A method for calculating energy collection efficiency of solar-powered UAV

Abstract

The present invention relates to the technical field of solar-powered unmanned aerial vehicles, and discloses a method for calculating the energy collection efficiency of solar-powered unmanned aerial vehicles. The main operating steps include: recording vertical ground irradiation, recording remote temperature of solar cells, establishing a solar irradiation model, establishing an irradiation model of a solar cell array, establishing a power output model of a solar cell power generation array, establishing an energy transmission loss model, and comparative analysis. The present invention utilizes the ground measured irradiation value and the remote temperature value of solar cells, combined with the actual array arrangement of solar cells on the unmanned aerial vehicle and related theoretical calculations, to solve the current situation that the energy collection efficiency of the onboard solar cell array is difficult to accurately evaluate. The method is also easy to implement in engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of solar-powered unmanned aerial vehicles, and in particular to a method for calculating the energy collection efficiency of a solar-powered unmanned aerial vehicle. Background Art

[0002] Solar drones use solar energy as energy, and theoretically can fly forever, without pollution to the environment, are flexible to use, and have low costs, and have broad application prospects. In civil applications, they can be used for atmospheric research, weather forecasting, environmental and disaster monitoring, crop telemetry, traffic control, telecommunications and television services, and nature reserve monitoring; in military applications, they can be used for border patrols, reconnaissance, and communication relays.

[0003] Considering the application characteristics of solar drones, solar cell modules should not only have high conversion efficiency, but also be lightweight, flexible, and adaptable to the application of wing airfoil surfaces. At present, solar drones are mainly divided into skin-integrated and hard-shell drones according to the different application methods of solar cell modules. The two types of drones have their own advantages and disadvantages. After the solar cell modules are laid on the aircraft, they need to form multiple solar cell arrays through series and parallel connection between the modules. The power generation power and voltage range of the solar cell array need to match the corresponding MPPT (maximum power point tracking) controller. The design of the solar cell array is crucial, which is related to whether the solar cell can achieve maximum power output and the energy collection efficiency of the whole machine. The conversion efficiency of solar cell modules will be measured under standard conditions before being laid on the aircraft. After the solar cell modules form a solar cell array on the aircraft, they are affected by the wing surface, test conditions, etc., and their conversion efficiency under standard conditions cannot be tested. They can only roughly evaluate their energy collection. This method cannot support the estimation of energy collection during the flight test. Summary of the invention

[0004] The present invention provides a method for calculating the energy collection efficiency of a solar-powered unmanned aerial vehicle. The method can more accurately evaluate the ground energy collection efficiency of a solar-powered unmanned aerial vehicle and verify the energy collection efficiency in a flight test.

[0005] The steps of the present invention include: establishing a solar irradiation model, establishing a solar cell array irradiation model, establishing a solar cell array power output model, calculating the theoretical output power of the MPPT controller corresponding to each power generation array, comparing the actual output power value of the MPPT controller obtained by telemetry with the theoretical value, and obtaining the energy collection efficiency of the solar drone.

[0006] Furthermore, establishing a solar radiation model includes:

[0007] Vertical irradiation record on the ground: Use a level meter to find a horizontal plane with no obstructions around it. The irradiance meter test probe is perpendicular to the ground horizontal plane. Monitor and record the vertical irradiation intensity I g ;

[0008] Temperature sensors are added during the installation of solar cell modules, and ground telemetry records the operating temperature T of the solar cell. cell ;

[0009] Reference irradiation model, with local latitude Lati, local longitude Longi, altitude h, number of days N d , time t as input, output solar altitude angle H a and azimuth angle ψ, calculate the direction of the sun's position vector in the inertial coordinate system

[0010] By recording the vertical irradiance I g and the solar altitude angle H a , calculate the magnitude of the sun position vector I s :

[0011] I s =I g / sin(H a ).

[0012] Furthermore, the radiation intensity recording interval is 1 to 3 seconds.

