judgment period (i.e., the time period corresponding to T3 to T4), and calculates the impedance deviation ΔZ(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 and the impedance deviation ΔZ(ω2) at the second measurement frequency ω2 respectively according to the equivalent impedance Z(ω1) of the photovoltaic module 10 at the first measurement frequency ω1 and the equivalent impedance Z(ω2) at the second measurement frequency ω2. And when there is a value greater than the impedance deviation threshold Z in ΔZ(ω1) and ΔZ(ω2) TH It should be noted that there seems to be an error in the original text where "Please refer to " in is not properly translated in the provided translation. It should be something like "Please refer to the description in " instead of "Please refer to the specific description of the period from 0 to T3 in " which doesn't make complete sense in the context. The above translation is adjusted as much as possible based on the correct understanding of the text.In the case of an impedance deviation of 0.001%, the DC / DC converter determines that there is a risk of failure in the photovoltaic assembly 10. Meanwhile, the DC / DC converter remains in a normal power generation operation state during the entire impedance deviation calculation and judgment period.

[0158] At time T4, the DC / DC converter enters the IV curve scanning period (i.e., the period corresponding to T4 to T5), and controls the conduction time of the switch tube Q according to the IV curve scanning driving signal to achieve the output voltage of the photovoltaic module 10 from the first reference voltage V ref1 First, it gradually rises to the open circuit voltage. At the same time, the output current of the photovoltaic module 10 increases from the first reference voltage V ref1 The corresponding reference current I ref1 Gradually decreases until it reaches zero. Secondly, in the descending phase, the scanning cycle (ie t 41 to t 42 During the period corresponding to the time period, the output voltage of the photovoltaic module 10 gradually decreases from the open circuit voltage to the short circuit voltage (i.e., 0) according to the voltage drop rule of the fixed voltage difference. At the same time, the output current of the photovoltaic module 10 gradually increases from zero to the current peak. 42 to t 43 During the time period corresponding to the fixed voltage difference, the output voltage of the photovoltaic module 10 gradually increases from the short-circuit voltage to the open-circuit voltage. At the same time, the output current of the photovoltaic module 10 gradually decreases from the current peak to zero. Finally, the output voltage of the photovoltaic module 10 gradually decreases from the open-circuit voltage to the first reference voltage V ref1 At the same time, the output current of the photovoltaic module 10 gradually increases from zero to the first reference voltage V ref1 The corresponding reference current I ref1 In addition, during the IV curve scanning period, the DC / DC converter also obtains the descending phase scanning data of the photovoltaic module 10 in the descending phase scanning cycle and the ascending phase scanning data of the photovoltaic module 10 in the ascending phase scanning cycle, and obtains the IV curve scanning data of the photovoltaic module 10 based on the descending phase scanning data and the ascending phase scanning data.

[0159] At time T5, the DC / DC converter enters the IV curve scan data judgment period. If the deviation between the IV curve scan data of PV module 10 and the IV curve standard data exceeds the deviation threshold, the DC / DC converter determines that PV module 10 has failed. Meanwhile, the DC / DC converter operates normally during the entire IV curve scan data judgment period.

[0160] Depend on Figure 7 and Figure 8It can be seen that during the measurement of the equivalent impedance of the photovoltaic module 10, the output voltage v(t) and the output current i(t) of the photovoltaic module 10 only fluctuate slightly, and the average output voltage and the average output current of the photovoltaic module 10 are respectively maintained at the first reference voltage V ref1 and the first reference voltage V ref1 The corresponding reference current I ref1 Therefore, the equivalent impedance measurement method of the photovoltaic module provided by the present application will only cause a small power fluctuation during the measurement process, and will not affect the power generation of the photovoltaic system 1 like the offline photovoltaic module impedance measurement method, and has strong applicability.

[0161] See also Figure 9 , Figure 9 This is another schematic diagram of the photovoltaic system provided by this application. Figure 9 As shown, the photovoltaic system 1 includes a photovoltaic module 10 and an inverter, and the photovoltaic module 10 is connected to the AC power grid through the inverter. Figure 9 In the photovoltaic system 1 shown, the photovoltaic power generation device 11 provided in this application is an inverter, which includes a power supply circuit 111 and a controller 112. The two input terminals i111+ and i111- of the power supply circuit 111 are respectively connected to the two input terminals i11+ and i11- of the inverter, and the three output terminals o1111, o1112, and o1113 of the power supply circuit 111 are respectively connected to the three output terminals o111, o112, and o113 of the inverter. The power supply circuit 111 is an inverter circuit, which includes a first-phase bridge arm, a second-phase bridge arm, and a third-phase bridge arm, and the first-phase bridge arm, the second-phase bridge arm, and the third-phase bridge arm are all connected in parallel to the input terminals of the inverter circuit.

