ABSTRACT:
Photovoltaic
(PV) generation systems are widely employed in transformer less inverters, in
order to achieve the benefits of high efficiency and low cost. Safety
requirements of leakage currents are met by proposing the various transformers
less inverter topologies. In this paper, three transformer less inverter
topologies are illustrated such as a family of H6 transformer less inverter
topologies with low leakage currents is proposed, and the intrinsic
relationship between H5 topology, highly efficient and reliable inverter
concept (HERIC) topology. The proposed H6 topology has been discussed as well.
For a detailed analysis with operation modes and modulation strategy one of the
proposed H6 inverter topologies is taken as an example. Comparison among the HERIC,
the H5, and the proposed H6 topologies is been done for the power device costs
and power losses. For evaluating their performances in terms of power
efficiency and leakage currents characteristics, a universal prototype is built
for these three topologies mentioned. Simulation results show that the proposed
HERIC topology and the H6 topology achieve similar performance in leakage
currents, which is slightly worse than that of the H5 topology, but it features
higher efficiency than that of H5 topology.
KEYWORDS:
1.
Common-mode
voltage
2.
Grid-tied inverter
3.
Leakage current
4.
Photovoltaic (PV) generation system
5.
Transformerless inverter
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1. Leakage current path for
transformerless PV inverters
EXPECTED SIMULATION RESULTS:
Fig. 2. CM voltage and leakage current
in H6 topology. (a) CM voltage. (b) Leakage current.
Fig. 3. Drain–source voltages in H6
topology. (a) Voltage stress on S5 and S6 . (b) Detailed
waveforms.
Fig. 4. DM characteristic of H6
topology.
Fig.
5. Efficiency comparison of H5, HERIC and H6 topologies.
CONCLUSION:
In
this paper, based on the H5
topology, a new current path is formed by inserting a power device between the
terminals of PV array and the midpoint of one of bridge legs. As a result, a
family of single-phase transformerless full-bridge H6 inverter topologies with
low leakage currents is derived. The proposed H6 topologies have the following
advantages and evaluated by simulation
results:
1)
The conversion efficiency of the novel H6 topology is better than that of the
H5 topology, and its thermal stress distribution is better than that of the H5
topology;
2)
The leakage current is almost the same as HERIC topology, and meets the safety
standard;
3)
The excellent DM performance is achieved like the isolated full-bridge inverter
with uniploar SPWM. Therefore, the proposed H6 topologies are good solutions
for the single phase transformerless PV grid-tied inverters.
REFERENCES:
[1] S. B. Kjaer, J. K. Pederson, and F.
Blaabjerg, “A review of single-phase grid-connected inverters for photovoltaic
modules,” IEEE Trans. Ind. Appl., vol. 41, no. 5, pp. 1292–1306,
Sep/Oct. 2005.
[2]
F. Blaabjerg, Z. Chen, and S. B. Kjaer, “Power electronics as efficient interface
in dispersed power generation systems,” IEEE Trans. Power Electron.,
vol. 19, no. 5, pp. 1184–1194, Sep. 2004.
[3]
B. Sahan, A. N. Vergara, N. Henze, A. Engler, and P. Zacharias, “A single stage
PVmodule integrated converter based on a low-power current source inverter,” IEEE
Trans. Ind. Electron., vol. 55, no. 7, pp. 2602–2609, Jul.2008.
[4]
M. Calais, J. Myrzik, T. Spooner, and V. G. Agelidis, “Inverters for single phase
grid connected photovoltaic systems—An overview,” in Proc. IEEE PESC,
2002, vol. 2, pp. 1995–2000.
[5]
F. Blaabjerg, Z. Chen, and S. B. Kjaer, “Power electronics as efficient interface
in dispersed power generation systems,” IEEE Trans. Power Electron.,
vol. 19, no. 5, pp. 1184–1194, Sep. 2004.
