Bidirectional Control With Fitting Model-Based Synchronous Rectification and Input Ripple Current Feedforward for SiC Bidirectional CLLC EV Charger
Haoran Li, Yibo Sun, Shengdong Wang, Zhiliang Zhang, Xiaoyong Ren, Pinjia Zhang, Guozhi Yang, Cungang Hu
Abstract
Conventional CLLC synchronous rectification (SR) typically adopts detection circuits to sense the high frequency signals. It can hardly be used in the high-voltage SiC applications directly as it is sensitive to high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> and may cause false operation. A bidirectional control is proposed for the SiC CLLC charger to achieve the SR function and mitigate the input ripple current. Considering the switching frequency and load, the SR on-time is calculated by the proposed three-order fitting model with low calculation source and high immunity to high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> . Moreover, an input ripple current feedforward control is proposed in the discharging mode, which adds the extracted double line-frequency ripple current to the bus voltage reference. It not only achieves low SR conduction loss, but also reduces the input ripple current largely in the discharge. A 6.6-kW SiC bidirectional CLLC charger was built. Compared to the conventional SR, the CLLC efficiency of proposed SR improves 0.28% at 6.6 kW in the charge. In the discharge, the reduction of CLLC input ripple current at the double line-frequency is up to 91%. The overall charging and discharging efficiencies are 95.4% and 96.1% at full load, respectively.