Calculation method and optimization design method of annual power generation of offshore floating photovoltaic power generation system

Abstract

The present invention belongs to the technical field of photovoltaic power generation, and relates to a method for calculating the annual power generation of an offshore floating photovoltaic power generation system and an optimization design method. The annual power generation calculation method takes into account the influence of the motion characteristics of the floating platform on the layout of photovoltaic modules, and accurately calculates the specific changes in the inclination angle and azimuth angle of the photovoltaic modules before and after the rotation through the Euler angle of the dynamic characteristics of the floating platform, thereby calculating the irradiance attenuation factor caused by the rotation of the floating platform, and according to the total radiation of the inclined surface, the irradiance attenuation factor and the shielding effect of the front row of photovoltaic modules on the rear row, combined with the efficiency of the photovoltaic modules and the overall efficiency of the photovoltaic power generation system, the annual power generation of the offshore floating photovoltaic power generation system is calculated. The offshore floating photovoltaic power generation system is optimized and designed with maximizing the annual power generation and minimizing the total area of ​​the photovoltaic modules as the optimization goals. The present invention can improve the calculation accuracy of the annual power generation, effectively increase the annual power generation, and reduce the use of photovoltaic modules while maintaining the efficient operation of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic power generation, and relates to offshore floating photovoltaic power generation technology, and specifically, to an annual power generation calculation method and an optimization design method for an offshore floating photovoltaic power generation system. Background Art

[0002] With the rapid development of global power scale and the excessive consumption of non-renewable resources such as fossil fuels, the problem of greenhouse gas emissions is becoming increasingly serious. Therefore, it is an inevitable trend to use renewable resources (such as solar energy, wind energy, tidal energy, geothermal energy, biomass energy, etc.) to solve the energy crisis, among which the use of solar energy. Among them, photovoltaic (PV) power generation is the best solution to solve the power supply problem in remote areas.

[0003] Photovoltaic power generation includes land photovoltaic (LPV) power generation and floating photovoltaic (FPV) power generation. LPV power generation system needs to occupy a large amount of land, and with the emergence of dust accumulation and air pollution, the photovoltaic conversion efficiency of LPV power generation system is reduced. Compared with LPV power generation system, FPV power generation system is built on the sea surface. On the one hand, it can greatly save land use area and reduce the impact of dust on the conversion efficiency of photovoltaic modules; on the other hand, because the photovoltaic modules are covered on the water surface, the evaporation of water is reduced by 70%; on the other hand, the cooling effect of the water body and the influence of the wind speed on the sea surface can reduce the temperature of the photovoltaic modules during operation, solving the problem of low efficiency of photovoltaic cells under high temperature operation.

[0004] The floating photovoltaic power stations that have been developed so far are limited to waters with less environmental loads, such as inland waters or offshore bays. Due to environmental and landscape factors, the area of ​​such waters is difficult to meet the development volume of photovoltaic power stations. The offshore sea surface can provide sufficient paving area for photovoltaic development, and offshore floating photovoltaic power generation has become a research hotspot in the photovoltaic industry. However, there are still challenges in exploring the design of offshore floating photovoltaic power generation systems. The literature "Analysis of the tilt and azimuth angles of photovoltaic systems in non-ideal positions for urban applications[J]. Barbón A, Bayón-Cueli C, Bayón L, et al. APPLIEDENERGY, 2022, 305." studies the energy loss of photovoltaic systems in non-ideal positions and the distribution of photovoltaic modules on the roofs of urban buildings. The paper "Optimisation for large-scale photovoltaic arrays placementbased on Light Detection And Ranging data[J]. Lukac N, Spelic D, StumbergerG, et al. APPLIED ENERGY, 2020, 263: 114592." proposes a new method to optimize the placement of large-scale photovoltaic arrays based on light detection and ranging point cloud data to maximize the potential of photovoltaic power generation. The paper "Effect of Wave Conditions on Offshore Floating Photovoltaic Power Generation[C] / / 2023 Tian Y, Gao Q, Li D, et al. 6TH INTERNATIONAL CONFERENCE ONRENEWABLE ENERGY AND POWER ENGINEERING, REPE 2023. New York: IEEE, 2023: 326-330." analyzes the calculation method of the amount of solar radiation received by photovoltaic modules under the action of regular waves, and only considers the situation under optimal lighting conditions.The paper "Effect of sea waves on radiant energy of floating photovoltaic[J]. Lu Wenhe, Lian Jijian, Dong Xiaofeng, et al. Journal of Hydroelectric Engineering, 2023, 42(5): 35-42." studies the efficiency ratio of the radiant energy received by offshore floating photovoltaics with different photovoltaic module inclination angles under regular waves at the same latitude and land photovoltaics with the optimal photovoltaic module inclination angle.

[0005] At present, the overall offshore floating photovoltaic power generation technology is in the test and pilot stage. The design optimization method of photovoltaic power generation system includes relying on expert experience and trial and error using simulation software. The design process is shown in Figure 1 . In the existing design process, designers first use commercial photovoltaic software to build a detailed model of the photovoltaic system, and then simulate the electrical behavior under different marine environmental conditions to predict system performance and identify potential problems. Subsequently, based on the simulation results and combined with the rich experience of experts, the design is repeatedly adjusted and optimized. This "trial and error method" is not only time-consuming and labor-intensive, but also difficult to take into account multiple conflicting goals, such as maximizing power generation efficiency, minimizing costs, and enhancing system stability and environmental adaptability. Although this method completes the design of the photovoltaic power generation system, its efficiency and accuracy are relatively low.

[0006] In the design process of photovoltaic power generation system, the motion characteristics of the photovoltaic floating platform will affect the layout of the photovoltaic array. Specifically, the rotation of the photovoltaic floating platform not only causes the solar irradiance received by the inclined surface of the photovoltaic module to change, but may also introduce additional shadow areas, thereby affecting the overall power generation efficiency. Therefore, when designing an offshore floating photovoltaic power generation system, it is also necessary to consider the impact of the rotation of the photovoltaic floating platform on the annual power generation of the photovoltaic module, so as to improve the accuracy of the calculation of the annual power generation of the offshore floating photovoltaic power generation system. Summary of the invention

[0007] In view of the above-mentioned problems existing in the prior art, the present invention provides a method for calculating the annual power generation of an offshore floating photovoltaic power generation system and an optimization design method, which comprehensively considers the influence of the rotation of the photovoltaic floating platform on the power generation performance of the photovoltaic modules, improves the calculation accuracy of the annual power generation, and optimizes the design of the offshore floating photovoltaic power generation system with maximizing the annual power generation and minimizing the total area of ​​the photovoltaic modules as the optimization goals, which can effectively increase the annual power generation and reduce the use of photovoltaic modules while maintaining the efficient operation of the offshore floating photovoltaic power generation system.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for calculating the annual power generation of an offshore floating photovoltaic power generation system, comprising:

[0009] Data acquisition steps: obtain the latitude, total horizontal radiation and normal incident radiation of the location of the photovoltaic power generation system;

[0010] Model construction steps: construct a calculation model for total radiation on the inclined surface based on radiation conversion factor, ground albedo, horizontal direct radiation, horizontal scattered radiation and horizontal total radiation;

[0011] Steps for determining the sun's position: determine the sun's position in the equatorial coordinate system by the calculated solar hour angle and solar declination angle, and determine the sun's position in the horizontal coordinate system by the calculated solar altitude angle and solar azimuth angle;

[0012] Calculation steps for horizontal radiation: convert the normal incident radiation into the direct radiation on the horizontal plane according to the sun's position information, and subtract the direct radiation on the horizontal plane from the total radiation on the horizontal plane to get the scattered radiation on the horizontal plane;

[0013] The steps for calculating the inclination and azimuth of the photovoltaic module are as follows: the rotation matrix R1 of the floating body coordinate system of the floating body platform relative to the earth coordinate system is obtained according to the Euler angle describing the dynamic characteristics of the floating body platform; the rotation matrix R2 of the floating body coordinate system of the photovoltaic module relative to the earth coordinate system is obtained according to the inclination and azimuth of the photovoltaic module relative to the floating body platform; the normal vector coordinates of the floating body platform after each rotation of the initial normal vector of the floating body platform are obtained according to the rotation matrix R1; the azimuth and zenith angle ranges of the normal vector coordinate transformation of the floating body platform are divided into counting grids; each grid center of the counting grid is used as the normal vector coordinate of the floating body platform; the plane normal vector coordinates of the photovoltaic module are obtained according to the rotation matrix R2 and the normal vector coordinates of the floating body platform; the inclination and azimuth of the photovoltaic module relative to the earth are calculated according to the plane normal vector coordinates of the photovoltaic module;

[0014] The radiation conversion factor calculation steps are as follows: the inclination and azimuth of the photovoltaic module relative to the earth are taken as the inclination and azimuth of the inclined surface, and the radiation conversion factor is obtained according to the sun's position, the inclination, the azimuth and the normal incident radiation;

[0015] The total radiation amount calculation steps of the inclined surface are as follows: the total radiation amount of the inclined surface before and after the floating platform rotates is calculated by using the total radiation amount calculation model of the inclined surface;

[0016] Calculation steps of irradiance attenuation factor: Calculate the irradiance attenuation factor caused by the rotation of the floating platform according to the change of total radiation on the inclined surface before and after the rotation of the floating platform and the statistical quantity of the counting grid;

[0017] Calculation steps for the shading effect: Calculate the shading effect of the front row of photovoltaic modules on the rear row of photovoltaic modules;

[0018] Calculation steps for annual power generation: Based on the total radiation of the inclined surface before the floating platform rotates, the irradiance attenuation factor, the size of the shielding effect, the efficiency of the photovoltaic modules and the overall efficiency of the offshore floating photovoltaic power generation system, the annual power generation of the offshore floating photovoltaic power generation system is expressed as:

[0019]

[0020] In the formula, Annual power generation of offshore floating photovoltaic power generation system, is the total area of ​​PV panels, is the total radiation of the inclined surface before the floating platform rotates, is the irradiance attenuation factor, is the shading effect of the front row of photovoltaic modules on the rear row of photovoltaic modules, is the photovoltaic module efficiency, The overall efficiency of the offshore floating photovoltaic power generation system.

