Power conversion device and photovoltaic module detection method

Abstract

The invention provides a power conversion device and a detection method of a photovoltaic module, and is applied to the technical field of photovoltaic power generation. Wherein the power conversion device performs impedance scanning on the photovoltaic module through zero bias voltage, first bias voltage corresponding to a parallel resistance peak value of the photovoltaic module and second bias voltage corresponding to a series resistance peak value of the photovoltaic module, and impedance characteristic parameters of the photovoltaic module at the specific three bias voltages are obtained. And then, the power conversion device outputs the fault type of the photovoltaic module according to a comparison result of the obtained impedance characteristic parameter and a preset impedance characteristic parameter. Based on this, the fault of the photovoltaic module can be detected through the original power conversion device of the photovoltaic power generation system, and the fault type of the photovoltaic module is output only through the comparison result of the impedance characteristic parameters at the three bias voltages and the preset impedance characteristic parameters during detection. And the cost is reduced while the fault detection efficiency of the photovoltaic module is improved.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a power conversion device and a photovoltaic component detection method. Background Art

[0002] In recent years, with the development of photovoltaic power generation technology, the installed capacity of photovoltaic power generation systems has continued to rise, and ensuring the long-term reliable operation of photovoltaic power generation systems has also become a focus of industry attention. Among them, photovoltaic modules in photovoltaic power generation systems may have various faults during long-term service. In order to ensure more reliable operation of photovoltaic power generation systems, it is necessary to detect photovoltaic module faults in a timely manner so as to repair the faults in a timely manner. However, the existing detection scheme requires the use of additional equipment to detect photovoltaic module faults and the detection efficiency is low. Therefore, it is necessary to provide a solution to solve the above problems. Summary of the invention

[0003] The embodiments of the present application provide a power conversion device and a photovoltaic module detection method, so as to improve the fault detection efficiency of the photovoltaic module and reduce the cost at the same time.

[0004] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions.

[0005] In a first aspect, a power conversion device is provided, wherein a DC input terminal of the power conversion device is used to connect a photovoltaic module. When the output power of the photovoltaic module is less than a preset output power, the power conversion device can perform an impedance scan on the photovoltaic module through a plurality of bias voltages to obtain impedance characteristic parameters of the photovoltaic module at the plurality of bias voltages. Then, the power conversion device outputs the fault type of the photovoltaic module according to the comparison result between the impedance characteristic parameters and the preset impedance characteristic parameters. The impedance characteristic parameters include the parallel resistance value, the series resistance value and the fitting parameter value of the constant phase element of the photovoltaic module at the plurality of bias voltages. The plurality of bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic module and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic module.

[0006] In the above manner, the power conversion device can perform impedance scanning on the photovoltaic module through multiple bias voltages such as zero bias voltage, the first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic module, and the second bias voltage corresponding to the peak value of the series resistance of the photovoltaic module to obtain the impedance characteristic parameters of the photovoltaic module at multiple bias voltages, and output the fault type of the photovoltaic module according to the comparison result between the above impedance characteristic parameters and the preset impedance characteristic parameters. Based on this, there is no need to add additional equipment when performing fault detection on the photovoltaic module, and the fault type of the photovoltaic module can be detected by performing impedance scanning with the above three bias voltages, which improves the fault detection efficiency of the photovoltaic module while reducing costs.

[0007] In one embodiment, the preset impedance characteristic parameter includes a first preset parallel resistance value. When the photovoltaic component is subjected to impedance scanning by a zero bias voltage, the impedance characteristic parameter includes the first parallel resistance value. The power conversion device is used to output the fault type of the photovoltaic component as a diode open circuit fault when the first parallel resistance value is greater than the first preset parallel resistance value.

[0008] At zero bias voltage, the parallel resistance value when the diode in the photovoltaic module has an open circuit fault is greater than the first preset parallel resistance value when the photovoltaic module is normal. Therefore, the diode open circuit fault of the photovoltaic module can be identified by the above method.

[0009] In one embodiment, the power conversion device is further used to output the fault type of the photovoltaic component as a diode open circuit fault when the first parallel resistance value is greater than the first preset parallel resistance value and the difference between the first parallel resistance value and the first preset parallel resistance value is greater than a first threshold value. The above-mentioned first parallel resistance value is greater than the first preset parallel resistance value, which may be caused by the normal attenuation of the photovoltaic device. Therefore, the diode open circuit fault of the photovoltaic component can be more accurately identified in the above manner. Based on this, the diode open circuit fault of the photovoltaic component can be identified when the difference between the first parallel resistance value and the first preset parallel resistance value is large, thereby further improving the accuracy of fault identification.

[0010] In one implementation, the first threshold is greater than or equal to 10% of the first preset parallel resistance value.

[0011] Under normal use of the photovoltaic module, the first parallel resistance value of the photovoltaic module at zero bias voltage will be greater than the first preset parallel resistance value due to normal power attenuation. However, when the photovoltaic module has a diode short circuit fault, the parallel resistance value at zero bias voltage is significantly greater than the parallel resistance value under normal power attenuation. Therefore, the above method can avoid the misidentification of the diode short circuit fault.

[0012] In one embodiment, the preset impedance characteristic parameter also includes a preset fitting parameter value of a constant phase element. When the photovoltaic module is subjected to impedance scanning by a zero bias voltage, the impedance characteristic parameter also includes a fitting parameter value of a constant phase element of the photovoltaic module. The power conversion device is also used to output that the fault type of the photovoltaic module is a potential induced degradation fault when the first parallel resistance value is less than the first preset parallel resistance value and the fitting parameter value of the constant phase element is less than the preset fitting parameter value of the constant phase element.

[0013] The fitting parameter value of the constant phase element of a photovoltaic module is usually characterized by the non-uniformity of the photovoltaic module. The closer the fitting parameter value of the constant phase element of the photovoltaic module is to 1, the better the uniformity of the photovoltaic module. Among them, the fitting parameter value of the constant phase element will change slightly with the normal attenuation of the photovoltaic device. However, when there is a potential induced attenuation fault in the photovoltaic module, the fitting parameter value of the constant phase element will change significantly. Therefore, the preset fitting parameter value of the constant phase element under normal circumstances can be used as a reference value to improve the accuracy of potential induced attenuation fault identification.

[0014] In one embodiment, the power conversion device is further used for: when the first parallel resistance value is less than the first preset parallel resistance value, the difference between the first parallel resistance value and the first preset parallel resistance value is greater than a second threshold, and the fitting parameter value of the constant phase element is less than the preset fitting parameter value of the constant phase element, the fault type of the output photovoltaic component is a potential induced degradation fault.

