A Novel Limited Grid-Forming Strategy to Support Power System Stability under Primary Energy Source Limitations

Abstract

The available literature on grid-forming converters often assumes an unlimited primary energy source, for example by postulating a constant DC voltage source. However, this assumption is not justified in real-world scenarios as soon as primary energy source limitations are reached. Therefore, it is imperative for grid-forming control strategies to take such limitations into account and ensure that they support robust system stability even under primary source limitations. In this work, a novel concept of limited grid-forming control is introduced that supports the stability of the network, even under primary energy source power as well as energy constraints. Moreover, the control concept also allows for a seamless transition between full grid-forming and limited grid-forming behavior without any control mode switching. The proposed scheme is tested on a modified IEEE 9-bus test system with one synchronous machine replaced by a droop-based grid-forming controlled battery system incorporating the proposed control scheme. The simulation of a couple of dynamic events provides results that demonstrate promising performance, thereby substantiating the feasibility of the proposed control scheme.