Method and device for detecting ground capacitance value of photovoltaic module, controller, storage medium and photovoltaic system

Abstract

The invention provides a ground capacitance detection method and device of a photovoltaic module, a controller, a storage medium and a photovoltaic system, and the method comprises the steps: obtaining a voltage between the positive and negative output ends of a photovoltaic string when a preset switch is switched off, and taking the voltage as a first voltage; taking the voltage of the photovoltaic string between the positive and negative output ends when the preset switch is closed as a second voltage; according to a ratio relation between the first voltage and the second voltage, determining a fault photovoltaic module in the photovoltaic string; charging and discharging the faulted photovoltaic string by controlling the on-off of the preset switch, and obtaining the full-charge voltage, the discharge voltage and the discharge duration of the photovoltaic string; and determining the ground capacitance value of the fault photovoltaic module according to the full-charge voltage, the discharge voltage and the discharge duration of the photovoltaic module string. According to the method, the photovoltaic modules do not need to be detected one by one, so that the ground capacitance value detection process is greatly simplified, and the ground capacitance value detection efficiency is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic system technology, and in particular to a method, apparatus, controller, storage medium, and photovoltaic system for detecting the ground capacitance of a photovoltaic module. Background Technology

[0002] Insulation testing of photovoltaic modules is a key step in ensuring the safe and stable operation of photovoltaic systems. It can effectively prevent leakage risks caused by module insulation failure, prevent short circuits, arc discharges and other faults caused by insulation degradation, reduce equipment damage such as junction box burnout and cable aging, and extend the service life of photovoltaic systems.

[0003] The ground capacitance of a photovoltaic (PV) module is the equivalent parasitic capacitance between the internal conductive structure of the PV module (such as cells and solder strips) and the grounding terminal (frame and support), reflecting the electric field coupling strength of the module's insulating medium. When the ground parasitic capacitance of a PV module increases, it indicates a decrease in its insulation performance. Therefore, the insulation performance of a PV module can be determined by detecting the magnitude of the parasitic capacitance. Current technology typically uses an LCR bridge to measure the ground capacitance of each PV module sequentially. However, this method is cumbersome, time-consuming, and results in low efficiency in detecting insulation faults. Summary of the Invention

[0004] This invention provides a method, apparatus, controller, storage medium, and photovoltaic system for detecting the ground capacitance of photovoltaic modules, thereby solving the problem of low efficiency in detecting the ground capacitance at the module level in the prior art.

[0005] In a first aspect, embodiments of the present invention provide a method for detecting the ground capacitance of a photovoltaic module, applied to a photovoltaic system; the photovoltaic system includes a photovoltaic string; the photovoltaic string includes a preset switch and multiple photovoltaic modules connected in series, and the first output terminal of the photovoltaic string is grounded through the preset switch; the first output terminal is either the positive output terminal or the negative output terminal of the photovoltaic string; The method includes: The voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open is obtained and used as the first voltage; the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed is used as the second voltage. Based on the ratio between the first voltage and the second voltage, the faulty photovoltaic module in the photovoltaic string is determined; By controlling the opening and closing of the preset switch, the faulty photovoltaic string is charged and discharged, and the full charge voltage, discharge voltage and discharge duration of the photovoltaic string are obtained. The ground capacitance of the faulty photovoltaic module is determined based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string.

[0006] Secondly, embodiments of the present invention provide a device for detecting the ground capacitance of a photovoltaic module, applied to a photovoltaic system; the photovoltaic system includes a photovoltaic string; the photovoltaic string includes a preset switch and multiple photovoltaic modules connected in series, and the first output terminal of the photovoltaic string is grounded through the preset switch; the first output terminal is either the positive output terminal or the negative output terminal of the photovoltaic string; The device includes: The voltage acquisition module is used to acquire the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and use it as the first voltage; and to use the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as the second voltage. The fault component determination module is used to determine the faulty photovoltaic module in the photovoltaic string based on the ratio between the first voltage and the second voltage. The charging and discharging parameter acquisition module is used to charge and discharge the faulty photovoltaic string by controlling the opening and closing of the preset switch, and to acquire the full charge voltage, discharge voltage and discharge duration of the photovoltaic string. The ground capacitance calculation module is used to determine the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string.

[0007] Thirdly, embodiments of the present invention provide a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the photovoltaic module's ground capacitance detection method as described in any possible implementation of the first aspect above.

[0008] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the photovoltaic module ground capacitance detection method as described in any possible implementation of the first aspect above.

[0009] Fifthly, this embodiment provides a photovoltaic system, which includes: a photovoltaic string and a controller as described in the third aspect above.

