A small inductor is added to the auxiliary power delivery path, and diodes are replaced by active switches for bidirectional power flow control, as shown in the modified SEPIC topology in Fig. However, these converters still possess hard-switching properties, and diodes particularly suffer from severe reverse recovery problem.Ī new non-isolated bidirectional soft switching SEPIC/ZETA converter with reduced ripple currents is proposed to overcome these hard-switching problems. Inductor ripple currents and switching voltages of the main switch and diode can be reduced by shortening the duration of the original SEPIC or ZETA operation while extending the duration of the direct power link operation.
![operating principle of isolated cuk converter operating principle of isolated cuk converter](https://www.scientific.net/AMR.354-355.1400/preview.gif)
The converters consist of the original SEPIC or ZETA components in addition to an auxiliary diode and switch to form a new direct power delivery path between input and output. Without using any interleaved techniques, unidirectional SEPIC and ZETA converters featuring reduced ripple currents have been proposed in. Control reliability may also deteriorate with increased interleaving phases. These converters can enhance circuit performance but may increase overall circuit system complexity. Multiphase interleaved converters are often adopted to decrease voltage ripple and filter size by reducing the inductor current ripple components. The literature has reported on several non-isolated bidirectional DC–DC converters, such as bidirectional boost/buck-derived -, Cuk, SEPIC/ZETA, multilevel, , and coupled-inductor type converters. Non-isolated converters are simpler and more efficient than isolated converters and are thus preferred for use when galvanic isolation is unnecessary. These desirable features increased the use of bidirectional DC–DC converters in battery chargers/dischargers, fuel cell hybrid power systems, DC uninterruptible power supplies, and energy regenerative systems in automotive applications. Therefore, the weight, volume, and cost of the overall system can be reduced by simplifying circuit composition.
![operating principle of isolated cuk converter operating principle of isolated cuk converter](https://static-01.hindawi.com/articles/ape/volume-2012/730473/figures/730473.fig.003b.jpg)
![operating principle of isolated cuk converter operating principle of isolated cuk converter](https://d3i71xaburhd42.cloudfront.net/4220802879b00ea3a943c1cf5e0e6ef2a9c58b6e/5-Figure9-1.png)
Bidirectional DC–DC converters can manipulate bilateral power flow between two DC sources by using only a single-circuit structure.