Research On Spacecraft Solar Array Shading Effects And Power Subsystem Simulation And Optimization Method

Spacecraft power subsystem is a core and essential subsystem of the spacecraft.Its functions are generating electric energy,regulating electric energy,storing electric energy,and distributing electric energy.Due to the limitations in volume,weight,and economic feasibility,the spacecraft power subsystem cannot implement dual-system backup like other subsystems.With the support of the Chinese Lunar Exploration Program,the National Natural Science Foundation of China,and other projects and foundations,this thesis conducts in-depth research and improvement of five issues,including solar array analysis and calculation under translucent shadow,layout optimization of the solar array under partially shaded conditions,multi-objective optimization of the power subsystem,Li-ion battery state-of-charge(SOC)estimation and lunar rover power subsystem simulation and verification.These five aspects are explored and developed to reasonably design and reduce the effect of shading on the solar array,accurately calculate the output power of solar array at different orbital positions and attitudes and quickly and accurately estimate the state-of-charge of the battery,in order to provide support for spacecraft power subsystem design,energy-balance analysis and on-orbit management.The large-scale components outside the cabin cause compound shading consist of solid shading and translucent shading,both of which cause the output power of the solar array decline.In order to solve this problem,a method for calculating the translucent shadow is proposed.The proposed method builds 3D-model of the metal mesh with the minimum repeating unit to obtain the light transmission rate of the metal mesh under different illumination.Through establishing the correspondence between the light transmittance and incident light direction,the shadow caused by the metal mesh components is calculated,and the output characteristics of the solar cell,string,and array under the condition of translucent shadow is analyzed which supports accurate calculation of the solar array output power by theory and data.By discussing the differences between solutions for solving partially shaded problems in aerospace and ground applications,a method for optimizating the solar array layout to improve the output power performance under partially shaded conditions is proposed.Quantitative indices were proposed to evaluate the output power performance of different layouts in specific mission.An improved genetic algorithm is proposed with the encoding,crossover,and mutate methods of the layouts to solve the problem which is difficult to seek the analytical solution between the evaluation index and the layouts.Without adding additional components or changing the control algorithms,the proposed algorithm improves the solar array output power performance under partially shaded conditions.The process of spacecraft power subsystems design is mostly a compound of simulation and manual adjustment,which leads to a narrow range of exploration,while multi-variable coupling problems are hard to solve and dynamic programming optimal design is difficult to achieve.A multi-objective multi-variable optimization framework is proposed to improve the designing process spacecraft power subsystem.A modularly integrated simulation model is established.After inputting task parameters and constraints,various solutions are automatically evaluated and compared,and a heuristic optimization algorithm is used to explore the solution domain to give an optimized solutions that met the constraints.A hardware-in-loop simulation platform is built to verify the key constraints of the optimized solution to ensure that it meets the requirements.The integrated simulation and verification method enables rapid qualitative and quantitative analysis of the spacecraft power subsystem,which helps to shorten the design period and improve reliability.Operation commands for the lunar rover are simulated and verified by the ground simulation and verification system and transmitted to the lunar rover through teleoperation instructions when it is on-orbit.Power subsystem simulation and verification are studied,which contain Lunar dust accumulation simulation,Moonlight wake-up simulation,secondary power supply controller,cable network modelling and load simulation model.A simulation and verification software consist of ten simulation modules are developed.The model of the software platform is initialized with data such as the SOC of the battery at the initial time,and then quickly simulate the important status data through the next stage of the work process including output power of the solar array,battery working status,SOC,voltage of the power subsystem which support mission planning and analysis decisions.The simulation results of continuous working condition and severe operating condition are consistent with the actual work situation,and verify the validity of the various functional modules of the software.