Fractional Differential Equations

Critical review of the methods for monitoring of lithium-ion batteries in electric and hybrid vehicles

The electric vehicle (EV) technology addresses the issue of the reduction of carbon and greenhouse gas emissions. The concept of EVs focuses on the utilization of alternative energy resources. However, EV systems currently face challenges in energy storage systems (ESSs) with regard to their safety, size, cost, and overall management issues. In addition, hybridization of ESSs with advanced power electronic technologies has a significant influence on optimal power utilization to lead advanced EV technologies. This paper comprehensively reviews technologies of ESSs, its classifications, characteristics, constructions, electricity conversion, and evaluation processes with advantages and disadvantages for EV applications. Moreover, this paper discusses various classifications of ESS according to their energy formations, composition materials, and techniques on average power delivery over its capacity and overall efficiencies exhibited within their life expectancies. The rigorous review indicates that existing technologies for ESS can be used for EVs, but the optimum use of ESSs for efficient EV energy storage applications has not yet been achieved. This review highlights many factors, challenges, and problems for sustainable development of ESS technologies in next-generation EV applications. Thus, this review will widen the effort toward the development of economic and efficient ESSs with a longer lifetime for future EV uses.

Review of energy storage systems for electric vehicle applications: Issues and challenges

Plug-in hybrid electric vehicles (PHEVs) offer an immediate solution for emissions reduction and fuel displacement within the current infrastructure. Targeting PHEV powertrain optimization, a plethora of energy management strategies (EMSs) have been proposed. Although these algorithms present various levels of complexity and accuracy, they find a limitation in terms of availability of future trip information, which generally prevents exploitation of the full PHEV potential in real-life cycles. This paper presents a comprehensive analysis of EMS evolution toward blended mode (BM) and optimal control, providing a thorough survey of the latest progress in optimization-based algorithms. This is performed in the context of connected vehicles and highlights certain contributions that intelligent transportation systems (ITSs), traffic information, and cloud computing can provide to enhance PHEV energy management. The study is culminated with an analysis of future trends in terms of optimization algorithm development, optimization criteria, PHEV integration in the smart grid, and vehicles as part of the fleet.

Energy Management in Plug-in Hybrid Electric Vehicles: Recent Progress and a Connected Vehicles Perspective

Adaptive unscented Kalman filtering for state of charge estimation of a lithium-ion battery for electric vehicles

In conventional equalizers, the facts of bulky size and high cost are widespread. Particularly, the zero-switching loss and zero-voltage gap (ZVG) between cells are difficult to implement due to the high-frequency hard switching and the voltage drop across power devices. To overcome these difficulties, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed. The QRLCC is employed to gain zero-current switching, leading to a reduction of power losses. The BDDC is employed to enhance the equalization voltage gap for large balancing current and ZVG between cells. Moreover, through controlling the duty cycle of the BDDC, the topology can online adaptively regulate the equalization current according to the voltage difference, which not only effectively prevents overequalization but also abridges the overall balancing time. Instead of a dedicated equalizer for each cell, only one balancing converter is employed and shared by all cells, reducing the size and implementation cost. Simulation and experimental results show the proposed scheme exhibits outstanding balancing performance, and the energy conversion efficiency is higher than 98%. The validity of the proposed equalizer is further verified by a quantitative and systematic comparison with the existing active balancing methods.

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A Cell-to-Cell Battery Equalizer With Zero-Current Switching and Zero-Voltage Gap Based on Quasi-Resonant LC Converter and Boost Converter

This paper proposes an automatic any-cells-to-any-cells battery equalizer, which merges the forward and flyback converters through a common multiwinding transformer. The windings of the transformer are divided into two groups, which have opposite polarities. The principles of the proposed equalizer are that the equalization in one group is achieved based on forward conversion and the balancing between the two different groups is based on flyback conversion, by which the magnetic energy stored in the transformer can be automatically reset without using additional demagnetizing circuits. Moreover, only one MOSFET and one primary winding are required for each cell, resulting in smaller size and lower cost. One pair of complementary control signals is employed for all MOSFETs, and energy can be automatically and directly delivered from any high-voltage cells to any low-voltage cells without the requirement of cell monitoring circuits, thereby leading to a high balancing efficiency and speed. The proposed topology can achieve the global equalization for a long battery string through connecting the secondary sides of transformers without the need of additional components for the equalization among modules, which also overcomes the mismatching problem of multiple windings. The validity of the proposed equalizer is verified through experiments, and the balancing efficiency can reach up to 89.4% over a wide range of conditions.

