Yusuke Baba

Electrical Network of Single‐Crystalline Metal Oxide Nanoclusters Wired by π‐Molecules

In a mixed-valence polyoxometalate, electrons are usually delocalized within the cluster anion because of low level of inter-cluster interaction. Herein, we report the structure and electrical properties of a single crystal in which mixed-valence polyoxometalates were electrically wired by cationic π-molecules of tetrathiafulvalene substituted with pyridinium. Electron-transport characteristics are suggested to represent electron hopping through strong interactions between cluster and cationic π-molecules.

A new half-bridge based inverter with the reduced-capacity DC capacitors for DC micro-grid

This paper proposes a new half-bridge based inverter for the DC micro-grid. The proposed topology consists of a three-leg inverter, which can be constructed by an intelligent power module (IPM). Using the IPM gives cost-effective inverters for the dc micro-grid. In the proposed half-bridge based topology with a three-leg inverter, two legs are used for two single-phase half-bridge inverters, where the neutral line is grounded. The third leg performs a power de-coupler balancing the mean value of two dc capacitor voltages. This power de-coupler exchanges the energies between two dc capacitors connected to two single-phase half-bridge inverters. Thus the capacity of the dc capacitors of the half-bridge inverters can be dramatically reduced as compared to those of the previously proposed half-bridge inverters for the dc micro-grid. The basic principle of the proposed half-bridge based inverter is discussed in detail, and then confirmed by digital computer simulation using PSIM software. Simulation results demonstrate that the capacity of the dc capacitors is reduced by one fortieth as compared to those of the previously proposed half-bridge based inverter used in the dc micro-grid.

A half-bridge inverter based current balancer with the reduced dc capacitors in single-phase three-wire distribution feeders

This paper proposes a half-bridge inverter based current balancer in single-phase three-wire distribution systems with the reduced dc capacitors. The proposed current balancer can use a 6-in-1 IGBT module. Two legs perform a half-bridge inverter based current balancer, which compensates the reactive and unbalanced active components on the source-side. The third-leg performs a power de-coupler with a dc-capacitor voltage balancer. This power de-coupler sinks the power fluctuation, which flows into the dc capacitors, caused by the unbalanced conditions of two half-bridge inverters. Thus the capacity of the dc capacitors of the half-bridge inverter based current balancer can be dramatically reduced as compared to those of the previously proposed current balancer. The basic principle of the proposed half-bridge inverter based current balancer with the reduced dc capacitors is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the balanced source currents are obtained on the secondary-side of the pole-mounted distribution transformer, reducing the capacity of the dc capacitors of the half-bridge inverter based current balancer.

A half-bridge inverter based Active Power Quality Compensator using a constant DC capacitor voltage control for electrified railways

This paper proposes a half-bridge inverter based Active Power Quality Compensator (APQC) using a constant DC capacitor voltage control for electrified railways. The APQC is composed of three-leg structured power devices with two common DC capacitors. Two legs perform as two half-bridge inverters, which compensate the unbalanced active, reactive and harmonic currents on the source side through DC capacitor. The third-leg controls two common DC capacitors voltages with a small amount of the output currents. Therefore the current rating of the third-leg devices can be reduced as compared to that of the already proposed three-leg structured APQC. For the control algorithm of the half-bridge inverter based APQC, a constant DC capacitor control based algorithm is used. Any calculation blocks of the unbalanced active, reactive and harmonic components of the load current are not needed. Thus we offer the simplest algorithm for the half-bridge inverter based APQC. The basic principle of the proposed half-bridge inverter based APQC using a constant DC capacitor voltage control is discussed in detail, and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that the proposed APQC can achieve balanced and sinusoidal source currents on the primary side of Scott transformer in the traction substations for electrified railways.

A constant DC-capacitor voltage control based strategy for current balancer in single-phase three-wire distribution systems

This paper proposes a constant dc-capacitor voltage control based strategy for a current balancer in single-phase three-wire distribution systems. The proposed control strategy only uses the constant dc-capacitor voltage control block commonly used in active power conditioners to calculate the compensation current. No calculation blocks to obtain the reactive and unbalanced-active components are necessary. Thus, we provide the simplest possible control strategy for the current balancer. The basic principle of the proposed control method is discussed in detail then its validity is confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of unity are obtained on the secondary side of a pole-mounted distribution transformer while retaining unbalanced load current conditions with a lagging power factor.

A half-bridge inverter based Active Power Quality Compensator with a DC voltage balancer for electrified railways

This paper proposes a half-bridge inverter based Active Power Quality Compensator (APQC) with a DC voltage balancer for electrified railways. The APQC is composed of three-leg structured power devices with two common DC capacitors. The first two legs perform as two half-bridge inverters to generate compensation currents and the third-leg is used for DC voltage balancer. The first-leg is connected to α-phase and the second-leg is connected to β-phase. Two DC capacitors are connected in series and midpoint is grounded. These two half-bridge inverters exchange and balance active power for two feeders through two common DC capacitors and compensate reactive and harmonic components of the distorted load currents. The third-leg controls two common DC capacitors to balance voltage level of each other. Using proposed APQC, the primary side of Scott transformer attains balanced and sinusoidal source currents. The principle and control algorithm of proposed a half-bridge inverter based APQC is discussed in detail. The proposed APQC is confirmed by both the PSIM computer simulation software and prototype experiment system. Simulation results show that the proposed APQC can achieve balanced and sinusoidal source currents in secondary side of Scott transformer.