Yoshiaki Taguchi

Simulation results of novel energy storage equipment series-connected to the traction inverter

We developed novel energy-storage equipment that is series-connected to DC side of traction inverter of DC electric railway vehicle. When a train is powering and braking at a high-speed and the equipment boosts an input voltage of the traction inverter, the motor torque increases. Consequently, the mechanical brake force, compensating the electric brake force, becomes less. That leads to less energy dissipation. During the powering period, the acceleration of the train becomes larger due to the boosting operation of the equipment. The equipment charges a part of regenerated energy when it boosts the voltage during braking period, and discharges the stored energy when it boosts the voltage during accelerating period. In this paper, we selected electric double layer capacitor (EDLC) for the energy storage device of the equipment. Firstly, we explain the operational principle of the energy storage equipment: how to boost voltage at a desired level; how to charge and discharges the energy of the EDLC. Next, we described the circuit configuration and the control algorithm. Finally, we present simulation results to evaluate the performance of the energy storage equipment. According to the simulation results, the equipment charged/discharged the regenerated energy smoothly, and controlled the input voltage of the traction inverter at a desired level.

Development of contact-wire/battery hybrid LRV

Contact-wire/onboard battery hybrid railway electric vehicles run on a hybrid power source that enables energy to be fed from contact wires and /or onboard batteries. We developed a contact-wire/battery hybrid LRV (Light Rail Vehicle) and had it manufactured. This paper concerns the hybrid source technology for the contact-wire/battery hybrid system, and on the running results with onboard rechargeable lithium ion battery (600 V-system). The LRV ran on a commercial service on-street line on an actual operation diagram, and recorded a regeneration ratio of 41 % (the volume of regenerated energy divided by the energy consumed in powering), cutting the energy consumption by maximum 30 % over that of existing inverter vehicles, with the hybrid controlled running. The LRV also achieved the running distance by one spell of charge of 25 km over on a street line and 49 km on an existing railway main line.

Reduction of Current and Rise in Temperature of Lithium Ion Battery by Combining with Lithium Ion Capacitor

We experimentally show that by parallelly connecting Lithium Ion Capacitor (LIC) with Lithium Ion Battery (LIB), the current of the LIB decreases, and the rise in temperature, a degradation factor in the quality, is reduced. The rise in temperature of the LIB is related to the current and the internal resistance of the LIB. We also show that the current distribution between LIB and LIC is calculated with high accuracy from a simple model, in which LIB and LIC are represented by a series circuit of internal resistance and capacitance.

Evaluation of a Thermal Network Model for the Traction Battery of the Battery-Powered EMU

We developed a battery-powered and AC-fed dual source EMU (test train) for the purpose of the interoperable service between the AC electrified lines and the non-electrified lines. The eveloped EMU is equipped with a 83-kWh lithium-ion battery system for traction. Thermal management of the battery is an important issue in ensuring long lifetime, and large input/output power. We developed a simple thermal network model to estimate the average temperature of battery cells. The running test results demonstrate that a deviation of the estimated battery temperature is acceptable value of up to 2°C both in summer and winter.

Effective method of using electromagnetic coupling of air-core reactor

To reduce joule loss due to ripple current in multiphase current reversible chopper, we manufactured reactors, which achieve an optimal electromagnetic-coupling coefficient and we tested the new reactors. As a result, the new reactors whose electromagnetic-coupling coefficient is 0.60 reduces ripple current both on each phase and on the total combined when those operate with differential coupling and shift-phase switching. The loss from ripple current is reduced to 31% when the chopper operates with above mentioned condition. When the chopper operates with equal-phase switching and cumulative coupling and employs new reactors whose electromagnetic-coupling coefficient is 0.97, the joule loss due to ripple current is reduced to 11%.