Model selection method, system and device for direct current capacitor of photovoltaic inverter and medium

Abstract

The invention relates to a model selection method, system and device for a DC capacitor of a photovoltaic inverter and a medium, and the method comprises the steps: obtaining a loop stray inductance value of a DC-DC loop in the photovoltaic inverter through calculation; based on the real working environment parameters of the photovoltaic inverter, calculating to obtain an impulse voltage correction value of a direct current capacitor in the photovoltaic inverter; on the basis of the impact voltage correction value and the loop stray inductance value, the impact voltage of the direct-current capacitor is obtained through calculation; and calculating an output combined voltage of a programmable power supply in the durability test platform based on the impulse voltage so as to carry out a durability test on the direct-current capacitor to obtain the direct-current capacitor meeting a preset safety requirement. According to the method and the device, the real working environment parameters are used for correction on the impact voltage simulation calculation of the direct current capacitor, so that the endurance test is carried out to obtain the direct current capacitor meeting the requirement, the safe operation level of the inverter in different working environments is effectively improved, and the problem of how to select the type of the direct current capacitor of the photovoltaic inverter is solved.

Description

Technical Field

[0001] This application relates to the field of new energy power generation technology, and in particular to a method, system, device and medium for selecting DC capacitors for photovoltaic inverters. Background Technology

[0002] An inverter is a core power electronic device that converts direct current (DC) into alternating current (AC), and it is widely used in new energy, power systems, industrial control, and other fields. Its core function is to convert electrical energy output from DC power sources such as batteries and photovoltaic panels into AC power that matches the power grid or load through electronic switching devices (such as IGBTs and MOSFETs) and control technology.

[0003] The DC capacitor (also known as the DC link capacitor or support capacitor, hereinafter referred to as capacitor) of a photovoltaic inverter is a core component, also called the inverter DC support capacitor. It stabilizes the DC bus voltage and prevents voltage spikes from damaging power devices such as IGBTs. When the DC capacitor fails, it usually leads to DC bus burnout and even IGBT failure. Therefore, how to select the right DC capacitor for a photovoltaic inverter is a pressing issue that needs to be addressed.

[0004] Currently, no effective solution has been proposed for the selection of DC capacitors in photovoltaic inverters in related technologies. Summary of the Invention

[0005] This application provides a method, system, device, and medium for selecting DC capacitors for photovoltaic inverters, so as to at least solve the problem of how to select DC capacitors for photovoltaic inverters in related technologies.

[0006] In a first aspect, embodiments of this application provide a method for selecting DC capacitors for photovoltaic inverters, the method comprising:

[0007] The stray inductance value of the DC-DC circuit in the photovoltaic inverter is calculated.

[0008] Based on the actual operating environment parameters of the photovoltaic inverter, the impulse voltage correction value of the DC capacitor in the photovoltaic inverter is calculated.

[0009] Based on the impulse voltage correction value and the stray inductance value of the circuit, the impulse voltage of the DC capacitor in the photovoltaic inverter is calculated.

[0010] The output combined voltage of the programmable power supply in the durability test platform is calculated based on the impulse voltage, and the DC capacitor in the photovoltaic inverter is subjected to a durability test using the durability test platform to obtain a DC capacitor that meets the preset safety requirements.

[0011] In some embodiments, the impulse voltage correction value of the DC capacitor in the photovoltaic inverter is calculated based on the actual operating environment parameters of the photovoltaic inverter, including:

[0012] Obtain the actual operating environment parameters of the photovoltaic inverter;

[0013] Obtain the test environment parameters of the photovoltaic inverter during the inverter type test;

[0014] Based on the actual working environment parameters and the test environment parameters, the correction coefficient K is calculated using the first preset formula;

[0015] Based on the correction factor K and the rated voltage U of the photovoltaic inverter r The impulse voltage correction value ΔU of the DC capacitor in the photovoltaic inverter is calculated using the second preset formula.

[0016] In some embodiments, the impulse voltage of the DC capacitor in the photovoltaic inverter is calculated based on the impulse voltage correction value and the stray inductance value of the circuit, including:

[0017] Based on the impulse voltage correction value ΔU and the stray inductance value L0 of the circuit, the peak impulse voltage V of the DC capacitor in the photovoltaic inverter is calculated using the third preset formula. peak ;

[0018] Based on the peak impulse voltage V peak The impulse voltage U of the DC capacitor in the photovoltaic inverter is calculated using the fourth preset formula.

