We quantitatively investigate the reduction of the voltage error caused due to deadtime by introducing multilevel inverters. In particular, the voltage errors of a flying capacitor multilevel inverter with carrier phase shifted modulation, a diode-clamped multilevel inverter with carrier phase disposition modulation, and a 2-level inverter are theoretically investigated via circuit analysis. Based on a theoretical study, the voltage errors of multilevel inverters with different levels, circuit topologies, and modulation methods and the voltage errors of a 2-level inverter, are comparatively verified via simulation and experimental results. Moreover, output current total harmonics distortion (THD) validate based on simulation results. The simulation and experimental results demonstrate that the voltage errors and harmonics are significantly reduced by utilizing the multilevel inverters. We expect that the results presented in this paper will provide useful guidelines for the introduction of multilevel inverters in practical inverter systems.

Condition monitoring techniques, which help in monitoring the operation status of on-board devices and vehicle environment from the driver cab, have been introduced in some railway vehicles. Most of these techniques consist of a single transmission line through a train line. However, it is difficult to install new transmission lines to make information transmission redundant owing to equipment limitations. For this problem, vehicle condition monitoring systems through wireless communication are being studied for their easy installation. In this study, we proposed a hybrid communication network combining wireless and wired communication, and developed its configuration method. This hybrid communication network is expected to increase the speed of wireless communication and redundancy of wired lines. Furthermore, we developed a method to calculate the processing time of the proposed network configuration method. We also implemented the proposed method in a prototype system to demonstrate the effectiveness of hybrid communication networks.

In comparison to pn junction isolation ICs, dielectric isolation ICs have several advantages such as high blocking voltage, small isolation area, high thermal resistance and small interferences among integrated devices, which result in small chip area, multi high output power and floating electric source operation in Dielectrically Isolated High Voltage large electric capacity Power ICs (DI-HVPICs). In this paper, our series of R&Ds for Si DI-HVPICs with the above advantages are introduced in almost time series. On the other hand, SiC semiconductor gets along with the DI-HVPICs in its physical properties and is expected synergistic effects in SiC DI-HVPICs. However, since physical and electrical deference between SiC and Si result in several difficulties in the design of device structure and production process. SiC DI-HVPIC has been investigated in detail and a few solutions have been found, thus conceptual design of 1200V·65A output devices and one chip inverter SiC DI-HVPIC of 600V·25kW class for brushless motors have been attempted, and its rough chip size has been estimated.

At present, there is a growing demand for energy saving to prevent global warming. Thus, the railway industry is also focusing on energy saving methods. Power consumption of running trains has a large variation of approximately 20% caused by drivers' operation. Therefore, improving the running profile can considerably reduce energy consumption. Numerous algorithms for generating energy saving running profiles have been researched and developed. To adapt energy saving operation to various environments, we developed a technology that maintains punctuality without reducing the energy efficiency when temporary differences occur in driving conditions. We propose a method that determines the re-creation command point to complete the re-creation at the switching point of the driving operation in the existing energy-saving target pattern, to achieve both punctuality and ride comfort. As a result of verifying the effect of the proposed method on the conventional method via a simulation, it was confirmed that the proposed method can prevent the increase in the number of operation changes when the driving conditions change, whereas the conventional method increases the number of operation changes.

This paper proposes a three-phase wireless power transfer (WPT) system with a three-phase-to-three-phase matrix converter. The proposed system directly converts power from an AC grid to high-frequency AC for WPT. The three-phase WPT system with the matrix converter is effectively expands the lifetime of the WPT system. A novel hybrid commutation method, which is suitable for the WPT system with a resonant characteristic, is proposed to avoid the commutation failure of the matrix converter. The strategy of the proposed hybrid commutation is based on an estimation of the current direction considering the resonant characteristics and elimination of commutation in the critical area. The proposed commutation method achieves an AC input-current total harmonic distortion (THD) of 4.7% with the resonant three-phase load without a current sensor on the high-frequency side. Furthermore, the proposed WPT system achieves a system efficiency of 88.2% at a load of 4kW.

