Optimizing voltage management and transformer design in MV networks with high distributed energy resource penetration

(MV) distribution networks has fundamentally altered traditional voltage regulation and frequency control paradigms. As synchronous generators are displaced by inverter-based resources (IBRs), system strength, inertia, and voltage stiffness are significantly reduced, creating new operational challenges. This paper investigates the role of grid-forming (GFM) inverters in optimizing voltage management in MV networks under high DER penetration, with particular emphasis on the Virtual Synchronous Generator (VSG) control approach. Using detailed electromagnetic transient simulations implemented in RSCAD, the VSG-based gridforming inverter is evaluated under grid-connected operation, islanded operation, black-start conditions, fault ride-through events, inertia emulation tests, and varying short-circuit ratios

(SCRs). The results from a model by [1] demonstrates that VSG-controlled grid-forming inverters can effectively regulate voltage magnitude, support active and reactive power sharing, provide tunable synthetic inertia, and maintain stable operation in both weak and stiff MV grids when appropriately parameterized. The findings from simulations and multiple literature confirms that VSG-based grid-forming control represents a critical enabler for resilient MV distribution networks with high DER penetration and provides practical insights for network planning and operational studies.