[0021] In some embodiments, in the step of determining the sun position, the solar hour angle is calculated according to the true solar time by formula (1) in the equatorial coordinates, and the solar declination angle is calculated according to the number of days from the test date to January 1 by formula (2); formula (1) and formula (2) are expressed as:

[0022] (1)

[0023] (2)

[0024] In the formula, is the solar hour angle, is the solar declination angle, n is the number of days from the test date to January 1;

[0025] In the horizontal coordinate system, the solar altitude angle is calculated by formula (3) according to the solar hour angle, solar declination angle and the latitude of the photovoltaic power generation system, and the solar azimuth angle is calculated by formula (4) according to the solar hour angle, solar declination angle and solar altitude angle, or the solar azimuth angle is calculated by formula (4) according to the latitude of the photovoltaic power generation system, solar declination angle and solar altitude angle; formula (3) and formula (4) are expressed as:

[0026] (3)

[0027] (4)

[0028] In the formula, is the solar altitude angle, is the solar azimuth, is the latitude of the location of the photovoltaic power generation system.

[0029] In some embodiments, in the radiation conversion factor calculation step, the radiation conversion factor includes a direct radiation conversion factor, a scattered radiation conversion factor, and a horizontal surface reflected radiation conversion factor; the method for obtaining the direct radiation conversion factor is: according to the latitude of the location of the photovoltaic power generation system, the position of the sun, and the inclination angle of the photovoltaic module, the inclined surface solar incident angle is calculated by formula (5), and formula (5) is expressed as:

[0030] (5)

[0031] in:

[0032]

[0033] In the formula, is the solar incidence angle on the inclined surface, is the inclination angle of the inclined surface, is the relative azimuth between the solar azimuth and the tilt surface azimuth, is the azimuth of the inclined surface;

[0034] The horizontal solar incident angle is calculated according to the latitude of the photovoltaic power generation system and the position of the sun using formula (6), which is expressed as:

[0035] (6)

[0036] In the formula, The angle of solar incidence on the horizontal plane;

[0037] The direct radiation conversion factor obtained based on the solar incident angle of the inclined surface and the solar incident angle of the horizontal surface is expressed as:

[0038] (7)

[0039] In the formula, is the direct radiation conversion factor;

[0040] The method for obtaining the horizontal plane reflected radiation conversion factor is: According to the inclination angle of the photovoltaic module, the horizontal plane reflected radiation conversion factor is expressed as:

[0041] (8)

[0042] In the formula, is the horizontal surface reflected radiation conversion factor;

[0043] The method to obtain the scattered radiation conversion factor is: the corrected anisotropy index is expressed as follows based on the normal incident radiation:

[0044] (9)

[0045] In the formula, is the modified anisotropy index, is the normal incident radiation, is the solar constant;

[0046] According to the inclination angle of the photovoltaic module and the corrected anisotropy index, the scattered radiation conversion factor is expressed as:

[0047] (10)

[0048] In the formula, is the diffuse radiation conversion factor.

[0049] In some embodiments, in the model building step, the inclined surface total radiation calculation model is expressed as:

[0050] (11)

[0051] In the formula, is the total radiation of the inclined surface, is the direct radiation on the horizontal surface, is the horizontal scattered radiation, is the total solar radiation on the horizontal surface, is the ground albedo.

[0052] In some embodiments, in the irradiance attenuation factor calculation step, the specific method for calculating the irradiance attenuation factor caused by the rotation of the floating platform is:

[0053] According to the total radiation of the inclined surface before and after the floating platform rotates, the change of the total radiation of the inclined surface before and after the floating platform rotates is calculated by formula (12). Formula (12) is expressed as:

[0054] (12)

[0055] In the formula, is the change in annual radiation of the inclined surface before and after the floating platform rotates, is the total radiation of the inclined surface before the floating platform rotates, is the total radiation of the inclined surface after the floating platform rotates, is the index of the dip angle in the counting grid, is the index of the azimuth in the counting grid;

[0056] According to the change of total radiation on the inclined surface before and after the floating platform rotates and the statistical number of counting grids, the irradiance attenuation factor caused by the rotation of the floating platform is calculated by formula (13). Formula (13) is expressed as:

[0057] (13)

[0058] In the formula, The statistical quantity of the counting grid.

[0059] In some embodiments, in the step of calculating the magnitude of the shading effect, the specific method for calculating the magnitude of the shading effect of the front-row photovoltaic components on the rear-row photovoltaic components is:

[0060] The length of the shadow cast by the front row of photovoltaic modules is calculated according to the height of the photovoltaic modules, the solar altitude angle, the solar azimuth angle and the azimuth angle of the photovoltaic modules relative to the earth by formula (14). Formula (14) is expressed as:

[0061] (14)

[0062] In the formula, is the length of the shadow cast by the front row of photovoltaic modules, is the height of the photovoltaic module, is the azimuth angle of the PV module relative to the earth;

[0063] The length of the shadow cast by the front row of photovoltaic modules on the rear row of photovoltaic modules is calculated by formula (15) according to the length of the shadow cast by the front row of photovoltaic modules, the row spacing of photovoltaic modules, the solar altitude angle and the inclination angle of the photovoltaic modules relative to the earth. Formula (15) is expressed as:

[0064] (15)

[0065] In the formula, is the length of the shadow cast by the front row of PV modules on the rear row of PV modules, is the row spacing of photovoltaic modules, is the inclination angle of the PV module relative to the earth;

[0066] According to the shadow length of the front row of photovoltaic modules cast on the rear row of photovoltaic modules and the north-south length of the photovoltaic modules, the ratio of the unshaded area of ​​the photovoltaic modules to the area of ​​the photovoltaic modules is calculated by formula (16). Formula (16) is expressed as:

[0067] (16)

[0068] In the formula, The ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module. is the north-south length of the photovoltaic module;

[0069] According to the ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module and the hourly radiation received by the photovoltaic module, the annual shading effect at the angle corresponding to the grid center value is calculated by calculation formula (17). Formula (17) is expressed as:

[0070] (17)

[0071] In the formula, is the occlusion effect throughout the year at the angle corresponding to the grid center value, is the amount of radiation received by the PV panels hour by hour;

[0072] According to the shading effect of the whole year at the angle corresponding to the grid center value and the statistical number of counting grids, the shading effect of the front row photovoltaic modules on the rear row photovoltaic modules is calculated according to formula (18). Formula (18) is expressed as:

[0073] (18)

[0074] In the formula, The statistical quantity of the counting grid.

[0075] In some embodiments, in the photovoltaic module inclination and azimuth calculation step, the rotation matrix R1 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as:

[0076] (19)

[0077] In the formula, is the angle of rotation of the floating body coordinate system about the X axis with respect to the earth coordinate system, is the rotation angle of the floating body coordinate system about the Y axis with respect to the earth coordinate system, The angle of rotation of the floating body coordinate system around the Z axis with respect to the earth coordinate system;

[0078] The rotation matrix R2 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as:

[0079] (20)

[0080] In the formula, is the azimuth angle of the photovoltaic module relative to the floating platform, is the inclination angle of the PV module relative to the floating platform.

[0081] In order to achieve the above-mentioned object, a second embodiment of the present invention provides an optimization design method for an offshore floating photovoltaic power generation system.

[0082] Optimization target determination step: maximizing annual power generation and minimizing the total area of ​​PV panels are taken as optimization targets;

[0083] PV inverter selection steps: set the number of PV inverters, select PV inverters of the same model and with nominal power within the set nominal power range, and determine the upper limit of the number of PV inverters;

[0084] PV module selection steps: select PV modules with a set efficiency range within a set maximum power range, set the inclination range and azimuth range of the PV modules relative to the floating platform, determine the maximum number of PV modules in series and the maximum number of PV modules in parallel, and determine the number of PV modules according to the number of series and parallel connections of the PV inverter;

[0085] Steps for determining the spacing between photovoltaic arrays: set the column spacing of the photovoltaic arrays, determine the minimum spacing between photovoltaic arrays without blocking according to the solar altitude angle, solar azimuth angle and photovoltaic module height, and set the row spacing of the photovoltaic arrays to 0~minimum spacing+1m;

[0086] Steps for determining the area occupied by the photovoltaic array: determining the area occupied by the photovoltaic array according to the number of photovoltaic modules, the column spacing and row spacing of the photovoltaic array, the size of the photovoltaic modules and the inclination angle of the photovoltaic modules relative to the floating platform;

[0087] Optimization steps: Under the conditions of satisfying geometric constraints, wind load constraints and electrical constraints, adjust the photovoltaic inverter model, the number of photovoltaic inverters, the photovoltaic module model, the photovoltaic module configuration mode, the number of photovoltaic modules in series and parallel, the inclination and azimuth of the photovoltaic modules relative to the floating platform, and the photovoltaic array row spacing, and use the annual power generation calculation method of the offshore floating photovoltaic power generation system described in the first aspect of the present invention to calculate the annual power generation, and use a multi-objective optimization algorithm to minimize the maximum annual power generation and the minimum total area of ​​the photovoltaic modules; the geometric constraint is the matching degree between the size of the photovoltaic array and the floating platform, the wind load constraint is the wind load degree borne by the photovoltaic module, and the electrical constraint is the matching degree between the DC side and the AC side of the offshore floating photovoltaic power generation system.

[0088] In some embodiments, in the photovoltaic inverter selection step, the upper limit of the number of photovoltaic inverters is determined according to the nominal power of the photovoltaic inverter and the theoretical maximum capacity of the offshore floating photovoltaic power generation system:

[0089] (twenty one)

[0090] in:

[0091] (twenty two)

[0092] In the formula, is the theoretical maximum number of photovoltaic inverters, is the theoretical maximum capacity of an offshore floating photovoltaic power generation system, is the nominal power of the photovoltaic inverter, is the floating platform area, is the total radiation of the inclined surface, is the photovoltaic module efficiency, The overall efficiency of offshore floating photovoltaic power generation system;

[0093] In the photovoltaic module selection step, the maximum number of photovoltaic modules in series is determined according to the maximum input voltage of the photovoltaic inverter and the maximum open-circuit voltage of the photovoltaic module:

[0094] (twenty three)

[0095] In the formula, is the maximum number of PV panels connected in series, is the maximum input voltage of the photovoltaic inverter, is the maximum open circuit voltage of the photovoltaic module;

[0096] The maximum number of PV modules connected in parallel is determined based on the maximum input current of the PV inverter and the maximum short-circuit current of the PV modules:

[0097] (twenty four)

[0098] In the formula, is the maximum number of PV panels connected in parallel, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the number of PV inverters.

