String design method and device for household distributed photovoltaic

Abstract

The invention relates to the technical field of photovoltaic power generation, and discloses a string design method for household distributed photovoltaic, which is characterized by comprising the following steps: establishing a generating capacity evaluation theoretical model; calculating a power generation loss rate by using the power generation evaluation theoretical model based on the related electrical parameters of the unmixed and mixed photovoltaic modules; if the power generation loss rate does not accord with a first preset constraint condition, adjusting the number of unmixed and mixed photovoltaic modules according to the series number of the photovoltaic modules; and according to the adjusted related electrical parameters of the unmixed and mixed photovoltaic modules, returning to the step of calculating the power generation loss rate by using the power generation evaluation theoretical model until the power generation loss rate meets a first preset constraint condition.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a method and device for designing a household distributed photovoltaic string. Background Art

[0002] With the rapid development of photovoltaic power generation technology, distributed photovoltaic installed capacity has occupied a significant market share in the photovoltaic industry. Household distributed photovoltaic is an important application scenario of distributed photovoltaic (hereinafter referred to as household scenario). Household scenarios are complex and diverse, and face the following problems:

[0003] (1) The existing string design does not take into account the string mixing requirements on the north and south slopes and does not meet the business development needs.

[0004] (2) The photovoltaic power station simulation software cannot directly simulate the impact of string mixing on power generation.

[0005] (3) The mixing effect is difficult to monitor and quantitatively analyze.

[0006] How to rationally research and develop a set of evaluation and calculation methods to measure the impact of string and mixed string on power generation, reduce the problems of low efficiency and insufficient accuracy caused by traditional string and mixed string design relying on manual experience, and fail to fully utilize existing space resources, thereby reducing power generation benefits, has become a technical problem that needs to be solved urgently. Summary of the Invention

[0007] In view of this, the present invention provides a method and device for designing a group string for household distributed photovoltaics to solve the problem of how to accurately design group strings and mixed strings.

[0008] In a first aspect, the present invention provides a method for designing a string for household distributed photovoltaics, comprising: establishing a theoretical model for power generation assessment; calculating the power generation loss rate using the theoretical model for power generation assessment based on relevant electrical parameters of unmixed and mixed photovoltaic modules; if the power generation loss rate does not meet a first preset constraint, adjusting the number of unmixed and mixed photovoltaic modules according to the number of photovoltaic modules in series; and returning to the step of "calculating the power generation loss rate using the theoretical model for power generation assessment" based on the adjusted relevant electrical parameters of the unmixed and mixed photovoltaic modules, until the power generation loss rate meets the first preset constraint.

[0009] In an optional embodiment, a power generation evaluation theoretical model is established for calculating the power generation of a photovoltaic power station. The power generation calculation process of a photovoltaic power station includes: calculating the effective power generation of all mixed-string photovoltaic modules based on the module efficiency coefficient; calculating the effective power generation of all unmixed-string photovoltaic modules based on the module efficiency coefficient; and taking the sum of the effective power generation of all mixed-string photovoltaic modules and the effective power generation of all unmixed-string photovoltaic modules as the power generation of the photovoltaic power station.

[0010] In an optional embodiment, the calculation formula for establishing the power generation evaluation theoretical model is:

[0011]

[0012] I mp =η inv ·G·A

[0013] Among them, E' p is the power generation of the power station; η inv is the component efficiency coefficient; V′ mp is the operating voltage of the mixed string photovoltaic modules; I' mp is the working current of the mixed series photovoltaic modules; V mp is the operating voltage of the unmixed PV modules; I mp is the operating current of the unmixed PV module; G is the unit irradiation intensity; A is the area of the PV module.

[0014] In an optional embodiment, the process of calculating the power generation loss rate includes: calculating the sum of the power generation of photovoltaic modules without mixed strings in different orientations based on the module efficiency coefficient; taking the ratio of the power generation of the photovoltaic power station to the power generation of photovoltaic modules without mixed strings in different orientations as the power generation efficiency of the photovoltaic power station; and taking the difference between the value 1 and the power generation efficiency of the photovoltaic power station as the power generation loss rate.

