The nanosatellites require a power conditioning unit (PCU), which is responsible of the management and administration of the power used by different subsystems of the satellite. It is necessary carry out simulations that verify the performance of this unit given the conditions that arise during the operation of the mission. A PCU was designed based on components commercial off the shelf (COTS) through the evaluation of different configurations and the operation of each one was verified through simulations. The analysis and design of the evaluated configurations are presented, which show the operation of the algorithm of maximum power point tracking, charge regulation in the battery, power conditioning buses and the protection system against overcurrent peaks. According to the results, the propose designs meet the power requirements of the satellite and will be validated experimentally.