Electrical Engineering in Japan最新文献

In this paper, the authors propose an ensemble forecasting method using multiple individuals for short-time-ahead (1 h ahead) insolation forecasting by using neuroevolution (NE), in which a genetic algorithm is applied to the learning algorithm of a neural network for insolation. Although the method improves the accuracy compared to a single forecast, NE has a problem that the training time is long. In order to solve this problem, the authors propose a parallelization method of GPU processing for short-time-ahead forecasting and try to solve the problem by parallelizing the GPU.

Electric buses are introduced toward achieving carbon neutrality by 2050, and there is a movement to utilize their storage batteries. On the other hand, the electric power system, where distributed energy resources are rapidly spreading, is becoming increasingly complex, and the impact of charging by electric buses on power system is an issue. In this study, we propose an optimization method for electric bus charge/discharge schedule that considers sector coupling between transportation system and power system. Then, we evaluate the effectiveness of the proposed method from the viewpoints of both the distribution system operator and the electric bus operator by performing power flow calculations using a distribution system model. The results show that the proposed method can contribute to power demand shifting and smoothing power flow in distribution network by charging and discharging, and that multiple evaluation indices, for example, peak-cutting of power flow, line occupation rate, distribution loss, reverse power flow utilization rate, renewable energy rate and CO₂ emissions, are improved compared to the conventional charging scheduling method.

This study proposes a novel integrated transformer structure with simple circuit configuration and miniaturized magnetic components. In a bridgeless flyback rectifier, two flyback converters operate corresponding to the polarity of the AC input, requiring two transformers. This paper proposes a novel winding structure that realizes zero coupling co-efficient between two sets of windings. This enables the integration of two transformers into a single transformer, preventing their flyback operations from interfering with each other. The integrated transformer has approximately 16% lower volume compared to that of conventional transformers. The proposed integrated transformer was built, evaluated, and verified by designing a 75 W-bridgeless flyback rectifier with 100 kHz switching frequency.

This paper reports on a microdevice for compartmentalizing the solution microenvironment that can fractionate the space surrounding spheroids during the culture and differentiation processes, with the aim of verifying the effects of cell–cell interactions in the solution microenvironment on iPS cell differentiation. In this paper, we demonstrated that spheroids of iPS cells were successfully formed on the device and fractionated their microenvironment by a detachable compartmentalization frame (DCF) formed by 3D printing technology.

Blood contains volatile biomarkers related to diseases and metabolism. We developed a biofluorometric gas sensor that measures acetone with high sensitivity and confirmed its significance in lipid metabolism and diabetes when applied to breath measurement. Furthermore, regarding transcutaneous gases that permeate through the skin from blood, a biofluorometric gas-imaging system for ethanol vapor as the target chemical was developed and analyzed the secretion dynamics of transcutaneous gases at each skin site, thus showing the stable release of blood-derived volatile markers from the ear canal. Based on the results, we have developed a headphone-type gas sensor and succeeded in continuous and stable transcutaneous gas measurement, thus indicating the future potential of a novel wearable biosensor for blood VOCs.

Flywheels have several advantages such as long life, high reliability, and high environmental resistance. This paper describes the application of flywheel to uninterruptible power supplies that rotate a motor-generator at commercial frequencies of 3000 min⁻¹. Conventional systems that use flywheel generators require high-capacity semiconductor power converters for energy conversion. Moreover, a specially designed generator is required because the generator operates at variable speed. To overcome these weaknesses, this paper proposes a flywheel generator using a planetary gear, which is a mechanical shaft coupling mechanism. The use of a planetary gear enables the flywheel and generator to rotate at different speed. As a result, even if the flywheel speed drops during a power outage, the generator speed can be kept constant. This paper reports on the design guidelines and experimental verifications for a 1-kW system

In this study, we developed a four-wheel-driven autonomous mobile robot to transport heavy objects on narrow alleys and steep slopes. The robot, which weighs 450 kg, is driven by four 650 W hub motors to climb 20° steep slopes and travel through a narrow alley. Two 2D-LiDARs attached to the front and rear of the robot body are used for highly accurate driving. A method based on the least squares approach for estimating the position and posture of the robot body is proposed by using the point cloud information of the side wall of the narrow alley. Field experiments on test courses demonstrated that the autonomous robot could transport heavy objects over steep slopes and travel in a narrow alley with high accuracy.

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.

Reverse power flow from a photovoltaic (PV) power generation system to distribution system is limited below a certain limit value. The behavior of a power conditioning system (PCS) for large capacity PV power generation system when the output power approached the output power limit value was experimentally estimated. Under the condition, the PCS became uncontrollable. It was pointed out that this phenomenon was caused by the maximum power point tracking (MPPT) control of the PCS. Furthermore, some methods to avoid the uncontrollable condition of PCS were shown.