A Novel Integrated Bidirectional AC to DC Resonant Converter

Conventionally, an AC to DC isolated converter follows a two-stage design approach, wherein the first stage is an AC to DC power factor correction (PFC) stage followed by a resonant converter stage for DC voltage regulation. In existing topologies, the PFC stage and the primary side resonant switch network are merged into a single switch network giving rise to 25% fewer devices. Moreover, the switches in these topologies are soft switched that facilitates high switching frequency. Hence, low volume magnetic components and capacitors can be used to achieve higher power density. However, it is an unipolar voltage-fed resonant topology and also, the power transfer is unidirectional, restricting the power flow only from AC to DC side. This paper proposes a novel isolated bidirectional bipolar voltage-fed AC to DC converter which has all the aforementioned advantages. In addition, it addresses their shortcomings by generating a bipolar voltage across the resonant tanks and realizing bidirectional power flow. A modulation and control technique is proposed for generating switching pulses for DC link voltage control and bidirectional power transfer. These are demonstrated through simulations and experiments, where 1.35 kW power is transferred at 130 kHz switching frequency, 150V (L-L) AC input voltage and 200V output DC voltage.