ارائه ساختار مبدل و الگوريتم براي متعادل‌سازي وضعيت شارژ سلول‌هاي باتري‌هاي ليتيومي مبتني بر روش هيسترزيس

With the advancement of electric vehicle technologies, the effective an‎d reliable use of rechargeable batteries has become a key concern for automobile manufacturers. Among rechargeable batteries, lithium-ion types are the most well-known. Their unique characteristics including high specific energy, high specific power, an‎d low self-discharge rate have made them widely used in electric vehicles. Lithium-ion battery packs are not integrated units; rather, they are composed of a large number of individual cells. These cells are small battery units with relatively low voltage, capacity, an‎d power. To provide the voltage an‎d current required by electric vehicles, the cells are connected in series an‎d parallel configurations. Although the cells used in a battery pack are selec‎ted from the same bran‎d an‎d with identical factory specifications, they are not completely identical an‎d differ in capacity, internal resistance, internal voltage, aging rate, an‎d other parameters. These inconsistencies originate both from internal factors (such as manufacturing variations) an‎d external factors (such as the arrangement of cells within the pack an‎d the heat transfer conditions). Such differences in a series string of cells limit the performance of that string, an‎d ultimately the entire battery pack. For example, a cell with lower capacity compared to the others in the series string will reach full discharge sooner during operation. As a result, the entire series string becomes unable to deliver power even if the remaining cells still have charge. These inconsistencies reduce usable capacity, accelerate cell aging, an‎d introduce significant safety risks such as overcharging an‎d battery explosion. A balancing controller is a vital component of the battery management system in all electric vehicles an‎d plays an important role in increasing battery lifespan an‎d ensuring safety. This research introduces various methods for balancing battery cells connected in series. There are many cell-balancing techniques, generally categorized into passive an‎d active methods. Each category includes several sub-types, which are described in this work. The topologies, operating principles, power circuits, an‎d different operating modes of each method are explained. Each topology has its own advantages an‎d disadvantages, an‎d these are compared accordingly. The parameters on which the balancing process is based are discussed as well, along with the benefits, drawbacks, an‎d effectiveness of each parameter in achieving cell balancing. One class of balancing methods examined in this study is the inductor-based approach. This method has gained more attention due to its advantages over other methods, including cost-effectiveness, fast response time, fewer circuit components, simpler control, an‎d more. In this research, a new balancer with a novel topology an‎d control strategy is proposed. This balancer uses an inductor as the energy-storage element an‎d is capable of transferring energy between any two cells in the series string. As a result, it offers advantages such as high speed, high accuracy, an‎d high efficiency. Since this strategy avoids unnecessary charging an‎d discharging of the batteries, it produces less heat an‎d increases battery lifespan. Using this converter, series-connected batteries can be balanced quickly an‎d accurately.

محمد سعيد مهدوي

حميدرضا كارشناس , احمدرضا تابش