ABSTRACT:
In this paper, the unbalanced current in the 12- pulse
phase control AC/DC converters was studied. The 12- pulse A-Y type AClDC
converter will keep a balanced voltage with 30" phase shifted at the low
coupling coefficient condition. But an unbalanced current will be obtained in
the 12-pulse autotransformer phase shift AClDC converter at the low coupling
coefficient condition. The theoretical phasor analysis of the unbalanced
current was presented and a feedback controller was designed to overcome this
problem. Finally, a 3 kW 12-pulse autotransformer phase shifted AClDC converter
was implemented to demonstrate the theoretical analysis.
KEYWORDS:
1.
12 Pulse AClDC
Converter
2.
Phase
Controller
3. Autotransformer
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1. Conventional 12-pulse AClDC converter.
(a) A-Y isolated transformer.
(b) Autotransformer phase shifted.
Fig. 2. 12-pulse phase control A-Y connected AC/DC
converter.
Fig. 3. I;!-pulse phase control autotransformer connected
AC/DC
converter.
EXPECTED SIMULATION RESULTS:
Fig. 4 The output current io, and io, of
12-pulse phase control A-Y
typ:
transformer ACDC converter with K=0.96 and
a = 30"
Fig 5 The output current io, and io, of
12-pulse autotransformer
phase shift ACDC converter with K=0.96 and a =
30".
Fig. 6 The output current of 12-pulse
autotransformer connected
AC/DC converter with the controller
Fig.
7 Experimental results for a resistive load without controller
Fig.
8 Experimental results for a resistive load with controller
CONCLUSION:
In
this paper, the 12-pulse phase control ACDC converters with A-Y type and
autotransformer type are analyzed and studied. The theoretical
analysis is presented and the computer simulation results are
performed. The 12- pulse A-Y type ACDC converter can function well under any
firing condition. However, a serious unbalanced circulation current exists in
the autotransformer connected ACDC converter at the non-unity coupling
coefficient conditions. Finally, a 3 kW 12-pulse
autotransformer phase controlled ACDC converter was implemented to demonstrate
the theoretical analysis.
REFERENCES:
1. S. Choi, A. Jouanne, P.
Enjeti and 1. Pitel, “New Polyphase Transformer Arrangements with
Reduced kVA Capacities for Harmonic Current Reduction in Rectifier Type Utility
Interface,“ IEEE PESC, 1995.
2. S. Choi, P. N. Enjeti, H. Lee
and I. J. Pitel, “A New Active Interphase Reactor for 12-Pulse Rectifiers
Provides Clean Power Utility Interface,” IEEE IAS, pp.2468-2474, 1995.
3. G. Oliver, G. E. April, E. Ngandui
and C. Guimaraes, “Novel Transformer Connection to Improve Current Sharing on High
Current DC Rectifier,” IEEE IAS, pp.986-962, 1993.
4. S. Miyairi, etc.al, “New
Method for Reducing Harmonic Involved in Input and Output of Rectifier with
Interphase Transformer,” IEEE Trans. On Industry Applications, Vol. IA-22,
No.5, pp.790- 797, SepIOct, 1986.
5. A .R. Prasad, P. D. Ziogas, and S.
Manias, “An Active Power Factor Correction Technique for Three-phase
Diode Rectifier,” IEEE Trans. on Power Electronics, Vo1.6, No.1,
pp.83-92, 1991