[0015] In an optional embodiment, for each slope, the process of adjusting the number of non-mixed and mixed photovoltaic modules includes: establishing a second preset constraint based on the maximum DC input voltage allowed by the inverter, the open-circuit voltage of the photovoltaic module, and the open-circuit voltage temperature coefficient of the photovoltaic module; establishing a third preset constraint based on the minimum MPPT voltage of the inverter, the maximum MPPT voltage of the inverter, the operating voltage of the photovoltaic module, and the open-circuit voltage temperature coefficient of the photovoltaic module; and adjusting the number of non-mixed and mixed photovoltaic modules based on the second preset constraint and the third preset constraint.

[0016] In an optional implementation, the calculation formula for the second preset constraint condition is:

[0017]

[0018] Where N is the number of photovoltaic modules in series; V dcmax V is the maximum DC input voltage allowed by the inverter; oc is the open circuit voltage of the photovoltaic module; K v is the open circuit voltage temperature coefficient of the photovoltaic module; t is the extreme low temperature under the working conditions of the photovoltaic module;

[0019] The calculation formula for the third preset constraint condition is:

[0020]

[0021] Where t' is the extreme high temperature under the working conditions of the photovoltaic module; V dcmax V is the maximum DC input voltage allowed by the inverter; mpptmax is the maximum value of the inverter MPPT voltage; V mpptmin is the minimum value of the inverter MPPT voltage; V pm is the operating voltage of the photovoltaic module.

[0022] In a second aspect, the present invention provides a device for designing a string of household distributed photovoltaics, the device comprising: a model building module for establishing a theoretical model for power generation assessment; a calculation module for calculating the power generation loss rate based on the relevant electrical parameters of unmixed and mixed photovoltaic modules and the theoretical model for power generation assessment; an adjustment module for adjusting the number of unmixed and mixed photovoltaic modules according to the number of photovoltaic modules in series if the power generation loss rate does not meet the first preset constraint condition; and a loop adjustment module for returning to the step of "calculating the power generation loss rate using the theoretical model for power generation assessment" according to the adjusted relevant electrical parameters of the unmixed and mixed photovoltaic modules until the power generation loss rate meets the first preset constraint condition.

[0023] In a third aspect, the present invention provides a computer device comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to execute the method for designing a string for household distributed photovoltaics according to the first aspect or any corresponding embodiment thereof.

[0024] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method for designing a string for household distributed photovoltaics according to the first aspect or any corresponding embodiment thereof.

[0025] In a fifth aspect, the present invention provides a computer program product comprising computer instructions for causing a computer to execute the method for designing household distributed photovoltaic strings according to the first aspect or any corresponding embodiment thereof.

[0026] This application provides a method for evaluating and calculating the impact of string and string mixing on power generation. This method leverages the meteorological prior data built into the PVsyst software to simulate string and string mixing for residential applications with north-south slopes. It then defines a quantitative analysis method for the effects of string and string mixing, and ultimately develops a set of standards tailored to actual applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 is an equivalent circuit diagram of a single diode model of a photovoltaic module monomer according to an embodiment of the present invention;

[0029] Figure 2 is a flow chart of a method for designing household distributed photovoltaic strings according to an embodiment of the present invention;

[0030] Figure 3 is a flow chart of another method for designing household distributed photovoltaic strings according to an embodiment of the present invention;

[0031] FIG4(a) and FIG4(b) are respectively diagrams showing voltage and current characteristics of a photovoltaic module according to an embodiment of the present invention;

[0032] Figure 5 This is a bar chart of annual irradiation hours for sunrooms in Zhengzhou at different orientations according to an embodiment of the present invention;

[0033] Figure 6 Schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0035] According to an embodiment of the present invention, an embodiment of a method for designing a string for household distributed photovoltaics is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings 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 can be executed in an order different from that shown here.

