Performance Comparison of VSI Based DSTATCOM and ZSI Based DSTATCOM in A Distribution System Network---D-STATCOM (Distribution Static Compensator) is a shunt device which is generally used to improve power quality of distribution systems. It is a device applied for correcting power factor, maintaining constant distribution voltage and mitigating current harmonics in a distribution network. In this paper, effort has been made to use ZSI based D-STATCOM in distribution system and its performance has been compared to VSI based DSTATCOM. The MATLAB/SIMULINK models have been developed to draw the conclusions.
http://www.iosrjournals.org/iosr-jeee/Papers/Vol9-issue6/Version-3/E09633035.pdf
Performance Comparison of VSI Based DSTATCOM and ZSI Based DSTATCOM in A Distribution System Network
1. Under Guidance of
Mr. Parag Nijhawan
Assistant Professor, EIED
Submitted By-:
Ruban Preet Kaur
Roll no. 821141009
2. CONTENTS
Gap In Literature Survey
Objective
Introduction
FACTS
STATCOM
DSTATCOM & Configuration
Models
Results and Discussions
Conclusions
Publication Work
References
3. GAP IN LITERATURE SURVEY
Application of ZSI based DSTATCOM to show
the power quality improvement in distribution
system
Comparison of performance of VSI based
DSTATCOM with ZSI based DSTATCOM in
distribution system for power quality
improvement.
4. OBJECTIVE
To analyze the response of the system with
ZSI based DSTATCOM.
To compare the performance of the VSI
based DSTATCOM and ZSI based
DSTATCOM in distribution system.
5. INTRODUCTION
1. Various power quality problems that are
experienced in the system are [5]:
Voltage dip
Voltage swells
Voltage flicker
Harmonic distortions
Interruptions
Power frequency variations
Low Power Factor
6. 2. These Power Quality problems lead to abnormal
operations of facilities and tripping of protection
devices.
3. In order to improve the quality of power supply in
system FACTS devices are introduced in the main
system.
7. FACTS
Flexible Alternating Current Systems:
incorporates power electronics-based device
and other static controllers to enhance
controllability and increase power transfer
capability
Methods to install facts devices:
1. Series compensation
2. Shunt compensation
8. STATCOM
Static synchronous compensator : A STATCOM is a
voltage source converter (VSC)-based device, with the
voltage source behind a reactor.
Provides Reactive Power Compensation.
Reactive Power Exchange is zero when:
Vi=Vs
Reactive Power Exchange is in Capacitive Mode :
Vi>Vs (DSTATCOM provides reactive power to
System)
Reactive Power Exchange is in Inductive Mode:
Vi<Vs ( DSTATCOM absorbs reactive power from
System)
9. D STATCOM
STATCOM when used in Distribution system is
termed as DSTATCOM.
The building block of a DSTATCOM is a voltage
source converter (VSC) and a capacitor on a DC
bus.
The device is shunt connected to power system
network.
DSTATCOM provides:
a) Power factor correction
b) Harmonic compensation
c) Load balancing
11. VOLTAGE SOURCE CONVERTER
A voltage-source converter (VSC) offers the
regulated output voltage in terms of
magnitude and phase.
VSC either completely replace the voltage or
inject the missing voltage in to the system.
It helps in conversion of DC voltage stored in
storage device to 3 phase AC output [12].
12. CONTROL BLOCK
The Control block performs the function of
recognising Power Quality problems like sags
and swells in voltage due to load disturbance or
fault.
Compensate for Power Quality problems by
generating trigger pulses and terminating
triggers when the disturbance instant has
ended.
The main objective of the control scheme is to
sustain voltage at constant magnitude level at
the instant whenever a sensitive load is
connected.
13. HYSTERESIS CONTROLLER
It does not need any information regarding any load
parameters.
It is for the track down of
reference current.
Instantaneous source current
and reference current are
compared within the small
hysteresis band.
For better track down of source currents a narrow
hysteresis band is preferred.
14. ENERGY STORAGE
The energy demand by the VSC for the
voltage generation to be injected in the
system is met by the help of storage devices.
DC source and the DC capacitor is the
general device that stores reactive power.
It is plugged in parallel to the system.
Energy storage units like flywheels, batteries,
superconducting magnetic energy storage
(SMES) and super capacitors store energy
[16].
15. Z SOURCE INVERTER
A Z-source inverter is a
type of power inverter, a
circuit that converts DC-
AC, AC-DC, DC-DC, AC-
AC.
It functions as a buck-
boost inverter.
Advantages of ZSI
The main circuit of a ZSI can either be the traditional
VSI or the traditional CSI.
Works as a buck-boost inverter.
The load of a ZSC can either be inductive or
capacitive or another Z-Source network.
16. OPERATING PRINCIPAL
The output voltage of DSTATCOM is generated by a
DC – AC voltage source inverter operated from an
energy storage capacitor.
From the DC input voltage source, provided by a
charged capacitor, the converter produces a set of
controllable three phase output voltages with the
frequency of AC power system.
By varying the magnitude of output voltage produced,
the reactive power exchange between DSTATCOM
and AC system is controlled.
22. CASES TO BE DISCUSSED
Reduction in THD Level
Power Factor Improvement
Load Balancing
System Parameters
Line Impedance
Ripple Filter
DC Bus Capacitor
DC Bus Voltage
AC Line Voltage
Non- Linear Load
Rs = 0.01Ω, Ls = 2mH
Rf= 5Ω, Cf = 10µF
500µF
750V
415V, 50Hz
Universal Bridge
25. THD level in sources current in
uncompensated system is 29.03%.
THD level reduces to 11.20% when VSI
based DSTATCOM is employed in the
system.
THD level reduces to 2.58% when ZSI based
DSTATCOM is employed in the system.
26. Case II: Power Factor Improvement
Power factor in distribution system with
inductive load can be improved by
implementing DSTATCOM.
System power factor here without DSTATCOM
is recorded as 0.9506
System power factor with VSI based
DSTATCOM is improved to 0.9567
System power factor with ZSI based
DSTATCOM rises to 0.997.
27. Case III: Load Balancing
The supply currents are balanced and in
phase at all conditions [21].
At 0.1 sec load is changed to two phase
load.
At 0.2 sec load changes to single phase.
At 0.4 sec load gets disconnected.
And all phases of the load are applied again
at 0.45 sec.
29. RESPONSE WITH DSTATCOM
Source Current
v/s Time
With VSI based
DSTATCOM
Source Current
v/s Time
With ZSI based
DSTATCOM
30. THD reduction in source current is more in case
of ZSI based DSTATCOM as compared to that
of VSI based DSTATCOM.
Power factor improvement is comparatively
better in ZSI based DSTATCOM than that in VSI
based DSTATCOM.
Source current is compensated well in
DSTATCOM with ZSI as compared to
DSTATCOM with VSI. Source current waveform
is more sinusoidal when ZSI configuration is
used as compared to case when VSI
configuration is used.
CONCLUSIONS
31. PUBLICATION WORK
Ruban Preet Kaur and Parag Nijhawan,
“Performance Comparison of VSI based
DSTATCOM and ZSI based DSTATCOM in a
Distribution System Network”, IOSR Journal
of Electrical and Electronics Engineering,
Nov-Dec 2014.
