Direct Power Control Of Series
Converter Of Unified Power-Flow Controller With Three-Level Neutral Point
Clamped Converter
ABSTRACT:
A unified power-flow controller (UPFC) can enforce unnatural
power flows in a transmission grid, to maximize the power flow while
maintaining stability. Theoretically, active and reactive power flow can be
controlled without overshoot or cross coupling. This paper develops direct
power control, based on instantaneous power theory, to apply the full potential
of the power converter. Simulation and experimental results of a full three-phase
model with non ideal transformers, series multilevel converter, and load
confirm minimal control delay, no overshoot nor cross coupling. A comparison
with other controllers demonstrates better response under balanced and
unbalanced conditions. Direct power control is a valuable control technique for
a UPFC, and the presented controller can be used with any topology of voltage-source
converters. In this paper, the direct power control is demonstrated in detail
for a third-level neutral point clamped converter.
KEYWORDS:
1.
Direct power
control
2.
Flexible ac transmission control (FACTS)
3.
Multilevel converter
4.
Sliding mode control
5.
Unified power-flow controller (UPFC)
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.1.Laboratory
setup.
CONCLUSION:
The
DPC technique was applied to a UPFC to control the power flow on a transmission
line. The technique has been described in detail and applied to a three-level
NPC converter. The main benefits of the control technique are fast dynamic
control behavior with no cross coupling or overshoot, with a simple controller,
independent of nodal voltage changes. The realization was demonstrated by
simulation and experimental results on a scaled model of a transmission line.
The controller was compared to two other controllers under balanced and
unbalanced conditions, and demonstrated better performance, with shorter
settling times, no overshoot, and indifference to voltage unbalance. We
conclude that direct power control is an effective method that can be used with
UPFC. It is readily adaptable to other converter types than the three-level
converter demonstrated in this paper.
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[5]
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