[0099] In some embodiments, in the optimization step, the geometric constraints include site utilization constraint, photovoltaic module quantity constraint and shadow shading constraint, and the site utilization constraint is:

[0100] (25)

[0101] in:

[0102] (26)

[0103] (27)

[0104] In the formula, is the site utilization rate, is the area occupied by the photovoltaic array, is the floating platform area, is the north-south length of the photovoltaic module, is the inclination angle of the photovoltaic module relative to the floating platform, is the line spacing, is the east-west length of the photovoltaic module, is the column spacing, is the actual number of PV panels;

[0105] The number of photovoltaic modules is constrained as follows:

[0106] (28)

[0107] in:

[0108] (29)

[0109] (30)

[0110] (31)

[0111] (32)

[0112] (33)

[0113] (34)

[0114] In the formula, is the maximum number of PV panels, is the maximum number of rows that the venue can accommodate, is the maximum number of columns that the venue can accommodate, is the actual number of PV panels connected in series, is the actual number of PV panels connected in parallel, is the north-south length of the ground projection of the photovoltaic module, is the east-west length of the photovoltaic module's ground projection, is the north-south length of the floating platform, is the east-west length of the floating platform;

[0115] The shadow occlusion constraints are:

[0116] (35)

[0117] In the formula, The shading of the front row to the back row within the range of the sun’s altitude and azimuth angles from 9 a.m. to 3 p.m. on the winter solstice, where 0 means all shading and 1 means no shading at all;

[0118] The wind load constraints are:

[0119] (36)

[0120] In the formula, is the front wind load on the photovoltaic module, is the wind load on the back of the photovoltaic module, is the maximum wind load on the front of the photovoltaic module, is the limit value of wind load on the back of PV modules;

[0121] Electrical constraints include system capacity ratio constraints, array peak power voltage constraints, array maximum open circuit voltage constraints, array maximum short-circuit current constraints, and photovoltaic inverter MPPT number utilization rate constraints, among which:

[0122] The system capacity ratio constraint is:

[0123] (37)

[0124] in:

[0125] (38)

[0126] In the formula, is the lower limit of the system capacity ratio, is the upper limit of the system capacity ratio, is the system capacity ratio, is the DC side power, is the AC side power, is the nominal power of the photovoltaic module, is the nominal power of the photovoltaic inverter, is the actual number of PV panels, is the actual number of PV inverters;

[0127] The array peak power voltage constraint is:

[0128] (39)

[0129] in:

[0130] (40)

[0131] In the formula, is the minimum working voltage of the photovoltaic inverter, is the maximum operating voltage of the photovoltaic inverter, is the photovoltaic array power voltage, is the peak power voltage of the photovoltaic module, is the actual number of PV panels connected in series;

[0132] The maximum open circuit voltage constraint of the array is:

[0133] (41)

[0134] in:

[0135] (42)

[0136] (43)

[0137] In the formula, is the maximum open circuit voltage of the photovoltaic array, is the maximum input voltage of the photovoltaic inverter, is the maximum open circuit voltage of the photovoltaic module, is the actual number of PV panels connected in series, The open circuit voltage of photovoltaic modules under standard test conditions. is the minimum working temperature, is the open circuit voltage temperature coefficient of the photovoltaic module;

[0138] The maximum short-circuit current constraint of the array is:

[0139] (44)

[0140] in:

[0141] (45)

[0142] (46)

[0143] In the formula, is the maximum short-circuit current of the photovoltaic array, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the actual number of PV panels connected in parallel, The short-circuit current of photovoltaic modules under standard test conditions. is the maximum temperature of the working condition, is the short-circuit current temperature coefficient of the photovoltaic module;

[0144] The utilization rate constraint of the MPPT path of the photovoltaic inverter is:

[0145] (47)

[0146] in:

[0147] (48)

[0148] In the formula, is the lower limit of the utilization rate of the MPPT paths of the photovoltaic inverter, The upper limit of the utilization rate of the MPPT paths of the photovoltaic inverter. is the utilization rate of the MPPT paths of the photovoltaic inverter, is the actual number of PV panels connected in parallel, is the maximum short-circuit current of the photovoltaic module, is the maximum input current of the photovoltaic inverter MPPT, is the number of MPPT paths of the photovoltaic inverter, is the actual number of PV inverters.

[0149] Compared with the prior art, the advantages and positive effects of the present invention are:

[0150] The annual power generation calculation method and optimization design method of the offshore floating photovoltaic power generation system provided by the present invention consider the influence of the motion characteristics of the floating platform on the layout of the photovoltaic modules, and accurately calculate the specific changes of the inclination angle and azimuth angle of the photovoltaic modules before and after the rotation through the Euler angle of the dynamic characteristics of the floating platform, so as to calculate the irradiance attenuation factor caused by the rotation of the floating platform, and calculate the annual power generation of the offshore floating photovoltaic power generation system according to the total radiation of the inclined surface, the irradiance attenuation factor and the shielding effect of the front row of the photovoltaic modules on the rear row, combined with the efficiency of the photovoltaic modules and the overall efficiency of the photovoltaic power generation system, thereby improving the accuracy of the annual power generation calculation. With the maximization of annual power generation and the minimization of the total area of ​​the photovoltaic modules as the optimization goals, the multi-objective optimization algorithm is applied to optimize the design of the offshore floating photovoltaic power generation system, which can effectively improve the annual power generation, and can also reduce the use of photovoltaic modules while maintaining the efficient operation of the offshore floating photovoltaic power generation system. While taking into account the economy and design quality, the adaptability of the offshore floating photovoltaic power generation system in complex sea conditions is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0151] Figure 1 Flowchart designed for a conventional offshore floating photovoltaic power generation system;

[0152] Figure 2 This is a flow chart of a method for calculating annual power generation of an offshore floating photovoltaic power generation system according to an embodiment of the present invention;

[0153] Figure 3 A schematic diagram of the rotation mode and coordinate system of the floating platform according to an embodiment of the present invention;

[0154] Figure 4 This is a schematic diagram of solar radiation angles according to an embodiment of the present invention;

[0155] Figure 5 This is a schematic diagram of shadow shielding of a photovoltaic module according to an embodiment of the present invention;

[0156] Figure 6 A flow chart of an optimization design method for an offshore floating photovoltaic power generation system according to an embodiment of the present invention;

[0157] Figure 7 This is a schematic plan view of the row spacing of photovoltaic modules according to an embodiment of the present invention;

[0158] Figure 8 A three-dimensional schematic diagram of the row spacing of photovoltaic modules according to an embodiment of the present invention;

[0159] Fig. 9 It is a flowchart of the NSGA-II multi-objective optimization algorithm described in an embodiment of the present invention;

[0160] Fig.10 A schematic diagram of the direction of the normal vector of the platform after multiple groups of angular rotations according to an embodiment of the present invention;

[0161] Fig.11 This is a graph showing the change trend of the average value of the population optimization target when the floating platform in Qingdao area does not rotate according to an embodiment of the present invention;

[0162] Fig.12 This is a trend chart of the average value of population optimization target when the floating platform in Qingdao area rolls -3° and pitches 3° using an embodiment of the present invention;

[0163] Fig.13 This is a graph showing the change trend of the average value of population optimization targets under the condition of multiple groups of angular rotations in Qingdao area according to an embodiment of the present invention;

[0164] Fig.14 This is a diagram showing the target value variation process when the floating platform in Qingdao area does not rotate according to an embodiment of the present invention;

[0165] Fig.15 This is a diagram showing the target value variation process when the floating platform in Qingdao area rolls -3° and pitches 3° according to an embodiment of the present invention;

[0166] Fig.16 This is a diagram showing the target value variation process under the condition of multiple groups of angle rotation in Qingdao area according to an embodiment of the present invention;

[0167] Fig.17 A schematic diagram of the Pareto frontier in the case where the floating platform in Qingdao area does not rotate according to an embodiment of the present invention;

[0168] Fig.18 This is a schematic diagram of the Pareto front when the floating platform in Qingdao area rolls -3° and pitches 3° according to an embodiment of the present invention;

[0169] Fig.19 A schematic diagram of the Pareto frontier under the condition of multiple groups of angle rotations in Qingdao area according to an embodiment of the present invention;

[0170] Fig. 20 This is a distribution diagram of annual power generation in Qingdao area when the floating platform does not rotate according to an embodiment of the present invention;

[0171] Fig.21 This is the annual power generation distribution diagram of the floating platform in Qingdao area under the condition of rolling -3° and pitching 3° in the embodiment of the present invention;

[0172] Fig. 22 This is a distribution diagram of annual power generation in Qingdao under multiple angular rotation conditions according to an embodiment of the present invention;

[0173] Fig.23 This is a graph of monthly power generation and the difference with the simulation software in the case where the floating platform in Qingdao area does not rotate according to the embodiment of the present invention;

[0174] Fig.24 This is a graph of monthly power generation and the difference with the simulation software when the floating platform in Qingdao area rolls -3° and pitches 3° in an embodiment of the present invention;

[0175] Fig.25 This is a diagram showing the monthly power generation under multiple angular rotation conditions in Qingdao area and the difference with the simulation software in an embodiment of the present invention.

[0176] In the figure, 1. floating platform, 2. shadow of photovoltaic modules, 3. front row photovoltaic modules, 4. rear row photovoltaic modules, A. direction of normal vector of horizontal plane, B. direction of normal vector of inclined plane, C. bow roll, D. heave, E. pitch, F. pitch, Q. roll, P. sway. DETAILED DESCRIPTION

[0177] The present invention is described in detail below by way of exemplary embodiments. However, it should be understood that elements, structures, and features in one embodiment may also be beneficially combined in other embodiments without further description.

[0178] See also Figure 2 The first embodiment of the present invention provides a method for calculating the annual power generation of an offshore floating photovoltaic power generation system, comprising:

[0179] S1. Data acquisition step: obtaining the latitude of the location of the photovoltaic power generation system, the horizontal plane direct radiation, the horizontal plane scattered radiation and the normal incident radiation.

[0180] S2. Model construction steps: Construct a calculation model for the total radiation of the inclined surface based on the radiation conversion factor, ground albedo, total radiation of the horizontal surface and total radiation of the horizontal surface.

