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Isolated High Step-Up DC-DC Converter
Based on Quasi-Switched-Boost Network
Abstract:
In this paper, a new isolated high step-up DC-DC converter is proposed based on
the quasi-switched-boost network. The proposed converter has the following
features: 1) continuous input current; 2) reduced turn ratio of the isolated
transformer; 3) increased reliability, as it can operate in either short-circuit mode or
open-circuit mode without causing damage to the power converter; and 4)
unchanged primary and secondary voltage waveforms of the transformer, although
the shoot-through duty cycle is variable. Compared to the quasi-Z-source-based
isolated DC-DC converter, the proposed converter uses fewer passive components.
The operating principles, analysis, parameter design guideline, and comparison
with the quasi-Z-source-based isolated DC-DC converter are presented. A 450 W
prototype is built to test the proposed converter. The proposed converter is
applicable for distributed power generation applications where a varying low dc
input voltage is converted to a high stabilized dc output voltage with a galvanic
separation requirement.
Existing system:
A high step-up DC-DC converter is typically used to convert a low-voltage DC
energy source to that of a higher-voltage DC before connecting it to a DC-AC
inverter for grid-connected applications. Solar photovoltaics (PVs) and fuel cells
(FCs) are low-voltage DC energy sources used in power conditioning systems
(PCSs). To interlink PVs or FCs to 230-Vac single-phase or 3 x 400-Vac
residential loads, a two-stage DC-DC-AC grid-connected inverter is widely used
due to its simple control.
Proposed system:
A QSB-based isolated step-up DC-DC converter was proposed in this paper. The
proposed converter can operate in either short-circuit mode or open-circuit mode
without causing any damage to the power converter. In addition, the input
current of the proposed converter is continuous. Thus, the proposed converter can
reach the required reliability without the need for any additional components.
Because the VDR and shoot-through duty cycle are used to boost voltage, the turn
ratio of the isolated transformer is significantly reduced. Compared to the QZSbased isolated DC-DC converter, the proposed converter uses fewer passive
components. Therefore, the size, weight, and cost of the proposed converter are
reduced.
Circuit diagram:
Advantages:
Uses one less capacitor with a lower capacitance and one less inductor with a
higher inductance; lower current rating on both switches and diodes; higher boost
factor with the same parasitic effect; and higher efficiency.
Reference:
[1] C. T. Pan and C. M. Lai, “A high-efficiency high step-up converter with
low switch voltage stress for fuel-cell system applications,” IEEE Trans.
Ind. Electron., vol. 57, no. 6, pp. 1998–2006, Jun. 2010.
[2] Y. P. Siwakoti, P. C. Loh, F. Blaabjerg, S. J. Andreasen and G. E. Town,
"Y-source boost DC/DC converter for distributed generation," IEEE
Trans. Ind. Electron., vol. 62, no. 2, pp. 1059–1069, Feb. 2015.
[3] A. I. Bratcu, I. Munteanu, S. Bacha, D. Picault and B. Raison, "Cascaded
DC–DC converter photovoltaic systems: power optimization issues,"
IEEE Trans. Ind. Electron., vol. 58, no. 2, pp. 403-411, February 2011.
[4] G. Wu, X. Ruan and Z. Ye, "Nonisolated high step-up DC–DC converters
adopting switched-capacitor cell," IEEE Trans. Ind. Electron., vol. 62, no.
1, pp. 383-393, January 2015.