Method and system for calculating short-circuit current of photovoltaic power station

Abstract

The application discloses a kind of short-circuit current calculation methods of photovoltaic power station, method includes obtaining the amplitude reduction value of inverter output electric energy. With the unit of bus-tie box, obtain the current each group amplitude reduction value of each group solar unit component connected. According to the nominal series loss of each group, whether the current each group amplitude reduction value is fault amplitude reduction is judged, and first output power value and second output power value are obtained respectively. According to the first output power value and / or second output power value, the short-circuit current of photovoltaic access point photovoltaic power station is obtained. Therefore, according to the real-time measurement of electric energy monitoring, the short-circuit current is obtained, the safety, reliability of power system operation is improved, especially the switching state of solar energy system is used as an operating condition, and the actual electric energy output condition in the operation process of solar power station is more truly embodied.

Description

Technical Field

[0001] This invention belongs to the field of power monitoring and maintenance technology, and in particular relates to a method and system for calculating the short-circuit current of a photovoltaic power station. Background Technology

[0002] In existing power systems, the calculation of short-circuit current for photovoltaic power plants often uses per-unit value or nominal value methods. Depending on the actual application, the short-circuit current is often estimated based on multiples of the rated current. In the process of estimating or calculating the short-circuit current, the output power of the photovoltaic power plant is generally an estimated value. However, during the power generation and maintenance of photovoltaic power plants, the output power may fluctuate due to sunlight and equipment shading. As a result, the accuracy of the calculation of short-circuit current for existing photovoltaic power plants is poor.

[0003] Meanwhile, the calculation of short-circuit current in existing technologies is mainly used to maintain the normal operation of the line through relay protection. It is mostly calculated and obtained during the design stage, which has poor real-time availability and is not convenient for dynamic monitoring. Summary of the Invention

[0004] The embodiments of the present invention are intended to solve at least one of the above-mentioned technical problems.

[0005] In a first aspect, embodiments of the present invention provide a method for calculating the short-circuit current of a photovoltaic power station. The photovoltaic power station includes: multiple sets of solar cell modules, a combiner box, an inverter, and a detection controller. Multiple sets of solar cell modules connected in series are respectively combined in the combiner box. The output line of the combiner box is connected to the inverter. Each solar cell module is equipped with a backup solar cell, which is connected to its respective solar cell module via a backup switching circuit.

[0006] The inverter output of the photovoltaic power station is connected to the main line via the overhead line length parameter and the transformer. The detection controller has multiple input terminals and multiple output terminals.

[0007] The methods for calculating the short-circuit current of a photovoltaic power station include:

[0008] Step S101: Obtain the reduction value of the inverter output power.

[0009] Step S102: Using the combiner box as a unit, obtain the current reduction value of each group of solar unit modules connected to it.

[0010] Step S103: Determine whether the current reduction value of each group is a fault reduction based on the nominal series loss of each group. If not, obtain the first output power value based on the actual measured power loss and the rated output power of the solar unit module of this group.

[0011] Step S1031: If yes, obtain the power value of each solar cell in the solar cell module. Determine the defect characteristic type based on the power value of each solar cell, and drive the switching circuit according to the defect characteristic type to add the backup solar cell to its corresponding solar cell module.

[0012] In step S1032, the second output power value is obtained based on the actual measured power loss and the rated output power of the switched solar unit module.

[0013] Step S104: Obtain the output power of each combiner box based on its first output power value and / or second output power value.

[0014] Step S105: Obtain the maximum output power of the total inverter by summing the output power of each combiner box.

[0015] Step S106: Obtain the short-circuit current of the photovoltaic power station at the photovoltaic access point based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

[0016] Secondly, embodiments of the present invention provide a system for calculating the short-circuit current of a photovoltaic power station. The photovoltaic power station includes: multiple sets of solar cell modules, a combiner box, an inverter, and a detection controller. Multiple sets of solar cell modules connected in series are respectively combined in the combiner box. The output line of the combiner box is connected to the inverter. Each solar cell module is equipped with a backup solar cell, which is connected to its respective solar cell module via a backup switching circuit.

[0017] The inverter output of the photovoltaic power station is connected to the main line via overhead line length parameters and a transformer. The detection controller has multiple input terminals and multiple output terminals. The short-circuit current calculation system of the photovoltaic power station includes: an inverter sag value acquisition unit, configured to acquire the sag value of the inverter output power; and a combiner box sag value acquisition unit, configured to acquire the current sag value of each group of solar unit modules connected to the combiner box as a unit.

