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Based on a low cost multi-switched inductor balancing circuit (MSIBC), a fuzzy logic (FL) controller is proposed to improve the balancing performances of lithium-ion battery packs instead of an existing proportional-integral (PI) controller. In the proposed FL controller, a cell’s open circuit voltages (OCVs) and their differences in the pack are u...
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... goal of the balancing operation is to equalize the cells' SOCs. The measured battery terminal voltage is only a rough indicator of the SOC as the terminal voltage consists of three components; namely, open circuit voltage (OCV), polarization voltage, and voltage drop across internal resistances [9,25,35]. Of these, only the OCV directly reflects the SOC. To find the OCV, a commonly-used equivalent circuit model (ECM) of a battery is adopted, as shown in Figure 5 can be ignored [9]. Therefore, the OCV can be approximately calculated ...
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Citations
... Various active equalization methods have been explored, including resistor-based, capacitor-based, and inductor-based techniques. Among these, inductor-based active cell equalization has shown promise for its efficiency and effectiveness [3,4]. ...
Ultracapacitors, known for their high power density and long cycle life, are widely used in various applications. However, when ultracapacitor cells are connected in series, voltage imbalances can occur, limiting overall energy storage capacity and system performance. This paper presents an investigation into inductor-based active cell equalization techniques for ultracapacitor energy storage systems. The proposed approach utilizes inductors, switching devices, and control circuitry to efficiently balance cell voltages. By monitoring cell voltages and activating switching devices when predetermined thresholds are exceeded, energy is transferred from higher voltage cells to inductors during the charging phase. In the subsequent discharging phase, the stored energy is released, equalizing the cell voltages. This iterative process continues until voltage balance is achieved. Inductor-based active cell equalization offers advantages such as rapid voltage equalization, wide voltage range operation, and electrical isolation between cells. However, challenges include system complexity, cost, and losses introduced by switching devices. Ongoing research focuses on optimizing design and control strategies to improve energy efficiency and address these challenges. The proposed technique shows promise in maximizing energy storage capacity and enhancing the performance and lifespan of ultracapacitor systems. This circuit could balance the capacity of the ultracapacitor in 2.3 seconds with a voltage ripple of 0.0038 V (0.18 %). Further advancements are expected to promote the widespread adoption of inductor-based active cell equalization in diverse applications. (Abstract)
... A voltage sensor and complex control are usually required in the inductor-based voltage-equalizer circuits. Their control circuits are divided into two PI and fuzzy types [175], [176], [177]. In the PI controller type, maximum current value is calculated according to the [144], and (c) full-bridge phase-shift converter [142]. ...
... The controller output signal is the balancing current. In this type of controller, the current is flexible and the speed is optimal [175]. ...
... Fuzzy controller block diagram[175]. ...
Voltage unbalances of the series-connected battery and supercapacitor cells are mainly due to their differences in materials, manufacturing technology, internal specifications, temperature, initial charge, etc. This voltage difference can reduce the battery or supercapacitor pack capacity, stored energy, efficiency, and lifespan. Various methods have been proposed to overcome this issue to avoid its disadvantages. Generally, voltage equalizer circuits are divided into active and passive categories. The passive methods consume high-voltage cells energy as heat, and they are widely used in non-sensitive applications, due to their low cost and volume, high reliability, and expandability. However, these equalizer circuits are not used in sensitive applications, due to their power losses, heat generation, and low efficiency. To overcome these problems, the active balancing methods have been proposed, which transfer energy from high-voltage cells to low-voltage cells. However, these methods have complex structures and control circuits. In this paper, different types of batteries and supercapacitors and their optimum combinations are investigated, first. Then, the active and passive equalizer circuits are examined and compared, in detail. In addition, their different control methods have been studied to choose the most suitable circuit and its control method for a desired application.
... Fig. 4 shows the difference in voltage estimation between the Rint and Thevenin model when a constant current is applied. Based on the assumption of adequate sampling speed in voltage sensing for battery [40], [41], the diffusion effect of Cth can be neglected so that the lithium-ion batteries can reach the steady-state condition quickly [42], [ ...
The battery performance decreases as the charging/discharging cycles increase. Thus, a battery management system (BMS) is essential to properly estimating the battery states. In order to enhance the performance of the BMS, an accurate estimation method for lithium-ion batteries state is proposed. The main drawback of the coulomb counting method (CCM) for estimating a state of charge (SoC) is the error of initial value. To make-up this problem, the open circuit voltage (OCV) method which includes the internal resistance of the battery has been applied to update the initial value. In this paper, an enhanced coulomb counting (ECC) method is proposed to improve the accuracy of SoC estimation. Due to the battery aging by repeated charging/discharging cycles, the charging/discharging times become reduced and it can be formulated as a function of coulombic efficiency. Using the power equation to the battery, the state of health (SoH) can be estimated according to the change in the internal resistance. In the proposed flowchart, after the completion of charging/discharging in the
k
cycle, the internal resistance, coulombic efficiency, and capacities are calculated and those resultants will be utilized in
k
+
1
cycle. The proposed methods are verified by 3 kW energy storage system and the comparative experiment results are also presented to point out its effectiveness.
