Utility-Based Grid Forming Inverters Applications: Seamless Transition and Power Oscillation Damping

Utility-based Grid Forming Inverters (GFMs) are gaining immense popularity as penetration of inverter-based resources (IBRs) are reaching all-time high levels. One of the main advantages of these inverters is their ability to operate in both grid-connected and islanded modes of operation. GFMs need to have a smooth transition between the different modes of operation to maintain synchronism during the transition and establish a stiff voltage source when in islanded or locked frequency mode. This paper presents a synchronization control technique based on smoothing the change in angle when the GFM transitions between modes of operation. Furthermore, a Power Oscillation Damper (POD) was designed as an auxiliary control of the GFM to damp electromechanical oscillations when operating in grid-connected mode. The proposed GFM model is interconnected to the modified IEEE 12-bus system, and simulation results demonstrate the effectiveness of the proposed control.