Conversor síncrono CC-CC para ensaio de carga e descarga de baterias de íons de lítio

Abstract

The present work aims at the implementation and functional validation of a DC-DC converter for charging and discharging tests applied on lithium ion battery packs. Initially, a bibliographic review of the subjects included in the work was carried out. Next, the synchronous converter topology was defined, semiconductor switches were chosen, and then, an LCL filter was designed for current ripple attenuation on the batteries. For control loop design, first, system dynamics had to be modeled, a state-space model for the LCL filter, a first order transfer function for the energy in the DC bus and a for battery voltage dynamics. Next, satisfactory strategies for control loops were considered: full state feedback with servomechanism to current control in the filter magnets, and PI controllers for the other loops. Considering the need for closed loop control, measuring instruments were developed, these were conditioned to the electrical characteristics of the electronic system and calibrated in practical tests. Still regarding the measurement of the system variables, a Luenberger state observer was implemented to estimate the voltage on the LCL filter capacitor. For the proposed general features implementation, the digital signal processor was programmed in C language, unifying the processing of the measured variables, control laws calculation, battery charge and discharge algorithms and the signal modulation applied to the actuators. Finally, the proposed system was built and submitted to validation tests, experiment results shown satisfactory results regarding the project objectives.