[0013] Furthermore, establishing a solar cell array irradiation model includes:

[0014] The cells selected for the wing airfoil are segmented and folded into lines, and the inclination angle of each cell is The wing dihedral angle is θ sf , then in the body coordinate system, the solar cells with the same inclination angle are connected in series to form a power generation array, and the unit normal vector of the power generation array is It can be expressed as:

[0015]

[0016] Through coordinate system transformation, the unit normal vector of the power generation array in the body coordinate system is converted into the unit normal vector in the inertial coordinate system.

[0017]

[0018] J eb is the transformation matrix:

[0019]

[0020] In the formula, θ P is the pitch angle of the aircraft, θ Y is the yaw angle of the aircraft, θ R is the roll angle of the aircraft. Further, calculate the vertical incidence of sunlight on the solar cell on the drone

[0021]

[0022] Furthermore, the solar cell array power output model is established including:

[0023] According to the working temperature of the solar cell, the conversion efficiency η and temperature coefficient c under reference standard conditions cell , normal temperature T0, calculate the solar cell conversion efficiency η at this temperature cell :

[0024] η cell =η*(1-c cell *(T cell -T0))

[0025] The vertical incident sunlight on the solar cell The number of cells in a solar array Conversion efficiency η at operating temperature cell , Select the effective power generation area of ​​solar cell monomer A s As input, the theoretical output power P of each solar array is calculated i solar :

[0026]

[0027] Furthermore, the theoretical output power of the MPPT controller corresponding to each power generation array is calculated:

[0028] P i MPPT =P i solar *η line *η shade *η MPPT

[0029] Among them, η line is the cable loss coefficient, η shade is the shading loss coefficient, η MPPT is the efficiency coefficient of the MPPT controller.

[0030] Beneficial effects of the present invention:

[0031] Through the above technical solution, the theoretical energy collection of solar drones can be calculated. By comparing with the power value obtained by onboard telemetry, the energy collection efficiency of onboard solar cells can be evaluated. The present invention uses the ground measured irradiation value and the solar cell telemetry temperature value, combined with the actual array mode of solar cells on drones and related theoretical calculations, to solve the current situation that the energy collection efficiency of onboard solar cell arrays is difficult to accurately evaluate. This method is also easy to implement in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A calculation flow chart of a method for calculating energy collection efficiency of a solar-powered UAV provided in an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the division of the inclination angles of solar cells in a method for calculating the energy collection efficiency of a solar drone provided in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of a power array in a method for calculating energy collection efficiency of a solar drone provided in an embodiment of the present invention.

[0035] Figure 2 The reference number 1 is the wing airfoil, and the reference number 2 is the solar cell. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0037] The technical solution of the present invention is a method for calculating the energy collection efficiency of a solar-powered UAV, which mainly includes: recording ground vertical irradiation, recording solar cell telemetry temperature, establishing a solar irradiation model, establishing a solar cell array irradiation model, establishing a solar cell power generation array power output model, establishing an energy transmission loss model, and comparative analysis.

[0038] First, use a level meter to find a horizontal plane with no obstructions around it. The radiometer test probe is perpendicular to the horizontal plane of the earth, monitoring and recording the vertical radiation intensity I g The radiation intensity is recorded at intervals of 1 to 3 seconds.

[0039] Furthermore, temperature sensors are added during the installation of solar cell modules, and ground telemetry records the operating temperature of the solar cell T cell .

[0040] Further, referring to the irradiation model, the local latitude Lati, the local longitude Longi, the altitude h, the number of days N d , time t as input, output solar altitude angle H a And azimuth angle ψ, further calculate the direction of the sun position vector in the inertial coordinate system

[0041] Furthermore, by recording the vertical irradiance I g and the solar altitude angle H a , the magnitude of the sun position vector I can be calculated s :

[0042] I s =I g / sin(Ha )

[0043] So far, the solar radiation model in the inertial coordinate system has been established.

[0044] The solar cells in each power generation array are processed as a plane with a certain inclination angle to the X-axis of the body coordinate system, that is, the wing airfoil is segmented and folded using the selected cells. The inclination angle of each cell is The wing dihedral angle is θ sf In the body coordinate system, solar cells with the same inclination angle are connected in series to form a power generation array, and the unit normal vector of the power generation array is It can be expressed as:

[0045]

[0046] Through coordinate system transformation, the unit normal vector of the power generation array in the body coordinate system is converted into the unit normal vector in the inertial coordinate system.

