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This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [ABSTRACT FROM PUBLISHER]

On account of complementary control, reduced size, and energy saving, the switched-capacitor (SC) based equalizer becomes promising for the energy management of energy storage system. Traditionally, the number of the bypass capacitor in the SC based equalizer equals to the number of the battery module in series or parallel connections. The amount of bypass capacitors is enormous, thus costly and bulky for electric vehicles (EVs). In this paper, the integrated energy storage is proposed to reduce cost and save space, meanwhile, the equalizations between the batteries and the ultracapacitors (UCs) are achieved by the reutilization of SC network. UCs not only perform as energy storage units, but also work as energy exchange units. Thus, the number of balanced elements can be reduced significantly. The operational principles of the storage system and the analyses of the balancing process are examined in detail. The system simulation is performed for functionality evaluations. Meanwhile, an experimental prototype is also implemented for six cells to demonstrate the balancing process. The accordance of experiment and simulation can further testify the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

Some electrified vehicles, for example the Toyota Prius, integrate a dc–dc converter between the battery pack and the traction inverter to increase the powertrain efficiency. However, adding this extra converter adversely affects the cost and power density of the powertrain due to the additional components, such as the switches and the inductor, that are expensive and heavy in high-power converters. The concept of the multi-source inverter was previously introduced as an alternative solution to reduce the power rating of the dc–dc converter while keeping similar powertrain performance. In this paper, the implementation of the multi-source inverter in a hybrid power-split powertrain is discussed. The operating modes during both dc–ac and ac–dc conversions are detailed and a prototype is experimentally tested with a load. New control strategies of the proposed powertrain show that three out of five operating modes bring new opportunities in terms of battery charging and power rating reduction of the dc–dc converter. A vehicle-level simulation model is developed in MATLAB/Simulink to quantify the benefits of the proposed topology. Simulations are performed for four drive cycles to compare the power profile of the dc–dc converter of the suggested powertrain with the Toyota Prius. The average power transferred by the dc–dc converter can be reduced by up to 25 $\%$ in most drive cycles tested. [ABSTRACT FROM AUTHOR]

With the growing popularization of Electric Vehicle (EVs), Electro-mobility (in terms of where to charge EV) has become an increasingly important research problem in smart cities. One of the major concerns is the anxiety of EVs, as drivers may suffer from discomfort due to long charging time. In this paper, we leverage the battery switch technology to provide an even faster charging than plug-in charging service, by cycling switchable (fully recharged) batteries at Charging Stations (CSs). Upon that, a cost-efficient Publish/Subscribe (P/S) system is provisioned, to facilitate the design of distributed charging manner for privacy guarantee. The proposed communication framework utilizes Mobile Edge Computing (MEC)-functioned Road Side Units (RSUs) to bridge, process, and aggregate the information flow between CSs and EVs. We further design an advanced reservation-based charging system, in which the knowledge of EVs' reservations is utilized to predict how likely a CS will be congested. This benefits to a smart transportation planning on where to charge, in order to improve charging comfort. Results show the advantage of our enabling technology comparing to other benchmark solutions, in terms of minimized waiting time for the battery switch (as the benefit for EV drivers), and a higher number of batteries switched (as the benefit for CSs). [ABSTRACT FROM AUTHOR]

In this paper, we compare the performance of time-switching relaying (TSR) and power-splitting relaying (PSR) protocols in two-hop networks with a battery-assisted energy-harvesting (EH) amplify-and-forward relay. In this battery-assisted relay framework, the EH relay augments the harvested energy with energy drawn from a battery. Using expressions derived for throughput and average battery energy consumption, we investigate maximization of throughput for given battery energy availability per time slot and minimization of battery energy consumption for target throughput requirement. When only statistical channel knowledge is available, PSR results in better throughput performance at practical signal-to-noise ratios. However, in the typical low battery energy and low target throughput regime, it is TSR that is more battery energy efficient. When second-hop instantaneous channel knowledge is available, we observe dramatical energy savings that increases lifetime of nodes. Simulation results are presented to demonstrate accuracy of the derived expressions. [ABSTRACT FROM AUTHOR]