[0019] In some embodiments, calculating the combined output voltage of the programmable power supply in the durability testing platform based on the impulse voltage includes:

[0020] Based on the impulse voltage U and the rated voltage U r The output combined voltage U1 of the programmable power supply in the durability test platform is calculated using the fifth preset formula.

[0021] In some embodiments, the DC capacitors in the photovoltaic inverter are subjected to durability tests using a durability testing platform to obtain DC capacitors that meet preset safety requirements, including:

[0022] If the DC capacitor fails or the programmable power supply trips within 1000 hours when the programmable power supply continuously outputs the combined voltage U1 in the endurance test platform, the endurance test fails and the DC capacitor of the photovoltaic inverter is deemed unqualified.

[0023] If the DC capacitor passes the 1000-hour test, the parameters of the DC capacitor after the durability test are measured. If and only if the parameters after the durability test meet the preset safety requirements, the DC capacitor that has passed the durability test and meets the preset safety requirements is obtained.

[0024] In some embodiments, the method includes, prior to performing durability testing on the DC capacitors in the photovoltaic inverter using a durability testing platform:

[0025] A durability test platform for DC capacitors in a photovoltaic inverter is constructed. The durability test platform includes an oscilloscope, a voltage probe, a current probe, a programmable power supply, and a purely resistive load. The DC capacitors are connected in parallel in the test circuit, the purely resistive load is connected in series in the test circuit, and the programmable power supply has overcurrent protection function.

[0026] In some embodiments, the photovoltaic inverter is an SG225HX type inverter.

[0027] Secondly, embodiments of this application provide a selection system for DC capacitors in photovoltaic inverters. The system is used to execute the method described in the first aspect above. The system includes a parameter acquisition module, a voltage correction module, a voltage determination module, and a durability test module.

[0028] The parameter acquisition module is used to calculate the stray inductance value of the DC-DC circuit in the photovoltaic inverter.

[0029] The voltage correction module is used to calculate the impulse voltage correction value of the DC capacitor in the photovoltaic inverter based on the actual working environment parameters of the photovoltaic inverter.

[0030] The voltage determination module is used to calculate the impulse voltage of the DC capacitor in the photovoltaic inverter based on the impulse voltage correction value and the stray inductance value of the circuit.

[0031] The durability test module is used to calculate the output combined voltage U1 of the programmable power supply in the durability test platform based on the impulse voltage U, and to use the durability test platform to conduct a durability test on the DC capacitor in the photovoltaic inverter to obtain a DC capacitor that meets the preset safety requirements.

[0032] Thirdly, embodiments of this application provide an electronic device 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 method described in the first aspect above.

[0033] Fourthly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in the first aspect above.

[0034] Compared to related technologies, this application provides a method, system, device, and medium for selecting DC capacitors in photovoltaic inverters. The method calculates the stray inductance value of the DC-DC circuit in the photovoltaic inverter; calculates the impulse voltage correction value of the DC capacitor based on the actual operating environment parameters of the photovoltaic inverter; calculates the impulse voltage of the DC capacitor based on the impulse voltage correction value and the stray inductance value; calculates the output combined voltage of the programmable power supply in the durability test platform based on the impulse voltage; and conducts a durability test on the DC capacitor in the photovoltaic inverter using the durability test platform to obtain DC capacitors that meet preset safety requirements. This method achieves durability testing of DC capacitors in photovoltaic inverters by outputting a simulated calculated combined voltage from the test platform to screen out qualified DC capacitors. Furthermore, the simulation calculation of the impulse voltage of the DC capacitor is corrected using actual operating environment parameters, effectively improving the safe operation level of photovoltaic inverters under different operating environments and solving the problem of how to select DC capacitors for photovoltaic inverters. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a flowchart of the steps of the photovoltaic inverter DC capacitor selection method according to the embodiments of this application;

[0037] Figure 2 This is a simplified circuit diagram of a durability testing platform according to an embodiment of this application.