[0018] The first power acquisition unit is configured to determine whether the current power loss of each group is a fault-related power loss based on the nominal series loss of each group. If not, it acquires a first output power value based on the actual measured power loss and the rated output power of the solar unit module in this group. The second power acquisition unit is configured to acquire the power value of each solar unit in the solar unit module if the power loss is faulty. Based on the power value of each solar unit, it determines the defect characteristic type and drives the switching circuit according to the defect characteristic type to add a backup solar unit to the corresponding solar unit module.

[0019] The second output power value is obtained based on the actual measured power loss and the rated output power of the switched solar unit modules. The combiner box output power acquisition unit is configured to acquire the output power of each combiner box based on its first and / or second output power values.

[0020] The maximum output power value acquisition unit is configured to obtain the total maximum output power value of the inverter based on the sum of the output power of each combiner box. The short-circuit current acquisition unit obtains the short-circuit current of the photovoltaic power station at the photovoltaic access point based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

[0021] This invention monitors the usage status of solar energy units. After switching to a backup system based on their power generation efficiency, it monitors their output power. While ensuring the amount of solar power generated, it can monitor their power generation in real time and calculate their maximum output current based on the actual situation. The current value is closer to the actual usage situation, providing effective data for the later modification and maintenance of the line. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a system composition diagram of an embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention;

[0024] Figure 2 This is a flowchart of an embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention;

[0025] Figure 3 This is a system composition diagram of another embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0028] This invention can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, elements, data structures, etc., that perform a specific task or implement a specific abstract data type. This invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0029] In this invention, terms such as "module," "device," and "system" refer to relevant entities applied to a computer, such as hardware, combinations of hardware and software, software, or software in execution. More specifically, for example, an element can be, but is not limited to, a process running on a processor, a processor, an object, an executable element, an execution thread, a program, and / or a computer. Furthermore, an application program or script running on a server, and the server itself, can also be an element. One or more elements may be in an execution process and / or thread, and elements may be localized on a single computer and / or distributed across two or more computers, and may be run on various computer-readable media. Elements can also communicate via local and / or remote processes based on signals having one or more data packets, for example, signals from data interacting with another element in a local system, a distributed system, and / or interacting with other systems via signals over a network of the Internet.

[0030] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising" or "including" include not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] In one embodiment of the present invention, a method for calculating the short-circuit current of a photovoltaic power station is disclosed. For example... Figure 1 As shown, the photovoltaic power station includes: multiple sets of solar unit modules 10, 20, 30, and 40; combiner boxes 50 and 60; inverter 70; and a monitoring controller. Each set of solar unit modules includes multiple solar panels connected in series. Taking solar unit module 10 as an example, solar unit module 10 includes solar panels 11, 12, 13, 14, and 15 connected in series.

[0032] Multiple sets of solar unit modules connected in series are fed into combiner boxes 50 and 60. The output lines of combiner boxes 50 and 60 are connected to inverter 70. Each solar unit module is equipped with a backup solar unit, which is connected to its assigned solar unit module via a backup switching circuit.

[0033] The inverter output of the photovoltaic power station is connected to the main line via the overhead line length parameter and the transformer. The detection controller has multiple input terminals and multiple output terminals.

[0034] like Figure 2 As shown, the calculation method for the short-circuit current of a photovoltaic power station includes:

[0035] Step S101: Obtain the reduction value of the inverter output power.

[0036] In this step, the decrease in inverter output power can be determined by comparing the normal output power of inverter 70 with the current output power.

[0037] Step S102: Obtain the current reduction value of each group of solar unit modules.

[0038] In this step, taking combiner boxes 50 and 60 as units, the current sag values ​​of each group of solar unit modules connected to them are obtained. For example, the sag values ​​of combiner boxes 50 and 60 are obtained first, and then the sag values ​​of each group of solar unit modules connected to the combiner boxes are obtained. All of the above data can be obtained through the control systems of the inverter and combiner boxes. If this data cannot be obtained, the output values ​​of each combiner box can be obtained by measuring other lines.

[0039] Step S103: Obtain the first output power value.

[0040] Determine whether the current reduction value of each group is a fault reduction value based on the nominal series loss of each group. If not, obtain the first output power value based on the actual measured power loss and the rated output power of the solar unit module of this group.

