Multicell-to-Multicell Equalizers Based on Matrix and Half-Bridge <i>LC</i> Converters for Series-Connected Battery Strings

Shang, Yunlong; Zhang, Qi; Cui, Naxin; Duan, Bin; Zhou, Zhongkai; Zhang, Chenghui

doi:10.1109/jestpe.2019.2893167

Cited by 58 publications

(51 citation statements)

References 25 publications

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“…The efficiency was lower than 60%, and diode forward voltage drops were considered to be the dominant loss factor as it took a significant portion of the output voltage. The measured efficiency characteristic was somewhat inferior to that of conventional equalizers (e.g., 80% [31,35]). Nevertheless, the inferior efficiency performance would be acceptable in most applications because processed power in the equalizer is one-hundredth to one-thousandth that of a main converter [36,37].…”

Section: Measured Waveforms and Characteristics Of Equalizermentioning

confidence: 63%

“…The pack-to-cell equalizer with polarity switches (Figure 2c) can further reduce the switch count as low as n + 5 [27]. The direct cell-to-cell equalizer with an energy storage medium (Figure 2d), such as a capacitor, inductor, resonant tank, etc., can reduce the switch count as low as n + 1 [28][29][30][31][32][33][34][35], but selection switches in many existing direct cell-to-cell equalizer must operate at a high switching frequency, for which numerous high-frequency gate drivers are also indispensable. Furthermore, four unidirectional switches are also necessary in the case of the topology in Figure 2d.…”

Section: Figurementioning

confidence: 99%

“…The number of selection switches should desirably be reduced as much as possible to simplify the circuit and to reduce the cost. Meanwhile, cell-to-cell equalizers using cell selectin switches have been intensively developed for EV battery systems [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Target cells having the lowest or highest voltages in the pack are selected by the cell selection switches so that their stored energies are exchanged to equalize cell voltages, regardless of voltage drops across internal impedance.…”

Section: Figurementioning

confidence: 99%

“…With the proposed equalizer, on the other hand, the number of bidirectional selection switches and unidirectional switches can be reduced to as low as n and two, respectively, reducing the circuit complexity and cost. Furthermore, the selection switches in the proposed equalizer do not need to operate at a high frequency, and therefore, gate driver circuits for selection switches can be simpler and less powerful than those needed in conventional cell-to-cell equalizer using selection switches [28][29][30][31][32][33][34][35]. Although diodes D 1 -D 8 and smoothing capacitors C o1 -C o4 are additionally necessary for the voltage multiplier, these are passive components and do not need auxiliary circuits.…”

Section: Featuresmentioning

confidence: 99%

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Cell Voltage Equalizer Using a Selective Voltage Multiplier with a Reduced Selection Switch Count for Series-Connected Energy Storage Cells

2019

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Cell voltage equalization is mandatory to eliminate voltage imbalance of series-connected energy storage cells, such as lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs), to ensure years of safe operations. Although a variety of cell equalizers using selection switches have been proposed, conventional techniques require numerous switches in proportion to the cell count and are prone to complexity. This paper proposes a novel cell voltage equalizer using a selective voltage multiplier. By embedding selection switches into the voltage multiplier-based cell voltage equalizer, the number of selection switches can be reduced in comparison with that in conventional topologies, realizing the simplified circuit. A prototype for twelve cells was built, and an equalization test using LIBs was performed. The voltage imbalance decreased down to approximately 20 mV by the proposed equalizer, and the standard deviation of cell voltages at the end of the equalization test was as low as 10 mV, demonstrating its equalization performance.