[0181] Specifically, the radiation conversion factor includes direct radiation conversion factor, scattered radiation conversion factor and horizontal surface reflected radiation conversion factor. The total radiation calculation model of the inclined surface is expressed as:

[0182] (11)

[0183] In the formula, is the total radiation of the inclined surface, is the direct radiation conversion factor, is the direct radiation on the horizontal surface, is the diffuse radiation conversion factor, is the horizontal scattered radiation, is the horizontal surface reflected radiation conversion factor, is the total solar radiation on the horizontal surface, is the ground albedo.

[0184] S3. Step of determining the position of the sun: in the equatorial coordinate system, the position of the sun is determined by the calculated solar hour angle and solar declination angle, and in the horizontal coordinate system, the position of the sun is determined by the calculated solar altitude angle and solar azimuth angle.

[0185] It should be noted that in the equatorial coordinate system, the position of the sun is determined by the solar hour angle and the solar declination angle. The solar hour angle is the angular distance from the celestial meridian circle of the observation point along the lateness to the hour circle where the sun is located, and the solar declination angle is the angle between the earth's equatorial plane and the line connecting the sun and the center of the earth. Specifically, in the equatorial coordinate system, the solar hour angle is calculated according to the true solar time using formula (1), and the solar declination angle is calculated according to formula (2) based on the number of days from the test date to January 1; formula (1) and formula (2) are expressed as:

[0186] (1)

[0187] (2)

[0188] In the formula, is the solar hour angle, is the solar declination angle, and n is the number of days from the test date to January 1st.

[0189] It should be noted that, in the horizontal coordinate system, the position of the sun is determined by the solar altitude angle and the solar azimuth angle. The solar altitude angle is the angle between the direct sunlight and the plane where the observation point is located, and the solar azimuth angle is the angle between the projection line of the direct sunlight on the horizon and the south direction line on the horizon. Specifically, in the horizontal coordinate system, the solar altitude angle is calculated by formula (3) based on the solar hour angle, solar declination angle and latitude of the location of the photovoltaic power generation system, and the solar azimuth angle is calculated by formula (4) based on the solar hour angle, solar declination angle and solar altitude angle, or the solar azimuth angle is calculated by formula (4) based on the latitude of the location of the photovoltaic power generation system, solar declination angle and solar altitude angle; formula (3) and formula (4) are expressed as:

[0190] (3)

[0191] (4)

[0192] In the formula, is the solar altitude angle, is the solar azimuth, is the latitude of the location of the photovoltaic power generation system.

[0193] S4. Calculation steps for horizontal radiation: convert the normal incident radiation into horizontal direct radiation according to the sun position information, and subtract the horizontal direct radiation from the total horizontal radiation to obtain the horizontal scattered radiation.

[0194] It should be noted that the total horizontal radiation consists of the direct horizontal radiation and the scattered horizontal radiation. The total horizontal radiation is the sum of the direct horizontal radiation and the scattered horizontal radiation.

[0195] S5, the calculation steps of the inclination and azimuth of the photovoltaic module: according to the Euler angle describing the dynamic characteristics of the floating platform, the rotation matrix R1 of the floating body coordinate system of the floating platform relative to the earth coordinate system is obtained; according to the inclination and azimuth of the photovoltaic module relative to the floating platform, the rotation matrix R2 of the floating body coordinate system of the photovoltaic module relative to the earth coordinate system is obtained; according to the rotation matrix R1, the initial normal vector of the floating platform is obtained =(0,0,1) Normal vector coordinates of the floating platform after each rotation The azimuth and zenith angle ranges of the floating platform normal vector coordinate transformation are divided into counting grids, and each grid center of the counting grid is used as the floating platform normal vector coordinate. The plane normal vector coordinate of the photovoltaic module is obtained according to the rotation matrix R2 and the floating platform normal vector coordinate , the inclination and azimuth of the PV module relative to the earth are calculated according to the plane normal vector coordinates of the PV module.

[0196] Specifically, the rotation matrix R1 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as:

[0197] (19)

[0198] In the formula, is the angle of rotation of the floating body coordinate system about the X axis with respect to the earth coordinate system, is the rotation angle of the floating body coordinate system about the Y axis with respect to the earth coordinate system, It is the rotation angle of the floating body coordinate system about the Z axis with respect to the earth coordinate system.

[0199] It should be noted that the motion characteristics of the floating platform will affect the layout design of the photovoltaic array. Specifically, the rotation of the floating platform not only causes changes in the amount of solar radiation received by the inclined surface of the photovoltaic module, but may also introduce additional shadow areas, thereby affecting the overall power generation efficiency of the photovoltaic power generation system. Under the action of wind and waves, the floating platform undergoes multi-dimensional motions such as longitudinal sway, transverse sway, vertical sway, roll, pitch and bow. Among them, roll, pitch and bow directly affect the spatial posture of the photovoltaic module and array, and thus affect its performance. For the rotation method and the establishment of the rectangular coordinate system, see Figure 3 , the rectangular coordinate system is a right-hand system, and the direction of rotation follows the right-hand rule. In order to evaluate the impact of the rotation, it is necessary to accurately calculate the specific changes in the inclination and azimuth of the photovoltaic module before and after the rotation based on the Euler angle that describes the dynamic characteristics of the floating platform.

[0200] Roll only with roll angle When Angle, the transformation matrix is:

[0201]

[0202] Pitch only with a pitch angle of When the floating body coordinate system rotates around the Y axis relative to the earth coordinate system Angle, the transformation matrix is:

[0203]

[0204] Only the bow roll and the bow roll angle is When the floating body coordinate system rotates around the Z axis relative to the earth coordinate system Angle, the transformation matrix is:

[0205]

[0206] According to the external rotation rpy, when roll, pitch and yaw occur simultaneously, the combined rotation matrix is ​​the rotation matrix R1 of the floating platform's floating body coordinate system relative to the earth coordinate system.

[0207] The rotation matrix R2 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as:

[0208] (20)

[0209] In the formula, is the azimuth angle of the photovoltaic module relative to the floating platform, is the inclination angle of the PV module relative to the floating platform.

[0210] Specifically, the normal vector coordinates of the floating platform are transformed into azimuth angles by the following transformation formula: and zenith angle .

[0211]

[0212]

[0213] It should be noted that the azimuth is the angle between the projection of the normal vector of the floating platform on the horizontal plane and the x-axis, the zenith angle is the angle between the normal vector of the floating platform and the z-axis.

[0214] According to the plane normal vector coordinates of the photovoltaic module, the inclination angle of the photovoltaic module relative to the ground is calculated by the following formula: and azimuth .

[0215]

[0216] S6. Calculation steps of radiation conversion factor: Taking the inclination angle and azimuth of the photovoltaic module relative to the earth as the inclination angle of the tilt surface and the azimuth of the tilt surface, the radiation conversion factor is obtained according to the sun's position, the inclination angle of the tilt surface, the azimuth of the tilt surface and the normal incident radiation.

[0217] Specifically, in some embodiments, the method for obtaining the direct radiation conversion factor is: according to the latitude of the location of the photovoltaic power generation system, the position of the sun and the inclination angle of the photovoltaic module, the solar incident angle of the inclined surface is calculated by formula (5), and the formula (5) is expressed as:

[0218] (5)

[0219] in:

[0220]

[0221] In the formula, is the solar incidence angle on the inclined surface, is the inclination angle of the inclined surface, is the relative azimuth between the solar azimuth and the tilt surface azimuth, is the azimuth of the inclined surface;

[0222] The horizontal solar incident angle is calculated according to the latitude of the photovoltaic power generation system and the position of the sun using formula (6), which is expressed as:

[0223] (6)

[0224] In the formula, The angle of solar incidence on the horizontal plane;

[0225] The direct radiation conversion factor obtained based on the solar incident angle of the inclined surface and the solar incident angle of the horizontal surface is expressed as:

[0226] (7)

[0227] In the formula, is the direct radiation conversion factor.

[0228] It should be noted that the definitions of the angles in the above formula refer to Figure 4 , and the azimuth towards due south is defined as 0°, towards the west as positive, and towards the east as negative.

[0229] Specifically, in some embodiments, the method for obtaining the horizontal plane reflected radiation conversion factor is: according to the inclination angle of the photovoltaic module, the horizontal plane reflected radiation conversion factor is obtained and expressed as:

[0230] (8)

[0231] In the formula, is the horizontal surface reflected radiation conversion factor.

[0232] It should be noted that in order to calculate the horizontal plane reflected radiation on the inclined plane, it is usually assumed that the radiation received by the inclined plane from the horizontal plane and the surrounding environment is ideally isotropic. Therefore, the horizontal plane reflected radiation conversion factor can be simplified as shown in the above formula (8).

[0233] Specifically, in some embodiments, the method for obtaining the scattered radiation conversion factor is: according to the normal incident radiation, the corrected anisotropy index is obtained and expressed as:

[0234] (9)

[0235] In the formula, is the modified anisotropy index, is the normal incident radiation, is the solar constant;

[0236] According to the inclination angle of the photovoltaic module and the corrected anisotropy index, the scattered radiation conversion factor is expressed as:

[0237] (10)

[0238] In the formula, is the diffuse radiation conversion factor.

[0239] It should be noted that three types of calculation models are widely used in evaluating the amount of scattered radiation received on inclined surfaces, namely isotropic models, anisotropic models and refined models based on the solution of scattered radiation differentially and then integrated. The isotropic model assumes that the sky scattering model is uniform in all directions, that is, it does not consider the differences in the spatial distribution of terrain, slope aspect and sky scattered radiation; the anisotropic model considers the differences in the spatial distribution of sky scattered radiation and assumes that the intensity of scattered radiation in different directions is different. This type of model is relatively complex, but it can more accurately simulate the scattered radiation situation under the actual terrain; the model that constructs the solution of scattered radiation differentially and then integrated describes the physical process of scattered radiation through differential equations, and then combines the integral method to solve it. It shows high calculation accuracy and flexibility when dealing with complex scatterers and multiple scattering mechanisms. The Hay2 model used in this paper belongs to the anisotropic model. This model subdivides scattered radiation into zenith scattered radiation and circumsolar scattered radiation, and further optimizes the expression of the anisotropy index on the basis of the Hay1 model as shown in the above formula (10).

[0240] S7, inclined surface total radiation calculation step: calculate the inclined surface total radiation before and after the floating platform rotates by using the inclined surface total radiation calculation model.

