Power Decoupling Method of DC to Single-phase AC Converter using Flying Capacitor DC/DC Converter with Boundary Current Mode

Abstract

In this paper, a flying capacitor DC/DC converter with the active power decoupling capability utilizing small inductor and capacitor is introduced. The single-phase AC power converters are widely employed such as the Photovoltaic (PV) generation systems. Typically, a bulky electrolytic capacitor is required as the energy buffer for the compensation of the double-line frequency power ripple in these applications. However, the drawback of the electrolytic capacitor is often mentioned such as the large volume, and short life-time due to the high environmental temperature. On the other hand, an active power decoupling method achieves the power ripple compensation with small firm or ceramic capacitor. As the one of the active power decoupling approach, the power decoupling control method for the flying capacitor DC/DC converter has been proposed. However, this control method is mentioned under the Continuous Current Mode (CCM) condition. Therefore, large inductor is necessary to limit the current ripple within CCM. The active power decoupling control method of the flying capacitor DC/DC converter with the Boundary Current Mode (BCM) is proposed in order to minimize the inductor in this paper. The validity of the proposed power decoupling control is confirmed by the experiment with 1-kW prototype circuit. As the experimental result, the DC-link voltage fluctuation due to the double-line frequency power ripple is reduced by 85.6% owing to the proposed control.