[0162] Further, Figure 9 The photovoltaic system shown can be equivalent to Figure 10 The photovoltaic system shown in Figure 1 is Figure 10 As shown, Figure 10 The photovoltaic module fault detection device shown is Figure 9 The controller 112 shown corresponds to the controller 112. In addition, to simplify the description, the three-phase AC variables are represented by a simplified representation method, that is, three short slashes are used to represent the variables or electrical three-phase variables, for example Figure 10 Medium AC current i g , which actually includes the three-phase current information of phase A, phase B and phase C. In addition, since the output end of the photovoltaic system 1 in this embodiment is connected to the AC power grid, Figure 6Compared to the fault detection device shown in FIG. 1 , the fault detection device in this embodiment further includes a first AC sampling module 1125, the control module 1125 further includes a first AC current control unit 11256, and the IV curve acquisition module 1123 further includes a second AC current control unit 11236. The first AC current control unit 11256 and the second AC current control unit 11236 can be the same AC current control unit or two different AC current control units, and this application does not impose any restrictions on this.

[0163] The first AC sampling module 1125 is used to collect the AC current i at the output port of the power supply circuit 111. g The AC current amplitude and AC voltage phase are controlled. The first AC current control unit 11256 and the second AC current control unit 11236 are both used to control the AC current amplitude at the output port of the power supply circuit 111 to ensure normal power generation of the photovoltaic system 1. The first modulation unit 11253 and the second modulation unit 11233 are also used to convert the control variable at the DC end into an electrical variable that matches the AC port.

[0164] In an optional embodiment, after the photovoltaic system 1 starts working, the inverter is in a power-limited working state or a non-power-limited working state. When it is necessary to perform fault detection on the photovoltaic assembly 10, the first determination module 1127 determines the current working state of the inverter and determines the first reference voltage V according to the current working state of the inverter. ref1 .

[0165] At the same time, the measurement signal generation and position selection unit 11255 generates an AC measurement signal of the first measurement frequency ω1 according to the first measurement frequency ω1 and the first amplitude A1. Assume that the first measurement frequency ω1 is less than the frequency threshold ω b , the measurement signal generation and position selection unit 11255 determines that the first superposition unit 11251 is the superposition unit of the AC measurement signal of the first measurement frequency ω1, and outputs the AC measurement signal of the first measurement frequency ω1 to the first superposition unit 11251.

[0166] The first superimposing unit 11251 adds the first reference voltage V ref1 The third reference voltage V corresponding to the first measurement frequency ω1 is obtained by superimposing the AC measurement signal of the first measurement frequency ω1. ref31 and the third reference voltage V corresponding to the first measurement frequency ω1 ref31 Output to the first control unit 11252. The first control unit 11252 outputs the third reference voltage V corresponding to the first measurement frequency ω1. ref31The first AC current control unit 11256 generates a fourth modulated wave corresponding to the first measured frequency ω1 based on the current output voltage v(t1) of the photovoltaic module 10 and the collected AC current amplitude and reference AC current amplitude, thereby adjusting the amplitude of the fourth modulated wave corresponding to the first measured frequency ω1 to obtain an adjusted fourth modulated wave corresponding to the first measured frequency ω1, thereby ensuring the normal power generation function of the photovoltaic system 1. The first AC current control unit 11256 outputs the modulated fourth modulated wave corresponding to the first measured frequency ω1 to the second superposition unit 11254. The second superposition unit 11254 outputs the modulated fourth modulated wave corresponding to the first measured frequency ω1 to the first modulation unit 11253. The first modulation unit 11253 generates a drive signal corresponding to the first measured frequency ω1 based on the modulated fourth modulated wave corresponding to the first measured frequency ω1. The drive signal corresponding to the first measured frequency ω1 includes a first drive sub-signal, a second drive sub-signal, and a third drive sub-signal. Specifically, the first modulation unit 11253 first generates a first driving sub-signal according to the fourth modulation wave corresponding to the modulated first measurement frequency ω1, and then performs a phase shift on the first driving sub-signal according to the phase of the AC voltage to obtain a second driving sub-signal and a third driving sub-signal, and outputs the first driving sub-signal, the second driving sub-signal, and the third driving sub-signal to the switch tube of the first phase bridge arm, the switch tube of the second phase bridge arm, and the switch tube of the third phase bridge arm, respectively. The first driving sub-signal is used to control the conduction time of the switch tube of the first phase bridge arm, the second driving sub-signal is used to control the conduction time of the switch tube of the second phase bridge arm, and the third driving sub-signal is used to control the conduction time of the switch tube of the third phase bridge arm, thereby generating an AC measurement signal of the first measurement frequency ω1 at the output voltage of the photovoltaic module 10, while maintaining the average value of the output voltage of the photovoltaic module 10 equal to the first reference voltage V ref1 It should be noted that the switch tubes of the above-mentioned first phase bridge arm to the third phase bridge arm can be the switch tubes located at the top or the switch tubes located at the bottom in each phase bridge arm, and the driving sub-signal of the switch tube located at the top in the same phase bridge arm is complementary to the driving sub-signal of the switch tube located at the bottom.

