Optimization design method of photovoltaic power station

Abstract

The invention discloses an optimal design method of a photovoltaic power station. Local solar energy resources and design requirements are analyzed according to design specifications, and month-by-month horizontal plane-inclined plane radiation quantity conversion calculation, related photovoltaic module type selection and inverter type selection are carried out; determining the upper and lower limit values of the series connection number of the photovoltaic modules, and obtaining the optimized series connection number of the photovoltaic modules according to the solar resources of the place where the photovoltaic power station is located; determining the arrangement of photovoltaic modules, and determining the array spacing of the photovoltaic modules according to the topographic condition of the location of the photovoltaic power station; carrying out direct current and alternating current cable model selection, calculating corresponding cable length and carrying out photovoltaic power station site plane design; energy storage system configuration and optimization design are carried out based on the installed capacity and the operation mode of the photovoltaic power station, and the energy storage capacity is determined according to the grid-connected condition and the operation requirement of the photovoltaic power station. According to the invention, the array voltage and the output electric quantity of the photovoltaic array under the conditions of weak light and array shading are effectively improved, and the array power generation efficiency is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic power generation, and in particular relates to an optimization design method for a photovoltaic power station. Background Art

[0002] Through continuous technological innovation and policy support, photovoltaic power generation will play an increasingly important role in energy production and consumption. Currently, the design of solar photovoltaic power generation systems in industry engineering practice generally relies on engineering experience or the use of engineering software to assist in design. However, my country has a vast territory, complex terrain, and variable solar radiation resources. Furthermore, with the increasing deployment of energy storage in large-scale photovoltaic power generation, photovoltaic power station designs based on engineering experience or foreign design software are not ideal. Summary of the Invention

[0003] In response to the shortcomings of existing photovoltaic power station design technology, based on different types of photovoltaic power station types, grid-connected conditions and operating modes, and targeting scenarios with different radiation resources, different types of photovoltaic-energy storage power stations, and combining different intelligent control and maintenance methods, the present invention proposes an optimized photovoltaic power station design method and related optimization parameters. Compared with the photovoltaic power station design methods currently commonly used in the industry, this method has higher accuracy, wider scope of application and stronger practicality, and can serve as a demonstration reference for energy storage configuration, upgrading and transformation, and improvement of power generation efficiency of other similar existing photovoltaic power stations.

[0004] The present invention is implemented as follows: a method for optimizing the design of a photovoltaic power station, the method comprising the following steps:

[0005] (1) Obtain the infrastructure data of the photovoltaic power station, analyze the local solar energy resources and design requirements according to the design specifications, perform monthly horizontal-inclined radiation conversion calculations, and select relevant photovoltaic modules and inverters;

[0006] (2) Determine the upper and lower limits of the number of PV modules in series according to the design specifications, and optimize the number of PV modules in series and parallel according to the solar energy resources at the location of the PV power station;

[0007] (3) Determine the arrangement of photovoltaic modules according to the design specifications, and determine the array spacing of photovoltaic modules according to the terrain conditions of the photovoltaic power station location;

[0008] (4) Select DC and AC cables and calculate the corresponding cable lengths and the plane design of the photovoltaic power station site according to the design specifications;

[0009] (5) Configure and optimize the design of the energy storage system based on the installed capacity and operation mode of the photovoltaic power station, and determine the energy storage capacity according to the grid connection conditions and operation requirements of the photovoltaic power station.

[0010] Preferably, the design specification is the "Design Specification for Photovoltaic Power Stations" (GB50797-2012).

[0011] Preferably, the infrastructure data includes the construction location, type, installed capacity and grid connection method of the photovoltaic power station.

