Two-stage Charging Research Articles

Revealing the Two-Stage Charging Process in Sulfuric Acid Electrolyte by Molecular Dynamics Simulation.

Two-dimensional MXene materials perform excellently in supercapacitor applications, but self-stacking and overlap limit their applications. Constructing a reasonable layered structure by combining MXene and graphene can effectively inhibit the restacking and overlap of MXene and improve the performance of supercapacitors. In this work, we studied the energy storage performance of a conventional MXene electrode and MXene/graphene composite electrode in sulfuric acid aqueous electrolyte by molecular dynamics (MD) simulation and analyzed their energy storage mechanisms. The simulation results reveal that the MXene/graphene composite electrode showed faster charge-discharge speed and larger capacity and had more obvious advantages as a cathode. The charging process of the composite cathode can be divided into two stages. In the first stage, SO42- and H3O+ enter the electrode as a whole in a nearly 1:2 ratio, and a unique three-layer structure is formed in the graphene area, while a large number of HSO4- leaves the electrode. In the second stage, SO42- with a part of H3O+ (ratio of 2:2 to 2:3) leave the electrode, and the three-layer structure is gradually destroyed. The cooperation of these two stages leads to a particular "concave" in the total energy change of the composite cathode. The introduction of graphene has brought about changes in ion distribution, migration mechanism, and energy change, making the MXene/graphene cathode show significant advantages in energy storage. This work is of great significance for understanding the microscopic energy storage mechanism of MXene/graphene-based electrodes.

Research on two-stage on-board charging system based on IPOP LLC resonant converter

Research on two-stage on-board charging system based on IPOP LLC resonant converter

Research on two-stage on-board charging system based on IPOP LLC resonant converter

Research on two-stage on-board charging system based on IPOP LLC resonant converter

Smart and efficient EV charging navigation scheme in vehicular edge computing networks

With the increasing number of electric fast charging stations (FCSs) deployed along roadsides of both urban roads and highways, the long-distance travel of electric vehicles (EVs) becomes possible. The EV charging navigation scheme is significant for the quality of user experience. However, the variable conditions of both power grid and traffic networks make it a serious challenge. In this paper, we propose an efficient EV charging navigation scheme while considering both the electric and computation resource sharing. With the support of vehicular edge computing networks in intelligent transportation systems (ITSs), EVs perform both the flexible power load and edge computing nodes. When the traffic network in the established route starts to become congested, EVs can select to enter the nearest FCS. In addition to being supplemented by electric resources, EVs also benefit by sharing their own computing resource with FCSs. We formulate the EV charging navigation as a mixed integer programming problem, the EV moving route planning, FCS selection, and staying time in FCSs are optimized, to balance the relationships among the traveling time, traveling cost and reward. To address the influence caused by the randomness of traffic conditions and charging prices, a two-stage charging navigation algorithm combined with A∗\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A^{*}$$\\end{document} algorithm and deep reinforcement learning (DRL) is proposed, with a novel designed reward function. Eventually, numerous experimental results show the effectiveness of the proposed schemes.

ELECTRIC VEHICLE ONBOARD CHARGING VIA HARRIS HAWKS OPTIMIZATION-BASED FRACTIONAL-ORDER SLIDING MODE CONTROLLER

Electric vehicles (EVs) have become more popular due to their excellent efficiency and pollution-free benefits. The technology requirements for onboard chargers are increasing as the number of electric vehicles increases. This research proposes a fractional-order sliding mode controller (FOSMC) for power converters to improve the efficiency of the onboard battery charger. The Harris Hawks optimization (HHO) algorithm chooses the FOSMC parameters. Independent controllers are used in a two-stage charging scheme. The grid-side ac–dc converter helps to smooth the current and voltage in the dc bus while reducing the harmonic frequency in the grid. A dc-dc converter with a constant current–constant voltage curve regulates the charging parameters of the battery on the battery side. Experiments show that HHO-based FOSMC improves the overall dynamic response of the onboard battery charger. Moreover, the proposed method performs with a current total harmonic distortion (THD) of less than 2 %. The proposed method improves 98% efficiency than existing methods such as SSA-PID and SSA- FOAFPIDF controllers.