This paper proposes a torque ripple suppression control method considering the radial force ripple to reduce the torque ripple and vibration generated when a switched reluctance motor is driven by vector control. The proposed method is based on the estimated torque and radial force derived using theoretical equations, and it superimposes harmonic currents on the q-axis current reference to cancel out the ripple components of torque and radial force. Moreover, the effectiveness of the proposed method has been demonstrated through experiments. At 300 min^-1, it was observed that the amplitudes of the sixth harmonic components, which are the main component of the torque and radial force ripples, are suppressed by 14.5% for torque and 14.8% for radial force compared with those of the conventional control for a certain combination of gains introduced in the proposed method. In addition, the noise suppression effect of the proposed method was measured using a sound level meter.

This paper proposes a passive common-noise canceller (PCC) capable of cancelling the common-mode voltage generated by voltage source inverters. The proposed canceller is characterized by its simple circuit configuration consisting of only passive elements; three common-mode transformers and Y-capacitors are used. The basic principle and characteristics of the PCC are described in this paper. Two prototypes, i.e., a through-type PCC and a wound-type PCC, are constructed and tested. The experimental results with a voltage source PWM inverter using SiC-MOSFETs show that the two PCCs can suppress the CM voltage even in a frequency band up to several MHz, and that iron losses in the magnetic core can cause a temperature rise in the PCCs.

It is known that the harmonic current of a motor affects torque ripple. Therefore, to take into account the harmonic current in finite element analysis, the voltage input needs to be evaluated however, voltage input analysis is more time-consuming than current input analysis. In this paper, we propose a method to predict the harmonic current and torque ripple of the voltage input analysis of the sine wave by only using the result of the current input analysis of the sine wave in the surface permanent magnet synchronous motor.

In this study, the authors experimentally verify the improved effects of DC supply voltage utilization by the addition of a third harmonic on pulse-voltage-injected two-phase modulation. Two-phase modulation is known for its low switching loss and high DC supply voltage utilization. However, its output voltage spectrum is spread out over a wider frequency band. Therefore, a novel two-phase modulation scheme using pulse-voltage-injection method was published previously. However, this scheme decreased the DC supply voltage utilization. To address this, the authors compare the experimental results with and without third harmonic addition and verify the effect of increasing this utilization using a three-phase voltage-fed inverter. Present results indicate that third harmonic addition improves the DC supply voltage utilization of this novel modulation scheme. Furthermore, the authors compare output voltage waveforms and spectrum, output current waveforms, and conversion efficiency to verify that the third harmonic addition does not introduce any new problems.

The position information for railway vehicles is encoded by the position detection sensor by analyzing the multiple metallic markers placed on railway tracks these markers are detected using on-board equipment. This enables position detection for railway vehicles. However, the optimal distance between these metallic markers considering lift-off and rail displacement has not yet been studied. Therefore, we evaluated the effect of sensor misalignment on detection sensitivity. We examined the placement distance between the metallic markers and found that the best encoding is achieved when the placement distance is 300mm.

When designing electric motors, many types of performances (electrical and mechanical characteristics) must be predicted with good accuracy. In general, these performances are determined based on complex theoretical calculations, but theoretical calculations include various assumptions. Therefore, it is difficult to eliminate prediction errors when predicting performance, and it is necessary to improve accuracy by referring actual test data. Recently, with the digitalization of the manufacturing process, a large amount of actual data has been converted into a database, and it is expected to be put to effective use. Here, a neural network that predicts various performances of electric motors using a large amount of actual data as a training dataset, is constructed to achieve uniform and high-precision performance prediction via deep learning. Its practical use for actual design work is verified in this study.

The application of input-series output-series (ISOS) connected dual active bridge (DAB) converters has advantages in bidirectional power transmission and isolation. However, their application makes it difficult to maintain the voltage balance. In this study, a voltage balancing control method for ISOS-connected DAB converters with no auxiliary circuits is proposed. The proposed control changes methods according to the amount of load. Furthermore, a hierarchized simple controller is proposed to connect a large number of DAB converters for transmission and isolation in high voltage DC (HVDC) systems. The simulation and experimental results indicate that the proposed method can balance the voltage in bidirectional power transmission between two DC grids with unequal voltages.