[0012] Preferably, in step (2), the upper and lower limits of the number N of photovoltaic modules connected in series and parallel are defined as:

[0013]

[0014] Where: K v —Open circuit voltage temperature coefficient of photovoltaic modules; K' v — working voltage temperature coefficient of photovoltaic modules; N—number of photovoltaic modules in series (N is rounded up); t—limit low temperature under working conditions of photovoltaic modules (℃), t'—limit high temperature under working conditions of photovoltaic modules (℃), V dcmax —The maximum DC input voltage allowed by the inverter (V), V mpptmax —Inverter MPPT maximum voltage (V), V mpptmin —Inverter MPPT voltage minimum value (V), V oc —Open circuit voltage of photovoltaic modules (V), V pm —The operating voltage of the photovoltaic module (V) is: where the standard operating temperature of the module is 25°C;

[0015] The optimized number of photovoltaic modules connected in series and parallel Nr is:

[0016]

[0017] Among them, N r To optimize the number of series connections, N G Calculate the number of series connections for the national standard, H a is the annual solar radiation resource, and T is the local minimum temperature.

[0018] Preferably, in step (3), the terrain includes ordinary ground with a site slope of less than 2 degrees, mountainous land, and industrial and commercial roofs with a site slope of less than 2 degrees;

[0019] The array spacing of the photovoltaic modules on the ordinary ground is:

[0020]

[0021] Where D is the array spacing, L is the north-south length of the photovoltaic array, and β is the inclination angle of the photovoltaic array. is the local latitude angle, and β is classified according to the solar radiation resources of the photovoltaic power station location. The first type of resource area is generally The second type of resource area is The three types of resource areas are generally

[0022] The array spacing of the photovoltaic modules in the mountain area is:

[0023]

[0024] Where D is the array spacing, θ is the site slope, which is positive when it is lower in the south and higher in the north, and negative when it is higher in the south and lower in the north; D' is the projection length of the array in the north-south direction; τ is the local shadow magnification; H' is the height difference between the front and rear ends of the array;

[0025] The array spacing of the industrial and commercial roof is:

[0026]

[0027] Where D is the array spacing, L is the north-south length of the photovoltaic array, is the local latitude angle.

[0028] Preferably, in step (3), if the photovoltaic power station generates all electricity and is connected to the grid, a full-coverage form can be adopted, that is, the array spacing of the photovoltaic modules is D=0.

[0029] Preferably, in step (5), if the photovoltaic power station is operated off-grid and forms an independent microgrid with the energy storage system and the DC load, the energy storage capacity Q of the battery pack is b for:

[0030]

[0031] Among them, P i is the total AC / DC load (kW), h i is the load working hours, η is the efficiency of the energy storage system, D od is the depth of discharge of the battery.

[0032] Preferably, in step (5), if the photovoltaic power station is connected to the grid, the energy storage capacity Q of the battery pack is b for:

[0033]

[0034] Among them, Q B : battery pack capacity (kWh), P: rated output power of photovoltaic power station (kW), h: energy storage adjustment width (h). When scheduling photovoltaic power output, the adjustment width is 1 to 4 hours. D: energy storage adjustment depth (%), η: energy storage system charge and discharge efficiency (%), D od : Depth of discharge (%) of the energy storage system, ranging from 65% to 90% based on different types of batteries. The charge and discharge control mode is determined by analyzing the local power peak and valley time distribution and electricity prices.

[0035] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0036] (1) The optimization calculation method of the number of series-connected modules in the photovoltaic array of the present invention can effectively improve the array voltage and output power of the photovoltaic array under weak light and array shading conditions, thereby improving the array power generation efficiency.

[0037] (2) The optimization calculation method for array spacing in the present invention can effectively improve the power generation per unit area of a photovoltaic power station, and is very suitable for use in projects with limited land resources such as industrial and commercial rooftop photovoltaics.

[0038] (3) The calculation method for the energy storage system capacity configuration in the present invention can realize the translation of photovoltaic power generation on the time coordinate, so that it can participate in power peak regulation, and significantly improve the system's power generation income by formulating a reasonable photovoltaic-energy storage control strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the solar radiation calculation and power generation estimation in the embodiment of the present invention;

[0040] Figure 2 is the calculation of the number of photovoltaic modules connected in series in the embodiment of the present invention;

[0041] Figure 3 The output voltages of different series numbers in the embodiments of the present invention are different;

[0042] Figure 4 is a schematic diagram of the photovoltaic array arrangement according to an embodiment of the present invention;