An Automatic Equalizer Based on Forward–Flyback Converter for Series-Connected Battery Strings

The coordination between the powertrain and control strategy has significant impacts on the operating performance of hybrid electric vehicles (HEVs). A comprehensive methodology based on Particle Swarm Optimization (PSO) is presented in this paper to achieve parameter optimization for both the powertrain and the control strategy, with the aim of reducing fuel consumption, exhaust emissions, and manufacturing costs of the HEV. The original multi-objective optimization problem is converted into a single-objective problem with a goal-attainment method, and the principal parameters of powertrain and control strategy are set as the optimized variables by PSO, with the dynamic performance index of HEVs being defined as the constraint condition. Computer simulations were carried out, which showed that the PSO scheme gives preferable results in comparison to the ADVISOR method. Therefore, fuel consumption and exhaust emissions of HEVs can be effectively reduced without sacrificing dynamic performance of HEVs.

PSO algorithm-based parameter optimization for HEV powertrain and its control strategy

Due to the low cost, small size, and easy control, the switched-capacitor (SC) equalizer is promising among all types of active cell balancing methods. However, the balancing speed is generally slow and the balancing efficiency is seriously low when the SC equalizer is applied into a long battery string. Therefore, an automatic switched-coupling-capacitor equalizer (SCCE) is proposed, which can realize the any-cells-to-any-cells equalization for a battery string. Only two switches and one capacitor are required for each battery cell. All mosfet s are controlled by one pair of complementary pulse width modulation signals, and energy can be automatically and directly delivered from any higher voltage cells to any lower voltage ones without the need of cell monitoring circuits, leading to a high balancing efficiency and speed independent of the cell number and the initial cell voltages. Contrary to the conventional equalizers using additional components for the equalization among modules, the proposed equalizer shares a single converter for the equalization among cells and modules, resulting in smaller size and lower cost. A prototype for four lithium battery cells is implemented, and an experimental comparison between the proposed SCCE and the conventional SC equalizer is presented. Experimental results show the proposed topology exhibits a substantially improved balancing performance, and the measured peak efficiency is 92.7%.

A Switched-Coupling-Capacitor Equalizer for Series-Connected Battery Strings

Due to the adjacent cell-to-cell equalization, the classical switched-capacitor equalizer (SCE) has seriously low balancing speed and efficiency for a long battery string. Therefore, a series of star-structured switched-capacitor equalizers are proposed to achieve high balancing speed and efficiency independent of the cell number and the cell voltage distribution without significant influences on the size, cost, control, and reliability compared with the classical SCE. The proposed topologies use the least mosfet s and capacitors to achieve the most direct balancing paths between any two cells, being the optimal switched-capacitor structures. An analysis method for the slow switching limit and the fast switching limit impedances of the proposed equalizers is proposed to provide a theoretical guidance for the selection of the switching frequency. The inherent advantages of the proposed systems are the small size, low cost, simple control, high efficiency, fast speed, easy modularization, and high reliability. A prototype for four lithium-ion battery cells is set up. Experimental results show improved balancing performances with strong robustness. Moreover, the measured peak balancing efficiency is about 93.1% despite faster balancing speed.

Naxin Cui

Papers

A Cell-to-Cell Battery Equalizer With Zero-Current Switching and Zero-Voltage Gap Based on Quasi-Resonant LC Converter and Boost Converter

An Automatic Equalizer Based on Forward–Flyback Converter for Series-Connected Battery Strings

PSO algorithm-based parameter optimization for HEV powertrain and its control strategy

A Switched-Coupling-Capacitor Equalizer for Series-Connected Battery Strings

Analysis and Optimization of Star-Structured Switched-Capacitor Equalizers for Series-Connected Battery Strings