HIL Testbed-Based Design and Implementation of DER-Integrated-MMC for Extreme Fast Charger

The limited availability of affordable and rapid charging infrastructure slows the adoption of electric vehicles (EVs). The modular multilevel converter (MMC) based approach can provide a viable solution for future extreme-fast charging (XFC) infrastructure. Additionally, distributed energy resources (DER) can be integrated to minimize grid dependency and increase availability and reliability. We propose a DER-integrated-MMC for extreme fast charger (MMC-DER-XFC) that incorporates a dual-active bridge (DAB) for EV charging and DER within the sub-module (SM). While some researchers have explored related studies, the absence of access to the SM capacitor terminals limits the integration with DAB and DER. To address this challenge, this paper proposes an innovative and optimal design of MMC-DER-XFC and implements and validates it using an OpalRT real-time simulator-based HIL testbed. This model can act as a testbed for various studies and control developments. This paper simulates a testbed with 60 EVs and DERs, but it can support up to 300 EVs and DERs. Additionally, any number of EVs and DERs can be activated or deactivated for a specified duration. Furthermore, distinct EV charging/discharging and DER generation profiles can be independently defined for each unit. The developed testbed has been evaluated using a standard MMC controller. This paper examines the internal dynamics of the MMC-DER-XFC under different scenarios: (1) only DERs are operational, (2) only EVs are functioning in either grid-to-vehicle (G2V) or vehicle-to-grid (V2G) mode, and (3) both DERs and EVs (G2V and V2G) are active. The testbed demonstrates harmonic distortion at low power levels, but these distortions are eliminated under full load conditions.