[0041] This allows us to obtain the actual power loss of each solar unit module during long-term use, which is very suitable for the long-term maintenance of solar power plants. When a solar power plant is in use, the replacement of individual solar cells, or the inability to replace them in a timely manner, will affect other solar panels in the solar unit module. Although the rated power loss is 95% to 98%, the power loss will change year by year during long-term use. In the existing methods, this parameter is detected during maintenance, but it is not dynamic.

[0042] The above actual measured power loss is based on the current reduction value P of each group. 1ΔThe ratio value is calculated from the rated output power P1. The rated output power can be the factory power of the solar module, or it can be the power under normal operating conditions during its annual inspection. The first output power value is obtained by multiplying the actual measured power loss by the rated output power of this group of solar unit modules.

[0043] Step S1031: Switch the faulty unit.

[0044] In this step, the nominal series loss of each group is used to determine whether the current reduction value of each group is a fault reduction value. If so, the power value of each solar cell in the solar unit module is obtained. Based on the power value of each solar cell, the defect characteristic type is obtained, and the switching circuit is driven according to the defect characteristic type to enable the backup solar cell to be added to the corresponding solar unit module.

[0045] The fault reduction value can be understood as a value significantly lower than the value during long-term use, or a value given based on empirical judgment. By obtaining the power values ​​of each solar cell unit in solar module 10, 20, 30, and 40, the operating status of each solar panel can be understood. In the use of solar cell arrays, issues such as shading, dust, and snow / rain coverage can occur. While faults are usually addressed based on these issues, over time, this reduces and diminishes the long-term power generation of the solar cell array.

[0046] In this invention, the backup switching circuit switches control whenever a fault occurs, which not only eliminates the impact of the fault in a timely manner, but also treats the switching control as a normal operation and incorporates it into the overall output power of the solar power station, thus truly reflecting its actual operation.

[0047] If the power values ​​of each solar panel (e.g., solar panels 11, 12, 13, 14, 15) are close to the normal power value, it indicates complete damage or a short circuit. If the power value is 20%–40% of the normal value, consider dust and snow / rain cover. If the power value is 40%–50% of the normal value, consider shading and obstruction. The above values ​​are based on experience and may vary in different regions.

[0048] Based on the different defects mentioned above, the switching circuit is driven so that the circuit can be in a normal power generation state.

[0049] It should be noted that the switched circuit is still monitored. After the switch, the nominal series loss of each group is used to determine whether the current reduction value of each group is a fault reduction. If so, the power value of each solar cell in the solar unit module is obtained. The defect characteristic type is obtained based on the power value of each solar cell, and the switching circuit is driven according to the defect characteristic type. Especially in the case of shading fault, if the output power of the original solar cell is not 0, the original solar panel can still be switched back to use. Therefore, the switching in this invention is a normal and very flexible process, which is beneficial for the long-term use of solar power plants.

[0050] Step S1032: Obtain the second output power value.

[0051] In this step, the second output power value is obtained based on the actual measured power loss and the rated output power of the switched solar unit module.

[0052] Step S104: Obtain the output power of each combiner box.

[0053] In this step, the output power of each combiner box 50 and 60 is obtained based on the first output power value and / or the second output power value of each combiner box 50 and 60.

[0054] If a second output power value is not available, the first output power value is used to obtain the output power of each combiner box. Alternatively, the output power of each combiner box can be obtained by summing the first output power value with the second output power value.

[0055] Step S105: Obtain the maximum output power value.

[0056] In this step, the maximum output power of the total inverter 70 is obtained by summing the output power of each combiner box 50 and 60.

[0057] Step S106: Obtain the short-circuit current of the photovoltaic power station at the photovoltaic access point.

[0058] In this step, the short-circuit current of the photovoltaic power station at the photovoltaic access point is obtained based on the maximum output power value, the overhead line length parameter, and the transformer capacity and transformer impedance.

[0059] For example, based on the above calculations, its maximum output power is 1000kW. The overhead line voltage level is 10kV. The transformer capacity is 800kVA, the distance to the high-voltage distribution point is L, and U is the output voltage of the photovoltaic power station.

