Modified Phase shift Control for DAB Based Bidirectional Onboard EV Charger

Abstract

This paper proposes a modified phase shift control algorithm with variable duty cycle for electric vehicle (EV) on-board bi-directional charging scheme with level-l charger. The EV charger interacts with the distribution grid to exchange the required amount of active and reactive power demand from either side by the purposed control methodology. An isolated DC-DC converter topology is implemented to ensure the bidirectional charging process of the electric vehicle (EV) battery stack with an increased efficiency. The proposed control topology for double stage AC-DC converter is explained with mathematical model through state averaging technique to analyze the converter steady state voltage and current dynamics. The interdependency of phase shift ratio and power transfer limit is described through state space model to illustrate the bi-directional active power flow while maintaining unity power factor at utility. The direct power control algorithm with a cost optimizing function is implemented to generate the switching pulses for the front-end converter that provides accurate control over complex PI controller gain tuning technique. Dual active bridge with a high frequency isolating transformer is designed to carry out the bi-directional power flow with the EV battery. A MATLAB & Simulink model is developed to validate the proposed control topology for a 3.5 kW bi-directional EV charger.