[0038] Figure 3 This is a schematic diagram of the internal structure of an electronic device according to an embodiment of this application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0040] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0041] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0042] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0043] This application provides a method for selecting DC capacitors for photovoltaic inverters. Figure 1 This is a flowchart illustrating the steps of a photovoltaic inverter DC capacitor selection method according to an embodiment of this application, as follows: Figure 1As shown, the method includes the following steps:

[0044] Step S102: Calculate the stray inductance value of the DC-DC circuit in the photovoltaic inverter;

[0045] Step S102 specifically involves solving for the stray inductance L using the formula HL = U, where H is the excitation matrix containing AC excitations of different frequencies, L is the stray inductance of the loop to be determined, and U is the terminal voltage of the stray inductance of the loop. The following matrix formula is obtained experimentally:

[0046]

[0047] The set of L is calculated, L i Let L be the stray inductance value of the loop in the i-th test; then sort it using the bubble sort method, and take the average of the five largest values ​​in set L as L0. L0 represents the stray inductance value of the DC-DC loop in the photovoltaic inverter.

[0048] It should be noted that in the DC-DC circuit of an inverter, stray inductance is a non-ideal inductance introduced by factors such as wiring, parasitic parameters of components, and busbar structure. Stray inductance can cause problems such as voltage spikes, electromagnetic interference (EMI), and switching losses. Therefore, accurate calculation or measurement of stray inductance is crucial for optimizing system performance.

[0049] Step S104: Based on the actual operating environment parameters of the photovoltaic inverter, calculate the impulse voltage correction value of the DC capacitor in the photovoltaic inverter.

[0050] Step S104 specifically includes the following steps:

[0051] Step S1041: Obtain the actual operating environment parameters for the photovoltaic inverter to operate;

[0052] Specifically, step S1041 involves obtaining the multi-year summer average temperature T1 and multi-year summer average humidity H1 in the actual working environment in which the photovoltaic inverter is to operate.

[0053] Step S1042: Obtain the test environment parameters of the photovoltaic inverter during the inverter type test;

[0054] Specifically, step S1042 involves obtaining the ambient temperature T0, ambient humidity H0, and DC capacitor limit temperature rise T during the inverter type test of the photovoltaic inverter. max .

[0055] It should be noted that inverter type testing is a finalization test conducted on inverter products to verify whether they meet technical specifications. Specifically, by simulating actual operating environments, the performance parameters of the inverter (such as conversion efficiency, anti-islanding protection, low voltage ride-through, etc.) are comprehensively evaluated to ensure that the product meets relevant standards and safety requirements. Key test contents include basic performance tests (such as core indicators such as conversion efficiency, power factor, and harmonic suppression), safety protection tests (such as verification of safety functions such as islanding protection, low voltage ride-through, and short circuit protection), and environmental adaptability tests (such as vibration tests and temperature rise tests).

[0056] Step S1043: Based on the actual working environment parameters and the test environment parameters, the correction coefficient K is calculated using the first preset formula;

[0057] Specifically, step S1043 involves using the first preset formula:

[0058]

[0059] The correction factor K is calculated, where T0 is the ambient temperature of the photovoltaic inverter during the inverter type test, H0 is the ambient humidity of the photovoltaic inverter during the inverter type test, and T max T1 represents the maximum temperature rise of the DC capacitor during inverter type testing; T1 represents the average summer ambient temperature over many years in the actual operating environment of the photovoltaic inverter; and H1 represents the average summer ambient humidity over many years in the actual operating environment of the photovoltaic inverter.

[0060] Step S1044, based on the correction factor K and the rated voltage U of the photovoltaic inverter r The impulse voltage correction value ΔU of the DC capacitor in the photovoltaic inverter is calculated using the second preset formula.

[0061] Specifically, step S1044 involves using the second preset formula:

[0062] ΔU=0.85*K*U r

[0063] The calculated impulse voltage correction value ΔU of the DC capacitor in the photovoltaic inverter is obtained, where K is the correction coefficient, and U r This is the rated voltage of the photovoltaic inverter.

[0064] Step S106: Based on the impulse voltage correction value and the stray inductance value of the circuit, the impulse voltage of the DC capacitor in the photovoltaic inverter is calculated.