[0167] The fault detection device of the photovoltaic component 10 obtains the output voltage v(ω1) and the output current i(ω1) of the photovoltaic component 10 at the first measuring frequency ω1 under the control of the driving signal corresponding to the first measuring frequency ω1, and then calculates the equivalent impedance Z(ω1)=v(ω1) / i(ω1) of the photovoltaic component 10 at the first measuring frequency ω1.

[0168] Afterwards, the fault detection device of the photovoltaic assembly 10 may calculate the equivalent impedance Z(ω2)=v(ω2) / i(ω2) of the photovoltaic assembly 10 at the second measurement frequency ω2 according to the above method.

[0169] The fault detection device of the photovoltaic component 10 calculates the impedance deviation ΔZ(ω1) of the photovoltaic component 10 at the first measuring frequency ω1 and the impedance deviation ΔZ(ω2) at the second measuring frequency ω2 according to the equivalent impedance Z(ω1) of the photovoltaic component 10 at the first measuring frequency ω1 and the equivalent impedance Z(ω2) of the photovoltaic component 10 at the second measuring frequency ω2, and the impedance deviation ΔZ(ω1) and the impedance deviation ΔZ(ω2) of the photovoltaic component 10 are greater than the impedance deviation threshold Z TH In the case of impedance deviation, the IV curve of the photovoltaic component 10 is scanned.

[0170] The specific implementation process of the fault detection device of the photovoltaic module 10 performing IV curve scanning on the photovoltaic module 10 is as follows: the judgment unit 11231 determines whether there is an impedance deviation threshold value Z greater than ΔZ(ω1) and ΔZ(ω2). TH In the event of an impedance deviation, an IV curve scanning instruction is sent to the second control unit 11232. Based on the IV curve scanning instruction, the second control unit 11232 generates a scanning modulation wave according to the scanning reference voltage and the current output voltage v(t1) of the photovoltaic module 10, and outputs the scanning modulation wave to the second AC current control unit 11236. The second AC current control unit 11236 adjusts the amplitude of the scanning modulation wave based on the collected AC current amplitude and the reference AC current amplitude, thereby obtaining an adjusted scanning modulation wave to ensure the normal power generation function of the photovoltaic system 1. The second AC current control unit 11236 outputs the adjusted scanning modulation wave to the second modulation unit 11233. The second modulation unit 11233 generates an IV curve scanning drive signal according to the phase of the AC voltage and the adjusted scanning modulation wave, namely the first scanning drive sub-signal, the second scanning drive sub-signal and the third scanning drive sub-signal, and outputs the first scanning drive sub-signal, the second scanning drive sub-signal and the third scanning drive sub-signal to the switch tube of the first phase bridge arm, the switch tube of the second phase bridge arm and the switch tube of the third phase bridge arm respectively. The first scanning drive sub-signal is used to control the conduction time of the switch tube of the first phase bridge arm, the second scanning drive sub-signal is used to control the conduction time of the switch tube of the second phase bridge arm, and the third scanning drive sub-signal is used to control the conduction time of the switch tube of the third phase bridge arm, thereby controlling the output voltage of the photovoltaic module 10 from the first reference voltage V ref1 The voltage changes from the open circuit voltage to the short circuit voltage according to the preset decreasing rule, and then gradually increases from the short circuit voltage to the open circuit voltage according to the preset increasing rule, and finally changes from the open circuit voltage to the first reference voltage V ref1 .