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Section: Measured Waveforms and Characteristics Of Equalizermentioning

confidence: 63%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Featuresmentioning

confidence: 99%

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Cell Voltage Equalizer Using a Selective Voltage Multiplier with a Reduced Selection Switch Count for Series-Connected Energy Storage Cells

2019

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“…It is not conducive to the balancing system volume reduction. LC resonant balancing circuit [16][17][18] can transfer energy directly between any two cells, but require bulky magnetic components, high-voltage switches, a complex control algorithm, or prolonged balancing time when they are used to balance a pack that has high voltage and high capacity. Balancing topologies based on transformers have the advantages of simple control, high balancing efficiency, and easy isolation.…”

Section: Introductionmentioning

confidence: 99%

A Flyback Converter-Based Hybrid Balancing Method for Series-Connected Battery Pack in Electric Vehicles

Guo

Geng

Liu

et al. 2021

IEEE Trans. Veh. Technol.

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An active balancing method based on two flyback converters is proposed for series-connected battery pack. Balanced energy can be transferred between the whole battery and any single cell. The proposed topology reduces the number of energy storage components, the volume and the cost of the balancing system. And it has the characteristics of fast balancing speed and high balancing efficiency. Based on the topology, a dual-objective hybrid control strategy is proposed, which can reduce the highest voltage and boost the lowest voltage in the charging or discharging process of the cells in one sampling period, so as to improve the balancing speed. Simulation and experimental results show that the proposed method has a good balancing effect and can significantly improve the consistency of series battery pack. This work is potentially significant in terms of improved reliability of battery packs and savings of costs and lives in safety-critical applications.

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A bidirectional converter with integrated voltage equalizer for series‐connected supercapacitors

Yang

Jia

Wang

et al. 2022

Circuit Theory & Apps

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Energy storage systems include not only a charge/discharge bidirectional converter but also a separate voltage equalizer. This paper proposes a bidirectional converter with an integrated voltage equalizer, which saves a DC-AC converter, thus significantly reducing the size, cost, and complexity of the equalization circuit. In addition, integrating the equalizer into the bidirectional converter also has a positive impact on the realization of ZVS operation. Analytical models have been established that can be used for accurate prediction, optimal design, and effective control of the proposed converter. A control strategy is proposed, which not only enables the cells to be automatically balanced when the cell string is charged/discharged but also enables ZVS operation within a wide range of voltage changes and minimizes the RMS value of the primary current. An experimental prototype of 60 W applied to nine supercapacitors (SCs) in series was built, and the experimental results verified the theoretical analysis and demonstrated the characteristics of the proposed converter.bidirectional converter, supercapacitors (SCs), voltage equalizer, voltage multiplier 1 | INTRODUCTION Supercapacitors (SCs) have been widely used in portable electronic devices, regenerative energy systems, hybrid vehicles, uninterruptible power supplies, and so on, and because of their long service life, they are expected as an alternative to traditional rechargeable batteries. [1][2][3] Since the voltage of a single SC is low, typically 0-3.0 V, multiple SCs need to be connected in series to form a string to provide a higher voltage level. Due to the slight difference in characteristics between cells and the influence of the ambient temperature, the voltage of each cell in the series-connected SC string will gradually become unbalanced.Many methods for cell balancing have been proposed, each with different advantages and disadvantages. The active balance method transfers energy through an external circuit to achieve balance between the cells. According to the energy flow mode, these methods are classified into four types: cell-to-cell, cell-to-string, string-to-cell, and cell(s)-tostring-to-cell(s). 4 Compared with other types of equalizers, string-to-cell equalizers can achieve cell balance through a single power conversion stage. The number of active switches in these equalizers is usually small, and the control method is relatively simple. The low complexity of these equalizers is very attractive, especially suitable for small-and medium-sized energy storage systems.

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Multicell-to-Multicell Equalizers Based on Matrix and Half-Bridge LC Converters for Series-Connected Battery Strings

Cited by 58 publications

References 25 publications

Cell Voltage Equalizer Using a Selective Voltage Multiplier with a Reduced Selection Switch Count for Series-Connected Energy Storage Cells

Cell Voltage Equalizer Using a Selective Voltage Multiplier with a Reduced Selection Switch Count for Series-Connected Energy Storage Cells

A Flyback Converter-Based Hybrid Balancing Method for Series-Connected Battery Pack in Electric Vehicles

A bidirectional converter with integrated voltage equalizer for series‐connected supercapacitors

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