Electrical Engineering in Japan最新文献

This study investigated cost-effective energy strategies for realizing net zero CO₂ emissions in Japan by 2050, employing an energy system optimization model with hourly electricity balances. The detailed temporal resolution enables the model to capture the intermittency of variable renewable energy (VRE) and the costs of system integration measures. Siting constraints on VRE, such as prohibiting solar PV and onshore wind developments in forests and offshore wind developments inside fishery rights areas, are incorporated in the model to reflect the environmental protection and social acceptance perspectives. Simulation results imply that a well-balanced power generation mix, combining renewables, nuclear, gas-fired with carbon capture and storage, as well as ammonia-fired, would contribute to curbing mitigation costs. In contrast, a simulation case with very high VRE penetration poses economic challenges. The average shadow price of electricity in 2050 in a 100% renewables case (RE100) is projected to be more than doubled from a reference case which is based on middle-of-the-road assumptions. Marginal CO₂ abatement cost in 2050 increases from 49,200 JPY/tCO₂ in the reference case to 75,300 JPY/tCO₂ in the RE100 case. The economic viability of high VRE penetration is improved by relaxing the siting constraints, although it may raise environmental and social concerns.

In this paper, a calculation method is proposed for the radial suspension force of a bearingless motor with a surface-mounted permanent magnet (SPM) rotor, a consequent-pole permanent magnet (CPM) rotor, and a homopolar permanent rotor (HPM). The radial suspension forces are calculated mathematically and analytically using the airgap flux density. It was confirmed that the proposed radial force equations are practical to calculate the suspension force based on the airgap flux density. The CPM bearingless motor and bearingless AC HPM have salient pole rotors that interact with the 2-pole Magnetomotive force (MMF) to generate 6- and 10-pole components. As a result, the radial suspension force of the CPM bearingless motor is generated by 8- and 6-pole, and 8- and 10-pole magnetic flux, whereas the bearingless AC HPM produces the radial suspension force by DC and 2-pole components. The shaft torque, the suspension force, and efficiency were also compared for SPM, CPM bearingless motors, and bearingless AC HPM. Consequently, the torque value of the CPM bearingless motor is quite close to SPM bearingless motor. Moreover, the suspension force of the CPM bearingless motor is quite close to bearingless AC HPM.

In order to improve the mileage per charge of battery electric vehicles (BEV), dynamic wireless power transfer systems are being developed. There are some problems such as is the wide gap between coils when mounted under the floor of a vehicle, and the effect of foreign objects between coils on power transmission. In-wheel coils, in which the coils are placed inside the wheel, have been proposed as a solution to these problems. However, they a plastic wheel such as CFRP and cannot reduce the gap between coils. In this paper, we propose a coil configuration in which the coils are placed inside the tire and the wheel. This configuration has the advantage of using a conventional aluminum to reduce the gap between coils. The effectiveness of this method is demonstrated via simulations and experiments.

This paper proposes the application of an adjustable speed diesel engine-driven power plant employing a doubly-fed induction generator to an isolated small-scale power system including renewable power sources. This type of power plant can contribute to fast and flexible power balancing regulations under vacillating power supplies such as wind, solar, and other renewable power sources. Installation of a battery system is also considered, which can assist coordinately with the power plant to augment renewable power sources in the isolated power system.

Recently, dynamic wireless power transfer (DWPT) for battery electric vehicles has been actively studied because it can enhance their cruising range and reduce their charging time. An SS type WPT circuit is simpler and more efficient than a WPT circuit with a filter, such as an LCC type WPT circuit. By contrast, the leakage magnetic field generated by the harmonic current is a problem that needs to be addressed. The leakage magnetic field is limited by the Radio Act and the Ordinance for Regulating Radio Equipment in Japan. This study aims to reduce the leakage magnetic field generated by the harmonic current using a high-frequency switching technology. The inverter and rectifier are operated using pulse width modulation (PWM) with a high carrier frequency. The effectiveness of the proposed method was experimentally verified using a GaN inverter and rectifier. As a result, the proposed method can drastically reduce the leakage magnetic field, especially, the magnetic field generated by the current harmonics of order greater than five.

A torque-difference-amplification torque vectoring differential (TDA-TVD), which is composed of a two-input-two-output system, has a great potential for cornering maneuverability; however, the overall controllability of slip ratio or driving force control is difficult owing to its complex mechanical structure. In order to enhance the controllability of TDA-TVD, this study proposes a design method to apply a driving force controller (DFC) with a decent slip ratio and driving force controllability, which was originally intended for independent wheel drive systems. An experimental verification on a slippery road using a real vehicle with the TDA-TVD indicated that the DFC can be applied to the TDA-TVD and that it improves the overall performance of the traction control.

Ball-screw-driven stages are widely used as feed systems of industrial equipment such as machine tools. Rolling friction in the stages causes a large tracking error called a quadrant glitch at a velocity reversal. Although the model-based friction compensation reduces the quadrant glitch, it often leads to a tracking error in the direction opposite to the quadrant glitch. This study aims to present a control system that reduces both the quadrant glitch and opposite-direction error. This is achieved by combining the model-based friction compensation and initial value compensation. The effectiveness of the proposed control system is verified by simulations and experiments with two-axis experimental setup.

As the mileage of the electric railway increases, the unevenness of the contact wire may separate the contact wire and the contact strip. Simultaneously, a disconnection arc discharge is generated by the molten metal bridge. This causes the contact wire to melt and evaporate causing it to break. A few studies have conducted experiments to prevent the contact wire from disconnecting. Based on the results thus obtained, they presented their hypotheses considering conditions sch as the current and time required for melting and evaporation of molten metal bridge and arc generation. In this study, a calculation method for the melting and disconnection phenomenon of the contact wire. Its mass increased when the currents from both sides of the contact wire were taken into consideration. Therefore, we obtained that the convection and radiation play an improtant role for calculation of the melting amount mass of contact wire.

This paper proposes a multi-port DC-AC converter with high efficiency and high-power density. The proposed circuit consists of a full bridge converter, a series active filter, and an unfolder circuit. The proposed circuit reduces the low switching losses owing to the square waveform operation with low switching frequency. In addition, the proposed converter improves the power density because the number of inductors is significantly reduced compared to the conventional multi-port converter. As the experimental result, the maximum efficiency of the proposed circuit reached 99.3%. Finally, the power density of the proposed converter is evaluated by the Pareto front curve. As the result, the power density of the proposed circuit was increased by 1.6 times in comparison with the conventional circuit.

In restricted slit-like space by two polymer plates, the effects of the space width, current and atmospheric pressure on arc electrical field were investigated experimentally for high-current air arc above several kA. As a result of the evaluations, it was found that the electrical field increases significantly with the pressure rise under condition near 0 MPa-g, and it increases with current in the restricted space at the width less than 10 mm. Comparing the electrical field in using polymer with glass for the restricted material, it revealed that the electrical field has current dependence caused by the space width in addition to increasing effect to above 1.5–2 times by the ablation or spallation effects of the polymer.