[0171] At the same time, the fault detection device of the photovoltaic component 10 obtains the IV curve scanning data of the photovoltaic component 10 during the IV curve scanning process, and determines that the photovoltaic component 10 is faulty when the deviation between the IV curve scanning data of the photovoltaic component 10 and the IV curve standard data is greater than the deviation threshold.

[0172] It should be noted that, in the process of fault detection of the photovoltaic module 10, the specific process performed by each module and each unit in the fault detection device can be found in Figure 6 The description of the corresponding parts in the corresponding embodiments will not be repeated here.

[0173] In this embodiment, since the entire fault detection process of the photovoltaic module 10 is completed by the inverter already in the photovoltaic system 1, there is no need to add any detection equipment or systems, nor is there a need to select different detection equipment based on different types of photovoltaic modules. Therefore, it can not only effectively reduce the detection cost, but also effectively cover all photovoltaic systems that require photovoltaic module fault detection, and has strong applicability. In addition, compared with the method of performing fault detection based on multiple IV curve scans, in this embodiment, the photovoltaic module 10 is scanned by the IV curve when there is a deviation impedance greater than the impedance deviation threshold among the two impedance deviations of the photovoltaic module 10. Therefore, the number of IV curve scans can be effectively reduced, thereby effectively reducing the power fluctuation during detection, thereby increasing the power generation of the photovoltaic system 1. Compared with the method of performing fault detection based on the equivalent impedance of the photovoltaic module, the present application determines whether the photovoltaic module is faulty based on both the equivalent impedance of the photovoltaic module and the IV curve scan results, thus effectively improving the accuracy of fault detection.

[0174] See also Figure 11 , Figure 11 This is another schematic diagram of the photovoltaic system provided by this application. Figure 11 As shown, the photovoltaic system 1 includes a photovoltaic module 10, a DC / DC converter, a DC bus (i.e., a positive DC bus BUS+ and a negative DC bus BUS-), and an inverter 12. The two input terminals i11+ and i11- of the DC / DC converter are connected to the photovoltaic module 10. The two output terminals o11+ and o11- of the DC / DC converter, as well as the two input terminals i12+ and i12- of the inverter 12 are all connected in parallel to the DC bus. The three output terminals o121, o122, and o123 of the inverter 12 are connected to the AC grid. Figure 11In the photovoltaic system 1 shown, the photovoltaic power generation equipment 11 provided in this application is a DC / DC converter, which includes a power supply circuit 111 and a controller 112. The two input terminals i111+ and i111- of the power supply circuit 111 are respectively connected to the two input terminals i11+ and i11- of the DC / DC converter, and the two output terminals o111+ and o111- of the power supply circuit 111 are respectively connected to the two output terminals o11+ and o11- of the DC / DC converter.

[0175] When the power supply circuit 111 is a Boost circuit, Figure 11 The photovoltaic system shown can also be equivalent to Figure 12 The photovoltaic system shown in Figure 1 is Figure 12 As shown, Figure 12 The fault detection device of the photovoltaic module 10 shown is Figure 11 The controller 112 shown corresponds to the controller 112. After the photovoltaic system 1 starts operating, the inverter 12 generates an inverter drive signal based on the AC current amplitude and AC voltage phase at the output port of the inverter 12. The inverter drive signal is used to control the conduction duration of the switching tubes of the three-phase bridge arm in the inverter circuit inside the inverter, so that the inverter 12 outputs AC power that meets the requirements of the AC grid to the AC grid.

[0176] and Figure 5 Compared to the DC / DC converter shown in FIG, the DC / DC converter in this embodiment is not directly connected to the power grid, but an inverter 12 is added at the back stage to connect to the AC power grid. The inverter 12 has an independent control system. The function of the back stage inverter 12 is to provide a stable output AC voltage, which has no effect on the front stage DC / DC converter. Therefore, the specific implementation process of the fault detection of the photovoltaic module 10 in this embodiment is the same as that in FIG. Figure 5 and Figure 6 The descriptions in the corresponding embodiments are consistent and will not be repeated here.