A Bidirectional Five-Level Buck PFC Rectifier With Wide Output Range for EV Charging Application

AC-to-DC conversion is integral to the two-stage charging interface of electric vehicle (EV) batteries. For such chargers, the use of multilevel rectifiers (MLRs) reduces voltage ratings of power switches, while achieving a high-quality input voltage waveform. Balancing of capacitors in MLRs, however, is an important challenge. In this work, a power factor correction (PFC) five-level rectifier with self-balanced switched capacitors is proposed. Each leg of the presented topology comprises five power switches and one switched capacitor, where the voltage ratings of power switches are equal to the output dc voltage. It does not require an additional filter capacitor on the dc side, as the load appears in parallel always with a switched capacitor of one of the legs. The five-level operation with continuous conduction leads to the elimination of the capacitive filter on the ac-side and inductive filter on the dc-side. This article presents the operating principle, modulation strategy, closed-loop control, and design aspects of the proposed rectifier. The proposed topology is validated through experimental results and a comparison is made with other topologies. Following three features of the proposed topology make it suitable for EV battery charging applications—buck operation with a wide output regulation, the possibility of bidirectional flow of power needed for vehicle-to-grid systems, and easy realization of its three-phase version by simply adding one more leg. These features too have been demonstrated with experimental results.

Power Scheduling Scheme for a Charging Facility Considering the Satisfaction of Electric Vehicle Users

This paper proposes a novel user-preference-aware power scheduling scheme for application at an electric vehicle (EV) charging facility. Here, the preference of the EV user is characterized as a utility function by considering two different factors: 1) a satisfaction factor according to the charged energy, and 2) payment for the received charging service. As a key component of the power scheduling method, this paper proposes a two-stage power charging method and analyzes the advantage of the proposed method from a monetary perspective. In addition, this paper analyzes the economic benefits of a charging facility and EVs using the single-leader, multi-follower Stackelkberg game. By showing the existence of a unique best response for each participant, this paper presents the improvement of financial profit of EV users and charging facility through comparison with the case where the charging facility does not apply a proper power management scheme. Based on the actual world datasets, this paper shows that the proposed power scheduling scheme is feasible for actual environment. With satisfying the constraints, it is possible to reduce overall electricity cost up to 8.59% compared to the case without considering the peak power in EV charging facility.

Joint Mobile Charging and Coverage-Time Extension for Unmanned Aerial Vehicles

In modern networks, the use of drones as mobile base stations (MBSs) has been discussed for coverage flexibility. However, the realization of drone-based networks raises several issues. One of critical issues is drones are extremely power-hungry. To overcome this, we need to characterize a new type of drones, so-called charging drones, which can deliver energy to MBS drones. Motivated by the fact that the charging drones also need to be charged, we deploy ground-mounted charging towers for delivering energy to the charging drones. We introduce a new energy-efficiency maximization problem, which is partitioned into two independently separable tasks. More specifically, as our first optimization task, two-stage charging matching is proposed due to the inherent nature of our network model, where the first matching aims to schedule between charging towers and charging drones while the second matching solves the scheduling between charging drones and MBS drones. We analyze how to convert the formulation containing non-convex terms to another one only with convex terms. As our second optimization task, each MBS drone conducts energy-aware time-average transmit power allocation minimization subject to stability via Lyapunov optimization. Our solutions enable the MBS drones to extend their lifetimes; in turn, network coverage-time can be extended.