[0015] During normal use of the photovoltaic module, the first parallel resistance value may also be less than the first preset parallel resistance value. However, when the photovoltaic module has a potential induced degradation fault, the difference between the first parallel resistance value and the first preset parallel resistance value is significantly greater than the difference under normal circumstances. Therefore, the above method can further improve the accuracy of fault identification.

[0016] In one implementation, the second threshold is greater than or equal to 10% of the first preset parallel resistance value.

[0017] When the photovoltaic module is in normal use, the first parallel resistance value at the zero bias voltage may still be slightly smaller than the first preset parallel resistance value. However, when the photovoltaic module has a potential induced degradation fault, the reduction value of the parallel resistance value of the photovoltaic module at the zero bias voltage is significantly greater than the reduction value of the parallel resistance value in normal use. Therefore, the above method can avoid the misidentification of the potential induced degradation fault.

[0018] In one embodiment, the preset impedance characteristic parameter also includes a first preset series resistance value, a second preset parallel resistance value, and a second preset series resistance value. When the photovoltaic component is impedance scanned by a zero bias voltage, the impedance characteristic parameter also includes the first series resistance value. When the photovoltaic component is impedance scanned by a first bias voltage, the impedance characteristic parameter also includes the second parallel resistance value and the second series resistance value. When the photovoltaic component is impedance scanned by a second bias voltage, the impedance characteristic parameter also includes the third series resistance value. On this basis, the power conversion device is also used for: when the first parallel resistance value is less than the first preset parallel resistance value, the first series resistance value is greater than the first preset series resistance value, the fitting parameter value of the constant phase element is greater than the preset fitting parameter value of the constant phase element, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is less than or equal to the first series resistance value or the second series resistance value, the fault type of the output photovoltaic component is a diode short circuit fault.

[0019] When a photovoltaic module has a diode short circuit fault, the impedance characteristic parameters of the photovoltaic module at zero bias voltage, first bias voltage and second bias voltage will have specific changes compared with the corresponding preset impedance characteristic parameters. Based on this, the diode short circuit fault of the photovoltaic module can be detected according to the comparison results of the impedance characteristic parameters at three bias voltages with the corresponding preset impedance characteristic parameters.

[0020] In one embodiment, the power conversion device is also used to output the fault type of the photovoltaic component as a battery crack fault or a battery corrosion fault when the first parallel resistance value is less than a first preset parallel resistance value, the fitting parameter value of the constant phase element is greater than the preset fitting parameter value of the constant phase element, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is greater than the first series resistance value and the second series resistance value.

[0021] When a photovoltaic module has a cell crack fault or a cell corrosion fault, the impedance characteristic parameters of the photovoltaic module at zero bias voltage, the first bias voltage, and the second bias voltage will also have specific changes compared with the corresponding preset impedance characteristic parameters. Based on this, the cell crack fault or cell corrosion fault of the photovoltaic module can be detected according to the comparison results of the impedance characteristic parameters at the three bias voltages with the corresponding preset impedance characteristic parameters.

[0022] In a second aspect, a detection method for a photovoltaic component is provided, the method comprising: when the output power of the photovoltaic component is less than the preset output power, the power conversion device performs impedance scanning on the photovoltaic component through multiple bias voltages to obtain impedance characteristic parameters of the photovoltaic component at multiple bias voltages. The power conversion device outputs the fault type of the photovoltaic component according to the comparison result between the impedance characteristic parameters and the preset impedance characteristic parameters. The above-mentioned impedance characteristic parameters include the parallel resistance value, the series resistance value and the fitting parameter value of the constant phase element of the photovoltaic component at multiple bias voltages. The above-mentioned multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic component, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic component.

[0023] Regarding the technical principles and beneficial effects of the above-mentioned second aspect, reference may be made to the relevant description of the above-mentioned first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a photovoltaic power generation system provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of the structure of another photovoltaic power generation system provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of the structure of another photovoltaic power generation system provided in an embodiment of the present application;

[0027] Figure 4 A distribution curve diagram of a parallel resistance value of a photovoltaic module according to an embodiment of the present application as a function of a bias voltage;

[0028] Figure 5 A distribution curve diagram of the series resistance value of a photovoltaic module according to an embodiment of the present application as a function of the bias voltage;

[0029] Figure 6 A schematic diagram of a process flow of a photovoltaic module detection method provided in an embodiment of the present application;

[0030] Figure 7 A schematic flow chart of another photovoltaic module detection method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0032] In the embodiments of the present application, "plurality" refers to two or more. In addition, in the embodiments of the present application, words such as "first" and "second" do not limit the quantity and order. "And / or" describes the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural.

[0033] It should be noted that in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way. The terms "coupling" and "connection" involved in the embodiments of the present application should be understood in a broad sense. For example, they may refer to a physical direct connection, or they may refer to an indirect connection achieved through an electronic device, such as a connection achieved through a resistor, inductor, capacitor or other electronic device.

[0034] The power conversion device provided in the embodiment of the present application can be applied to various application fields such as the field of new energy intelligent microgrid, power transmission and distribution, new energy (such as photovoltaic grid-connected field), photovoltaic power generation, energy storage power generation, etc. Among them, the power conversion device provided in the embodiment of the present application can be an inverter (including string photovoltaic inverters and distributed photovoltaic inverters), a DC-DC (DC / DC) converter (such as a photovoltaic optimizer), etc., which is applicable to different application scenarios, such as photovoltaic power supply scenarios, photovoltaic storage power supply scenarios, etc. The photovoltaic power supply scenario is used as an example for explanation below.

[0035] Photovoltaic generation system (PGS) is a power generation system that directly converts solar radiation energy into electrical energy by utilizing the photovoltaic effect of semiconductor materials. Figure 1 As shown, Figure 1 It is a structural schematic diagram of a photovoltaic power generation system 100 provided in an embodiment of the present application. In the photovoltaic power supply application scenario, the power conversion device 110 in the photovoltaic power generation system 100 provided in an embodiment of the present application may include an inverter 111. Among them, the input end of the inverter 111 is used to connect the photovoltaic module 120. The output end of the inverter 111 is used to connect the AC power grid 130 and / or the AC load 140. The inverter 111 can be controlled by a control circuit. The inverter 111 is used to invert the DC power of the photovoltaic module into AC power under the control of the control circuit, thereby realizing power supply to the AC power grid 130 or the AC load 140 (such as household appliances).