[0043] Figure 5 It is the simulated output curve of the photovoltaic-energy storage system. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] An embodiment of the present invention discloses a method for optimizing the design of a photovoltaic power station, the method comprising the following steps:

[0046] (1) Obtain the infrastructure data of the photovoltaic power station (including the construction site, type, installed capacity, and grid connection method of the photovoltaic power station). In this embodiment, the construction site of the photovoltaic power station is located in Xiaguanying Town, Yuzhong County, Lanzhou City (36.0N, 104.0E). The power station type is a rooftop photovoltaic power station. There is no need to rent the roof. The estimated installed capacity of the power station is 100kW, and the grid connection method is full access to the grid. According to the design specifications of the "Design Specifications for Photovoltaic Power Stations" (GB50797-2012), the local solar energy resources (such as Figure 1 As shown in the figure) and design requirements, monthly horizontal plane-tilt conversion calculations, relevant PV module selection and inverter selection are performed.

[0047] In the embodiment of the present invention, based on the estimation results of solar radiation at different angles, the photovoltaic module is selected to be 450W and the inverter is selected to be 100kW.

[0048] (2) Determine the upper and lower limits of the number of photovoltaic modules in series according to the design specifications, and optimize the number of photovoltaic modules in series and parallel according to the solar energy resources at the location of the photovoltaic power station.

[0049] In step (2), the upper and lower limits of the number of photovoltaic modules in series are calculated according to the "Design Specifications for Photovoltaic Power Stations" (GB50797-2012), as shown in the following formula:

[0050]

[0051] Where: K v —Open circuit voltage temperature coefficient of photovoltaic modules; K' v — working voltage temperature coefficient of photovoltaic modules; N—number of photovoltaic modules in series (N is rounded up); t—limit low temperature under working conditions of photovoltaic modules (℃), t'—limit high temperature under working conditions of photovoltaic modules (℃), V dcmax —The maximum DC input voltage allowed by the inverter (V), V mpptmax —Inverter MPPT maximum voltage (V), V mpptmin —Inverter MPPT voltage minimum value (V), V oc —Open circuit voltage of photovoltaic modules (V), V pm —The operating voltage of the photovoltaic module (V) is: where the standard operating temperature of the module is 25℃.

[0052] Based on the selected PV panels and inverter electrical parameters, such as Figure 2 As shown in the figure, the number of photovoltaic modules connected in series calculated according to the national standard is 21.

[0053] At the same time, the annual solar radiation resources at the power station site are approximately 1422kWh m -2, and the annual minimum temperature is > -20℃. Considering the comprehensive power generation efficiency and inverter electrical parameters, the number of components in series and parallel should be 1.1N, that is, 23 photovoltaic modules are connected in series. Given that the total installed capacity of the photovoltaic power station is 100kW, in order to ensure the MPPT tracking effect, it is optimized to connect 22 photovoltaic modules in series into 10 strings. Based on the string-parallel connection result, the actual installed capacity of the power station is 99kW.

[0054] Based on this optimization method, the output voltage of the photovoltaic module is low under weak light conditions and cannot reach the starting voltage of the inverter, such as Figure 3 As shown in the figure, by connecting multiple modules in series, the output voltage of a string can be increased under weak light conditions, thereby effectively increasing the output power of the inverter AC end of the photovoltaic array under weak light conditions and array shading, thereby improving the array's power generation efficiency.

[0055] (3) Design the photovoltaic module layout according to the "Design Specifications for Photovoltaic Power Stations" (GB50797-2012), and optimize the boundary conditions (array spacing of photovoltaic modules) based on the terrain conditions of the photovoltaic power station. Since the power station in the embodiment is a rooftop photovoltaic power station, the site slope is less than 2 degrees and the site rent is less than 0.75 yuan / m 2 / year, use the following formula to calculate the photovoltaic array spacing

[0056]

[0057] Where D is the array spacing, L is the north-south length of the photovoltaic array, is the local latitude angle.

