Modeling and Preliminary Sizing of the Electrical Power Subsystem for the PdQSat Mission

Abstract

PdQSat is a 3U academic CubeSat developed at the Federal University of Minas Gerais for the in-orbit characterization of lithium–sulfur batteries and a supercapacitor. As the payloads are energy storage devices, thermal control is a critical driver for mission feasibility. In this work, different orbital scenarios were analyzed using Systems Tool Kit (STK) to estimate energy generation and define a feasible orbital envelope. Based on the resulting data, power budgets were developed for multiple operational scenarios. A dynamic Electrical Power Subsystem (EPS) model was implemented in MATLAB/Simulink using Supervisory Control Theory applied to Discrete Event Systems, integrating power generation, storage, consumption, and operational logic. Simulation results indicate that proper energy management, particularly of the payload thermal control, ensures positive energy margins and safe satellite operation. Higher altitudes and inclinations were identified as more favorable for EPS performance. Thermal control was confirmed as the most energy-demanding subsystem: duty cycles of 80% and 60% were energetically infeasible, while a 40% duty cycle was marginally acceptable under restrictions. Duty cycles of 20% or lower resulted in viable operation across all analyzed orbits, with minimum state of energy always above 77%. The proposed approach supports preliminary EPS sizing and provides guidance for thermal control requirements in CubeSat missions.