[0036] like Figure 2 As shown, Figure 2 It is a structural schematic diagram of another photovoltaic power generation system 100 provided in an embodiment of the present application. In the photovoltaic power supply application scenario, the power conversion device 110 in the photovoltaic power generation system 100 provided in an embodiment of the present application may include a DC / DC converter 112. Among them, the input end of the DC / DC converter 112 is connected to the photovoltaic component 120, and the output end of the DC / DC converter 112 is connected to the DC power grid 150 and / or the DC load 160. The DC / DC converter 112 can be controlled by a control circuit. The DC / DC converter 112 is used to convert the DC power generated by the photovoltaic component 120 connected to its input end into a DC power with a voltage of a preset value under the control of the control circuit, thereby realizing the power supply to the DC power grid 150 and / or the DC load 160.

[0037] like Figure 3 As shown, Figure 3 It is a structural schematic diagram of another photovoltaic power generation system 100 provided in an embodiment of the present application. In the photovoltaic power supply application scenario, the power conversion device 110 in the photovoltaic power generation system 100 provided in an embodiment of the present application may include a DC / DC converter 112 and an inverter 111. Among them, the input end of the DC / DC converter 112 is connected to the photovoltaic component 120, and the output end of the DC / DC converter 112 is connected to the AC power grid 130 and / or the AC load 140 through the inverter 111. The DC / DC converter 112 and the inverter 111 can be controlled by a control circuit. After the photovoltaic power generation system 100 composed of the DC / DC converter 112 and the inverter 111 starts to operate, the control circuit can control the DC / DC converter 112 to perform maximum power point tracking (maximum power point tracking, MPPT) on the photovoltaic component 120 connected to its input end so that the output power of the photovoltaic component 120 reaches the maximum. At the same time, the DC / DC converter 112 converts the DC power generated by the photovoltaic module 120 connected to its input end into DC power with a preset voltage, and outputs the DC power to the inverter 111. Under the control of the control circuit 113, the inverter 111 inverts the DC power output by the DC / DC converter 112 into AC power, thereby realizing power supply to the AC grid 130 or the AC load 140 (such as household appliances).

[0038] In some related technologies, in order to Figures 1 to 3 In order to detect the fault of the photovoltaic module 120 in the photovoltaic power generation system 100, the operation and maintenance personnel can be arranged to carry the detection equipment to the photovoltaic power station site to detect the photovoltaic module 120. However, the above scheme has low detection efficiency, poor timeliness, large errors, and high costs. At the same time, when the photovoltaic module 120 is detected, the module and the power generation system need to be disconnected to ensure the arrangement of personnel, which will affect the power generation of the system.

[0039] In some related technologies, the electroluminescence (EL) principle of crystalline silicon can be used to input energy into the photovoltaic module 120 so that the photovoltaic module 120 emits light outward. This process is exactly the opposite of using the photovoltaic module 120 to generate electricity, so it is called energy feedback. In this process, a high-resolution infrared camera is used to capture a near-infrared image of the photovoltaic module 120, and the defects of the photovoltaic module 120 are determined based on whether the near-infrared image of the light emitted by the photovoltaic module 120 is normal. However, the above solution requires additional image acquisition and processing systems, such as cameras or drones, which increases the cost of the detection system.

[0040] In some related technologies, the detection equipment can be controlled to scan the working point of the photovoltaic module 120 from open circuit to short circuit, record the current-voltage curve of the photovoltaic module 120 at the working point and evaluate it. However, this solution is only effective for faults that have caused the power generation of the photovoltaic module 120 to be distorted. Other faults still need to be detected by other solutions, which reduces the efficiency of fault detection.

[0041] In order to solve the above problems, the embodiment of the present application improves the power conversion device 110. In the process of the photovoltaic power generation system 100 supplying power to the electrical equipment, when the output power of the photovoltaic module 120 is less than the preset output power, the power conversion device 110 performs impedance scanning on the photovoltaic module 120 through multiple bias voltages to obtain the impedance characteristic parameters of the photovoltaic module 120 at multiple bias voltages. Then, the power conversion device 110 outputs the fault type of the photovoltaic module 120 according to the comparison result between the impedance characteristic parameters and the preset impedance characteristic parameters. In the above impedance characteristic parameters, the parallel resistance value Rsh, the series resistance value Rs and the fitting parameter value CPE-P of the constant phase element of the photovoltaic module 120 at the above multiple bias voltages are included. The above preset impedance characteristic parameters include one or more of the preset parallel resistance value, the preset series resistance value and the preset fitting parameter value. The above multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic module 120, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic module 120.

[0042] The parallel resistance value Rsh of the photovoltaic module 120 mainly comes from the design and manufacturing defects of the photovoltaic module 120, and the parallel resistance value Rsh will affect the leakage current of the photovoltaic module 120, thereby affecting the photovoltaic power. The series resistance value Rs of the photovoltaic module 120 mainly comes from the body resistance of the semiconductor material and the contact resistance between the metal and the semiconductor material, and the series resistance value Rs will affect the fill factor (FF). The fitting parameter value CPE-P of the constant phase element of the photovoltaic module 120 is usually characterized by non-uniformity. The closer the CPE-P is to 1, the better the uniformity of the component. Therefore, the embodiment of the present application uses the impedance characteristic parameters such as the parallel resistance value Rsh, the series resistance value Rs and the fitting parameter value CPE-P of the constant phase element of the photovoltaic module 120 as the basis for fault detection, and can detect the corresponding fault problems in a targeted manner.

[0043] Among them, the comparison results of the impedance characteristic parameters of the photovoltaic module at zero bias voltage, the first bias voltage and the second bias voltage with the preset impedance characteristic parameters can be used to detect different fault types. For example, the comparison result of the parallel resistance value of the photovoltaic module at zero bias voltage with the corresponding preset parallel resistance value can be used to detect the diode open circuit fault of the photovoltaic module. The comparison result of the parallel resistance value of the photovoltaic module at zero bias voltage with the corresponding preset parallel resistance value, and the comparison result of the fitting parameter value CPE-P of the constant phase element with the preset fitting parameter value can be used to detect the potential induced attenuation fault of the photovoltaic module. The comparison results of the parallel resistance value and the series resistance value of the photovoltaic module at zero bias voltage and the first bias voltage with the corresponding preset parallel resistance value and series resistance value, the comparison result of the fitting parameter value CPE-P of the constant phase element of the photovoltaic module at zero bias voltage with the preset fitting parameter value, and the comparison result of the series resistance value of the photovoltaic module at the third bias voltage with the corresponding preset series resistance value can be combined to detect the diode short circuit fault of the photovoltaic module and the battery crack fault or battery corrosion fault.