[0177] In this embodiment, since the entire fault detection process of the photovoltaic module 10 is completed by the existing DC / DC converter in the photovoltaic system 1, there is no need to add any detection equipment or systems, nor is there a need to select different detection equipment based on different types of photovoltaic modules. Therefore, it can not only effectively reduce the detection cost, but also effectively cover all photovoltaic systems that require photovoltaic module fault detection, and has strong applicability. In addition, compared with the method of fault detection based on multiple IV curve scans, in this embodiment, the photovoltaic module 10 is scanned by the IV curve when there is a deviation impedance greater than the impedance deviation threshold among the two impedance deviations of the photovoltaic module 10. Therefore, the number of IV curve scans can be effectively reduced, thereby effectively reducing the power fluctuation during detection, thereby increasing the power generation of the photovoltaic system 1. Compared with the method of fault detection based on the equivalent impedance of the photovoltaic module, the present application determines whether the photovoltaic module is faulty based on both the equivalent impedance of the photovoltaic module and the IV curve scan results, thus effectively improving the accuracy of fault detection.

[0178] See also Figure 13 , Figure 13 The photovoltaic module fault detection method provided in the present application is applicable to Figure 3 、 Figure 4 、 Figure 6 、 Figure 10 and Figure 12 The photovoltaic module 10 fault detection device in the photovoltaic system 1 is shown. The photovoltaic module fault detection method may include the following steps:

[0179] S101 : Determine an equivalent impedance of the photovoltaic assembly at each measurement frequency based on an output voltage and an output current of the photovoltaic assembly at each measurement frequency of at least one measurement frequency.

[0180] In an optional embodiment, the fault detection device of the photovoltaic assembly 10 obtains the faults of the photovoltaic assembly 10 at n measurement frequencies (ie, ω1, ..., ω n ) in each measurement frequency ω j The output voltage v(ω j ) and output current i(ω j ), and based on the photovoltaic component 10 at each measurement frequency ω in the n measurement frequencies j The output voltage v(ω j ) and output current i(ω j ), calculate the photovoltaic module 10 at each measurement frequency ω j The equivalent impedance Z(ω j )=v(ω j ) / i(ω j ), where n is a positive integer.

[0181] S102: Obtain the impedance deviation of the photovoltaic module at each measurement frequency.

[0182] The impedance deviation of the photovoltaic module at each measurement frequency is the impedance deviation between the equivalent impedance of the photovoltaic module at each measurement frequency and the standard equivalent impedance at each measurement frequency.

[0183] In an optional embodiment, the fault detection device of the photovoltaic assembly 10 calculates the fault of the photovoltaic assembly 10 at each measurement frequency ω j The equivalent impedance Z(ω j ) and at each measurement frequency ω j The standard equivalent impedance Z REF (ω j ), and the impedance deviation between the photovoltaic module 10 and the measured frequency ω is obtained. j Impedance deviation ΔZ(ω j )=|Z(ω j )-Z REF (ω j )|.

[0184] S103 : When the impedance deviation of the photovoltaic assembly at each measurement frequency has an impedance deviation greater than an impedance deviation threshold, perform an IV curve scan on the photovoltaic assembly and obtain IV curve scan data of the photovoltaic assembly.

[0185] In an optional embodiment, the fault detection device of the photovoltaic component 10 performs an IV curve scan on the photovoltaic component and obtains IV curve scanning data of the photovoltaic component when there is an impedance deviation greater than an impedance deviation threshold in the impedance deviation of the photovoltaic component at each measurement frequency.

[0186] In another optional embodiment, the fault detection device of the photovoltaic component 10 performs an IV curve scan on the photovoltaic component and obtains IV curve scanning data of the photovoltaic component when there are m impedance deviations greater than the impedance deviation threshold in the impedance deviations of the photovoltaic component at each measurement frequency and m is greater than a quantity threshold, wherein the quantity threshold is a positive integer.

[0187] S104 , when the deviation between the IV curve scan data of the photovoltaic module and the IV curve standard data is greater than a deviation threshold, determining that the photovoltaic module is faulty.

[0188] In a specific implementation, more operations performed by the fault detection device in the photovoltaic module fault detection method provided in this application can be found in Figure 3 、 Figure 4 、 Figure 6 、 Figure 10 and Figure 12 The implementation method performed by the fault detection device of the photovoltaic assembly 10 in the photovoltaic system 1 is not described in detail here.

[0189] In this embodiment, since the entire fault detection process of the photovoltaic component 10 is completed by the fault detection device of the photovoltaic component 10 already in the photovoltaic system 1, there is no need to add any detection equipment and system, nor is there any need to select different detection equipment according to different types of photovoltaic components. Therefore, it can not only effectively reduce the detection cost, but also effectively cover all photovoltaic systems that require photovoltaic component fault detection, and has strong applicability.