[0065] Step S106 specifically includes the following steps:

[0066] Step S1061: Based on the impulse voltage correction value ΔU and the stray inductance value L0 of the circuit, the peak impulse voltage V of the DC capacitor in the photovoltaic inverter is calculated using the third preset formula. peak ;

[0067] Specifically, step S1061 involves using a third preset formula:

[0068]

[0069] The peak impulse voltage V of the DC capacitor in the photovoltaic inverter was calculated. peak Where ΔU is the impulse voltage correction value, L0 is the stray inductance of the circuit, and U r Let i be the rated voltage of the photovoltaic inverter, i be the current, and t be the time. This represents the rate of change of current when the IGBT switching device is switched on or off.

[0070] Step S1062, then based on the peak impulse voltage V peak The impulse voltage U of the DC capacitor in the photovoltaic inverter is calculated using the fourth preset formula.

[0071] Specifically, step S1062 involves using the fourth preset formula:

[0072] U = V peak *t*e -1.25t

[0073] The impulse voltage U of the DC capacitor in the photovoltaic inverter is calculated, where V peak Here, t represents the peak value of the impulse voltage, t represents time, and e represents a constant.

[0074] Step S108: Calculate the output combined voltage of the programmable power supply in the durability test platform based on the impulse voltage, and use the durability test platform to conduct a durability test on the DC capacitor in the photovoltaic inverter to obtain a DC capacitor that meets the preset safety requirements.

[0075] Step S108 specifically includes the following steps:

[0076] Step S1081, based on the impulse voltage U and the rated voltage U r The output combined voltage U1 of the programmable power supply in the durability test platform is calculated using the fifth preset formula.

[0077] Specifically, step S1081 involves the fifth preset formula:

[0078]

[0079] The output combined voltage U1 of the programmable power supply in the durability test platform is calculated, where U rU is the rated voltage of the photovoltaic inverter, and U is the impulse voltage of the DC capacitor in the photovoltaic inverter.

[0080] Step S1082, under the condition that the programmable power supply in the durability test platform continuously outputs the combined voltage U1 for 1000 hours:

[0081] If the DC capacitor of U1 fails or the programmable power supply trips within 1000 hours, the endurance test fails and the DC capacitor of the photovoltaic inverter is deemed unqualified.

[0082] If the DC capacitor passes the 1000-hour test, the parameters of the DC capacitor after the durability test are measured. If and only if the parameters after the durability test meet the preset safety requirements, a DC capacitor that has passed the durability test and meets the preset safety requirements is obtained.

[0083] Specifically, step S1082, regarding "measuring the parameters of the DC capacitor after the endurance test, if and only if the parameters after the endurance test meet the preset safety requirements," specifically, it involves measuring the inter-electrode resistance R1 of the DC capacitor after the endurance test, and the total partial discharge X1 (in picocoos, PC) within half an hour at 1.1 times the rated voltage, if and only if... In the case where the parameters meet the preset safety requirements after the durability test, a DC capacitor that has passed the durability test and meets the preset safety requirements is obtained. Here, R0 is the initial inter-electrode resistance of the DC capacitor in the photovoltaic inverter before the durability test, and X0 is the corresponding initial partial discharge total amount in half an hour at 1.1 times the rated voltage.

[0084] Through the steps described in this application embodiment, a combined voltage calculated by simulation output from the test platform is used to conduct a durability test on the DC capacitor in the photovoltaic inverter, thereby selecting the DC capacitor that meets the requirements. Furthermore, the simulation calculation of the impulse voltage of the DC capacitor is corrected using parameters from the actual working environment, which effectively improves the safe operation level of the photovoltaic inverter under different working environments. This has significant practical engineering value and solves the problem of how to select the DC capacitor for the photovoltaic inverter.

[0085] In some preferred embodiments, before performing durability testing on the DC capacitor in the photovoltaic inverter using the durability testing platform in the above embodiments, the method provided by this preferred embodiment includes:

[0086] A durability test platform for DC capacitors in a photovoltaic inverter was constructed. The platform includes an oscilloscope, voltage probe, current probe, programmable power supply, and a purely resistive load. The DC capacitors are connected in parallel in the test circuit, and the purely resistive load is connected in series in the test loop. The programmable power supply has overcurrent protection. Figure 2This is a simplified circuit diagram of a durability testing platform according to an embodiment of this application. The photovoltaic inverter is preferably an SG225HX type inverter.

[0087] It should be noted that the steps shown in the above process or in the flowchart of the accompanying figures can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0088] This application provides a selection system for DC capacitors in photovoltaic inverters. The system includes a parameter acquisition module, a voltage correction module, a voltage determination module, and a durability test module.