[0044] Through the above method, when the output power of the photovoltaic component 120 is less than the preset output power, for example, the photovoltaic component 120 is in weak light or dark conditions, fault type detection is implemented according to the impedance characteristic parameters of the photovoltaic component 120, without adding any equipment and system, and without selecting different detection equipment according to different types of photovoltaic components 120. Therefore, it can not only effectively reduce the detection cost and improve the fault detection efficiency of the photovoltaic component 120, but also effectively cover various types of photovoltaic power generation systems, and has strong applicability.

[0045] In one embodiment, the above-mentioned multiple bias voltages can be used to determine the impedance scan of the initial state of the normal photovoltaic component 120 when the output power is less than the preset output power threshold. Wherein, when the output power of the photovoltaic component 120 is less than the preset output power threshold, the power conversion device 110 sets the impedance scanning frequency to multiple frequencies in sequence according to the preset bias voltage and the preset disturbance voltage, and sequentially generates multiple AC signals with different frequencies superimposed on the preset bias voltage at the input end of the power conversion device 110 to perform impedance scanning on the photovoltaic component 120, thereby obtaining multiple equivalent impedance values ​​of the photovoltaic component 120 at multiple frequencies corresponding to the multiple AC signals, and the above-mentioned multiple frequencies correspond to the above-mentioned multiple equivalent impedance values ​​one by one. Wherein, the above-mentioned multiple frequencies can be any multiple frequencies in the high frequency range of 100000 Hz to the low frequency range of 0.1 Hz.

[0046] Exemplarily, the power conversion device 110 can scan the impedance scanning frequency from 100000 Hz in the high frequency area to 0.1 Hz in the low frequency area according to the preset bias voltage and the preset disturbance voltage, and perform impedance scanning according to a logarithmic curve at 10 points every 10 times the frequency to obtain multiple equivalent impedance values ​​of the preset disturbance voltage at multiple frequencies. Among them, the above-mentioned preset bias voltage can be any value greater than or equal to 0 and less than or equal to the maximum bias voltage Voc of the photovoltaic component 120. The above-mentioned preset disturbance voltage represents the voltage amplitude of the AC measurement signal superimposed on the preset bias voltage. Among them, the above-mentioned preset disturbance voltage is set to between 1mV and 100mV. After the impedance scan, its impedance spectrum, i.e., the Nyquist diagram, will be obtained. The impedance spectrum can be fitted and analyzed using the relevant algorithm to extract the required parallel resistance value Rsh, series resistance value Rs and fitting parameter value CPE-P of the constant phase element of the photovoltaic component 120.

[0047] In one embodiment, after obtaining multiple equivalent impedance values ​​of the photovoltaic component 120 at multiple frequencies, the power conversion device 110 determines the parallel resistance value Rsh and the series resistance value Rs of the photovoltaic component 120 based on the multiple equivalent impedance values ​​of the photovoltaic component 120 at multiple frequencies. Exemplarily, when the number of the multiple equivalent impedance values ​​of the photovoltaic component 120 is 2, the power conversion device 110 determines the parallel resistance value Rsh and the series resistance value Rs of the photovoltaic component 120 based on the multiple equivalent impedance values ​​of the photovoltaic component 120 at the frequency ω 1 The equivalent impedance value Z(ω 1 )=Z Re1 +i*Z Im1 , and at frequency ω 2 The equivalent impedance value Z(ω 2 )=Z Re2 +i*Z Im2The parallel resistance value Rsh and the series resistance value Rs of the photovoltaic assembly 120 are calculated. Wherein, i represents the output current of the photovoltaic assembly 120, and the output current can be detected by the sampling circuit and sent to the control circuit in the power conversion device 110. The parallel resistance value Rsh and the series resistance value Rs of the photovoltaic assembly 120 can be calculated by the following equations:

[0048]

[0049] In the above formula, Rs is the series resistance value of the photovoltaic module 120, Rsh is the parallel resistance value of the photovoltaic module 120, and Z Re1 is the equivalent impedance value Z(ω 1 ), Z Im1 is the equivalent impedance value Z(ω 1 ), Z Re2 is the equivalent impedance value Z(ω 2 ), Z Im2 is the equivalent impedance value Z(ω 2 )’s imaginary part.

[0050] The above equations can be used to obtain the distribution curve of the parallel resistance value Rsh of the normal photovoltaic module 120 as the bias voltage changes, and the distribution curve of the series resistance value Rs of the photovoltaic module 120 as the bias voltage changes. The distribution curve of the parallel resistance value Rsh of the photovoltaic module 120 as the bias voltage changes is as follows: Figure 4 As shown, the distribution curve of the series resistance value Rs of the photovoltaic module 120 as the bias voltage changes is as follows Figure 5 As shown. Figure 4 It can be seen that the bias voltage changes from V 0 (i.e. 0V) rises to V 1 During the process, the parallel resistance value Rsh of the photovoltaic module gradually increases and when the bias voltage is V 1 The bias voltage is increased from V 1 In the process of increasing to the maximum bias voltage Voc, the parallel resistance value Rsh of the photovoltaic module 120 gradually decreases. Figure 5 It can be seen that the bias voltage changes from V 0 Rising to V 2 During the process, the series resistance value Rs of the photovoltaic module 120 gradually increases and increases at V 2 The bias voltage is increased from V 2 In the process of increasing to the maximum bias voltage Voc, the series resistance Rs of the photovoltaic module 120 gradually decreases. Based on the above-mentioned change characteristics, the embodiment of the present application sets V 0 、V 1 and V 2 Three bias voltages are used as the bias voltages for impedance scanning. 0 is zero bias voltage, V1 is the first bias voltage, V 2 is the second bias voltage.

[0051] In one embodiment, in order to improve the accuracy of the parallel resistance value Rsh and the series resistance value Rs of the photovoltaic component 120, the number of equivalent impedance values ​​of the photovoltaic component 120 can be increased. When the number of equivalent impedance values ​​of the photovoltaic component 120 is greater than 2, the multiple equivalent impedance values ​​of the photovoltaic component 120 can be divided into multiple groups of equivalent impedance values, each group of equivalent impedance values ​​includes 2 equivalent impedance values, and the equivalent impedance values ​​contained in different groups of equivalent impedance values ​​are different. The power conversion device 110 brings each group of equivalent impedance values ​​into the above equation group to calculate a parallel resistance value Rsh and a series resistance value Rs of the photovoltaic component 120. In the above manner, multiple parallel resistance values ​​and series resistance values ​​of the photovoltaic component 120 can be obtained. Among them, the power conversion device 110 determines the parallel resistance value with the smallest deviation value between the standard deviation of the multiple parallel resistance values ​​among the multiple parallel resistance values ​​as the parallel resistance value of the photovoltaic component 120. The power conversion device 110 determines the series resistance value having the smallest deviation from the standard deviation of the series resistance values ​​among the multiple series resistance values ​​as the series resistance value of the photovoltaic module 120 .