[0036] In photovoltaic power generation systems, string and mixed string design are key strategies for optimizing power generation efficiency. String design focuses on component combinations, allowing photovoltaic modules with different power, voltage, and current to be paired into strings. Its core purposes are multiple: first, to adapt to the inverter input requirements and accurately meet the system's adaptation needs for voltage and current; second, to leverage the complementary advantages of components to improve power generation efficiency under complex lighting conditions; third, to disperse the risk of failure and enhance the overall reliability of the system; fourth, standardized string types simplify the installation process and facilitate subsequent maintenance and inspection. Mixed string design takes a different approach, characterized by the different orientations of components within the same string. In household scenarios, the asymmetric structure of the building results in uneven layout of components on the north and south slopes, and differences in azimuth and inclination angles further differentiate power generation efficiency. Mixed string operation can break through limitations, efficiently integrate components on the north and south slopes, convert idle rooftop space into installed capacity, and maximize the site's power generation potential.

[0037] In household scenarios, the components on the north and south slopes have different azimuths and inclinations. At the same time, buildings are often not designed to be symmetrical from north to south, resulting in inconsistent numbers of components on the north and south slopes. Therefore, the power generation efficiency of individual components on the south and north slopes is different, so string and mixed string operations are often performed.

[0038] This embodiment provides a string design method for household distributed photovoltaics, which is used in household scenarios. The method can use the meteorological prior data built into the PVsyst software to perform string and mixed string simulation considering the north and south slopes for household scenarios, and then define a quantitative analysis method for string and mixed string effects, and finally formulate a set of standards for actual business. Specifically, this embodiment can solve the following problems: 1. Standardization of design schemes: unify design rules to eliminate scheme differences caused by human subjectivity. 2. Accurate control of losses: Accurately control power generation losses caused by string (mixed string) based on the acceptable loss range. 3. Optimal economic efficiency: maximize the use of photovoltaic construction in household scenarios, increase installed capacity, and achieve better economic benefits for owners, investors, and power grids.

[0039] The following describes the design principles of photovoltaic strings:

[0040] (1) Physical (electrical) characteristics of a single photovoltaic module

[0041] Photovoltaic cells (also known as "photovoltaic modules" in engineering) use the photovoltaic effect of semiconductor PN junctions to convert light energy into electrical energy. As the smallest power generation unit in a photovoltaic system, accurately determining its electrical behavior is the basis for further analysis of photovoltaic array characteristics. Due to its advantages such as simple calculation and reasonable accuracy, the single diode model is widely used. Figure 1 The figure shows the equivalent circuit diagram of the single-diode model of a photovoltaic cell, which consists of a photocurrent source, a diode, and series-parallel resistors.

[0042] In a photovoltaic string, the current of the i-th module is recorded as Ii , voltage is recorded as V i According to Kirchhoff's current law, the output characteristic equation of the single diode model of the photovoltaic module is:

[0043] I i =I ph -I d -I p (1)

[0044] Where, I i is the output current of the photovoltaic cell, I ph is the photocurrent related to the irradiation intensity, I p is the leakage current generated by the parallel resistor shunt, I d Represents the current flowing through the diode, which is proportional to the reverse saturation current of the diode, I ph , I d and I p The expressions are as follows:

[0045]

[0046]

[0047]

[0048] Where G is the irradiance (1000W / m 2 ); T is the photovoltaic cell temperature; G STC and T STC They are the irradiance under STC (1000W / m 2 ) and temperature (25°C); I pv.stc is the photocurrent under STC conditions (A); K ISC is the short-circuit temperature coefficient of the photovoltaic cell; I0 is the reverse saturation current of the diode (A); R s and R p are the series and parallel resistances (Ω); V i represents the output voltage of the photovoltaic cell, n represents the ideality factor of the diode; V t It represents the thermal voltage of the photovoltaic cell (V).

[0049] From equations (2) to (4), the output characteristic equation of the photovoltaic cell under the single diode model is obtained as follows:

[0050]

[0051] (2) Physical (electrical) characteristics of multiple photovoltaic modules

[0052] When multiple photovoltaic modules are connected in series, assuming a total of n photovoltaic cells, the final voltage, current, and power parameters are as follows based on the electrical characteristics:

[0053]

[0054] I total =min{I i} (7)

[0055]

[0056] Among them, V i , I i 、P i Represents the voltage (V), current (A), and power (W) of the i-th module in the photovoltaic array string; V total , I total 、P total Represents the total voltage (V), current (A), and power (W) of the PV array strings.