[0010] This invention provides a method, apparatus, controller, storage medium, and photovoltaic system for detecting the ground capacitance of photovoltaic modules. The method first obtains the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and uses it as a first voltage; then, it uses the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as a second voltage; then, based on the ratio between the first voltage and the second voltage, it determines the faulty photovoltaic module in the photovoltaic string. This avoids the cumbersome process of measuring insulation faults in each photovoltaic module individually, and significantly improves the efficiency of ground capacitance detection. Secondly, by controlling the opening and closing of the preset switch, the faulty photovoltaic string is charged and discharged, and the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string are obtained. Finally, based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string, the ground capacitance of the faulty photovoltaic module is determined. This ingeniously transforms complex capacitance measurement into voltage and time measurement that the system can automatically complete without additional precision instruments, thereby greatly improving detection efficiency and achieving a leap from simple fault location to quantitative evaluation of insulation performance. This provides key data support for preventing insulation failure and leakage risks caused by excessive ground capacitance, and significantly improves the intelligence level and safety of photovoltaic system operation and maintenance. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of the photovoltaic system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the specific structure of the photovoltaic system provided in the embodiment of the present invention; Figure 3 This is a flowchart illustrating the implementation of the method for detecting the ground capacitance of photovoltaic modules provided in this embodiment of the invention. Figure 4 This is a schematic diagram of the structure of the photovoltaic module ground capacitance detection device provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Detailed Implementation

[0013] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0015] Figure 1 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of the present invention. Figure 1 As shown, the photovoltaic system includes a photovoltaic string; the photovoltaic string includes a preset switch and multiple photovoltaic modules (PVM1~PVMn) connected in series, and the first output terminal of the photovoltaic string is grounded through the preset switch K0; the first output terminal is the positive output terminal or the negative output terminal of the photovoltaic string.

[0016] Specifically, the positive output terminal PV+ of the photovoltaic string is connected to the positive bus of the photovoltaic system, and the negative output terminal PV- of the photovoltaic string is connected to the negative bus of the photovoltaic system. The positive and negative buses can be connected to subsequent photovoltaic converters. These photovoltaic converters can be photovoltaic inverters or rectifiers.

[0017] In this embodiment, the photovoltaic system further includes a voltage sensor, a current sensor, and a controller. The voltage sensor detects the voltage between the positive and negative output terminals of the photovoltaic string and sends this voltage value to the controller. The current sensor detects the current value at the first output terminal of the photovoltaic string and sends this current value to the controller. The controller can control the on / off state of a preset switch K0 and can also detect the capacitance of the photovoltaic module to ground.

[0018] Specifically, the preset switch K0 can be an electronic switch such as a relay or MOSFET, and it must meet the switching reliability requirements under high voltage DC.

[0019] In one embodiment, Figure 2 This embodiment shows a schematic diagram of the specific structure of the photovoltaic system provided, as follows: Figure 2 As shown, the photovoltaic string includes multiple (PV1~PVn), the positive output terminal PV+ of each photovoltaic string is connected to the positive bus of the photovoltaic system, and the negative output terminal PV- of each photovoltaic string is connected to the negative bus of the photovoltaic system. When the first output terminal is the positive output terminal PV+, the negative output terminal of the photovoltaic string is connected to the negative bus via a switching device K1 (K1-1 to K1-4); the switching device is a relay switch or a diode; and when the switching device K1 is a diode, the negative output terminal of the photovoltaic string is connected to the negative terminal of the diode, and the positive terminal of the diode is connected to the negative bus.

[0020] In this embodiment, reference Figure 2 The photovoltaic system includes multiple MPPT (Maximum Power Point Tracking) modules. Each MPPT module (MPPT1 to MPPT2) includes at least one photovoltaic string. Multiple photovoltaic strings in each MPPT module are connected in parallel. The positive output terminal PV+ of each MPPT module is connected to the positive bus, and the negative output terminal PV- of each MPPT module is connected to the negative bus. The positive and negative buses are used to connect to the input terminal of the photovoltaic converter.

[0021] Specifically, each photovoltaic string has a diode K2 (K2-1 to K2-2) connected between its positive output terminal PV+ and the positive busbar. The positive terminal of the diode is connected to the positive output terminal PV+ of the corresponding photovoltaic string, and the negative terminal of the diode is connected to the positive busbar.

[0022] To address the aforementioned circuit structure, this embodiment provides a method for detecting the ground capacitance at the photovoltaic module level. (See [link to relevant documentation]). Figure 3 The document illustrates a flowchart of the implementation of a method for detecting the ground capacitance of a photovoltaic module according to an embodiment of the present invention. This method is applied to a controller in a photovoltaic system and is described in detail below: S101: Obtain the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and use it as the first voltage; use the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as the second voltage.