[0058] The calculated PV array spacing is 1.35m. The PV module tilt angle is 33°. The area occupied by a single PV module string is 67.95 square meters. The total area occupied by the PV power station is 679.54 square meters. The annual power generation per square meter of rooftop is calculated as 189.39kWh / m based on an effective sunshine time of 1300h. 2 .

[0059] Compared with the unoptimized PV array spacing calculation method, the PV module tilt angle is 33°, the unoptimized PV array spacing is calculated to be 2.40m, the area occupied by a single PV module string is 91.98 square meters, and the total area occupied by the PV power station is 919.78 square meters. The annual power generation per square meter of roof is calculated to be 139.92kWh / m based on 1300h of effective sunshine time. 2 .

[0060] It can be seen that the power station optimization design method provided by the present invention can effectively improve the power generation per unit area of the photovoltaic power station, and is very suitable for use in projects with tight land resources and high rents, such as industrial and commercial rooftop photovoltaics.

[0061] (4) Select DC and AC cables according to design specifications and calculate the corresponding cable lengths and the plane design of the photovoltaic power station site.

[0062] According to the calculation results of the above steps and in accordance with the "Design Specifications for Photovoltaic Power Stations" (GB50797-2012), select DC and AC cables and calculate the corresponding cable lengths, and then carry out the plane design of the photovoltaic power station site, such as Figure 4 shown.

[0063] (5) Configure and optimize the design of the energy storage system based on the installed capacity and operation mode of the photovoltaic power station, and determine the energy storage capacity according to the grid connection conditions and operation requirements of the photovoltaic power station.

[0064] The installed capacity of the grid-connected power station is 99kW. To maximize the benefits of the photovoltaic power station, a lithium battery energy storage system is configured. The operating goal is to dispatch photovoltaic power output. The energy storage system capacity has an energy storage adjustment width of 2 hours. Based on the comprehensive characteristics of the energy storage system, the energy storage adjustment depth is determined to be 100%, the energy storage system efficiency is determined to be 95%, and the discharge depth is determined to be 85%. The energy storage capacity optimization calculation is performed:

[0065]

[0066] Among them, Q B : battery pack capacity (kWh);

[0067] P: Rated output power of photovoltaic power station (kW);

[0068] h: Energy storage regulation width. Typically, the width used for smoothing power stations is 0.05 to 0.2 hours. The width used for peak shifting and valley filling should be no greater than the local solar radiation peak hours. The reference range is 1 to 4 hours.

[0069] D: Energy storage regulation depth (%), usually used to smooth the power station output power regulation depth of 10-20%, the depth of scheduling PV module output is 100%;

[0070] η: Energy storage power station system efficiency (%);

[0071] D od : Battery discharge depth (%).

[0072] The optimized energy storage system configuration capacity is calculated to be 245kWh. The simulated output curve of the photovoltaic-energy storage system configured according to this energy storage capacity is as follows: Figure 5 As shown in the figure, the energy storage system is used to improve the dispatchability of effective power generation. At the same time, given the large differences in the time distribution of power peaks and valleys and electricity prices, the energy storage system is used during the peak period of photovoltaic power generation. The energy storage system can be used to shift photovoltaic power generation on the time coordinate, allowing it to participate in power peak regulation and optimize the economic efficiency of system operation.

