Road vehicles using electric power sources have become increasingly popular in the last decade. Meanwhile, battery technology is still not mature enough to meet expected vehicle range; thus the transition from ICE vehicle to fully electric vehicle is not imminent. Therefore the concept of hybrid drivetrain technology was introduced. The hybrid powertrain configuration includes at least two different energy converters together with an energy storage medium. In this article, different gear shifting algorithms were introduced to increase ICE efficiency in conventional vehicle. Besides, a parallel hybrid configuration was also introduced to enhance drivetrain efficiency. The Equivalent Energy Minimization Method (ECMS) and Dynamic Programming (DP) algorithms were selected as online and offline implementable optimal control methods for hybrid power sharing management. Totally six different case studies were planned to compare the efficiency of each configuration. Finally, the effect of the gear ratio selection and power split algorithms were compared on conventional and parallel hybrid drivetrains regarding overall efficiency.
This study investigates the electrical and thermal characteristics of a cylindrical lithium-ion cell with an axisymmetric two-dimensional lumped model. The cell is completely discharged at 0.5, 1 and 1.5 C rates under 0, 20 and 50 °C operating temperatures. Both the open circuit voltage values and the average specific heat value of the cell are measured and used as an input to the model. The model uses the variable internal resistance approach to evaluate the voltage variation of the cell that is obtained from experimental data. A cylindrical lithium-ion cell has a spiral construction that involves multiple layers. However, these layers are assumed as a uniform material in the lumped model. The lumped model in COMSOL Multiphysics couples the heat transfer and lumped battery interfaces so it allows predicting the surface temperature of the cell during discharging processes. The experimental results point out that the operating temperature inversely affects the internal resistance and the heat generation within the cell during a discharging process. Furthermore, it is found that the capacity of the cell significantly decreases at low operating temperatures. Finally, the predicted temperature profile follows the same trend with the experimental data and is consistent at each operating condition.
A TCSC is one of the FACTS devices that can provide fast-acting controls of power on the long ac transmission line over wide range. This paper investigates the effects of the TCSC on damping power system oscillations. In this study, TCSC is represented by its fundamental frequency impedance. For improving the system damping, a supplementary damping controller is considered. Finally, the simulation results of system dynamic performance response for system parameters variation is achieved and discussed.
The hybrid electric powertrain is a robust solution that allows for major improvements in both fuel economy and emission reduction. In the present study, a through-the-road hybrid vehicle model with an electric motor driving the rear axle and an Internal Combustion Engine (ICE) driving the front axle has been constructed. We then present a systematic method for the determination of a real time applicable optimal Energy Management Strategy (EMS) for a hybrid road vehicle. More precisely, we compare the performance of rule-based EMS strategies to an optimization-based strategy, namely ECMS (Equivalent Consumption Minimization Strategy). The comparison is conducted in parallel with a parameterization of the size of the internal combustion engine and the implementation of a Continuously Variable Transmission (CVT) that allows following the line of best fuel economy. For the FTP-75 driving cycle, the constrained engine On-off control algorithm is shown to offer a 28% improvement potential of fuel consumption compared to the conventional internal combustion engine while the ECMS strategy achieves an improved potential of nearly 33%.
Abstract Lithium-Ion batteries have become the principal battery technology for EVs to date. However, one of the principal factors limiting the widespread usage of the EVs is the length of charging times for the lithium-ion battery packs. The appropriate charging algorithm is critical to shorten the battery charging times while keeping the battery safe. In our earlier work, we proposed a novel optimal strategy for charging the lithium-ion battery based on electrochemical battery model using A performance index that aimed at achieving a faster charging rate while maintaining safe limits for various battery parameters. A more realistic model, based on battery electro-chemistry has been used for the design of the optimal charging algorithm as opposed to the conventional equivalent circuit models. Simulation results showed that the proposed optimal charging algorithm is capable of shortening the charging time of a lithium-ion cell by as much as 30% when compared with the standard constant current charging. Here we present the results from a number of experiments using Lithium-Ion cylindrical cells that were charged using the proposed algorithm and compared the charging times with the standard constant current-constant voltage (CC-CV) charging algorithms. A Maccor Series 4300 battery testing system was used to carry out the experiments. The experimental results showed that the proposed algorithm offered shorter charging times by up to 16% when compared to the CC-CV charging algorithms under the same battery initial conditions such as SOC and temperature of the cells.
Li-ion batteries, as a secondary battery type, are currently the most viable option for powering hybrid/electric vehicles. They have considerable advantages such as high specific energy and power, no memory effect, long cycling life, low maintenance requirement, and low self-discharge rate. However, their thermal performance can easily deteriorate at extreme ambient temperatures. Therefore, in this study, thermal and electrical behaviors of Li-ion batteries were investigated under various operating temperatures using a driving cycle that represents a highway driving condition. A battery testing system was used to determine the performance of Li-ion batteries under simulated loads. The results show that the measured temperature profiles, in broad strokes, follow the current profile. Because of the thermal capacitance of the battery, the changes in temperature variations are observed to be the smoothened out version of the current profile. Moreover, the results show that the extreme ambient temperatures have adverse effects on thermal performance of Li-ion batteries. The volumetric energy density and the capacity of the cell significantly decrease at cold ambient temperatures, especially for the sub-zero temperature applications possibly due to weak ionic conductivity within the cell. On the other hand, the difference between the ambient temperature and the surface of the cell becomes more pronounced as the ambient temperature decreases.
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