[0052] Based on this, the accuracy of the parallel resistance value and the series resistance value of the photovoltaic assembly 120 can be improved, thereby improving the accuracy of the fault type detection of the power conversion device 110.

[0053] In one embodiment, the power conversion device 110 is based on the photovoltaic component 120 at a frequency ω 1 The equivalent impedance value Z(ω 1 ) and frequency ω 2 The equivalent impedance value Z(ω 2 ), the series resistance value Rs, and the parallel resistance value Rsh are used to calculate the fitting parameter value of the constant phase element of the photovoltaic component 120. The fitting parameter value of the constant phase element of the photovoltaic component 120 can be calculated by the following equation group:

[0054]

[0055] In the above formula, CPE-P is a fitting parameter value of the constant phase element CPE in the photovoltaic module 120. CPE-T is another non-critical parameter of the constant phase element CPE in the photovoltaic module 120.

[0056] Further, in order to improve the accuracy of the fitting parameter value CPE-P of the constant phase element of the photovoltaic assembly 120, the number of equivalent impedance values ​​of the photovoltaic assembly 120 may be increased. Here, the specific implementation method of the power conversion device 110 improving the accuracy of the fitting parameter value CPE-P of the constant phase element of the photovoltaic assembly 120 by increasing the number of equivalent impedance values ​​of the photovoltaic assembly 120 can refer to the description of the embodiment of the power conversion device 110 improving the accuracy of the parallel resistance value of the photovoltaic assembly 120, which will not be repeated here.

[0057] In one embodiment, the power conversion device 110 is provided with a zero bias voltage V 0 When the photovoltaic module 120 is subjected to impedance scanning, the impedance characteristic parameters include the first parallel resistance value, the first series resistance value, and the fitting parameter value CPE-P of the constant phase element (CPE) of the photovoltaic module 120. 1 When the photovoltaic module 120 is subjected to impedance scanning, the impedance characteristic parameter also includes the second parallel resistance value and the second series resistance value. 2 When the photovoltaic module 120 is subjected to impedance scanning, the impedance characteristic parameters also include a third series resistance value. The above-mentioned preset impedance characteristic parameters include a first preset parallel resistance value, a first preset series resistance value, a second preset parallel resistance value, a second preset series resistance value and a preset fitting parameter value of a constant phase element.

[0058] In one embodiment, when the output power of the photovoltaic module 120 is less than the preset output power, the power conversion device 110 can firstly 0 The photovoltaic assembly 120 is subjected to an impedance scan to obtain a first parallel resistance value, a first series resistance value, and a fitting parameter value CPE-P of the constant phase element of the photovoltaic assembly 120. Wherein, when the first parallel resistance value is greater than the first preset parallel resistance value, the fault type of the output photovoltaic assembly 120 is a diode open circuit fault. When the first parallel resistance value is less than the first preset parallel resistance value and the fitting parameter value CPE-P of the constant phase element is less than the preset fitting parameter value, the fault type of the output photovoltaic assembly 120 is a potential induced degradation fault.

[0059] In one embodiment, when the photovoltaic component 120 has a diode open circuit fault or a potential induced decay fault, the power conversion device 110 outputs a corresponding fault type and the power conversion device 110 does not need to be at the first bias voltage V 1 and the second bias voltage V 2 The impedance scan is performed on the photovoltaic assembly 120. Based on this, the time for fault detection can be reduced.

[0060] In one embodiment, considering that during normal use, the photovoltaic module may also have a zero bias voltage V due to normal power attenuation. 0 The first parallel resistance value at is greater than the first preset parallel resistance value. Based on this, in order to improve the accuracy of fault identification and avoid misidentification of diode open circuit faults. When the first parallel resistance value of the power conversion device 110 is greater than the first preset parallel resistance value and the difference between the first parallel resistance value and the first preset parallel resistance value is greater than the first threshold value, the fault type of the output photovoltaic component 120 is a diode open circuit fault. The first threshold value is greater than or equal to 10% of the first preset parallel resistance value.

[0061] Exemplarily, when the resistance value of the first preset parallel resistance value is 5000Ω, when the first parallel resistance value of the power conversion device 110 is greater than 5000Ω and the first parallel resistance value is greater than 5500Ω, the fault type of the output photovoltaic component 120 is a diode open circuit fault.

[0062] Of course, the above-mentioned first threshold is only an example provided in the embodiment of the present application. In the specific embodiment, the above-mentioned first threshold can be adjusted according to actual conditions.

[0063] In addition, during normal use, the photovoltaic module may also appear at zero bias voltage V 0 The first parallel resistance value at is less than the first preset parallel resistance value and the fitting parameter value of the constant phase element is less than the preset fitting parameter value of the constant phase element. Based on this, in order to improve the accuracy of fault identification and avoid misidentification of potential induced attenuation faults. In the case where the first parallel resistance value of the power conversion device 110 is less than the first preset parallel resistance value, the difference between the first parallel resistance value and the first preset parallel resistance value is greater than the second threshold value, and the fitting parameter value CPE-P of the constant phase element is less than the preset fitting parameter value of the constant phase element, the fault type of the output photovoltaic component 120 is a potential induced attenuation fault. Among them, the second threshold value is greater than or equal to 10% of the first preset parallel resistance value.

[0064] Exemplarily, when the resistance value of the first preset parallel resistance value is 5000Ω and the second threshold value is greater than 500Ω, the power conversion device 110 outputs the photovoltaic component 120 and the fault type is a potential induced degradation fault when the first parallel resistance value is less than 4500Ω and the fitting parameter value CPE-P of the constant phase element is less than the preset fitting parameter value (for example, 0.96).

[0065] Of course, the above second threshold is only an example provided in the embodiment of the present application. In the specific embodiment, the above second threshold can be adjusted according to actual conditions.

[0066] In one embodiment, when the power conversion device 110 passes the zero bias voltage V 0 After the photovoltaic module 120 is subjected to impedance scanning, the zero bias voltage V 0 The comparison result of the impedance characteristic parameter under the condition of V1 and the preset impedance characteristic parameter determines that the photovoltaic component 120 does not have a diode open circuit fault or a potential induced decay fault, then the power conversion device 110 can choose to pass the first bias voltage V 1 and the second bias voltage V 2 Continue to perform impedance scanning on the photovoltaic module 120, and according to the first bias voltage V 1 and the second bias voltage V 2 The comparison result of the impedance characteristic parameters under the condition and the preset impedance characteristic parameters is used to judge the photovoltaic module diode short circuit fault, battery crack fault or battery corrosion fault.

