ABSTRACT:
An interline dynamic voltage restorer (IDVR) is
invariably employed in distribution systems to mitigate voltage sag/swell
problems. An IDVR merely consists of several dynamic voltage restorers (DVRs)
sharing a common dc link connecting independent feeders to secure electric
power to critical loads. While one of the DVRs compensates for the local
voltage sag in its feeder, the other DVRs replenish the common dc-link voltage.
For normal voltage levels, the DVRs should be bypassed. Instead of bypassing the
DVRs in normal conditions, this paper proposes operating the DVRs, if needed,
to improve the displacement factor (DF) of one of the involved feeders. DF
improvement can be achieved via active and reactive power exchange (PQ sharing)
between different feeders. To successfully apply this concept, several
constraints are addressed throughout the paper. Simulation and experimental results
elucidate and substantiate the proposed concept.
KEYWORDS:
1.
Displacement
factor improvement
2.
Interline dynamic
voltage restorer (IDVR)
3.
Interline
dynamic voltage restoring and displacement factor controlling (IVDFC)
4.
PQ sharing mode
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Principle of IVDFC system operation during normal conditions (PQ sharing
mode).
EXPECTED SIMULATION RESULTS:
Fig.
2. Per-phase PQ sharing mode simulation results: (a)–(c) for first case
and (d)–(f) for the second case.
Fig.
3. Per-phase simulation results for voltage sag condition at: (a) feeder 1 and
(b) feeder 2.
Fig.
4. Per-phase experimental and corresponding simulation results for DF
improvement case: (a) and (b) receiving feeder; (c) and (d) sourcing feeder
(time/div= 10 ms/div).
Fig.
5 Per-phase experimental results and corresponding simulation results for
voltage sag case: (a) and (b) at feeder 1 and (c) and (d) at feeder 2 (time/div
= 10 ms/div).
Fig.
6 Per-phase experimental results and corresponding simulation results for
voltage swell case at: (a) and (b) feeder 1 and (c) and (d) at feeder 2
(time/div = 10 ms/div).
CONCLUSION
This
paper proposes a new operational mode for the IDVR to improve the DF of
different feeders under normal operation. In this mode, theDFof one of the
feeders is improved via active and reactive power exchange (PQ sharing)
between feeders through the common dc link.
The same system can also be used under abnormal
conditions for voltage sag/swell mitigation. The main conclusions of this work
can be summarized as follows:
1)
Under PQ sharing mode, the injected voltage in any feeder does not
affect its load voltage/current magnitude, however, it affects the DFs of both
sourcing and receiving feeders. The DF of the sourcing feeder increases while
the DF of the receiving feeder decreases.
2)
When applying the proposed concept, some constraints should be satisfied to
maintain the DF of both sourcing and receiving feeders within acceptable limits
imposed by the utility companies. These operational constraints have been
identified and considered.
3)
The proposed mode is highly beneficial if the active power rating of the
receiving feeder is higher than the sourcing feeder. In this case, the DF of
the sourcing feeder will have a notable improvement with only a slight
variation in DF of the receiving feeder.
The proposed concept has been supported with
simulation and experimental results.
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[1]
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[2]
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[3]
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