To overcome the problem that the balancing performance of existing switched-capacitor (SC) cell balancing systems drops along with the increase in the number of series-connected battery cells, a novel SC cell balancing circuit is presented in this paper. The same as other SC balancing systems, only a pair of complementary square-wave signals is required to control the proposed circuit. With resonant SC design, all switches employed in the proposed balancing circuit operate under zero-current switching. The equivalent model is derived to reveal the balancing performance of the proposed balancing circuit. The system feasibility and theoretical analysis are verified by both of simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved equalization architecture for series-connected lithium-ion battery strings, which can deliver energy from a battery module to the cells in the next adjacent battery module, resulting in an enhancement of the equalization current and efficiency. Particularly, the global equalization is achieved without the need of additional stage circuits to balance among modules, leading to a small size and low cost. A two-module equalizer based on resonant LC converter and buck converter with soft switching is implemented to verify the validity of the proposed interleaved architecture. Furthermore, a self-learning fuzzy logic control (SLFLC) algorithm is employed to online regulate the equalization period based on the voltage difference among cells and the cell voltage, not only greatly abbreviating the balancing time but also effectively preventing overequalization. The SLFLC has the outstanding advantages of high balancing precision, easy implementation, and strong robustness. Experimental results demonstrate that the proposed equalizer has good balancing performances with soft switching and high efficiency, and achieves zero-voltage gap among cells. Moreover, the proposed SLFLC algorithm abridges the total equalization time by about 27%, and reduces the equalization cycles by about 59% compared with the traditional control algorithm. [ABSTRACT FROM AUTHOR]

In the pursuit of fuel economy improvement and emission reduction, a trajectory optimization-based engine multioperating-point control strategy is proposed in this paper for the auxiliary power unit (APU) in an extended range electric vehicle. This strategy design deeply considers the transient process of the operating point switching that somehow influences the engine fuel economy and emission, and was often ignored. First, a combined cost MAP fully integrating several indices, including fuel consumption rate, CO, HC, and NOx emissions, is presented to synthetically evaluate the effect of the operation trajectory. Then an improved genetic algorithm, in terms of computational load reduction and convergence improvement, is employed to optimize the engine trajectory in the transient operating point switching process of the APU system, so that it is able to perform with the best fuel consumption and emissions. Finally, simulated and experimental results indicate that the proposed control strategy has obvious improvements in fuel economy and emissions, compared with conventional ones. [ABSTRACT FROM AUTHOR]

A nonisolated single-stage on-board charger for electric vehicles has been proposed to increase system efficiency and power density in previous works. However, its ability to achieve high efficiency is limited by variations in the electric utility and battery, especially during the step-down operation. This paper proposes an advanced control algorithm that improves system efficiency in the step-down mode by controlling each switch asymmetrically using a phase-shift control. The proposed algorithm consists of only one controller, which prevents transient states from causing variations in the controller. The algorithm decreases the magnitude and ripple of the inductor current, which improves the charging efficiency by approximately 4.1% over at the 3.7-kW full load that of the conventional algorithm in the step-down mode, and measured total harmonic distortion and power factor are 3.2% and 0.995, respectively. [ABSTRACT FROM AUTHOR]

Due to an increasing in-vehicle electric load demand, a new 48-V electric system architecture proposed by German premier car manufacturers has been gaining increasing attention recently for electrified vehicles. In this paper, a multiple-voltage bus converter for the 48-V and existing 12-V dual supply system, providing additional flexible dc bus voltages, is proposed. The proposed converter can provide a dual flexible dc voltage bus and an additional dependent voltage bus while simultaneously managing the 12-V supply net using only one single-leg switch pole and a diode. The additional dc voltage buses will provide more options to accommodate variable electric load components in a vehicle, improving their power density. Due to the multiple control objectives, the single-leg pole requires a multimode switching strategy to regulate the additional bus voltages. To improve the onboard vehicle system reliability and performance, an impedance network structure is implemented in the converter to obtain a dead-time-free pulsewidth modulation (PWM). Simulation and experimental results are presented to verify the feasibility and effectiveness of the proposed structure and control method. [ABSTRACT FROM PUBLISHER]