[0023] In this embodiment, during the standby state before grid connection after the photovoltaic converter starts up, the controller controls a preset switch to open. The voltage sensor detects the voltage value between the positive and negative terminals of the photovoltaic string at this time and sends this voltage value as the first voltage to the controller. This first voltage can be the open-circuit voltage of the photovoltaic string, that is, the sum of the voltages of each photovoltaic module.

[0024] In this embodiment, after obtaining the first voltage, the controller controls the preset switch to close, grounding the negative / positive output terminals of the photovoltaic string. The voltage sensor detects the voltage value between the positive and negative terminals of the photovoltaic string at this time and sends this voltage value to the controller as the second voltage. At this time, the faulty photovoltaic module causes a voltage drop due to the reduced insulation resistance, resulting in the second voltage being less than the first voltage.

[0025] S102: Determine the faulty photovoltaic module in the photovoltaic string based on the ratio between the first voltage and the second voltage.

[0026] In this embodiment, the second voltage is affected by the faulty photovoltaic module, causing the voltage value of the entire photovoltaic string to drop. Specifically, when a photovoltaic module experiences an insulation fault, the insulation medium between the internal circuit of the photovoltaic module and the grounding frame (or grounding terminal) fails, forming a low-resistance leakage path. At this time, the faulty photovoltaic module is grounded, and a short circuit occurs between the first pole output terminal of the photovoltaic string and the faulty photovoltaic module. The voltage value of the entire photovoltaic string is then determined by the voltage values ​​of the remaining photovoltaic modules that are not in a short circuit. Therefore, this embodiment can determine the number of photovoltaic modules that are not in a short circuit based on the ratio between the first voltage and the second voltage of the photovoltaic string, thereby determining the location of the faulty photovoltaic module in the photovoltaic string.

[0027] S103: By controlling the opening and closing of the preset switch, the faulty photovoltaic string is charged and discharged, and the full-charge voltage, discharge voltage and discharge duration of the photovoltaic string are obtained.

[0028] In this embodiment, to calculate the parasitic capacitance of the faulty photovoltaic module, the charging and discharging of the faulty photovoltaic string can be controlled, and the full-charge voltage of the photovoltaic module when fully charged, the voltage when fully discharged, and the corresponding discharge duration can be collected. The discharge duration is the time taken for the photovoltaic string to go from a fully charged state to being fully discharged.

[0029] S104: Determine the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string.

[0030] Specifically, this embodiment can calculate the ground capacitance of the faulty photovoltaic module by performing a single charge-discharge test on the faulty photovoltaic string, thereby significantly shortening the detection time of the ground capacitance of the photovoltaic module.

[0031] As can be seen from the above embodiments, the method first obtains the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and uses it as the first voltage; then, it uses the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as the second voltage; then, based on the ratio between the first voltage and the second voltage, the faulty photovoltaic module in the photovoltaic string is determined. This avoids the tedious process of measuring insulation faults of each photovoltaic module individually, significantly improving the efficiency of ground capacitance detection. Secondly, by controlling the opening and closing of the preset switch, the faulty photovoltaic string is charged and discharged, and the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string are obtained; finally, based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string, the ground capacitance of the faulty photovoltaic module is determined. This cleverly transforms complex capacitance measurement into voltage and time measurement that the system can automatically complete, without the need for additional precision instruments, thereby greatly improving detection efficiency and achieving a leap from simple fault location to quantitative evaluation of insulation performance. This provides key data support for preventing insulation failure and leakage risks caused by excessive ground capacitance, significantly improving the intelligence level and safety of photovoltaic system operation and maintenance.

[0032] In one possible implementation, when the first output terminal is the negative output terminal, the specific implementation process of S102 includes: The ratio of the first voltage to the second voltage is used as the first proportion.

[0033] The first value N is calculated based on the first proportion and the number of photovoltaic modules in the photovoltaic string; Starting from the positive output terminal of the photovoltaic string, the (N+1)th photovoltaic module is identified as a faulty photovoltaic module. Specifically, in this embodiment, the second voltage can be divided by the first voltage to obtain the first proportion; this value reflects the degree of voltage attenuation of the photovoltaic string under insulation grounding fault conditions. Of course, the first voltage can also be divided by the second voltage to obtain the first proportion.

