A study of a floating-capacitor (FC) multilevel-converter-based VSC transmission system operating under unbalanced AC conditions is presented. The control strategy is based on the use of two controllers, i.e. a main controller, which is implemented in the synchronous d–q frame without involving positive and negative sequence decomposition, and an auxiliary controller, which is implemented in the negative sequence d–q frame with the negative sequence current extracted. Automatic power balancing during AC fault is achieved without communication between the two converters by automatic power modulation on the detection of abnormal DC voltages. The impact of unbalanced floating capacitor voltages of the FC converter on power devices is described. A software-based method, which adds square waves whose amplitudes vary with the capacitor voltage errors to the nominal modulation signals for fast capacitor voltage balancing during faults, is proposed. Simulations on a 300 kV DC, 300 MW VSC transmission system based on a four-level FC converter show good performance of the proposed control strategy during unbalanced conditions caused by single-phase to ground fault.
References
-
-
1)
-
Chen, S., Joos, G., Moran, L.T.: `Dynamic performance of PWM STATCOMs operating under unbalanced and fault conditions in distribution systems', Proc. 2001 IEEE PES Winter Meeting, 2001.
-
2)
-
Lavieville, J.P., Bethoux, O., Carrere, P., Meynard, T.A.: `Electronic circuit for converting electrical energy', 5726870, March 1998, US Patent.
-
3)
-
Mendalek, N., Al-Haddad, K., Dessaint, L.A., Fnaiech, F.: `Nonlinear control strategy applied to a shunt active power filter', Proc. 2001 IEEE Power Electronics Specialist Conf..
-
4)
-
B.R. Andersen ,
L. Xu ,
P. Horton ,
P. Cartwright
.
Topologies for VSC transmission.
Power Eng. J.
,
3 ,
142 -
150
-
5)
-
T. A. Meynard ,
H. Foch
.
Imbricated cells multi-level voltage-source inverters for high voltage applications.
EPE J.
,
2 ,
99 -
106
-
6)
-
C. Hochgraf ,
R.H. Lasseter
.
Statcom controls for operation with unbalanced voltages.
IEEE Trans. Power Deliv.
,
2 ,
538 -
544
-
7)
-
L. Xu ,
B.R. Andersen ,
P. Cartwright
.
Control of VSC transmission systems under unbalanced network conditions.
IEEE Trans. Power Deliv.
,
1 ,
427 -
434
-
8)
-
C.B. Jacobina ,
M.B. Correa ,
R.F. Pinheiro ,
E.R.C. da Silva ,
A.M.N. Lima
.
Modeling and control of unbalanced three-phase systems containing PWM converters.
IEEE Trans. Ind. Appl.
,
6 ,
1807 -
1816
-
9)
-
Yu, Q., Round, S.D., Norum, L. E., Undeland, T.M.: `Dynamic control of a unified power flow controller', Proc. 1996 IEEE Power Electronics Specialist Conf., , p. 508–514.
-
10)
-
L. Xu ,
V.G. Agelidis
.
Active capacitor voltage control of flying capacitor multilevel converters.
IEE Proc., Electr. Power Appl.
,
3 ,
313 -
320
-
11)
-
T. A. Meynard ,
H. Foch
.
Multi-level choppers for high voltage applications.
EPE J.
,
1 ,
45 -
50
-
12)
-
P. Rioual ,
H. Pouliquen ,
J.-P. Louis
.
Regulation of a PWM rectifier in the unbalanced network state using a generalized model.
IEEE Trans. Power Electron.
,
495 -
502
-
13)
-
Thomas, J. L., Poullain, S., Benchaib, A.: `Analysis of a robust DC-bus voltage control system for a VSC transmission scheme', Proc. 7th AC/DC Transmission Conf., November 2001.
-
14)
-
L. Xu ,
V.G. Agelidis
.
A flying capacitor multilevel PWM converter based UPFC.
IEE Proc., Electric. Power Appl.
,
4 ,
304 -
310
-
15)
-
C. C Shauder ,
H. Mehta
.
Vector analysis and control of advanced static VAR compensator.
IEE Proc., Electr. Power Appl.
,
4 ,
299 -
306
-
16)
-
Y. Liang ,
C.O. Nwankpa
.
A power-line conditioner based on flying-capacitor multilevel voltage-source converter with phase-shift SPWM.
IEEE Trans. Ind. Appl.
,
965 -
971
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