[0241] S8. Calculation steps of irradiance attenuation factor: Calculate the irradiance attenuation factor caused by the rotation of the floating platform based on the change in total radiation on the inclined surface before and after the rotation of the floating platform and the statistical quantity of the counting grid.

[0242] Specifically, in some embodiments, the specific method for calculating the irradiance attenuation factor caused by the rotation of the floating platform is:

[0243] According to the total radiation of the inclined surface before and after the floating platform rotates, the change of the total radiation of the inclined surface before and after the floating platform rotates is calculated by formula (12). Formula (12) is expressed as:

[0244] (12)

[0245] In the formula, is the change in annual radiation of the inclined surface before and after the floating platform rotates, is the total radiation of the inclined surface before the floating platform rotates, is the total radiation of the inclined surface after the floating platform rotates, is the index of the dip angle in the counting grid, is the index of the azimuth in the counting grid;

[0246] According to the change of total radiation on the inclined surface before and after the floating platform rotates and the statistical number of counting grids, the irradiance attenuation factor caused by the rotation of the floating platform is calculated by formula (13). Formula (13) is expressed as:

[0247] (13)

[0248] In the formula, The statistical quantity of the counting grid.

[0249] S9, steps for calculating the magnitude of the shading effect: Calculate the magnitude of the shading effect of the front-row photovoltaic modules on the rear-row photovoltaic modules.

[0250] like Figure 5 As shown, given the inclination and azimuth of the photovoltaic modules relative to the ground, the height of the photovoltaic modules, and the row spacing, the shadow size is calculated first, and then the shadowing effect of the front photovoltaic modules on the rear photovoltaic modules is calculated. Specifically, the specific method for calculating the shadowing effect of the front photovoltaic modules on the rear photovoltaic modules is:

[0251] The length of the shadow cast by the front row of photovoltaic modules is calculated according to the height of the photovoltaic modules, the solar altitude angle, the solar azimuth angle and the azimuth angle of the photovoltaic modules relative to the earth by formula (14). Formula (14) is expressed as:

[0252] (14)

[0253] In the formula, is the length of the shadow cast by the front row of photovoltaic modules, is the height of the photovoltaic module, is the azimuth angle of the PV module relative to the earth;

[0254] The length of the shadow cast by the front row of photovoltaic modules on the rear row of photovoltaic modules is calculated by formula (15) according to the length of the shadow cast by the front row of photovoltaic modules, the row spacing of photovoltaic modules, the solar altitude angle and the inclination angle of the photovoltaic modules relative to the earth. Formula (15) is expressed as:

[0255] (15)

[0256] In the formula, is the length of the shadow cast by the front row of PV modules on the rear row of PV modules, is the row spacing of photovoltaic modules, is the inclination angle of the PV module relative to the earth;

[0257] According to the shadow length of the front row of photovoltaic modules cast on the rear row of photovoltaic modules and the north-south length of the photovoltaic modules, the ratio of the unshaded area of ​​the photovoltaic modules to the area of ​​the photovoltaic modules is calculated by formula (16). Formula (16) is expressed as:

[0258] (16)

[0259] In the formula, The ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module. is the north-south length of the photovoltaic module;

[0260] According to the ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module and the hourly radiation received by the photovoltaic module, the annual shading effect at the angle corresponding to the grid center value is calculated by calculation formula (17). Formula (17) is expressed as:

[0261] (17)

[0262] In the formula, is the occlusion effect throughout the year at the angle corresponding to the grid center value, is the amount of radiation received by the PV panels hour by hour;

[0263] According to the shading effect of the whole year at the angle corresponding to the grid center value and the statistical number of counting grids, the shading effect of the front row photovoltaic modules on the rear row photovoltaic modules is calculated according to formula (18). Formula (18) is expressed as:

[0264] (18)

[0265] In the formula, The statistical quantity of the counting grid.

[0266] S10. Calculation steps for annual power generation: Based on the total radiation of the inclined surface before the floating platform rotates, the irradiance attenuation factor, the size of the shielding effect, the efficiency of the photovoltaic modules and the overall efficiency of the offshore floating photovoltaic power generation system, the annual power generation of the offshore floating photovoltaic power generation system is expressed as:

[0267]

[0268] In the formula, Annual power generation of offshore floating photovoltaic power generation system, is the total area of ​​PV panels, is the total radiation of the inclined surface before the floating platform rotates, is the irradiance attenuation factor, is the shading effect of the front row of photovoltaic modules on the rear row of photovoltaic modules, is the photovoltaic module efficiency, The overall efficiency of the offshore floating photovoltaic power generation system.

[0269] See also Figure 6 The second aspect of the present invention provides an optimization design method for an offshore floating photovoltaic power generation system, comprising:

[0270] S1. Optimization target determination step: maximizing annual power generation and minimizing the total area of ​​PV panels are taken as optimization targets.

[0271] S2. PV inverter selection steps: set the number of PV inverters, select PV inverters of the same model and with a nominal power within the set nominal power range, and determine the upper limit of the number of PV inverters.

[0272] Specifically, the upper limit of the number of photovoltaic inverters is determined according to the nominal power of the photovoltaic inverter and the theoretical maximum capacity of the offshore floating photovoltaic power generation system:

[0273] (twenty one)

[0274] in:

[0275] (twenty two)

[0276] In the formula, is the theoretical maximum number of photovoltaic inverters, is the theoretical maximum capacity of an offshore floating photovoltaic power generation system, is the nominal power of the photovoltaic inverter, is the floating platform area, is the total radiation of the inclined surface, is the photovoltaic module efficiency, The overall efficiency of the offshore floating photovoltaic power generation system.

[0277] S3. PV module selection steps: select PV modules with a set efficiency range within a set maximum power range, set the inclination range and azimuth range of the PV modules relative to the floating platform, determine the maximum number of PV modules in series and the maximum number of PV modules in parallel, and determine the number of PV modules according to the number of series and parallel connections of the PV inverter.

[0278] It should be noted that the inclination angle and inclination setting of the photovoltaic module relative to the floating platform need to ensure that the photovoltaic module can be as perpendicular to the incident direction of sunlight as possible to reduce solar radiation loss. An inclination angle less than 0° and an inclination angle that is too large are not conducive to lighting, and an inclination angle that is too large will also cause a large wind load. Specifically, in some embodiments, the inclination range of the photovoltaic module relative to the floating platform is set to 0°~55°, and the azimuth range of the photovoltaic module relative to the floating platform is set to -45°~45°.

[0279] Specifically, the maximum number of PV modules connected in series is determined according to the maximum input voltage of the PV inverter and the maximum open-circuit voltage of the PV modules:

[0280] (twenty three)

[0281] In the formula, is the maximum number of PV panels connected in series, is the maximum input voltage of the photovoltaic inverter, It is the maximum open circuit voltage of the PV module.

[0282] Specifically, the maximum number of PV modules connected in parallel is determined according to the maximum input current of the PV inverter and the maximum short-circuit current of the PV module:

[0283] (twenty four)

[0284] In the formula, is the maximum number of PV panels connected in parallel, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the number of PV inverters.

[0285] S4. PV array spacing determination step: Set the column spacing of the PV array, determine the minimum spacing between PV arrays without obstruction based on the solar altitude angle, solar azimuth angle and PV module height, and set the row spacing of the PV array to the range of 0 to the minimum spacing + 1m based on the minimum spacing.

[0286] It should be noted that the configuration of the PV array row spacing is of great significance for reducing the shading of the front row PV modules to the rear row PV modules and thus improving the system efficiency. Figure 7 , 8 The non-blocking row spacing is an important reference for setting the row spacing. It refers to the minimum distance between the highest point of the front row of photovoltaic modules and the lowest point of the rear row of photovoltaic modules when the shadow is between 9 am and 3 pm on the winter solstice. According to formula (3), the solar azimuth is According to formula (4), the projection length of the photovoltaic module is , the minimum spacing between photovoltaic arrays without blocking is:

[0287]

[0288] In the formula, It is the minimum spacing between photovoltaic arrays without blocking each other.

[0289] S5. Steps for determining the area occupied by the photovoltaic array: determine the area occupied by the photovoltaic array according to the number of photovoltaic modules, the column spacing and row spacing of the photovoltaic array, the size of the photovoltaic modules and the inclination angle of the photovoltaic modules relative to the floating platform.

[0290] The calculation formula for the area occupied by the photovoltaic array is as follows:

[0291] (27)

[0292] In the formula, is the area occupied by the photovoltaic array, is the north-south length of the photovoltaic module, is the inclination angle of the photovoltaic module relative to the floating platform, is the line spacing, is the east-west length of the photovoltaic module, is the column spacing, is the actual number of PV panels.

[0293] S6, optimization step: Under the conditions of satisfying geometric constraints, wind load constraints and electrical constraints, adjust the photovoltaic inverter model, the number of photovoltaic inverters, the photovoltaic module model, the photovoltaic module configuration mode (indicating whether the photovoltaic module is placed horizontally or vertically), the number of photovoltaic modules in series and parallel, the inclination and azimuth of the photovoltaic modules relative to the floating platform, and the photovoltaic array row spacing, and calculate the annual power generation using the annual power generation calculation method for the offshore floating photovoltaic power generation system described in the embodiment of the first aspect of the present invention, and use a multi-objective optimization algorithm to minimize the maximum annual power generation and the minimum total area of ​​the photovoltaic modules; the geometric constraint is the matching degree between the size of the photovoltaic array and the floating platform, the wind load constraint is the wind load degree borne by the photovoltaic module, and the electrical constraint is the matching degree between the DC side and the AC side of the offshore floating photovoltaic power generation system.

[0294] Specifically, the geometric constraints include site utilization constraint, photovoltaic module quantity constraint and shadow shading constraint. The site utilization constraint is:

[0295] (25)

[0296] in:

[0297] (26)

[0298] In the formula, is the site utilization rate, is the floating platform area.

[0299] The number of photovoltaic modules is constrained as follows:

[0300] (28)

[0301] in:

[0302] (29)

[0303] (30)

[0304] (31)

[0305] (32)

[0306] (33)

[0307] (34)

[0308] In the formula, is the maximum number of PV panels, is the maximum number of rows that the venue can accommodate, is the maximum number of columns that the venue can accommodate, is the actual number of PV panels connected in series, is the actual number of PV panels connected in parallel, is the north-south length of the ground projection of the photovoltaic module, is the east-west length of the photovoltaic module's ground projection, is the north-south length of the floating platform, It is the east-west length of the floating platform.