[0034] In this embodiment, the first output terminal is taken as the negative output terminal. Assuming the insulation impedance of each component in the photovoltaic string is uniformly distributed, the fault point divides the photovoltaic string into two sections: the first section is from the positive output terminal of the photovoltaic string to the fault point, and the second section is from the fault point to the negative output terminal of the photovoltaic string. Since both the photovoltaic module at the fault point and the negative output terminal are grounded, the second section of the photovoltaic string is short-circuited. Therefore, the total voltage of the photovoltaic string is determined by the voltage of the first section. This embodiment can determine the number of photovoltaic modules in the first section based on the first proportion and the total number of photovoltaic modules in the photovoltaic string; alternatively, it can determine the number of photovoltaic modules in the second section based on the first proportion and the total number of photovoltaic modules in the photovoltaic string, thereby identifying the faulty photovoltaic module.

[0035] In this embodiment, when the first proportion is the ratio of the second voltage to the first voltage, the controller can multiply the first proportion by the number of photovoltaic modules in the photovoltaic string to obtain a first value N. This first value is precisely the number of photovoltaic modules that were not short-circuited in the previous section. Therefore, in this embodiment, starting from the positive output terminal of the photovoltaic string, counting backwards to the (N+1)th photovoltaic module, we can identify the photovoltaic module that experienced an insulation fault and grounding, thus determining it as the faulty photovoltaic module.

[0036] Furthermore, if the first value is not an integer, the two nearest integer neighbors of the first value are taken as target values ​​A and B. Taking the positive output terminal of the photovoltaic string as the starting point, the (A+1)th and (B+1)th photovoltaic modules are identified as faulty photovoltaic modules. The module-level insulation fault is located in these two adjacent photovoltaic modules, and then the location of the insulation fault can be further located by individual testing. It can be seen that this method can greatly reduce the workload of insulation testing and improve the insulation testing efficiency of photovoltaic modules, even in application scenarios where the first value is not an integer.

[0037] As can be seen from the above embodiments, this embodiment is based on the principle that after the negative electrode is grounded, the components between the fault point and the grounding point will be short-circuited, causing a decrease in the output voltage of the entire photovoltaic string. By calculating the ratio of the first voltage to the second voltage and relating it to the total number of components in the photovoltaic string, the location of the fault point from the positive electrode starting point can be accurately calculated. Based on the above principle, this method can quickly and accurately locate the photovoltaic module with insulation faults by measuring only two voltage values ​​and performing simple calculations, greatly simplifying the operation process, reducing diagnostic time and human subjective error, and is particularly suitable for rapid troubleshooting and maintenance of large-scale photovoltaic power plants.

[0038] In one possible implementation, when the first electrode output terminal is the negative electrode output terminal, another specific implementation process for determining the faulty photovoltaic module described above may include: Divide the second voltage by the first voltage to obtain the first proportion; Based on formula Determine a second value M, where M is the number of photovoltaic modules in the photovoltaic string that are short-circuited; Starting from the negative output terminal of the photovoltaic string, the Mth photovoltaic module forward of it is identified as a faulty photovoltaic module, where n represents the number of photovoltaic modules in the photovoltaic string and k represents the first proportion.

[0039] Specifically, since photovoltaic strings typically assign serial numbers to each photovoltaic module from the negative output terminal to the positive output terminal, this embodiment can directly associate the value of M with the corresponding photovoltaic module serial number by calculating the second value M, eliminating the need to search for the corresponding photovoltaic module from the beginning, thereby further reducing the efficiency of detecting the ground capacitance of photovoltaic modules.

[0040] Furthermore, if the second value is not an integer, the two nearest integers to the second value are taken as target values ​​C and D; starting from the negative output terminal of the photovoltaic string, the Cth and Dth forward photovoltaic modules are both identified as faulty photovoltaic modules. The module-level insulation fault is located in two adjacent photovoltaic modules, and then the location of the insulation fault is further located.

[0041] The above method can avoid misdetection or missed detection of faulty photovoltaic modules by identifying photovoltaic modules near the ratio value when the ratio is not an integer.

[0042] In one possible implementation, to prevent current from other photovoltaic modules from flowing back to the faulty photovoltaic module when the photovoltaic module fails, thus causing the second voltage distortion of the faulty photovoltaic module, this embodiment can provide a diode between the positive output terminal of each photovoltaic module and the positive bus. The positive terminal of the diode is connected to the positive output terminal of the corresponding photovoltaic module, and the negative terminal of the diode is connected to the positive bus.

[0043] As can be seen from the above embodiments, for the configuration of photovoltaic systems with negative grounding, this embodiment fully considers the circuit characteristics of photovoltaic strings when the negative ground is grounded. It utilizes the linear relationship between voltage distribution and photovoltaic module position in series circuit to ensure the accuracy of insulation fault location. Furthermore, it uses the number N of un-short-circuited photovoltaic modules to reverse locate the faulty module, transforming abstract electrical parameters into specific module serial numbers. This enables maintenance personnel to quickly pinpoint the fault location, reduce troubleshooting time, and improve maintenance efficiency.