[0067] When a diode short circuit fault occurs in the photovoltaic module 120, the photovoltaic module is at zero bias voltage V 0 The parallel resistance value under the first bias voltage will decrease, the series resistance value will increase, and the fitting parameter value CPE-P of the constant phase element will be less than the preset fitting parameter value. In addition, the series resistance value of the photovoltaic module under the first bias voltage will increase, and the parallel resistance value will decrease. The series resistance value of the photovoltaic module under the second bias voltage will be less than the zero bias voltage V 0 Or the series resistance value under the first bias voltage. Therefore, the power conversion device 110 can detect the diode short circuit fault of the photovoltaic component 120 according to the change of the above parameters under the three bias voltages.

[0068] In one embodiment, when the first parallel resistance value of the power conversion device 110 is less than the first preset parallel resistance value, the first series resistance value is greater than the first preset series resistance value, the fitting parameter value CPE-P of the constant phase element is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is less than or equal to the first series resistance value or the second series resistance value, the fault type of the output photovoltaic component 120 is a diode short circuit fault.

[0069] The first preset parallel resistance value and the first preset series resistance value are zero bias voltage V 0 The parallel resistance and series resistance of the photovoltaic module are normal. The above preset fitting parameter value is zero bias voltage V 0 The second preset series resistance value and the second preset parallel resistance value are the series resistance value and the parallel resistance value when the photovoltaic component is normal under the first bias voltage.

[0070] In addition, when the photovoltaic module 120 has a cell crack fault or a cell corrosion fault, the photovoltaic module is at a zero bias voltage V 0 The parallel resistance value under the first bias voltage will decrease, and the fitting parameter value CPE-P of the constant phase element will be greater than the preset fitting parameter value. In addition, the series resistance value of the photovoltaic module under the first bias voltage will increase, and the parallel resistance value will decrease. The series resistance value of the photovoltaic module under the second bias voltage will be greater than the zero bias voltage V 0 Therefore, the power conversion device 110 can also detect the cell crack fault or cell corrosion fault of the photovoltaic module 120 according to the change of the above parameters at the three bias voltages.

[0071] In one embodiment, when the first parallel resistance value of the power conversion device 110 is less than the first preset parallel resistance value, the fitting parameter value CPE-P of the constant phase element is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is greater than the first series resistance value and the second series resistance value, the fault type of the output photovoltaic component 120 is a battery crack fault or a battery corrosion fault.

[0072] Further, in one embodiment, if Figure 6 As shown, the embodiment of the present application also provides a detection method for a photovoltaic module 120. The detection method for a photovoltaic module 120 provided in the embodiment of the present application is applicable to Figures 1 to 3 Any type of power conversion device 110.

[0073] S601: When the output power of the photovoltaic module is less than a preset output power, impedance scanning is performed on the photovoltaic module using a plurality of bias voltages to obtain impedance characteristic parameters of the photovoltaic module at the plurality of bias voltages.

[0074] Among them, the above-mentioned impedance characteristic parameters include the parallel resistance value, the series resistance value and the fitting parameter value CPE-P of the constant phase element of the photovoltaic component at multiple bias voltages, and the above-mentioned multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic component, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic component.

[0075] S602: Outputting the fault type of the photovoltaic module according to the comparison result between the above impedance characteristic parameter and the preset impedance characteristic parameter.

[0076] In one embodiment, in order to improve the convenience of photovoltaic module detection, the detection method of the photovoltaic module 120 can be as follows: Figure 7 Execute as shown:

[0077] S701: When the output power of the photovoltaic module is less than the preset output power, impedance scanning is performed on the photovoltaic module through a zero bias voltage to obtain impedance characteristic parameters of the photovoltaic module at the zero bias voltage.

[0078] The impedance characteristic parameters of the photovoltaic component 120 at zero bias voltage include a first parallel resistance value, a first series resistance value, and a fitting parameter value CPE-P of a constant phase element (CPE) of the photovoltaic component 120 .

[0079] S702: Outputting a fault type of the photovoltaic module according to a comparison result between the impedance characteristic parameter at the zero bias voltage and the preset impedance characteristic parameter at the zero bias voltage.

[0080] Wherein, when the first parallel resistance value is greater than the first preset parallel resistance value, the fault type of the output photovoltaic assembly 120 is a diode open circuit fault. When the first parallel resistance value is less than the first preset parallel resistance value and the fitting parameter value CPE-P of the constant phase element is less than the preset fitting parameter value, the fault type of the output photovoltaic assembly 120 is a potential induced attenuation fault. When the photovoltaic assembly 120 has a diode open circuit fault or a potential induced attenuation fault, the power conversion device 110 can output the fault type of the photovoltaic assembly 120 as a diode open circuit fault or a potential induced attenuation fault, and execute S705 to end the fault detection process. When no fault is detected according to the comparison result of the impedance characteristic parameter at the zero bias voltage and the preset impedance characteristic parameter at the zero bias voltage, the power conversion device 110 further executes S703.

[0081] In one embodiment, in order to improve the accuracy of diode open circuit fault detection, the power conversion device 110 further outputs the fault type of the photovoltaic component 120 as a diode open circuit fault when the first parallel resistance value is greater than the first preset parallel resistance value and the difference between the first parallel resistance value and the first preset parallel resistance value is greater than a first threshold.

[0082] In one embodiment, in order to improve the accuracy of potential induced degradation fault detection, the power conversion device 110 further outputs the fault type of the photovoltaic assembly 120 as potential induced degradation fault when the first parallel resistance value is less than the first preset parallel resistance value, the difference between the first parallel resistance value and the first preset parallel resistance value is greater than the second threshold value, and the fitting parameter value CPE-P of the constant phase element is less than the preset fitting parameter value. Exemplarily, the above preset fitting parameter value is 0.96.

[0083] S703: performing impedance scanning on the photovoltaic component through the first bias voltage and the second bias voltage to obtain impedance characteristic parameters of the photovoltaic component at the first bias voltage and the second bias voltage.

[0084] In one embodiment, the power conversion device 110 first performs an impedance scan on the photovoltaic component 120 through a first bias voltage to obtain the impedance characteristic parameters of the photovoltaic component 120 at the first bias voltage. Then, the power conversion device 110 performs an impedance scan on the photovoltaic component 120 through a second bias voltage to obtain the impedance characteristic parameters of the photovoltaic component 120 at the second bias voltage.

[0085] In one embodiment, the power conversion device 110 first performs an impedance scan on the photovoltaic component 120 through the second bias voltage to obtain the impedance characteristic parameters of the photovoltaic component 120 at the second bias voltage. Then, the power conversion device 110 performs an impedance scan on the photovoltaic component 120 through the first bias voltage to obtain the impedance characteristic parameters of the photovoltaic component 120 at the first bias voltage.

