Electrical Engineering in Japan最新文献

This paper proposes a new method for unit commitment (UC) with Quantum Predator Prey Brain Storm Optimization (QPPBSO). The UC problems may be expressed as a mixed integer nonlinear programming problem in which binary variables mean on/off conditions of units and continuous ones imply their output. Recently, Evolutionary Computation (EC) has been applied to the UC problems due to the existence of indifferentiable cost functions such as large-scale steam turbine units, etc. However, there is still room for improvement in EC because the UC problems have high nonlinear features. This paper focuses on the integration of EC with Quantum Computing (QC) that is promising in power systems. Specifically, this paper combines QC with Predator Prey Brain Storm Optimization (PPBSO) of high-performance EC. The effectiveness of the proposed method is demonstrated in the New England 39-node system.

To introduce ICT to the fisheries industry, it is important to secure a power supply. To supplement solar power generation at night, on rainy days, and on cloudy days, we have devised a rocking electric power generator that generates electricity from the rocking motion of waves. We report on the building up a rocking electric power generator. The generator can generate electricity by a rocking motion. It achieved to 1.28 VA rotational speed of 0.78 rps, and the maximum output current is 40 mA. The load resistance is available at 240 Ω or more. We clarified the relationship between rocking motion and power generation in a rocking power generator, using evaluation sensors each of motion and electricity. As a result of increasing the power generation efficiency of the air gap generator, the load current also flows to the coil, which causes the electromagnetic brake to work more strongly. Due to the influence of the electromagnetic brake, it was not possible to increase the generated voltage. It was found that a driving torque by the pendulum load was required that exceeded the braking force produced by the electromagnetic brake. To increase the pendulum load, the float becomes to lose its balance because the center of gravity becomes higher. The relationship between the pendulum load and balance is important for stable levitation.

The switching frequency of silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) should be increased to maximize their benefits in power conversion circuits. However, the switching loss increases when the switching frequency is increased. Generally, the gate resistance is designed to be small to reduce the switching loss for one cycle. However, SiC MOSFETs have a higher parasitic gate resistance than Si power devices. This paper proposes reducing the switching losses by “overdriving” the SiC MOSFETs, in which the gate voltage Vg is designed to be higher than the rated gate–source voltage of the SiC MOSFET. The relationship between gate voltage Vg and switching loss is clarified both theoretically and experimentally. Additionally, the effect of “overdrive” on the long-term reliability of SiC MOSFETs is evaluated by conducting continuous switching tests. The results show that “overdrive” can maximize the benefits of SiC MOSFETs based on the expected lifetime of the power conversion circuit.

This study examines the gate magnetic coupling technique, a gate drive technology for series-connected power semiconductor devices, and discusses the generation principle of gate voltage oscillation specific to the technique and its countermeasures. Additionally, this study proposes two gate-drive circuits designed to suppress gate voltage oscillation. The experimental results obtained using 3.3 kV/750 A SiC-MOSFET/SiC-SBD power modules demonstrate that the proposed methods can suppress gate voltage oscillation and reduce the voltage imbalance between the series-connected elements.

To establish a novel section locating technique for a water-tree degraded 22 kV cross-linked polyethylene (XLPE) cable, that is, included in another undegraded cables, we measured a reflected injection pulse at the impedance mismatch, which is dependent on water trees. The injection pulse was propagated into cables to be measured, and the measured arrival times of reflected pulses containing residual charges due to water trees were varied depending on the locations of water-tree degraded cables. The section locating was achieved by using the arrival time of the reflected pulse.

Currently, no technology has been established to measure the amount of ocean microplastics (MP) less than 5 mm. As a basic study of the quantitative evaluation, the authors proposed measurement method using the attenuation of transmitted light for the amount of microplastic that concentrated by dielectrophoresis. In this study, we report effective collection method of microplastics by combining an electrode structure that generate negative dielectrophoresis and a driving method using additive Synthesis sine wave.

Battery Energy Storage Systems (BESS) are compatible with renewable energy, so they are becoming increasingly popular around the world. On the other hand, the number of fire accidents are increasing with the spread of batteries, and as a result of the author's own analysis of these fire accidents, the author found phenomena unique to BESS fires. Therefore, the author will investigate whether Japan domestic laws and regulations are compatible with these unique phenomena and propose necessary safety countermeasures.

Characterizations of pulsed power output for pulsed power generator using GaN FET have been evaluated and compared with using SiC-MOS FET. The fast rise/fall time of output voltage without the dependance on the dummy load has attractive feathers. However, the surge voltage between drain and source terminals, exceeding the maximum rating occurred due to the fast turn-off speed feathers of Gallium nitride (GaN) FET, which has limited the power capability. The inductive energy storage pulsed power generator using GaN FETs as opening switches has developed, and the output obtains a maximum voltage of ∼900 V with rise/fall time of <20 ns. The fast current interruption characteristics by the turn-off of GaN FET lead to high voltage-pulsed output.

In this paper, a method for extracting constant power from transformers on power lines is presented. The secondary side power equation is obtained based on the circuit equation for power superposition using a single-phase transformer. Using this equation, an area discrimination method of the speed versus torque characteristics of the permanent magnet synchronous motor and a power superposition control method in the area are proposed. To validate the proposed method, the discrimination method was verified via simulation and experiment with boundary conditions. Similarly, the power superposition control method was verified via simulation and experiment, with the command current controlled using a power estimator. The results verify the discrimination and power superposition control methods.

If a voltage dip gets lower than a certain threshold at the moment when a transformer is energized, its mitigation is required. For this reason, when a transformer is energized, the voltage dip is calculated in advance and the need for its mitigation is considered. From the viewpoint of preventing unnecessary countermeasures, highly accurate calculations are required. However, electromagnetic transient analysis, which is known as a method with high accuracy, is not practical because its operation is rather complicated. In this paper, the analytical circuit is simplified by simulating the magnetizing inductance of the transformer with the inductance and the series connection of the ideal switch, and analytical formulas for the flux and current in the winding are derived for each switching mode. The calculated inrush currents and voltage dips during transformer energization using the derived analytical formulas agreed well with the results from electromagnetic transient analysis, which handled the nonlinear current-flux characteristics precisely.