By Nitw Sudharshan reddy Pasham Mtech research scholar

1. A NOVEL HIGH STEP-UP DC-DC
CONVERTER
FOR A MICROGRID SYSTEM
Under the guidence of BY
CH.RAMULU SUDHARSHAN REDDY.P
ROLL NO:122538

2. CONTENTS
• INTRODUCTION
• CIRCUIT DIAGRAM
• OPERATING PRINCIPLE
• MODES OF OPERATION
• ANALYSIS
• CONCLUSION
• REFERENCES

3. INTRODUCTION
• The concept is composed of two capacitors, two
diodes, and one coupled inductor.
• Two capacitors are charged in parallel, and are
discharged in series by the coupled inductor.
• High step-up voltage gain can be achieved with an
appropriate duty ratio.
• The voltage stresses on the main switch and output
diode are reduced by a passive clamp circuit.
• DG systems are powered by microsources such as
fuel cells, photovoltaic (PV) systems, and batteries
• High step-up dc–dc converters are required to have
a large conversion ratio, high efficiency, and small
volume.

4. • The isolated converters such as forward, flyback, push-
pull, half-bridge, and full-bridge types can adjust the
turns ratio of the transformer to achieve high step-up
voltage gain.
• To improve the conversion efficiency and achieve high
stepup voltage gain, many topologies have been
proposed.
• The leakage-inductor energy of the coupled inductor is
recycled into the load during the switch-off period;
thus, the voltage spike on the main switch can be
limited.
• passive clamping circuit is needed to recycle the
leakage-inductor energy of the coupled inductor and to
clamp the voltage across the main switch.
• The reverse-recovery problems in the diodes are
alleviated, and thus, high efficiency can be achieved.

6. CIRCUIT DIAGRAM

7. OPERATING PRINCIPLE
• To simplify the circuit analysis, the following
conditions are assumed.
• 1) Capacitors C2 , C3 , and Co are large enough that
Vc 2 , Vc 3 ,and Vo are considered to be constant in
one switching period.
• 2) The power MOSFET and diodes are treated as
ideal, but the parasitic capacitor of the power
switch is considered.
• 3) The coupling coefficient of coupled inductor k is
equal to Lm/(Lm+Lk ) and the turns ratio of coupled
inductor n is equal to Ns /Np .

9. Continuous-Conduction Mode Operation

10. • Mode I [t0 , t1 ]: During this time interval, S is turned on.
Diodes D1 , D2 , and D3 are turned off, and Do is turned on.
• Mode II [t1 , t2 ]: During this time interval, S is still turned on.
Diodes D1 and Do are turned off, and D2 and D3 are turned
on.
• Mode III [t2 , t3 ]: During this time interval, S is turnedoff.
Diodes D1 and Do are turned off, and D2 and D3 are turned
on.
• Mode IV [t3 , t4 ]: During this time interval, S is turned off.
Diodes D1 , D2 , and D3 are turned on and Do is turned off.
• Mode V [t4 , t5 ]: During this time interval, S is turned off.
Diodes D1 and Do are turned on, and D2 and D3 are turned
off.
• Mode VI [t5 , t6 ]: During this time interval, S is still turned off.
Diodes D1 and Do are turned on, and D2 and D3 are turned
off.

11. Discontinuous-Conduction Mode Operation

13. • Mode I [t0 , t1 ]: During this time interval, S is turned
on. The part energy of dc source Vin transfers to
magnetizing inductor Lm. Thus, iLm is increased linerly.
• Mode II [t1 , t2 ]: During this time interval, S is turned
off. The energy of the magnetizing inductor Lm is
released to the capacitor C1 .
• Mode III [t2 , t3 ]: During this time interval, S remains
turned off. the energy stored in Lm is depleted, the
energy stored in Co is discharged to load R. This mode
ends when S is turned on at t = t3

14. CCM OPERATION
the duty cycle of the released energy can be expressed as

17. • Fig. 8. Voltage gain versus duty ratio of the proposed
converter, the converters in [35] and [36] at CCM
operation under n = 3 and k = 1.

18. DCM OPERATION
During the time of mode I, the switch S is turned on. Thus, the
following equations can be formulated

22. Fig. 11. Experiment results under full-load Po = 400 W.

23. Fig. 13. Experimental conversion efficiency.

24. CONCLUSION
• This paper proposed a novel, high efficiency,
and high stepup dc–dc converter. By using the
capacitor charged in parallel and discharged in
a series by the coupled inductor, high step-up
voltage gain and high efficiency are achieved.
• Experimental results confirm that high
efficiency and high step-up voltage gain can be
achieved. The efficiency is 96.8%.

25. REFERENCES
• [1] Y. Li and Y. W. Li, “Decoupled power control for an inverter based
low voltage microgrid in autonomous operation,” in Proc. IEEE Int.
Power Electron. Motion Control Conf. (IPEMC), 2009, pp. 2490–
2496.
• [2] Y. Li, D. M. Vilathgamuwa, and P. H. Loh, “Design, analysis, and
realtime testing of a controller for multibus microgrid system,” IEEE
Trans. Power Electron., vol. 19, no. 5, pp. 1195–1204, Jul. 2004.
• [3] C. L. Chen, Y. W, J. S. Lai, Y. S. Lee, and D. Martin, “Design of
parallel inverters for smooth mode transfer microgrid applications,”
IEEE Trans. Power Electron., vol. 25, no. 1, pp. 6–15, Jan. 2010.
• [4] A. Timbus, M. Liserre, R. Teodorescu, P. Rodriguez, and F.
Blaabjerg, “Evaluation of current controllers for distributed power
generation systems,” IEEE Trans. Power Electron., vol. 24, no. 3, pp.
654–664, Mar. 2009.

26. Thank You