[0190] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A photovoltaic system, characterized in that: The photovoltaic system includes a photovoltaic module and a photovoltaic power generation device, the input end of the photovoltaic power generation device is connected to the photovoltaic module, and the output end of the photovoltaic power generation device is connected to the power grid, wherein: The photovoltaic power generation device is configured to determine the equivalent impedance of the photovoltaic assembly at each of the at least one measurement frequencies based on the output voltage and output current of the photovoltaic assembly at each of the at least one measurement frequencies; Obtaining an impedance deviation of the photovoltaic assembly at each measurement frequency, wherein the impedance deviation of the photovoltaic assembly at each measurement frequency is an impedance deviation between an equivalent impedance of the photovoltaic assembly at each measurement frequency and a standard equivalent impedance at each measurement frequency; When the impedance deviation of the photovoltaic assembly at each measurement frequency is greater than an impedance deviation threshold, performing an IV curve scan on the photovoltaic assembly and acquiring IV curve scan data of the photovoltaic assembly; When a deviation between the IV curve scan data and the IV curve standard data of the photovoltaic component is greater than a deviation threshold, it is determined that the photovoltaic component is faulty.

2. The photovoltaic system according to claim 1, characterized in that: The photovoltaic power generation equipment is also used for: generating a first drive signal according to a first reference voltage and the AC measurement signal of the at least one measurement frequency, and controlling the output voltage of the photovoltaic assembly according to the first drive signal, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid; An output voltage and an output current of the photovoltaic component at each of the at least one measurement frequency under the control of the first driving signal are obtained.

3. The photovoltaic system according to claim 2, characterized in that: The photovoltaic power generation equipment is used for: Superimposing the first reference voltage and the AC measurement signal of the at least one measurement frequency to obtain a second reference voltage; A first modulation wave is generated according to the second reference voltage and the current output voltage of the photovoltaic assembly, and the first driving signal is generated according to the first modulation wave.

4. The photovoltaic system according to claim 2, characterized in that: The photovoltaic power generation equipment is used for: generating a second modulation wave according to the first reference voltage and the current output voltage of the photovoltaic component; The second modulated wave and the AC measurement signal of the at least one measurement frequency are superimposed to obtain a third modulated wave, and the first drive signal is generated according to the third modulated wave.

5. The photovoltaic system according to claim 1, characterized in that: The photovoltaic power generation equipment is also used for: generating a drive signal corresponding to each of the at least one measurement frequency according to a first reference voltage and an AC measurement signal of each of the at least one measurement frequency, and controlling the output voltage of the photovoltaic assembly according to the drive signal corresponding to each of the at least one measurement frequency, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid; An output voltage and an output current of the photovoltaic component at each of the at least one measurement frequency under the control of a driving signal corresponding to each of the at least one measurement frequency are obtained.

6. The photovoltaic system according to claim 5, characterized in that: The photovoltaic power generation equipment is used for: respectively superimposing the first reference voltage and the AC measurement signal of each frequency in the at least one measurement frequency to obtain a third reference voltage corresponding to each measurement frequency in the at least one measurement frequency; A fourth modulation wave corresponding to each measurement frequency is generated according to the current output voltage of the photovoltaic module and the third reference voltage corresponding to each measurement frequency, and a driving signal corresponding to each measurement frequency is generated according to the fourth modulation wave corresponding to each measurement frequency.

7. The photovoltaic system according to claim 5, characterized in that: The photovoltaic power generation equipment is used for: generating a fifth modulation wave according to the first reference voltage and the current output voltage of the photovoltaic component; The fifth modulation wave and the AC measurement signal of each measurement frequency in the at least one measurement frequency are superimposed to obtain a sixth modulation wave corresponding to each measurement frequency, and a drive signal corresponding to each measurement frequency is generated according to the sixth modulation wave corresponding to each measurement frequency.

8. The photovoltaic system according to any one of claims 2 to 7, characterized in that: The photovoltaic power generation equipment is also used for: Determine the current working state of the photovoltaic power generation device, and determine the first reference voltage according to the current working state of the photovoltaic power generation device, the first reference voltage being a reference input voltage when the photovoltaic power generation device is in a power-limited working state, or a reference input voltage when the photovoltaic power generation device is in a non-power-limited working state.

9. The photovoltaic system according to any one of claims 1 to 7, characterized in that: The photovoltaic power generation device is used to perform an IV curve scan on the photovoltaic component when, among the impedance deviations of the photovoltaic component at each measurement frequency, there are m impedance deviations greater than the impedance deviation threshold and the m is greater than a quantity threshold, where the quantity threshold is a positive integer.