[0086] S704: Outputting the fault type of the photovoltaic component according to the comparison result of the impedance characteristic parameter at zero bias voltage and the preset impedance characteristic parameter at zero bias voltage, the comparison result of the impedance characteristic parameter at the first bias voltage and the preset impedance characteristic parameter at the first bias voltage, and the comparison result of the impedance characteristic parameter at the second bias voltage and the preset impedance characteristic parameter at the second bias voltage.

[0087] In one embodiment, when the first parallel resistance value is less than the first preset parallel resistance value, the first series resistance value is greater than the first preset series resistance value, the fitting parameter value CPE-P of the constant phase element is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is less than or equal to the first series resistance value or the second series resistance value, the fault type of the output photovoltaic component 120 is a diode short circuit fault.

[0088] In one embodiment, when the first parallel resistance value is less than the first preset parallel resistance value, the fitting parameter value CPE-P of the constant phase element is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is greater than the first series resistance value and the second series resistance value, the fault type of the output photovoltaic assembly 120 is a battery crack fault or a battery corrosion fault. When the first parallel resistance value is less than the first preset parallel resistance value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is greater than the first series resistance value and the second series resistance value, the fault type of the output photovoltaic assembly 120 is a battery crack fault or a battery corrosion fault.

[0089] It is understandable that the order of performing impedance scanning on the photovoltaic component by using the first bias voltage and the second bias voltage and performing impedance scanning on the photovoltaic component by using the zero bias voltage can also be adjusted according to actual needs, and the embodiments of the present application do not impose specific restrictions on this.

[0090] In one embodiment, it is considered that the impedance characteristic parameters of the photovoltaic assembly change very little during normal use or when there is a broken grid fault. Therefore, when the impedance characteristic parameters of the photovoltaic assembly 120 at zero bias voltage, the first bias voltage, and the second bias voltage change less than the corresponding preset impedance characteristic parameters, the power conversion device 110 can output the corresponding fault type as the photovoltaic assembly 120 having a broken grid fault or the normal attenuation of the photovoltaic assembly 120. Among them, the above-mentioned small change is defined as the increase value of the parallel resistance value at each bias voltage relative to the corresponding preset parallel resistance value is less than 5% of the preset parallel resistance value, and the difference between the series resistance value at each bias voltage and the corresponding preset series resistance value is less than 2% of the preset series resistance value.

[0091] In order to facilitate understanding of the improvements of the power conversion device 110 provided in the embodiment of the present application, the embodiment of the present application is also described in detail through the following scenarios.

[0092] In one embodiment, after performing an impedance scan of a single photovoltaic module 120 in an initial state, a zero bias voltage V 0 is 0V, the first bias voltage V 1 is 2V, the second bias voltage V 2 is 29V, zero bias voltage V 0 The parallel resistance value Rsh at is 5000Ω, the series resistance value Rs is 1.2Ω, and the fitting parameter value CPE-P of the constant phase element is 0.98. The first bias voltage V 1 The parallel resistance value Rsh at is 10100Ω, and the series resistance value Rs is 1.17Ω. The second bias voltage V 2 The series resistance value Rs at is 2.4Ω. In subsequent operation and maintenance, impedance scanning is performed at three bias voltage points of 0V, 2V and 29V to obtain the impedance change of the photovoltaic module 120.

[0093] In one embodiment, in subsequent operation and maintenance, the impedance change of the photovoltaic module 120 is: zero bias voltage V 0The parallel resistance value Rsh at the photovoltaic module 120 is 8000Ω, the series resistance value Rs is 1.2Ω, and the fitting parameter value of the constant phase element is 0.98. Then the fault type of the photovoltaic module 120 output by the power conversion device 110 is a diode short circuit fault. The diode short circuit fault indicates that at least one diode in the photovoltaic module 120 is short-circuited, and an alarm is required to check whether the junction box diode is loose, etc., and replace or reinforce the diode to prevent the battery cell from burning out due to shadow shading caused by the diode short circuit during operation. In the case where the fault type of the photovoltaic module 120 is a diode short circuit fault, the power conversion device 110 does not need to pass the first bias voltage V 1 and the second bias voltage V 2 The photovoltaic module 120 is subjected to impedance scanning, thereby reducing the fault inspection time and improving the fault detection efficiency.

[0094] In one embodiment, in subsequent operation and maintenance, the impedance change of the photovoltaic module 120 is: zero bias voltage V 0 The parallel resistance value Rsh at the position is 800Ω, the series resistance value Rs is 1.2Ω, and the fitting parameter value CPE-P of the constant phase element is 0.8035. The power conversion device 110 outputs that the fault type of the photovoltaic component 120 is a potential induced degradation fault, and an alarm is required to replace the photovoltaic component 120. In the case where the fault type of the photovoltaic component 120 is a potential induced degradation fault, the power conversion device 110 does not need to pass the first bias voltage V 1 and the second bias voltage V 2 An impedance scan is performed on the photovoltaic assembly 120 to improve the efficiency of fault detection.

[0095] In one embodiment, in subsequent operation and maintenance, the impedance change of the photovoltaic module 120 is: zero bias voltage V 0 The parallel resistance value Rsh at is 3500Ω, the series resistance value Rs is 2Ω, and the fitting parameter value CPE-P of the constant phase element is 0.98. The first bias voltage V 1 The parallel resistance Rsh at is 7500Ω, and the series resistance Rs is 2.17Ω. The second bias voltage V 2 The series resistance value Rs at is 1.4Ω, and the fault type of the power conversion device 110 outputting the photovoltaic assembly 120 is a diode short circuit fault. The diode short circuit fault indicates that at least one diode in the photovoltaic assembly 120 is short-circuited, and an alarm is required to replace the diode in time.

[0096] In one embodiment, in subsequent operation and maintenance, the impedance change of the photovoltaic module 120 is: zero bias voltage V 0 The parallel resistance value Rsh at is 5100Ω, the series resistance value Rs is 1.4Ω, and the fitting parameter value CPE-P of the constant phase element is 0.98. The first bias voltage V1 The parallel resistance Rsh at is 8000Ω, and the series resistance Rs is 1.17Ω. The second bias voltage V 2 The series resistance value Rs at is 2.3Ω, and the fault type of the photovoltaic assembly 120 output by the power conversion device 110 is a battery crack fault or a battery corrosion fault.

[0097] In one embodiment, in subsequent operation and maintenance, the photovoltaic assembly 120 is at a zero bias voltage V 0 When the increase in the series resistance value under the first bias voltage and the second bias voltage is small and the parallel resistance value has no obvious change, the fault type of the power conversion device 110 outputting the photovoltaic component 120 is normal attenuation or the photovoltaic component 120 has a broken grid fault.