[0047]

[0048] J eb is the transformation matrix:

[0049]

[0050] In the formula, θ P is the pitch angle of the aircraft, θ Y is the yaw angle of the aircraft, θ R is the roll angle of the aircraft. Further, calculate the vertical incidence of sunlight on the solar cell on the drone

[0051]

[0052] At this point, the solar cell array irradiation model has been established.

[0053] Furthermore, according to the operating temperature of the solar cell, the conversion efficiency η and the temperature coefficient c under the reference standard condition are cell , normal temperature T0, calculate the solar cell conversion efficiency η at this temperature cell :

[0054] η cell =η*(1-c cell *(T cell -T0))

[0055] The vertical incident sunlight on the solar cell The number of cells in a solar array Conversion efficiency η at operating temperature cell, Select the effective power generation area of ​​solar cell monomer A s As input, the theoretical output power P of each solar array is calculated i solar :

[0056]

[0057] Furthermore, considering the cable loss coefficient η line , shading loss coefficient η shade , MPPT controller efficiency coefficient η MPPT , calculate the output power of the MPPT controller corresponding to each power generation array:

[0058] P i MPPT =P i solar *η line *η shade *η MPPT

[0059] The total power generated by the entire solar drone is the sum of the output powers of each MPPT controller. Furthermore, the MPPT output power obtained by onboard telemetry is compared with the theoretical output in the above scheme to evaluate the collection efficiency of the onboard solar cells.

[0060] Through the above technical solution, the theoretical energy collection of solar drones can be calculated. By comparing with the power value obtained by onboard telemetry, the energy collection efficiency of onboard solar cells can be evaluated. The present invention uses the ground measured irradiation value and the solar cell telemetry temperature value, combined with the actual array mode of solar cells on drones and related theoretical calculations, to solve the current situation that the energy collection efficiency of onboard solar cell arrays is difficult to accurately evaluate. This method is also easy to implement in engineering.

[0061] The laying method is further explained below in conjunction with the implementation diagram. Figure 3 The left wing of the 9 solar arrays has a chord length of 1120mm and a wing dihedral angle of 3°. Figure 2 The upper curve of the wing is divided into 9 broken lines by 125mm*125mm crystalline silicon solar cells. The 9 broken lines form 9 inclination angles with the X-axis. The 9 broken lines correspond to 9 solar cell arrays along the wingspan direction. Each array contains 55 cells, and the area of ​​each cell is 0.0156m 2 The conversion efficiency of the selected crystalline silicon cell under standard conditions is 22%, and the temperature coefficient is -0.25%. The cable loss coefficient is 0.97, the shading loss coefficient is 0.97, and the MPPT controller efficiency coefficient is 0.98. Figure 1 Examples are described.

[0062] Step 1: Use a level gauge to find the horizontal plane, and the irradiance meter test probe is perpendicular to the horizontal plane of the earth. Monitor and record the vertical irradiance intensity. The irradiance intensity recording interval is 2 seconds. Add temperature sensors during the laying of solar cell modules, and the ground telemetry records the solar cell operating temperature T cell ;

[0063] Step 2: Refer to the irradiation model, take the local latitude, local longitude, altitude, day, and time as input, output the solar altitude angle and azimuth, and calculate the direction of the solar position vector in the inertial coordinate system by combining the direction vector calculation formula. By recording the vertical irradiation intensity and solar altitude angle, calculate the size of the solar position vector. So far, the inertial coordinate system solar irradiation model has been established;

[0064] Step 3: Treat the solar cells in each power generation array as a plane with a certain inclination angle to the X-axis of the body coordinate system, that is, the wing airfoil is segmented and folded using the selected cells. The inclination angle of each cell is θ qzi , the wing dihedral angle is θ sf In the body coordinate system, the unit normal vectors of the 9 solar cell arrays are established by combining the wing dihedral angle and the 9 cell inclination values. Further, through the coordinate system transformation, the unit normal vector of the array in the body coordinate system is converted into the unit normal vector in the inertial coordinate system, and then the cosine is calculated with the sun vector to obtain the vertical irradiation intensity of the 9 solar cell arrays at any flight time.