[0044] In one possible implementation, the first output terminal is a positive output terminal; correspondingly, the negative output terminal of the photovoltaic string is connected to the negative bus via a switching device; the specific implementation process for determining the second voltage in S101 includes: When the preset switch is in the closed state and the switching device is in the open state, the voltage between the positive and negative terminals of the photovoltaic string when the preset switch is closed is obtained.

[0045] In this embodiment, reference Figure 2 When the first output terminal is the positive output terminal, if there is a photovoltaic module with an insulation fault, since the negative terminals of the photovoltaic modules in each MPPT module are all connected together, the current of the photovoltaic string with the insulation fault will flow to other photovoltaic strings connected to its negative terminal, causing the detected second voltage to be distorted. Therefore, in this embodiment, a switching device can be set at the negative terminal of each photovoltaic string to isolate the negative terminals of each photovoltaic string, so as to monitor the accurate photovoltaic voltage when there is a faulty photovoltaic module.

[0046] The switching devices may include switching transistors and relays, and the switching transistors may be MOSFETs or diodes. When the second voltage is detected, the preset switch is closed, and the switching devices are not turned on.

[0047] As can be seen from the above embodiments, this embodiment can avoid mutual interference when multiple photovoltaic strings are connected in parallel, ensuring the accuracy of voltage measurement. When the positive terminal is grounded, the fault current path may be affected by other strings, but by disconnecting the switching device, the voltage change of a single photovoltaic string can be measured independently, improving the accuracy of fault detection. Therefore, it is applicable to positively grounded systems, enhancing the versatility of the solution. At the same time, it reduces the influence of external factors on the measurement, improves the reliability and repeatability of detection, and provides a reliable data foundation for subsequent fault location. It is particularly beneficial for fault diagnosis of complex photovoltaic systems, effectively preventing false alarms and missed alarms.

[0048] In one possible implementation, another step in S102 includes: The ratio of the first voltage to the second voltage is taken as the first proportion; The first value N is calculated based on the first proportion and the number of photovoltaic modules in the photovoltaic string; Starting from the negative output terminal of the photovoltaic string, the Nth photovoltaic module preceding it is identified as a faulty photovoltaic module.

[0049] Taking the first output terminal as the positive output terminal as an example. Assuming that the insulation impedance of each component in the photovoltaic string is uniformly distributed, the fault point divides the photovoltaic string into two sections: the first section is from the positive output terminal of the photovoltaic string to the fault point, and the second section is from the fault point to the negative output terminal of the photovoltaic string. Since both the photovoltaic module at the fault point and the positive output terminal are grounded, the first section of the photovoltaic string is short-circuited. Therefore, the total voltage of the photovoltaic string is determined by the voltage of the second section. In this embodiment, the number of photovoltaic modules in the first section can be determined based on the first proportion and the total number of photovoltaic modules in the photovoltaic string; alternatively, the number of photovoltaic modules in the second section can be determined based on the first proportion and the total number of photovoltaic modules in the photovoltaic string, thereby identifying the faulty photovoltaic module.

[0050] In this embodiment, taking the ratio obtained by dividing the second voltage by the first voltage as an example, the first ratio is multiplied by the number of photovoltaic modules in the photovoltaic string to obtain a first value N. Then, starting from the negative output terminal of the photovoltaic string, the Nth photovoltaic module counted backward is determined to be a faulty photovoltaic module.

[0051] Furthermore, if the first value is not an integer, the two nearest integers to the first value are taken as target values ​​A and B; starting from the negative output terminal of the photovoltaic string, the A-th and B-th forward photovoltaic modules are both identified as faulty photovoltaic modules. The module-level insulation fault is located in two adjacent photovoltaic modules, and then the location of the insulation fault is further located.

[0052] As can be seen from the above embodiments, in this embodiment, when the first output terminal is the positive output terminal, the number N of photovoltaic modules that are not short-circuited is obtained by calculating the first proportion and the number of modules in the photovoltaic string, and the Nth photovoltaic module forward is identified as the faulty photovoltaic module starting from the negative output terminal. This method complements the positioning logic when the negative terminal is grounded, making this detection method applicable to photovoltaic systems with different grounding methods. Furthermore, this embodiment fully utilizes the voltage division principle of series circuits, combined with the circuit characteristics when the positive terminal is grounded, to ensure the accuracy of photovoltaic module insulation fault location. In addition, this embodiment locates the faulty module starting from the negative output terminal, which conforms to the electrical connection sequence of the photovoltaic string, enabling maintenance personnel to quickly find the fault point according to the module arrangement order, improving the efficiency of fault diagnosis.

