Integration and Operation of a
Single-Phase
Bidirectional Inverter With Two
Buck/Boost MPPTs
for DC-Distribution Applications
ABSTRACT:
This study is focused on integration and operation
of a single-phase bidirectional inverter with two buck/boost maximum power
point trackers (MPPTs) for dc-distribution applications. In a dc-distribution
system, a bidirectional inverter is required to control the power flow between
dc bus and ac grid, and to regulate the dc bus to a certain range of
voltages.Adroop regulation mechanism according to the inverter inductor current
levels to reduce capacitor size, balance power flow, and accommodate load
variation is proposed. Since the photovoltaic (PV) array voltage can vary from 0
to 600 V, especially with thin-film PV panels, the MPPT topology is formed with
buck and boost converters to operate at the dc-bus voltage around 380 V,
reducing the voltage stress of its followed inverter. Additionally, the controller
can online check the input configuration of the two MPPTs, equally distribute
the PV-array output current to the two MPPTs in parallel operation, and switch control
laws to smooth out mode transition. A comparison between the conventional boost
MPPT and the proposed buck/boost MPPT integrated with a PV inverter is also
presented. Experimental results obtained from a 5-kW system have verified the
discussion and feasibility.
KEYWORDS:
1.
Bidirectional
inverter
2.
Buck/Boost Maximum
Power Point Trackers (MPPTs)
3.
DC-distribution
applications.
SOFTWARE: MATLAB/SIMULINK
BLOCK
DIAGRAM:
Fig. Configuration of the
studied PV inverter system with the buck/boost MPPTs.
CONCLUSION:
In
this paper, a single-phase bidirectional inverter with two buck/boost MPPTs has
been designed and implemented. The inverter controls the power flow between dc
bus and ac grid, and regulates the dc bus to a certain range of voltages. A
droop regulation mechanism according to the inductor current levels has been
proposed to balance the power flow and accommodate load variation. Since the
PV-array voltage can vary from 0 to 600 V, the MPPT topology is formed with
buck and boost converters to operate at the dc-bus voltage around 380 V,
reducing the voltage stress of its followed inverter. Additionally, the
controller can online check the input configuration of the MPPTs, equally
distribute the PV-array output current to the two MPPTs in parallel operation,
and switch control laws to smooth out mode transition. Integration and
operation of the overall inverter system have been discussed in detail, which
contributes to dc distribution applications significantly. Experimental results
obtained from a 5-kW, single-phase bidirectional inverter with the two MPPTs
have verified the analysis and discussion.
REFERENCES:
[1]
J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galvan, R. C. P.
Guisado, Ma. A. M. Prats, J. I. Leon, and N. Moreno-Alfonso, “Power-electronic
systems for the grid integration of renewable energy sources: a survey,” IEEE
Trans. Ind. Electron., vol. 53, no. 4, pp. 1002– 1016, Aug. 2006.
[2]
L. N. Khanh, J.-J. Seo, T.-S. Kim, and D.-J. Won, “Power-management strategies
for a grid-connected PV-FC hybrid system,” IEEE Trans. Power Deliv.,
vol. 25, no. 3, pp. 1874–1882, Jul. 2010.
[3]
Y. K. Tan and S. K. Panda, “Optimized wind energy harvesting system using
resistance emulator and active rectifier for wireless sensor nodes,” IEEE
Trans. Power Electron., vol. 26, no. 1, pp. 38–50, Jan. 2011.
[4]
J.-M. Kwon, K.-H. Nam, and B.-H. Kwon, “Photovoltaic power conditioning system
with line connection,” IEEE Trans. Ind. Electron., vol. 53, no. 4, pp.
1048–1054, Aug. 2006.
[5]
J. Selvaraj and N. A. Rahim, “Multilevel inverter for grid-connected PV system
employing digital PI controller,” IEEE Trans. Ind. Electron., vol. 56,
no. 1, pp. 149–158, Jan. 2009.
