Very Accurate Output Voltage Estimation on Primary-side for LLC Resonant Solid-State-Transformer (SST)

Abstract

Bulky traditional transformer can be replaced with solid-state-transformer (SST) thanks to fast-switching power semiconductors, such as silicon carbide FET and diode. SST implemented using LLC resonant converter can improve power efficiency and minimize its highfrequency transformer. However, high isolation voltage between primary and secondary sides makes output voltage sensing much more difficult. Even though output can be monitored on secondary side, it must be also estimated for fast protection on primary side. In this paper, very accurate estimation scheme for output voltage on primary side is proposed and verified by simulation.