power quality improvement in three phase four wire distribution systems using dual three leg voltage source inverter based d statcom

1. A Dual Three-leg VSI Based
DSTATCOM in
Three-Phase Four-Wire
Distribution Systems
PROJECT GUIDE PROJECT MEMBERS
V.MADHU SIR V.GANESH
A.NAVEEN
S.SATISH
P.PHANIBABU

2. Abstract:
This paper proposes a dual three-leg voltage
source inverter (VSI) based distribution
static compensator (DSTATCOM) to
compensate unbalanced and nonlinear loads
in three phase four-wire distribution
systems.
 The proposed topology uses two three-leg
inverters having common dc-link with single
dc capacitor and an additional small
capacitor connected from the negative
terminal of VSI to the system neutral.

3. 3. The proposed scheme with
associated control algorithm has the
capability to compensate unbalanced
nonlinear load and hence makes source
current as balanced sinusoidal and at
desired power factor.
4. The control algorithm also ensures
the proper sharing of reactive,
harmonics and unbalance powers
between two VSIs and controls the grid
current total harmonic distortion
(THD) level.

4. Introduction:
1. Distribution static compensators (DSTATCOMs)
are extensively being used for reactive, harmonic
and unbalanced load compensation in three-phase
four-wire distribution systems.
2. However, the use of DSTATCOMs for high power
applications is usually limited by the available
maximum current rating of semiconductor devices
and their switching characteristics.

5. 3.Many parallel inverter schemes for active
power compensation but in this topology a
reduced switch hybrid dual inverter to with a
common dc-link for active filter operation.
4. A shunt active compensator scheme
containing dual active filters operating in feed
forward and feedback modes has been
proposed to compensate the nonlinear
currents&harmonics.

6. Power quality improvement
• Power quality determines the fitness of electric
power to consumer devices.
• The term is used to describe electric power that drives
an electrical load and the load's ability to function
properly. Without the proper power, an electrical device
(or load) may malfunction, fail prematurely or not
operate at all.
• The quality of electrical power may be described as a set
of values of parameters, such as:
• Continuity of service
• Variation in voltage magnitude (see below)
• Transient voltages and currents
• Harmonic content in the waveforms for AC power

8. The Introduction Of A Switching Action And Consequently
Current Interruptions. Provides Current With Different
Components That Are Multiples Of The Fundamental Frequency
Of The System. These Components Are Called Harmonics.

9. We know that in a 3-phase, 3-wire, system there is no
zero sequence current unless there is a ground fault with
ground current flowing. Even if the 3 phases are
unbalanced the vector sum of the three phase currents
will always equal zero in an unfaulted condition, even if
unbalanced, and therefore there is no zero sequence
present unless there is a ground fault.

10. A Flexible Alternating Current Transmission
System(facts) Is Used To Enhance Controllability
And Increase Power Transfer Capability Of The
Network. In Most Of The Applications The
Controllability Is Used To Avoid Cost Intensively.
Type Of Facts Devices are
Series Devices - SSSC,TCSC
Shunt Devices - STATCOM,SVC
Series - series - IPFC,UPQC
Series – shunt - HVDC BANK

14. Proposed Block Diagram:

15. Explanation:
The load consists of both unbalanced
reactive and nonlinear loads and are
drawing currents ila, ilb and ilc.
The topology uses a single dc capacitor
Cdc and an additional small ac capacitor
Cn, which is connected between lower leg
of VSI and neutral. The voltage across Cdc
is maintained at 2×1.6×Vm, where Vm is
the peak of source phase voltage.

16. The selection of Cdc is based on the
rating of dual compensator, The neutral
capacitor Cn is chosen based on the zero
sequence current which is to be
compensated.
In this when our the non-linear loads can
entered it can be sensed by D-STATCOM
device and give the feedback to the
system to control the harmonics&balance
the reactive power.

17. Simulink Results:

19. Future scope
• The Most Advanced Controllers Such As
Fuzzy Network, Artificial Neutral
Network, Instantaneous Power Theory.
• It Can Be Also Used With Mc-upqc To
Make The System More Effective And
Effectiveness.

20. Conclusion:
A dual three-leg DSTATCOM to
compensate unbalanced and nonlinear
loads in three-phase four-wire
distribution systems is proposed. The
performance of this topology to share
unbalanced, harmonic and reactive
powers between two inverters and to
control the grid current THD has been
verified.