Download [2] block diagram of dstatcom

Improvement of Power Quality of a Grid Connected
Distributed System Using DSTATCOM
1.
SHIVARAJ S, 2.RAKESH J, 3 PRAVEENA ANAJI
1.
- U G Students, 2,3. - Assistant Professor
Department of Electrical &Electronics, Jain Institute of Technology Davanagere-03
Abstract:
Power quality is one of the
major issues in the modern electrical power
system the variation in the magnitude of
voltage causes serious problem in the
connected system. In order to solve this
problem the modern way of mitigation is the
use of static synchronous compensator
(STATCOM). It is very difficult to incorporate
the filter at the consumer premises as well as
at the generator and transmission levels as the
equipment gets seriously affected. Hence the
best place of incorporative static synchronous
compensator is at distribution grid.
In this paper the distribution
STATCOM is explained with its operation,
modeling and a case study which is executed
using MATLAB Simulink software and the
results and analyzed using theoretical
calculation and finally the STATCOM
operation is verified.
[1] INTRODUCTION:
As
the
electrical
system
is
continuously upgrading with the time there
exist new problem with synchronization,
transmission distribution etc., in order to meet
the load demand we are inter connecting the
tie-lines so that the power form different
generating sources can be utilized. Hence
when this type of synchronization is done
there is a creation of problems of harmonics,
voltage sag, voltage swell etc.,
Voltage sag and voltage swell are the
two major problems which has got very
dynamic effect on the power system if voltage
supplied to the equipment is less than the rated
it will not work or either it will work at very
low efficiency and if the voltage supplied is
above the rated windings get damaged. Hence
in order to provide reliable uniform, power
modern method of mitigation is use of
STATCOM.
A battery energy system is used to
supply the reactive power which is connected
shunt with capacitor bank. The STATCOMs
are voltage source converter and this is
powered by the battery bank.
The entire system is connected shunt
in distribution network so that whenever the
voltage of the line crosses the set value the
STATCOM circuit absorbs the active power
and whenever the voltage of the line falls then
the set value the STATCOM supplies the
reactive power.
[2] BLOCK
DSTATCOM:
DIAGRAM
OF
Figure shows the typical block
diagram of STATCOM connected to
distribution line. It mainly consists of the
voltage source converter. That is , pulse width
modulation circuit and capacitor bank,
controller circuit as well as the distribution
line.
The block diagram shown below has
three units with consisting resource unit,
module unit and a control unit.
shunt manner so that required power ratings
can be obtained.
[6] MODELING OF STATCOM:
The theoretical computation of
STATCOM is done based on the current
ratings needed i.e. injection and absorption
currents. As the electrical system mainly
consists of inductive equipment the current
lags the voltage and is shown in figure below,
Figure: Block diagram of
connected to distribution line.
[3]
VOLTAGE
CONVERTER:
STATCOM
SOURCE
Voltage source converters are the
devices which modifies the voltage waveform
i.e. these are power electronic device which
are used to convert DC power to alternating
power using pulse width modulation
technique.
IGBT/GTO are mainly used for this
operation as IGBTs have fast response time it
is mainly preferred.
Fig: Phasor diagram
Hence the output current can be given
as,
[4] CONTROLLER CIRCUIT:
PI controller is used in the
STATCOM circuit which produces an error
signal on comparing with set values, 3 phase
values are set i.e. Vdc for DC bus Vta, Vtb, Vtc
for lines i.e. AC bus.
The PI controllers are calibrated with
suitable proportion and integral value so that
accuracy in error calculation is made.
[5] BESS SYSTEM:
A capacitor bank with BESS (Battery
Energy Storage System) is used which consists
of array of batteries connected in series and
Figure: Single line diagram of DGgrid interfaced system
extra voltage needs to be removed from
the system health point of view.
Hence the DSTATCOM acts as an
additional load so that the battery is
charged. And in case of the less voltage
then the limit the battery supplies the DC
power which is inverted by VSC’s by
pulse width modulation technique and
hence reactive power is supplied into the
grid.
Figure: Schematic representation of
DSTATCOM
Figure: MATLAB model of DSTATCOM.
[7]
OPERATION
DSTATCOM:
OF
DSTATCOM is basically shunt
operated device which mainly operates in
two modes one is injective mode and other
is absorption mode. In the injective mode
the reactive power is supplied into the grid
and in absorption mode the active power is
taken from the system
i.e. if the magnitude of voltage
crosses the limit there exists the condition
of voltage swell. Under this condition the
[8]
SIMULATION
OF
DSTATCOM & ANALYSIS:
The analysis of STATCOM is done
by implementing a case study in MAT Lab
Simulink model. Figure shows the
simulated circuit in MAT Lab software
and the outputs at different conditions.
Transient
response
of
DSTATCOM when connected to a weak
supply system and transient responses of
distribution system with DSTATCOM
without battery for supply, these are the
two cases which we consider while
studying simulation results and the
obtained waves are represented below,
[10] REFERENCES:
1. Yash Pal, A. Swarup, and Bhim Singh,
“A Review of Compensating Type Custom
Power Devices for Power Quality
Improvement” 2008 Joint International
Conference on Power System Technology
(POWERCON) and IEEE Power India
Conference New Delhi, India.
2. Mahesh Singh and VaibhavTiwari,
Figure (a)
“Modeling analysis and solution of Power
Quality
Problems”,http://eeeic.org/proc/papers/50.
pdf.
3.
J. Barros, M. de Apraiz, and R. I.
Diego, “Measurement of Subharmonics In
Power Voltages”, Power Tech, IEEE
Lausanne, Page(s): 1736 – 1740, 2007.
4. Sannino. A “Global power systems for
sustainable development,” in IEEE
General Meeting, Denver, CO, Jun.2004
Figure (b)
[9] CONCLUSION:
From this modeling and analysis we
can conclude that the DSTATCOM is the best
method of providing reliable constant power
so that power quality problems are mitigated.