GridFormer – A New Approach to Stabilize and Manage a High IBR Penetration Grid

In this paper, a grid-enhancing technology to stabilize and manage the future high inverter-based-resource (IBR) penetration grid — the GridFormer — is presented. The Grid-Former builds on hybrid transformer technologies, and as such, is designed to attach to passive three-phase or three single-phase transformers with rated power from dozens of kVA to hundreds of MVA. Herein, a containerized structure with commercially available fractionally-rated solutions, consisting of two back-to-back voltage-source-converters (VSCs) (two, three, or multilevel) and an auxiliary transformer are connected between the low-voltage winding of the main transformer and neutral. The proposed configuration utilizes series and shunt voltage/current injection to achieve steady-state power flow control. Moreover, the dc-link of the GridFormer features an energy storage source (e.g., ultracapacitor or battery pack) to enable the active series/shunt damping of grid oscillations, and grid-forming functionality (including inertia support and grid stability enhancements). This functionality is the basis for the novelty of this work, and its implementation may hold the key to allowing the stable operation of the future grid. Lastly, the GridFormer is equipped with a ‘fail-normal-switch’ or FNS, capable of bypassing the series power converter and allowing the main transformer to ride any fault in the system. MATLAB Simulink and OPAL-RT hardware-in-loop (HIL) simulations validate the supporting capability of the GridFormer for load-transient and power oscillation damping.