[0089] The parameter acquisition module is used to calculate the stray inductance value of the DC-DC circuit in the photovoltaic inverter.

[0090] The voltage correction module is used to calculate the impulse voltage correction value of the DC capacitor in the photovoltaic inverter based on the actual working environment parameters of the photovoltaic inverter.

[0091] The voltage determination module is used to calculate the impulse voltage of the DC capacitor in the photovoltaic inverter based on the impulse voltage correction value and the stray inductance value of the circuit.

[0092] The durability test module is used to calculate the output combined voltage U1 of the programmable power supply in the durability test platform based on the impulse voltage U, and to use the durability test platform to conduct durability tests on the DC capacitors in the photovoltaic inverter to obtain DC capacitors that meet the preset safety requirements.

[0093] The parameter acquisition module, voltage correction module, voltage determination module, and durability test module in this application embodiment enable the use of a test platform to output a simulated and calculated combined voltage to conduct durability tests on the DC capacitors in the photovoltaic inverter, thereby selecting qualified DC capacitors. Furthermore, the simulation calculation of the DC capacitor's impulse voltage is corrected using parameters from the actual working environment, effectively improving the safe operation level of the photovoltaic inverter under different working environments. This has significant engineering practical value and solves the problem of how to select the DC capacitor for the photovoltaic inverter.

[0094] It should be noted that the above modules can be functional modules or program modules, and can be implemented through software or hardware. For modules implemented through hardware, the above modules can reside in the same processor; or the above modules can be located in different processors in any combination.

[0095] This embodiment provides an electronic device including a memory and a processor. The memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0096] Optionally, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0097] Optionally, the electronic device may further include a processor, memory, network interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When the computer program is executed by the processor, it implements a method for selecting DC capacitors for a photovoltaic inverter. The display screen may be a liquid crystal display (LCD) or an e-ink display. The input device may be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the device's casing, or an external keyboard, touchpad, or mouse.

[0098] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0099] Furthermore, in conjunction with the photovoltaic inverter DC capacitor selection method in the above embodiments, this application embodiment can provide a storage medium for implementation. This storage medium stores a computer program; when executed by a processor, the computer program implements any of the photovoltaic inverter DC capacitor selection methods in the above embodiments.

[0100] In one embodiment, Figure 3 This is a schematic diagram of the internal structure of an electronic device according to an embodiment of this application, such as... Figure 3 As shown, an electronic device is provided, which can be a server, and its internal structure diagram can be as follows. Figure 3 As shown, the electronic device includes a processor, a network interface, internal memory, and non-volatile memory connected via an internal bus. The non-volatile memory stores an operating system, computer programs, and a database. The processor provides computing and control capabilities, the network interface communicates with external terminals via a network, the internal memory provides an environment for the operating system and computer programs to run, the computer programs are executed by the processor to implement a method for selecting DC capacitors for a photovoltaic inverter, and the database stores data.

[0101] Those skilled in the art will understand that Figure 3 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the electronic device to which the present application is applied. A specific electronic device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0102] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0103] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0104] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for selecting DC capacitors for photovoltaic inverters, characterized in that, The method includes: The stray inductance value of the DC-DC circuit in the photovoltaic inverter is calculated. Based on the actual operating environment parameters of the photovoltaic inverter, the impulse voltage correction value of the DC capacitor in the photovoltaic inverter is calculated. Based on the impulse voltage correction value and the stray inductance value of the circuit, the impulse voltage of the DC capacitor in the photovoltaic inverter is calculated. The output combined voltage of the programmable power supply in the durability test platform is calculated based on the impulse voltage, and the DC capacitor in the photovoltaic inverter is subjected to a durability test using the durability test platform to obtain a DC capacitor that meets the preset safety requirements.