[0053] In one possible implementation, when the first electrode output terminal is a positive electrode output terminal, another implementation process for determining the faulty photovoltaic module described above may include: Based on formula Determine a second value M, where M is the number of photovoltaic modules in the photovoltaic string that are short-circuited; Starting from the positive output terminal of the photovoltaic string, the (M+1)th photovoltaic module thereafter is identified as a faulty photovoltaic module; where n represents the number of photovoltaic modules in the photovoltaic string, and k represents the first proportion.

[0054] Furthermore, if the second value is not an integer, the two nearest integers to the second value are taken as target values ​​C and D; starting from the positive output terminal of the photovoltaic string, the (C+1)th and (D+1)th photovoltaic modules are identified as faulty photovoltaic modules. The module-level insulation fault is located in two adjacent photovoltaic modules, and then the location of the insulation fault is further located.

[0055] In one possible implementation, prior to S104, the method provided in this embodiment further includes: The current at the first pole output terminal when the preset switch is closed is obtained and used as a reference current; The impedance to ground of the photovoltaic string is calculated based on the second voltage and the reference current.

[0056] Specifically, in this embodiment, a current sensor can be installed between a preset switch and ground. The current sensor collects the current between the preset switch and ground as a reference current and sends it to the controller. The controller divides the second voltage by the reference current to obtain the ground impedance of the photovoltaic string. Based on the ground impedance, the ground capacitance of the faulty photovoltaic module is further calculated.

[0057] In one possible implementation, the specific implementation process of S103 includes: The preset switch is controlled to open, and the full-charge voltage of the faulty photovoltaic string after it is fully charged is obtained; The preset switch is controlled to close, and the voltage (i.e., discharge voltage) and corresponding discharge duration of the faulty photovoltaic string after discharge are obtained.

[0058] In this embodiment, firstly, the controller controls the preset switch to open. At this time, the photovoltaic string has no grounding loop and is charged to a stable voltage by sunlight. When the voltage fluctuation is less than a preset fluctuation threshold, the voltage at this time is collected by a voltage sensor as the full-charge voltage V0. Secondly, the controller controls the preset switch to close. The ground capacitance C of the faulty photovoltaic module is discharged sequentially through its ground resistance, ground, the ground resistance of the first pole output terminal, the preset switch, and the first pole output terminal of the photovoltaic string. The discharge time t from the full-charge voltage V0 to the discharge voltage Vt is collected by the voltage sensor. The discharge voltage can be the voltage of the positive and negative pole output terminals when the photovoltaic string is fully discharged.

[0059] As can be seen from the above embodiments, this embodiment charges the string to full voltage by controlling the opening of a preset switch, and then discharges it through the ground resistance at the fault grounding point by closing the preset switch, recording the discharge voltage and duration. It utilizes the characteristic that the ground capacitance at the fault point stores and releases charge during this process, transforming the abstract measurement of ground capacitance into a standardized operational sequence that the control system can automatically execute, accurately time, and measure. The entire process requires no manual intervention or connection to external testing equipment, achieving online and automated detection. This not only ensures high efficiency but also avoids human error, guarantees data consistency, and lays a reliable foundation for subsequent accurate calculation of ground capacitance.

[0060] In one possible implementation, the specific implementation process of S104 includes: Based on formula Determine the ground capacitance of the faulty photovoltaic module; Where C represents the capacitance to ground of the faulty photovoltaic module, and V t V represents the discharge voltage, V0 represents the full charge voltage, and t represents the discharge duration.

[0061] Specifically, after calculating the ground impedance, the degree of insulation failure of the faulty photovoltaic module can be determined based on the magnitude of the ground impedance, where R represents the ground impedance.

[0062] Specifically, if the capacitance to ground is greater than the first preset capacitance threshold and less than or equal to the second preset capacitance threshold, the faulty photovoltaic module is determined to be in the early stage of failure. If the capacitance to ground is greater than the second preset capacitance threshold, the faulty photovoltaic module is determined to be in the severe stage of failure. Where the first preset capacitance threshold is less than the second preset capacitance threshold, the cause of the early stage of failure could be moisture or aging of the insulating medium. The cause of the severe failure is complete cable damage.

[0063] In this embodiment, when the ground capacitance value is greater than a first preset capacitance threshold and less than or equal to a second preset capacitance threshold, a potential serious fault can be predicted in advance by continuously monitoring the ground capacitance value change rate. Specifically, this embodiment subtracts the previous ground capacitance value from the current ground capacitance value to obtain the current ground capacitance value change rate. If the current ground capacitance value change rate is greater than the first preset change rate threshold, and the ground capacitance value change rates detected in the previous N times are all greater than the first preset change rate threshold, then a serious insulation fault is predicted to occur in the photovoltaic string. Maintenance reminder information can be generated to provide personnel with the necessary maintenance for the faulty photovoltaic modules, preventing the fault from escalating. For example, when changes in ambient humidity cause a temporary decrease in insulation, the ground capacitance value change rate is small, and there may be a short period where the ground capacitance value change rate decreases and then rises back to its original value. This can be distinguished from permanent faults (such as cable damage), thereby reducing the false alarm rate and improving system reliability.

