In this paper, we describe the control of electronic frequency converters (EFCs), which enables them to continue independent operation in the event of a fault, which is necessary to replace all the frequency conversion facilities in the Tokaido Shinkansen to EFCs. To continue independent operation of the EFCs under faults, we have developed a new overcurrent suppression control scheme applied to the three-phase AC input and output EFCs. We confirm through simulations that the new control suppresses fault current effectively and enables the EFCs to continue operation through a series of operations in which short-circuit faults occur at the feeding circuit, and the circuit breaker interrupts the circuit at the location of the fault following its occurrence and re-closes it after a short interval.

Train localization is an essential technology for effective train control. Currently, train localization primarily relies on using track circuits and balises, which are placed along the track to provide precise location information. However, balises have to be placed at intervals of a few kilometers. This increases maintenance costs and makes them vulnerable to being damaged by ice blocks falling from moving trains. Therefore, in this study, we propose a method for absolute train localization based on structure detection and identification using a 1D-LiDAR sensor to reduce the number of balises. Structure identification is achieved using scan matching. In the experiments using a car, the proposed method achieved an identification success rate of over 90%. We also considered the effect of raindrops by filtering the measurement data. By testing and analyzing the identification results, we successfully reduced all cases of misidentification.

During variable speed operation, the energy loss of an induction motor varies depending on the time waveforms (trajectories) of rotational angular velocity, torque, and rotor flux. Therefore, the optimal trajectories should be derived to minimize the energy loss under the given drive conditions. Several motor parameters, such as rotational damping coefficient and core loss resistance, vary based on the operating points. A design method of optimal trajectories with these variations should be discussed for energy saving. In this paper, the optimal trajectories (rotational angular velocity, torque, rotor flux) considering the rotational damping characteristics and the core loss resistance that vary based on the operating point are derived by applying an analytical method. The trajectories near each operating point are derived, and the overall trajectory is derived by connecting them. The rotational damping characteristic at the operating point is obtained from the experimentally measured data. A core loss resistance map is derived by subtracting the known loss component from the experimentally obtained loss map, and the core loss map data at each operating point are obtained and used to design the trajectories.

Mitigating delay propagation owing to excess dwell time at stations is crucial for ensuring stable transport regarding high-frequency urban train services. Previously, we assumed that only one train could enter the entire station section because trains may move back at a station section, which worsens the delay propagation. In this paper, we propose a partial moving block signaling operation, in which trains are operated by moving block signaling at a station after the platform doors open. We numerically verify the effectiveness of reducing the delay time based on case studies including the whole line. The results reveal that the partial moving block signaling operation can further mitigate delay propagation. However, turn-back stations present bottle-neck owing to their fixed block signaling restriction.

The efficiency of dual active bridge (DAB) converters decreases further as the input/output voltage ratio deviates from the transformer turn ratio of one. A 5-level DAB converter that replaces the primary circuit with an FC-type 3-level circuit has been used to solve this limitation so far. However, the optimization of the staircase voltage waveform is required and is complicated in such converters. In this paper, a DAB converter with an FC-type 9-level converter leg in the primary circuit is proposed. It uses multilevel squared voltage waveforms to expand a high-efficiency operation range and eliminate any waveform optimization. Experimental results show that the proposed converter can maintain a high efficiency on a wider operation range compared with the conventional converter.

In a boosting transformer feeding system (BT feeding system), the electrical circuit comprises negative feeders, booster transformers, and boosting wires, with the current flow restricted in the rail section. Although this system has merits such as attenuating the effect of inductive disturbances on telecommunication lines, the effects of a boosting wire disconnection on the system remain unclear. Therefore, this paper presents the findings of an investigation into the effects of a boosting wire disconnection on a BT feeding system.

In this study, we developed a four-wheel driven autonomous mobile robot to transport heavy objects on narrow alley and steep slopes. The robot, which weighs 450kg, is driven by four 650W hub motors to climb 20-degree 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 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 can transport heavy objects over steep slopes and travel in a narrow alley with high accuracy.

This paper proposes combining an active circuit with a passive EMI (electromagnetic interference) filter, which can suppress the conducted noise of an electric compressor in vehicle air conditioning system. The proposed active filter is characterized by connecting the active circuit in series with the Y-capacitor, ensuring that the volume of the EMI filter is not increased. In an experiment using a vehicle compressor, conducted noise could be suppressed by approximately 12dB in the frequency range from 150kHz-6MHz.

For the realization of carbon neutrality and an advanced information society, we have previously developed a novel current-limiting circuit breaker composed of a fuse, a power semiconductor and a fuse exchanger. However, its feasibility has been confirmed only for fault current interruption in a low voltage range of 100-500V. In this paper, the current-limiting circuit breaker was successfully used for fault and load current interruption at DC 1.5kV, thus demonstrating the high versatility of the circuit breaker.

D-systems, which inherently possess the ability to separate positive and negative phase components, are used in many applications such as flux estimation, back EMF estimation, current control, and harmonic disturbance suppression. D-systems are realized using inverse D-matrices. To implement a D-system in a discrete-time manner, discrete-time realization of the inverse D-matrix is essential. This paper proposes a new discrete-time realization of the inverse D-matrix, which is the most compact and has inherently characteristic root invariance between continuous-time and discrete-time realizations.

This letter studies the design of electromagnetic interference (EMI) noise mitigation for large-current SiC power modules with integrated DC-link capacitors based on the visualized near magnetic field strength in a prototype power module wiring. This method verifies that symmetrically placed DC-link capacitors in a power module is effective in reducing MHz band-noise current.

Our laboratory focuses on the miniaturization, weight reduction, and cost reduction of motor drive systems within the field of power electronics.