2. The method according to claim 1, characterized in that, Based on the actual operating environment parameters of the photovoltaic inverter, the calculated impulse voltage correction values ​​for the DC capacitor in the photovoltaic inverter include: Obtain the actual operating environment parameters of the photovoltaic inverter; Obtain the test environment parameters of the photovoltaic inverter during the inverter type test; Based on the actual working environment parameters and the experimental environment parameters, using the first preset formula: The correction factor K is calculated, where T0 is the ambient temperature of the photovoltaic inverter during the inverter type test, H0 is the ambient humidity of the photovoltaic inverter during the inverter type test, and T max T1 represents the maximum temperature rise of the DC capacitor during the inverter type test of the photovoltaic inverter; T1 represents the average summer ambient temperature over many years in the actual working environment of the photovoltaic inverter; and H1 represents the average summer ambient humidity over many years in the actual working environment of the photovoltaic inverter. Based on the correction factor K and the rated voltage U of the photovoltaic inverter r Through the second preset formula: ΔU=0.85*K*U r The calculated impulse voltage correction value ΔU of the DC capacitor in the photovoltaic inverter is obtained, where K is the correction coefficient, and U r This is the rated voltage of the photovoltaic inverter.

3. The method according to claim 2, characterized in that, Based on the impulse voltage correction value and the stray inductance value of the circuit, the impulse voltage of the DC capacitor in the photovoltaic inverter is calculated as follows: Based on the impulse voltage correction value ΔU and the stray inductance value L0 of the circuit, using the third preset formula: The peak impulse voltage V of the DC capacitor in the photovoltaic inverter was calculated. peak Where ΔU is the impulse voltage correction value, L0 is the stray inductance of the circuit, and U r Let i be the rated voltage of the photovoltaic inverter, i be the current, and t be the time. The rate of change of current when the IGBT switching device is turned on; Based on the peak impulse voltage V peak Through the fourth preset formula: U=V peak *t*e -1.25t The impulse voltage U of the DC capacitor in the photovoltaic inverter is calculated, where V peak Here, t represents the peak value of the impulse voltage, t represents time, and e represents a constant.

4. The method according to claim 3, characterized in that, Based on the aforementioned impulse voltage, the output combined voltage of the programmable power supply in the durability testing platform is calculated to include: Based on the impulse voltage U and the rated voltage U r Through the fifth preset formula: The output combined voltage U1 of the programmable power supply in the durability test platform is calculated, where U r U is the rated voltage of the photovoltaic inverter, and U is the impulse voltage of the DC capacitor in the photovoltaic inverter.

5. The method according to claim 4, characterized in that, The DC capacitors in the photovoltaic inverter were subjected to durability tests using a durability testing platform to obtain DC capacitors that meet the preset safety requirements, including: If the DC capacitor fails or the programmable power supply trips within 1000 hours when the programmable power supply continuously outputs the combined voltage U1 in the endurance test platform, the endurance test fails and the DC capacitor of the photovoltaic inverter is deemed unqualified. If the DC capacitor passes the 1000-hour test, the parameters of the DC capacitor after the durability test are measured. If and only if the parameters after the durability test meet the preset safety requirements, the DC capacitor that has passed the durability test and meets the preset safety requirements is obtained.

6. The method according to claim 1, characterized in that, Before conducting durability tests on the DC capacitors in the photovoltaic inverter using a durability testing platform, the method includes: A durability test platform for DC capacitors in a photovoltaic inverter is constructed. The durability test platform includes an oscilloscope, a voltage probe, a current probe, a programmable power supply, and a purely resistive load. The DC capacitors are connected in parallel in the test circuit, the purely resistive load is connected in series in the test circuit, and the programmable power supply has overcurrent protection function.

7. The method according to claim 1, characterized in that, The photovoltaic inverter is an SG225HX type inverter.

8. A selection system for DC capacitors in photovoltaic inverters, characterized in that, The system is used to perform the method according to any one of claims 1 to 7, and the system includes a parameter acquisition module, a voltage correction module, a voltage determination module, and a durability test module; The parameter acquisition module is used to calculate the stray inductance value of the DC-DC circuit in the photovoltaic inverter. The voltage correction module is used to calculate the impulse voltage correction value of the DC capacitor in the photovoltaic inverter based on the actual working environment parameters of the photovoltaic inverter. The voltage determination module is used to calculate the impulse voltage of the DC capacitor in the photovoltaic inverter based on the impulse voltage correction value and the stray inductance value of the circuit. The durability test module is used to calculate the output combined voltage U1 of the programmable power supply in the durability test platform based on the impulse voltage U, and to use the durability test platform to conduct a durability test on the DC capacitor in the photovoltaic inverter to obtain a DC capacitor that meets the preset safety requirements.

9. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method of any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1 to 7.

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