The method for detecting the train speed and position without using wayside equipment, such as track circuit, contribute to developing technologies for energy-saving operations and simplifying protection equipment. In this paper, the analysis methods of measured data from accelerometers are studied to determine the train speed and position simply and accurately and to make speed profiles. To effectively use the data measured by the accelerometer, discrete Fourier transform is applied to remove the noise from the measurements. Two accelerometers were used to increase accuracy, and differences of sensing and the state of motion of the train were considered to remove noise effectively. Experimental results show that the speed and distance of train are clearly different from the actual values when the calculation is directly based on measured data. Therefore, the speed and distance of train could be obtained adequately and speed profiles are also generated when the proposed method is applied. Finally, the proposed methods were confirmed by using a satellite positioning system and speedometer records.

The mitigation of delay propagation owing to excess dwell time at stations is crucial for ensuring stable transport in high-frequency urban train services. Previously, we assumed that only one train could enter the entire station section; however, the fixed block section should be divided to mitigate further delay propagation. In this paper, a novel control method is proposed to mitigate delay propagation with multiple block sections at a station. We numerically verify the effectiveness of reducing the delay time based on case studies. The results reveal that dividing the station section into multiple block sections can further mitigate delay propagation. Moreover, the results show that the block section at a station should be equally divided.

This paper proposes a novel method for detecting the gain fault of 3-phase AC current sensors in power electronics systems. In conventional methods, the sensor gain fault is detected by comparing the RMS values of the detection current of each phase. However, for an unbalanced three-phase load, a higher current will flow in the phase with the lower impedance, which causes misdiagnoses. In contrast, the proposed method utilizes the product of the detection current in each phase and sum of the detection current as part of the abnormality calculation (gain error calculation) of each current sensor, which can reduce calculation errors caused by an imbalance in the three-phase load. Simulation results show that the method can calculate the abnormality of the sensors with small error even if there is an imbalance in the three-phase load. Moreover, simulation results under conditions of varying current amplitude and frequency indicates that the method can detect sensor faults under transient conditions.

Vehicle detectors are required to operate in various environments. Current detectors employ various types of sensors including ultrasonic, loop coil, and image sensors. However, there exist some problems such as temperature and wind effects, maintenance problems, and accuracy degradation during nighttime. To solve these problems, we propose a vehicle detector that utilizes a 3D sensor based on near infrared laser and Time-of-Flight. This sensor can acquire a three-dimensional image that includes the distance data, unaffected by the external factors mentioned earlier. Therefore, our proposed vehicle detector design can be applied to traffic volume measurement, vehicle classification, multiple lane detection, etc. This paper discusses the application of the proposed vehicle detector in several scenarios.

With the recent developments in information and communication technologies, automatic train operations have been attracting increasing attention. In this paper, we propose a novel train group control method that utilizes train operation forecasts under complex timetable disruptions. In particular, we examine the effects of the proposed method using simulation results. The results reveal that the proposed method reduces the number of iterations required for searching the optimal cruising speed compared with bisection methods.

In recent years, applying SiC to switching devices of traction inverters has been attracting attention. By applying SiC devices, motors are able to increase the regenerative energy and reduce the power consumption by shortening powering time due to improved motor torque performance by driving motors with the larger current than the case of an Si-IGBT inverter. In this study, the trade-off relationships between increasing the loss of inverters and the effect of saving-energy are quantitatively studied by numerical simulations, assuming that SiC devices are applied for 1.5kV DC railway vehicle traction inverters.

This paper presents a capacitor-voltage-balancing control scheme for an isolated medium-voltage AC-DC converter using level-shifted PWM control of a modular matrix converter (MMxC). The proposed isolated AC-DC converter is composed of the primary MMxC with level-shifted PWM control, high-frequency transformer, and secondary H-bridge circuits. The high-frequency transformer of the proposed circuit can be downsized because the level-shifted PWM control scheme makes the rated frequency of the high-frequency transformer equal to the switching-frequency. The proposed capacitor-voltage-balancing control can compensate for the capacitor voltage imbalance of the MMxC using the positive-sequence and negative-sequence circulating-currents with a power supply frequency and high-frequency voltage. In the proposed control system, the three feedback control systems with DC control variables can be developed to compensate for the capacitor voltage imbalance. The effectiveness of the proposed capacitor-voltage-balancing control scheme and the control systems is verified by experiments using a 200V, 5-kW laboratory prototype.

This paper proposes a novel current control method for permanent-magnet synchronous motors with double independent three-phase windings (DIW-PMSMs). It is extremely difficult to achieve stable and fast current control of DIW-PMSMs because of the inevitable magnetic coupling between two windings. Many of the existing methods suffer from slow and/or low performance when trying to achieve stable control. The proposed method adopts a new approach using “synthetic vector physical quantities” and succeeds in achieving stable and fast current control of DIW-PMSMs. The method has the following features: a) It has application versatility that can be applied to both three-phase PMSM and six-phase PMSMs; b) It can be regarded as a current control method that expands and systematizes the VSD method for a six-phase PMSM with two identical windings; c) When applying the proposed method to a six-phase PMSM, it results in one of the most systematic and simplest VSD methods; d) It can also be applied to DIW-PMSMs with strong magnetic coupling and/or 2% parameter difference between the two windings. The effectiveness of the proposed method is verified though extensive simulations under harsh operating conditions.

The direct ac-ac converter is an effective circuit topology for high-efficient power conversion in induction heating (IH) applications. The conventional pulse frequency modulation (PFM)-based power control scheme causes audible noises between the adjacent IH loads which operate at different switching frequencies. As a solution for the technical issue, a new fixed-frequency power control methodology for a single-phase direct ac-ac converter is proposed in this paper, featuring a wide range of soft switching operation and robustness for abnormal load conditions. The principle of the proposed pulse modulation is explained in detail with the logic circuit diagram of controller. The performances of the ac-ac converter and power controller are demonstrated by simulation, after which the effectiveness is revealed in terms of the power control range and soft switching operation.

Our research focuses on the high-performance analog integrated circuits and subsystems for information and communication systems. In particular, the main theme is interface circuit technology for optical/electrical conversion devices, which are the key to optical communication systems.