ABSTRACT
The DPFC is derived from
the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC
with an eliminated common dc link. The active power exchange between the shunt
and series converters which is through the common dc link in the UPFC is now
through the transmission lines at the third-harmonic frequency. The DPFC
employs the distributed concept, in which the common dc-link between the shunt
and series converters are eliminated and three-phase series converter is divided
to several single-phase series distributed converters through the line.
According to the growth of electricity demand and the increased number of
non-linear loads in power grids harmonics, voltage sag and swell are the major
power quality problems. DPFC is used to mitigate the voltage deviation and
improve power quality. Simulations are carried out in MATLAB/Simulink
environment. The presented simulation results validate the DPFC ability to improve
the power quality.
KEYWORDS:
1.
Load flow control
2.
FACTS
3.
Power Quality
4.
Harmonics
5.
Sag and Swell Mitigation
6.
Distributed Power Flow Controller
7.
Y– transformer
SOFTWARE: MATLAB/SIMULINK
BLOCK
DIAGRAM:
Fig. 1. Flowchart from UPFC to DPFC.
Fig. 2.
DPFC configuration.
EXPECTED SIMULATION RESULTS:
Fig 3. three phase voltage sag waveform
without DPFC
Fig. 4. Three phase voltage sag
waveform with DPFC
Fig.5. 3- load current
swell waveform without DPFC
Fig.6 Mitigation of 3- load current swell with DPFC
Fig.7. Total harmonic distortion of load voltage
without DPFC
Fig.8. Total harmonic distortion of load voltage with DPFC
CONCLUSION
This
paper has presented a new concept called DPFC. The DPFC emerges from the UPFC
and inherits the control capability of the UPFC, which is the simultaneous
adjustment of the line impedance, the transmission angle, and the bus voltage magnitude.
The common dc link between the shunt and series converters, which is used for
exchanging active power in the UPFC, is eliminated. This power is now transmitted
through the transmission line at the third-harmonic frequency. The series
converter of the DPFC employs the DFACTS concept, which uses multiple small
single-phase converters instead of one large-size converter. The reliability of
the DPFC is greatly increased because of the redundancy of the series
converters. The total cost of the DPFC is also much lower than the UPFC, because
no high-voltage isolation is required at the series-converter part and the
rating of the components of is low. To improve power quality in the power
transmission
system, the harmonics due to nonlinear loads, voltage sag and swell are
mitigated. To simulate the dynamic performance, a three-phase fault is
considered near the load. It is shown that the DPFC gives an acceptable
performance in power quality improvement and power flow control.
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