1. At National Institute of Technology, Meghalaya, Shillong, India
International Conference on Energy, power and Environment (Towards Sustainable Growth) ICEPE 2015
At National Institute of Technology, Meghalaya, Shillong, India
12-13th June,2015
Topic of Presentation theoretical study on performance constraints of a dc-dc buck-boost converter
Presented By:
Mr. Barnam Jyoti Saharia

2. Presentation Outline:
Introduction: Maximum Power Point Tracking of Photovoltaic Power Generators
A Brief overview of DC-DC Buck-Boost Converter
Performance parameters considered in this study
DC-DC Buck-Boost Converter Analysis
Conclusion
Limitation and Scope for future works
References

3. Introduction At the heart of any MPPT there are three components:
1. A switched-mode DC-DC converter
2. A control circuit, and or along with
3. Tracking algorithm.
Fig 1: PV panel connected through DC-DC converter
with a direct coupled load

4. Fig 2: Location of Maximum power operating point of PV module connected to a resistive load

5. maximum power point tracking of photovoltaic power generators:
Fig 3: DC-DC converter interface for the operation of PV module at MPP

6. INTRODUCTION: DC-DC Buck-Boost Converter
(1)
(2)
(3)
(4)
Fig 4: DC-DC Buck-Boost Converter Operation

7. PERFORMANCE PARAMETERS CONSIDERED:
To analyze the behavior of the DC-DC BUCK-BOOST converter with change of duty ratio or duty cycle (D) five basic parameters have been considered, which have been found to be dependent on the duty ratio.
Output Voltage (Vo)
Input Current (Io)
Effective Input Impedance (Reff)
Minimum filter inductance (Lbmin)
Minimum filter capacitance (Cmin)
20V, 2A supplying a load of 20Ω. Switching frequency is 100 kHz. Output ripples are considered to be limited to 1%.

8. Table I: Performance parameters for the Buck-Boost Converters
DC-DC BUCK-BOOST CONVERTER ANALYSIS:
Table I: Performance parameters for the Buck-Boost Converters
Parameter
Buck-boost
Output Voltage (Vo)
Vd(-D)/(1-D)
Output Current (Io)
-Id (1-D)/D
Input Impedance (Reff)
RL (1-D) 2/D 2
Minimum filter inductance (Lbmin)
(1-D) 2 RL/2f
Minimum filter capacitance (Cmin)
VoD/(VrRLf)
These parameters have been derived considering that the converter is in CCM of operation and works under 100% efficiency [1,7].

9. DC-DC BUCK-BOOST CONVERTER ANALYSIS: Continued
Fig 5: The variation of Duty Ratio with switching period

10. DC-DC BUCK-BOOST CONVERTER ANALYSIS: Continued
Fig 6: Effect of variation of duty ratio on the Io and Vo

11. DC-DC BUCK-BOOST CONVERTER ANALYSIS: Continued
Fig 7: Effect of variation of Duty ratio on the effective input impedance of the Buck-Boost converter

12. DC-DC BUCK-BOOST CONVERTER ANALYSIS: Continued
Fig 8: Effect of variation of Duty ratio on the effective input impedance of the Buck-Boost converter

13. CONCLUSION:
The D decreases inversely with the increase in switching period.
Sensitivity – more for lower switching periods. Assumes constant values for higher switching periods.
Vo and Reff increases with the decrease of D
Io and Reff decrease with the increase of D
Voltage sensitivity decreases while current sensitivity increases as D > 0.5.

14. Limitation and scope for future works:
Analysis is carried out under the assumption that the converter operates under CCM and that the converter is lossless.
Future works may be carried out taking into consideration the effect of the discontinuous conduction mode(DCM) and switching losses.

15. References:
[1] M. Rashid, Power Electronics – circuits, devices and applications (3rd Edition, Pearson Education, 2004) [2] M.H. Taghvee, M.A.M. Radzi, S.M. Moosavain, H. Hizam, M.H. Marhaban, “ A current and future study on non-isolated DC-DC converters for photovoltaic applications”, Renewable and Sustainable Energy Reviews, Vol. 17 , 2013, pp [3] J. M. Enrique, E. Durán, M. Sidrach-de-Cardona, J.M. Andújar, M.A. Bohórquez and J.E. Carretero, "A new approach to obtain I-V and P-V curves of PV panels by using DC-DC converters," Proceedings of the 31st IEEE Photovoltaic Specialist Conference, PVSC 2005, Orlando, EEUU, [4] D.P. Hohm and M.E. Ropp, “Comparative Study of Maximum Power Point Tracking Algorithms”, Progress in Photovoltaics: Research and Applications. 2003; 11: pp [5] T. Esram T. and P.L. Chapman, “Comparison of photovoltaic array maximum power point tracking techniques,” IEEE Trans. Energy Conver. Vol . 22 (2) 2007, pp 439–449. [6] J.M. Enrique, et al , “Theoretical assesment of the maximum power point tracking efficiency of photovoltaic facilities with different converter topologies”, Solar Energy , Vol 81, 2007, pp [7] L. Umanand, Power Electronics Essentials and Applications (1st Edition, Wiley India, 2009)

16. Thank you

17. Queries?