[0060] Transformer short-circuit voltage U k =9%, assuming a baseline capacity S b Line impedance per unit length X L Reference voltage U bThe short-circuit current at the photovoltaic connection point is:

[0061] Line impedance per unit value: X1 = X L ×L×(S b / U b 2 )

[0062] Transformer impedance per unit value: X2 = (U k / 100)×S b / 800

[0063] Total impedance per unit: X3 = X1 + X2

[0064] Per-unit value of electromotive force: E = U / U b

[0065] Short-circuit current per unit value: I k =E / X3.

[0066] The above parameters can also be used to calculate the effective value of the short-circuit current, the total current value, and the impulse current value. This allows for the acquisition of the short-circuit current at the photovoltaic power station's connection point.

[0067] Therefore, by monitoring and acquiring short-circuit current based on real-time measured power energy, the safety and reliability of the power system operation are improved. In particular, by taking the switching status of the solar system as an operating condition, the actual power output during the operation of the solar power station is more realistically reflected.

[0068] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, step S101 further includes:

[0069] The front-end derating value is obtained based on the derating value of the inverter 70's output power and the inverter 70's power loss rate. For example: derating value: 10kW, inverter power loss rate: 95%, front-end derating value is 10.52kW.

[0070] Measure the intermediate line loss from each combiner box 50 / 60 to the inverter 70 based on their arrangement. Obtain the line length based on the arrangement of combiner boxes 50 / 60. Based on the line length, determine the line impedance and the reference capacity S. b Reference voltage U b The intermediate line loss can be obtained. For example, the intermediate line loss is 0.15kw.

[0071] Based on the intermediate line loss and front-end droop value of each combiner box 50 and 60, obtain the total droop value of all combiner boxes 50 and 60. For example, 10.52 + 0.15 = 10.67 kW.

[0072] Based on the measured output power and rated output value of each combiner box, obtain the output deviation value of each combiner box; install a combiner box detection switch in the connection line between each combiner box and the inverter.

[0073] Install detection switches for combiner boxes 50 and 60 in the connection lines of each combiner box 50, 60 and inverter 70.

[0074] The output of the detection controller is connected to the detection switches of combiner boxes 50 and 60. When the input of the detection controller receives the command to measure the output power value of each combiner box 50 and 60, it sends the drive information to disconnect the detection switches of combiner boxes 50 and 60.

[0075] The total error loss of the combiner box is obtained by summing the output deviation values ​​and the total drop value.

[0076] Based on the total error loss of the combiner boxes and the number of combiner boxes, the output loss of each combiner box is obtained by evenly distributing the losses. The output deviation value of each combiner box is then corrected based on the output loss of each combiner box to obtain the corrected output power value.

[0077] Determine if there is a minimum output power value for each combiner box after calibration. If so, obtain the combiner box number corresponding to the minimum value and mark it as the abnormal combiner box number. This allows verification of the accurate combiner box number where the "fault descent" occurred should a "fault descent" situation arise subsequently.

[0078] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, the method for actually measuring power loss includes:

[0079] Step 201: Install detection switches K11, K12, K13, and K14 in the series circuit between the solar cells 11, 12, 13, 14, and 15 of a single solar unit module, such as solar unit module 10. Each solar cell has two adjacent switches. Each solar cell is connected to the IV detection device via a disconnect switch array circuit.

[0080] Step 202: When actually measuring power loss, the detection controller controls the two adjacent switches of each solar unit to be disconnected, and controls the disconnection switch array to connect each solar unit individually to the IV detection device. After connecting to the IV detection device, the output power of each solar unit is detected and obtained by the IV detection device.

[0081] Step 203: Sum the output power of each solar cell to obtain the component and measured power of a single solar cell group.

[0082] Step 204: Control the two adjacent switches of each solar unit to turn off through the detection controller, and connect the single group of solar unit modules to the IV detection device to obtain the group measurement power of the single group of solar unit modules.

[0083] Step 205: Obtain and measure the difference between the power and the group measured power, and obtain the actual measured power loss based on the difference and the component and measured power.

[0084] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, the step of obtaining the power value of each solar cell in the solar cell module includes:

[0085] The output power of each solar cell is obtained using the method in step 202.

[0086] like Figure 3 As shown, the switching circuit includes:

[0087] A set of series-connected solar backup modules comprises multiple series-connected solar backup units. Each backup unit is disconnected via a backup switch. The backup switch is controlled by a detection controller. Lines connecting combiner boxes 50 and 60 are provided between each backup unit.

