Floating Capacitor Integrated DAB for Single-Phase, Single-Stage PFC in Wireless Battery Charging Application

Abstract

In this article, a novel active power decoupling topology called Floating Capacitor Integrated Dual Active Bridge (FCI-DAB) for single-phase, single-stage AC-DC solutions is introduced. The main point of the circuit is an active energy buffer that compensates the power fluctuation at double the grid frequency. The power decoupling filter is composed by a floating capacitor and a full-bridge; and is connected to the high-frequency link of a resonant DAB $|$AC$|$-DC converter. Compared to state-of-the-art two-stage solutions, it dispenses with the bulky electrolytic storage capacitor, with high ESR and low reliability, whose function is to create a constant DC bus. Unlike typical single-stage converters, filtering the fluctuating instantaneous power in the primary-side of the converter brings advantages such as reducing the RMS current in the secondary-side of the circuit, which results on a 50${\%}$ of savings in the secondary-side resistive conduction losses. This is considered a key point, specially in Electric Vehicle (EV) wireless battery charging applications, facilitating the refrigeration of secondary-side circuit that is located on-board the vehicle. The article presents the novel FCI-DAB circuit and proposes a control strategy based on duty-cycle modulation which enables the realization of the PFC in the grid-side and the compensation of the power fluctuation with the active buffer in the primary-side. The FCI-DAB concept is verified by experimental results, obtained from an GaN-based IPT 1.5 kW battery charger, with 93% of efficiency and PF = 0.99.

Keywords

• Active filter
• power pulsation buffer
• PFC
• floating capacitor
• FCI-DAB
• single-phase