10. The photovoltaic system according to any one of claims 1 to 7, wherein the photovoltaic power generation equipment is used for: Compare the descending phase scanning data of the photovoltaic module in the descending phase scanning period with the ascending phase scanning data of the photovoltaic module in the ascending phase scanning period, and output the IV curve scanning data of the photovoltaic module according to the comparison result, wherein, The descending phase scanning period and the ascending phase scanning period constitute an IV curve scanning period of the photovoltaic module.

11. The photovoltaic system according to any one of claims 1 to 7, characterized in that: The photovoltaic power generation equipment is a DC / DC converter, the power grid is a DC power grid, the photovoltaic system further includes a DC bus, and the output end of the DC / DC converter is connected to the DC power grid via the DC bus.

12. The photovoltaic system according to any one of claims 1 to 7, characterized in that: The photovoltaic system also includes an inverter and a DC bus. The photovoltaic power generation equipment is a DC / DC converter, and the power grid is an AC power grid. The output end of the DC / DC converter and the input end of the inverter are connected in parallel to the DC bus, and the output end of the inverter is connected to the AC power grid.

13. The photovoltaic system according to any one of claims 1 to 7, characterized in that: The photovoltaic power generation equipment is an inverter, and the power grid is an AC power grid.

14. A photovoltaic module fault detection method, characterized in that: The photovoltaic assembly is connected to an input end of a photovoltaic power generation device, and an output end of the photovoltaic power generation device is connected to a power grid. The method includes: determining, based on an output voltage and an output current of the photovoltaic assembly at each of the at least one measurement frequency, an equivalent impedance of the photovoltaic assembly at each of the measurement frequencies; Obtaining an impedance deviation of the photovoltaic assembly at each measurement frequency, wherein the impedance deviation of the photovoltaic assembly at each measurement frequency is an impedance deviation between an equivalent impedance of the photovoltaic assembly at each measurement frequency and a standard equivalent impedance at each measurement frequency; When the impedance deviation of the photovoltaic assembly at each measurement frequency is greater than an impedance deviation threshold, performing an IV curve scan on the photovoltaic assembly and acquiring IV curve scan data of the photovoltaic assembly; When a deviation between the IV curve scan data and the IV curve standard data of the photovoltaic component is greater than a deviation threshold, it is determined that the photovoltaic component is faulty.

15. The method according to claim 14, characterized in that The method further comprises: generating a first drive signal according to a first reference voltage and the AC measurement signal of the at least one measurement frequency, and controlling the output voltage of the photovoltaic assembly according to the first drive signal, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid; An output voltage and an output current of the photovoltaic component at each of the at least one measurement frequency under the control of the first driving signal are obtained.

16. The method according to claim 15, characterized in that Generating the first drive signal according to the first reference voltage and the AC measurement signal of the at least one measurement frequency includes: Superimposing the first reference voltage and the AC measurement signal of the at least one measurement frequency to obtain a second reference voltage; A first modulation wave is generated according to the second reference voltage and the current output voltage of the photovoltaic assembly, and the first driving signal is generated according to the first modulation wave.

17. The method according to claim 15, characterized in that Generating the first drive signal according to the first reference voltage and the AC measurement signal of the at least one measurement frequency includes: generating a second modulation wave according to the first reference voltage and the current output voltage of the photovoltaic component; The second modulated wave and the AC measurement signal of the at least one measurement frequency are superimposed to obtain a third modulated wave, and the first drive signal is generated according to the third modulated wave.

18. The method according to claim 14, characterized in that The method further comprises: generating a drive signal corresponding to each of the at least one measurement frequency according to a first reference voltage and an AC measurement signal of each of the at least one measurement frequency, and controlling the output voltage of the photovoltaic assembly according to the drive signal corresponding to each of the at least one measurement frequency, wherein the first reference voltage is a reference input voltage of the photovoltaic power generation device when supplying power to the grid; An output voltage and an output current of the photovoltaic component at each of the at least one measurement frequency under the control of a driving signal corresponding to each of the at least one measurement frequency are obtained.

19. The method according to claim 18, characterized in that Generating a drive signal corresponding to each of the at least one measurement frequency according to the first reference voltage and the AC measurement signal of each of the at least one measurement frequency comprises: respectively superimposing the first reference voltage and the AC measurement signal of each frequency in the at least one measurement frequency to obtain a third reference voltage corresponding to each measurement frequency in the at least one measurement frequency; A fourth modulation wave corresponding to each measurement frequency is generated according to the current output voltage of the photovoltaic module and the third reference voltage corresponding to each measurement frequency, and a driving signal corresponding to each measurement frequency is generated according to the fourth modulation wave corresponding to each measurement frequency.

