To reduce carbon dioxide emissions from mobility, electrified vehicles and mobility have been rapidly increasing in recent years. In this regard, this paper presents the latest trend of technologies supporting mobility electrification, such as electric motors, inverters, and related technologies including vehicle-to-everything, as social systems.

Electric vehicles (EVs) and renewable energy (RE) are expected to increase in the path to achieving carbon neutrality. EVs with vehicle grid integration (VGI) can compensate for the fluctuation of RE to utilize RE more effectively and reduce fossil fuel consumption for thermal generation. This research aims to quantify CO₂ reduction from VGI using the demand and supply power system simulator and actual usage data of vehicles. Evidently, EVs with charge control (V1G) reduces 0.9 ton of CO₂ per EV per year and EV with charge and discharge control (V2G) reduces 1.9 ton of CO₂ per EV per year compared to non-controlled-charging. Additionally, the impact of VGI to EV battery degradation is quantified for the future improvement of VGI operation design to reduce CO₂ emissions and suppress battery degradation.

Double-rotor motors are a promising configuration for electric aircraft propulsion, aiming to minimize the overall weight of the powertrain by leveraging their high-power factor. This study proposes a double-rotor motor with an axially extended closed-slot structure to secure the stator and reduce harmonic rotor losses. Subsequently, a novel cooling structure, termed as direct coil cooling, is implemented in the proposed motor, and a prototype small-scale stator is fabricated to evaluate the enhancement in current density. Lastly, a partitioned rotor core with carbon fiber reinforced plastic (CFRP) retaining ring is applied for high-speed operation.

This study presents the development of a small electric vehicle (EV) traction drive motor using Fe-based amorphous laminated cores that can be mass produced. The following innovative technologies are developed to realize the amorphous laminated core: (1) production technology for thicker amorphous alloy foils to reduce the number of machining operations and (2) punching press technology for amorphous alloy foils that improves the usability of the tool life and maintains quality. The interior permanent magnet synchronous motor (IPMSM) using the amorphous laminated core is designed to be compatible with a 4.5-kW-class small EV traction drive with high efficiency while satisfying the required torque characteristics. A prototype of the designed IPMSM was manufactured and evaluated. The test machine achieves a maximum efficiency of 98.7% and a wide range of efficiencies exceeding 97%. Additionally, the prototype motor exhibit improved efficiency in all operating points compared with a prototype manufactured using an electrical steel sheet.

This paper presents a design study on improving the operating range and lowering the cogging torque for a variable flux surface-mounted permanent magnet motor (VFSPMSM) with a variable airgap structure employing a mechanical stator mover system for the eco-car race called Ene-1 Challenge. Eco-car race application requires designing a traction motor with a wider operating range and higher efficiency under given battery voltage and current regulations. To realize these requirements, the VFSPMSM can change the back-emf constant based on the motor speed by adjusting only the axial alignment between stator and rotor appropriately based on the mechanical stator mover system, resulting in a wider operating speed range without field weakening control. Additionally, it is essential to achieve the lowest cogging torque possible to ensure driving comfort. The design procedure of a VFSPMSM for operating range expansion is examined based on the problems found in the previously designed motor. Finite element method-based design and simulation and experimental drive performance evaluation results of the designed VFSPMSM without field wakening show an extended operating range, improved motor efficiency and minimized cogging torque.

Technical innovations for the downsizing of motor systems are necessary to realize energy savings and roomy and comfortable car interior space in electric vehicles. In this paper, a novel motor drive system with multiple high speed motors and a Magnetic Multiple Spur Gear (MMSG) is proposed for electric vehicles. Furthermore, the factors leading to a high power density and high torque density in an MMSG system are clarified.

This research presents a comprehensive framework for electric bus power consumption and charging systems based on the type of electric bus and charging conditions. The power consumption model ranges from a study model before electric bus operation to a more elaborate model in which the electric bus is equipped with a global positioning system logger and current sensor. The electric bus power consumption and fluctuation characteristics are clarified using Osaka University's inter-campus shuttle bus as an example based on given schedule data and the actual driving record. The demonstration experiment is useful for future bus electrification and energy management.

A current control method using an extended Clarke transformation with the Gram-Schmidt orthogonalization method is proposed for multi-phase induction machine drives by multiple single-phase inverters. By applying the Gram-Schmidt orthonormalization method to the extended Clarke transformation matrix representing the asymmetric winding arrangement under the faults, the unbalanced AC currents for the asymmetric winding condition can be controlled by DC signals in the rotational reference frame similarly with conventional three-phase machine controls. This paper reports experimental verification of the proposed control using a prototype of a nine-phase open-winding induction machine and multiple single-phase inverters.

During the operation of a dual active bridge (DAB) converter, reducing the DC offset current, which causes magnetic saturation, is critical when phase shifts change. In other words, reducing the DC offset current is necessary to improve the transient characteristics of the converter. This paper proposes DC offset reduction methods applicable to DAB converters with multilevel inverter topology. The methods developed for reducing the DC offset current are determined based on the phase shift commands for the transient state. The proposed method consists of the following elements: adjustment of the phase between the legs of the active bridges, adjustment of the phase between the active bridges, and voltage polarity at phase adjustment. The effectiveness of the proposed reduction methods has been verified by performing experiments and simulations, from which the peak values of the inductor current moving average in a period of AC voltages have been observed to be lowered to 3.7A and 0.80A, respectively, using the proposed method.

This study investigates the effectiveness of overhead catenary line voltage compensation when substations are replaced by energy storage systems (ESS). Our findings reveal that the voltage compensation effect is insufficient to elevate the substation voltage to the required level and stabilize the output voltage of the ESS using conventional control methods. Therefore, this study evaluated the voltage compensation effect using a three-dimensional power control method for ESS that considers for both feeder voltage compensation and the state of charge of the ESS. A numerical simulation, which considers in the actual feeder circuit configuration and train diagram, is employed to verify the effectiveness of the proposed control method. The simulation results indicate that the suggested approach requires a limited energy capacity of approximately 25kWh to achieve voltage compensation for overhead catenary lines.

Asymmetric H-bridge converter, which is a typical switched reluctance motor drive circuit, has conduction losses owing to the use of freewheeling diodes that reduce efficiency. In contrast, series-end winding or four-wire converter enables high-efficiency drive by synchronous rectification with MOSFETs. Therefore, switched reluctance motor is driven under the maximum torque control conditions per ampere of the unipolar and bipolar drive methods, which consider the fourth harmonic component of self-inductance, and the efficiency of the three circuit methods is compared through experiments. This letter shows that series-end winding converter has the highest conversion efficiency, and the results show that the efficiency of the bipolar drive increases further.