Download (EVs) on single-phase three-wire distribution feeders

REDUCED-CAPACITY SMART CHARGER FOR ELECTRIC VEHICLES ON
SINGLE-PHASE THREE-WIRE DISTRIBUTION FEEDERS WITH REACTIVE
POWER CONTROL
ABSTRACT:
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.
INTRODUCTION:
The charger, which uses the PWM rectifier with a bidirectional dc–dc converter, can support the
grid in the following ways: 1) time-of-day-based coordination of the charging power; 2)
regulation of the reactive power when connected to the grid; and 3) returning power to the grid
when there is a need for peak shaving. Various studies analyzing the value and the potential
impact of these effects on the utility grid have been reported.
The analysis of the reactive power operation in a charger was described in detail. The operation
modes of the proposed battery charger were divided into quadrants based on the active and
reactive power on the ac side.
Then, the control method, the dc capacitor design, the ac inductor design, and the loss evaluation
were discussed. Other small-capacity loads are connected to each feeder with a neutral line, and
their voltage rating is 105 Vrms. The load conditions are always unbalanced.
If the charger is connected to single-phase three-wire distribution feeders, perfect reactive power
compensation for each feeder with a power factor of unity cannot be achieved on the low voltage
side. Moreover, unbalanced conditions remain on the secondary side of the pole-mounted
distribution transformer.
This imbalance causes an imbalance in the feeder voltages. It is well known that this imbalance
of the source current on the secondary side of the distribution transformer increases the loss in
the distribution transformer. Balancing the currents on the two feeders is effective for balancing
the feeder voltages and reducing the losses.
EXISTING SYSTEM:
A charger with a three-leg-structured PWM rectifier with a bidirectional dc–dc converter
for a split-phase transformer in single-phase three-wire feeders has been proposed. However, the
third leg is controlled by fixed 50% duty to keep the two output voltages of 120 Vrms balance.
Thus, unbalanced active and reactive currents cannot be compensated on the secondary side of
the pole-mounted distribution transformer. The proposed smart charger, reducing the capacity of
the three-leg PWM rectifier, which performs as the smart charger, is strongly required. A sourceside power factor of 0.9 is acceptable. Thus, controlling the reactive power on the source side is
effective for reducing the capacity of the proposed smart charger. In this paper, we propose a
new control algorithm for the previously proposed smart charger to reduce the capacity of the
three-leg PWM rectifier, which performs as the smart charger, with reactive power control on the
source side.
PROPOSED SYSTEM:
The proposed smart charger consists of four-leg insulated-gate bipolar transistors (IGBTs). The
first and second legs are connected to Feeder1 and Feeder2, respectively. The third leg is
connected to the neutral line. These three legs are used as a single-phase 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 feeders by connecting the third leg to the
neutral line. When EVs are not connected to the proposed charger, the power quality is also
improved on the secondary side of the pole-mounted distribution transformer.
ADVANTAGES:

The capacity of dc capacitor CDC is reduced by 37% with the proposed reactive power
control algorithm.
BLOCK DIAGRAM:
PASSIVE
FILTER
THREE PHASE
CONVERTER
DC TO DC
CONVERTER
12V
DC
DRIVER CIRCUIT
5V DC
PIC CONTROLLER WITH
BUFFER
BATTERY
TOOLS AND SOFTWARE USED:

MPLAB – microcontroller programming.

ORCAD – circuit layout.

MATLAB/Simulink – Simulation
APPLICATIONS:

Electric vehicles (EVS )
CONCLUSION:
In this paper, we have proposed a new control algorithm to reduce the capacity of the
previously proposed smart charger with reactive power control. The smart charger consists of
fourleg structured IGBTs. Three legs are used for a single-phase PWM rectifier, where two legs
are connected to each feeder and the third leg is connected to the neutral line. This PWM rectifier
can compensate reactive and unbalanced active currents on single-phase three-wire distribution
feeders. The fourth leg is used as a bidirectional dc–dc converter for battery charging and
discharging operations. The authors have shown theoretically that controlling the reactive power
on the source side can reduce the capacity of the previously proposed smart charger. The basic
principle of the proposed control algorithm was discussed in detail and then confirmed by digital
computer simulation using PSIM software.
REFERENCES:
[1] Y. Mitani, “Method and system leveling power load,” Japan Patent Office, 4862 153 (P4 862
153), Jan. 25, 2012.
[2]
Nissan
Motor
Corporation.
[Online].
com/EN/NEWS/2011/_STORY/110802-01-e.html
Available:
http://www.nissanglobal.