An efficient cell balancing method for LiFeP04 batteries based on inductors

Abstract

Nowadays, transportation is living through a great transformation motivated, among many other reasons, by the pollution caused by combustion vehicles. Faced with this change, other more renewable forms of transport, such as the electric car, are increasing and being introduced weighty in the market. Due to the great monopoly of the combustion car in recent years, this type of technology is not yet fully developed and there are many areas for improvement, especially in the plot of electric batteries. Within these devices, most of the studies and efforts are focusing on these two topics: - New materials for battery construction with better chemical characteristics, such as graphene. - New systems to supervisor and control the battery in a more efficient way, BMS (Battery Management System). Currently most companies design their BMS through capacitors, which decrease the cost and complexity of system control, in exchange for increasing the balancing time. This fact reduces the useful life of the cells. Motivated by the dissatisfaction of a market that tends to lead mobility soon, this thesis is studying, implementing, and developing an innovative cell balancing circuit through inductors. It is theoretically (through equations) and practically (through simulations) created to simulate the behavior of an electric vehicle battery. To obtain simulations and results that will make the industry think about the possible incorporation of this system to the electric vehicle, two types of balancing (with inductors and with capacitors), have been simulated and compared in the PSIM tool in three different situations .After visualizing the graphs of the three cell voltages, the cell power, and the total current of the circuit, it can be concluded that with the inductor method, more precision and speed is achieved when charging the inductors. The realization of a PSIM circuit with the same design but with a larger number of cells, as well as the integration of this three-cell circuit with physical elements, is being considered for future studies.