http://chglib.icp.ac.ru/subjex/2014/pdf03/JPowerSources-2014-254()168.pdf

A review of lithium deposition in lithium-ion and lithium metal secondary batteries

In electric vehicle (EV) energy storage systems, a large number of battery cells are usually connected in series to enhance the output voltage for motor driving. The difference in electrochemical characters will cause state-of-charge (SOC) and terminal voltage imbalance between different cells. In this paper, a hybrid cascaded multilevel converter which involves both battery energy management and motor drives is proposed for EV. In the proposed topology, each battery cell can be controlled to be connected into the circuit or to be bypassed by a half-bridge converter. All half-bridges are cascaded to output a staircase shape dc voltage. Then, an H-bridge converter is used to change the direction of the dc bus voltages to make up ac voltages. The outputs of the converter are multilevel voltages with less harmonics and lower dv/dt, which is helpful to improve the performance of the motor drives. By separate control according to the SOC of each cell, the energy utilization ratio of the batteries can be improved. The imbalance of terminal voltage and SOC can also be avoided, fault-tolerant can be easily realized by modular cascaded circuit, so the life of the battery stack will be extended. Simulation and experiments are implemented to verify the performance of the proposed converter.

A Hybrid Cascaded Multilevel Converter for Battery Energy Management Applied in Electric Vehicles

This paper proposes a power converter architecture for the implementation of an ultrafast charging station for electric vehicles (EVs). The versatile converter topology is based on the concept of the power electronic transformer. For the direct transformerless coupling to the medium-voltage grid, a cascaded H-bridge (CHB) converter is utilized. On the level of each submodule, integrated split battery energy storage elements play the role of power buffers, reducing thus the influence of the charging station on the distribution grid. The power interface between the stationary split storage stage and the EV batteries is performed through the use of parallel-connected dual-half-bridge dc/dc converters, shifting the isolation requirements to the medium-frequency range. By choosing several different submodule configurations for the parallel connection, a multiport output concept is achieved, implying the ability to charge several EVs simultaneously without the use of additional high-power chargers. All possible charging station operating modes among with the designed necessary control functions are analyzed. The state-of-charge self-balancing mode of the delta-connected CHB converter is also introduced. Finally, the development of a downscaled laboratory prototype is described, and preliminary experimental results are provided.

A Modular Multiport Power Electronic Transformer With Integrated Split Battery Energy Storage for Versatile Ultrafast EV Charging Stations

Charging optimization in lithium-ion batteries based on temperature rise and charge time

Lithium-ion batteries: Evaluation study of different charging methodologies based on aging process

A rapid charge strategy based on the residual energy evaluation is proposed for LiFePO $_{4}$ (LFP) batteries to reduce charging time and improve charging performance. In the approach, the residual energy model was formulated based on the measured terminal voltage with respect to a certain state of charge value. Subsequently, the stored energy of an LFP battery was evaluated by using the obtained voltage characterizations. This is followed by the difference calculated between the fully stored energy and the residual energy such that the suitable time to enact the high-rate charge is determined, thereby ensuring a battery of full capacity in stable, safe, and nonovercharged conditions. Moreover, for the hysteresis effects that may affect the battery voltage evaluation, they are also included in the charge process in this study. In order to validate the method, this proposed strategy has been examined from perspectives of charge time, charge efficiency, and the number of charge cycles. Compared with other charge strategies, both the charge time and the charge efficiency are highly improved, hence confirming the feasibility of the method for energy storage applications.

Fast Charge Strategy Based on the Characterization and Evaluation of LiFePO $_{\bm 4}$ Batteries

Comprehension of open-circuitvoltage (OCV) function and battery impedance can be used to evaluate the residual energy and dynamic voltage response of lithium batteries. However, noise contamination during data sampling may affect the accuracy of the derived OCV function and battery impedance extraction, resulting in a poor evaluation performance. By aiming at formulating a more representative circuit-based model, this study proposes a hybrid averaging method along with an impedance network observation approach that is embedded within a time-frequency localisation method, anticipating eliminating the influences of sampling noise such that the characterisation of the OCV function and battery impedances can be better ensured. In such an integrated approach, the trimmed relevance vector regression is also added, which is followed by two cascaded R-C networks in order to fit the characteristics of battery impedances. Through the method proposed in this paper, it is found that the average error can be decreased to be less than 20 mV. Both battery residual energy and I-V performance are more effectively comprehended.

An approach to measurements of electrical characteristics of lithium-ion battery with open-circuit voltage function

A matching design for the cooperation of super-capacitor and Lithium-ion battery in electric wheel motors is proposed in this paper. This concept is originated with anticipation of grasping the power delivery through the control of switching time between the super-capacitor and lithium-ion battery, by which the excessive energy of lithium-ion battery can be dissipated to each cell such that the battery equalizer can be reached, while the super-capacitor is meanwhile served as the energy-recycling device to accomplish the energy-saving goal. This proposed approach has been realized as the laboratory prototype, by which the simulations are validated with satisfactory test results.

A matching design for ultra-capacitor and Li-ion battery cooperation in electric wheel motors

This paper is aimed to develop a Li-ion battery charger with the intelligent decisions based on OCV information of the battery. In this method, the OCV function can be formulated through the measurement of output voltage with respect to a certain SOC value. Then using the obtained dynamics of battery intrinsic, a fast charging method can be developed to reach speedy and full charge without entering over-charging area. The method proposed in this paper is examined under various scenarios. The results help consolidate the feasibility and practicability of the approach for the applications considered.

Design of a Lithium-iron battery charger with the open-circuit voltage function evaluation

This paper proposes a contactless energy-transfer system (CETS) for lithium iron phosphate battery-charging circuits. In the study, the design flow of contactless transformers and compensated circuit are investigated through the analysis of their impedance-matching and resonant features, by which the appropriate inductive coils can be optimally determined such that power transmission efficiency can be increased. Moreover, an algorithm of charging strategy is integrated into the microcontroller chip to facilitate the charging process. From theoretical analysis and hardware realization, they help support the proposed approach applied for the performance improvement of lithium iron phosphate battery-charging applications.

Bo-Ge Huang

Papers

Fast Charge Strategy Based on the Characterization and Evaluation of LiFePO $_{\bm 4}$ Batteries

An approach to measurements of electrical characteristics of lithium-ion battery with open-circuit voltage function

A matching design for ultra-capacitor and Li-ion battery cooperation in electric wheel motors

Design of a Lithium-iron battery charger with the open-circuit voltage function evaluation

Contactless energy-transfer system design for lithium iron phosphate battery-charging circuits