[0057] In summary, the total voltage of the string is equal to the sum of the voltages of all individual photovoltaic cells, the total current of the string is equal to the minimum value of all individual photovoltaic cells, and the power is the sum of the power of each individual photovoltaic cell. i The difference is small and can be considered to be approximately equal. However, the operating current of each single photovoltaic cell will vary greatly due to the influence of the factory material characteristics, actual installation inclination, radiation intensity, obstacles, temperature differences, etc. Therefore, in the string process, it is required that the current difference of each component is as small as possible and the number of components with large current is as small as possible to reduce the impact of the inconsistent current difference on the power generation of the power station.

[0058] Based on the above principles, Figure 2 This is a flow chart of the design method for household distributed photovoltaic strings, such as Figure 2 As shown, the string design method includes:

[0059] Step S1: Establish a theoretical model for power generation evaluation.

[0060] Optionally, a theoretical model for power generation assessment is established to calculate the power generation of a photovoltaic power station. The power generation calculation process of a photovoltaic power station includes: calculating the effective power generation of all mixed-string photovoltaic modules based on the module efficiency coefficient; calculating the effective power generation of all unmixed-string photovoltaic modules based on the module efficiency coefficient; and taking the sum of the effective power generation of all mixed-string photovoltaic modules and the effective power generation of all unmixed-string photovoltaic modules as the power generation of the photovoltaic power station.

[0061] Specifically, according to the curve relationship between irradiation intensity, current and voltage, the parameter index of the entire photovoltaic power station after string (mixed string) can be expressed by current and irradiation intensity, as shown in the following formula:

[0062]

[0063] I mp =η inv ·G·A (10)

[0064] Among them, E' p is the power generation of the power station (J); η inv is the component efficiency coefficient; V′ mp is the operating voltage of the mixed string photovoltaic modules (V); I' mp is the operating current of the mixed series photovoltaic modules (A); V mp is the operating voltage of the unmixed PV modules (V); I mp is the operating current of the unmixed photovoltaic module (A); G is the unit irradiance (J / m 2 ); A is the area of PV modules.

[0065] Step S2: Based on the relevant electrical parameters of the non-string mixed and mixed PV modules, the power generation loss rate is calculated using the power generation evaluation theoretical model.

[0066] Specifically, with the help of professional measuring instruments, the operating current, operating voltage and unit irradiation intensity of the non-mixed and mixed photovoltaic modules are measured, and the current power generation of the photovoltaic power station is calculated based on formulas (9) and (10).

[0067] To measure the effectiveness of string grouping (mixed string configuration), we define the ratio k of the power generation loss of the entire power station after string grouping (mixed string configuration) to the power generation of the entire power station without string grouping (mixed string configuration) as a quantitative standard for measurement. We define k as the power generation loss rate. The process of calculating the power generation loss rate includes: calculating the sum of the power generation of PV modules without mixed string configuration in different orientations based on the module efficiency coefficient; taking the ratio of the power generation of the PV power station to the power generation of PV modules without mixed string configuration in different orientations as the power generation efficiency of the PV power station; and taking the difference between the value 1 and the power generation efficiency of the PV power station as the power generation loss rate.

[0068] The formula for calculating the power generation loss rate is as follows:

[0069]

[0070]

[0071] Among them, E p The sum of the power generation of components in different orientation strings (mixed strings); E' p It is the sum of the power generation of modules without strings (mixed strings) in different orientations.

[0072] Therefore, the final expression of the formula k is as follows

[0073]

[0074] Step S3: If the power generation loss rate does not meet the first preset constraint condition, the number of non-mixed and mixed photovoltaic modules is adjusted according to the number of photovoltaic modules in series.

[0075] Specifically, Equation (13) shows that the power loss rate k of a power station after string (mixed string) connection is related to the number of components in the string (mixed string) connection and the irradiation intensity. Therefore, the power loss rate can be adjusted by adjusting the number of components in the string (mixed string) connection.

