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Poloei, Fereshteh
Electric Vehicles , SOC , Battery Management System , Charging Equalization
One of the main challenges in power electronic applications is Battery Management System (BMS) that covers battery modeling, charging estimation, and charging control. Lithium Ion (Li-ion) batteries offer uncontested advantages over other types of batteries. They are used in many electronic devices such as cell phones, cameras, laptops, and are an important part of stand-alone wind and solar systems, smart grids applications, and Electric Vehicles (EVs). The goal of a battery management system (BMS) is to optimize the battery’s lifetime while improving the system’s stability, reliability, and cost. Among the factors involved in the battery management system (BMS), State of Charge (SOC) estimation and Charging Equalization (CE) among a set of batteries are of importance greater than the others. An appropriate and accurate modelling of the battery combined with an accurate and fast estimation scheme are required for a good estimation of the battery’s state of charge (SOC). In terms of charging equalization, the efficiency, modularity, algorithm simplicity, CE time, minimum added elements and cost, and maximum possible operation modes involved during CE process should be considered to have a more practical and advantageous CE method and topology. This research focuses on developing a new modelling and SOC estimation technique for Li-ion batteries as well as introducing a novel charging equalization algorithm and topology for all possible operation modes in a battery stack. This research work introduces a comprehensive but simple model for the battery and a novel accurate, fast, and online estimation method for a Li-ion cell and then proposes an innovative advantageous balancing algorithm that includes all modes of operation for a battery stack. Our proposed CE algorithm can not only balance the charge among the modules in the battery stack when it is connected to the grid, either in charging or discharge mode. It is also capable of charge equalizing when the battery stack is disconnected from the grid. This unique feature of our proposed method prolongs the battery life and improves the performance in a modular battery system. The proposed modelling and charging schemes are validated through comprehensive simulations and experimental results.
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