[0088] Taking solar cell module 10 as an example, each solar cell is connected in series with a backup solar cell unit 70. To prevent shading faults, the backup solar cell units 70 are arranged in a row along the delay direction A of the solar cell module 10 to prevent partial shading faults from becoming unsolvable. The backup solar cell unit 70 includes multiple backup solar cells 71, 72, ..., and each backup solar cell 71, 72 is connected to a switch K72, K73. The backup solar cell unit 70 is connected in series with the solar cell module 10 via K71.

[0089] Each solar backup unit module includes a parallel switching line. A parallel switching switch is installed in the parallel switching line. For example, solar unit module 10 includes a parallel switching line 19, which is connected to the lines between each solar cell via parallel switching switches K11-2, K12-2, and K13-2.

[0090] Each of the backup solar cells 71, 72, etc., is connected via a parallel switching circuit, with switches K71-1 and K72-1 and combiner box 50 in the circuit. The backup solar unit modules are connected in series with the solar unit modules.

[0091] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, the spare solar panels of the series-connected solar units are arranged sequentially along the arrangement direction of the solar unit panels. This prevents shading faults and solves the problem of small-area local shading.

[0092] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, it further includes:

[0093] If the power output of one or a predetermined number of solar panels is lower than a first predetermined percentage of the rated output power, the detection controller will connect one or a predetermined number of backup solar panel components to the original solar panel components, while simultaneously disconnecting the corresponding solar panel components, so that the backup components can replace the original solar panel components. The predetermined number is 70% to 80% of the total number of solar panel components.

[0094] If the number of units exceeds 70% to 80% of the set quantity, the original solar unit components will be disconnected from the combiner boxes 50 and 60 by the detection controller, and the spare solar unit components will be connected to the combiner boxes 50 and 60 as a whole, and the first abnormal information will be generated.

[0095] For example, if two solar cells 11 and 12 in the solar unit module 10 need to be replaced, then K71 and K72 are closed, K71-1 and K11-1 are opened and in an open circuit state, K72-1 is in a closed state, K13-2 is closed, and K11-2 is closed, thereby realizing a new series connection.

[0096] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, if the power value of all solar energy units is higher than a first set percentage of the rated output power and lower than a second set percentage of the rated output power, then the detection controller connects all the backup components of the solar energy units to the original solar energy unit components, and simultaneously disconnects the corresponding solar energy unit components, and generates a second abnormal information.

[0097] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, it further includes:

[0098] If the power value of one or a set number of solar units is higher than a first set percentage of the rated output power but lower than a second set percentage of the rated output power, the detection controller will connect the corresponding one or a set number of solar unit spare components to the original solar unit components, and at the same time disconnect the corresponding solar unit components, so that the solar unit spare components can replace the original solar unit components.

[0099] In one embodiment of the method for calculating the short-circuit current of a photovoltaic power station according to the present invention, step S106 includes: obtaining the short-circuit current of the photovoltaic power station at the photovoltaic access point using the per-unit method based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

[0100] Another aspect of the present invention provides a system for calculating the short-circuit current of a photovoltaic power plant.

[0101] The photovoltaic power station includes: multiple sets of solar unit modules 10, 20, 30, and 40; combiner boxes 50 and 60; an inverter 70; and a monitoring controller. The multiple sets of solar unit modules connected in series are fed into combiner boxes 50 and 60. The output lines of combiner boxes 50 and 60 are connected to the inverter 70. Each solar unit module is equipped with a backup solar unit, which is connected to its assigned solar unit module via a backup switching circuit.

[0102] The inverter output of the photovoltaic power station is connected to the main line via the overhead line length parameter and the transformer. The detection controller has multiple input terminals and multiple output terminals.

[0103] The system for calculating the short-circuit current of a photovoltaic power plant includes:

[0104] The inverter 70 reduction value acquisition unit is configured to acquire the reduction value of the output power of the inverter 70.

[0105] The combiner box 50 and 60 reduction value acquisition unit is configured to acquire the current reduction value of each group of solar unit modules connected to combiner boxes 50 and 60 as units.

[0106] The first power acquisition unit is configured to determine whether the current reduction value of each group is a fault reduction value based on the nominal series loss of each group. If not, it acquires the first output power value based on the actual measured power loss and the rated output power of the solar unit module of this group.

[0107] The second power acquisition unit, if configured to acquire the power value of each solar cell in the solar cell module, determines the defect characteristic type based on the power value of each solar cell, and drives the switching circuit according to the defect characteristic type to add a backup solar cell to its corresponding solar cell module.

