Beat Frequency Modulated Twice-Line-Frequency Active Energy Buffer

Traditionally, electrolytic capacitors serve as twice-line-frequency energy buffers in high power factor single-phase ac-dc and dc-ac converters, often limiting the converter's size and lifespan. Numerous active energy buffers enabling the usage of longer life film or ceramic capacitors have been proposed in literature as alternative solutions. This work presents a novel active energy buffering solution using the newly proposed beat frequency modulation (BFM) control strategy, offering reduced circuit and control complexity. In the proposed architecture, a full bridge inverter with series LC resonant tank at its output is connected across the dc bus. Utilizing BFM on the full bridge inverter generates the necessary ripple power to mitigate the instantaneous power differences between dc and ac ports. The circuit operation and the energy buffer design are discussed in detail. Through appropriate design of the active energy buffer, it is shown both in simulations and experiments that effective ripple power cancellation can be achieved on the dc port, thereby validating the proposed architecture.