Abstract: Embodiments of the present disclosure provide a power conversion device, an electric vehicle charging system, and a method of controlling the power conversion device. The power conversion device includes a first power converter and a second power converter; a resonant converter coupled between the first power converter and the second power converter; and a controller. The controller being configured to control the first power converter to perform conversion between an AC voltage or a first DC voltage and a second DC voltage. The controller being configured to control the resonant converter to operate at a predetermined resonant frequency to perform conversion between the second DC voltage and a third DC voltage. The controller being configured to control, based on the voltage information, the second power converter to perform conversion between the third DC voltage and a fourth DC voltage.