[0076] Optionally, the process of adjusting the number of non-mixed and mixed photovoltaic modules includes: establishing a second preset constraint based on the maximum DC input voltage allowed by the inverter, the open-circuit voltage of the photovoltaic module, and the open-circuit voltage temperature coefficient of the photovoltaic module; establishing a third preset constraint based on the minimum MPPT voltage of the inverter, the maximum MPPT voltage of the inverter, the operating voltage of the photovoltaic module, and the open-circuit voltage temperature coefficient of the photovoltaic module; and adjusting the number of non-mixed and mixed photovoltaic modules based on the second preset constraint and the third preset constraint.

[0077] Specifically, the process of stringing PV modules needs to take into account electrical matching, shadowing, safety standards, and the actual environment. According to the national standard GB 50797-2012 Photovoltaic Power Station Design Specification and its revised version, in a PV array, the electrical performance parameters of each PV module in the same PV module string should be kept consistent, and the number of PV modules connected in series should be calculated according to the following formula.

[0078]

[0079]

[0080] Where N is the number of photovoltaic modules in series (N is an integer); V dcmax is the maximum DC input voltage allowed by the inverter (V); V oc is the open circuit voltage of the photovoltaic module (V); K v is the open circuit voltage temperature coefficient of the photovoltaic module; t is the extreme low temperature under the working conditions of the photovoltaic module (℃); where t' is the extreme high temperature under the working conditions of the photovoltaic module (℃); V dcmax is the maximum DC input voltage allowed by the inverter (V); V mpptmax is the maximum value of the inverter MPPT voltage (V); V mpptmin is the minimum value of the inverter MPPT voltage (V); V pm is the operating voltage of the PV module (V).

[0081] Step S4: Based on the adjusted relevant electrical parameters of the non-mixed and mixed PV modules, return to the step of "calculating the power generation loss rate using the power generation evaluation theoretical model" until the power generation loss rate meets the first preset constraint condition.

[0082] Specifically, Figure 3 This is a specific flow chart of the string design method. Figure 3 In the process, when the house has two sides, a theoretical model for power generation assessment is established, and the power generation loss rate is calculated based on the number of PV strings in the current group. When the power generation loss rate does not meet the first preset constraint condition, the number of PV strings in the group is modified, and the power generation loss rate is calculated again and judged. This process is repeated until the power generation loss rate meets the first preset constraint condition.

[0083] Based on the above design method, this embodiment uses PVsyst software for simulation and design. The specific process is as follows:

[0084] 1. Use PVsyst software to collect relevant meteorological data to provide factual support for simulation.

[0085] 2. Analysis of the electrical characteristics of mixed PV panels in actual power plants. Data from a typical power plant on a single day (24 hours) in the database was selected to analyze the electrical characteristics of distributed PV panels for a residential application on a north-south, double-slope site. Figure 4(a) shows that the voltage difference after stringing the panels is minimal. In Figure 4(b), the current after mixing strings in different orientations in an actual power plant is the minimum of the currents in the two orientations.

[0086] Analysis of the electrical characteristics of mixed strings of PV modules in a simulated power station. Simulated string mixing curves were tracked and compared with actual string mixing results over three days (3 x 24 hours). PV module electrical characteristics were analyzed, and voltage, current, and power characteristics after string grouping (mixing) were collected. ① String (mixed string) voltage change: The voltage change after string mixing is minimal and can be approximately considered equal. ② String (mixed string) voltage change: The total circuit current after string mixing shifts toward the minimum current of a single module. Basic information of the experimental power station: North-south orientation, with 55 modules on the south slope and 35 on the north slope. String mixing configuration: MPPT1: 18 modules on the south slope + 18 modules on the south slope; MPPT2: 18 modules on the south slope + 0 modules; MPPT3: 18 modules on the north slope + 0 modules; MPPT4: 18 modules mixed (1 module on the south slope + 17 modules on the north slope) + 0 modules.

[0087] 3. The power generation loss of the power station before and after the string group (mixed string) is calculated through data simulation, and the theoretical design range is calculated according to formula (13).

