Circulating Active Power Flow and DC-Link Voltage Ripple in Hybrid Transformers

Hybrid Distribution Transformers (HDTs) are a promising solution to power quality problems on distribution networks, allowing for precise voltage and current regulation. HDTs that connect the series converter on the primary side are subject to a Circulating Active Power Flow (CAPF) between the Low-Frequency Transformer (LFT) and the power converters that appear when compensating for voltage disturbances. This paper analyzes the cause of the CAPF and its behavior, considering varying grid conditions and the impact of the CAPF on the DC-Link ripple.