In the future, a tsunami may occur in Japan due to a large earthquake. Railway companies must take measures for tsunami evacuation. In order to protect the lives of many people, we must ensure quick evacuation. However, train announcement for tsunami evacuation has become a major issue and currently takes too long. This study proposes train announcement for quick evacuation.

This paper proposes a multiport converter based on a flying capacitor converter topology for use in a battery management system. The proposed circuit operates in discontinuous current mode and pulse frequency modulation in order to reduce inductor volume. The circuit achieves load fluctuation compensation and maximum power point tracking of the photovoltaic (PV) system by deciding duty ratio based on load current and PV output current. According to the experimental results, an efficiency of more than 95.8% was achieved under all operation conditions. In addition, the maximum efficiency reached 98.8% at the rated load (750W). Furthermore, the inductor volume reduced by 85.5% compared to that of the conventional circuit using two inductors.

MOSFETs generally have excellent switching characteristics, and their switching losses can be reduced by synchronous rectification. Furthermore, using the body diode of MOSFET, it is possible to remove any external freewheeling diodes. However, the body diode of a SiC-MOSFET has two major problems: the on-state voltage of the body diode is high, and a reverse recovery current occurs. These problems are appeared by the current flowing through the body diode during the dead time of synchronous rectification. To prevent these problems, we propose a synchronous rectification scheme with substantial zero dead time control. In this type of control, we apply a circuit to detect current by integrating the voltage generated in the wiring inductance of the semiconductor device. A short-circuit current flows by substantially eliminating the dead time, but it is limited by providing a period of suppressed gate voltage. In this paper, we present the principle of this scheme, measurement results of the loss when the MOSFET is turned-on/off, and control parameters. Using this scheme, it was confirmed that the loss when the MOSFET is turned-on/off could be reduced.

We are developing current-detection technology that directly measures the main current of a high-power semiconductor module using the wiring inductance of the module. In a previous study, we proposed a circuit that detects current by integrating the voltage generated in the wiring inductance between the sense emitter and emitter terminals of the IGBT (Insulated Gate Bipolar Transistor) module. In this study, we developed a total current detection scheme for parallel-connected modules.

The basic principle of this scheme is that the total current can be obtained by the total of each voltage generated on the wiring inductance of each module. It was realized by using only one integrating circuit. A challenge for this study was avoiding reflection caused by impedance mismatch. We addressed this by adding a termination resistance with the same value as the characteristic impedance.

This study presents a magnetic polarity detection method of an initial rotor position estimation for permanent magnet synchronous motor drives without a position sensor. The magnetic polarity detection method utilizes stator core magnetic saturation caused by the rotor magnet and uses current responses when a high frequency or impulse voltage is applied to the motor. Recently, capacity enlargement, miniaturization, and cost reduction of the motor have been steadily progressing and motors with complicated magnetic saturation characteristics are available. The authors have developed a new magnetic polarity detection method for initial rotor position estimation that is suitable for many motors having common or complicated magnetic saturation characteristics. In the proposed method, high-frequency voltage waves with different amplitudes are applied to the motor. The proposed method measures the motor current ripple components and can estimate the magnetic polarity by using the amount of d-axis inductance variation caused by magnetic saturation. The basic idea, computer simulation, and experimental results are discussed in this paper.

The authors have proposed an isolated medium-voltage AC-DC converter using a Modular Matrix Converter (MMxC). The proposed circuit directly converts medium three-phase AC voltage to DC voltage because the MMxC has a high breakdown voltage capability. Therefore, the proposed circuit can be downsized because it does not need a commercial transformer to convert the medium voltage to the low voltage. This paper presents a level-shifted PWM control in the proposed circuit's MMxC to generate the multi-level output voltage. When the MMxC output voltage frequency is equal to the switching frequency, the level-shifted PWM control is more suitable than phase-shifted PWM control for generating the MMxC multi-level output voltage. Level-shifted PWM control can reduce the source current harmonics and the MMxC switching loss. The total-power-factor of the high-frequency transformer can be improved by level-shifted PWM control. The theoretical waveforms of applying level-shifted PWM control to the proposed circuit can be experimentally obtained using a 6-kW small power system. In addition, this control method's effectiveness is verified, compared with the conventional control method which generates the three-level PWM waveform in the MMxC.

This paper describes the quantitative comparison results of two pulsating torque controllers with evaluation axes of vibration amplitude and energy consumption. Moreover, this paper proposes a balance torque control that realizes vibration reduction and energy saving simultaneously.

This paper describes a method to analyze the harmonic components of the air-gap flux density distribution of a 3-phase cage induction motor, by considering the influence of the circumferential slot arrangement, stator winding pattern, and distribution of air-gap permeance by leakage flux. The proposed method is based on an analytical model of the permeance and magnetomotive force distributions. The proposed method is also applied to the analysis of a cage induction motor under starting conditions by considering the leakage-flux magnetic saturation. As a result, the harmonic components of the torque at the starting conditions are shown quantitatively. The proposed method is also confirmed using the numerical analysis method by considering the main flux magnetic saturation. From the comparison of these calculated results, the proposed method is shown to be appropriate and useful for quantitative estimation of the harmonic torque of a cage induction motor.

This letter proposes a measurement method for the parasitic components on a PCB for a high-frequency inverter circuit to estimate the DC-bus parameters on the PCB accurately. The proposed method enables accurate measurement with a short jig that applies the shunt-through method for the DC-bus parameter evaluations. The validity of the proposed method is further demonstrated by comparisons with the results of electromagnetic analysis.