S-Shaped-Based Power Sharing Control of DC-Coupled EV Charging Station

This work proposes an S-shaped power-sharing control (S-PSC) for enhancing scalability of the DC-coupled electric vehicle (EV) charging stations. The scheme provides DC-link voltage regulation while coordinating the charging activities of multiple EVs and integrating battery energy storage systems (BESSs), supercapacitors, renewable energy sources, and a bidirectional voltage source inverter (B-VSI). While existing inertial droop-based control strategies require measurements of the DC-source output power to tune their response according to the assigned inertia, the proposed S-PSC relies solely on DC-link voltage measurements to decouple the DC power demand into multiple inertia-response levels. The S-shaped function prioritizes the compensation of these response levels by dynamically coordinating the operation of the B-VSI, BESS, and EV storage units, ensuring acceptable state of charge, adequate inertia support, and operation close to nominal power levels. A small-signal analysis confirms voltage stability and attenuation of the BESS current. Experimental validation using hardware-in-the-loop under 60 minutes of intensive EV charging during peak hour demonstrated that the S-PSC reduces BESS stress by 40%, increases energy delivery to EVs by 32%, enhances the economic benefit of BESS utilization, and mitigates flicker in the low-voltage grid when compared with the conventional benchmark solution for industrial applications.