Supercapacitors Energy Storage System for Power Quality Improvement:

[attachment=16427]

Introduction
The first complete electric power system was built by the Thomas Edison in September
1882 in the New York city ;through the steam driven dc generator supplying at 110 Volt.
Due to dc system and low voltage level; the losses in transmission line (I2R) puts the
limitation for the long distance transmission of the power. After development of the
transformer and ac transmission system by L.Gaulard and J.D. Gibbs led to ac electric
power system. In the year 1889, the first ac transmission line in North America was put in
to operation in Oregon between Willamette falls and Portland.



Voltage flicker
DG may cause voltage flicker as a result of starting a machine or sudden change in the
DG output which results in a significant voltage change on the feeder. In case of non
dispatchable source, the output fluctuates.
The voltage flicker can be reduced by controlled voltage starting of Induction generators,
tighter synchronization; Inverters are controlled to limit inrush currents and the change in
output levels so that it must follow the IEEE standards 519-1992[8, 9, 10].

b) Voltage sags
The most common power quality problem is voltage sag; the DG may or may not help.
However, the ability of DG to reduce sags is very dependent on the type of generation
technology and interconnection location, during voltage sag, DG might act to counter sag.
Large rotating machines can help support the voltage magnitudes and phase relationships.
Although not a normal feature, Inverter-based distributed generators can be controlled to
supply reactive power for voltage support during sag [8, 9, 10].


6. Conclusions
Through a critical survey of the literature for the energy storage system especially for
the Supercapacitors energy storage system for improvement of power quality of the
different systems; an overview has been presented. Various aspects of the problem, such as
to provide ride through, stabilization of power system, to make undispatchable power into
dispatchable, to improve power quality of weak transportation system, of aircraft
distribution system UPS, elevator and PDS adopting PI control technique, dynamic voltage
restorer in the island mode, switching transients mode, grid connected mode, in stand alone
for the short term outage.