[0073] Based on the peak-valley electricity prices for photovoltaic power generation in Gansu Province, the on-grid price for the valley period from 9:00 AM to 5:00 PM is 0.1539 yuan / kWh, and the on-grid price for the peak period from 5:00 PM to 11:00 PM is 0.4617 yuan / kWh. Based on these prices, the photovoltaic-energy storage power station's operation control mode is established, with photovoltaic output prioritizing the energy storage system before supplying power to the grid. The energy storage system is charged and discharged once a day. This photovoltaic-energy storage system generates a daily power generation revenue of 124.9452 yuan, significantly higher than the 60.9444 yuan daily revenue of a photovoltaic power station without energy storage. The calculation results show that the energy storage system configured based on this capacity calculation method can effectively improve the economic benefits of the entire photovoltaic-energy storage system through reasonable charge and discharge control.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A photovoltaic power station optimization design method, characterized in that: The method comprises the following steps: (1) Obtain the infrastructure data of the photovoltaic power station, analyze the local solar energy resources and design requirements according to the design specifications, perform monthly horizontal-inclined radiation conversion calculations, and select relevant photovoltaic modules and inverters; (2) Determine the upper and lower limits of the number of PV modules in series according to the design specifications, and optimize the number of PV modules in series and parallel according to the solar energy resources at the location of the PV power station; (3) Determine the arrangement of photovoltaic modules according to the design specifications, and determine the array spacing of photovoltaic modules according to the terrain conditions of the photovoltaic power station location; (4) Select DC and AC cables and calculate the corresponding cable lengths and the plane design of the photovoltaic power station site according to the design specifications; (5) Configure and optimize the energy storage system based on the installed capacity and operating mode of the photovoltaic power station, and determine the energy storage capacity based on the grid connection conditions and operating requirements of the photovoltaic power station; The design specification is the "Design Specification for Photovoltaic Power Stations" (GB50797-2012).

2. The method according to claim 1, wherein The infrastructure data includes the construction location, type, installed capacity and grid connection method of the photovoltaic power station.

3. The method according to claim 1, wherein In step (2), the upper and lower limits of the number N of photovoltaic modules connected in series and parallel are defined as: Where: K v —Open circuit voltage temperature coefficient of photovoltaic modules; K' v — working voltage temperature coefficient of photovoltaic modules; N—number of photovoltaic modules in series (N is rounded up); t—limit low temperature under working conditions of photovoltaic modules (℃), t'—limit high temperature under working conditions of photovoltaic modules (℃), V dcmax —The maximum DC input voltage allowed by the inverter (V), V mpptmax —Inverter MPPT maximum voltage (V), V mpptmin —Inverter MPPT voltage minimum value (V), V oc —Open circuit voltage of photovoltaic modules (V), V pm —The operating voltage of the photovoltaic module (V) is: where the standard operating temperature of the module is 25°C; The optimized number of photovoltaic modules connected in series and parallel Nr is: Among them, N r To optimize the number of series connections, N G Calculate the number of series connections for the national standard, H a is the annual solar radiation resource, and T is the local minimum temperature.

4. The method according to claim 1, wherein In step (3), the terrain includes ordinary ground with a site slope of less than 2 degrees, mountainous land, and industrial and commercial roofs with a site slope of less than 2 degrees; The array spacing of the photovoltaic modules on the ordinary ground is: Where D is the array spacing, L is the north-south length of the photovoltaic array, and β is the inclination angle of the photovoltaic array. is the local latitude angle, and β is classified according to the solar radiation resources of the photovoltaic power station location. The first type of resource area is generally The second type of resource area is The three types of resource areas are generally The array spacing of the photovoltaic modules in the mountain area is: Where D is the array spacing, θ is the site slope, which is positive when it is lower in the south and higher in the north, and negative when it is higher in the south and lower in the north; D' is the projection length of the array in the north-south direction; τ is the local shadow magnification; H' is the height difference between the front and rear ends of the array; The array spacing of the industrial and commercial roof is: Where D is the array spacing, L is the north-south length of the photovoltaic array, is the local latitude angle.

5. The method according to claim 4, wherein In step (3), if the photovoltaic power station generates all electricity and is connected to the grid, a full-coverage form can be adopted, that is, the array spacing of the photovoltaic modules is D=0.

6. The method according to claim 1, wherein In step (5), if the photovoltaic power station is off-grid and forms an independent microgrid with the energy storage system and DC load, the energy storage capacity of the battery group Q b for: Among them, P i is the total AC / DC load (kW), h i is the load working hours, η is the efficiency of the energy storage system, D od is the depth of discharge of the battery.

7. The method according to claim 1, wherein In step (5), if the photovoltaic power station is connected to the grid, the energy storage capacity of the battery group Q b for: Among them, Q B : battery pack capacity (kWh), P: rated output power of photovoltaic power station (kW), h: energy storage adjustment width (h), D: energy storage adjustment depth (%), η: energy storage system charge and discharge efficiency (%), D od : Discharge depth of energy storage system (%).

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