A Novel Design Method of LCC-S Compensated Inductive Power Transfer System Combining Constant Current and Constant Voltage Mode via Frequency Switching

Inductive power transfer (IPT) is an attractive wireless power charging option in many applications such as electric vehicle biomedical devices and consumer electronics, etc. Constant current and constant voltage (CC-CV) charging profile is widely used for charging applications due to affecting the life and the reliability of the Li-ion battery. However, the IPT systems that can achieve both CC and CV modes with soft switching are not well studied. This paper presents an inductive power transfer system for wireless charging without a back-end converter, which achieves the required two-stage charging profile with high efficiency by keeping inverters’ soft switching operation. The characteristics of an LCC-S compensation topology have been investigated thoroughly. Two fixed resonant frequencies, whose analytical expressions have been derived, can be found to realize constant current output and constant voltage output respectively under zero-phase angle condition. Besides, an effective tuning method has been presented for zero voltage switching realization to reduce the switching loss. Moreover, a parameter design procedure has been summarized for the wireless charger with a simplified structure and high efficiency. Finally, the method is validated through experiments on a 3.5kW prototype realizing constant current and constant voltage outputs with a peak efficiency of 97.3%.

Forecasting of a boosted locomotive gas diesel engine parameters with one- and two-stage charging systems

Conversion of locomotive engines for operation on natural gas lowers considerably expenses for fuel and reduces exhaust emissions which makes it possible to omit large and expensive aftertreatment systems. The permanent need to raise the engine power requires a considerable increase of the boost pressure. This can be realized by using a high pressure turbocharger or a two-stage charging system. In the research, parameters of a high boosted D200 6-cylinder locomotive engine having D/S=200/280 mm are forecasted using a one-zone model developed in MADI. An analysis was carried out to explain why the 1st stage compressor of the two-stage charging system should be specially profiled to have its map tilted to the right. Calculations were performed for the gas diesel engine having a break mean effective pressure (BMEP) 2.7 MPa with one and two-stage charging systems. In both cases, close fuel efficiency was obtained, though for the two-stage charging system, the boost air pressure was higher. The engine with one turbocharger had no reserves for further power augmentation while the two-stage charging system enabled to increase the boost air pressure further. Therefore, parameters of the engine having a higher BMEP 3.2 MPa were calculated. In that case, not to exceed the peak combustion pressure, a retarded fuel injection was used which resulted in fuel efficiency drop by approximately 1.5%.

A two stage battery charger for EV charging applications

<p><span>Electric power generation and consumption are indicating an unprecedented change in recent decades. Electrical power industry and transportation sector lie at the core of this development and hence this change. This change is one of the major causes of polluting environmental and global warming. </span><span>So, to decrease the dependency on conventional fuels and greenhouse gas emissions, countries around the globe are actively finding alternative energy resources. It will help to develop clean and green energies to build a sustainable society. Simultaneously, energy utilization in the field of transportation is witnessing a change from fossil fuel to electricity-based fuel. Electrified transportation system is a solution to endorse sustainable energy development and addressing environmental pollution, global warming issues. In this paper, an EV battery charger is designed with a two-stage charging model to achieve good efficiency. The design is simulated by using MATLAB simulation and compared with the existing model. The simulation results show that the proposed model is superior to the traditional model.</span></p>

Thermal–Electrochemical simulation of electrochemical characteristics and temperature difference for a battery module under two-stage fast charging

Abstract The electrochemical characteristics and temperature difference are crucial for a battery module, but they are seldom taken into account in the previous works of multistage fast charging focusing on reducing charging time and temperature rise for a single battery. A multilayer electrochemical-thermal coupled model incorporating parallel connected cells inside each battery is developed for a serially connected battery module using two-stage fast charging patterns with different charging current rates (C-rates) in two charging stages to study the electrochemical characteristics, temperature difference and state of balance. Results show that the shift of C-rate causes a sudden change in the magnitude and spatial distribution of local current density, and in the magnitude of solid phase Li+ concentration gradient and electrolyte Li+ concentration. The non-uniformity of electrochemical performance inside a battery generally is more significant when the C-rate of the first stage is higher than that of the second stage. The charging pattern with lower C-rate in the first stage has potential in reducing the maximum local temperature difference in a battery while increasing the maximum temperature difference of module. The increase and decrease of the C-rate in the second stage easily aggravates the state of balance at the end of charging and leads to a sudden fluctuation of state of balance in the shift of C-rate, respectively. The charging strategy should be optimized with the consideration of electrochemical performance, cooling intensity, coolant temperature, battery initial temperature and state of balance.