[0088] 4. Conduct power plant string (mixed string) design experiments based on actual environments. ① Latitude variation: When the number of strings (mixed strings) on the north and south slopes is the same, the lower the latitude, the smaller the k value, indicating less power generation loss. ② Angle variation: When the number of strings (mixed strings) on the north and south slopes is the same and the latitude is the same, the smaller the angle with due north (azimuth 0°), the smaller the k value, indicating less power generation loss.

[0089] The specific parameters of the sun room power station in Zhengzhou, Henan are shown in Table 1 and Table 2. The specific parameters of the sun room power station in Yongzhou, Hunan are shown in Table 3 and Table 4.

[0090] In Tables 2 and 4, six loss percentages are compared with those without string mixing under the following PV module quantity settings:

[0091] (1) South 26, North 22, South 12 + South 12 / North 12 + Mixed 12 (South 2, North 10).

[0092] (2) South 26, North 22, South 17 + South 17 / Mixed 14 (South 9, North 5).

[0093] (3) South 26, North 22, South 16 + South 16 / Mixed 16 (South 10, North 6).

[0094] (4) South 32 North 28, South 10+South 10 / South 10+Mixed 10 (South 2 North 8) / North 10+North 10.

[0095] (5) South 32, North 28, South 12+South 12 / 0+Mixed 12 (South 8, North 4) / North 12+North 12.

[0096] (6) South 32 North 28, South 15 + South 15 / Mixed 15 (South 2 North 3) / North 15.

[0097] Table 1

[0098]

[0099]

[0100] Table 2

[0101]

[0102] Table 3

[0103] Zhengzhou, Henan <![CDATA[Annual irradiance intensity Kw*h / m 2 > Mixed string Mixed strings are normal Loss after mixing 180° South 1068 1037 97.1％ 2.9％ 0° North 1041 1037 99.7％ 0.3％ 225° Southwest 1064 1029 96.7％ 3.3％ Northeast 45° 1044 1029 98.5％ 1.5％ 240° southwest 1061 1026 96.7％ 3.3％ Northeast 60° 1047 1026 98.0％ 2.0％ 270° West 1054 1024 97.1％ 2.9％ 90° East 1054 1024 97.1％ 2.9％ 120° southeast 1061 1026 96.8％ 3.2％ 300° Northwest 1048 1026 98.0％ 2.0％ 135° Southeast 1063 1029 96.8％ 3.2％ 315° Northwest 1045 1029 98.5％ 1.5％

[0104] Table 4

[0105]

[0106]

[0107] From Table 3, Table 4, Figure 5 It can be seen that for the Henan Zhengzhou sunroom power station with a south 26 and north 22, the maximum number of mixed string components on the south slope is 8; when the number of mixed string components on the south slope is ≥9, the power generation loss is greater than 1%; for the Henan Zhengzhou sunroom power station with a south 32 and north 28, the maximum number of mixed string components on the south slope is 10; when the number of mixed string components on the south slope is 8, the power generation loss is less than 1%.

[0108] It can be seen from Tables 3 and 4 that for the Hunan Yongzhou sunroom power station with a south 26 and north 22, the maximum number of mixed string modules on the south slope is 8; when the number of mixed string modules on the south slope is ≥ 9, the power generation loss is <1%; for the Hunan Yongzhou sunroom power station with a south 32 and north 28, the maximum number of mixed string modules on the south slope is 10; when the number of mixed string modules on the south slope is 8, the power generation loss is <1%; under the same design conditions, the power generation loss of power stations in the southern region is smaller when there is mixed string.

[0109] Based on the above simulation experiments, design specifications were formed, as shown in Table 5. In Table 5, the first column lists common problems in the design process, and the second column lists the design specifications obtained after simulation verification. They can be used as a reference for subsequent string and mixed string design.

