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In this paper, a highly efficient isolated resonant converter with a novel modulation method is proposed for delivering power from photovoltaic (PV) modules to the dc microgrid. The proposed modulation method allows the converter to boost low input voltages and regulate a wide input voltage range. The converter design is based on a series resonant converter (SRC) that operates at the resonant frequency to achieve highest efficiency under nominal input voltage condition. Under shadowed or low irradiance conditions of PV panels, the converter will operate with the proposed “double-pulse duty cycle” modulation method to step up the voltage for the dc microgrid connection. With the proposed modulation method, the output switches serve for both synchronous rectification and voltage boost function. This method enables a higher voltage boost ratio than the SRC without adding additional switches while operating at the resonant frequency. A 300-W hardware prototype with gallium-nitride devices is built to verify the performance of the proposed converter and modulation method. The converter achieved a peak efficiency of 98.9% and a California Energy Commission weighted efficiency of 98.7% under nominal input voltage condition. [ABSTRACT FROM AUTHOR]