IEEE Transactions on Power Electronics, 2015
ABSTRACT
This paper investigates a dynamic
voltage restorer (DVR) composed of two conventional three-phase inverters
series cascaded through an open-end winding (OEW) transformer, denominated here
DVR-OEW. The DVR-OEW operating with either equal or different dc-link voltages
are examined. The proposed topology aims to regulate the voltage at the load side
in the case of voltage sags/swells, distortion, or unbalance at the grid
voltage. A suitable control strategy is developed, including space-vector
analysis, level-shifted PWM (LSPWM) and its equivalent optimized single-carrier
PWM (SCPWM), as well as the operating principles and characteristics of the DVR.
Comparisons among the DVR-OEW and conventional configurations, including a
neutral-point clamped (NPC) converter based DVR, are furnished. The main
advantages of the DVROEW compared to the conventional topologies lie on: i)
reduced harmonic distortion, ii) reduced converter losses, and iii) reduced voltage
rating of the power switches. Simulated and experimental results are presented
to validate the theoretical studies.
SOFTWARE:
MATLAB/SIMULINK
BLOCK
DIAGRAM:
Fig.
1 Example of a typical application of DVR in
Medium-Voltage (MV) distribution system..
EXPECTED
SIMULATION RESULTS:
Fig. 2. System voltages for vca = vcb. (a) Grid
voltages (egj). (b) DVR voltages at the secondary side of the injection
transformers (vsj ). (c) Load voltages (vlj ). (d) Injected
voltage (vp1) for one phase at the primary side of injection
transformer.
Fig. 3. Pole voltages in one phase at inverters A (v1a0a)
and B (v1b0b), respectively. (a) OEW inverter operates
with alternatively leg of converter clamped in every half cycle. (b) OEW
inverter operates by clamping inverter A.
CONCLUSION
In this paper a dynamic voltage restorer (DVR) obtained by means
of the series connection of two three-phase inverters through an open-end
winding transformer was presented. Two equivalent implementations with either
level-shifted carrier PWM (LSPWM) or single-carrier PWM (SCPWM) strategy approaches
were presented. The main advantages of the proposed topology, compared to
conventional configurations with three legs (see Fig. 2(a)), six-leg (see Fig.
2(b)) and NPC (see Fig. 2(c)) lies on: (i) reduced harmonic distortion
(operating at the same switching frequency), (ii) reduced converter
losses (operating with the same harmonic distortion), (iii) reduced
converter losses (with the same switching frequency), see Table III and (iv)
reduced voltage rating of the power switches employed in the DVR. The operations
with different dc-link voltages have been investigated and it is shown that
much lower harmonic distortion can be obtained. The proposed DVR system is
suitable for medium voltage application. Simulated and experimental results
were also presented.
REFERENCES
[1]
Goharrizi, S. Hosseini, M.
Sabahi, and G. Gharehpetian, “Threephase HFL-DVR with independently controlled
phases,” Power Electronics, IEEE Transactions on, vol. 27, pp.
1706–1718, April 2012.
[2]
S. Biswas, S. Goswami, and
A. Chatterjee, “Optimal distributed generation placement in shunt capacitor compensated
distribution systems considering voltage sag and harmonics distortions,” Generation,
Transmission Distribution, IET, vol. 8, pp. 783–797, May 2014.
[3]
C. N. M. Ho and H. S. H.
Chung, “Implementation and performance evaluation of a fast dynamic control
scheme for capacitor-supported interline DVR,” IEEE Trans. Power Electron.,
vol. 25, pp. 1975 –1988, Aug. 2010.
[4]
J. Rosas-Caro, F.
Mancilla-David, J. Ramirez-Arredondo, and A. Bakir, “Two-switch three-phase
ac-link dynamic voltage restorer,” Power Electronics, IET, vol. 5, pp.
1754–1763, November 2012.
[5]
S. Subramanian and M.
Mishra, “Interphase ac-ac topology for voltage sag supporter,” Power
Electronics, IEEE Transactions on, vol. 25, pp. 514 –518, feb. 2010.
