ABSTRACT

Droop control has commonly been used with distributed generators
for relating their terminal parameters with power generation. The generators
have also been assumed to have enough capacities for supplying the required
power. This is however not always true, especially with renewable sources
with no or insufficient storage for cushioning climatic changes. In addition,
most droop-controlled literatures have assumed a single dc-ac inverter with
its input dc source fixed. Front-end dc-dc converter added to a two-stage
photovoltaic (PV) system has therefore usually been ignored. To address these
unresolved issues, an improved droop scheme for a two-stage PV system has
been developed in the paper. The Proposed scheme uses the STATCOM
control structure in both grid-connected and islanded modes, which together
with properly tuned synchronizers, and mitigates the harmonics, by providing
Reactive power and Load current Subsequently the proposed scheme adapts
well with internal PV and external grid fluctuations, and is hence more
precise with its tracking, as compared with the traditional droop scheme.
Simulation and experimental results are obtained using MATLAB Simulink.
Keywords: Droop Control, Photovoltaic, STATCOM.
References
[1] M. Pereira, D. Limon, D. Munoz de la Pena, L. Valverde, and T. Alamo, “Periodic economic control of a nonisolatedmicrogrid,” IEEE Trans. Ind.
Electron., vol. 62, no. 8, pp. 5247–5255, Aug. 2015.
[2] Q. N. Trinh, and H. H. Lee, “An enhanced grid current compensator for grid-connected distributed generation under nonlinear loads and grid voltage
distortions,” IEEE Trans. Ind. Electron., vol. 61, no. 12, pp. 6528–6537, Dec. 2014.
[3] S. D. Reddy, M. P. Selvan, and S. Moorthi, “Design, operation, and control of S3 inverter for single-phase microgrid applications,” IEEE Trans. Ind.
Electron., vol. 62, no. 9, pp. 5569–5577, Sep. 2015.
[4] L. Hadjidemetriou, E. Kyriakides, and F. Blaabjerg, “A robust synchronization to enhance the power quality of renewable energy systems,” IEEE Trans.
Ind. Electron., vol. 62, no. 8, pp. 4858–4868, Aug. 2015.
[5] R. A. Mastromauro, M. Liserre, T. Kerekes, and A. Dell’Aquila, “A single-phase voltage-controlled grid-connected photovoltaic system with power
quality conditioner functionality,” IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 4436–4444, Nov. 2009.
[6] J. Kwon, S. Yoon, and S. Choi, “Indirect current control for seamless transfer of three-phase utility interactive inverters,” IEEE Trans. Power Electron.,
vol. 27, no. 2, pp. 773–781, Feb. 2012.
[7] S. Yoon, H. Oh, and S. Choi, “Controller design and implementation of Indirect current control based utility-interactive inverter system,” IEEE Trans.
Power Electron., vol. 28, no. 1, pp. 26–30, Jan. 2013..
[8] Z. Liu and J. J. Liu, “Indirect current control based seamless transfer of three-phase inverter in distributed generation,” IEEE Trans. Power Electron., vol.
29, no. 7, pp. 3368–3383, Jul. 2014.
[9] A. Micallef, M. Apap, C. Spiteri-Staines, J. M. Guerrero, and J. C. Vasquez, “Reactive power sharing and voltage harmonic distortion compensation of
droop controlled single phase islanded microgrids,” IEEE Trans. Smart Grid, vol. 5, no. 3, pp. 1149–1158, Nov. 2014.
[10] I. U. Nutkani, P. C. Loh, P. Wang, and F. Blaabjerg, “Autonomous droop scheme with reduced generation cost,” IEEE Trans. Ind. Electron., vol. 61, no.

12, pp. 6803–6811, Dec. 2014.