Nonisolated High Step-Up DC-DC Converters Adopting Switched-Capacitor Cell

The mass usage of traditional fossil energy has adversely affected the environment on a global scale, such as environmental pollution and greenhouse effect. Meanwhile, there has been a growing demand for energy with the development of society. Since traditional fossil energy is not renewable, it is faced with the problem of energy shortage. Solar energy and hydrogen energy are promising, and photovoltaic (PV) and fuel cell power generation as the utilization method of the two new energy types have been applied on a large scale. In a single-phase system with a two-stage structure, if the line voltage is 220 V, the bus voltage of the grid-connected inverter needs to be as high as 380 V. However, the output voltages of PV and fuel cells are generally ranged from 25 to 45 V, which are much lower than the bus voltage. Thus, a dc–dc converter with a high voltage gain is needed to boost the outputs of PV and fuel cells. By increasing the turns ratio of the transformer in isolated converters, a high voltage gain can be obtained. However, a too large turns ratio will lead to a large leakage inductor. As a result, the voltage stress of the switch will be increased, whereas the efficiency of the converter is degraded. Existing system A boost converter (step-up converter) is a DC-to-DC power converter with an output voltage greater than its input voltage. It is a Do Your Projects With Domain Experts... Copyright © 2015 LeMeniz Infotech. All rights reserved Page number 2 LeMeniz Infotech 36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue, Pondicherry-605 005. Call: 0413-4205444, +91 9566355386, 99625 88976. Web : www.lemenizinfotech.com / www.ieeemaster.com Mail : [email protected] class of switched-mode power supply (SMPS) containing at least two semiconductors (a diode and a transistor) and at least one energy storage element, a capacitor, inductor, or the two in combination. Filters made of capacitors (sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple. Proposed system The voltage gain of the SC converter is high, but the output voltage is not regulated. The output regulation of the nonisolated switchingmode dc–dc converter is excellent, but the voltage gain cannot be too high for achieving high efficiency. This paper proposes a combination method of the SC converter and the switching-mode dc–dc converter. The basic approach is introducing multiple capacitors into the switchingmode dc–dc converters. When the switch is off, the energy released from the inductor is used to charge the capacitors in parallel. When the switch is on, the capacitors are connected in series to supply the load. Thus, the voltage gain is increased, and the duty cycle is decreased, leading to small ripple current and turnoff current of the switch, and high efficiency can be expected. Meanwhile, the voltages of the capacitors are well regulated, thus achieving a tightly regulated output voltage. In addition, the new converters proposed in this paper can be infinitely extended when an enormous voltage gain is needed. Do Your Projects With Domain Experts... Copyright © 2015 LeMeniz Infotech. All rights reserved Page number 3 LeMeniz Infotech 36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue, Pondicherry-605 005. Call: 0413-4205444, +91 9566355386, 99625 88976. Web : www.lemenizinfotech.com / www.ieeemaster.com Mail : [email protected] Advantages  Voltage gain is increased.  High efficiency. Applications  PV and fuel cells. Do Your Projects With Domain Experts... Copyright © 2015 LeMeniz Infotech. All rights reserved Page number 4 LeMeniz Infotech 36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue, Pondicherry-605 005. Call: 0413-4205444, +91 9566355386, 99625 88976. Web : www.lemenizinfotech.com / www.ieeemaster.com Mail : [email protected]