Study on the start‐up and fault‐restart strategies and reactive power analysis of DC distribution systems

The DC distribution network is becoming the basic supporting component of the urban distribution network. A variety of power supplies, loads, and energy storage devices can be directly integrated into a DC distribution network, which can improve the economical and energy efficiency of the power system. This study proposes two charging strategies, two-stage charging and one-by-one charging, to make the converter start up safely or quickly return to the normal operation state after the fault clearance. Owing to the existence of numerous DC capacitors in voltage source converters, the reactive power consumption in the start-up process needs to be explicitly calculated. Mathematical expressions of reactive power requirements for different charging strategies are investigated in detail, from where it can be seen that the current-limiting resistance can significantly affect the reactive power and the entire charging time. Simulation results show that the AC voltage can be seriously affected by the oscillation of the reactive power, which will lead to voltage drop and waveform distortion in mode switching.

Two-stage fast charging method using dual-switch flyback converter

To improve the charging speed, a new two-stage charging method with dual-switch fly-back converter for Li-ion battery is proposed in this paper. The proposed charging method adopts a two-stage charging of constant current and adaptive pulse current (CC-APC) charging to reduce the charging time for batteries. A dual-switch fly-back converter has the features of simple topology, low cost, galvanic isolation, low voltage stress, no need of additional RCD clamp, and the leakage inductance energy is recovered to the input voltage when the switch is off. Based on the above advantages, a dual-switch fly-back converter is used and designed for the charging system. With the proposed charging method, the charging time is reduced by about 34% compared with the traditional constant current-constant voltage charging method, and the charging time is reduced by about 6% compared with the constant current-fixed duty cycle pulse charging method. The simulation results are provided to verify the system performance.

Modeling the effect of two-stage fast charging protocol on thermal behavior and charging energy efficiency of lithium-ion batteries

Abstract To enable fast charging of lithium ion batteries, extensive attention is needed to reduce the heat generation rate to avoid thermal runaway. This work studies the impact of the fast charging protocol on thermal behavior and energy efficiency of a lithium ion battery cell for 30-minute charging with 80% rated capacity. A two-stage constant current (2SCC) charging protocol with different current level combinations is adopted to mitigate the temperature rise leading to thermal runaway and improve the charging energy efficiency, because different charging current will generate different rates of heat. An electrochemical thermal coupled model is developed to predict the heat generation rate, charging energy rate, and temperature rise with experimental validation. The simulation results indicate that the “high-low” charging protocols of the 2SCC fast charge can achieve a lower overall temperature rise and higher charging energy efficiency than both the “low-high” charging protocols and the standard one-stage constant current (1SCC) charging. Compared to the 1SCC charge, the 2SCC charging protocol can improve the overall charging energy efficiency by 1%. Additionally, the impact of the 2SCC charging protocol on the thermal behavior under different initial cell temperatures and the heat transfer coefficients are discussed.

Two-Stage Optimal Scheduling of Electric Vehicle Charging Based on Transactive Control

In this paper, a two-stage optimal charging scheme based on transactive control is proposed for the aggregator to manage day-ahead electricity procurement and real-time electric vehicles (EV) charging management in order to minimize its total operating cost. The day-ahead electricity procurement considers both the day-ahead energy cost and expected real-time operation cost. In the real-time charging management, the cost of employing the charging flexibility from the EV owners is explicitly modeled. The aggregator uses a transactive market to manage the real-time charging demand to provide the regulating power. A model predictive control-based method is proposed for the aggregator to clear the transactive market. The real-time charging decisions of the EVs are determined by the clearing of the proposed transactive market according to the real-time requests and preferences of the EV owners. As such, the aggregators decisions in the real-time EV charging management and regulating power markets can be optimized. At the same time, the charging requirements and response preferences of the EV owners are respected. Case studies using real world driving data from the Danish National Travel Surveys were conducted to verify the proposed framework.