To process the power in hybrid energy systems using a reduced part count, researchers have proposed several multiinput dc–dc power converter topologies to transfer power from different input voltage sources to the output. This paper proposes a novel bidirectional nonisolated multi-input converter (MIC) topology for hybrid systems to be used in electric vehicles composed of energy storage systems (ESSs) with different electrical characteristics. The proposed converter has the ability to control the power of ESSs by allowing active power sharing. The voltage levels of utilized ESSs can be higher or lower than the output voltage. The inductors of the converter are connected to a single switch; therefore, the converter requires only one extra active switch for each input, unlike its counterparts, hence resulting in reduced element count. The proposed MIC topology is compared with its counterparts concerning various parameters. It is analyzed in detail, and then, this analysis is validated by simulation and through a 1-kW prototype based on a battery/ultracapacitor hybrid ESS. [ABSTRACT FROM PUBLISHER]

This paper presents a robust sliding-mode observer (RSMO) for state-of-charge (SOC) estimation of a lithium-polymer battery (LiPB) in electric vehicles (EVs). A radial basis function (RBF) neural network (NN) is employed to adaptively learn an upper bound of system uncertainty. The switching gain of the RSMO is adjusted based on the learned upper bound to achieve asymptotic error convergence of the SOC estimation. A battery equivalent circuit model (BECM) is constructed for battery modeling, and its BECM is identified in real time by using a forgetting-factor recursive least squares (FFRLS) algorithm. The experiments under the discharge current profiles based on EV driving cycles are conducted on the LiPB to validate the effectiveness and accuracy of the proposed framework for the SOC estimation. [ABSTRACT FROM AUTHOR]

In this paper, an optimization framework for the calibration of energy management in plug-in hybrid electric vehicles (PHEVs) is proposed. The framework is based on the modeling of hybrid vehicles as hybrid systems in the mathematical sense, i.e., as a system, whose input is composed of continuous and discrete variables. This allows for the flexible integration of discrete decisions, such as drive modes and gear selection. Hybrid optimal control problems are then formulated, which seek optimal continuous and discrete system inputs, and methods for the efficient solution are described. The framework also allows for the incorporation of losses that occur due to a change in a discrete variable. The results can then be used to automatically calculate lookup tables for optimal gear shifts, optimal torque split between the motor/generator and the internal combustion engine, and the determination of the drive mode (electric or hybrid mode). It is demonstrated that when switching cost is disregarded, the main challenge is still finding the initial costate value. Practical strategies for determining the costate value online are described, containing a rule-based method, a \CO2 optimal method, and predictive energy management. The most important implementation issues are discussed, and the results of real-world experiments of predictive energy management are shown. [ABSTRACT FROM PUBLISHER]

