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Tuesday 29 May 2018

A Fuzzy Logic Controller for Autonomous Operation of a Voltage Source Converter-Based Distributed Generation System



ABSTRACT
KEYWORDS
1.     Autonomous operation
2.     Distributed generation (DG)
3.      Fuzzy logic controller (FLC)
4.      Voltage source converter
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:


Fig. 1. Single line diagram of the DG system
 EXPECTED SIMULATION RESULTS


Fig. 2. Responses for transition from grid-connected to islanded mode. (a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC.




Fig. 3 Responses for the change of the load resistance R from 76 to 152 Ω(a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC.


Fig. 4. Responses for the change of the load resistance R from 76 to 304 Ω(a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC.


Fig. 5. Responses for change of the load inductance L from 111.9 to 222 mH. (a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC.

Fig. 6. Responses for connecting a nonlinear load in parallel to the load. (a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC.


Fig. 7. Responses for connecting a three-phase induction motor in parallel to the load. (a) Vd. (b) Vq. (c) Load voltage (rms). (d) Load real power. (e) Load reactive power. (f) Three-phase load voltage using FLC. (g) Three-phase converter currents using FLC. (h) Motor speed. (i) Developed torque.

CONCLUSION
This paper has presented the application of a FLC to the autonomous operation of an electronically coupled DG unit and its local load with the purpose of achieving better transient responses despite the load variability and uncertainty. A detailed dynamic model of the system under study and the control strategy are investigated. The system performance using the FLC is evaluated through the following case studies:
1) transition from the grid-connected mode to the islanded mode;
2) change of the RLC load parameters;
3) switching of a nonlinear load;
4) motor energization.
The simulation results have shown that the system performance using the proposed FLC has a better damped response and a faster transient behavior in comparison with that obtained using the conventional PI controller. It can be concluded that the FLC guarantees a robust stability and efficient performance irrespective of the load uncertainty.
REFERENCES
[1] N. Hatziargyriou, H. Asano, R. Iravani, and C. Marnay, “Microgrids,” IEEE Power Energy Mag., vol. 5, no. 4, pp. 78–94, Jul./Aug. 2007.
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[3] F. Katiraei, M. R. Iravani, and P.W. Lehn, “Micro-grid autonomous operation during and subsequent to islanding process,” IEEE Trans. Power Del., vol. 20, no. 1, pp. 248–257, Jan. 2005.
[4] P. Piagi and R. H. Lasseter, “Autonomous control of microgrids,” in Proc. IEEE Power Eng. Soc. (PES) Gen. Meeting, Montreal, QC, Canada, Jun. 2006, Paper no. 1708993.
[5] H. Nikkhajoei and R. H. Lasseter, “Distributed generation interface to the CERTS microgrid,” IEEE Trans. Power Del., vol. 24, no. 3, pp. 1598–1608, Jul. 2009.