The regenerative power in DC electric railways is generated during braking and is shared between vehicles. The sharing contributes to the reduction of the overall power consumption. When there is no powered vehicle running nearby, a light-load regenerative brake control is activated to prevent overvoltage. In that case, the regenerative power cannot be used effectively. Therefore, an appropriate bus voltage can be set as a means of reducing the light-load regeneration control and increasing the regenerative power.

In this study, to effectively utilize the regenerative power, we conducted verification tests on the Yokohama line by changing the bus voltage of DC substations, and determined an appropriate bus voltage that would not affect the train operation. To clarify this voltage, it is necessary to clarify the pattern in which the regenerative power is used. It requires a detailed analysis of the regenerative energy, powering energy, and feeding loss related to the operating energy. This study revealed that lowering the voltage facilitates the transfer of regenerative power to other feeding lines, and quantitatively demonstrated that reducing the amount of restricted regenerative braking energy increases the regenerative energy. The relationship between regenerative energy, power-running energy, and feeding loss was shown, as well as the factors that reduced the operating energy. This method is effective on railway lines where an amount of the restricted regenerative braking energy is generated, such as the Yokohama Line. If the half-tap extra-high-voltage transformer is set to a voltage that lowers when changing one tap from normal on the Yokohama Line, the regenerative power can be further increased without affecting the train operation and the operating energy can be reduced.

In this paper, by applying a control method called power balance mode control (PBMC) to a boost-forward DC-DC converter, we realized a highly stable and responsive converter. The effectiveness of the proposed method was verified using a 48V-100V boost-forward DC-DC converter. From the frequency characteristics of the loop gain, it was confirmed that the PBMC has a larger phase margin and better control stability than conventional control methods. From the load transient-response waveforms, it was confirmed that the PBMC was superior to the conventional control method in both the short settling time to the target value and the small output-voltage fluctuation.

Overall, applying the PBMC to a boost-forward DC-DC converter verified in this study enables control that is both more stable and more responsive than conventional control methods, thereby improving the operation.

Dynamic wireless power transfer (DWPT) chargers are crucial technological components for the future development of infrastructure suitable for electric vehicle (EV)-based transportation and mobility systems in industrial automation. This paper proposes a novel DWPT system for autonomous guided vehicles (AGVs) using single-ended inverters and a multi-transmitter and receiver coil system. The proposed DWPT system, featuring a multi-coil arrangement, exhibits an extremely small, lightweight, and low-cost structure without batteries. It operates stably despite the position deviation of transmitter (Tx) and receiver (Rx) coils without any feedback control, due to a single-ended high-frequency inverter with parallel-series resonant compensation tanks. The performance of the proposed DWPT system was experimentally investigated with a 1.5kW-85kHz prototype, verifying the robustness against dynamic deviations of Tx and Rx coil distances. Additionally, the low peak power profile enabled by the multi-coil system achieves high efficiency and high energy utilization from a practical perspective.

This paper proposes a current-harmonics reduction method for a partial switching power-factor correction (PFC) converter with a proportional-sinusoidal (PS) controller for current control and a phase-shift control for an input current to reduce man-hours for adjustment of the partial switching. The PS controller realizes a stable current control for a peak input voltage larger than a DC-link voltage. In addition, the phase-shift control reduces the current harmonics, depending on the relationship between the input voltage and DC-link voltage. The validity of the proposed method was confirmed by a prototype. In the experimental results, the DC-link voltage and the input current are controlled according to the command value when the peak input voltage is larger than a DC-link voltage by using the current PS control. Furthermore, the current harmonics of the input current are within the limit of the IEC 61000-3-2 standard when the phase-shift controller is applied.

Maintenance worker scheduling generates a daily schedule for each worker group to perform inspection and maintenance work such as cleaning rolling stock when superior trains turn around at a terminal station. Since the schedule varies from day to day according to changes in daily train timetables and rolling stock operations, it is required to be created for each day. This paper proposes a new method for automatic generation of maintenance worker schedules that can consider the priority of constraints by tabu search. It includes a new model and a generation method of an initial solution, and a generation method of neighborhood solutions. In order to confirm the effectiveness of the proposed method, we perform parameter sensitivity analysis of the tabu list. Moreover, we compare an actual schedule with schedules generated by the proposed method, a mathematical programming method that guarantees a theoretically optimal solution, and local search. The results indicate that the proposed method can generate a stable solution within a practical computation time of three minutes with reduced worker loads, regardless of the size of the train schedule.

In recent years, a demand has arisen for smaller traction motors with higher power. This study focused on high-speed rotation for miniaturization and developed a prototype motor using Nd-based bonded magnets. It had a maximum rotational speed of 34,000rpm, which is twice that of existing 50kW-class motors. The motor achieved the desired performance in the test in combination with a reducer. As a result, the weight of the prototype motor was reduced by 54%, and a power density of 6.7kW/kg was achieved.

Our research group focuses on several motors for automobiles, factory automation, and home appliances, etc. Through magnetic field analysis, machine learning, and experiment, we aim to realize high-performance motors. We are committed to the challenge of conducting research contributes to industry, not just research for research.