[0064] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0065] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0066] Figure 4 A schematic diagram of the structure of the photovoltaic module ground capacitance detection device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 4 As shown, the photovoltaic module's ground capacitance detection device 100 includes: The voltage acquisition module 110 is used to acquire the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and use it as the first voltage; and use the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as the second voltage. The fault component determination module 120 is used to determine the faulty photovoltaic component in the photovoltaic string based on the ratio between the first voltage and the second voltage. The charging and discharging parameter acquisition module 130 is used to charge and discharge the faulty photovoltaic string by controlling the opening and closing of the preset switch, and to acquire the full charge voltage, discharge voltage and discharge duration of the photovoltaic string. The ground capacitance calculation module 140 is used to determine the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage and discharge duration of the photovoltaic string.

[0067] In one possible implementation, the first pole output terminal is the negative pole output terminal; the fault component determination module 120 includes: The first ratio calculation unit is used to take the ratio of the first voltage to the second voltage as the first ratio; The first numerical determination unit is used to calculate the first numerical value N based on the first proportion and the number of photovoltaic modules in the photovoltaic string; An insulation fault location unit is used to identify the (N+1)th photovoltaic module after the positive output terminal of the photovoltaic string as a faulty photovoltaic module.

[0068] In one possible implementation, the first output terminal is a positive output terminal; correspondingly, the negative output terminal of the photovoltaic string is connected to the negative bus via a switching device; the voltage acquisition module 110 is specifically used for: When the preset switch is in the closed state and the switching device is in the open state, the voltage between the positive and negative terminals of the photovoltaic string is obtained and used as the second voltage.

[0069] In one possible implementation, the fault component determination module 120 is specifically used for: The ratio of the first voltage to the second voltage is taken as the first proportion; The first value N is calculated based on the first proportion and the number of photovoltaic modules in the photovoltaic string; Starting from the negative output terminal of the photovoltaic string, the Nth photovoltaic module preceding it is identified as a faulty photovoltaic module.

[0070] In one possible implementation, the charge / discharge parameter acquisition module 130 includes: The preset switch is controlled to open, and the full-charge voltage of the faulty photovoltaic string after it is fully charged is obtained; The preset switch is controlled to close, and the discharge voltage and corresponding discharge duration of the faulty photovoltaic string after discharge are obtained.

[0071] In one possible implementation, the photovoltaic module's ground capacitance detection device further includes a reference current acquisition module, used for: The current at the first pole output terminal when the preset switch is closed is obtained and used as a reference current; Calculate the ground impedance of the photovoltaic string based on the second voltage and the reference current; Accordingly, the ground tolerance calculation module 140 is specifically used for: Based on formula Determine the ground capacitance of the faulty photovoltaic module; Where C represents the capacitance to ground of the faulty photovoltaic module, and V t V represents the discharge voltage, V0 represents the full charge voltage, t represents the discharge duration, and R represents the impedance to ground.

[0072] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 5 As shown, the controller 5 in this embodiment includes a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, it implements the steps in the above embodiments of the photovoltaic module's ground capacitance detection method, for example... Figure 3 Steps S101 to S104 are shown. Alternatively, when the processor 50 executes the computer program 52, it implements the functions of each module / unit in the above-described device embodiments.

[0073] For example, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 52 in the controller 5.

[0074] The controller 5 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will understand that... Figure 5 This is merely an example of controller 5 and does not constitute a limitation on controller 5. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0075] The processor 50 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0076] The memory 51 can be an internal storage unit of the controller 5, such as a hard disk or memory of the controller 5. The memory 51 can also be an external storage device of the controller 5, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 5. Furthermore, the memory 51 can include both internal storage units and external storage devices of the controller 5. The memory 51 is used to store the computer program and other programs and data required by the controller. The memory 51 can also be used to temporarily store data that has been output or will be output.