[0110] Table 5

[0111]

[0112]

[0113] This embodiment simulates string and string mixing for household applications, considering north-south slopes, then defines a quantitative analysis method for the effects of string and string mixing, and finally establishes a set of standards for actual business. This method improves the design accuracy of string and string mixing and increases the installed capacity of household scenarios. For example, in northern regions (e.g., Zhengzhou, Henan, 34° north latitude), when the power generation loss k is required to be less than 1%, the maximum number of south-slope string mixing components is 8. It can also adapt to a variety of complex project requirements, achieving good returns for owners, investors, and the power grid.

[0114] In this embodiment, a device for designing a household distributed photovoltaic string is provided, the device comprising:

[0115] Model building module, used to establish a theoretical model for power generation assessment;

[0116] A calculation module is used to calculate the power generation loss rate based on the relevant electrical parameters of the unmixed and mixed photovoltaic modules using a power generation evaluation theoretical model;

[0117] an adjustment module, configured to adjust the number of non-mixed and mixed photovoltaic modules according to the number of photovoltaic modules in series if the power generation loss rate does not meet the first preset constraint condition;

[0118] The cyclic adjustment module is used to return to the step of "calculating the power generation loss rate using the power generation evaluation theoretical model" according to the adjusted relevant electrical parameters of the unmixed and mixed photovoltaic modules until the power generation loss rate meets the first preset constraint condition.

[0119] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0120] The string design device for household distributed photovoltaics in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0121] An embodiment of the present invention further provides a computer device having the above-mentioned device for designing strings of household distributed photovoltaic systems.

[0122] See also Figure 6 , Figure 6 is a structural diagram of a computer device provided by an optional embodiment of the present invention, such as Figure 6 As shown, the computer device includes: one or more processors 10, memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components utilize different buses to communicate with each other and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in the memory or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Equally, multiple computer devices can be connected, and each device provides part of the necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Figure 6 A processor 10 is taken as an example.

[0123] The processor 10 may be a central processing unit, a network processor, or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit, a programmable logic device, or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic, or any combination thereof.

[0124] The memory 20 stores instructions that can be executed by at least one processor 10, so as to enable at least one processor 10 to execute the method shown in the above embodiment.

[0125] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and application programs required for at least one function; the data storage area may store data created based on the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0126] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0127] The computer device further includes an input device 30 and an output device 40. The processor 10, the memory 20, the input device 30 and the output device 40 may be connected via a bus or other means. Figure 6 The bus connection is taken as an example.

[0128] The input device 30 can receive input digital or character information and generate key signal input related to user settings and function control of the computer device, such as a touch screen, a keypad, a mouse, a trackpad, a touch pad, an indicator stick, one or more mouse buttons, a trackball, a joystick, etc. The output device 40 can include a display device, an auxiliary lighting device (e.g., an LED), and a tactile feedback device (e.g., a vibration motor). The above-mentioned display device includes but is not limited to a liquid crystal display, a light emitting diode, a display, and a plasma display. In some optional embodiments, the display device can be a touch screen.

[0129] The embodiment of the present invention also provides a computer-readable storage medium. The above-mentioned method according to the embodiment of the present invention can be implemented in hardware, firmware, or implemented as a computer code that can be recorded in a storage medium, or implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and downloaded through a network and will be stored in a local storage medium, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state drive, etc.; further, the storage medium can also include a combination of the above-mentioned types of memory. It can be understood that a computer, a processor, a microprocessor controller or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor or hardware, the method shown in the above embodiment is implemented.

[0130] A portion of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the form in which the computer program instruction exists in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc. Accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium that can be accessed by the computer.

[0131] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for designing a string for household distributed photovoltaic systems, characterized in that: The method comprises: Establish a theoretical model for power generation assessment; Based on the relevant electrical parameters of the non-string mixed and mixed PV modules, the power generation loss rate is calculated using the power generation evaluation theoretical model; If the power generation loss rate does not meet the first preset constraint condition, adjusting the number of non-mixed and mixed photovoltaic modules according to the number of photovoltaic modules in series; Based on the adjusted electrical parameters of the unmixed and mixed PV modules, the process returns to the step of "calculating the power generation loss rate using the power generation evaluation theoretical model" until the power generation loss rate meets the first preset constraint condition.