[0309] The shadow occlusion constraints are:

[0310] (35)

[0311] In the formula, It represents the degree of obstruction of the front row to the back row within the range of the sun's altitude and azimuth angles from 9:00 a.m. to 3:00 p.m. on the winter solstice. 0 means complete obstruction and 1 means no obstruction at all.

[0312] The wind load constraints are:

[0313] (36)

[0314] In the formula, is the front wind load on the photovoltaic module, is the wind load on the back of the photovoltaic module, is the maximum wind load on the front of the photovoltaic module, It is the limit value of wind load on the back of PV modules.

[0315] Specifically, the wind load on the front of the photovoltaic module and the wind load on the back of the photovoltaic module are calculated by the wind load standard value calculation formula. The wind load standard value calculation formula is expressed as:

[0316]

[0317] In the formula, is the standard value of wind load, unit: kN / m 2 ; For height The wind vibration coefficient at is the overall shape coefficient of wind load, is the wind pressure height variation coefficient, is the basic wind pressure, unit: kN / m 2 It should be noted that, in order to ensure the stable operation of photovoltaic modules, the front wind load should generally not exceed 5400Pa, and the back wind load should generally not exceed 2400Pa.

[0318] Electrical constraints include system capacity ratio constraints, array peak power voltage constraints, array maximum open circuit voltage constraints, array maximum short-circuit current constraints and photovoltaic inverter MPPT path utilization rate constraints.

[0319] The system capacity ratio constraint is:

[0320] (37)

[0321] in:

[0322] (38)

[0323] In the formula, is the lower limit of the system capacity ratio, is the upper limit of the system capacity ratio, is the system capacity ratio, is the DC side power, is the AC side power, is the nominal power of the photovoltaic module, is the nominal power of the photovoltaic inverter, is the actual number of PV panels, is the actual number of PV inverters.

[0324] It should be noted that the system capacity ratio reflects the relationship between the power on the DC side and the power on the AC side. Appropriate over-capacity design is conducive to improving the comprehensive utilization rate of the photovoltaic system and reducing the cost of electricity of the photovoltaic system. Specifically, in the embodiment of the present invention, the value range of the system capacity ratio is set to 1~1.25.

[0325] The array peak power voltage constraint is:

[0326] (39)

[0327] in:

[0328] (40)

[0329] In the formula, is the minimum working voltage of the photovoltaic inverter, is the maximum operating voltage of the photovoltaic inverter, is the photovoltaic array power voltage, is the peak power voltage of the photovoltaic module, is the actual number of PV panels connected in series.

[0330] It should be noted that constraining the peak power voltage of the photovoltaic array within the operating voltage range of the photovoltaic inverter can ensure the safe operation of the photovoltaic power generation system.

[0331] The maximum open circuit voltage constraint of the array is:

[0332] (41)

[0333] in:

[0334] (42)

[0335] (43)

[0336] In the formula, is the maximum open circuit voltage of the photovoltaic array, is the maximum input voltage of the photovoltaic inverter, is the maximum open circuit voltage of the photovoltaic module, is the actual number of PV panels connected in series, The open circuit voltage of photovoltaic modules under standard test conditions. is the minimum working temperature, is the open circuit voltage temperature coefficient of the photovoltaic module.

[0337] The maximum short-circuit current constraint of the array is:

[0338] (44)

[0339] in:

[0340] (45)

[0341] (46)

[0342] In the formula, is the maximum short-circuit current of the photovoltaic array, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the actual number of PV panels connected in parallel, The short-circuit current of photovoltaic modules under standard test conditions. is the maximum temperature of the working condition, is the short-circuit current temperature coefficient of the photovoltaic module.

[0343] The utilization rate constraint of the MPPT path of the photovoltaic inverter is:

[0344] (47)

[0345] in:

[0346] (48)

[0347] In the formula, is the lower limit of the utilization rate of the MPPT paths of the photovoltaic inverter, The upper limit of the utilization rate of the MPPT paths of the photovoltaic inverter. is the utilization rate of the MPPT paths of the photovoltaic inverter, is the actual number of PV panels connected in parallel, is the maximum short-circuit current of the photovoltaic module, is the maximum input current of the photovoltaic inverter MPPT, is the number of MPPT paths of the photovoltaic inverter, is the actual number of PV inverters.

[0348] It should be noted that the higher the utilization rate of the MPPT paths of the photovoltaic inverter, the higher the utilization rate of the photovoltaic inverter. Specifically, the utilization rate of the MPPT paths of the photovoltaic inverter in the embodiment of the present invention is set to 0.8~1.

[0349] Specifically, the multi-objective optimization algorithm adopts the NSGA-Ⅱ multi-objective optimization algorithm, and its process is as follows: Fig. 9 shown.

[0350] The NSGA-Ⅱ multi-objective optimization algorithm population uses real number coding; the parent individual selection method is the binary tournament method; the crossover operator is simulated binary crossover, the crossover probability is 0.8, and the distribution index is 20; the mutation operator is a polynomial mutation operator, the mutation probability is 0.2, and the distribution index is 20. The population size is set to 1000, and the maximum number of iterations is set to 350.

[0351] The adaptive penalty function method is used to deal with constraints. Based on the population feasibility rate, individuals that violate the constraints are adaptively penalized. The algorithm uses the modified objective function value to check the dominance in the group. The basis for modification is the constraints violated by the individual and its target performance. The modified target value consists of two parts: distance metric and adaptive penalty , the corrected objective function value for:

[0352]

[0353] The calculation steps are as follows:

[0354] For individuals No. The objective function is regularized:

[0355]

[0356] Calculate individual The degree of constraint violation , whose value is equal to the individual The normalized sum of each constraint violated divided by the total number of constraints :

[0357]

[0358] in,

[0359]

[0360] In the formula, Indicates Individual The maximum violation of a constraint, is the tolerance of the equality constraint, is the number of inequality constraints, is the number of equality constraints. Greater than 0 means the individual violates the constraints, otherwise it means the constraints are met.

[0361] Calculate individual Distance metric in each objective function dimension:

[0362]

[0363] In the formula, is the current population feasibility rate.

[0364] The first part is based on the objective function, and the second part is based on constraint violations. The calculation method is:

[0365]

[0366] in,

[0367]

[0368] The penalty function effect is:

[0369] If the population feasibility rate is 0, no penalty will be imposed;

[0370] If the population feasible rate is small, the individuals that violate the constraints seriously will be punished.

[0371] If the feasible rate of the population is large, the infeasible individuals with large objective function values ​​will be mainly penalized.

[0372] The optimization objective of maximizing annual power generation is transformed into a minimization objective, and the algorithm optimization objective after being processed by the adaptive penalty function is as follows:

[0373]

[0374] in, and Respectively for and Corrected results.

[0375] It should be noted that using the NSGA-II multi-objective optimization algorithm to solve the multi-objective optimization problem of the photovoltaic power generation system will obtain the Pareto frontier. The solutions in this solution set do not dominate each other and cannot be directly compared. A decision-making method is required to select a better solution. The decision-making method selected in the embodiment of the present invention is the VIKOR method, which performs a compromise ranking of limited decision-making solutions by maximizing group utility and minimizing individual regret values, and the target weights are set to 0.5 and 0.5.

[0376] The effectiveness of the annual power generation calculation method and optimization design method of the offshore floating photovoltaic power generation system of the present invention is verified in combination with specific embodiments below.

[0377] Embodiment: The offshore floating photovoltaic power generation system is located in the Qingdao waters, with longitude and latitude of 36°N, 120°E, site shape of rectangle, site size of 50m×50m, and the rotation conditions of the floating platform include: no rotation, single angle rotation, and multi-angle rotation.

[0378] The tests were conducted under three scenarios: the floating platform did not rotate, the floating platform rolled -3° and then pitched 3°, and the floating platform rotated at multiple angles. These tests covered the conditions of still water, single-angle rotation, and complex-angle rotation. The purpose was to fully verify the optimization performance of the optimization algorithm under different sea conditions. The specific information of the multi-angle rotation is shown in Table 1. The direction distribution of the plane normal vector of the floating platform under this group of angles is shown in the following figure. Fig.10 shown.

[0379] Table 1

[0380]

[0381] The trend of the average value of population optimization target under three rotation conditions in Qingdao area is as follows Fig.11 , Fig.12 , Fig.13 As shown in the figure, the two optimization objectives Obj1 and Obj2 represent minimizing the opposite of annual power generation and minimizing the total area of ​​PV array components, respectively, and their values ​​are the normalized average values ​​of the population. The average values ​​of the two optimization objectives in the population dropped rapidly at the beginning of the optimization process, reflecting that the population converged rapidly in the global exploration stage. After 100 iterations, the average values ​​of the two optimization objectives were close to stability, which means that the population entered the local search stage. Minimizing the opposite of annual power generation is equivalent to maximizing annual power generation. Since maximizing annual power generation and minimizing the total area of ​​PV components are almost completely conflicting goals, the decrease in one of the target values ​​is always accompanied by an increase in the other target value.

[0382] Fig.14 , Fig.15 , Fig.16 This is the convergence process of the actual target values ​​under three scenarios in Qingdao. In the early stage of the evolution process, the target value distribution of the floating platform non-rotating scenario is relatively concentrated compared with the latter two. At the 100th generation, the population basically converged to the straight line reflecting the positive correlation between annual power generation and the total area of ​​PV panels. At this time, there are still many infeasible solutions in the population. At the 350th generation, the actual value of the population target basically fell on the straight line, completing the convergence process.

[0383] The Pareto frontier at the end of the optimization process in three scenarios in Qingdao is as follows Fig.17 , Fig.18 , Fig.19As shown in the figure, the red mark on the Pareto front is the location of the optimization algorithm optimization and decision-making results. The smaller points of Obj1 represent individuals with larger annual power generation in the population, and the smaller points of Obj2 represent individuals with smaller total area of ​​PV modules in the population. The frontier converges well and is close to the theoretical optimal frontier; the distribution range is large, reflecting that the population covers all possible scales and configurations well; the population is relatively densely distributed in areas with smaller annual power generation and smaller total area of ​​PV modules, and is sparsely distributed in another section of the frontier, which may be because there are fewer reasonable matching solutions for PV systems in areas with high annual power generation.