[0077] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0078] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0079] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0080] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0081] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0082] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0083] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of the above embodiments of the photovoltaic module ground capacitance detection method. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0084] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for detecting the ground capacitance of a photovoltaic module, characterized in that, This technology is applied to photovoltaic systems; the photovoltaic system includes photovoltaic strings; the photovoltaic string includes a preset switch and multiple photovoltaic modules connected in series, and the first output terminal of the photovoltaic string is grounded through the preset switch; the first output terminal is either the positive output terminal or the negative output terminal of the photovoltaic string. The method includes: The voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open is obtained and used as the first voltage; the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed is used as the second voltage. Based on the ratio between the first voltage and the second voltage, the faulty photovoltaic module in the photovoltaic string is determined; By controlling the opening and closing of the preset switch, the faulty photovoltaic string is charged and discharged, and the full charge voltage, discharge voltage and discharge duration of the photovoltaic string are obtained. The ground capacitance of the faulty photovoltaic module is determined based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string.

2. The method for detecting the ground capacitance of a photovoltaic module according to claim 1, characterized in that, The first output terminal is the negative output terminal; the step of determining the faulty photovoltaic module in the photovoltaic string based on the ratio between the first voltage and the second voltage includes: The ratio of the first voltage to the second voltage is taken as the first proportion; The first value N is calculated based on the first proportion and the number of photovoltaic modules in the photovoltaic string; Starting from the positive output terminal of the photovoltaic string, the N+1th photovoltaic module is identified as a faulty photovoltaic module.

3. The method for detecting the ground capacitance of a photovoltaic module according to claim 1, characterized in that, The photovoltaic string comprises multiple photovoltaic strings, the positive output terminal of each photovoltaic string is connected to the positive bus of the photovoltaic system, and the negative output terminal of each photovoltaic string is connected to the negative bus of the photovoltaic system; the first output terminal is the positive output terminal; correspondingly, the negative output terminal of the photovoltaic string is connected to the negative bus through a switching device. The step of obtaining the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed, and using it as the second voltage, includes: When the preset switch is in the closed state and the switching device is in the open state, the voltage between the positive and negative terminals of the photovoltaic string is obtained and used as the second voltage.

4. The method for detecting the ground capacitance of a photovoltaic module according to claim 3, characterized in that, The step of determining the faulty photovoltaic module in the photovoltaic string based on the ratio between the first voltage and the second voltage includes: The ratio of the first voltage to the second voltage is taken as the first proportion; The first value N is calculated based on the first proportion and the number of photovoltaic modules in the photovoltaic string; Starting from the negative output terminal of the photovoltaic string, the Nth photovoltaic module preceding it is identified as a faulty photovoltaic module.

5. The method for detecting the ground capacitance of a photovoltaic module according to claim 1, characterized in that, The process of charging and discharging the faulty photovoltaic string by controlling the opening and closing of the preset switch, and obtaining the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string, includes: The preset switch is controlled to open, and the full-charge voltage of the faulty photovoltaic string after it is fully charged is obtained; The preset switch is controlled to close, and the discharge voltage and corresponding discharge duration of the faulty photovoltaic string after discharge are obtained.

6. The method for detecting the ground capacitance of a photovoltaic module according to claim 1, characterized in that, Before determining the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string, the method further includes: The current at the first pole output terminal when the preset switch is closed is obtained and used as a reference current; Calculate the ground impedance of the photovoltaic string based on the second voltage and the reference current; Accordingly, determining the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string includes: Based on formula Determine the ground capacitance of the faulty photovoltaic module; Where C represents the capacitance to ground of the faulty photovoltaic module, and V t V represents the discharge voltage, V0 represents the full charge voltage, t represents the discharge duration, and R represents the impedance to ground.

7. A device for detecting the ground capacitance of a photovoltaic module, characterized in that, This technology is applied to photovoltaic systems; the photovoltaic system includes photovoltaic strings; the photovoltaic string includes a preset switch and multiple photovoltaic modules connected in series, and the first output terminal of the photovoltaic string is grounded through the preset switch; the first output terminal is either the positive output terminal or the negative output terminal of the photovoltaic string. The device includes: The voltage acquisition module is used to acquire the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is open, and use it as the first voltage; and to use the voltage between the positive and negative output terminals of the photovoltaic string when the preset switch is closed as the second voltage. The fault component determination module is used to determine the faulty photovoltaic module in the photovoltaic string based on the ratio between the first voltage and the second voltage. The charging and discharging parameter acquisition module is used to charge and discharge the faulty photovoltaic string by controlling the opening and closing of the preset switch, and to acquire the full charge voltage, discharge voltage and discharge duration of the photovoltaic string. The ground capacitance calculation module is used to determine the ground capacitance of the faulty photovoltaic module based on the full-charge voltage, discharge voltage, and discharge duration of the photovoltaic string.

8. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting the ground capacitance of the photovoltaic module as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for detecting the ground capacitance of the photovoltaic module as described in any one of claims 1 to 6.

10. A photovoltaic system, characterized in that, It includes photovoltaic strings and the controller as described in claim 7.

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