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This paper presents a new multiple-input soft-switching DC−DC Ćuk converter for clean and renewable energy sources. The proposed converter can buck and boost the different voltages of renewable energy sources to produce a constant DC output voltage in a DC microgrid. In the proposed converter, edge-resonant soft-switching modules are used to perform better than the conventional multiple-input Ćuk converter. All switches in the edge-resonant soft-switching modules can realize zero-current switching turnon and zero-voltage switching turn-off. By using these modules, the proposed converter can achieve lower current stress of the switches, wider soft-switching range, and higher power efficiency than the conventional multiple-input Ćuk converter. These advantages are achieved in the edge-resonant modules, which optimize soft-switching states and costs. In addition, the soft-switching states can be easily achieved because the edge-resonant soft-switching modules have a wide soft-switching range. Furthermore, the proposed converter can independently transfer the generated power from renewable energy sources to the DC microgrid. In this article, the operation principles and performance of the proposed converter are discussed in detail. The theoretical analysis is validated by experimental results obtained from a laboratoryscale prototype and full-scale real-time hardware-in-the-loop experiments.INDEX TERMS DC−DC power converters, Edge-resonant, Multiple-input Ćuk converter, Zero-current switching, Zero-voltage switching.

This study proposes a grid-connected inverter for photovoltaic (PV)-powered electric vehicle (EV) charging stations. The significant function of the proposed inverter is to enhance the stability of a microgrid. The proposed inverter can stabilize its grid voltage and frequency by supplying or absorbing active or reactive power to or from a microgrid using EVs and PV generation. Moreover, the proposed inverter can automatically detect an abnormal condition of the grid, such as a blackout, and operate in the islanding mode, which can provide continuous power to local loads using EV vehicle-to-grid service and PV generation. These inverter functions can satisfy the requirements of the grid codes, such as IEEE Standard 1547–2018 and UL 1741 SA. In addition, the proposed inverter can not only enhance the microgrid stability but also charge EVs in an appropriate mode according to the condition of the PV array and EVs. The proposed inverter was verified through experimental results with four scenarios in a lab-scale testbed. These four scenarios include grid normal conditions, grid voltage fluctuations, grid frequency fluctuations, and a power blackout. The experimental results demonstrated that the proposed inverter could enhance the microgrid stability against grid abnormal conditions, fluctuations of grid frequency and voltage, and charge EVs in an appropriate mode.

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