An Efficient and Compact Single-Stage High-Frequency-Link Medium Voltage AC to DC Converter

High frequency (HF) link medium voltage AC (MVAC) to low voltage DC (LVDC) converters are attractive as they do not use expensive and heavy line frequency transformers. They find a wide range of essential applications, including solid-state transformers, grid integration of renewables storage, fast charging of electric vehicles, etc. This paper presents a new topology and modulation strategy for HF link MVAC to LVDC converter that supports bi-directional power flow at any power factor at high power quality. It achieves high efficiency due to the low frequency and soft-switching of power devices. The proposed solution uses multi-level architecture in each cascaded module and a quad-active bridge configuration to combine DC-side bridges in all three phases resulting in a significant reduction in the number of devices. The single-stage architecture avoids the electrolytic DC link capacitor present in each module of the conventional multi-stage solution that experiences a second harmonic ripple and improves reliability and power density. The proposed solution is verified through simulation and experiment.