Cell voltage equalization is inevitable to ensure years of safe operation of series-connected energy storage cells, such as lithium-ion batteries and supercapacitors (SCs). Although various kinds of cell voltage equalizers have been proposed, most equalizer topologies require multiple switches and/or a multiwinding transformer, resulting in complex circuitry and poor modularity. In this paper, a single-switch single-transformer equalizer using a forward–flyback resonant inverter (FFRI) with a voltage multiplier is proposed. The required switch count of the proposed equalizer is the minimum without impairing modularity due to the single-switch circuitry with no need for a multiwinding transformer. An experimental equalization test performed for eight SCs connected in series successfully demonstrated the equalization performance of the proposed equalizer. The FFRI can be extended as a “resonant input cell,” and by combining one of resonant input cells and a voltage multiplier, a single-switch resonant equalization charger that is basically a charger with an equalization function is also derived. An experimental charging test using the resonant equalization charger was also performed, and its equalization-charging performance was demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a control strategy is presented for a high-performance capacitively loaded loop (LLC) multiresonant dc–dc converter in a two-stage smart charger for neighborhood electric vehicle (NEV) applications. It addresses several aspects and limitations of LLC resonant dc–dc converters in battery charging applications, such as very wide output voltage range while keeping the efficiency maximized, implementation of the current mode control at the secondary side, and optimization of burst mode operation for current regulation at very low output voltage. The proposed control scheme minimizes both low- and high-frequency current ripples on the battery while maintaining stability of the dc–dc converter, thus maximizing battery life without penalizing the volume of the charger. Experimental results are presented for a prototype unit converting 390 V from the input dc link to an output voltage range of 3–72 V dc at 650 W. The prototype achieves a peak efficiency value of 96%. [ABSTRACT FROM PUBLISHER]

This paper presents the design and control of a high-efficiency multiphase dc–dc converter for a truck auxiliary power unit (APU) fed by a fuel-cell stack. The power-stage design methodology and the operation of the designed power stage used to achieve high efficiency are described in detail. To operate the designed converter as a truck APU, the mode transfer control scheme, where smooth transitions of the voltage and current control modes are necessary, is proposed, and the current controller design procedure is described. A 5-kW four-phase dc–dc converter prototype is built with the proposed power-stage configuration, and the proposed control strategy is applied to control the dc–dc converter. The efficiency of the converter is more than 99.5% at near 10% load and above 98% from 10% to 100% load range. Simulations and experimental results are provided to verify the feasibilities of dc–dc converter operation and the proposed control strategy in the truck APU application. [ABSTRACT FROM PUBLISHER]

Plug-in hybrid electric vehicles (PHEVs) will play a vital role in future sustainable transportation systems due to their potential in terms of energy security, decreased environmental impact, improved fuel economy, and better performance. Moreover, new regulations have been established to improve the collective gas mileage, cut greenhouse gas emissions, and reduce dependence on foreign oil. This paper primarily focuses on two major thrust areas of PHEVs. First, it introduces a grid-friendly bidirectional alternating current/direct current ac/dc–dc/ac rectifier/inverter for facilitating vehicle-to-grid (V2G) integration of PHEVs. Second, it presents an integrated bidirectional noninverted buck–boost converter that interfaces the energy storage device of the PHEV to the dc link in both grid-connected and driving modes. The proposed bidirectional converter has minimal grid-level disruptions in terms of power factor and total harmonic distortion, with less switching noise. The integrated bidirectional dc/dc converter assists the grid interface converter to track the charge/discharge power of the PHEV battery. In addition, while driving, the dc/dc converter provides a regulated dc link voltage to the motor drive and captures the braking energy during regenerative braking. [ABSTRACT FROM PUBLISHER]

Various types of cell voltage equalizers that exchange charges among cells have been proposed for series-connected lithium-ion cells. During equalization, cells are possibly cycled not only over a conventional period that ranges from seconds to hours but at a high frequency that is equal to the operating frequency of the equalizers as well. This paper investigates how the high-frequency cycling occurs and the factor that affects the life performance of the cells during high-frequency cycling. Experiments on charge–discharge cycling at frequencies of 1–100 kHz were performed for lithium-ion cells. The capacity of cells cycled at frequencies below 10 Hz significantly deteriorated, whereas the capacity decay of cells cycled at higher frequencies were identical to the corresponding calendar degradation. Simulation analyses revealed that the cycling current at high frequencies served only to charge and discharge the double-layer capacitance C \rm dl, whereas the current that flows through the charge-transfer resistance Rct, indicating the charge-transfer process, dominated at low frequencies. A correlation between the degradation trend and current distribution to Cdl and Rct was observed, implying that the calendar degradation and the degradation due to the charge-transfer process were the major causes of capacity decay in the frequency range below 10 Hz. [ABSTRACT FROM PUBLISHER]