Abstract
We designed and implemented a single-switch step-up DC-DC converter based on cascaded boost and Luo converters. The proposed converter demonstrated a quadratic voltage gain and a high efficiency, which makes it suitable for renewable energy applications, where a high voltage gain ratio is desired without imposing a high number of bulky items or employing a high duty cycle of the active switches. This converter benefits from the continuity of the input current waveform, which equips the maximum utilisation of renewable energy sources. While a transformer-less high voltage-gain was achieved, the voltage and current stresses of the power switch and diodes were kept low in comparison with the existing quadratic DC-DC converters. We analysed the converter in both continuous and discontinuous conduction modes. A non-ideal model of components was considered for power loss and efficiency calculations and comparisons. Finally, the simulation results were extracted with PLECS and validated with experiments on a 120 W prototype.
Highlights
The DC-DC topologies can be mainly divided into isolated and non-isolated designs.The turn ratio of the coils in the isolated topologies acts an essential role in the increase of the voltage gain, independent of the high value of the duty cycle
For the higher values of the duty cycle, the decreasing rates of the designed topology and quadratic boost converters were sharper than the Luo converter due to higher degree of their voltage gain
The gain of the proposed converter was more than the Luo and quadratic boost converters, and it caused a higher value of the inductor current in the proposed converter in comparison with the Luo and quadratic boost converters at the specified duty cycle
Summary
The DC-DC topologies can be mainly divided into isolated and non-isolated designs. The turn ratio of the coils in the isolated topologies acts an essential role in the increase of the voltage gain, independent of the high value of the duty cycle. The storage of the energy in the inductor during the first mode and the subsequent release of that energy to the load makes the 50 percent duty cycle the best choice Such a situation causes a pass-through rather than a step-up in the buck-boost converter [1,2,3]. By increasing the duty cycle and its approach to unity, higher orders of voltage gain can be achieved. To achieve higher values of the voltage gain, the duty-cycle has to approach unity, which can significantly decrease the efficiency due to the increase in the number of the components. The efficiency of the designed topology has achieved high values, and the operating point has become more than 90 percent Such design of the converter can be used for applications that need to step up the battery voltage (for example, 24 to 100 or 200 V, such as electric bikes). The continuous input current makes this design appropriate for renewable applications to provide a high and stable output voltage
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