[0384] The optimization and decision results are shown in Table 2. Among them, the inverter selection, the number of inverters and the PV module selection have no direct relationship with the rotation of the floating platform. The inclination angle, azimuth angle and row spacing change with the rotation. The number of series and parallel connections changes with the changes of the first seven variables.

[0385] Table 2

[0386]

[0387] The result obtained by NSGA-II optimization is a suboptimal solution. Compared with other quantities to be optimized, the inclination and azimuth in the optimization results can better reflect the gap between the results and the theoretical optimal solution. The optimization results except the inclination and azimuth are set as constants, and the contour maps of annual power generation under three working conditions in Qingdao area with respect to the inclination and azimuth are drawn as shown in the figure. Fig. 20 , Fig.21 , Fig. 22 As shown in the figure, the red mark indicates the location of the optimization result. It can be seen that the inclination and azimuth in the optimization result are within the highest contour line, reflecting that the optimization result is extremely close to the theoretical optimal solution. Compared with the case where the floating platform does not rotate, the floating platform rolls -3° and pitches 3°, which makes the optimal inclination of the photovoltaic module larger and the optimal azimuth is biased to the west. As compensation, the floating platform rotates at multiple angles to slightly increase the optimal inclination.

[0388] The performance of the optimization results and the numerical simulation results under three working conditions in Qingdao are shown in Table 3. Because the multi-objective optimization algorithm must take into account the two goals of maximizing annual power generation and minimizing the total area of ​​PV panels, there is no comparability between the optimized annual power generation and the total area of ​​PV panels under different floating platform rotation conditions. The size of the annual unit power generation can better reflect the quality of the optimization results. The values ​​of "non-optimized annual unit power generation" and "non-optimized annual unit power generation" under "roll -3° pitch 3°" and "multi-group angle rotation" in the table are the results obtained by directly applying the optimization results of the floating platform without rotation to the latter two cases. Compared with the optimization results for specific working conditions, the annual unit power generation of the first case directly applied to the latter two cases is reduced by 0.8% and 4% respectively. The site utilization rate in the "roll -3° pitch 3°" case of the floating platform is smaller than the corresponding values ​​of the other two scenarios. The reason is related to the discontinuity of the selection and quantity of inverters and photovoltaic panels in the photovoltaic system and the matching relationship between them. In the table The meaning of is the change in irradiance caused by the rotation of the floating platform. 1 represents no change, greater than 1 represents an increase in irradiance, and vice versa represents a decrease. It can be seen from the values ​​in the table that rotation can cause the irradiance to increase or decrease. The meaning of is the radiation loss caused by shielding in the optimization result throughout the year under the current rotation of the floating platform. 1 represents no shielding loss throughout the year, and less than 1 represents the radiation with shielding loss.

[0389] Table 3

[0390]

[0391] In terms of power generation calculation, in order to verify the correctness of the program design, the configuration of the optimization results under three working conditions of the floating platform in Qingdao was simulated and calculated. The annual power generation in the simulation was 357MWh / yr, 348MWh / yr, and 383MWh / yr, respectively. The errors between the program calculation and the simulation results were 0.8%, 1.7%, and -2.1%, respectively. The monthly power generation calculation results and the monthly difference are shown in the figure below. Fig.23 , Fig.24 , Fig.25 shown.

[0392] The above embodiments are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for calculating the annual power generation of an offshore floating photovoltaic power generation system, characterized in that: include: Data acquisition steps: obtain the latitude, total horizontal radiation and normal incident radiation of the location of the photovoltaic power generation system; Model construction steps: construct a calculation model for total radiation on the inclined surface based on radiation conversion factor, ground albedo, horizontal direct radiation, horizontal scattered radiation and horizontal total radiation; Steps for determining the sun's position: determine the sun's position in the equatorial coordinate system by the calculated solar hour angle and solar declination angle, and determine the sun's position in the horizontal coordinate system by the calculated solar altitude angle and solar azimuth angle; Calculation steps for horizontal radiation: convert the normal incident radiation into the direct radiation on the horizontal plane according to the sun's position information, and subtract the direct radiation on the horizontal plane from the total radiation on the horizontal plane to get the scattered radiation on the horizontal plane; The steps for calculating the inclination and azimuth of the photovoltaic module are as follows: the rotation matrix R1 of the floating body coordinate system of the floating body platform relative to the earth coordinate system is obtained according to the Euler angle describing the dynamic characteristics of the floating body platform; the rotation matrix R2 of the floating body coordinate system of the photovoltaic module relative to the earth coordinate system is obtained according to the inclination and azimuth of the photovoltaic module relative to the floating body platform; the normal vector coordinates of the floating body platform after each rotation of the initial normal vector of the floating body platform are obtained according to the rotation matrix R1; the azimuth and zenith angle ranges of the normal vector coordinate transformation of the floating body platform are divided into counting grids; each grid center of the counting grid is used as the normal vector coordinate of the floating body platform; the plane normal vector coordinates of the photovoltaic module are obtained according to the rotation matrix R2 and the normal vector coordinates of the floating body platform; the inclination and azimuth of the photovoltaic module relative to the earth are calculated according to the plane normal vector coordinates of the photovoltaic module; The radiation conversion factor calculation steps are as follows: the inclination angle and azimuth angle of the photovoltaic module relative to the earth are the inclination angle and the azimuth angle of the inclination surface, and the radiation conversion factor is obtained according to the sun position, the inclination angle of the inclination surface, the azimuth angle of the inclination surface and the normal incident radiation. The radiation conversion factor includes a direct radiation conversion factor, a scattered radiation conversion factor and a horizontal surface reflected radiation conversion factor. The method for obtaining the direct radiation conversion factor is as follows: the solar incident angle of the inclination surface is calculated by formula (5) according to the latitude of the location of the photovoltaic power generation system, the sun position and the inclination angle of the photovoltaic module inclination surface. Formula (5) is expressed as: （5） in: In the formula, is the solar incidence angle on the inclined surface, is the inclination angle of the inclined surface, is the relative azimuth between the solar azimuth and the tilt surface azimuth, is the azimuth of the inclined surface; The horizontal solar incident angle is calculated according to the latitude of the photovoltaic power generation system and the position of the sun using formula (6), which is expressed as: （6） In the formula, The angle of solar incidence on the horizontal plane; The direct radiation conversion factor obtained based on the solar incident angle of the inclined surface and the solar incident angle of the horizontal surface is expressed as: （7） In the formula, is the direct radiation conversion factor; The method for obtaining the horizontal plane reflected radiation conversion factor is: According to the inclination angle of the photovoltaic module, the horizontal plane reflected radiation conversion factor is expressed as: （8） In the formula, is the horizontal surface reflected radiation conversion factor; The method to obtain the scattered radiation conversion factor is: the corrected anisotropy index is expressed as follows based on the normal incident radiation: （9） In the formula, is the modified anisotropy index, is the normal incident radiation, is the solar constant; According to the inclination angle of the photovoltaic module and the corrected anisotropy index, the scattered radiation conversion factor is expressed as: （10） In the formula, is the diffuse radiation conversion factor; The total radiation amount calculation steps of the inclined surface are as follows: the total radiation amount of the inclined surface before and after the floating platform rotates is calculated by using the total radiation amount calculation model of the inclined surface; Calculation steps of irradiance attenuation factor: Calculate the irradiance attenuation factor caused by the rotation of the floating platform according to the change of total radiation on the inclined surface before and after the rotation of the floating platform and the statistical quantity of the counting grid; Calculation steps for the shading effect: Calculate the shading effect of the front row of photovoltaic modules on the rear row of photovoltaic modules; Calculation steps for annual power generation: Based on the total radiation of the inclined surface before the floating platform rotates, the irradiance attenuation factor, the size of the shielding effect, the efficiency of the photovoltaic modules and the overall efficiency of the offshore floating photovoltaic power generation system, the annual power generation of the offshore floating photovoltaic power generation system is expressed as: In the formula, Annual power generation of offshore floating photovoltaic power generation system, is the total area of ​​PV panels, is the total radiation of the inclined surface before the floating platform rotates, is the irradiance attenuation factor, is the shading effect of the front row of photovoltaic modules on the rear row of photovoltaic modules, is the photovoltaic module efficiency, The overall efficiency of the offshore floating photovoltaic power generation system.

2. The method for calculating annual power generation of an offshore floating photovoltaic power generation system according to claim 1, characterized in that: In the solar position determination step, the solar hour angle is calculated according to the true solar time by formula (1) in the equatorial coordinates, and the solar declination angle is calculated according to the number of days from the test date to January 1 by formula (2); formula (1) and formula (2) are expressed as: （1） （2） In the formula, is the solar hour angle, is the solar declination angle, n is the number of days from the test date to January 1; In the horizontal coordinate system, the solar altitude angle is calculated by formula (3) according to the solar hour angle, solar declination angle and the latitude of the photovoltaic power generation system, and the solar azimuth angle is calculated by formula (4) according to the solar hour angle, solar declination angle and solar altitude angle, or the solar azimuth angle is calculated by formula (4) according to the latitude of the photovoltaic power generation system, solar declination angle and solar altitude angle; formula (3) and formula (4) are expressed as: （3） （4） In the formula, is the solar altitude angle, is the solar azimuth, is the latitude of the location of the photovoltaic power generation system.

3. The method for calculating the annual power generation of an offshore floating photovoltaic power generation system according to claim 2, characterized in that: In the model building step, the total radiation calculation model of the inclined surface is expressed as: （11） In the formula, is the total radiation of the inclined surface, is the direct radiation on the horizontal surface, is the horizontal scattered radiation, is the total solar radiation on the horizontal surface, is the ground albedo.

4. The method for calculating annual power generation of an offshore floating photovoltaic power generation system according to claim 2, characterized in that: In the irradiance attenuation factor calculation step, the specific method for calculating the irradiance attenuation factor caused by the rotation of the floating platform is: According to the total radiation of the inclined surface before and after the floating platform rotates, the change of the total radiation of the inclined surface before and after the floating platform rotates is calculated by formula (12). Formula (12) is expressed as: （12） In the formula, is the change in annual radiation of the inclined surface before and after the floating platform rotates, is the total radiation of the inclined surface before the floating platform rotates, is the total radiation of the inclined surface after the floating platform rotates, is the index of the dip angle in the counting grid, is the index of the azimuth in the counting grid; According to the change of total radiation on the inclined surface before and after the floating platform rotates and the statistical number of counting grids, the irradiance attenuation factor caused by the rotation of the floating platform is calculated by formula (13). Formula (13) is expressed as: （13） In the formula, The statistical quantity of the counting grid.

