Low latency/delay is one of the most critical requirements for the application of vehicular networks. However, frequent real-time information update caused by vehicles» high mobility is liable to aggravate the delay. Meanwhile, the task migration between different vehicular edge computing (VEC) servers results in an amount of delay if the computing cannot be completed before the vehicle moves out of the coverage of the current VEC server. In this paper, the problem is concluded as when and to whom to offload the task for VEC, which is formulated as a finite horizon Markov decision process (MDP) to minimize the delay with respect to the communication, computing, handover and migration. Through characterizing the time-space correlation of vehicle's mobility, the curse of dimensionality problem in MDP is resolved. Meanwhile, a general expression of the transition probabilities is derived. On this basis, the specific results of highway, 2-D street and real-data scenarios are provided as well. For practical implementation considerations, the transition probabilities are commonly uncertain primarily due to random driver behavior, inaccurate sample data and complex path environment. Under this uncertain environment, a robust time-aware MDP-based task offloading algorithm (RTMDP) is proposed, which has been proved to perform well even under the high uncertain transition probabilities by simulation results.

The characteristics of inductive power-transfer (IPT) systems are sensitive to the variation of the coupling coefficient caused by misalignment conditions or different gaps. This results in a reduction in transferred power and efficiency. The output characteristics considering frequency modulation applied in series–series (SS), inductor–capacitor–capacitor (LCC)-S and LCC–LCC compensated IPT systems have been explored, revealing that high-order compensation topologies hold limited power regulation ability if coupling varies significantly. The parameter sensitivity of LCC–LCC-compensated topology is investigated through the singular values (SVs) analysis. It is found that the variation of the parallel-compensated capacitors has the greatest impact on the output power. Aiming at alleviating the power drop caused by the coupling variation, a parameter offline tuning method realized by switching the parallel-compensated capacitance for a detuned LCC–LCC resonant converter is proposed for electric vehicle (EV) wireless charging. Analytical expressions have been derived in aiding the design of modified value of capacitance ensuring primary zero voltage switching (ZVS) operation. Thus, the detuned parameter combinations, which deliver rated power even with the worst coupling, are obtained. Finally, a 6.6-kw prototype has been built to verify the validity of the proposed topology, which can deliver 6.1 kW with an efficiency of 94% even when the coupling drops from 0.3 to 0.15.

In this article, an efficiency-oriented control strategy is proposed for LCC–LCC-compensated wireless power transfer (WPT) system to achieve zero-voltage-switching (ZVS) operation over a wide current regulation range, in which full-bridge (FB) and half-bridge (HB) modes are combined and switchable based on requirements from load. The harmonic-considered time-domain models for FB and HB modes are first built to calculate current through the switches at the turn- off moment accurately. Then, focused on the constant voltage charge stage with variable output current, the ZVS boundaries are identified in HB and FB modes as the preferable control trajectories, which determines the desired current output with joint considerations of frequency, phase-shift angle, and duty ratio. Next, a least squares optimization method is introduced to fit the theoretical control trajectories into a smooth curve that is practical for implementation on microcontrollers. Finally, a 4.4-kW WPT prototype is built to verify the feasibility and validity of the proposed control strategy. Results show that a high system efficiency can be achieved over a wide output current range, with an efficiency of 94.68% even at 20% rated power.

Thermal runaway of an electric vehicle (EV) battery can cause severe loss of property and human life. With the increasing market share of EVs, this issue becomes more critical since one single cell short circuit could easily cause thermal runaway in a few minutes. Therefore, battery short-circuit detection systems are important for the prevention and limitation of EV fire incidents. This article proposes a short-circuit detection and isolation method for lithium-ion battery packs based on relative entropy and the Z-score method, which identifies the cell voltage dropping behaviors caused by a short circuit with the sliding window processing method. Taking the optimal sliding window width, the proposed detection algorithm can be performed in real time without any significant delay. The effectiveness and efficiency of the proposed method are verified using real-world data measured from EVs that experienced fire incidents caused by thermal runaways. Results indicate the method in this article is capable to recognize the data pattern of the potential threat in real time and send an early alarm to the driver.

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%.