CO₂ reduction is the biggest challenge in the world, and the vehicles play an important role. Regulations governing CO₂ emission reduction for vehicles will be tightened in the future. Automotive manufacturers design EVs, PHVs, HEVs, FCVs to meet CO₂ regulation. However, vehicles with the internal combustion engine will continue to retain a large market share in the near future. This report presents recent technology trends in fuel economy for electrical and conventional vehicles.

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In the twenty-first century, rapid advances are being made in the electric propulsion of vehicles as a countermeasure of global warming. In addition, CO₂ emissions from all vehicles are to be stringently regulated to 95g/km by 2020. Thus, most automakers around the world have had to develop not only hybrid electric vehicles but also conventional internal combustion engine with energy-saving technology. Battery technology (Li-ion) and semiconductor technology (SiC, GaN) for automotive power supply systems have proceeded to the mass-production stage. In 2011VDA (German OEMs and suppliers) announced the adoption of DC48V for the market of 2020. In this paper, we analyze the needs and impact of DC48V and compare it with DC42V (current technology). We also try to portray the future view under DC60V for automotive power supply systems.

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Battery systems, widely used as energy storage devices for electric vehicles (EVs), suffer from issues such as short lifetimes and low power density. In this paper, a hybrid energy storage system (HESS), which is a combination of a supercapacitor (SC) and a battery, that can be charged using wireless power transfer (WPT) technology, is presented. This combination can achieve the desired energy capacity and power density. Moreover, it offers an acceptable energy storage size for applications such as EVs and machines. In order to optimize the system for the energy and power requirements of a power train system, an optimal design principle for the HESS is proposed. The battery charge degree, Q, is defined and calculated to minimize the entire weight of the HESS. The optimal SC ratio can be obtained on the basis of the defined operation constraints. This optimal combination can reduce the weight of the storage system by 30% for the given operation pattern. Furthermore, under some conditions with optimized charge times, the SC can serve as the sole operated energy storage device and charge power can be increased using WPT.

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When the cells of energy-storage devices such as electric double-layer capacitors (EDLCs) are connected in series, it results in voltage imbalance in each cell because of the nonuniform properties of the individual cells. In a previous research, the authors proposed a novel cell voltage equalization circuit using an LC series circuit, and they examined the effectiveness of this circuit. However, the characteristics of the cell voltage equalization operation depend on each cell voltage difference. Therefore, the proposed circuit has a disadvantage that the equalization time tends to be longer than other cell voltage equalization circuits with a boosting circuit. This paper proposes an equalization time reduction method that uses a pseudo-random number sequence generated by the linear congruential generators. The proposed method can reduce the average equalization time without adding any other active or passive elements. The effectiveness of the proposed method is verified through the experimental results. According to the experimental results, the proposed equalization time reduction method reduces the equalization time to 86.5% of the conventional method.

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One of the main problems of Electric Vehicles is the mass and volume of the electric powertrain. In particular, the power converters, that interface the storage unit with the motors, are composed of bulky and heavy components. These converters suffer from considerable power losses caused by hard-switching and recovery phenomena. Therefore, the efficiency of the converter decreases, and the mass and volume increases because it is necessary to use bulky and heavy cooling systems to dissipate the power losses produced by these phenomena. This study proposes a novel recovery-less boost converter that can achieve zero-current switching and reverse-recovery reduction by using two saturable inductors for the reduction and softening of the switching transition. Consequently, a high-efficiency performance can be achieved. In addition, the proposed two saturable inductors offer advantages of mass and volume reduction of the auxiliary inductors in comparison with other conventional converters for reverse-recovery reduction. Therefore, power density of the proposed converter can be increased. In this paper, the circuit configuration, the operating principle, and the reverse-recovery reduction of the proposed converter are described. Moreover, the design procedure of the proposed saturable inductors is presented. Finally, the effectiveness of the proposed converter is validated through experiments. As a result, a reduction in both the recovery phenomenon and the auxiliary inductor volume is confirmed, with a 72% reduction in the recovery phenomenon and a 63% reduction in the auxiliary inductor volume.

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This paper describes variable magnetization machines, which are capable of varying the magnetization state of permanent magnets during operation. A pulse current on the stator windings creates a magnetic field on the rotor; this can be used to manipulate the magnetization state of the rotor magnets. Regulating the magnetization state according to the machine operating condition can reduce machine losses. A proof-of-principle machine was designed and fabricated. A series of experiments was conducted to evaluate the torque-speed envelope and efficiency contours of the fabricated machine. A full-scale machine was then designed with a modified magnetic circuit for application to an electric vehicle and evaluated using finite element analysis. A control strategy for the magnetization state during machine operation is proposed, and the losses during a driving cycle with the strategy were evaluated.

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This paper presents the design of a signal-injection-based sensorless interior permanent magnet synchronous motor (IPMSM) for a traction drive in hybrid electric vehicles (HEVs). To realize an accurate design, the sensorless safety operation region (SSOR) is introduced to account for the cross-coupling magnetic saturation and harmonics of inductance distributions. The SSOR defines a working point on the maximum torque per ampere trajectory at which the motor can perform sensorless operation with a guaranteed performance in the steady state. The reliability of the SSOR was verified in experiments using a prototype. The influence of the IPM motor geometry on the SSOR was then examined. Under the given dimensional constraints, the design of a 100Nm-10 kW 12-pole, 18-slot IPMSM was optimized to meet the requirements for the target traction drive in an HEV. The validity of the proposed design was verified by using a MATLAB/SIMULINK-based dynamic simulator.

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As a type of non-permanent magnet motor, the Wound Field Flux Switching Motor (WFFSM) has attracted considerable research interest owing to its simple structure. Because both the field and the armature windings are placed in the stator, there is no need for bushes or a slip ring for field coil excitation. The rotor has neither a winding nor a permanent magnet, and therefore, it is suitable for high-speed and high-power-density motors used as HEV/EV drives.  This paper focuses on the high-power production mechanism of WFFSM by increasing the field winding current, which allows for the extraction of higher power from a given WFFSM within given inverter voltage and current constraints. In order to achieve higher power production, one of the main factors is reducing the armature reaction in terms of higher power factor control and applied voltage suppression. In this study, we focus on magnetic saturation by increasing the field current excitation, which leads to saturation of the armature reaction. Experimental studies using a 100-kW test WFFSM confirm that the high-power production mechanism based on increasing the field winding current contributes to the extraction of higher power from the tested WFFSM.

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It is known that the electroconductive polymer, poly-3,4-ethylenedioxithiophene/poly-styrenesulphonic acid (PEDOT/PSS) has high generality, electroconductivity, and transparency. We have been studying blending fibers that consists of the electroconductive polymer and another polymer (e.g. polyvinyl alcohol: PVA) to achieve high strength along with high conductivity for practical applications. As an automobile application, we developed a prototype of a fabric seat heater made using the blended conductive fibers, and confirmed that it warmed up in approximately half the time required by a conventional seat heater.

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In the near future, many distributed power systems will be connected to utility lines in the local area. The demand for control accuracy of utility interactive inverters will likely increase beyond present capabilities. The utility interactive inverter requires FRT capability to compensate for utility voltage fluctuations. A deadbeat control with disturbance compensation and 1MHz-PLL control with quasi-dq transformation were applied to a utility interactive inverter using an FPGA based hardware controller. The FRT characteristics were verified through simulations and experiments, and the superior characteristics of the proposed method were verified.

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