[0065] Step 4: Combine the solar cell temperature and cell temperature coefficient recorded by telemetry to calculate the solar cell conversion efficiency at that temperature. The product of the vertical irradiation intensity of the cell array, the number of cells in the cell array, the cell power generation area and the conversion efficiency is the theoretical output power of each cell array;

[0066] Step 5: The theoretical output power of each battery array is multiplied by the cable loss coefficient, the shading loss coefficient, and the MPPT controller efficiency coefficient, which is the theoretical output power of the MPPT controller corresponding to each power generation array;

[0067] Step 6: During the flight test or ground test, the actual output power value of the MPPT controller can be obtained by telemetry. By comparing the theoretical and actual values, the energy collection efficiency of the solar drone can be analyzed.

[0068] The above specific implementations are limited to explaining and illustrating the technical solutions of the present invention, but cannot constitute a limitation on the protection scope of the claims. Those skilled in the art should be aware that any new technical solutions obtained by making any simple deformation or replacement on the basis of the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for calculating the energy collection efficiency of a solar-powered drone, characterized in that the steps include: Establish a solar irradiation model, a solar cell array irradiation model, and a solar cell array power output model, calculate the theoretical output power of the MPPT controller corresponding to each power generation array, compare the actual output power value of the MPPT controller obtained by telemetry with the theoretical value, and obtain the energy collection efficiency of the solar drone; Building a solar irradiation model includes: Vertical irradiation record on the ground: Use a level meter to find a horizontal plane with no obstructions around it. The irradiance meter test probe is perpendicular to the ground horizontal plane. Monitor and record the vertical irradiation intensity I g ; Temperature sensors are added during the installation of solar cell modules, and ground telemetry records the operating temperature T of the solar cell. cell ; Reference irradiation model, with local latitude Lati, local longitude Longi, altitude h, number of days N d , time t as input, output solar altitude angle H a and azimuth angle ψ, calculate the direction of the sun's position vector in the inertial coordinate system By recording the vertical irradiance I g and the solar altitude angle H a , calculate the magnitude of the sun position vector I s : I s =I g / sin(H a ); Modeling solar array irradiation involves: The cells selected for the wing airfoil are segmented and folded into lines, and the inclination angle of each cell is The wing dihedral angle is θ sf , then in the body coordinate system, the solar cells with the same inclination angle are connected in series to form a power generation array, and the unit normal vector of the power generation array is It can be expressed as: Through coordinate system transformation, the unit normal vector of the power generation array in the body coordinate system is converted into the unit normal vector in the inertial coordinate system. J eb is the transformation matrix: In the formula, θ P is the pitch angle of the aircraft, θ Y is the yaw angle of the aircraft, θ R is the roll angle of the aircraft. Further, calculate the vertical incidence of sunlight on the solar cell on the drone Modeling the power output of a solar array involves: According to the working temperature of the solar cell, the conversion efficiency η and temperature coefficient c under reference standard conditions cell , normal temperature T0, calculate the solar cell conversion efficiency η at this temperature cell : η cell =η*(1-c cell *(T cell -T0)) The vertical incident sunlight on the solar cell The number of cells in a solar array Conversion efficiency η at operating temperature cell , Select the effective power generation area of ​​solar cell monomer A s As input, the theoretical output power P of each solar array is calculated i solar : Calculate the theoretical output power of the MPPT controller corresponding to each power generation array: P i MPPT =P i solar *or line *or shade *or MPPT Among them, η line is the cable loss coefficient, η shade is the shading loss coefficient, η MPPT is the efficiency coefficient of the MPPT controller.

2. A method for calculating the energy collection efficiency of a solar-powered UAV according to claim 1, characterized in that: The radiation intensity recording interval is 1 to 3 seconds.

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