Two-stage charging strategy of plug-in electric vehicles based on fuzzy control

This paper proposes a two-stage charging strategy for solving charging control issues of plug-in electric vehicle (PEV). At the first stage, the optimal charging of each PEV is calculated with Bee Algorithm (BA) as an aggregator optimizer. At the second stage, this aggregated power is then distributed among electrical vehicles (EVs) using fuzzy logic controller (FLC). This framework has considered non-linear dynamic feature of PEV batteries in various practical scenarios. Main advantageous of this method are reducing load peak, smoothing transformers load profile, consideration of non-linear dynamic behavior of PEV batteries and proper energy management of batteries in case of unscheduled unplugging of PEVs from charging stations. Finally, simulation results are presented to verify the analysis of the proposed charging control strategy.

Dead-beat instantaneous power control for off-board charger of electric vehicle for V2G application

Dead-beat instantaneous power control strategy for electric vehicle off-board V2G charger is presented in this paper, to suppress harmonic pollution to power grid and realize bi-directional flow of electric energy. The charger consists of three-phase voltage source PWM grid-side converter and bi-directional dc/dc converter. A double closed-loop for three-phase voltage source PWM grid-side converter is designed firstly. And the outer voltage loop is used to keep dc bus voltage constant. The expected switching voltage components are achieved by substituting predicted instantaneous power with its instruction value, to form the inner dead-beat instantaneous power loop. Then a voltage–current double closed-loop for bi-directional dc/dc converter is proposed to implement two-stage charging, combining with constant-current charging and constant-voltage charging. Finally, the effectiveness and feasibility of the proposed control strategy are verified on the power-hardware-in-loop-simulation platform.

Charging Distributed Sensor Nodes Exploiting Clustering and Energy Trading

One of the main issues on wireless sensor networks is the sustainability of network operation. Sensor nodes typically acquire their energy from batteries. However, they are often deployed in hard-to-reach places, so replacing their batteries incurs substantial increase in operational cost. Therefore, energy harvesting by sensor nodes can be more cost-efficient for sustainable network operation. The harvested energy should be transmitted from a single or multiple chargers. This paper deals with a charging scheme for distributed sensors nodes. The charging scheme consists of two stages: charging by a mobile charger and charging undercharged sensor nodes by overcharged ones. The second stage is considered energy trading between seller nodes and buyer nodes. For charging in the first stage, all the sensor nodes are classified into clusters. To this end, the concept of inclusion circle is devised. By the clustering based on the inclusion circle, a sensor node, which is located around the center of grouped sensor nodes is highly likely selected as a cluster head. Charging path of the mobile charger in the first stage is determined according to the locations of cluster heads. The energy trading in the second stage is to achieve energy balancing of the sensor nodes. When the proposed two-stage charging is finished, every sensor node is charged over the target level. The proposed scheme is compared with the existing charging schemes. As a result, the total amount of charging energy and the total charging time can be significantly reduced.

Profit maximization with customer satisfaction control for electric vehicle charging in smart grids

As the market of electric vehicles is gaining popularity, large-scale commercialized or privately-operated charging stations are expected to play a key role as a technology enabler. In this paper, we study the problem of charging electric vehicles at stations with limited charging machines and power resources. The purpose of this study is to develop a novel profit maximization framework for station operation in both offline and online charging scenarios, under certain customer satisfaction constraints. The main goal is to maximize the profit obtained by the station owner and provide a satisfactory charging service to the customers. The framework includes not only the vehicle scheduling and charging power control, but also the managing of user satisfaction factors, which are defined as the percentages of finished charging targets. The profit maximization problem is proved to be NPcomplete in both scenarios (NP refers to “nondeterministic polynomial time”), for which two-stage charging strategies are proposed to obtain efficient suboptimal solutions. Competitive analysis is also provided to analyze the performance of the proposed online two-stage charging algorithm against the offline counterpart under non-congested and congested charging scenarios. Finally, the simulation results show that the proposed two-stage charging strategies achieve performance close to that with exhaustive search. Also, the proposed algorithms provide remarkable performance gains compared to the other conventional charging strategies with respect to not only the unified profit, but also other practical interests, such as the computational time, the user satisfaction factor, the power consumption, and the competitive ratio.