1,720,999 research outputs found
A lithium-ion capacitor model working on a wide temperature range
Full text linkEnergy storage systems are spreading both in stationary and transport applications. Among innovative storage devices, lithium ion capacitors (LiCs) are very interesting. They combine the advantages of both traditional electric double layer capacitors (EDLCs) and lithium ion batteries (LiBs). The behavior of this device is much more similar to ELDCs than to batteries. For this reason, several models developed for traditional ELDCs were extended to LiCs. Anyway, at low temperatures LiCs behavior is quite different from ELDCs and it is more similar to a LiB. Consequently, EDLC models works fine at room temperature but give worse results at low temperatures. This paper proposes a new electric model that, overcoming this issue, is a valid solution in a wide temperature range. Based on only five parameters, depending on polarization voltage and temperature, the proposed model is very simple to be implemented. Its accuracy is verified through experimental tests. From the reported results, it is also shown that, at very low temperatures, the dependence of the resistance from the current has to be taken into account
Decentralized PEV Control Based on a Subgradient Method for Mixed-Integer Programming Problems
No full textIn this paper, a subgradient method for solving mixed-integer linear programming problems is tailored and used to control in a distributed, and hence scalable way, the recharging process of a fleet of plug-in electric vehicles (PEVs). This makes possible to scale the problem to large PEV fleets, in a privacy-preserving fashion, something that cannot be done when relying on centralized optimization-based methods. A key challenge to face is given by the fact that the mathematical formulation of the PEV charging problem includes both real (i.e., continuous) and integer (in particular, Boolean) variables. This complicates significantly the mathematical theory, compared to the case in which all the involved variables are real. The PEV charging power is realistically modelled as a semi-continuous variable (while most of the works model it as a on/off variable), and the goal is to recharge the PEVs according to the user charging preferences, while letting the aggregated PEV power track a given power reference. Simulation results are discussed and possible directions for future research are outlined
Torque Allocation and Energy Management Strategy for a Multi-Motor Electric Vehicle
No full textThe 2023 edition of the IEEE VTS Motor Vehicles
Challenge proposed to develop energy and mechanical
management strategies for an electric vehicle (EV) equipped with
three motors and a hybrid energy system based on fuel cells and
batteries. The proposed strategy aimed to maximize the
performance of the EV by making it possible to work the hybrid
energy storage system, as much as possible, in its optimal
efficiency range and by adequately allocating the total required
torque among the three motors. The developed strategy achieved
second place at the 2023 edition of the IEEE VTS Motor Vehicles
Challeng
Improvement of EVs range by hybrid storage units
No full textNowadays, electric vehicles (EVs) are of great interest over the world. In the past, the diffusion of EVs was impeded because of the limits of energy storage units, which reflect in vehicle range limited extension. In recent years, a significant progress was made in terms of power and energy density thanks to the lithium based batteries that can guarantee vehicle ranges higher than 100 km. Another further step can be done by coupling more than one storage technology and leading to an increased efficiency and extension of the vehicle range. In this paper, the effectiveness of adding another storage unit to a lithium ion battery is investigated for different EVs and driving cycles. Furthermore, a methodology procedure, based on the knowledge of the test driving cycle, and parameters of the EV, is proposed to find the optimal size of the auxiliary storage, that maximizes the EV range
Lithium Ion Battery Models and Parameter Identification Techniques
Full text linkNowadays, battery storage systems are very important in both stationary and mobile applications. In particular, lithium ion batteries are a good and promising solution because of their high power and energy densities. The modeling of these devices is very crucial to correctly predict their state of charge (SoC) and state of health (SoH). The literature shows that numerous battery models and parameters estimation techniques have been developed and proposed. Moreover, surveys on their electric, thermal, and aging modeling are also reported. This paper presents a more complete overview of the different proposed battery models and estimation techniques. In particular, a method for classifying the proposed models based on their approaches is proposed. For this classification, the models are divided in three categories: mathematical models, physical models, and circuit models
Swept area theory: An approach in nonlinear and switched network analysis
No full textIn this work, according to the concept of area' on the v-i plane, a new approach called swept area theory, under both nonlinear continuous and discontinuous conditions, is developed. Novel conservative functions, such as area velocity and closed area over time (CAT), involved in this theory, are proposed. An analysis is carried out, by means of these functions, over nonlinear R, L, and C elements and over the ideal switch. In addition, jump discontinuities are discussed in detail. The CAT is related to the harmonic reactive powers and under sinusoidal steady state becomes proportional to the classical reactive power. A balance rule concerning harmonic reactive powers over nonlinear resistor under continuous conditions is obtained and discussed as a novel interesting result. This aspect impacts on a possible expanded definition of reactive power under distorted conditions. Thanks to the switching power, a novel quantitative relation between hard-switching commutations and CAT is obtained, with both theoretical and applicative relevance. More explanation is presented through a demonstration that shows how an ideal switch and power converters can become sources of reactive power. Issues of principle regarding the ideal switch model with respect to the real one are another important result of this work
Temperature Effect on the Open Circuit Voltage of Lithium-Ion Battery
No full textNowadays, lithium-ion battery technology is widely employed in a lot of applications. The state of charge (SOC) is one of the most crucial parameters to be estimated since it ensures working in a safe range and identify the available energy. Several methods for SOC estimation rely on the knowledge of the open circuit voltage (OCV) curve. The latter is highly dependent on the battery temperature, so for a proper SOC estimation, it is important to know and model how the OCV changes with temperature. In the literature, the effect of temperature on the OCV is mostly considered through lookup tables, and correcting factors applied to the OCV curve at a reference temperature. On the other hand, the variation law of the OCV curve as a function of the battery temperature is not well characterized. In this work, based on an experimental campaign, the dependency on temperature was analyzed. Finally, a model was developed and validated
Real Time State of Charge Estimation of Lithium-Ion Battery Considering Temperature
No full textThis study introduces and validates a real-time state of charge (SOC) estimation method for lithium-ion batteries (LiBs), which considers the impact of temperature. The SOC estimation is based on a simple first-order Thevenin electric circuit model. First, the proposed algorithm estimates the parameters of this model while implementing a simple analytical function that models the relationship between the open circuit voltage (OCV) and the absolute state of discharge, q, of the LiB, considering temperature effects. Through the measured current, voltage, and temperature of the battery, the OCV is thus estimated. By inversely applying the proposed OCV-q relationship, the actual absolute state of discharge and battery capacity can be estimated. Finally, the SOC is assessed through this estimation. The validation process involves emulating an LiB for an electric vehicle application using a comprehensive electric battery model coupled with a simple thermal circuit model
Evaluation of Dual-Chemistry Battery Storage System for Electric Vehicles Charging Stations
No full textThe use of stationary batteries in electric vehicle
fast-charging stations is a well-known solution to alleviate stress
on the grid. However, the rapid variations in charging demand
pose a challenge to battery lifetime due to cycle aging. In this
framework, the paper aims to evaluate the adoption of two
different battery chemistries within the same storage system to
cope with different demand dynamics (fast and slow power
variations). The comparison is done by finding the optimal sizing
for both the single and hybrid chemistry solutions and comparing
their costs
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