A Switch-Reduced Multicell-to-Multicell Battery Equalizer Based on Full-Bridge Bipolar-Resonant LC Converter

Abstract

Many battery equalizers have been proposed to achieve voltage consistency between series connected battery cells. Among them, the multicell-to-multicell (MC2MC) equalizers, which can directly transfer energy from consecutive more-charged cells to less-charged cells, can enable fast balancing and a high efficiency. However, due to the limitations of the equalizers, it is not possible to achieve fast equalization and reduce the size of the circuit at the same time. Therefore, a MC2MC equalizer based on a full-bridge bipolar-resonant LC Converter (FBBRLCC) is proposed in this paper, which not only implements MC2MC equalization, but also greatly reduces the circuit size by reducing the number of switches by nearly half. A mathematical model and simulation comparison with conventional equalizers are used to illustrate the high-speed equalization performance of the proposed equalizer and excellent balancing efficiency. An experimental prototype for eight cells is built to verify the performance of the proposed FBBRLCC equalizer and the balancing efficiencies in different operating modes are from 85.19% to 88.77% with the average power from 1.888 W to 14.227 W.

Voltage Equalization of Series Energy Storage Unit Based on LC Resonant Circuit

“…According to the energy transfer path, non-energy consuming equalization circuits can be broadly classified into five categories: Pack-to-cell (P2C), [11][12][13] Cell-topack(C2P), [14][15][16] Directcell-to-cell(DC2C), [17,18] Adjacent cell-tocell (AC2C), [19][20][21] and multicell-to-multicell (MC2MC). [22][23][24][25] The P2C equalization circuit can transfer energy from a series storage unit to a lower voltage monomer. The utilization of a push-pull converter and a distributed control strategy is proposed for the implementation of a P2C balancing circuit in.…”

“…An AC2C equalization circuit based on tri-resonant state LC cells was proposed in, [20] which can achieve a high equalization speed when the voltage gap between the energy storage monomers is small, but its equalization speed and efficiency decrease with the increase in the number of cells. Considering the advantages and limitations of the above equalization circuits, a multi-monomer-to-multi-monomer (MC2MC) equalization circuit was proposed in, [23][24][25] which can transfer energy from the cell with more charging to the cell with less charging. Shang et al [23] proposed the half-bridge LC converter (HBLCC) is unable to achieve boost conversion, which slows down the equalization speed.…”

“…According to the energy transfer path, non‐energy consuming equalization circuits can be broadly classified into five categories: Pack‐to‐cell (P2C), [ 11–13 ] Cell‐to‐pack(C2P), [ 14–16 ] Directcell‐to‐cell(DC2C), [ 17,18 ] Adjacent cell‐to‐cell (AC2C), [ 19–21 ] and multicell‐to‐multicell (MC2MC). [ 22–25 ]…”

A multicell-to-multicell battery equalizer with more balancing modes based on half-bridge bipolar-resonant LC converter

“…In contrast, non-dissipative techniques use energy storage elements to transfer energy from strong cells to weak cells, avoiding waste of imbalanced energy and improving the pack's capacity [21]- [23]. Non-dissipative voltage equalizers can be further categorized based on their balancing paths, including adjacent-cell-to-cell (AC2C) equalizers [24]- [26], direct cell-to-cell (DC2C) equalizers [27]- [29], any-cell-to-any -cell (AC2AC) equalizers, cellto-pack (C2P) equalizers [30], pack-to-cell (P2C) equalizers [31], and multicell-to-multicell (MC2MC) equalizers [32,33]. The AC2C equalizers equalize adjacent cells but only transfer energy between two cells, leading to slow balancing speed and low efficiency as the number of cells increases.…”

“…However, the half-bridge LC converter (HBLCC) used in [32] lacks step-up conversion, which limits its balancing speed. To address this, a full-bridge bipolar-resonant LC converter (FBBRLCC) equalizer was introduced in [33]. This converter improves balancing speed and power by enabling its LC resonant tank to resonant in a bipolar manner.…”