[0098] In summary, the embodiment of the present application provides a power conversion device, a photovoltaic power generation system and a detection method for a photovoltaic module, which are applied to the field of photovoltaic power generation technology. Among them, the power conversion device can perform impedance scanning on the photovoltaic module through multiple bias voltages to obtain the impedance characteristic parameters of the photovoltaic module at multiple bias voltages. Then, the power conversion device outputs the fault type of the photovoltaic module according to the comparison result of the impedance characteristic parameter and the preset impedance characteristic parameter. Among them, the above-mentioned impedance characteristic parameter includes the parallel resistance value, the series resistance value and the fitting parameter value of the constant phase element of the photovoltaic module at multiple bias voltages. The above-mentioned multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic module, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic module. Based on this, the fault of the photovoltaic module can be detected by the original power conversion device of the photovoltaic power generation system, and the fault type of the photovoltaic module only needs to be output by comparing the impedance characteristic parameters at three bias voltages with the preset impedance characteristic parameters during detection, which improves the fault detection efficiency of the photovoltaic module while reducing the cost.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed systems, circuits and devices can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the circuits and modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0100] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power conversion device, characterized in that: The DC input end of the power conversion device is used to connect to a photovoltaic module, wherein: The power conversion device is used to perform impedance scanning on the photovoltaic component through multiple bias voltages when the output power of the photovoltaic component is less than the preset output power, so as to obtain impedance characteristic parameters of the photovoltaic component at the multiple bias voltages; the impedance characteristic parameters include one or more of the parallel resistance value, the series resistance value and the fitting parameter value of the constant phase element of the photovoltaic component at the multiple bias voltages; the multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic component, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic component; The power conversion device is further used to output the fault type of the photovoltaic component according to the comparison result between the impedance characteristic parameter and the preset impedance characteristic parameter.

2. The power conversion device according to claim 1, characterized in that: The preset impedance characteristic parameter includes a first preset parallel resistance value; when the photovoltaic component is subjected to impedance scanning by the zero bias voltage, the impedance characteristic parameter includes the first parallel resistance value, and the power conversion device is used for: When the first parallel resistance value is greater than the first preset parallel resistance value, the fault type of the photovoltaic component is output as a diode open circuit fault.

3. The power conversion device according to claim 2, characterized in that: The power conversion device is used for: When the first parallel resistance value is greater than the first preset parallel resistance value and the difference between the first parallel resistance value and the first preset parallel resistance value is greater than a first threshold, the fault type of the photovoltaic component is output as a diode open circuit fault.

4. The power conversion device according to claim 3, characterized in that: The first threshold is greater than or equal to 10% of the first preset parallel resistance value.

5. The power conversion device according to claim 1, characterized in that: The preset impedance characteristic parameter includes a first preset parallel resistance value and a preset fitting parameter value of a constant phase element; when the photovoltaic component is subjected to impedance scanning by the zero bias voltage, the impedance characteristic parameter also includes the fitting parameter value of the constant phase element; the power conversion device is further used for: When the first parallel resistance value is less than the first preset parallel resistance value and the fitting parameter value is less than the preset fitting parameter value, the fault type of the photovoltaic component is output as a potential induced degradation fault.

6. The power conversion device according to claim 5, characterized in that: The power conversion device is further used for: When the first parallel resistance value is less than the first preset parallel resistance value, the difference between the first parallel resistance value and the first preset parallel resistance value is greater than a second threshold, and the fitting parameter value is less than the preset fitting parameter value, the fault type of the photovoltaic component is output as a potential induced degradation fault.

7. The power conversion device according to claim 6, characterized in that: The second threshold is greater than or equal to 10% of the first preset parallel resistance value.

8. The power conversion device according to claim 1, characterized in that: The preset impedance characteristic parameters include a first preset parallel resistance value, a first preset series resistance value, a second preset parallel resistance value, a second preset series resistance value and a preset fitting parameter value of a constant phase element; when the photovoltaic component is subjected to an impedance scan by the zero bias voltage, the impedance characteristic parameters also include a first series resistance value; when the photovoltaic component is subjected to an impedance scan by the first bias voltage, the impedance characteristic parameters also include a second parallel resistance value and a second series resistance value; when the photovoltaic component is subjected to an impedance scan by the second bias voltage, the impedance characteristic parameters also include a third series resistance value; the power conversion device is further used for: When the first parallel resistance value is less than the first preset parallel resistance value, the first series resistance value is greater than the first preset series resistance value, the fitting parameter value is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is less than or equal to the first series resistance value or the second series resistance value, the fault type of the photovoltaic component is output as a diode short circuit fault.

9. The power conversion device according to claim 1, characterized in that: The preset impedance characteristic parameters include a first preset parallel resistance value, a first preset series resistance value, a second preset parallel resistance value, a second preset series resistance value and a preset fitting parameter value of a constant phase element; when the photovoltaic component is subjected to an impedance scan by the zero bias voltage, the impedance characteristic parameters also include a first series resistance value; when the photovoltaic component is subjected to an impedance scan by the first bias voltage, the impedance characteristic parameters also include a second parallel resistance value and a second series resistance value; when the photovoltaic component is subjected to an impedance scan by the second bias voltage, the impedance characteristic parameters also include a third series resistance value; the power conversion device is further used for: When the first parallel resistance value is less than the first preset parallel resistance value, the fitting parameter value is greater than the preset fitting parameter value, the second series resistance value is greater than the second preset series resistance value, the second parallel resistance value is less than the second preset parallel resistance value, and the third series resistance value is greater than the first series resistance value and the second series resistance value, the fault type of the photovoltaic component is output as a battery crack fault or a battery corrosion fault.

10. A method for detecting a photovoltaic module, characterized in that: The photovoltaic assembly is connected to a DC input terminal of a power conversion device, and the method comprises: In the case where the output power of the photovoltaic component is less than the preset output power, the power conversion device performs impedance scanning on the photovoltaic component through multiple bias voltages to obtain impedance characteristic parameters of the photovoltaic component at the multiple bias voltages; the impedance characteristic parameters include the parallel resistance value, the series resistance value and the fitting parameter value of the constant phase element of the photovoltaic component at the multiple bias voltages; the multiple bias voltages include a zero bias voltage, a first bias voltage corresponding to the peak value of the parallel resistance of the photovoltaic component, and a second bias voltage corresponding to the peak value of the series resistance of the photovoltaic component; The power conversion device outputs the fault type of the photovoltaic component according to a comparison result between the impedance characteristic parameter and a preset impedance characteristic parameter.

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