Abstract.-The use of battery cell equalizers is mandatory in order to assure that all the cells connected in series are charged to its maximum capacity, even when they present small differences in this parameter due to several factors, such as aging, manufacturing or temperature. Active equalizers, with a higher efficiency in comparison to passive ones, have the disadvantage of using a considerable number of components. Moreover, in the case of active equalizers with very high performance, this number can be even higher. In this paper, the use of the wave-trap concept, widely used in telecommunication systems, is studied. This concept allows the battery cell equalizer to use its switching frequency as the control variable that decides which cell is being charged. Hence, it is not necessary to use a complex system based on a high number of controlled switches in order to determine which cell is being charged. In this way, the number of switches (and the corresponding driving signals) can be strongly minimized without reducing the performance of the system. In order to proof the validity of this concept (i.e., wave traps) in the design of battery-cell equalizers, a topology based on a half-bridge structure is also proposed in this paper. It uses only two controlled switches in order to decide which cell is charged. Experimental results are provided for a 4-cell equalizer as a proof of concept.
Abstract-This paper is about the decentralization and distribution of a Kalman filter for fractional order systems. A fractional order discrete state space for a global system is introduced and divided into different submodules. The distribution of the model and of the state estimation algorithm into submodules leads to small and scalable units, which do not need a central processing node. Each submodule performs its computation locally. All information required by other nodes is communicated between the nodes directly. Finally, an example is given to compare the fractional Kalman filter (FKF) for the overall system with the distributed and decentralized fractional Kalman filter (DDFKF).
Temperature is one of the key factors when working with lithium-ion battery modules due to its influence in safety, performance, and lifespan concerns in these devices. High working temperatures reduce the available capacity of each cell within the module after several cycles due to aging; nonuniform temperature distributions in the module lead to different aging processes in each cell, and thus it will be impossible to take advantage of all the energy available in the Li-ion storage system, because the most aged cell will limit the available energy. This paper is focused on the minimization of the maximum temperature gradient of a battery module for high depth of discharge applications to avoid different aging processes of the cells within the module. Voltage balancing is proposed as a solution for this purpose, and different strategies and their results are presented in this paper.
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