... In switched IBCB, the transfer of charge is possible between neighbouring cells, gradually balancing all the cells present in the pack. The disadvantage of this method is that the time taken for balancing is directly proportional to the number of batteries in the overall chain [20], [34], [36]. ...
The performance of a battery pack is greatly affected by an imbalance between the cells. Cell balancing is a very important criterion for Battery Management System (BMS) to operate properly. This paper presents the various cell balancing topologies which have been presented by various researchers in the past years. A novel topology has also been discussed, which improves the overall efficiency of the components being used. Various comparison parameters such as Control, Speed, Efficiency, Power Effects, Manufacturability, Size, and Cost have been considered.
... The Coulomb counting method suffers from accumulated current sensing error and the initial SOC must be known [38]. The OCV is a more accurate indication of the SOC than the terminal voltage because the OCV accounts for the voltage drop across the series resistance of the battery [2,[39][40][41][42][43][44][45]. The values of cell current and battery series resistance are needed to estimate this voltage drop. ...
... Consequently, this might result in exceeding the current rating of the inductor. Non-fixed duty cycle schemes of balancing converters between series-connected battery cells are proposed in the literature for different balancing topologies, but not for the switched-inductor topology shown in Fig. 1(a), such as in [39,41,51]. ...
... The current in the fixed-duty-cycle scheme is variable and does not yield operating at maximum efficiency point for minimum power losses [4,19,28,34]. This is also the case for other topologies with non-fixed duty cycle scheme [39,41,51]. ...
This paper presents a current-mode controller for switched-inductor topology to achieve voltage balancing between battery cells or modules in a battery pack while operating at peak efficiency. The presented method yields several advantages and/or eliminates several drawbacks of the existing conventional fixed duty cycle scheme. Among these advantages: (1) the balancing current is well controlled instead of being a function of battery cells' voltages and system parasitic elements which might result in exceeding the current ratings of the components, and (2) the balancing current reference is selected such that the balancing circuit operates at its maximum efficiency point and therefore yielding lower balancing power losses. This paper also presents a battery balancing algorithm for utilization with the presented controller that achieves open circuit voltage balancing which is a more accurate indicator of State-Of-Charge (SOC) compared to terminal voltage. Experimental results obtained from a laboratory prototype of a 3-cell battery pack are presented to evaluate the presented current control and balancing method under different modes of operation.
... Single inductor configuration use only one inductor to transfer energy from a high-voltage cell to the entire battery pack which reduces magnetic losses [101]. Multi-inductor topologies transfer energy between neighboring cells (cell-to-cell) due to which it takes more balancing time than a single-inductor typology which renders the system inefficient for applications using large battery strings, such as EVs [102,103]. Transformer-based balancers are classified into three main categories: single-winding, multi-winding, and multiple transformers [104]. The single-winding transformer uses a single winding on both primary and secondary sides to achieve cell-to-pack/pack-to-cell charge transfer [105]. ...
As the battery provides the entire propulsion power in electric vehicles (EVs), the utmost importance should be ascribed to the battery management system (BMS) which controls all the activities associated with the battery. This review article seeks to provide readers with an overview of prominent BMS subsystems and their influence on vehicle performance, along with their architectures. Moreover, it collates many recent research activities and critically reviews various control strategies and execution topologies implied in different aspects of BMSs, including battery modeling, states estimation, cell-balancing, and thermal management. The internal architecture of a BMS, along with the architectures of the control modules, is examined to demonstrate the working of an entire BMS control module. Moreover, a critical review of different battery models, control approaches for state estimation, cell-balancing, and thermal management is presented in terms of their salient features and merits and demerits allowing readers to analyze and understand them. The review also throws light on modern technologies implied in BMS, such as IoT (Internet of Things) and cloud-based BMS, to address issues of battery safety. Towards the end of the review, some challenges associated with the design and development of efficient BMSs for E-mobility applications are discussed and the article concludes with recommendations to tackle these challenges.
... Non-dissipative balancing utilizes capacitors [59], [60], inductors [61], [62], transformers [63]- [65], and various common power electronic converter topologies [66]- [70] to transfer the energy among the cells within the pack. Energy is transferred from more charged to less charged cells, preventing the waste of energy present for dissipative methods. ...
