Modeling and four-loop master-slave control of a six-phase interleaved buck converter for ultrafast EV charging

Abstract

In this paper, modeling and control of a six-phase interleaved buck converter (IBC) are presented for fast charging of ultra-fast electric vehicle (EV) batteries. The primary difficulty faced is the need to operate at high power charging rates with stable and efficient performance, while minimizing output ripple and current sharing errors. To solve these problems, the cascaded multi-loop control method is proposed using a proportional-integral (PI) controller. By implementing a reduced number of control loops (four coordinated loops) from conventional configurations, the control structure is simplified, while stable operation and effective current sharing are maintained. The proposed system is implemented in a constant current/constant voltage (CC-CV) charging method, which guarantees safe and efficient battery charging. The proposed system is validated by using MATLAB/Simulink simulation under steady-state and transient conditions. The results show that with a very small amount of ripple, a battery voltage of about 820 V and a charging current of 330 A are obtained. The dynamic response has a settling time of about 100 ms and an overshoot less than 5%, which is suitable for disturbances. Furthermore, in the SIMO configuration, it is noted that a disturbance or fault on the output of one of the cascaded control loops has minimal effect on the output of the other control loop, which illustrates good decoupling between cascaded control loops. This is a sign of better robustness and reliability for multi-output EV charging applications. Moreover, the stability margins of the proposed control method are verified by frequency-domain analysis.