5. The method for calculating annual power generation of an offshore floating photovoltaic power generation system according to claim 2, characterized in that: In the step of calculating the magnitude of the shading effect, the specific method for calculating the magnitude of the shading effect of the front-row photovoltaic components on the rear-row photovoltaic components is: The length of the shadow cast by the front row of photovoltaic modules is calculated according to the height of the photovoltaic modules, the solar altitude angle, the solar azimuth angle and the azimuth angle of the photovoltaic modules relative to the earth by formula (14). Formula (14) is expressed as: （14） In the formula, is the length of the shadow cast by the front row of PV panels, is the height of the photovoltaic module, is the azimuth angle of the PV module relative to the earth; The length of the shadow cast by the front row of photovoltaic modules on the rear row of photovoltaic modules is calculated by formula (15) according to the length of the shadow cast by the front row of photovoltaic modules, the row spacing of photovoltaic modules, the solar altitude angle and the inclination angle of the photovoltaic modules relative to the earth. Formula (15) is expressed as: （15） In the formula, is the length of the shadow cast by the front row of PV modules on the rear row of PV modules, is the row spacing of photovoltaic modules, is the inclination angle of the PV module relative to the earth; According to the shadow length of the front row of photovoltaic modules projected on the rear row of photovoltaic modules and the north-south length of the photovoltaic modules, the ratio of the unshaded area of ​​the photovoltaic modules to the area of ​​the photovoltaic modules is calculated by formula (16). Formula (16) is expressed as: （16） In the formula, The ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module. is the north-south length of the photovoltaic module; According to the ratio of the unshaded area of ​​the photovoltaic module to the area of ​​the photovoltaic module and the hourly radiation received by the photovoltaic module, the annual shading effect at the angle corresponding to the grid center value is calculated by calculation formula (17). Formula (17) is expressed as: （17） In the formula, is the occlusion effect throughout the year at the angle corresponding to the grid center value, is the amount of radiation received by the PV panels hour by hour; According to the shading effect of the whole year at the angle corresponding to the grid center value and the statistical number of counting grids, the shading effect of the front row photovoltaic modules on the rear row photovoltaic modules is calculated according to formula (18). Formula (18) is expressed as: （18） In the formula, The statistical quantity of the counting grid.

6. The method for calculating annual power generation of an offshore floating photovoltaic power generation system according to claim 1, characterized in that: In the photovoltaic module inclination and azimuth calculation step, the rotation matrix R1 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as: （19） In the formula, is the angle of rotation of the floating body coordinate system about the X axis with respect to the earth coordinate system, is the rotation angle of the floating body coordinate system about the Y axis with respect to the earth coordinate system, The angle of rotation of the floating body coordinate system around the Z axis with respect to the earth coordinate system; The rotation matrix R2 of the floating platform floating body coordinate system relative to the earth coordinate system is expressed as: （20） In the formula, is the azimuth angle of the photovoltaic module relative to the floating platform, is the inclination angle of the PV module relative to the floating platform.

7. An optimization design method for an offshore floating photovoltaic power generation system, characterized in that: include: Optimization target determination step: maximizing annual power generation and minimizing the total area of ​​PV panels are taken as optimization targets; PV inverter selection steps: set the number of PV inverters, select PV inverters of the same model and with nominal power within the set nominal power range, and determine the upper limit of the number of PV inverters; PV module selection steps: select PV modules with a set efficiency range within a set maximum power range, set the inclination range and azimuth range of the PV modules relative to the floating platform, determine the maximum number of PV modules in series and the maximum number of PV modules in parallel, and determine the number of PV modules according to the number of PV modules in series and parallel; Steps for determining the spacing between photovoltaic arrays: set the column spacing of the photovoltaic arrays, determine the minimum spacing between photovoltaic arrays without blocking according to the solar altitude angle, solar azimuth angle and photovoltaic module height, and set the row spacing of the photovoltaic array to range from 0 to the minimum spacing + 1m; Steps for determining the area occupied by the photovoltaic array: determining the area occupied by the photovoltaic array according to the number of photovoltaic modules, the column spacing and row spacing of the photovoltaic array, the size of the photovoltaic modules and the inclination angle of the photovoltaic modules relative to the floating platform; Optimization steps: Under the conditions of satisfying geometric constraints, wind load constraints and electrical constraints, adjust the photovoltaic inverter model, the number of photovoltaic inverters, the photovoltaic module model, the photovoltaic module configuration mode, the number of photovoltaic modules in series and parallel, the inclination and azimuth of the photovoltaic modules relative to the floating platform, and the photovoltaic array row spacing, and calculate the annual power generation using the annual power generation calculation method for the offshore floating photovoltaic power generation system as described in any one of claims 1 to 6, and use a multi-objective optimization algorithm to minimize the maximum annual power generation and the minimum total area of ​​the photovoltaic modules; the geometric constraint is the matching degree between the size of the photovoltaic array and the floating platform, the wind load constraint is the wind load degree borne by the photovoltaic module, and the electrical constraint is the matching degree between the DC side and the AC side of the offshore floating photovoltaic power generation system.

8. The method for optimizing the design of an offshore floating photovoltaic power generation system according to claim 7, characterized in that: In the photovoltaic inverter selection step, the upper limit of the number of photovoltaic inverters is determined according to the photovoltaic inverter nominal power and the theoretical maximum capacity of the offshore floating photovoltaic power generation system: （21） in: （22） In the formula, is the theoretical maximum number of photovoltaic inverters, is the theoretical maximum capacity of an offshore floating photovoltaic power generation system, is the nominal power of the photovoltaic inverter, is the floating platform area, is the total radiation of the inclined surface, is the photovoltaic module efficiency, The overall efficiency of the offshore floating photovoltaic power generation system; In the photovoltaic module selection step, the maximum number of photovoltaic modules in series is determined according to the maximum input voltage of the photovoltaic inverter and the maximum open-circuit voltage of the photovoltaic module: （23） In the formula, is the maximum number of PV panels connected in series, is the maximum input voltage of the photovoltaic inverter, is the maximum open circuit voltage of the photovoltaic module; The maximum number of PV modules connected in parallel is determined based on the maximum input current of the PV inverter and the maximum short-circuit current of the PV modules: （24） In the formula, is the maximum number of PV panels connected in parallel, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the number of PV inverters.

9. The method for optimizing the design of an offshore floating photovoltaic power generation system according to claim 7, characterized in that: In the optimization step, the geometric constraints include site utilization constraint, photovoltaic module quantity constraint and shadow shading constraint. The site utilization constraint is: （25） in: （26） （27） In the formula, is the site utilization rate, is the area occupied by the photovoltaic array, is the floating platform area, is the north-south length of the photovoltaic module, is the inclination angle of the photovoltaic module relative to the floating platform, is the line spacing, is the east-west length of the photovoltaic module, is the column spacing, is the actual number of PV panels; The number of photovoltaic modules is constrained as follows: （28） in: （29） （30） （31） （32） （33） （34） In the formula, is the maximum number of PV panels, is the maximum number of rows that the venue can accommodate, is the maximum number of columns that the venue can accommodate, is the actual number of PV panels connected in series, is the actual number of PV panels connected in parallel, is the north-south length of the ground projection of the photovoltaic module, is the east-west length of the photovoltaic module's ground projection, is the north-south length of the floating platform, is the east-west length of the floating platform; The shadow occlusion constraints are: （35） In the formula, The shading of the front row to the back row within the range of the sun’s altitude and azimuth angles from 9 a.m. to 3 p.m. on the winter solstice, where 0 means all shading and 1 means no shading at all; The wind load constraints are: （36） In the formula, is the front wind load on the photovoltaic module, is the wind load on the back of the photovoltaic module, is the maximum wind load on the front of the photovoltaic module, is the limit value of wind load on the back of PV modules; Electrical constraints include system capacity ratio constraints, array peak power voltage constraints, array maximum open circuit voltage constraints, array maximum short-circuit current constraints, and photovoltaic inverter MPPT number utilization rate constraints, among which: The system capacity ratio constraint is: （37） in: （38） In the formula, is the lower limit of the system capacity ratio, is the upper limit of the system capacity ratio, is the system capacity ratio, is the DC side power, is the AC side power, is the nominal power of the photovoltaic module, is the nominal power of the photovoltaic inverter, is the actual number of PV panels, is the actual number of PV inverters; The array peak power voltage constraint is: （39） in: （40） In the formula, is the minimum working voltage of the photovoltaic inverter, is the maximum operating voltage of the photovoltaic inverter, is the photovoltaic array power voltage, is the peak power voltage of the photovoltaic module, is the actual number of PV panels connected in series; The maximum open circuit voltage constraint of the array is: （41） in: （42） （43） In the formula, is the maximum open circuit voltage of the photovoltaic array, is the maximum input voltage of the photovoltaic inverter, is the maximum open circuit voltage of the photovoltaic module, is the actual number of PV panels connected in series, The open circuit voltage of photovoltaic modules under standard test conditions. is the minimum working temperature, is the open circuit voltage temperature coefficient of the photovoltaic module; The maximum short-circuit current constraint of the array is: （44） in: （45） （46） In the formula, is the maximum short-circuit current of the photovoltaic array, is the maximum input current of the photovoltaic inverter, is the maximum short-circuit current of the photovoltaic module, is the actual number of PV panels connected in parallel, The short-circuit current of photovoltaic modules under standard test conditions. is the maximum temperature of the working condition, is the short-circuit current temperature coefficient of the photovoltaic module; The utilization rate constraint of the MPPT path of the photovoltaic inverter is: （47） in: （48） In the formula, is the lower limit of the utilization rate of the MPPT paths of the photovoltaic inverter, The upper limit of the utilization rate of the MPPT paths of the photovoltaic inverter. is the utilization rate of the MPPT paths of the photovoltaic inverter, is the actual number of PV panels connected in parallel, is the maximum short-circuit current of the photovoltaic module, is the maximum input current of the photovoltaic inverter MPPT, is the number of MPPT paths of the photovoltaic inverter, is the actual number of PV inverters.

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