Complete electrical model and simulation of a medium size satellite

Abstract

Aiming on the requirement of generating an accurate electrical model of a medium size satellite, the software created for this paper provides a complete simulation of a medium to bigger size satellites. The components include system design and solidification of a generic solar array, distribution system, backup battery system, load analysis system and a complete thermal model for the battery and solar array. The software includes solar cell to solar array relations, bypass systems, imbalance in array wings, array power generation and shunting model, battery charge and discharge model and a load profile. Load profile is a data stream fed into the computer including illumination or eclipse data. All cell/array/battery features are highly realistic and database or graph modeled. Initial process begins with identification of peak and average power requirements. Given the bus voltage, single cell open circuit voltage and short circuit current, the software calculates number of cells per block, number of blocks per string, number of parallel strings per circuit and number of circuits for the satellite. According to the load profile which includes the day/night flag the battery is either charged or discharged. During daylight, power is used to run the system requirements and charge the battery. Excess power is calculated and shunted. On the other hand, during darkness, the panels provide no power. The only power source is the battery. Therefore the simulation needs to have an accurate battery model for both charge and discharge features. Battery function includes slow and fast charge rates, and is a complex function of various inputs. Since the whole simulation is heavily dependent on temperature, the system also includes a built in model for thermal cooling. The motive in this study was to precisely model and simulate the complete electrical function of a satellite. An accurate model and simulation of the actual system greatly helps the design process. The goal is fulfilled utilization of the simulation during the design process of the actual satellite. Also the fast and reliable simulation allows us to take measure to adapt to environmental and internal changes.