Akinobu Okui

Application of energy storage system for railway transportation in Japan

The electrical energy is easily controllable compared with other energy. In addition, the electrical energy has an advantageous feature for environment. The electrical energy is also used as the driving energy of the rolling stock in railway. On the other hand, to supply the electric energy with stability, the power supply system needs to have a sufficient supply capacity for demand. The feature of the electric power used in electric railways is that the peak power is large and the average power is low. This is a factor of the power cost increase. Moreover, electric railway is increasing effective use for the resurrection energy of the vehicle and the necessity of the voltage descent measures. In addition, an electric railway needs effective use of regenerating energy from rolling stock for energy conservation, and the measure against a voltage drop. To apply the energy storage system to electric railways is one method to solve these problems. This paper describes the example of application and future view of the energy storage system for DC-electric railway in Japan.

Fundamental study on energy storage system for DC electric railway system

The methods to stabilize power sources have been important issues in DC feeding circuits. A number of applications of energy storage have been investigated so far. In recent years, the development of energy storage media has been remarkable for drive-power supplies of electric vehicles. Therefore, the authors produced an energy storage prototype for a DC electric railway system that consists of electric double-layer capacitors, diode bridge rectifiers, a chopper system and PWM power converters. This paper describes its characteristics and experimental results of the prototype.

Survey of power electronics and electric machine application for on-site railway power system in Japan to realize eco-friendly transportation

In this paper, a survey of novel applications of power electronics and electric machine technology for on-site railway power supply system during the last decade in Japan to realize environmentally friendly transportation is conducted. The applications for high speed railway transportation called Shinkansen are described in Chapter 2 and for conventional railway are in Chapter 3. Not only the technologies which have been put into practical use but also the technologies which are just proposed and tested are introduced. The railway transportation in Japan has already realized CO2 emission index about 19g-CO2/person-km while the index of car is about 168g-CO2/person-km. Electrification is, as a matter of course, key technology to realize such a eco-friendly transportation and its system progresses day by day applying power electronics and electrical machine technologies. The continuing effort of railway companies and manufacturers in Japan to make the system more reliable and more ecological will be grasped in this paper.

Harmonic resonance phenomenon in the DC circuit of inverter to drive LSM

In large-scale inverter systems, a DC circuit connects the rectifier and inverter. And the DC circuit has DC capacitors to smooth and stabilize the DC voltage and the inductance of distribution wires. Therefore, it is possible that a harmonic resonance phenomenon is induced in this circuit. This harmonic resonance phenomenon depends on the characteristics of the DC circuit and the harmonic current generated by the rectifier and inverter. This paper describes the analysis of the input current of the inverter system caused by PWM control and the harmonic resonance phenomenon induced in the DC circuit.

Constitution and characteristics of neutral point clamped type inverter for driving LSM

In Japan, Maglev (magnetic levitation) system adopting a LSM (linear synchronous motor) with the primary side on the ground is under development as a new transportation system. This system needs a power converter with large capacity to drive the LSM which is able to generate variable voltage and variable frequency. For such a power converter, the authors produced a PWM (pulse width modulation) inverter which it is possible to operate as a neutral point clamped type (NPC type) at Miyazaki Maglev Test Track. The authors describe this inverter, laying emphasis on its characteristics and constitution.<<ETX>>