... For inductor-based methods, one or more inductors are utilized for cell balancing [61], [62]. The single-inductor balancing system utilizes one inductor to transfer the energy between the pack to the weakest cells [61]. ...
... The control system selects the weakest cell with the lowest SOC level to transfer the energy through activating the corresponding switches. The multi inductor method utilizes n-1 inductor for balancing n cells, [62]. The controller senses the voltage difference of the two neighboring cells, then a control signal is applied to the switches with the condition that the higher cell must be switched on first to transfer the energy to the weakest cell. ...
Lithium-Ion battery packs are an essential component for electric vehicles (EVs). These packs are configured from hundreds of series and parallel connected cells to provide the necessary power and energy for the vehicle. An accurate, adaptable battery management system (BMS) is essential to monitor and control such a large number of cells. Series and parallel connected cells also experience different production and operational conditions, which makes it challenging for the BMS to ensure the safe operation of each individual cell. The main functions of the BMS include battery state estimation, cell balancing, thermal management, and fault diagnosis. Robust estimation of the state of charge (SOC) is crucial for providing the driver with an accurate indication of the remaining range. This paper presents the state of art of battery pack SOC estimation methods along with the impact of cell inconsistency on pack performance and SOC estimation. Cell balancing methods, which are necessary due to cell inconsistencies, are discussed as well. Four categories of pack SOC estimation methods are presented, including individual cell, lumped cell, reference cell, and mean cell and difference estimation methods. The SOC estimation methods are compared in terms of algorithm type, computational load, and engineering effort to help practitioners decide which method best fits their application.
... Active equalizer circuits have been widely studied in order to achieve more efficient equalization and typically employ energy interchanging components, such as capacitors, inductors, and transformers, as well as power converters for exchanging energy between high-and low-SOC batteries. Depending on type of used component, the active equalizer circuits can be classified into capacitor-based equalizers [35]- [38], [40]- [42], [45]- [50], inductor-based equalizers [35]- [38], [40], [51]- [54], transformer-based equalizers [55]- [59] and converter-based equalizers [60]- [67], as shown in Figure 2 ...
... But, it takes a long time for balancing the end to end cell in a high string battery pack. 56 Hence, the inductor based balancing techniques can be executed for high power applications such as hybrid electric vehicles and electric vehicles. The advantage of this technique is high balancing current which provides a fast balancing time and high efficiency than capacitorbased topology, and smaller production cost than transformer-based topology. ...
Li‐ion batteries are influenced by numerous features such as over‐voltage, under voltage, overcharge and discharge current, thermal runaway and cell voltage imbalance. One of the most significant factors is cell imbalance which varies each cell voltage in the battery pack overtime and hence decreases battery capacity rapidly. So as to increase the lifetime of the battery pack, the battery cells should be frequently equalized to keeps up the difference between the cells as small as possible. There are different techniques of cell balancing have been presented for the battery pack. It is classified as passive and active cell balancing methods based on cell voltage and state of charge (SOC ). The passive cell balancing technique equalizing the state of charge of the cells by the dissipation of energy from higher SOC cells and formulates all the cells with similar SOC equivalent to the lowest level cell SOC . The active cell balancing transferring the energy from higher SOC cell to lower SOC cell, hence the SOC of the cells will be equal. This review article introduces an overview of different proposed cell balancing methods for Li‐ion battery can be used in energy storage and automobile applications.
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... The advantages are that it is easy to implement, has a simple structure, and a simple control, but it is not suitable when the batteries that need to be balanced are numerous. A multi-switched inductor equalization circuit is designed in [25], and an inductor based equalization circuit is proposed in [26] for constant-voltage/current charging and discharging, their topologies are simple and easy to control, but could only transfer energy between adjacent batteries. An interleaved equalization architecture based on a resonant LC converter and buck converter is proposed in [15], which can exchange energy from a battery module to the next adjacent battery module and from a battery module to a cell, and achieve high equalization efficiency and a large equalization current. ...
The power from lithium-ion batteries can be retired from electric vehicles (EVs) and can be used for energy storage applications when the residual capacity is up to 70% of their initial capacity. The retired batteries have characteristics of serious inconsistency. In order to solve this problem, a layered bidirectional active equalization topology is proposed in this paper. Specifically, a bridge-type equalization topology based on an inductor is adopted in the bottom layer, and the distributed equalization topological structure based on the bidirectional BUCK-BOOST circuit is adopted in the top layer. State of charge (SOC) is used as the equalization target variable, and the bottom layer equalization algorithm based on a "partition" idea and route optimization is proposed. The static equalization experiments and charge equalization experiments are performed by the 12 retired batteries selected from an electric sanitation vehicle. The results show that the proposed equalization method can reduce the SOC difference between retired batteries and can effectively improve the inconsistency of the retired battery pack with a faster equalization speed.