[0108] The second output power value is obtained based on the actual measured power loss and the rated output power of the switched solar unit module.

[0109] The output power acquisition unit of combiner boxes 50 and 60 is configured to acquire the output power of each combiner box 50 and 60 based on the first output power value and / or the second output power value of each combiner box 50 and 60.

[0110] The maximum output power value acquisition unit is configured to obtain the maximum output power value of the total inverter 70 based on the sum of the output power of each combiner box 50 and 60.

[0111] The short-circuit current acquisition unit acquires the short-circuit current of the photovoltaic power station at the photovoltaic access point based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 this application.

Claims

1. A method for calculating the short-circuit current of a photovoltaic power station, characterized in that: The photovoltaic power station includes: multiple sets of solar unit modules, a combiner box, an inverter, and a detection controller; multiple sets of solar unit modules connected in series are respectively combined in the combiner box; the output line of the combiner box is connected to the inverter; each solar unit module is equipped with a backup solar unit, and the backup solar unit is connected to its assigned solar unit module through a backup switching circuit; The inverter output of the photovoltaic power station is connected to the main line through the overhead line length parameter and the transformer; the detection controller has multiple input terminals and multiple output terminals; The calculation method for the short-circuit current of the photovoltaic power station includes: Step S101: Obtain the reduction value of the inverter output power; Step S102: Using the combiner box as a unit, obtain the current reduction value of each group of solar unit modules connected to it; Step S103: Determine whether the current reduction value of each group is a fault reduction based on the nominal series loss of each group. If not, obtain the first output power value based on the actual measured power loss and the rated output power of the solar unit module of this group. Step S1031: If yes, obtain the power value of each solar unit in the solar unit assembly; determine the defect feature type based on the power value of each solar unit; drive the switching circuit based on the defect feature type to add the backup solar unit to its respective solar unit assembly. Step S1032: Obtain the second output power value based on the actual measured power loss and the rated output power of the switched solar unit module; Step S104: Obtain the output power of each combiner box based on the first output power value and / or the second output power value of each combiner box. Step S105: Obtain the maximum output power of the total inverter by summing the output power of each combiner box; Step S106: Obtain the short-circuit current of the photovoltaic power station at the photovoltaic access point based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

2. The calculation method according to claim 1, characterized in that, Step S101 further includes: The front-end reduction value is obtained based on the reduction value of the inverter output power and the inverter power loss rate; Measure the intermediate line loss from each combiner box to the inverter according to the arrangement of the combiner boxes; Based on the intermediate line loss of each combiner box and the front-end drop value, obtain the total drop value of all combiner boxes; Based on the measured output power and rated output value of each combiner box, obtain the output deviation value of each combiner box; install a combiner box detection switch in the connection line between each combiner box and the inverter; The output terminal of the detection controller is connected to the combiner box detection switch. When the input terminal of the detection controller receives an instruction to measure the output power value of each combiner box, it sends a drive message to the combiner box detection switch to disconnect it. The total error loss of the combiner box is obtained by summing the output deviation values ​​and the total drop value. Based on the total error loss of the combiner boxes and the number of combiner boxes, the output loss of each combiner box is obtained by evenly distributing the loss. Based on the output loss of each combiner box, the output deviation value of each combiner box is corrected to obtain the corrected output power value. Determine whether there is a minimum value in the output power of each combiner box after correction. If so, obtain the combiner box number information corresponding to the minimum value and mark it as abnormal combiner box number information, which is used as the abnormal combiner box number.

3. The calculation method according to claim 1, characterized in that, The method for actually measuring power loss includes: Step 201: Install a detection switch in the series circuit between each solar cell of a single solar cell module; each solar cell has two adjacent switches; the individual solar cell is connected to an IV detection device via a disconnect switch array circuit. Step 202: When actually measuring power loss, the detection controller controls the two adjacent switches of each solar cell to disconnect, and controls the disconnect switch array to connect each solar cell individually to the IV detection device. After connecting to the IV detection device, the output power of each solar cell is detected and obtained by the IV detection device. Step 203: Sum the output power of each solar cell to obtain the component and measured power of a single solar cell group; Step 204: Control the two adjacent switches of each solar unit to turn off through the detection controller, and connect the single group of solar unit components to the IV detection device to obtain the group measurement power of the single group of solar unit components; Step 205: Obtain the difference between the measured power and the group measured power, and obtain the actual measured power loss based on the difference and the component measured power.

