ABSTRACT:
A grid tied photovoltaic (PV) power conversion
topology is presented in this study with a novel scheme of resynchronization to
the grid. This scheme serves the purpose of supplying continuous power to the
load along with feeding power to the grid. The control approach helps in
mitigation of harmonics and improving the power quality while extracting the optimum
power from the PV array. Depending on the availability of grid voltage, the
proposed configuration is controlled using three approaches, defined as grid
current control, Point of Common Coupling (PCC) voltage control and intentional
islanding with re-synchronisation. A simple proportional integral controller
manages the grid current, load voltage, battery current and DC Direct Current
(DC) link voltage within these modes. Moreover, a control scheme for quick and
smooth transitions among the modes is described. The robustness of the system
under erratic behaviour of solar insolation, load power and disturbances in grid
supply makes it a suitable choice for a residential application. The control,
design and simulation results are presented to demonstrate the satisfactory operation
of the proposed system.
SOFTWARE: MATLAB/SIMULINK
Fig. 1 Proposed system topology
Fig. 2 Performance
of the system under grid isolation
(a) GCC to PVC, (b) Harmonic
spectrum of grid current (ig), (c) Harmonic spectrum of load voltage (vL)
Fig. 3Performance of the system under grid
reconnection
(a) Mode change from PVC to IIRS, (b) Grid voltage (vg) vs. load
voltage (vL) during
intentional
islanding
Fig. 4 Performance of the system for insolation
change from 1000 W/m2
to
500/m2
CONCLUSION:
The
proposed scheme has combined the solar PV power generating unit to single-phase
grid with a unique feature of resynchronization of grid to the system after
overcoming the grid failures. The ability of the system to generate maximum
power for varying insolation, feeding active power to the grid as well as load and
store/extract power to/from the battery has been validated by the dynamic performance.
This helps in increasing the efficiency of the system. The scheme has utilised
minimum number of switches resulting in lower switching losses. The VSC has the
ability to diminish the switching harmonics in grid current and load voltages resulting
in <5% THD as demanded by the IEEE 519 standard. The system has ability to
re-synchronise with the grid within five cycles of grid voltage for any phase
difference. This helps in achieving the fast time response of the system, thus
making it a suitable choice for residential applications. The obtained results
have authenticated the robustness and feasibility of the proposed system under
various disturbances.
REFERENCES:
[1]
Zheng, H., Li, S., Bao, K., et al.: ‘Comparative study of maximum power point
tracking control strategies for solar PV systems’. IEEE Conf. on Transmission,
Distribution and Exposition, May 2012, pp. 1–8
[2]
Weihang, Y., Jianhui, W., Wenzhong, G., et al.: ‘A MPPT algorithm based
on extremum seeking with variable gain for microinverters in microgrid’. IEEE Conf.
on Control (CCC), July 2015, pp. 7939–7944
[3]
Zhang, Q., Hu, C., Chen, L., et al.: ‘A center point iteration MPPT
method with application on the frequency-modulated LLC microinverter’, IEEE Trans.
Power Electron., 2014, 29, (3), pp. 1262–1274
[4]
Li, Q., Wolfs, P.: ‘A review of the single phase photovoltaic module integrated
converter topologies with three different DC link configurations’, IEEE
Trans. Power Electron., 2008, 23, (3), pp. 1320–1333
[5]
Gloire, N., Lei, D., Xiaozhong, L., et al.: ‘Single phase grid-connected
PV inverter applying a boost coupled inductor’. IEEE Conf. on Transportation Electrification (ITEC Asia-Pacific), August–September
2014, pp. 1–5
