ABSTRACT
This paper presents a new control strategy for real and
reactive power control of three-level multipulse voltage source converter based
High Voltage DC (HVDC) transmission system operating at Fundamental Frequency
Switching (FFS). A three-level voltage source converter replaces the conventional two-level
VSC and it is designed for the real and reactive power control is all four
quadrants operation. A new control method is developed for achieving the
reactive power control by varying the pulse width and by keeping the dc link
voltage constant. The steady state and dynamic performances of HVDC system interconnecting
two different frequencies network are demonstrated for active and reactive
powers control. Total numbers of transformers used in the system are reduced in
comparison to two level VSCs. The performance of the HVDC system is also
improved in terms of reduced harmonics level even at fundamental frequency
switching.
KEYWORDS
1.
HVDC
2.
Voltage Source
Converter
3.
Multilevel
4.
Multipulse
5.
Dead Angle (β)
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1 A three-level 24-Pulse voltage source converter based HVDC system
CONTROL SCHEME
Fig. 2 Control scheme of three-level VSC based HVDC system using dynamic dead angle (β) Control
EXPECTED SIMULATION
RESULTS
Fig.
3 Performance of rectifier station during simultaneous real and reactive power
control of three-level 24-pulse VSC based HVDC system
Fig. 4 Performance of inverter station during simultaneous real and reactive power control of three-level 24-pulse VSC based HVDC system
Fig. 5 Variation of angles (δ) and (β) values of three-level 24-pulse VSC based HVDC system during simultaneous real and reactive power control
CONCLUSION
A
new control method for three-level 24-pulse voltage source converter configuration
has been designed for HVDC system. The performance of this 24-pulse VSC based
HVDC system using the control method has been demonstrated in active power
control in bidirectional, independent control of the reactive power and power quality
improvement. A new dynamic dead angle (β) control has been introduced for
three-level voltage source converter operating at fundamental frequency
switching. In this control the HVDC system operation is successfully
demonstrated and also an analysis of (β) value for various reactive power
requirement and harmonic performance has been carried out in detail. Therefore,
the selection of converter operation region is more flexible according to the requirement
of the reactive power and power quality.
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