2. The method for designing household distributed photovoltaic strings according to claim 1, characterized in that: The power generation evaluation theoretical model is established to calculate the power generation of the photovoltaic power station. The power generation calculation process of the photovoltaic power station includes: Calculate the effective power generation of all PV panels in series based on the module efficiency coefficient; Calculate the effective power generation of all unmixed PV panels based on the module efficiency coefficient; The sum of the effective power generation of all mixed-string PV modules and the effective power generation of all unmixed-string PV modules is taken as the power generation of the PV power station.

3. The method for designing household distributed photovoltaic strings according to claim 2, characterized in that: The calculation formula for establishing the theoretical model for power generation evaluation is: I mp =the inv ·G·A Among them, E' p is the power generation of the power station; η inv is the component efficiency coefficient; V′ mp is the operating voltage of the mixed string photovoltaic modules; I' mp is the working current of the mixed series photovoltaic modules; V mp is the operating voltage of the unmixed PV modules; I mp is the operating current of the unmixed PV module; G is the unit irradiation intensity; A is the area of the PV module.

4. The method for designing household distributed photovoltaic strings according to claim 2, characterized in that: The process of calculating the power generation loss rate includes: Based on the module efficiency coefficient, calculate the sum of the power generation of PV modules with different orientations and no mixed strings; The ratio of the power generation of the photovoltaic power station to the power generation of the photovoltaic modules without mixed strings in different orientations is used as the power generation efficiency of the photovoltaic power station. The difference between the value 1 and the power generation efficiency of the photovoltaic power station is used as the power generation loss rate.

5. The method for designing household distributed photovoltaic strings according to claim 1, characterized in that: For each slope, the process of adjusting the number of unmixed and mixed PV panels includes: Establishing a second preset constraint condition based on a maximum DC input voltage allowed by the inverter, an open-circuit voltage of the photovoltaic module, and an open-circuit voltage temperature coefficient of the photovoltaic module; Establishing a third preset constraint condition based on the inverter MPPT voltage minimum value, the inverter MPPT voltage maximum value, the photovoltaic module operating voltage, and the photovoltaic module open circuit voltage temperature coefficient; Based on the second preset constraint condition and the third preset constraint condition, the number of non-string mixed and string mixed photovoltaic components is adjusted.

6. The method for designing household distributed photovoltaic strings according to claim 5, characterized in that: The calculation formula for the second preset constraint condition is: Where N is the number of photovoltaic modules in series; V dcmax V is the maximum DC input voltage allowed by the inverter; oc is the open circuit voltage of the photovoltaic module; K v is the open circuit voltage temperature coefficient of the photovoltaic module; t is the extreme low temperature under the working conditions of the photovoltaic module; The calculation formula for the third preset constraint condition is: Where t' is the extreme high temperature under the working conditions of the photovoltaic module; V dcmax V is the maximum DC input voltage allowed by the inverter; mpptmax is the maximum value of the inverter MPPT voltage; V mpptmin is the minimum value of the inverter MPPT voltage; V pm is the operating voltage of the PV panel.

7. A device for designing strings of household distributed photovoltaic systems, characterized in that: The device comprises: Model building module, used to establish a theoretical model for power generation assessment; A calculation module, configured to calculate a power generation loss rate based on relevant electrical parameters of the non-string-mixed and mixed-string photovoltaic modules and using the power generation evaluation theoretical model; an adjustment module, configured to adjust the number of non-mixed and mixed photovoltaic modules according to the number of photovoltaic modules in series if the power generation loss rate does not meet the first preset constraint condition; The cyclic adjustment module is used to return to the step of "calculating the power generation loss rate using the power generation evaluation theoretical model" based on the adjusted relevant electrical parameters of the unmixed and mixed photovoltaic modules until the power generation loss rate meets the first preset constraint condition.

8. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the string design method for household distributed photovoltaics according to any one of claims 1 to 6 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method for designing household distributed photovoltaic strings according to any one of claims 1 to 6.

10. A computer program product, characterized in that The method comprises computer instructions for causing a computer to execute the method for designing household distributed photovoltaic strings according to any one of claims 1 to 6.

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