4. The calculation method according to claim 3, characterized in that, The steps of obtaining the power values ​​of each solar cell in the solar cell module include: The output power of each solar cell is obtained using the method in step 202; The switching circuit includes: A set of series-connected solar unit backup components includes multiple series-connected solar backup units; each solar backup unit is disconnected by a backup switch; the backup switch is controlled by the detection controller; and a line connecting each solar backup unit to the combiner box is provided. Each solar cell module includes a parallel switching line; a parallel switching switch is provided in the parallel switching line; The spare component of the series-connected solar unit is connected to the solar unit component in series.

5. The calculation method according to claim 4, characterized in that, The spare components of the series-connected solar energy units are arranged sequentially along the arrangement direction of the solar energy unit components.

6. The calculation method according to claim 4 or 5, characterized in that, Also includes: If the power value of one or a predetermined number of solar energy units is lower than a first predetermined percentage of the rated output power, the detection controller will connect the corresponding one or a predetermined number of backup solar energy unit components to the original solar energy unit components, while simultaneously disconnecting the corresponding solar energy unit components, so that the backup solar energy unit components can replace the original solar energy unit components; the predetermined number is 70% to 80% of the number of solar energy unit components. If the number of units exceeds the set quantity of 70%~80%, the original solar unit component will be disconnected from the combiner box by the detection controller, and the entire spare solar unit component will be connected to the combiner box, and the first abnormal information will be generated.

7. The calculation method according to claim 4 or 5, characterized in that, Also includes: If the power value of all solar units is higher than the first set percentage of the rated output power but lower than the second set percentage of the rated output power, the detection controller will connect all the backup components of the solar units to the original solar unit components, while disconnecting the corresponding solar unit components and generating a second abnormal information.

8. The calculation method according to claim 4 or 5, characterized in that, Also includes: If the power value of one or a set number of solar units is higher than a first set percentage of the rated output power but lower than a second set percentage of the rated output power, the detection controller will connect the corresponding one or a set number of solar unit spare components to the original solar unit components, and at the same time disconnect the corresponding solar unit components, so that the solar unit spare components can replace the original solar unit components.

9. The calculation method according to claim 1, characterized in that, Step S106 includes: obtaining the short-circuit current of the photovoltaic power station at the photovoltaic access point using the per-unit method based on the maximum output power value, overhead line length parameters, transformer capacity, and transformer impedance.

10. A system for calculating the short-circuit current of a photovoltaic power station, characterized in that: The photovoltaic power station includes: multiple sets of solar unit modules, a combiner box, an inverter, and a detection controller; multiple sets of solar unit modules connected in series are respectively combined in the combiner box; the output line of the combiner box is connected to the inverter; each solar unit module is equipped with a backup solar unit, and the backup solar unit is connected to its assigned solar unit module through a backup switching circuit; The inverter output of the photovoltaic power station is connected to the main line through the overhead line length parameter and the transformer; the detection controller has multiple input terminals and multiple output terminals; The short-circuit current calculation system for the photovoltaic power station includes: An inverter derating value acquisition unit is configured to acquire the derating value of the inverter's output power. The combiner box reduction value acquisition unit is configured to acquire the current reduction value of each group of solar unit modules connected to the combiner box as a unit; The first power acquisition unit is configured to determine whether the current reduction value of each group is a fault reduction based on the nominal series loss of each group. If not, it acquires the first output power value based on the actual measured power loss and the calibrated output power of the solar unit module of this group. The second power acquisition unit is configured to acquire the power value of each solar cell in the solar cell assembly, and to obtain the defect feature type based on the power value of each solar cell, and to drive the switching circuit based on the defect feature type so that the backup solar cell is added to the solar cell assembly. The second output power value is obtained based on the actual measured power loss and the rated output power of the switched solar unit module; The combiner box output power acquisition unit is configured to acquire the output power of each combiner box based on the first output power value and / or the second output power value of each combiner box. The maximum output power value acquisition unit is configured to obtain the maximum output power value of the total inverter based on the sum of the output power of each combiner box. The short-circuit current acquisition unit acquires the short-circuit current of the photovoltaic power station at the photovoltaic access point based on the maximum output power value, the overhead line length parameter, and the transformer capacity and transformer impedance.

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