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This paper proposes a novel active power quality compensator (APQC) topology with a DC voltage balancer for electrified railways. The APQC is composed of a three-leg structure 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 in the traction substation. The third leg controls two common DC capacitor voltages with a small amount of the output currents. Therefore, the current rating of the third leg can be reduced as compared to that of the already proposed three-leg structured APQC. In the control algorithm of the two half-bridge inverters, a strategy based on constant DC capacitor voltage control is used, which does not need any calculation blocks of the unbalanced active, reactive, and harmonic components of the load current to perform the APQC operation. Thus we offer the simplest algorithm for the proposed APQC. The basic principle of the proposed APQC topology with the DC voltage balancer is discussed in detail, and then confirmed by digital computer simulation using the 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 the Scott transformer in traction substations for electrified railways. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a new control algorithm to reduce the capacity of a previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders with reactive power control. The basic principle of the proposed control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is implemented to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is also constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable for Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs. The capacity of dc capacitor CDC is also reduced by 37% with the proposed reactive power control algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we propose a smart charger for electric vehicles with a power-quality compensator. The proposed smart charger consists of four-leg insulated-gate bipolar transistors (IGBTs). Three legs are used for a single-phase full-bridge-based pulsewidth-modulated (PWM) rectifier, which converts power from ac to dc during the battery-charging operation or from dc to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of single-phase three-wire distribution feeders. The fourth leg is used as a bidirectional dc–dc converter for battery-charging and battery-discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power-quality compensator. The basic principle of the proposed smart charger 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 balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and battery-discharging operations. [ABSTRACT FROM PUBLISHER]