Abstract of Thesis presented at COPPE/UFRJ as a partial fulfillment of the requirements for the degree of Master of Science (M.Sc.)

State of Charge Estimation and Battery Balancing Control

André Abido Figueiró

December/2015

Advisors:

Ramon Romankevicius Costa Alessandro Jacoud Peixoto

Department:

Eletrical Engineering

      In this paper, the issue of battery cells state of charge (SoC) balancing is studied. An equivalent electric circuit dynamic model is proposed for a LiFePO₄ battery cell. The model parameters are identified and two passive balancing algorithms are proposed, tracking the minimum and medium SoC among the cells. The stability analysis of the state feedback is done for the proposed algorithms. Output feedback versions of the balancing algorithms are implemented via Kalman Filters (Extended Kalman Filter and Unscented Kalman Filter) and the closed loop performance is evaluated via numeric simulations and experiments. For the case when the SoC is not available and, in addition, the cell parameters are unknown, a novel SoC/parameter joint estimator is developed for a class of nonlinear cells via amplitude demodulation and online normalized least squares estimation techniques.