20. The method according to claim 18, wherein Generating a drive signal corresponding to each of the at least one measurement frequency according to the first reference voltage and the AC measurement signal of each of the at least one measurement frequency comprises: generating a fifth modulation wave according to the first reference voltage and the current output voltage of the photovoltaic component; The fifth modulation wave and the AC measurement signal of each measurement frequency in the at least one measurement frequency are superimposed to obtain a sixth modulation wave corresponding to each measurement frequency, and a drive signal corresponding to each measurement frequency is generated according to the sixth modulation wave corresponding to each measurement frequency.

21. The method according to any one of claims 15 to 20, characterized in that The method further comprises: Determine the current working state of the photovoltaic power generation device, and determine the first reference voltage according to the current working state of the photovoltaic power generation device, the first reference voltage being a reference input voltage when the photovoltaic power generation device is in a power-limited working state, or a reference input voltage when the photovoltaic power generation device is in a non-power-limited working state.

22. The method according to any one of claims 14 to 20, characterized in that: When the impedance deviation of the photovoltaic component at each measurement frequency is greater than an impedance deviation threshold, performing IV curve scanning on the photovoltaic component includes: If, among the impedance deviations of the photovoltaic component at each measurement frequency, there are m impedance deviations greater than the impedance deviation threshold and m is greater than a quantity threshold, IV curve scanning is performed on the photovoltaic component, where the quantity threshold is a positive integer.

23. The method according to any one of claims 14 to 20, wherein obtaining IV curve scanning data of the photovoltaic module comprises: The descending phase scanning data of the photovoltaic component in the descending phase scanning period is compared with the ascending phase scanning data of the photovoltaic component in the ascending phase scanning period, and the IV curve scanning data of the photovoltaic component is output according to the comparison result, wherein the descending phase scanning period and the ascending phase scanning period constitute the IV curve scanning period of the photovoltaic component.

24. A photovoltaic module fault detection device, characterized in that: The device is located in a photovoltaic power generation device, and includes: an equivalent impedance determination module, configured to determine the equivalent impedance of the photovoltaic assembly at each measurement frequency based on the output voltage and output current of the photovoltaic assembly at each measurement frequency of at least one measurement frequency; an impedance deviation acquisition module, configured to acquire an impedance deviation of the photovoltaic assembly at each measurement frequency, wherein the impedance deviation of the photovoltaic assembly at each measurement frequency is an impedance deviation between an equivalent impedance of the photovoltaic assembly at each measurement frequency and a standard equivalent impedance at each measurement frequency; An IV curve acquisition module is configured to perform an IV curve scan on the photovoltaic assembly and acquire IV curve scan data of the photovoltaic assembly when an impedance deviation of the photovoltaic assembly at each measurement frequency is greater than an impedance deviation threshold; The fault determination module is configured to determine that the photovoltaic assembly is faulty when a deviation between the IV curve scan data and the IV curve standard data of the photovoltaic assembly is greater than a deviation threshold.

25. A photovoltaic power generation device, characterized in that: The input end of the photovoltaic power generation device is connected to the photovoltaic module, and the output end of the photovoltaic power generation device is connected to the power grid. The photovoltaic power generation device includes a controller and a power supply circuit, wherein: The input end of the power supply circuit is connected to the input end of the photovoltaic power generation device, and the output end of the power supply circuit is connected to the output end of the photovoltaic power generation device. The power supply circuit is used to convert the input end voltage of the photovoltaic power generation device into the output end voltage of the photovoltaic power generation device; The controller is configured to determine the equivalent impedance of the photovoltaic component at each measurement frequency based on the output voltage and output current of each measurement frequency of the photovoltaic component; obtain the impedance deviation of the photovoltaic component at each measurement frequency, wherein the impedance deviation of the photovoltaic component at each measurement frequency is the impedance deviation between the equivalent impedance of the photovoltaic component at each measurement frequency and the standard equivalent impedance at each measurement frequency; perform an IV curve scan on the photovoltaic component and obtain IV curve scan data of the photovoltaic component when an impedance deviation greater than an impedance deviation threshold exists in the impedance deviation of the photovoltaic component at each measurement frequency; and determine that the photovoltaic component is faulty when the deviation between the IV curve scan data of the photovoltaic component and the IV curve standard data is greater than the deviation threshold.

Images