Abstract
This study developed and implemented a LiFePO4 battery pack (LBP) rapid charger. Using the three-terminal switch and partnership for a new generation of vehicles (PNGV) battery models, this study could obtain a small-signal system matrix to derive transfer functions and further analyze frequency responses for the charge voltage and current loops; therefore, both voltage and current feedback controllers could be designed to fulfill the constant-voltage (CV) and constant-current (CC) charges. To address practical applications, the proposed equivalent model also considered the wire resistance-inductance of the power cable. According to the derived high-order transfer function, the pole-zero break frequency in the Bode plot was observed that approximated the practical measurement; therefore, the pole-zero compensation could be accomplished for both charge loop requirements. Moreover, the design features for implementing the CV and CC charges are presented in detail herein, and the current overshoot during the start-up phase could be mitigated using the method of zero break frequency shifting and a novel proportional shifting proportional-integral control. The LBP parameter estimations, model construction processes, and frequency response analyses are also presented. The feedback compensation design based on the proposed model was validated through simulations and experiments. The results were determined to be in excellent agreement with theoretical derivations.
Highlights
The greenhouse effect, resulting in climate change, has become a major problem, and ecofriendly technologies for producing clean energy are paramount to alleviating greenhouse gas emissions.Commonly-used rechargeable batteries including lead-acid, Ni-Cd, Ni-MH, and Li-ion batteries have been applied in smartphones, laptops, electric screwdrivers, and other portable instruments as well as in electric forklifts and other electric vehicles
LiFePO4 battery pack (LBP); this study focused on the voltage feedback controller (VFC) design for the CV output operation of LBP rapid charger (LBPRC), and the current feedback controller (CFC) design for the CC output operation of LBPRC
An optimum charge strategy can be determined by the battery management system (BMS), rather than the LBPRC
Summary
The greenhouse effect, resulting in climate change, has become a major problem, and ecofriendly technologies for producing clean energy are paramount to alleviating greenhouse gas emissions.Commonly-used rechargeable batteries including lead-acid, Ni-Cd, Ni-MH, and Li-ion batteries have been applied in smartphones, laptops, electric screwdrivers, and other portable instruments as well as in electric forklifts and other electric vehicles. The greenhouse effect, resulting in climate change, has become a major problem, and ecofriendly technologies for producing clean energy are paramount to alleviating greenhouse gas emissions. Compared with other secondary batteries, Li-ion batteries have the highest power and energy density [1]; Li-ion cells inside a battery pack are a suitable choice for electric vehicles [1,2,3]. The Lithium iron phosphate (LiFePO4 ) is suitable for the positive electrode material in batteries because the strong P–O covalent bonds in the LiFePO4 lattices do not decompose . The LiFePO4 battery possesses excellent thermal stability; even under high-temperature or overcharge conditions, they rarely overheat because the LiFePO4 lattice does not collapse and oxidize. LiFePO4 batteries are suitable for powering electric vehicles because they offer multicycle
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